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Sample records for finite strain elasticity

  1. Finite strain crack tip fields in soft incompressible elastic solids.

    PubMed

    Krishnan, Venkat R; Hui, Chung Yuen; Long, Rong

    2008-12-16

    A finite element model (FEM) is used to study the behavior of the large deformation field near the tip of a crack in a soft incompressible plane stress fracture specimen loaded in mode I. Results are obtained for the case of a neo-Hookean solid (ideal rubber) and a hyperelastic solid with exponentially hardening behavior. In contrast to the predictions of linear elastic fracture mechanics (LEFM), the near tip stress fields are dominated by the opening stress which shows a 1/R singularity for the neo-Hookean material and a -1/(R ln R) singularity for the exponential hardening solid. We found very similar qualitative behavior in the near tip stress fields despite the very large difference in strain hardening behavior of the two material models. Our result shows that the near tip opening stress is controlled by the far field energy release rate for large applied loads. PMID:19053624

  2. Finite-strain large-deflection elastic-viscoplastic finite-element transient response analysis of structures

    NASA Technical Reports Server (NTRS)

    Rodal, J. J. A.; Witmer, E. A.

    1979-01-01

    A method of analysis for thin structures that incorporates finite strain, elastic-plastic, strain hardening, time dependent material behavior implemented with respect to a fixed configuration and is consistently valid for finite strains and finite rotations is developed. The theory is formulated systematically in a body fixed system of convected coordinates with materially embedded vectors that deform in common with continuum. Tensors are considered as linear vector functions and use is made of the dyadic representation. The kinematics of a deformable continuum is treated in detail, carefully defining precisely all quantities necessary for the analysis. The finite strain theory developed gives much better predictions and agreement with experiment than does the traditional small strain theory, and at practically no additional cost. This represents a very significant advance in the capability for the reliable prediction of nonlinear transient structural responses, including the reliable prediction of strains large enough to produce ductile metal rupture.

  3. Explicit mixed strain-displacement finite elements for compressible and quasi-incompressible elasticity and plasticity

    NASA Astrophysics Data System (ADS)

    Cervera, M.; Lafontaine, N.; Rossi, R.; Chiumenti, M.

    2016-06-01

    This paper presents an explicit mixed finite element formulation to address compressible and quasi-incompressible problems in elasticity and plasticity. This implies that the numerical solution only involves diagonal systems of equations. The formulation uses independent and equal interpolation of displacements and strains, stabilized by variational subscales. A displacement sub-scale is introduced in order to stabilize the mean-stress field. Compared to the standard irreducible formulation, the proposed mixed formulation yields improved strain and stress fields. The paper investigates the effect of this enhancement on the accuracy in problems involving strain softening and localization leading to failure, using low order finite elements with linear continuous strain and displacement fields (P1P1 triangles in 2D and tetrahedra in 3D) in conjunction with associative frictional Mohr-Coulomb and Drucker-Prager plastic models. The performance of the strain/displacement formulation under compressible and nearly incompressible deformation patterns is assessed and compared to analytical solutions for plane stress and plane strain situations. Benchmark numerical examples show the capacity of the mixed formulation to predict correctly failure mechanisms with localized patterns of strain, virtually free from any dependence of the mesh directional bias. No auxiliary crack tracking technique is necessary.

  4. Explicit mixed strain-displacement finite elements for compressible and quasi-incompressible elasticity and plasticity

    NASA Astrophysics Data System (ADS)

    Cervera, M.; Lafontaine, N.; Rossi, R.; Chiumenti, M.

    2016-09-01

    This paper presents an explicit mixed finite element formulation to address compressible and quasi-incompressible problems in elasticity and plasticity. This implies that the numerical solution only involves diagonal systems of equations. The formulation uses independent and equal interpolation of displacements and strains, stabilized by variational subscales. A displacement sub-scale is introduced in order to stabilize the mean-stress field. Compared to the standard irreducible formulation, the proposed mixed formulation yields improved strain and stress fields. The paper investigates the effect of this enhancement on the accuracy in problems involving strain softening and localization leading to failure, using low order finite elements with linear continuous strain and displacement fields ( P1 P1 triangles in 2D and tetrahedra in 3D) in conjunction with associative frictional Mohr-Coulomb and Drucker-Prager plastic models. The performance of the strain/displacement formulation under compressible and nearly incompressible deformation patterns is assessed and compared to analytical solutions for plane stress and plane strain situations. Benchmark numerical examples show the capacity of the mixed formulation to predict correctly failure mechanisms with localized patterns of strain, virtually free from any dependence of the mesh directional bias. No auxiliary crack tracking technique is necessary.

  5. Homogenized mechanical properties of auxetic composite materials in finite-strain elasticity

    NASA Astrophysics Data System (ADS)

    Kochmann, Dennis M.; Venturini, Gabriela N.

    2013-08-01

    Careful microstructural design can result in materials with counterintuitive effective (macroscale) mechanical properties such as a negative Poisson’s ratio, commonly referred to as auxetic behavior. One specific approach to achieving auxetic behavior is to elastically connect structural elements with rotational degrees of freedom to result in elastic structures that unfold under uniaxial loading in specific directions, thereby giving rise to bi- or triaxial expansion, i.e. auxetic behavior (transverse expansion under uniaxial extension). This concept has been applied successfully to elastically coupled two-dimensional rigid rotational elements (such as rotating rectangles and triangles) which exhibit a negative effective in-plane Poisson’s ratio under uniaxial (ex)tension. Here, we adopt this fundamental design principle but take it to the next level by achieving auxetic behavior in finitely strained composites made of stiff inclusions in a hyperelastic matrix, and we study the resulting elastic properties under in-plane strain by numerical homogenization. Our results highlight the emergence of auxetic behavior based on geometric arrangement and properties of the base material and demonstrate a path towards simple inclusion-matrix composites with auxetic behavior.

  6. A staggered approach for the coupling of Cahn-Hilliard type diffusion and finite strain elasticity

    NASA Astrophysics Data System (ADS)

    Areias, P.; Samaniego, E.; Rabczuk, T.

    2016-02-01

    We develop an algorithm and computational implementation for simulation of problems that combine Cahn-Hilliard type diffusion with finite strain elasticity. We have in mind applications such as the electro-chemo-mechanics of lithium ion (Li-ion) batteries. We concentrate on basic computational aspects. A staggered algorithm is proposed for the coupled multi-field model. For the diffusion problem, the fourth order differential equation is replaced by a system of second order equations to deal with the issue of the regularity required for the approximation spaces. Low order finite elements are used for discretization in space of the involved fields (displacement, concentration, nonlocal concentration). Three (both 2D and 3D) extensively worked numerical examples show the capabilities of our approach for the representation of (i) phase separation, (ii) the effect of concentration in deformation and stress, (iii) the effect of strain in concentration, and (iv) lithiation. We analyze convergence with respect to spatial and time discretization and found that very good results are achievable using both a staggered scheme and approximated strain interpolation.

  7. Elastic strain reduction of finite germanium(x) silicon(1-x)/silicon structures

    NASA Astrophysics Data System (ADS)

    U'Ren, Gregory David

    The focus of this dissertation is a rigorous examination the elastic, intrinsic behavior of stress/strain for epitaxial Si1-xGe x/Si (100) structures having finite dimensions. Existing models predict that the behavior is governed primarily by geometry, which can have a profound effect should the ratio of half-width to height (l/h) be less than 50. Two main aspects of existing theories were pressed: first, the role of geometry for a fixed Si1-xGex composition and therefore strain (epsilon = 0.42%) and second, the role of misfit stress for a fixed l/b ratio of 0.5. Strict control of the fabrication process necessitated selective epitaxial growth via gas-source molecular beam epitaxy. Though experimental combinations of various thickness (50, 100, 140, and 200 nm) and variable pitch (0.09-25 mum) a wide range of l/b values was obtained (0.5-500). As the selectively grown structures are arranged into a periodic array, where the period is repeated over a large distance (mm), in addition to dynamical diffraction, Fraunhoffer diffraction was also observed. These two complementary mechanisms of diffraction were used to determine the stress distribution within these structures. Ensemble with transmission electron microscopy, a qualitative assessment of elastic strain reduction mechanisms--local curvature effects and tangential forces--was possible. The main conclusions of this dissertation are as follows: (A) An analytical reciprocal space construction was developed to facilitate the interpretation of experimental x-ray diffraction data. (B) As a corollary, arbitrary positioning and movement in reciprocal space are described, which in practice is applied to capturing scattered intensity parallel to the surface. (C) Facet growth in SiGe selective epitaxy was investigated. One key result is the persistence of a {113} facet with increasing thickness, as the {111} facet is anticipated. (D) In examining the role of geometry, elastic lattice distortions were only observed for l

  8. On constitutive relations at finite strain - Hypo-elasticity and elasto-plasticity with isotropic or kinematic hardening

    NASA Technical Reports Server (NTRS)

    Atluri, S. N.

    1984-01-01

    Nagtegaal and de Jong (1982) have studied stresses generated by simple finite shear in the case of elastic-plastic and rigid-plastic materials which exhibit anisotropic hardening. They reported that the shear stress is oscillatory in time. It was found that the occurrence of such an 'anomaly' is not restricted to anisotropic plasticity. Similar behavior in finite shear may result even in the case of hypoelasticity and classical isotropic hardening plasticity theory. The present investigation is concerned with the central problem of 'generalizing' with respect to the finite strain case, taking into account the constitutive relations of infinitesimal strain theories of classical plasticity with isotropic or kinematic hardening. The problem of hypoelasticity is also considered. It is shown that current controversies surrounding the choice of stress rate in the finite-strain generalizations of the constitutive relations and the anomalies surrounding kinematic hardening plasticity theory are easily resolvable.

  9. Beyond linear elasticity: jammed solids at finite shear strain and rate.

    PubMed

    Boschan, Julia; Vågberg, Daniel; Somfai, Ellák; Tighe, Brian P

    2016-06-28

    The shear response of soft solids can be modeled with linear elasticity, provided the forcing is slow and weak. Both of these approximations must break down when the material loses rigidity, such as in foams and emulsions at their (un)jamming point - suggesting that the window of linear elastic response near jamming is exceedingly narrow. Yet precisely when and how this breakdown occurs remains unclear. To answer these questions, we perform computer simulations of stress relaxation and shear start-up tests in athermal soft sphere packings, the canonical model for jamming. By systematically varying the strain amplitude, strain rate, distance to jamming, and system size, we identify characteristic strain and time scales that quantify how and when the window of linear elasticity closes, and relate these scales to changes in the microscopic contact network. PMID:27212139

  10. Local strain redistribution corrections for a simplified inelastic analysis procedure based on an elastic finite-element analysis

    NASA Technical Reports Server (NTRS)

    Kaufman, A.; Hwang, S. Y.

    1985-01-01

    Strain redistribution corrections were developed for a simplified inelastic analysis procedure to economically calculate material cyclic response at the critical location of a structure for life prediction proposes. The method was based on the assumption that the plastic region in the structure is local and the total strain history required for input can be defined from elastic finite-element analyses. Cyclic stress-strain behavior was represented by a bilinear kinematic hardening model. The simplified procedure predicts stress-strain response with reasonable accuracy for thermally cycled problems but needs improvement for mechanically load-cycled problems. Neuber-type corrections were derived and incorporated in the simplified procedure to account for local total strain redistribution under cyclic mechanical loading. The corrected simplified method was used on a mechanically load-cycled benchmark notched-plate problem. The predicted material response agrees well with the nonlinear finite-element solutions for the problem. The simplified analysis computer program was 0.3% of the central processor unit time required for a nonlinear finite-element analysis.

  11. A three dimensional field formulation, and isogeometric solutions to point and line defects using Toupin's theory of gradient elasticity at finite strains

    NASA Astrophysics Data System (ADS)

    Wang, Z.; Rudraraju, S.; Garikipati, K.

    2016-09-01

    We present a field formulation for defects that draws from the classical representation of the cores as force dipoles. We write these dipoles as singular distributions. Exploiting the key insight that the variational setting is the only appropriate one for the theory of distributions, we arrive at universally applicable weak forms for defects in nonlinear elasticity. Remarkably, the standard, Galerkin finite element method yields numerical solutions for the elastic fields of defects that, when parameterized suitably, match very well with classical, linearized elasticity solutions. The true potential of our approach, however, lies in its easy extension to generate solutions to elastic fields of defects in the regime of nonlinear elasticity, and even more notably for Toupin's theory of gradient elasticity at finite strains (Toupin Arch. Ration. Mech. Anal., 11 (1962) 385). In computing these solutions we adopt recent numerical work on an isogeometric analytic framework that enabled the first three-dimensional solutions to general boundary value problems of Toupin's theory (Rudraraju et al. Comput. Methods Appl. Mech. Eng., 278 (2014) 705). We first present exhaustive solutions to point defects, edge and screw dislocations, and a study on the energetics of interacting dislocations. Then, to demonstrate the generality and potential of our treatment, we apply it to other complex dislocation configurations, including loops and low-angle grain boundaries.

  12. A model for a constrained, finitely deforming, elastic solid with rotation gradient dependent strain energy, and its specialization to von Kármán plates and beams

    NASA Astrophysics Data System (ADS)

    Srinivasa, A. R.; Reddy, J. N.

    2013-03-01

    The aim of this paper is to develop the governing equations for a fully constrained finitely deforming hyperelastic Cosserat continuum where the directors are constrained to rotate with the body rotation. This is the generalization of small deformation couple stress theories and would be useful for developing mathematical models for an elastic material with embedded stiff short fibers or inclusions (e.g., materials with carbon nanotubes or nematic elastomers, cellular materials with oriented hard phases, open cell foams, and other similar materials), that account for certain longer range interactions. The theory is developed as a limiting case of a regular Cosserat elastic material where the directors are allowed to rotate freely by considering the case of a high "rotational mismatch energy". The theory is developed using the formalism of Lagrangian mechanics, with the static case being based on Castigliano's first theorem. By considering the stretch U and the rotation R as additional independent variables and using the polar decomposition theorem as an additional constraint equation, we obtain the governing and as well as the boundary conditions for finite deformations. The resulting equations are further specialized for plane strain and axisymmetric finite deformations, deformations of beams and plates with small strain and moderate rotation, and for small deformation theories. We also show that the boundary conditions for this theory involve "surface tension" like terms due to the higher gradients in the strain energy function. For beams and plates, the rotational gradient dependent strain energy does not require additional variables (unlike Cosserat theories) and additional differential equations; nor do they raise the order of the differential equations, thus allowing us to include a material length scale dependent response at no extra "computational cost" even for finite deformation beam/plate theories

  13. Finite Element Analysis of 2-D Elastic Contacts Involving FGMs

    NASA Astrophysics Data System (ADS)

    Abhilash, M. N.; Murthy, H.

    2014-05-01

    The response of elastic indenters in contact with Functionally Graded Material (FGM) coated homogeneous elastic half space has been presented in the current paper. Finite element analysis has been used due to its ability to handle complex geometry, material, and boundary conditions. Indenters of different typical surface profiles have been considered and the problem has been idealized as a two-dimensional (2D) plane strain problem considering only normal loads. Initially, indenters were considered to be rigid and the results were validated with the solutions presented in the literature. The analysis has then been extended to the case of elastic indenters on FGM-coated half spaces and the results are discussed.

  14. Asymmetric quadrilateral shell elements for finite strains

    NASA Astrophysics Data System (ADS)

    Areias, P.; Dias-da-Costa, D.; Pires, E. B.; Van Goethem, N.

    2013-07-01

    Very good results in infinitesimal and finite strain analysis of shells are achieved by combining either the enhanced-metric technique or the selective-reduced integration for the in-plane shear energy and an assumed natural strain technique (ANS) in a non-symmetric Petrov-Galerkin arrangement which complies with the patch-test. A recovery of the original Wilson incompatible mode element is shown for the trial functions in the in-plane components. As a beneficial side-effect, Newton-Raphson convergence behavior for non-linear problems is improved with respect to symmetric formulations. Transverse-shear and in-plane patch tests are satisfied while distorted-mesh accuracy is higher than with symmetric formulations. Classical test functions with assumed-metric components are required for compatibility reasons. Verification tests are performed with advantageous comparisons being observed in all of them. Applications to large displacement elasticity and finite strain plasticity are shown with both low sensitivity to mesh distortion and (relatively) high accuracy. A equilibrium-consistent (and consistently linearized) updated-Lagrangian algorithm is proposed and tested. Concerning the time-step dependency, it was found that the consistent updated-Lagrangian algorithm is nearly time-step independent and can replace the multiplicative plasticity approach if only moderate elastic strains are present, as is the case of most metals.

  15. Cyclic creep analysis from elastic finite-element solutions

    NASA Technical Reports Server (NTRS)

    Kaufman, A.; Hwang, S. Y.

    1986-01-01

    A uniaxial approach was developed for calculating cyclic creep and stress relaxation at the critical location of a structure subjected to cyclic thermomechanical loading. This approach was incorporated into a simplified analytical procedure for predicting the stress-strain history at a crack initiation site for life prediction purposes. An elastic finite-element solution for the problem was used as input for the simplified procedure. The creep analysis includes a self-adaptive time incrementing scheme. Cumulative creep is the sum of the initial creep, the recovery from the stress relaxation and the incremental creep. The simplified analysis was exercised for four cases involving a benchmark notched plate problem. Comparisons were made with elastic-plastic-creep solutions for these cases using the MARC nonlinear finite-element computer code.

  16. Finite strain discrete dislocation plasticity in a total Lagrangian setting

    NASA Astrophysics Data System (ADS)

    Irani, N.; Remmers, J. J. C.; Deshpande, V. S.

    2015-10-01

    We present two total Lagrangian formulations for finite strain discrete dislocation plasticity wherein the discrete dislocations are presumed to be adequately represented by singular linear elastic fields thereby extending the superposition method of Van der Giessen and Needleman (1995) to finite strains. The finite deformation effects accounted for are (i) finite lattice rotations and (ii) shape changes due to slip. The two formulations presented differ in the fact that in the "smeared-slip" formulation the discontinuous displacement field is smeared using finite element shape functions while in the "discrete-slip" formulation the weak form of the equilibrium statement is written to account for the slip displacement discontinuity. Both these total Lagrangian formulations use a hyper-elastic constitutive model for lattice elasticity. This overcomes the issues of using singular dislocation fields in a hypo-elastic constitutive relation as encountered in the updated Lagrangian formulation of Deshpande et al. (2003). Predictions of these formulations are presented for the relatively simple problems of tension and compression of single crystals oriented for single slip. These results show that unlike in small-strain discrete dislocation plasticity, finite strain effects result in a size dependent tension/compression asymmetry. Moreover, both formulations give nearly identical predictions and thus we expect that the "smeared-slip" formulation is likely to be preferred due to its relative computational efficiency and simplicity.

  17. Thermodynamic stability in elastic systems: Hard spheres embedded in a finite spherical elastic solid.

    PubMed

    Solano-Altamirano, J M; Goldman, Saul

    2015-12-01

    We determined the total system elastic Helmholtz free energy, under the constraints of constant temperature and volume, for systems comprised of one or more perfectly bonded hard spherical inclusions (i.e. "hard spheres") embedded in a finite spherical elastic solid. Dirichlet boundary conditions were applied both at the surface(s) of the hard spheres, and at the outer surface of the elastic solid. The boundary conditions at the surface of the spheres were used to describe the rigid displacements of the spheres, relative to their initial location(s) in the unstressed initial state. These displacements, together with the initial positions, provided the final shape of the strained elastic solid. The boundary conditions at the outer surface of the elastic medium were used to ensure constancy of the system volume. We determined the strain and stress tensors numerically, using a method that combines the Neuber-Papkovich spherical harmonic decomposition, the Schwartz alternating method, and Least-squares for determining the spherical harmonic expansion coefficients. The total system elastic Helmholtz free energy was determined by numerically integrating the elastic Helmholtz free energy density over the volume of the elastic solid, either by a quadrature, or a Monte Carlo method, or both. Depending on the initial position of the hard sphere(s) (or equivalently, the shape of the un-deformed stress-free elastic solid), and the displacements, either stationary or non-stationary Helmholtz free energy minima were found. The non-stationary minima, which involved the hard spheres nearly in contact with one another, corresponded to lower Helmholtz free energies, than did the stationary minima, for which the hard spheres were further away from one another. PMID:26701708

  18. Finite-element formulations for problems of large elastic-plastic deformation

    NASA Technical Reports Server (NTRS)

    Mcmeeking, R. M.; Rice, J. R.

    1975-01-01

    An Eulerian finite element formulation is presented for problems of large elastic-plastic flow. The method is based on Hill's variational principle for incremental deformations, and is ideally suited to isotropically hardening Prandtl-Reuss materials. Further, the formulation is given in a manner which allows any conventional finite element program, for 'small strain' elastic-plastic analysis, to be simply and rigorously adapted to problems involving arbitrary amounts of deformation and arbitrary levels of stress in comparison to plastic deformation moduli. The method is applied to a necking bifurcation analysis of a bar in plane-strain tension. The paper closes with a unified general formulation of finite element equations, both Lagrangian and Eulerian, for large deformations, with arbitrary choice of the conjugate stress and strain measures. Further, a discussion is given of other proposed formulations for elastic-plastic finite element analysis at large strain, and the inadequacies of some of these are commented upon.

  19. Elastic-plastic finite-element analyses of thermally cycled single-edge wedge specimens

    NASA Technical Reports Server (NTRS)

    Kaufman, A.

    1982-01-01

    Elastic-plastic stress-strain analyses were performed for single-edge wedge alloys subjected to thermal cycling in fluidized beds. Three cases (NASA TAZ-8A alloy under one cycling condition and 316 stainless steel alloy under two cycling conditions) were analyzed by using the MARC nonlinear, finite-element computer program. Elastic solutions from MARC showed good agreement with previously reported solutions that used the NASTRAN and ISO3DQ computer programs. The NASA TAZ-8A case exhibited no plastic strains, and the elastic and elastic-plastic analyses gave identical results. Elastic-plastic analyses of the 316 stainless steel alloy showed plastic strain reversal with a shift of the mean stresses in the compressive direction. The maximum equivalent total strain ranges for these cases were 13 to 22 percent greater than that calculated from elastic analyses.

  20. Elastic-plastic finite-element analyses of thermally cycled double-edge wedge specimens

    NASA Technical Reports Server (NTRS)

    Kaufman, A.; Hunt, L. E.

    1982-01-01

    Elastic-plastic stress-strain analyses were performed for double-edge wedge specimens subjected to thermal cycling in fluidized beds at 316 and 1088 C. Four cases involving different nickel-base alloys (IN 100, Mar M-200, NASA TAZ-8A, and Rene 80) were analyzed by using the MARC nonlinear, finite element computer program. Elastic solutions from MARC showed good agreement with previously reported solutions obtained by using the NASTRAN and ISO3DQ computer programs. Equivalent total strain ranges at the critical locations calculated by elastic analyses agreed within 3 percent with those calculated from elastic-plastic analyses. The elastic analyses always resulted in compressive mean stresses at the critical locations. However, elastic-plastic analyses showed tensile mean stresses for two of the four alloys and an increase in the compressive mean stress for the highest plastic strain case.

  1. Finite element formulations for problems of large elastic-plastic deformation

    NASA Technical Reports Server (NTRS)

    Mcmeeking, R. M.; Rice, J. R.

    1974-01-01

    An Eulerian finite element formulation is presented for problems of large elastic-plastic flow. The method is based on Hill's variational principle for incremental deformations, and is suited to isotropically hardening Prandtl-Reuss materials. The formulation is given in a manner which allows any conventional finite element program, for "small strain" elasticplastic analysis, to be simply and rigorously adapted to problems involving arbitrary amounts of deformation and arbitrary levels of stress in comparison to plastic deformation moduli. The method is applied to a necking bifurcation analysis of a bar in plane-strain tension. A unified general formulation of finite element equations, both Lagrangian and Eulerian, for large deformations, with arbitrary choice of the conjugate stress and strain measures, and a discussion is given of other proposed formulations for elastic-plastic finite element analysis at large strain.

  2. Finite Element Prediction of Sheet Forming Defects Using Elastic-Plastic, Damage and Localization Models

    NASA Astrophysics Data System (ADS)

    Haddag, Badis; Abed-Meraim, Farid; Balan, Tudor

    2007-05-01

    In this work, an advanced anisotropic elastic-plasticity model is combined with a damage model and a strain localization criterion in the aim to describe accurately the mechanical behavior of sheet metals. Large strain, fully three-dimensional, implicit time integration algorithms are developed for this model and implemented in the finite element code Abaqus. The resulting code is used to predict the strain localization limits as well as the springback after forming of sheet steels. The impact of strain-path dependent hardening models on the limit strains and on the amount of springback is addressed.

  3. Finite elastic-plastic deformation of polycrystalline metals

    NASA Technical Reports Server (NTRS)

    Iwakuma, T.; Nemat-Nasser, S.

    1984-01-01

    Applying Hill's self-consistent method to finite elastic-plastic deformations, the overall moduli of polycrystalline solids are estimated. The model predicts a Bauschinger effect, hardening, and formation of vertex or corner on the yield surface for both microscopically non-hardening and hardening crystals. The changes in the instantaneous moduli with deformation are examined, and their asymptotic behavior, especially in relation to possible localization of deformations, is discussed. An interesting conclusion is that small second-order quantities, such as shape changes of grains and residual stresses (measured relative to the crystal elastic moduli), have a first-order effect on the overall response, as they lead to a loss of the overall stability by localized deformation. The predicted incipience of localization for a uniaxial deformation in two dimensions depends on the initial yield strain, but the orientation of localization is slightly less than 45 deg with respect to the tensile direction, although the numerical instability makes it very difficult to estimate this direction accurately.

  4. ZIP3D: An elastic and elastic-plastic finite-element analysis program for cracked bodies

    NASA Technical Reports Server (NTRS)

    Shivakumar, K. N.; Newman, J. C., Jr.

    1990-01-01

    ZIP3D is an elastic and an elastic-plastic finite element program to analyze cracks in three dimensional solids. The program may also be used to analyze uncracked bodies or multi-body problems involving contacting surfaces. For crack problems, the program has several unique features including the calculation of mixed-mode strain energy release rates using the three dimensional virtual crack closure technique, the calculation of the J integral using the equivalent domain integral method, the capability to extend the crack front under monotonic or cyclic loading, and the capability to close or open the crack surfaces during cyclic loading. The theories behind the various aspects of the program are explained briefly. Line-by-line data preparation is presented. Input data and results for an elastic analysis of a surface crack in a plate and for an elastic-plastic analysis of a single-edge-crack-tension specimen are also presented.

  5. Models for elastic shells with incompatible strains

    PubMed Central

    Lewicka, Marta; Mahadevan, L.; Pakzad, Mohammad Reza

    2014-01-01

    The three-dimensional shapes of thin lamina, such as leaves, flowers, feathers, wings, etc., are driven by the differential strain induced by the relative growth. The growth takes place through variations in the Riemannian metric given on the thin sheet as a function of location in the central plane and also across its thickness. The shape is then a consequence of elastic energy minimization on the frustrated geometrical object. Here, we provide a rigorous derivation of the asymptotic theories for shapes of residually strained thin lamina with non-trivial curvatures, i.e. growing elastic shells in both the weakly and strongly curved regimes, generalizing earlier results for the growth of nominally flat plates. The different theories are distinguished by the scaling of the mid-surface curvature relative to the inverse thickness and growth strain, and also allow us to generalize the classical Föppl–von Kármán energy to theories of prestrained shallow shells. PMID:24808750

  6. Tunable thermoelectric transport in nanomeshes via elastic strain engineering

    SciTech Connect

    Piccione, Brian; Gianola, Daniel S.

    2015-03-16

    Recent experimental explorations of silicon nanomeshes have shown that the unique metastructures exhibit reduced thermal conductivity while preserving bulk electrical conductivity via feature sizes between relevant phonon and electron mean free paths, aiding in the continued promise that nanometer-scale engineering may further enhance thermoelectric behavior. Here, we introduce a strategy for tuning thermoelectric transport phenomena in semiconductor nanomeshes via heterogeneous elastic strain engineering, using silicon as a model material for demonstration of the concept. By combining analytical models for electron mobility in uniformly stressed silicon with finite element analysis of strained silicon nanomeshes in a lumped physical model, we show that the nonuniform and multiaxial strain fields defined by the nanomesh geometry give rise to spatially varying band shifts and warping, which in aggregate accelerate electron transport along directions of applied stress. This allows for global electrical conductivity and Seebeck enhancements beyond those of homogenous samples under equivalent far-field stresses, ultimately increasing thermoelectric power factor nearly 50% over unstrained samples. The proposed concept and structures—generic to a wide class of materials with large dynamic ranges of elastic strain in nanoscale volumes—may enable a new pathway for active and tunable control of transport properties relevant to waste heat scavenging and thermal management.

  7. Tunable thermoelectric transport in nanomeshes via elastic strain engineering

    NASA Astrophysics Data System (ADS)

    Piccione, Brian; Gianola, Daniel S.

    2015-03-01

    Recent experimental explorations of silicon nanomeshes have shown that the unique metastructures exhibit reduced thermal conductivity while preserving bulk electrical conductivity via feature sizes between relevant phonon and electron mean free paths, aiding in the continued promise that nanometer-scale engineering may further enhance thermoelectric behavior. Here, we introduce a strategy for tuning thermoelectric transport phenomena in semiconductor nanomeshes via heterogeneous elastic strain engineering, using silicon as a model material for demonstration of the concept. By combining analytical models for electron mobility in uniformly stressed silicon with finite element analysis of strained silicon nanomeshes in a lumped physical model, we show that the nonuniform and multiaxial strain fields defined by the nanomesh geometry give rise to spatially varying band shifts and warping, which in aggregate accelerate electron transport along directions of applied stress. This allows for global electrical conductivity and Seebeck enhancements beyond those of homogenous samples under equivalent far-field stresses, ultimately increasing thermoelectric power factor nearly 50% over unstrained samples. The proposed concept and structures—generic to a wide class of materials with large dynamic ranges of elastic strain in nanoscale volumes—may enable a new pathway for active and tunable control of transport properties relevant to waste heat scavenging and thermal management.

  8. Elastic scattering by finitely many point-like obstacles

    NASA Astrophysics Data System (ADS)

    Hu, Guanghui; Sini, Mourad

    2013-04-01

    This paper is concerned with the time-harmonic elastic scattering by a finite number N of point-like obstacles in {{R}}^n (n = 2, 3). We analyze the N-point interactions model in elasticity and derive the associated Green's tensor (integral kernel) in terms of the point positions and the scattering coefficients attached to them, following the approach in quantum mechanics for modeling N-particle interactions. In particular, explicit expressions are given for the scattered near and far fields corresponding to elastic plane waves or point-source incidences. As a result, we rigorously justify the Foldy method for modeling the multiple scattering by finitely many point-like obstacles for the Lamé model. The arguments are based on the Fourier analysis and the Weinstein-Aronszajn inversion formula of the resolvent for the finite rank perturbations of closed operators in Hilbert spaces.

  9. Finite gradient elasticity and plasticity: a constitutive mechanical framework

    NASA Astrophysics Data System (ADS)

    Bertram, Albrecht

    2015-11-01

    Following a suggestion by Forest and Sievert (Acta Mech 160:71-111, 2003), a constitutive frame for a general gradient elastoplasticity for finite deformations is established. The basic assumptions are the principle of Euclidean invariance and the isomorphy of the elastic ranges. Both the elastic and the plastic laws include the first and the second deformation gradient. The starting point is an objective expression for the stress power.

  10. Elastic-plastic finite element analysis-to-test correlation for structures subjected to dynamic loading

    SciTech Connect

    Hodge, S.C.; Minicucci, J.M.

    1997-11-01

    A test program was undertaken to demonstrate the ability of elastic-plastic finite element methods to predict dynamic inelastic response for simple structural members. Cantilever and fixed-beam specimens were tested to levels that produced plastic straining in the range of 2.0% and to 3.0% and permanent sets. Acceleration, strain, and displacement data were recorded for use in analytical correlation. Correlation analyses were performed using the ABAQUS finite element code. Results of the correlation show that current elastic-plastic analysis techniques accurately capture dynamic inelastic response (displacement, acceleration) due to rapidly applied dynamic loading. Peak elastic and inelastic surface strains are accurately predicted. To accurately capture inelastic straining near connections, a solid model, including fillet welds, is necessary. The hardening models currently available in the ABAQUS code (isotropic, kinematic) do not accurately capture inelastic strain reversals caused by specimen rebound. Analyses performed consistently underpredicted the peak strain level of the first inelastic reversal and the rebound deflection and overpredicted the permanent set of structures experiencing inelastic rebound. Based on these findings, an improved hardening model is being implemented in the ABAQUS code by the developers. The intent of this model upgrade is to improve the ability of the program to capture inelastic strain reversals and to predict permanent sets.

  11. Finite element methods for nonlinear elastostatic problems in rubber elasticity

    NASA Technical Reports Server (NTRS)

    Oden, J. T.; Becker, E. B.; Miller, T. H.; Endo, T.; Pires, E. B.

    1983-01-01

    A number of finite element methods for the analysis of nonlinear problems in rubber elasticity are outlined. Several different finite element schemes are discussed. These include the augmented Lagrangian method, continuation or incremental loading methods, and associated Riks-type methods which have the capability of incorporating limit point behavior and bifurcations. Algorithms for the analysis of limit point behavior and bifurcations are described and the results of several numerical experiments are presented. In addition, a brief survey of some recent work on modelling contact and friction in elasticity problems is given. These results pertain to the use of new nonlocal and nonlinear friction laws.

  12. Finite element analysis of fluid-filled elastic piping systems

    NASA Technical Reports Server (NTRS)

    Everstine, G. C.; Marcus, M. S.; Quezon, A. J.

    1983-01-01

    Two finite element procedures are described for predicting the dynamic response of general 3-D fluid-filled elastic piping systems. The first approach, a low frequency procedure, models each straight pipe or elbow as a sequence of beams. The contained fluid is modeled as a separate coincident sequence axial members (rods) which are tied to the pipe in the lateral direction. The model includes the pipe hoop strain correction to the fluid sound speed and the flexibility factor correction to the elbow flexibility. The second modeling approach, an intermediate frequency procedure, follows generally the original Zienkiewicz-Newton scheme for coupled fluid-structure problems except that the velocity potential is used as the fundamental fluid unknown to symmetrize the coefficient matrices. From comparisons of the beam model predictions to both experimental data and the 3-D model, the beam model is validated for frequencies up to about two-thirds of the lowest fluid-filled labor pipe mode. Accurate elbow flexibility factors are seen to be crucial for effective beam modeling of piping systems.

  13. Influence of thermal residual stresses on the elastic phase-strain

    SciTech Connect

    Shi, N.; Bourke, M.A.M.; Goldstone, J.A.

    1996-04-01

    The development of elastic lattice phase strains in a 15 vol. pct TiC particulate reinforced 2219-T6 Al composite was modeled as a function of tensile uniaxial loading by finite element method (FEM). In the relationship of applied stress vs. elastic lattice phase strain, the slopes vary with the applied load even before the macroscopic yielding. The slopes for the phase-strain perpendicular to loading follow nonmonotonic changes with loading, while, in the direction parallel to loading, the slopes change monotonically with the applied load. In this investigation, we have demonstrated via FEM that thermal residual stresses from thermal expansion mismatch between phases affect initiation of matrix plasticity. And the differences in the matrix plasticity initiation influence the internal stress distribution. The changes in the slope are dictated by the internal stress transfer between phases. FEM models with and without thermal history show significant differences in the response of elastic strain component, a mechanics equivalent of the lattice elastic strain. Agreement with experiment can only be obtained by including the thermal history. From a simple elasto-plastic spring model we are able to demonstrate that, with matrix plasticity propagating as predicted by FEM, the elastic strain component responds similarly to the more rigorous numerical predictions, suggesting that the morphology of elastic strain evolution is dictated by the development of matrix plasticity.

  14. Constitutive modeling and computational implementation for finite strain plasticity

    NASA Technical Reports Server (NTRS)

    Reed, K. W.; Atluri, S. N.

    1985-01-01

    This paper describes a simple alternate approach to the difficult problem of modeling material behavior. Starting from a general representation for a rate-tpe constitutive equation, it is shown by example how sets of test data may be used to derive restrictions on the scalar functions appearing in the representation. It is not possible to determine these functions from experimental data, but the aforementioned restrictions serve as a guide in their eventual definition. The implications are examined for hypo-elastic, isotropically hardening plastic, and kinematically hardening plastic materials. A simple model for the evolution of the 'back-stress,' in a kinematic-hardening plasticity theory, that is entirely analogous to a hypoelastic stress-strain relation is postulated and examined in detail in modeling finitely plastic tension-torsion test. The implementation of rate-type material models in finite element algorithms is also discussed.

  15. Automated Finite Element Analysis of Elastically-Tailored Plates

    NASA Technical Reports Server (NTRS)

    Jegley, Dawn C. (Technical Monitor); Tatting, Brian F.; Guerdal, Zafer

    2003-01-01

    A procedure for analyzing and designing elastically tailored composite laminates using the STAGS finite element solver has been presented. The methodology used to produce the elastic tailoring, namely computer-controlled steering of unidirectionally reinforced composite material tows, has been reduced to a handful of design parameters along with a selection of construction methods. The generality of the tow-steered ply definition provides the user a wide variety of options for laminate design, which can be automatically incorporated with any finite element model that is composed of STAGS shell elements. Furthermore, the variable stiffness parameterization is formulated so that manufacturability can be assessed during the design process, plus new ideas using tow steering concepts can be easily integrated within the general framework of the elastic tailoring definitions. Details for the necessary implementation of the tow-steering definitions within the STAGS hierarchy is provided, and the format of the ply definitions is discussed in detail to provide easy access to the elastic tailoring choices. Integration of the automated STAGS solver with laminate design software has been demonstrated, so that the large design space generated by the tow-steering options can be traversed effectively. Several design problems are presented which confirm the usefulness of the design tool as well as further establish the potential of tow-steered plies for laminate design.

  16. Finite-temperature elasticity of fcc Al: Atomistic simulations and ultrasonic measurements

    NASA Astrophysics Data System (ADS)

    Pham, Hieu H.; Williams, Michael E.; Mahaffey, Patrick; Radovic, Miladin; Arroyave, Raymundo; Cagin, Tahir

    2011-08-01

    Though not very often, there are some cases in the literature where discrepancies exist in the temperature dependence of elastic constants of materials. A particular example of this case is the behavior of C12 coefficient of a simple metal, aluminum. In this paper we attempt to provide insight into various contributions to temperature dependence in elastic properties by investigating the thermoelastic properties of fcc aluminum as a function of temperature through the use of two computational techniques and experiments. First, ab initio calculations based on density functional theory (DFT) are used in combination with quasiharmonic theory to calculate the elastic constants at finite temperatures through a strain-free energy approach. Molecular dynamics (MD) calculations using tight-binding potentials are then used to extract the elastic constants through a fluctuation-based formalism. Through this dynamic approach, the different contributions (Born, kinetic, and stress fluctuations) to the elastic constants are isolated and the underlying physical basis for the observed thermally induced softening is elucidated. The two approaches are then used to shed light on the relatively large discrepancies in the reported temperature dependence of the elastic constants of fcc aluminum. Finally, the polycrystalline elastic constants (and their temperature dependence) of fcc aluminum are determined using resonant ultrasound spectroscopy (RUS) and compared to previously published data as well as the atomistic calculations performed in this work.

  17. Rolling motion of an elastic cylinder induced by elastic strain gradients

    NASA Astrophysics Data System (ADS)

    Chen, Lei; Chen, Shaohua

    2014-10-01

    Recent experiment shows that an elastic strain gradient field can be utilized to transport spherical particles on a stretchable substrate by rolling, inspired by which a generalized plane-strain Johnson-Kendall-Roberts model is developed in this paper in order to verify possible rolling of an elastic cylinder adhering on an elastic substrate subject to a strain gradient. With the help of contact mechanics, closed form solutions of interface tractions, stress intensity factors, and corresponding energy release rates in the plane-strain contact model are obtained, based on which a possible rolling motion of an elastic cylinder induced by strain gradients is found and the criterion for the initiation of rolling is established. The theoretical prediction is consistent well with the existing experimental observation. The result should be helpful for understanding biological transport mechanisms through muscle contractions and the design of transport systems with strain gradient.

  18. Solution of elastic-plastic stress analysis problems by the p-version of the finite element method

    NASA Technical Reports Server (NTRS)

    Szabo, Barna A.; Actis, Ricardo L.; Holzer, Stefan M.

    1993-01-01

    The solution of small strain elastic-plastic stress analysis problems by the p-version of the finite element method is discussed. The formulation is based on the deformation theory of plasticity and the displacement method. Practical realization of controlling discretization errors for elastic-plastic problems is the main focus. Numerical examples which include comparisons between the deformation and incremental theories of plasticity under tight control of discretization errors are presented.

  19. Solution of elastic-plastic stress analysis problems by the P-version of the finite element method

    SciTech Connect

    Szabo, B.A.; Holzer, S.M.; Actis, R.L.

    1995-12-31

    The solution of small-strain elastic-plastic stress analysis problems by the p-version of the finite element method is discussed. The formulation is based on the deformation theory of plasticity and the displacement method. Practical realization of controlling discretization errors for elastic-plastic problems is the main focus of the paper. Numerical examples, which include comparisons between the deformation and incremental theories of plasticity under tight control of discretization errors, are presented.

  20. Development of the average lattice phase-strain and global elastic macro-strain in Al/TiC composites

    SciTech Connect

    Shi, N.; Bourke, M.A.M.; Goldstone, J.A.; Allison, J.E.

    1994-02-01

    The development of elastic lattice phase strains and global elastic macro-strain in a 15 vol% TiC particle reinforced 2219-T6 Al composite was modeled by finite element method (FEM) as a function of tensile uniaxial loading. The numerical predictions are in excellent agreement with strain measurements at a spallation neutron source. Results from the measurements and modeling indicate that the lattice phase-strains go through a ``zigzag`` increase with the applied load in the direction perpendicular to the load, while the changes of slope in the parallel direction are monotonic. FEM results further showed that it is essential to consider the effect of thermal residual stresses (TRS) in understanding this anomalous behavior. It was demonstrated that, due to TRS, the site of matrix plastic flow initiation changed. On the other hand, the changes of slope of the elastic global macrostrain is solely determined by the phase-stress partition in the composite. An analytical calculation showed that both experimental and numerical slope changes during elastic global strain response under loading could be accurately reproduced by accounting for the changes of phase-stress ratio between the matrix and the matrix.

  1. Elastic finite-difference method for irregular grids

    SciTech Connect

    Oprsal, I.; Zahradnik, J.

    1999-01-01

    Finite-difference (FD) modeling of complicated structures requires simple algorithms. This paper presents a new elastic FD method for spatially irregular grids that is simple and, at the same time, saves considerable memory and computing time. Features like faults, low-velocity layers, cavities, and/or nonplanar surfaces are treated on a fine grid, while the remaining parts of the model are, with equal accuracy, represented on a coarse grid. No interpolation is needed between the fine and coarse parts due to the rectangular grid cells. Relatively abrupt transitions between the small and large grid steps produce no numerical artifacts in the present method. Planar or nonplanar free surfaces, including underground cavities, are treated in a way similar to internal grid points but with consideration of the zero-valued elastic parameters and density outside the free surface (vacuum formalism). A theoretical proof that vacuum formalism fulfills the free-surface conditions is given. Numerical validation is performed through comparison with independent methods, comparing FD with explicitly prescribed boundary conditions and finite elements. Memory and computing time needed in the studied models was only about 10 to 40% of that employing regular square grids of equal accuracy. A practical example of a synthetic seismic section, showing clear signatures of a coal seam and cavity, is presented. The method can be extended to three dimensions.

  2. Stress-dependent finite growth in soft elastic tissues.

    PubMed

    Rodriguez, E K; Hoger, A; McCulloch, A D

    1994-04-01

    Growth and remodeling in tissues may be modulated by mechanical factors such as stress. For example, in cardiac hypertrophy, alterations in wall stress arising from changes in mechanical loading lead to cardiac growth and remodeling. A general continuum formulation for finite volumetric growth in soft elastic tissues is therefore proposed. The shape change of an unloaded tissue during growth is described by a mapping analogous to the deformation gradient tensor. This mapping is decomposed into a transformation of the local zero-stress reference state and an accompanying elastic deformation that ensures the compatibility of the total growth deformation. Residual stress arises from this elastic deformation. Hence, a complete kinematic formulation for growth in general requires a knowledge of the constitutive law for stress in the tissue. Since growth may in turn be affected by stress in the tissue, a general form for the stress-dependent growth law is proposed as a relation between the symmetric growth-rate tensor and the stress tensor. With a thick-walled hollow cylinder of incompressible, isotropic hyperelastic material as an example, the mechanics of left ventricular hypertrophy are investigated. The results show that transmurally uniform pure circumferential growth, which may be similar to eccentric ventricular hypertrophy, changes the state of residual stress in the heart wall. A model of axially loaded bone is used to test a simple stress-dependent growth law in which growth rate depends on the difference between the stress due to loading and a predetermined growth equilibrium stress. PMID:8188726

  3. Finite element investigation of thermo-elastic and thermo-plastic consolidation

    SciTech Connect

    Aboustit, B.L.

    1984-01-01

    The transient response of saturated continua due to thermal as well as mechanical loads is investigated in both elastic and plastic ranges. When the two phase saturated media are subjected to thermomechanical loading, the energy equation is coupled with the mass flow and solid deformation equations resulting in the initial boundary value problem of thermal consolidation. The solid behavior may be assumed to be either elastic or elastoplastic leading to the associated theories of thermoelastic and thermoelastoplastic consolidation. The governing equations for the quasi-static infinitesimal theory of thermoelastic consolidation are developed by using the theory of mixtures. An equivalent variational principle is developed along with associated finite element formulations. Two isoparametric elements of the composite type are employed for the spatial discretization. The formulation is extended to the plastic ranges by modeling the solid phase as an elastic work hardening material with an associated flow rule. An incremental iterative scheme is developed to solve this nonlinear transient problem. Several special purpose computer codes are developed for evaluating the isothermal, thermal, elastic and elastoplastic plane strain consolidation responses. These codes have been evaluated against limiting cases available in the literature. The effects of temporal and spatial interpolation schemes are investigated for one-dimensional thermoelastic consolidation problems. An application dealing with a plane strain underground coal gasification problem is also presented.

  4. Coupling finite and boundary element methods for 2-D elasticity problems

    NASA Technical Reports Server (NTRS)

    Krishnamurthy, T.; Raju, I. S.; Sistla, R.

    1993-01-01

    A finite element-boundary element (FE-BE) coupling method for two-dimensional elasticity problems is developed based on a weighted residual variational method in which a portion of the domain of interest is modeled by FEs and the remainder of the region by BEs. The performance of the FE-BE coupling method is demonstrated via applications to a simple 'patch test' problem and three-crack problems. The method passed the patch tests for various modeling configurations and yielded accurate strain energy release rates for the crack problems studied.

  5. Three-dimensional elastic-plastic finite-element analysis of fatigue crack propagation

    NASA Technical Reports Server (NTRS)

    Goglia, G. L.; Chermahini, R. G.

    1985-01-01

    Fatigue cracks are a major problem in designing structures subjected to cyclic loading. Cracks frequently occur in structures such as aircraft and spacecraft. The inspection intervals of many aircraft structures are based on crack-propagation lives. Therefore, improved prediction of propagation lives under flight-load conditions (variable-amplitude loading) are needed to provide more realistic design criteria for these structures. The main thrust was to develop a three-dimensional, nonlinear, elastic-plastic, finite element program capable of extending a crack and changing boundary conditions for the model under consideration. The finite-element model is composed of 8-noded (linear-strain) isoparametric elements. In the analysis, the material is assumed to be elastic-perfectly plastic. The cycle stress-strain curve for the material is shown Zienkiewicz's initial-stress method, von Mises's yield criterion, and Drucker's normality condition under small-strain assumptions are used to account for plasticity. The three-dimensional analysis is capable of extending the crack and changing boundary conditions under cyclic loading.

  6. Anisotropic finite strain viscoelasticity based on the Sidoroff multiplicative decomposition and logarithmic strains

    NASA Astrophysics Data System (ADS)

    Latorre, Marcos; Montáns, Francisco Javier

    2015-09-01

    In this paper a purely phenomenological formulation and finite element numerical implementation for quasi-incompressible transversely isotropic and orthotropic materials is presented. The stored energy is composed of distinct anisotropic equilibrated and non-equilibrated parts. The nonequilibrated strains are obtained from the multiplicative decomposition of the deformation gradient. The procedure can be considered as an extension of the Reese and Govindjee framework to anisotropic materials and reduces to such formulation for isotropic materials. The stress-point algorithmic implementation is based on an elastic-predictor viscous-corrector algorithm similar to that employed in plasticity. The consistent tangent moduli for the general anisotropic case are also derived. Numerical examples explain the procedure to obtain the material parameters, show the quadratic convergence of the algorithm and usefulness in multiaxial loading. One example also highlights the importance of prescribing a complete set of stress-strain curves in orthotropic materials.

  7. A solid-shell Cosserat point element (SSCPE) for elastic thin structures at finite deformation

    NASA Astrophysics Data System (ADS)

    Jabareen, Mahmood; Mtanes, Eli

    2016-04-01

    The objective of this study is to develop a new solid-shell element using the Cosserat point theory for modeling thin elastic structures at finite deformations. The point-wise Green-Lagrange strain tensor is additively decomposed into homogeneous and inhomogeneous parts. Only the latter part of the strain tensor is modified by the assumed natural strain ANS concept to avoid both curvature-thickness locking and transverse shear locking. To the authors' knowledge, such modification has not been applied yet in the literature, and here it is referred to as the assumed natural inhomogeneous strain ANIS concept. Moreover, a new methodology for determining the constitutive coefficients of the strain energy function, which controls the inhomogeneous deformations, is proposed. The resulting coefficients ensure both accuracy, robustness, and elimination of all locking pathologies in the solid-shell Cosserat point element (SSCPE). The performance of the developed SSCPE is verified and tested via various benchmark problems and compared to other solid, shell, and solid-shell elements. These examples demonstrate that the SSCPE is accurate, robust, stable, free of locking, and can be used for modeling thin structures at both small and finite deformations.

  8. A solid-shell Cosserat point element ( SSCPE) for elastic thin structures at finite deformation

    NASA Astrophysics Data System (ADS)

    Jabareen, Mahmood; Mtanes, Eli

    2016-07-01

    The objective of this study is to develop a new solid-shell element using the Cosserat point theory for modeling thin elastic structures at finite deformations. The point-wise Green-Lagrange strain tensor is additively decomposed into homogeneous and inhomogeneous parts. Only the latter part of the strain tensor is modified by the assumed natural strain ANS concept to avoid both curvature-thickness locking and transverse shear locking. To the authors' knowledge, such modification has not been applied yet in the literature, and here it is referred to as the assumed natural inhomogeneous strain ANIS concept. Moreover, a new methodology for determining the constitutive coefficients of the strain energy function, which controls the inhomogeneous deformations, is proposed. The resulting coefficients ensure both accuracy, robustness, and elimination of all locking pathologies in the solid-shell Cosserat point element ( SSCPE). The performance of the developed SSCPE is verified and tested via various benchmark problems and compared to other solid, shell, and solid-shell elements. These examples demonstrate that the SSCPE is accurate, robust, stable, free of locking, and can be used for modeling thin structures at both small and finite deformations.

  9. Atomistic modeling of diffusional phasetransformations with elastic strain

    SciTech Connect

    Mason, D R; Rudd, R E; Sutton, A P

    2003-10-31

    Phase transformations in 2xxx series aluminium alloys (Al-Cu-Mg) are investigated with an off-lattice atomistic kinetic Monte Carlo simulation incorporating the effects of strain around misfitting atoms and vacancies. Atomic interactions are modelled by Finnis-Sinclair potentials constructed for these simulations. Vacancy diffusion is modelled by comparing the energies of trial states, where the system is partially relaxed for each trial state. No special requirements are made about the description of atomic interactions, making our approach suitable for more fundamentally based models such as tight binding if sufficient computational resources are available. Only a limited precision is required for the energy of each trial state, determined by the value of kBT. Since the change in the relaxation displacement field caused by a vacancy hop decays as 1/r{sup 3} , it is sufficient to determine the next move by relaxing only those atoms in a sphere of finite radius centred on the moving vacancy. However, once the next move has been selected, the entire system is relaxed. Simulations of the early stages of phase separation in Al-Cu with elastic relaxation show an enhanced rate of clustering compared to those performed on the same system with a rigid lattice.

  10. Evidence for residual elastic strain in deformed natural quartz

    SciTech Connect

    Kunz, Martin; Chen, Kai; Tamura,Nobumichi; Wenk, Hans-Rudolf

    2009-01-30

    Residual elastic strain in naturally deformed, quartz-containing rocks can be measured quantitatively in a petrographic thin section with high spatial resolution using Laue microdiffraction with white synchrotron x-rays. The measurements with a resolution of one micrometer allow the quantitative determination of the deviatoric strain tensor as a function of position within the crystal investigated. The observed equivalent strain values of 800-1200 microstrains represent a lower bound of the actual preserved residual strain in the rock, since the stress component perpendicular to the cut sample surface plane is released. The measured equivalent strain translates into an equivalent stress in the order of {approx} 50 MPa.

  11. Finite gradient elasticity and plasticity: a constitutive thermodynamical framework

    NASA Astrophysics Data System (ADS)

    Bertram, Albrecht

    2016-05-01

    In Bertram (Continuum Mech Thermodyn. doi: 10.1007/s00161-014-0387-0 , 2015), a mechanical framework for finite gradient elasticity and plasticity has been given. In the present paper, this is extended to thermodynamics. The mechanical theory is only briefly repeated here. A format for a rather general constitutive theory including all thermodynamic fields is given in a Euclidian invariant setting. The plasticity theory is rate-independent and unconstrained. The Clausius-Duhem inequality is exploited to find necessary and sufficient conditions for thermodynamic consistency. The residual dissipation inequality restricts the flow and hardening rules in combination with the yield criterion.

  12. Visualization of elastic wavefields computed with a finite difference code

    SciTech Connect

    Larsen, S.; Harris, D.

    1994-11-15

    The authors have developed a finite difference elastic propagation model to simulate seismic wave propagation through geophysically complex regions. To facilitate debugging and to assist seismologists in interpreting the seismograms generated by the code, they have developed an X Windows interface that permits viewing of successive temporal snapshots of the (2D) wavefield as they are calculated. The authors present a brief video displaying the generation of seismic waves by an explosive source on a continent, which propagate to the edge of the continent then convert to two types of acoustic waves. This sample calculation was part of an effort to study the potential of offshore hydroacoustic systems to monitor seismic events occurring onshore.

  13. Near tip stress and strain fields for short elastic cracks

    NASA Technical Reports Server (NTRS)

    Soediono, A. H.; Kardomateas, G. A.; Carlson, R. L.

    1994-01-01

    Recent experimental fatigue crack growth studies have concluded an apparent anomalous behavior of short cracks. To investigate the reasons for this unexpected behavior, the present paper focuses on identifying the crack length circumstances under which the requirements for a single parameter (K(sub I) or delta K(sub I) if cyclic loading is considered) characterization are violated. Furthermore, an additional quantity, the T stress, as introduced by Rice, and the related biaxiality ratio, B, are calculated for several crack lengths and two configurations, the single-edge-cracked and the centrally-cracked specimen. It is postulated that a two-parameter characterization by K and T (or B) is needed for the adequate description of the stress and strain field around a short crack. To further verify the validity of this postulate, the influence of the third term of the Williams series on the stress, strain and displacement fields around the crack tip and in particular on the B parameter is also examined. It is found that the biaxiality ratio would be more negative if the third term effects are included in both geometries. The study is conducted using the finite element method with linearly elastic material and isoparametric elements and axial (mode I) loading. Moreover, it is clearly shown that it is not proper to postulate the crack size limits for 'short crack' behavior as a normalized ratio with the specimen width, a/w; it should instead be stated as an absolute, or normalized with respect to a small characteristic dimension such as the grain size. Finally, implications regarding the prediction of cyclic (fatigue) growth of short cracks are discussed.

  14. Elastic Wave Radiation from a Line Source of Finite Length

    SciTech Connect

    Aldridge, D.F.

    1998-11-04

    Straightforward algebraic expressions describing the elastic wavefield produced by a line source of finite length are derived in circular cylindrical coordinates. The surrounding elastic medium is assumed to be both homogeneous and isotropic, anc[ the source stress distribution is considered axisymmetic. The time- and space-domain formulae are accurate at all distances and directions from the source; no fa-field or long-wavelength assumptions are adopted for the derivation. The mathematics yield a unified treatment of three different types of sources: an axial torque, an axial force, and a radial pressure. The torque source radiates only azirnuthally polarized shear waves, whereas force and pressure sources generate simultaneous compressional and shear radiation polarized in planes containing the line source. The formulae reduce to more familiar expressions in the two limiting cases where the length of the line source approaches zero and infinity. Far-field approximations to the exact equations indicate that waves radiated parallel to the line source axI.s are attenuated relative to those radiated normal to the axis. The attenuation is more severe for higher I?equencies and for lower wavespeeds. Hence, shear waves are affected more than compressional waves. This fi-equency- and directiondependent attenuation is characterized by an extremely simple mathematical formula, and is readily apparent in example synthetic seismograms.

  15. Two-dimensional Finite Element Modeling for Modeling Tectonic Stress and Strain

    NASA Technical Reports Server (NTRS)

    Lyzenga, G. A.; Raefsky, A.

    1983-01-01

    Techniques of finite element analysis in two dimensional plane strain were applied to problems of geophysics and tectonics. More specifically, the flexibility of the finite element method was employed to address problems involving geological complexity and fault interactions. The modeling of effective anisotropy in material elastic properties proved useful in describing the deformation of faulted crustal blocks. The applications of this modeling work to problems of actual tectonics in southern California was explored. Preliminary models show encouraging agreement with measured tectonic strain in this region, and modeling work was done to gain an understanding of the stress state in a locked fault region with future seismic potential.

  16. Approaching the ideal elastic strain limit in silicon nanowires.

    PubMed

    Zhang, Hongti; Tersoff, Jerry; Xu, Shang; Chen, Huixin; Zhang, Qiaobao; Zhang, Kaili; Yang, Yong; Lee, Chun-Sing; Tu, King-Ning; Li, Ju; Lu, Yang

    2016-08-01

    Achieving high elasticity for silicon (Si) nanowires, one of the most important and versatile building blocks in nanoelectronics, would enable their application in flexible electronics and bio-nano interfaces. We show that vapor-liquid-solid-grown single-crystalline Si nanowires with diameters of ~100 nm can be repeatedly stretched above 10% elastic strain at room temperature, approaching the theoretical elastic limit of silicon (17 to 20%). A few samples even reached ~16% tensile strain, with estimated fracture stress up to ~20 GPa. The deformations were fully reversible and hysteresis-free under loading-unloading tests with varied strain rates, and the failures still occurred in brittle fracture, with no visible sign of plasticity. The ability to achieve this "deep ultra-strength" for Si nanowires can be attributed mainly to their pristine, defect-scarce, nanosized single-crystalline structure and atomically smooth surfaces. This result indicates that semiconductor nanowires could have ultra-large elasticity with tunable band structures for promising "elastic strain engineering" applications. PMID:27540586

  17. Approaching the ideal elastic strain limit in silicon nanowires

    PubMed Central

    Zhang, Hongti; Tersoff, Jerry; Xu, Shang; Chen, Huixin; Zhang, Qiaobao; Zhang, Kaili; Yang, Yong; Lee, Chun-Sing; Tu, King-Ning; Li, Ju; Lu, Yang

    2016-01-01

    Achieving high elasticity for silicon (Si) nanowires, one of the most important and versatile building blocks in nanoelectronics, would enable their application in flexible electronics and bio-nano interfaces. We show that vapor-liquid-solid–grown single-crystalline Si nanowires with diameters of ~100 nm can be repeatedly stretched above 10% elastic strain at room temperature, approaching the theoretical elastic limit of silicon (17 to 20%). A few samples even reached ~16% tensile strain, with estimated fracture stress up to ~20 GPa. The deformations were fully reversible and hysteresis-free under loading-unloading tests with varied strain rates, and the failures still occurred in brittle fracture, with no visible sign of plasticity. The ability to achieve this “deep ultra-strength” for Si nanowires can be attributed mainly to their pristine, defect-scarce, nanosized single-crystalline structure and atomically smooth surfaces. This result indicates that semiconductor nanowires could have ultra-large elasticity with tunable band structures for promising “elastic strain engineering” applications. PMID:27540586

  18. Finite Difference Elastic Wave Field Simulation On GPU

    NASA Astrophysics Data System (ADS)

    Hu, Y.; Zhang, W.

    2011-12-01

    Numerical modeling of seismic wave propagation is considered as a basic and important aspect in investigation of the Earth's structure, and earthquake phenomenon. Among various numerical methods, the finite-difference method is considered one of the most efficient tools for the wave field simulation. However, with the increment of computing scale, the power of computing has becoming a bottleneck. With the development of hardware, in recent years, GPU shows powerful computational ability and bright application prospects in scientific computing. Many works using GPU demonstrate that GPU is powerful . Recently, GPU has not be used widely in the simulation of wave field. In this work, we present forward finite difference simulation of acoustic and elastic seismic wave propagation in heterogeneous media on NVIDIA graphics cards with the CUDA programming language. We also implement perfectly matched layers on the graphics cards to efficiently absorb outgoing waves on the fictitious edges of the grid Simulations compared with the results on CPU platform shows reliable accuracy and remarkable efficiency. This work proves that GPU can be an effective platform for wave field simulation, and it can also be used as a practical tool for real-time strong ground motion simulation.

  19. Two Propositions on the Application of Point Elasticities to Finite Price Changes.

    ERIC Educational Resources Information Center

    Daskin, Alan J.

    1992-01-01

    Considers counterintuitive propositions about using point elasticities to estimate quantity changes in response to price changes. Suggests that elasticity increases with price along a linear demand curve, but falling quantity demand offsets it. Argues that point elasticity with finite percentage change in price only approximates percentage change…

  20. Internal elastic strains in an IF steel following changes in strain path

    SciTech Connect

    Wilson, D.V.; Bate, P.S.

    1996-08-01

    Residual elastic strains present in an IF steel following rolling and subsequent tensile deformation have been evaluated using X-ray diffraction. It was possible to decompose diffraction profiles into two symmetrical components notionally corresponding to dislocation walls and cell interiors and so estimate the volume fractions and mean elastic strains associated with these components of the microstructure following different deformation modes. The residual long range elastic strains were very small following rolling, but they were much greater following subsequent tensile elongation to macroscopic yield. The mean strains could only account for about one-third of the strain induced anisotropy of flow stress. It is concluded that insufficient dislocations accumulate at cell walls at macroscopic yield following a path change to give homogeneous loading of the dislocation walls, and that this effect can account for the difference between the macroscopic mechanical behavior and predictions from the X-ray strain measurements.

  1. A plane stress finite element model for elastic-plastic mode I/II crack growth

    NASA Astrophysics Data System (ADS)

    James, Mark Anthony

    A finite element program has been developed to perform quasi-static, elastic-plastic crack growth simulations. The model provides a general framework for mixed-mode I/II elastic-plastic fracture analysis using small strain assumptions and plane stress, plane strain, and axisymmetric finite elements. Cracks are modeled explicitly in the mesh. As the cracks propagate, automatic remeshing algorithms delete the mesh local to the crack tip, extend the crack, and build a new mesh around the new tip. State variable mapping algorithms transfer stresses and displacements from the old mesh to the new mesh. The von Mises material model is implemented in the context of a non-linear Newton solution scheme. The fracture criterion is the critical crack tip opening displacement, and crack direction is predicted by the maximum tensile stress criterion at the crack tip. The implementation can accommodate multiple curving and interacting cracks. An additional fracture algorithm based on nodal release can be used to simulate fracture along a horizontal plane of symmetry. A core of plane strain elements can be used with the nodal release algorithm to simulate the triaxial state of stress near the crack tip. Verification and validation studies compare analysis results with experimental data and published three-dimensional analysis results. Fracture predictions using nodal release for compact tension, middle-crack tension, and multi-site damage test specimens produced accurate results for residual strength and link-up loads. Curving crack predictions using remeshing/mapping were compared with experimental data for an Arcan mixed-mode specimen. Loading angles from 0 degrees to 90 degrees were analyzed. The maximum tensile stress criterion was able to predict the crack direction and path for all loading angles in which the material failed in tension. Residual strength was also accurately predicted for these cases.

  2. Three-dimensional elastic-plastic finite-element analyses of constraint variations in cracked bodies

    NASA Technical Reports Server (NTRS)

    Newman, J. C., Jr.; Bigelow, C. A.; Shivakumar, K. N.

    1993-01-01

    Three-dimensional elastic-plastic (small-strain) finite-element analyses were used to study the stresses, deformations, and constraint variations around a straight-through crack in finite-thickness plates for an elastic-perfectly plastic material under monotonic and cyclic loading. Middle-crack tension specimens were analyzed for thicknesses ranging from 1.25 to 20 mm with various crack lengths. Three local constraint parameters, related to the normal, tangential, and hydrostatic stresses, showed similar variations along the crack front for a given thickness and applied stress level. Numerical analyses indicated that cyclic stress history and crack growth reduced the local constraint parameters in the interior of a plate, especially at high applied stress levels. A global constraint factor alpha(sub g) was defined to simulate three-dimensional effects in two-dimensional crack analyses. The global constraint factor was calculated as an average through-the-thickness value over the crack-front plastic region. Values of alpha(sub g) were found to be nearly independent of crack length and were related to the stress-intensity factor for a given thickness.

  3. Finite element analysis of large transient elastic-plastic deformations of simple structures, with application to the engine rotor fragment containment/deflection problem

    NASA Technical Reports Server (NTRS)

    Wu, R. W.; Witmer, E. A.

    1972-01-01

    Assumed-displacement versions of the finite-element method are developed to predict large-deformation elastic-plastic transient deformations of structures. Both the conventional and a new improved finite-element variational formulation are derived. These formulations are then developed in detail for straight-beam and curved-beam elements undergoing (1) Bernoulli-Euler-Kirchhoff or (2) Timoshenko deformation behavior, in one plane. For each of these categories, several types of assumed-displacement finite elements are developed, and transient response predictions are compared with available exact solutions for small-deflection, linear-elastic transient responses. The present finite-element predictions for large-deflection elastic-plastic transient responses are evaluated via several beam and ring examples for which experimental measurements of transient strains and large transient deformations and independent finite-difference predictions are available.

  4. On local total strain redistribution using a simplified cyclic inelastic analysis based on an elastic solution

    NASA Technical Reports Server (NTRS)

    Hwang, S. Y.; Kaufman, A.

    1985-01-01

    Strain redistribution corrections were developed for a simplified inelastic analysis procedure to economically calculate material cyclic response at the critical location of a structure for life prediction purposes. The method was based on the assumption that the plastic region in the structure is local and the total strain history required for input can be defined from elastic finite element analyses. Cyclic stress-strain behavior was represented by a bilinear kinematic hardening model. The simplified procedure has been found to predict stress-strain response with reasonable accuracy for thermally cycled problems but needs improvement for mechanically load cycled problems. This study derived and incorporated Neuber type corrections in the simplified procedure to account for local total strain redistribution under cyclic mechanical loading. The corrected simplified method was exercised on a mechanically load cycled benchmark notched plate problem. Excellent agreement was found between the predicted material response and nonlinear finite element solutions for the problem. The simplified analysis computer program used 0.3 percent of the CPU time required for a nonlinear finite element analysis.

  5. Elastic-plastic mixed-iterative finite element analysis: Implementation and performance assessment

    NASA Technical Reports Server (NTRS)

    Sutjahjo, Edhi; Chamis, Christos C.

    1993-01-01

    An elastic-plastic algorithm based on Von Mises and associative flow criteria is implemented in MHOST-a mixed iterative finite element analysis computer program developed by NASA Lewis Research Center. The performance of the resulting elastic-plastic mixed-iterative analysis is examined through a set of convergence studies. Membrane and bending behaviors of 4-node quadrilateral shell finite elements are tested for elastic-plastic performance. Generally, the membrane results are excellent, indicating the implementation of elastic-plastic mixed-iterative analysis is appropriate.

  6. Medical ultrasound: imaging of soft tissue strain and elasticity

    PubMed Central

    Wells, Peter N. T.; Liang, Hai-Dong

    2011-01-01

    After X-radiography, ultrasound is now the most common of all the medical imaging technologies. For millennia, manual palpation has been used to assist in diagnosis, but it is subjective and restricted to larger and more superficial structures. Following an introduction to the subject of elasticity, the elasticity of biological soft tissues is discussed and published data are presented. The basic physical principles of pulse-echo and Doppler ultrasonic techniques are explained. The history of ultrasonic imaging of soft tissue strain and elasticity is summarized, together with a brief critique of previously published reviews. The relevant techniques—low-frequency vibration, step, freehand and physiological displacement, and radiation force (displacement, impulse, shear wave and acoustic emission)—are described. Tissue-mimicking materials are indispensible for the assessment of these techniques and their characteristics are reported. Emerging clinical applications in breast disease, cardiology, dermatology, gastroenterology, gynaecology, minimally invasive surgery, musculoskeletal studies, radiotherapy, tissue engineering, urology and vascular disease are critically discussed. It is concluded that ultrasonic imaging of soft tissue strain and elasticity is now sufficiently well developed to have clinical utility. The potential for further research is examined and it is anticipated that the technology will become a powerful mainstream investigative tool. PMID:21680780

  7. Finite circular plate on elastic foundation centrally loaded by rigid spherical indenter

    NASA Technical Reports Server (NTRS)

    Wadhwa, S. K.; Yang, P. P.

    1980-01-01

    The analytical solution of a finite circular plate on an elastic foundation centrally loaded by the rigid indenter is discussed. The procedure to use NASTRAN as a subroutine to iteratively converge to this solution numerically is described.

  8. Retaining large and adjustable elastic strains of kilogram-scale Nb nanowires [Better Superconductor by Elastic Strain Engineering: Kilogram-scale Free-Standing Niobium Metal Composite with Large Retained Elastic Strains

    DOE PAGESBeta

    Hao, Shijie; Cui, Lishan; Wang, Hua; Jiang, Daqiang; Liu, Yinong; Yan, Jiaqiang; Ren, Yang; Han, Xiaodong; Brown, Dennis E.; Li, Ju

    2016-02-10

    Crystals held at ultrahigh elastic strains and stresses may exhibit exceptional physical and chemical properties. Individual metallic nanowires can sustain ultra-large elastic strains of 4-7%. However, retaining elastic strains of such magnitude in kilogram-scale nanowires is challenging. Here, we find that under active load, ~5.6% elastic strain can be achieved in Nb nanowires in a composite material. Moreover, large tensile (2.8%) and compressive (-2.4%) elastic strains can be retained in kilogram-scale Nb nanowires when the composite is unloaded to a free-standing condition. It is then demonstrated that the retained tensile elastic strains of Nb nanowires significantly increase their superconducting transitionmore » temperature and critical magnetic fields, corroborating ab initio calculations based on BCS theory. This free-standing nanocomposite design paradigm opens new avenues for retaining ultra-large elastic strains in great quantities of nanowires and elastic-strain-engineering at industrial scale.« less

  9. Elastic strain relaxation in axial Si/Ge whisker heterostructures

    SciTech Connect

    Hanke, M.; Eisenschmidt, C.; Werner, P.; Zakharov, N. D.; Syrowatka, F.; Heyroth, F.; Schaefer, P.; Konovalov, O.

    2007-04-15

    The elastic behavior of molecular beam epitaxy-grown SiGe/Si(111) nanowhiskers (NWs) has been studied by means of electron microscopy, x-ray scattering, and numerical linear elasticity theory. Highly brilliant synchrotron radiation was applied to map the diffusely scattered intensity near the asymmetric (115) reciprocal lattice point. The larger lattice parameter with respect to the Si matrix causes a lateral lattice expansion within embedded Ge layers. This enables a clear separation of scattering due to NWs and laterally confined areas aside. Finite element calculations prove a lateral lattice compression in the Si matrix close to the NW apex above buried threefold and single Ge layer stacks. This suggests an incorporation probability, which additionally depends on the radial position within heteroepitaxial NWs.

  10. Controlling surface reactions with nanopatterned surface elastic strain.

    PubMed

    Li, Zhisheng; Potapenko, Denis V; Osgood, Richard M

    2015-01-27

    The application of elastic lattice strain is a promising approach for tuning material properties, but the attainment of a systematic approach for introducing a high level of strain in materials so as to study its effects has been a major challenge. Here we create an array of intense locally varying strain fields on a TiO2 (110) surface by introducing highly pressurized argon nanoclusters at 6-20 monolayers under the surface. By combining scanning tunneling microscopy imaging and the continuum mechanics model, we show that strain causes the surface bridge-bonded oxygen vacancies (BBOv), which are typically present on this surface, to be absent from the strained area and generates defect-free regions. In addition, we find that the adsorption energy of hydrogen binding to oxygen (BBO) is significantly altered by local lattice strain. In particular, the adsorption energy of hydrogen on BBO rows is reduced by ∼ 35 meV when the local crystal lattice is compressed by ∼ 1.3%. Our results provide direct evidence of the influence of strain on atomic-scale surface chemical properties, and such effects may help guide future research in catalysis materials design. PMID:25494489

  11. Do foliation refraction patterns around buckle folds represent finite strain?

    NASA Astrophysics Data System (ADS)

    Frehner, M.; Exner, U.

    2012-04-01

    Buckle folds in the field commonly feature a characteristic syn-deformational foliation, which is sub-parallel to the fold axial plane; hence it is called axial plane foliation. As the foliation is not perfectly parallel to the axial plane, it may exhibit either a divergent or convergent fan around the fold. Convergent fans most commonly occur in the stronger rocks (the folded layer) while divergent fans rather occur in the mechanically weaker rocks (the matrix). The foliation orientation is usually thought to reflect the long axes of the finite strain ellipses, a hypothesis that we investigate in our study. To study the strain distribution around folds, we use the finite-element method to simulate two-dimensional single-layer viscous buckling. The numerical simulations allow to calculate the strain evolution during the folding process and to visualize its distribution and orientation around the fold. We use different measures of strain: (1) the finite strain (recording the strain history from the beginning of the simulation until the end), (2) the infinitesimal strain (capturing only the very last moment of the simulation), (3) the incremental strain (recording the strain history from a certain shortening value during the simulation until the end), and (4) initially layer-orthogonal passive marker lines. The shortening value, from which the incremental strain is calculated, can be anything between the beginning and the end of the simulation. The first three strain measures are tensor fields that are used to calculate and visualize the orientation of the long axis of the strain ellipses around the fold. We find that all strain measures result in a divergent fan in the mechanically weak matrix at the outer arc of the fold and that this divergent fan has almost the same geometry for all strain measures. Also, for the case of the incremental strain, the divergent fan does hardly depend on the moment from which the incremental strain is calculated. This observation

  12. Retaining Large and Adjustable Elastic Strains of Kilogram-Scale Nb Nanowires.

    PubMed

    Hao, Shijie; Cui, Lishan; Wang, Hua; Jiang, Daqiang; Liu, Yinong; Yan, Jiaqiang; Ren, Yang; Han, Xiaodong; Brown, Dennis E; Li, Ju

    2016-02-10

    Individual metallic nanowires can sustain ultralarge elastic strains of 4-7%. However, achieving and retaining elastic strains of such magnitude in kilogram-scale nanowires are challenging. Here, we find that under active load, ∼ 5.6% elastic strain can be achieved in Nb nanowires embedded in a metallic matrix deforming by detwinning. Moreover, large tensile (2.8%) and compressive (-2.4%) elastic strains can be retained in kilogram-scale Nb nanowires when the external load was fully removed, and adjustable in magnitude by processing control. It is then demonstrated that the retained tensile elastic strains of Nb nanowires can increase their superconducting transition temperature and critical magnetic field, in comparison with the unstrained original material. This study opens new avenues for retaining large and tunable elastic strains in great quantities of nanowires and elastic-strain-engineering at industrial scale. PMID:26745016

  13. Probabilistic elastic-plastic fracture analysis of circumferentially cracked pipes with finite-length surface flaws

    SciTech Connect

    Rahman, S.

    1996-12-01

    A new probabilistic model was developed for predicting elastic-plastic fracture response of circumferentially cracked pipes with finite-length, constant-depth, internal surface flaws subject to remote bending loads. It involves engineering estimation of energy release rate, J-tearing theory for characterizing ductile fracture, and standard methods of structural reliability theory. The underlying J-estimation model is based on deformation theory of plasticity, constitutive law characterized by power law model for stress-strain curve, and an equivalence criterion incorporating reduced thickness analogy for simulating system compliance due to the presence of a crack. New equations were developed to predict J-integral and were evaluated by comparing with available finite-element results from the current literature. Both analytical and simulation methods were formulated to determine the probabilistic characteristics of J. The same methods were used later to predict the probability of crack initiation and net-section collapse as a function of the applied load. Numerical examples are provided to illustrate the proposed methodology.

  14. Analytical solutions to general anti-plane shear problems in finite elasticity

    NASA Astrophysics Data System (ADS)

    Gao, David Yang

    2016-03-01

    This paper presents a pure complementary energy variational method for solving a general anti-plane shear problem in finite elasticity. Based on the canonical duality-triality theory developed by the author, the nonlinear/nonconvex partial differential equations for the large deformation problem are converted into an algebraic equation in dual space, which can, in principle, be solved to obtain a complete set of stress solutions. Therefore, a general analytical solution form of the deformation is obtained subjected to a compatibility condition. Applications are illustrated by examples with both convex and nonconvex stored strain energies governed by quadratic-exponential and power-law material models, respectively. Results show that the nonconvex variational problem could have multiple solutions at each material point, the complementary gap function and the triality theory can be used to identify both global and local extremal solutions, while the popular convexity conditions (including rank-one condition) provide mainly local minimal criteria and the Legendre-Hadamard condition (i.e., the so-called strong ellipticity condition) does not guarantee uniqueness of solutions. This paper demonstrates again that the pure complementary energy principle and the triality theory play important roles in finite deformation theory and nonconvex analysis.

  15. ISOFINEL: Isoparametric finite element code for elastic analysis of two-dimensional bodies

    NASA Technical Reports Server (NTRS)

    Marino, C.

    1975-01-01

    A formulation is presented for the development of a finite element program for the elastic analysis of two-dimensional bodies using the eight-node isoparametric quadrilateral. The program solves for both plane stress and plane strain problems. The finite element formulation based on the isoparametric displacement functions is presented. The program structure is given in the form of flow diagrams with descriptions of the numerical procedure used to obtain the element stiffness matrix, and the solution method employed to solve for nodal displacements. Three numerical examples (a plate under uniaxial tension, a plate under pure shear, and a beam under pure bending) are presented to illustrate the capability and limitations of the element implementation. The first problem is solved exactly by the element, as predicted by the form of its displacement functions. In the other two problems the accuracy of the solution is highly dependent upon the slenderness of the element, the number of elements in the map, and the numerical integration scheme used to build the element stiffness matrix.

  16. Breakdown of nonlinear elasticity in amorphous solids at finite temperatures

    NASA Astrophysics Data System (ADS)

    Procaccia, Itamar; Rainone, Corrado; Shor, Carmel A. B. Z.; Singh, Murari

    2016-06-01

    It is known [H. G. E. Hentschel et al., Phys. Rev. E 83, 061101 (2011), 10.1103/PhysRevE.83.061101] that amorphous solids at zero temperature do not possess a nonlinear elasticity theory: besides the shear modulus, which exists, none of the higher order coefficients exist in the thermodynamic limit. Here we show that the same phenomenon persists up to temperatures comparable to that of the glass transition. The zero-temperature mechanism due to the prevalence of dangerous plastic modes of the Hessian matrix is replaced by anomalous stress fluctuations that lead to the divergence of the variances of the higher order elastic coefficients. The conclusion is that in amorphous solids elasticity can never be decoupled from plasticity: the nonlinear response is very substantially plastic.

  17. Arterial elasticity imaging: comparison of finite-element analysis models with high-resolution ultrasound speckle tracking

    PubMed Central

    2010-01-01

    Background The nonlinear mechanical properties of internal organs and tissues may be measured with unparalleled precision using ultrasound imaging with phase-sensitive speckle tracking. The many potential applications of this important noninvasive diagnostic approach include measurement of arterial stiffness, which is associated with numerous major disease processes. The accuracy of previous ultrasound measurements of arterial stiffness and vascular elasticity has been limited by the relatively low strain of nonlinear structures under normal physiologic pressure and the measurement assumption that the effect of the surrounding tissue modulus might be ignored in both physiologic and pressure equalized conditions. Methods This study performed high-resolution ultrasound imaging of the brachial artery in a healthy adult subject under normal physiologic pressure and the use of external pressure (pressure equalization) to increase strain. These ultrasound results were compared to measurements of arterial strain as determined by finite-element analysis models with and without a surrounding tissue, which was represented by homogenous material with fixed elastic modulus. Results Use of the pressure equalization technique during imaging resulted in average strain values of 26% and 18% at the top and sides, respectively, compared to 5% and 2%, at the top and sides, respectively, under physiologic pressure. In the artery model that included surrounding tissue, strain was 19% and 16% under pressure equalization versus 9% and 13% at the top and sides, respectively, under physiologic pressure. The model without surrounding tissue had slightly higher levels of strain under physiologic pressure compared to the other model, but the resulting strain values under pressure equalization were > 60% and did not correspond to experimental values. Conclusions Since pressure equalization may increase the dynamic range of strain imaging, the effect of the surrounding tissue on strain should

  18. Finite Strain Viscoplastic Modeling of Polymer Glasses

    NASA Astrophysics Data System (ADS)

    van Breemen, L. C. A.; Govaert, L. E.; Meijer, H. E. H.

    2008-07-01

    There are several techniques to probe local mechanical properties of polymer systems. Two frequently used techniques are indentation and scratching, also known as sliding friction. The first is used to determine material parameters such as Young's modulus and yield strength, the later to resolve issues concerning friction and wear properties. Both techniques are based on contact of a specimen with a well-defined indentation/scratching geometry. If we take a closer look at an indentation experiment, an indenter is pressed into the material and a force, the so called normal force, and penetration into the surface are measured. For the scratching experiment an extra sliding dimension is added and besides the normal force and penetration depth, a lateral force and sliding distance are measured. The first step of a scratching experiment is indentation; this implies that before we can start with investigation of sliding phenomena, all the phenomena governing indentation have to be captured. For polymers this technique should be used with great care, this because of the strong non-linearity and rate dependence of polymer systems. To understand both contact phenomena a combination of experiments and numerical techniques are used. To comprehend macroscopic polymer deformation a polymers' intrinsic deformation should be captured accurately. This deformation behavior is used as input for our constitutive model and subsequently the model is used for finite element calculations.

  19. Dynamically strained ferroelastics: Statistical behavior in elastic and plastic regimes

    NASA Astrophysics Data System (ADS)

    Ding, X.; Lookman, T.; Zhao, Z.; Saxena, A.; Sun, J.; Salje, E. K. H.

    2013-03-01

    The dynamic evolution in ferroelastic crystals under external shear is explored by computer simulation of a two-dimensional model. The characteristic geometrical patterns obtained during shear deformation include dynamic tweed in the elastic regime as well as interpenetrating needle domains in the plastic regime. As a result, the statistics of jerk energy differ in the elastic and plastic regimes. In the elastic regime the distributions of jerk energy are sensitive to temperature and initial configurations. However, in the plastic regime the jerk distributions are rather robust and do not depend much on the details of the configurations, although the geometrical pattern formed after yield is strongly influenced by the elastic constants of the materials and the configurations we used. Specifically, for all geometrical configurations we studied, the energy distribution of jerks shows a power-law noise pattern P(E)˜E-(γ-1)(γ-1=1.3-2) at low temperatures and a Vogel-Fulcher distribution P(E) ˜ exp-(E/E0) at high temperatures. More complex behavior occurs at the crossover between these two regimes where our simulated jerk distributions are very well described by a generalized Poisson distributions P(E)˜E-(γ-1) exp-(E/E0)n with n = 0.4-0.5 and γ-1 ≈ 0 (Kohlrausch law). The geometrical mechanisms for the evolution of the ferroelastic microstructure under strain deformation remain similar in all thermal regimes, whereas their thermodynamic behavior differs dramatically: on heating, from power-law statistics via the Kohlrausch law to a Vogel-Fulcher law. There is hence no simple way to predict the local evolution of the twin microstructure from just the observed statistical behavior of a ferroelastic crystal. It is shown that the Poisson distribution is a convenient way to describe the crossover behavior contained in all the experimental data without recourse to specific scaling functions or temperature-dependent cutoff lengths.

  20. A hybrid-stress finite element approach for stress and vibration analysis in linear anisotropic elasticity

    NASA Technical Reports Server (NTRS)

    Oden, J. Tinsley; Fly, Gerald W.; Mahadevan, L.

    1987-01-01

    A hybrid stress finite element method is developed for accurate stress and vibration analysis of problems in linear anisotropic elasticity. A modified form of the Hellinger-Reissner principle is formulated for dynamic analysis and an algorithm for the determination of the anisotropic elastic and compliance constants from experimental data is developed. These schemes were implemented in a finite element program for static and dynamic analysis of linear anisotropic two dimensional elasticity problems. Specific numerical examples are considered to verify the accuracy of the hybrid stress approach and compare it with that of the standard displacement method, especially for highly anisotropic materials. It is that the hybrid stress approach gives much better results than the displacement method. Preliminary work on extensions of this method to three dimensional elasticity is discussed, and the stress shape functions necessary for this extension are included.

  1. Dependence of the elastic strain coefficient of copper on the pre-treatment

    NASA Technical Reports Server (NTRS)

    Kuntze, Wilhelm

    1950-01-01

    The effect of various pre-treatments on the elastic strain coefficient (alpha) (defined as the reciprocal of the modulus of elasticity E) (Epsilon) and on the mechanical hysteresis of copper has been investigated. Variables comprising the pre-treatments were pre-straining by stretching in a tensile testing machine and by drawing through a die, aging at room and elevated temperatures and annealing. The variation of the elastic strain coefficient with test stress was also investigated.

  2. The Influence of Elastic Strain on Catalytic Activity in the Hydrogen Evolution Reaction.

    PubMed

    Yan, Kai; Maark, Tuhina Adit; Khorshidi, Alireza; Sethuraman, Vijay A; Peterson, Andrew A; Guduru, Pradeep R

    2016-05-17

    Understanding the role of elastic strain in modifying catalytic reaction rates is crucial for catalyst design, but experimentally, this effect is often coupled with a ligand effect. To isolate the strain effect, we have investigated the influence of externally applied elastic strain on the catalytic activity of metal films in the hydrogen evolution reaction (HER). We show that elastic strain tunes the catalytic activity in a controlled and predictable way. Both theory and experiment show strain controls reactivity in a controlled manner consistent with the qualitative predictions of the HER volcano plot and the d-band theory: Ni and Pt's activities were accelerated by compression, while Cu's activity was accelerated by tension. By isolating the elastic strain effect from the ligand effect, this study provides a greater insight into the role of elastic strain in controlling electrocatalytic activity. PMID:27079940

  3. Biaxial load effects on the crack border elastic strain energy and strain energy rate

    NASA Technical Reports Server (NTRS)

    Eftis, J.; Subramonian, N.; Liebowitz, H.

    1977-01-01

    The validity of the singular solution (first term of a series representation) is investigated for the crack tip stress and displacement field in an infinite sheet with a flat line crack with biaxial loads applied to the outer boundaries. It is shown that if one retains the second contribution to the series approximations for stress and displacement in the calculation of the local elastic strain energy density and elastic strain energy rate in the crack border region, both these quantities have significant biaxial load dependency. The value of the J-integral does not depend on the presence of the second term of the series expansion for stress and displacement. Thus J(I) is insensitive to the presence of loads applied parallel to the plane of the crack.

  4. Hysteretic nonlinear elasticity of Berea sandstone at low-vibrational strain revealed by dynamic acousto-elastic testing

    NASA Astrophysics Data System (ADS)

    Renaud, G.; RivièRe, J.; Le Bas, P.-Y.; Johnson, P. A.

    2013-02-01

    Abstract Through changes in wave speed of ultrasonic pulses traversing the sample, we measure variations in the <span class="hlt">elasticity</span> of dry Berea sandstone as a function of the applied low-frequency (LF) axial <span class="hlt">strain</span> (varied from 10-7 to 10-5). The approach, termed dynamic acousto-<span class="hlt">elasticity</span>, is the dynamic analog of static acousto-<span class="hlt">elasticity</span> where the wave speed is measured as a function of the applied static load. Dynamic acousto-<span class="hlt">elasticity</span> uses low-frequency vibrational loading of smaller <span class="hlt">strain</span> amplitude, typically below 10-4, and it includes inertial effects. At <span class="hlt">strain</span> amplitudes around 10-6, compression and tension produce a material softening of the material. In contrast, a quasi-static compression inducing a <span class="hlt">strain</span> between 10-4 and 10-3 leads to a material stiffening. At 10-5 <span class="hlt">strain</span> amplitude, elaborate hysteretic signatures of modulus <span class="hlt">strain</span> are observed. The measurements provide the first direct experimental evidence of hysteretic nonlinear (wave amplitude dependent) <span class="hlt">elasticity</span> in a sandstone at low dynamic <span class="hlt">strains</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19840024803','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19840024803"><span id="translatedtitle"><span class="hlt">Finite</span> Element Prediction of Acoustic Scattering and Radiation from Submerged <span class="hlt">Elastic</span> Structures</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Everstine, G. C.; Henderson, F. M.; Lipman, R. R.</p> <p>1984-01-01</p> <p>A <span class="hlt">finite</span> element formulation is derived for the scattering and radiation of acoustic waves from submerged <span class="hlt">elastic</span> structures. The formulation uses as fundamental unknowns the displacement in the structure and a velocity potential in the field. Symmetric coefficient matrices result. The outer boundary of the fluid region is terminated with an approximate local wave-absorbing boundary condition which assumes that outgoing waves are locally planar. The <span class="hlt">finite</span> element model is capable of predicting only the near-field acoustic pressures. Far-field sound pressure levels may be determined by integrating the surface pressures and velocities over the wet boundary of the structure using the Helmholtz integral. Comparison of <span class="hlt">finite</span> element results with analytic results show excellent agreement. The coupled fluid-structure problem may be solved with general purpose <span class="hlt">finite</span> element codes by using an analogy between the equations of <span class="hlt">elasticity</span> and the wave equation of linear acoustics.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19910006285','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19910006285"><span id="translatedtitle">Estimation of the engineering <span class="hlt">elastic</span> constants of a directionally solidified superalloy for <span class="hlt">finite</span> element structural analysis</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Abdul-Aziz, Ali; Kalluri, Sreeramesh</p> <p>1991-01-01</p> <p>The temperature-dependent engineering <span class="hlt">elastic</span> constants of a directionally solidified nickel-base superalloy were estimated from the single-crystal <span class="hlt">elastic</span> constants of nickel and MAR-MOO2 superalloy by using Wells' method. In this method, the directionally solidified (columnar-grained) nickel-base superalloy was modeled as a transversely isotropic material, and the five independent <span class="hlt">elastic</span> constants of the transversely isotropic material were determined from the three independent <span class="hlt">elastic</span> constants of a cubic single crystal. Solidification for both the single crystals and the directionally solidified superalloy was assumed to be along the (001) direction. Temperature-dependent Young's moduli in longitudinal and transverse directions, shear moduli, and Poisson's ratios were tabulated for the directionally solidified nickel-base superalloy. These engineering <span class="hlt">elastic</span> constants could be used as input for performing <span class="hlt">finite</span> element structural analysis of directionally solidified turbine engine components.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015JAMTP..56..667B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015JAMTP..56..667B"><span id="translatedtitle">Dynamics of the antiplane <span class="hlt">strain</span> of a nonlinear <span class="hlt">elastic</span> body</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Bondar', B. D.</p> <p>2015-07-01</p> <p>The dynamic antiplane <span class="hlt">strain</span> of an incompressible cylindrical body is studied in a nonlinear formulation in actual variables. A representation of the velocity and acceleration through the displacement is obtained. The problem of the body deformation with account for geometrical and physical nonlinearities is reduced to an initial boundary-value problem for the displacement. The displacement found is used to determine the pressure and stresses. For a body with a quadratic <span class="hlt">elastic</span> potential, plane waves and self-similar motion are studied. The linear potential is used to investigate the deformation of a hollow elliptical cylinder for which analytical expressions for displacement and stresses are found and the external load is determined. It is shown that, due to the degeneration of the inner cavity of the body to a plane section, the load on the section remains limited.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2016CompM..57..277O&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2016CompM..57..277O&link_type=ABSTRACT"><span id="translatedtitle">A computational framework for polyconvex large <span class="hlt">strain</span> <span class="hlt">elasticity</span> for geometrically exact beam theory</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ortigosa, Rogelio; Gil, Antonio J.; Bonet, Javier; Hesch, Christian</p> <p>2016-02-01</p> <p>In this paper, a new computational framework is presented for the analysis of nonlinear beam <span class="hlt">finite</span> elements subjected to large <span class="hlt">strains</span>. Specifically, the methodology recently introduced in Bonet et al. (Comput Methods Appl Mech Eng 283:1061-1094, 2015) in the context of three dimensional polyconvex <span class="hlt">elasticity</span> is extended to the geometrically exact beam model of Simo (Comput Methods Appl Mech Eng 49:55-70, 1985), the starting point of so many other <span class="hlt">finite</span> element beam type formulations. This new variational framework can be viewed as a continuum degenerate formulation which, moreover, is enhanced by three key novelties. First, in order to facilitate the implementation of the sophisticated polyconvex constitutive laws particularly associated with beams undergoing large <span class="hlt">strains</span>, a novel tensor cross product algebra by Bonet et al. (Comput Methods Appl Mech Eng 283:1061-1094, 2015) is adopted, leading to an elegant and physically meaningful representation of an otherwise complex computational framework. Second, the paper shows how the novel algebra facilitates the re-expression of any invariant of the deformation gradient, its cofactor and its determinant in terms of the classical beam <span class="hlt">strain</span> measures. The latter being very useful whenever a classical beam implementation is preferred. This is particularised for the case of a Mooney-Rivlin model although the technique can be straightforwardly generalised to other more complex isotropic and anisotropic polyconvex models. Third, the connection between the two most accepted restrictions for the definition of constitutive models in three dimensional <span class="hlt">elasticity</span> and beams is shown, bridging the gap between the continuum and its degenerate beam description. This is carried out via a novel insightful representation of the tangent operator.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015CMT....27..739W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015CMT....27..739W"><span id="translatedtitle">Harmonic three-phase circular inclusions in <span class="hlt">finite</span> <span class="hlt">elasticity</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Wang, Xu; Schiavone, Peter</p> <p>2015-09-01</p> <p>We study the exterior stress field in a three-phase circular inclusion which is bonded to the surrounding matrix through an intermediate interphase layer. All three phases belong to a particular class of compressible hyperelastic materials of harmonic type. We focus on the design of a harmonic <span class="hlt">elastic</span> inclusion which by definition, does not disturb the sum of the normal stresses in the surrounding matrix. We show that in order to make the coated inclusion harmonic, certain inequalities concerning the material and geometric parameters of the three-phase composite must first be satisfied. The corresponding remote loading parameters can then be uniquely determined while keeping the associated phase angles arbitrary. Our results allow for both uniform and non-uniform remote loading. We show that the stress field inside the inclusion is uniform when the remote loading is uniform.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2015CompM..56...87H&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2015CompM..56...87H&link_type=ABSTRACT"><span id="translatedtitle">Tangential differential calculus and the <span class="hlt">finite</span> element modeling of a large deformation <span class="hlt">elastic</span> membrane problem</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Hansbo, Peter; Larson, Mats G.; Larsson, Fredrik</p> <p>2015-07-01</p> <p>We develop a <span class="hlt">finite</span> element method for a large deformation membrane <span class="hlt">elasticity</span> problem on meshed curved surfaces using a tangential differential calculus approach that avoids the use of classical differential geometric methods. The method is also applied to form finding problems.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/440691','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/440691"><span id="translatedtitle">A mixed <span class="hlt">finite</span> element domain decomposition method for nearly <span class="hlt">elastic</span> wave equations in the frequency domain</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Feng, Xiaobing</p> <p>1996-12-31</p> <p>A non-overlapping domain decomposition iterative method is proposed and analyzed for mixed <span class="hlt">finite</span> element methods for a sequence of noncoercive elliptic systems with radiation boundary conditions. These differential systems describe the motion of a nearly <span class="hlt">elastic</span> solid in the frequency domain. The convergence of the iterative procedure is demonstrated and the rate of convergence is derived for the case when the domain is decomposed into subdomains in which each subdomain consists of an individual element associated with the mixed <span class="hlt">finite</span> elements. The hybridization of mixed <span class="hlt">finite</span> element methods plays a important role in the construction of the discrete procedure.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/665159','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/665159"><span id="translatedtitle">On the measurement of <span class="hlt">strain</span> in coatings formed on a wrinkled <span class="hlt">elastic</span> substrate</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Gong, X.Y.; Clarke, D.R.</p> <p>1998-12-01</p> <p>Highly stressed coatings, such as those formed by oxidation can, on occasion, wrinkle. Such wrinkling has been suggested as a mode of deformation by which the overall <span class="hlt">strain</span> energy in a compressively stressed coating can be reduced. One of the consequences of wrinkling is that the <span class="hlt">strain</span> in the coating does not remain independent of position, but rather varies over the wavelength of the wrinkling. The <span class="hlt">strain</span> variation caused by sinusoidal wrinkling is calculated using <span class="hlt">finite</span>-element methods and the effects on both photostimulated Cr{sup 3+} luminescence piezospectroscopy measurements and X-ray measurements calculated. Wrinkling is shown to decease the <span class="hlt">elastic-strain</span>-energy density in the coating. A direct measure of the decrease in the shift in the R2 Cr{sup 3+} luminescence line and the X-ray diffraction peaks. Wrinkling of a compressive coating also causes stresses to be created perpendicular to the coating-substrate interface, tensile at the crests in the wrinkles, and compressive stress at the troughs.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19900019298','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19900019298"><span id="translatedtitle">A hybrid-stress <span class="hlt">finite</span> element for linear anisotropic <span class="hlt">elasticity</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Fly, Gerald W.; Oden, J. Tinsley; Pearson, Mark L.</p> <p>1988-01-01</p> <p>Standard assumed displacement <span class="hlt">finite</span> elements with anisotropic material properties perform poorly in complex stress fields such as combined bending and shear and combined bending and torsion. A set of three dimensional hybrid-stress brick elements were developed with fully anisotropic material properties. Both eight-node and twenty-node bricks were developed based on the symmetry group theory of Punch and Atluri. An eight-node brick was also developed using complete polynomials and stress basis functions and reducing the order of the resulting stress parameter matrix by applying equilibrium constraints and stress compatibility constraints. Here the stress compatibility constraints must be formulated assuming anisotropic material properties. The performance of these elements was examined in numerical examples covering a broad range of stress distributions. The stress predictions show significant improvement over the assumed displacement elements but the calculation time is increased.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012MSMSE..20c5016I','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012MSMSE..20c5016I"><span id="translatedtitle">Crystal plasticity based <span class="hlt">finite</span> element modelling of large <span class="hlt">strain</span> deformation in AM30 magnesium alloy</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Izadbakhsh, Adel; Inal, Kaan; Mishra, Raja K.</p> <p>2012-04-01</p> <p>In this paper, the <span class="hlt">finite</span> <span class="hlt">strain</span> plastic deformation of AM30 magnesium alloy has been simulated using the crystal plasticity <span class="hlt">finite</span> element method. The simulations have been carried out using a rate-dependent <span class="hlt">elastic</span>-viscoplastic crystal plasticity constitutive model implemented in a user defined material subroutine (UMAT) in the commercial software LS-DYNA. The plastic deformation mechanisms accounted for in the model are the slip systems in the matrix (parent grain), extension twinning systems and the slip systems inside the extension twinned regions. The parameters of the constitutive model have been calibrated using the experimental data. The calibrated model has then been used to predict the deformation of AM30 magnesium alloy in bending and simple shear. For the bending <span class="hlt">strain</span> path, the effects of texture on the <span class="hlt">strain</span> accommodated by the deformation mechanisms and bending moment have been investigated. For simple shear, the effects of texture on the relative activity of deformation mechanisms, shear stress and texture evolution have been investigated. Also, the effect of twinning on shear stress and texture evolution has been studied. The numerical analyses predicted a more uniform <span class="hlt">strain</span> distribution during bending and simple shear for rolled texture compared with extruded texture.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/20034181','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/20034181"><span id="translatedtitle">Experimental investigation of stress and <span class="hlt">strain</span> fields in a ductile matrix surrounding an <span class="hlt">elastic</span> inclusion</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Nugent, E.E.; Calhoun, R.B.; Mortensen, A.</p> <p>2000-04-19</p> <p>A method for measuring stress and <span class="hlt">strain</span> distributions within a ductile material deforming by dislocational slip is developed. The method exploits the transparency and room-temperature ductility of silver chloride, and combines the techniques of photoelasticity and marker tracking. This method is used to investigate the deformation of an elasto-plastic ductile matrix surrounding an isolated stiff fiber, the grain size of the material being slightly smaller than the fiber length. The data are compared to predictions of <span class="hlt">finite</span> element calculations which take the matrix to be an isotropic elasto-plastic von Mises continuum. It is found that this model does not fully capture all of the features of the experimental data. Data suggest that the cause for observed discrepancies is the strong influence exerted by grain boundaries and grain orientation on the distribution of stress and <span class="hlt">strain</span> within the matrix. A comparison is also made between the data and predictions of the Eshelby equivalent inclusion calculation, to show that a far higher level of discrepancy results than with the <span class="hlt">finite</span> element calculations; this is caused by the fact that the Eshelby equivalent inclusion calculation is essentially <span class="hlt">elastic</span> and thus allows significant stress concentrations.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4058877','PMC'); return false;" href="http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4058877"><span id="translatedtitle">Bulk metallic glass composite with good tensile ductility, high strength and large <span class="hlt">elastic</span> <span class="hlt">strain</span> limit</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Wu, Fu-Fa; Chan, K. C.; Jiang, Song-Shan; Chen, Shun-Hua; Wang, Gang</p> <p>2014-01-01</p> <p>Bulk metallic glasses exhibit high strength and large <span class="hlt">elastic</span> <span class="hlt">strain</span> limit but have no tensile ductility. However, bulk metallic glass composites reinforced by in-situ dendrites possess significantly improved toughness but at the expense of high strength and large <span class="hlt">elastic</span> <span class="hlt">strain</span> limit. Here, we report a bulk metallic glass composite with strong <span class="hlt">strain</span>-hardening capability and large <span class="hlt">elastic</span> <span class="hlt">strain</span> limit. It was found that, by plastic predeformation, the bulk metallic glass composite can exhibit both a large <span class="hlt">elastic</span> <span class="hlt">strain</span> limit and high strength under tension. These unique <span class="hlt">elastic</span> mechanical properties are attributed to the reversible B2↔B19′ phase transformation and the plastic-predeformation-induced complicated stress state in the metallic glass matrix and the second phase. These findings are significant for the design and application of bulk metallic glass composites with excellent mechanical properties. PMID:24931632</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3171755','PMC'); return false;" href="http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3171755"><span id="translatedtitle">A Micromechanics <span class="hlt">Finite-Strain</span> Constitutive Model of Fibrous Tissue</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Chen, Huan; Liu, Yi; Zhao, Xuefeng; Lanir, Yoram; Kassab, Ghassan S.</p> <p>2011-01-01</p> <p>Biological tissues have unique mechanical properties due to the wavy fibrous collagen and elastin microstructure. In inflation, a vessel easily distends under low pressure but becomes stiffer when the fibers are straightened to take up the load. The current microstructural models of blood vessels assume affine deformation; i.e., the deformation of each fiber is assumed to be identical to the macroscopic deformation of the tissue. This uniform-field (UF) assumption leads to the macroscopic (or effective) <span class="hlt">strain</span> energy of the tissue that is the volumetric sum of the contributions of the tissue components. Here, a micromechanics-based constitutive model of fibrous tissue is developed to remove the affine assumption and to take into consideration the heterogeneous interactions between the fibers and the ground substance. The development is based on the framework of a recently developed second-order homogenization theory, and takes into account the waviness, orientations, and spatial distribution of the fibers, as well as the material nonlinearity at <span class="hlt">finite-strain</span> deformation. In an illustrative simulation, the predictions of the macroscopic stress-<span class="hlt">strain</span> relation, and the statistical deformation of the fibers are compared to the UF model, as well as <span class="hlt">finite</span>-element (FE) simulation. Our predictions agree well with the FE results, while the UF predictions significantly overestimate. The effects of fiber distribution and waviness on the macroscopic stress-<span class="hlt">strain</span> relation are also investigated. The present mathematical model may serves as a foundation for native as well as for engineered tissues and biomaterials. PMID:21927506</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2011JMPSo..59.1823C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011JMPSo..59.1823C"><span id="translatedtitle">A micromechanics <span class="hlt">finite-strain</span> constitutive model of fibrous tissue</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Chen, Huan; Liu, Yi; Zhao, Xuefeng; Lanir, Yoram; Kassab, Ghassan S.</p> <p>2011-09-01</p> <p>Biological tissues have unique mechanical properties due to the wavy fibrous collagen and elastin microstructure. In inflation, a vessel easily distends under low pressure but becomes stiffer when the fibers are straightened to take up the load. The current microstructural models of blood vessels assume affine deformation, i.e., the deformation of each fiber is assumed to be identical to the macroscopic deformation of the tissue. This uniform-field (UF) assumption leads to the macroscopic (or effective) <span class="hlt">strain</span> energy of the tissue that is the volumetric sum of the contributions of the tissue components. Here, a micromechanics-based constitutive model of fibrous tissue is developed to remove the affine assumption and to take into consideration the heterogeneous interactions between the fibers and the ground substance. The development is based on the framework of a recently developed second-order homogenization theory, and takes into account the waviness, orientations and spatial distribution of the fibers, as well as the material nonlinearity at <span class="hlt">finite-strain</span> deformation. In an illustrative simulation, the predictions of the macroscopic stress-<span class="hlt">strain</span> relation and the statistical deformation of the fibers are compared to the UF model, as well as <span class="hlt">finite</span>-element (FE) simulation. Our predictions agree well with the FE results, while the UF predictions significantly overestimate. The effects of fiber distribution and waviness on the macroscopic stress-<span class="hlt">strain</span> relation are also investigated. The present mathematical model may serves as a foundation for native as well as for engineered tissues and biomaterials.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1995ApOpt..34.4993P&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1995ApOpt..34.4993P&link_type=ABSTRACT"><span id="translatedtitle"><span class="hlt">Elastic</span> transducers incorporating <span class="hlt">finite</span>-length optical paths</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Peters, Kara J.; Washabaugh, Peter D.</p> <p>1995-08-01</p> <p>Frequently, when designing a structure to incorporate integrated sensors, one sacrifices the stiffness of the system to improve sensitivity. However, the use of interferometric displacement sensors that tessellate throughout the volume of a structure has the potential to allow the precision and range of the component measurement to scale with the geometry of the device rather than the maximum <span class="hlt">strain</span> in the structure. The design of stiff structures that measure all six resultant-load components is described. In addition, an advanced torsion sensor and a linear acceleration transducer are also discussed. Finally, invariant paths are presented that allow the in situ integrity of a structural volume to be monitored with a single pair of displacement sensors.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2006IJCEM...7..331Z','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2006IJCEM...7..331Z"><span id="translatedtitle">On a New Concept and Foundations of an Arbitrary Reference Configuration (ARC) Theory and Formulation for Computational <span class="hlt">Finite</span> Deformation Applications—Part I: <span class="hlt">Elasticity</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Zhou, X.; Sha, D.; Tamma, K. K.</p> <p>2006-10-01</p> <p>Of interest here are the class of static/dynamic <span class="hlt">finite</span> deformation problems that arise in computational mechanics, and the question of the suitability in employing the total <span class="hlt">strain</span> measure for this class of problems is raised. An attempt to resolve the problem by proposing a new arbitrary reference configuration (ARC) framework is described in this exposition. The ARC framework consists of the ARC <span class="hlt">elasticity</span>, which bridges the Truesdell stress rate hypo-<span class="hlt">elasticity</span> and the St. Venant-Kirchhoff hyperelasticity, and the ARC Lagrangian formulation, which bridges the updated Lagrangian formulation and the total Lagrangian formulation. The ARC framework serves as a generalized computational framework to handle both the computational infinitesimal and the <span class="hlt">finite</span> deformation/<span class="hlt">strain</span> deformation applications in a consistent and unified manner. In part II of the paper [1], we further extend the ARC framework to elasto-plasticity.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_3");'>3</a></li> <li><a href="#" onclick='return showDiv("page_4");'>4</a></li> <li class="active"><span>5</span></li> <li><a href="#" onclick='return showDiv("page_6");'>6</a></li> <li><a href="#" onclick='return showDiv("page_7");'>7</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_5 --> <div id="page_6" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_4");'>4</a></li> <li><a href="#" onclick='return showDiv("page_5");'>5</a></li> <li class="active"><span>6</span></li> <li><a href="#" onclick='return showDiv("page_7");'>7</a></li> <li><a href="#" onclick='return showDiv("page_8");'>8</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="101"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFMMR21A2608Y','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFMMR21A2608Y"><span id="translatedtitle">Three-dimensional analysis of pore effect on composite <span class="hlt">elasticity</span> by means of <span class="hlt">finite</span> element method</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Yoneda, A.</p> <p>2015-12-01</p> <p>A three-dimensional buffer-layer <span class="hlt">finite</span> element method (FEM) model was developed to investigate the porosity effect on macroscopic <span class="hlt">elasticity</span>. Using the three-dimensional model, the effect of pores on bulk effective <span class="hlt">elastic</span> properties were systematically analyzed by changing the degree of porosity, the aspect ratio of the ellipsoidal pore, and the <span class="hlt">elasticity</span> of the material. The present results in 3D space was compared with the previous ones in 2D space. Derivatives of normalized <span class="hlt">elastic</span> stiffness constants with respect to needle-type porosity are integers, if the Poisson ratio of a matrix material is zero; those derivatives of normalized stiffness <span class="hlt">elastic</span> constants for C33, C44, C11, and C66 converge to -1, -2, -3, and -4, respectively, at the corresponding condition. We proposed a criterion of R <~1/3, where the mutual interaction between pores becomes negligible for macroscopic composite <span class="hlt">elasticity</span>. These derivatives are nearly constant below 5% porosity in the case of spherical pore, suggesting that the interaction between neighboring pores is insignificant if the representative size of the pore is less than one-third of the mean distance between neighboring pores. The relations we obtained in this work were successfully applied to invert bulk modulus and rigidity of Cmcm-CaIrO3 as a case study; the performance of the inverting scheme was confirmed through this assessment. Thus the present scheme is applicable to predict macroscopic <span class="hlt">elasticity</span> of porous object as well.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015JMPSo..84..293N','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015JMPSo..84..293N"><span id="translatedtitle">A theory of <span class="hlt">finite</span> <span class="hlt">strain</span> magneto-poromechanics</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Nedjar, B.</p> <p>2015-11-01</p> <p>The main purpose of this paper is the multi-physics modeling of magnetically sensitive porous materials. We develop for this a magneto-poromechanics formulation suitable for the description of such a coupling. More specifically, we show how the current state of the art in the mathematical modeling of magneto-mechanics can easily be integrated within the unified framework of continuum thermodynamics of open media, which is crucial in setting the convenient forms of the state laws to fully characterize the behavior of porous materials. Moreover, due to the soft nature of these materials in general, the formulation is directly developed within the <span class="hlt">finite</span> <span class="hlt">strain</span> range. In a next step, a modeling example is proposed and detailed for the particular case of magneto-active foams with reversible deformations. In particular, due to their potentially high change in porosity, a nonlinear porosity law recently proposed is used to correctly describe the fluid flow through the interconnected pores when the solid skeleton is <span class="hlt">finitely</span> <span class="hlt">strained</span> causing fluid release or reabsorption. From the numerical point of view, the variational formulation together with an algorithmic design is described for an easy implementation within the context of the <span class="hlt">finite</span> element method. Finally, a set of numerical simulations is presented to illustrate the effectiveness of the proposed framework.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/319661','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/319661"><span id="translatedtitle">Simple structures test for <span class="hlt">elastic</span>-plastic <span class="hlt">strain</span> acceptance criterion validation</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Trimble, T.F.; Krech, G.R.</p> <p>1997-11-01</p> <p>A Simple Structures Test Program was performed where several cantilevered beam and fixed-end beam test specimens (fabricated from HY-80 steel) were subjected to a series of analytically predetermined rapidly applied transient dynamic input loads. The primary objective of the test program was to obtain dynamic nonlinear response for simple structures subjected to these load inputs. Data derived from these tests was subsequently used to correlate to analysis predictions to assess the capability to analytically predict <span class="hlt">elastic</span>-plastic nonlinear material behavior in structures using typical time-dependent (transient) design methods and the ABAQUS <span class="hlt">finite</span> element analysis code. The installation of a significant amount of instrumentation on these specimens and post-test measurements enabled the monitoring and recording of <span class="hlt">strain</span> levels, displacements, accelerations, and permanent set. An assessment of modeling parameters such as the element type and mesh refinement was made using these test results. In addition, currently available material models and the incremental time step procedure used in the transient analyses were evaluated. Comparison of test data to analysis results shows that displacements, accelerations, and peak <span class="hlt">strain</span> can be predicted with a reasonable level of accuracy using detailed solid models of the tested specimens. Permanent set is overpredicted by a factor of approximately two. However, the accuracy of the prediction of permanent set is being enhanced by updating material modeling in the ABAQUS code to account for effects of <span class="hlt">strain</span> reversal in oscillatory behavior of dynamically loaded specimens.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014APS..DFD.R8005T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014APS..DFD.R8005T"><span id="translatedtitle">Mechanisms of <span class="hlt">elastic</span> enhancement and hindrance for <span class="hlt">finite</span> length undulatory swimmers in viscoelastic fluids</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Thomases, Becca; Guy, Robert</p> <p>2014-11-01</p> <p>A computational model of <span class="hlt">finite</span>-length undulatory swimmers is used to examine the physical origin of the effect of <span class="hlt">elasticity</span> on swimming speed. We explore two distinct target swimming strokes, one derived from the motion of C. elegans, with large head undulations, and a contrasting stroke with large tail undulations. We show that both favorable stroke asymmetry and swimmer <span class="hlt">elasticity</span> contribute to a speed-up, but a substantial boost results only when these two effects work together. We reproduce conflicting results from the literature simply by changing relevant physical parameters.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014PhRvL.113i8102T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014PhRvL.113i8102T"><span id="translatedtitle">Mechanisms of <span class="hlt">Elastic</span> Enhancement and Hindrance for <span class="hlt">Finite</span>-Length Undulatory Swimmers in Viscoelastic Fluids</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Thomases, Becca; Guy, Robert D.</p> <p>2014-08-01</p> <p>A computational model of <span class="hlt">finite</span>-length undulatory swimmers is used to examine the physical origin of the effect of <span class="hlt">elasticity</span> on swimming speed. We explore two distinct target swimming strokes: one derived from the motion of Caenorhabditis elegans, with large head undulations, and a contrasting stroke with large tail undulations. We show that both favorable stroke asymmetry and swimmer <span class="hlt">elasticity</span> contribute to a speed-up, but a substantial boost results only when these two effects work together. We reproduce conflicting results from the literature simply by changing relevant physical parameters.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016CMT....28..477N','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016CMT....28..477N"><span id="translatedtitle">The exponentiated Hencky-logarithmic <span class="hlt">strain</span> energy: part III—coupling with idealized multiplicative isotropic <span class="hlt">finite</span> <span class="hlt">strain</span> plasticity</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Neff, Patrizio; Ghiba, Ionel-Dumitrel</p> <p>2016-03-01</p> <p>We investigate an immediate application in <span class="hlt">finite</span> <span class="hlt">strain</span> multiplicative plasticity of the family of isotropic volumetric-isochoric decoupled <span class="hlt">strain</span> energies F mapsto W_eH(F):= widehat{W}_eH(U) := μ/k e^{k | dev_n log {U}|^2}+κ/2 {widehat{k}} e^{widehat{k} [ tr(log U)]^2}&quad if& det F > 0, + ∞ & quad if & det F ≤ 0, based on the Hencky-logarithmic (true, natural) <span class="hlt">strain</span> tensor {log U} . Here, {μ > 0} is the infinitesimal shear modulus, {κ=2 μ+3λ/3 > 0} is the infinitesimal bulk modulus with λ the first Lamé constant, {k,widehat{k}} are additional dimensionless material parameters, {F=nabla \\varphi} is the gradient of deformation, {U=√{F^T F}} is the right stretch tensor, and dev n {log {U} =log {U}-1/n tr(log {U})\\cdot{1}} is the deviatoric part of the <span class="hlt">strain</span> tensor {log U} . Based on the multiplicative decomposition {F=F_e F_p} , we couple these energies with some isotropic elasto-plastic flow rules {F_p {dt}/[F_p^{-1}]in-partial χ(dev_3 Σe)} defined in the plastic distortion F p , where {partial χ} is the subdifferential of the indicator function {χ} of the convex <span class="hlt">elastic</span> domain {E_e({Σe},1/3{σ}_{y}^2)} in the mixed-variant {Σe} -stress space, {Σe=F_e^T D_{F_e}W_iso(F_e)} , and {W_iso(F_e)} represents the isochoric part of the energy. While {W_eH} may loose ellipticity, we show that loss of ellipticity is effectively prevented by the coupling with plasticity, since the ellipticity domain of {W_eH} on the one hand and the <span class="hlt">elastic</span> domain in {Σe} -stress space on the other hand are closely related. Thus, the new formulation remains elliptic in <span class="hlt">elastic</span> unloading at any given plastic predeformation. In addition, in this domain, the true stress-true <span class="hlt">strain</span> relation remains monotone, as observed in experiments.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/837670','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/837670"><span id="translatedtitle">Probing the <span class="hlt">Elastic</span>-Plastic, Time-Dependant Response of Test Fasteners using <span class="hlt">Finite</span> Element Analysis (FEA)</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>ML Renauld; H Lien</p> <p>2004-12-13</p> <p>The evolution of global and local stress/<span class="hlt">strain</span> conditions in test fasteners under test conditions is investigated using <span class="hlt">elastic</span>-plastic, time-dependent <span class="hlt">finite</span> element analyses (FEA). For <span class="hlt">elastic</span>-plastic response, tensile data from multiple specimens, material heats and test temperatures are integrated into a single, normalized flow curve from which temperature dependency is extracted. A primary creep model is calibrated with specimen- and fastener-based thermal relaxation data generated under a range of times, temperatures, stress levels and environments. These material inputs are used in analytical simulations of experimental test conditions for several types of fasteners. These fastener models are constructed with automated routines and contact conditions prescribed at all potentially mating surfaces. Thermal or mechanical room temperature pre-loading, as appropriate for a given fastener, is followed by a temperature ramp and a dwell time at constant temperature. While the amount of thermal stress relaxation is limited for the conditions modeled, local stress states are highly dependent upon geometry (thread root radius, for example), pre-loading history and thermal expansion differences between the test fastener and test fixture. Benefits of this FE approach over an <span class="hlt">elastic</span> methodology for stress calculation will be illustrated with correlations of Stress Corrosion Cracking (SCC) initiation time and crack orientations in stress concentrations.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AGUFM.V23D4825A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AGUFM.V23D4825A"><span id="translatedtitle">Numerical solution of an <span class="hlt">elastic</span> and viscoelastic gravitational models by the <span class="hlt">finite</span> element method</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Arjona Almodóvar, A.; Chacón Rebollo, T.; Gómez Marmol, M.</p> <p>2014-12-01</p> <p>Volcanic areas present a lower effective viscosity than usually in the Earth's crust. Both the <span class="hlt">elastic</span>-gravitational and the viscoelastic-gravitational models allow the computation of gravity, deformation, and gravitational potential changes in order to investigate crustal deformations of Earth (see for instance Battaglia & Segall, 2004; Fernández et al. 1999, 2001; Rundle 1980 and 1983). These models can be represented by a coupled system of linear parabolic (for the <span class="hlt">elastic</span> deformations), hyperbolic (for the viscoelastic deformations) and elliptic partial differential equations (for gravitational potential changes) (see for instance Arjona et al. 2008 and 2010). The existence and uniqueness of weak solutions for both the <span class="hlt">elastic</span>-gravitational and viscoelastic-gravitational problem was demonstrated in Arjona et al. (2008 and 2014). The stabilization to solutions of the associated stationary system was proved in Arjona and Díaz (2007). Here we consider the internal source as response to the effect of a pressurized magma reservoir into a multilayered, <span class="hlt">elastic</span>-gravitational and viscoelastic-gravitational earth model. We introduce the numerical analysis of a simplified steady <span class="hlt">elastic</span>-gravitational model, solved by means of the <span class="hlt">finite</span> element method. We also present some numerical tests in realistic situations that confirm the predictions of theoretical order of convergence. Finally, we describe the methodology for both the <span class="hlt">elastic</span>-gravitational and the viscoelastic-gravitational models using 2D and 3D test examples performed with FreeFEM++.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/22257086','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/22257086"><span id="translatedtitle">On the origin of <span class="hlt">elastic</span> <span class="hlt">strain</span> limit of bulk metallic glasses</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Ding, J. Ma, E.; Cheng, Y. Q.</p> <p>2014-01-06</p> <p>All bulk metallic glasses exhibit a large and almost universal <span class="hlt">elastic</span> <span class="hlt">strain</span> limit. Here, we show that the magnitude of the yield <span class="hlt">strain</span> of the glass state can be quantitatively derived from a characteristic property of the flow state typical in running shear bands (the root cause of yielding). The <span class="hlt">strain</span> in the shear flow is mostly plastic, but associated with it there is an effective <span class="hlt">elastic</span> atomic <span class="hlt">strain</span>. The latter is almost identical for very different model systems in our molecular dynamics simulations, such that the corresponding yield <span class="hlt">strain</span> is universal at any given homologous temperature.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19770021577','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19770021577"><span id="translatedtitle">Three-dimensional <span class="hlt">elastic</span> stress and displacement analysis of <span class="hlt">finite</span> geometry solids containing cracks</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Kring, J.; Gyekenyesi, J.; Mendelson, A.</p> <p>1977-01-01</p> <p>The line method of analysis is applied to the Navier-Cauchy equations of <span class="hlt">elastic</span> equilibrium to calculate the displacement fields in <span class="hlt">finite</span> geometry bars containing central, surface, and double-edge cracks under extensionally applied uniform loading. The application of this method to these equations leads to coupled sets of simultaneous ordinary differential equations whose solutions are obtained along sets of lines in a discretized region. Normal stresses and the stress intensity factor variation along the crack periphery are calculated using the obtained displacement field. The reported results demonstrate the usefulness of this method in calculating stress intensity factors for commonly encountered crack geometries in <span class="hlt">finite</span> solids.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19730016164','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19730016164"><span id="translatedtitle">Three-dimensional <span class="hlt">elastic</span> stress and displacement analysis of <span class="hlt">finite</span> circular geometry solids containing cracks</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Gyekenyesi, J. P.; Mendelson, A.; Kring, J.</p> <p>1973-01-01</p> <p>A seminumerical method is presented for solving a set of coupled partial differential equations subject to mixed and coupled boundary conditions. The use of this method is illustrated by obtaining solutions for two circular geometry and mixed boundary value problems in three-dimensional <span class="hlt">elasticity</span>. Stress and displacement distributions are calculated in an axisymmetric, circular bar of <span class="hlt">finite</span> dimensions containing a penny-shaped crack. Approximate results for an annular plate containing internal surface cracks are also presented.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/27480733','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/27480733"><span id="translatedtitle">A multiscale modelling of bone ultrastructure <span class="hlt">elastic</span> proprieties using <span class="hlt">finite</span> elements simulation and neural network method.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Barkaoui, Abdelwahed; Tlili, Brahim; Vercher-Martínez, Ana; Hambli, Ridha</p> <p>2016-10-01</p> <p>Bone is a living material with a complex hierarchical structure which entails exceptional mechanical properties, including high fracture toughness, specific stiffness and strength. Bone tissue is essentially composed by two phases distributed in approximately 30-70%: an organic phase (mainly type I collagen and cells) and an inorganic phase (hydroxyapatite-HA-and water). The nanostructure of bone can be represented throughout three scale levels where different repetitive structural units or building blocks are found: at the first level, collagen molecules are arranged in a pentameric structure where mineral crystals grow in specific sites. This primary bone structure constitutes the mineralized collagen microfibril. A structural organization of inter-digitating microfibrils forms the mineralized collagen fibril which represents the second scale level. The third scale level corresponds to the mineralized collagen fibre which is composed by the binding of fibrils. The hierarchical nature of the bone tissue is largely responsible of their significant mechanical properties; consequently, this is a current outstanding research topic. Scarce works in literature correlates the <span class="hlt">elastic</span> properties in the three scale levels at the bone nanoscale. The main goal of this work is to estimate the <span class="hlt">elastic</span> properties of the bone tissue in a multiscale approach including a sensitivity analysis of the <span class="hlt">elastic</span> behaviour at each length scale. This proposal is achieved by means of a novel hybrid multiscale modelling that involves neural network (NN) computations and <span class="hlt">finite</span> elements method (FEM) analysis. The <span class="hlt">elastic</span> properties are estimated using a neural network simulation that previously has been trained with the database results of the <span class="hlt">finite</span> element models. In the results of this work, parametric analysis and averaged <span class="hlt">elastic</span> constants for each length scale are provided. Likewise, the influence of the <span class="hlt">elastic</span> constants of the tissue constituents is also depicted. Results highlight</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016GeoJI.204..780J','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016GeoJI.204..780J"><span id="translatedtitle">Dramatic effect of <span class="hlt">elasticity</span> on thermal softening and <span class="hlt">strain</span> localization during lithospheric shortening</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Jaquet, Yoann; Duretz, Thibault; Schmalholz, Stefan M.</p> <p>2016-02-01</p> <p>We present two-dimensional numerical simulations for shortening a viscoelastoplastic lithosphere to quantify the impact of <span class="hlt">elasticity</span> on <span class="hlt">strain</span> localization due to thermal softening. The model conserves energy and mechanical work is converted into heat or stored as <span class="hlt">elastic</span> <span class="hlt">strain</span> energy. For a shear modulus G = 1010 Pa, a prominent lithospheric shear zone forms and <span class="hlt">elastic</span> energy release increases the localization intensity (<span class="hlt">strain</span> rate amplification). For G = 5 × 1010 Pa shear zones still form but deformation is less localized. For G = 1012 Pa, the lithosphere behaves effectively viscoplastic and no shear zones form during homogeneous thickening. Maximal shearing-related increase of surface heat flux is 15-25 mW m-2 and of temperature at lower crustal depth is ˜150 °C, whereby these peak values are transient (0.1-1 My). <span class="hlt">Elasticity</span> and related energy release can significantly contribute to <span class="hlt">strain</span> localization and plate-like behaviour of the lithosphere required for plate tectonics.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2006PhDT........42N','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2006PhDT........42N"><span id="translatedtitle">Inverse <span class="hlt">finite</span> element methods for extracting <span class="hlt">elastic</span>-poroviscoelastic properties of cartilage and other soft tissues from indentation</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Namani, Ravi</p> <p></p> <p>Mechanical properties are essential for understanding diseases that afflict various soft tissues, such as osteoarthritic cartilage and hypertension which alters cardiovascular arteries. Although the linear <span class="hlt">elastic</span> modulus is routinely measured for hard materials, standard methods are not available for extracting the nonlinear <span class="hlt">elastic</span>, linear <span class="hlt">elastic</span> and time-dependent properties of soft tissues. Consequently, the focus of this work is to develop indentation methods for soft biological tissues; since analytical solutions are not available for the general context, <span class="hlt">finite</span> element simulations are used. First, parametric studies of <span class="hlt">finite</span> indentation of hyperelastic layers are performed to examine if indentation has the potential to identify nonlinear <span class="hlt">elastic</span> behavior. To answer this, spherical, flat-ended conical and cylindrical tips are examined and the influence of thickness is exploited. Also the influence of the specimen/substrate boundary condition (slip or non-slip) is clarified. Second, a new inverse method---the hyperelastic extraction algorithm (HPE)---was developed to extract two nonlinear <span class="hlt">elastic</span> parameters from the indentation force-depth data, which is the basic measurement in an indentation test. The accuracy of the extracted parameters and the influence of noise in measurements on this accuracy were obtained. This showed that the standard Berkovitch tip could only extract one parameter with sufficient accuracy, since the indentation force-depth curve has limited sensitivity to both nonlinear <span class="hlt">elastic</span> parameters. Third, indentation methods for testing tissues from small animals were explored. New methods for flat-ended conical tips are derived. These account for practical test issues like the difficulty in locating the surface or soft specimens. Also, <span class="hlt">finite</span> element simulations are explored to elucidate the influence of specimen curvature on the indentation force-depth curve. Fourth, the influence of inhomogeneity and material anisotropy on the extracted</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/22230856','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/22230856"><span id="translatedtitle">Variational integrators for the dynamics of thermo-<span class="hlt">elastic</span> solids with <span class="hlt">finite</span> speed thermal waves</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Mata, Pablo</p> <p>2014-01-15</p> <p>This paper formulates variational integrators for <span class="hlt">finite</span> element discretizations of deformable bodies with heat conduction in the form of <span class="hlt">finite</span> speed thermal waves. The cornerstone of the construction consists in taking advantage of the fact that the Green–Naghdi theory of type II for thermo-<span class="hlt">elastic</span> solids has a Hamiltonian structure. Thus, standard techniques to construct variational integrators can be applied to <span class="hlt">finite</span> element discretizations of the problem. The resulting discrete-in-time trajectories are then consistent with the laws of thermodynamics for these systems: for an isolated system, they exactly conserve the total entropy, and nearly exactly conserve the total energy over exponentially long periods of time. Moreover, linear and angular momenta are also exactly conserved whenever the exact system does. For definiteness, we construct an explicit second-order accurate algorithm for affine tetrahedral elements in two and three dimensions, and demonstrate its performance with numerical examples.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013PMB....58.8457B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013PMB....58.8457B"><span id="translatedtitle">A direct vulnerable atherosclerotic plaque <span class="hlt">elasticity</span> reconstruction method based on an original material-<span class="hlt">finite</span> element formulation: theoretical framework</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Bouvier, Adeline; Deleaval, Flavien; Doyley, Marvin M.; Yazdani, Saami K.; Finet, Gérard; Le Floc'h, Simon; Cloutier, Guy; Pettigrew, Roderic I.; Ohayon, Jacques</p> <p>2013-12-01</p> <p>The peak cap stress (PCS) amplitude is recognized as a biomechanical predictor of vulnerable plaque (VP) rupture. However, quantifying PCS in vivo remains a challenge since the stress depends on the plaque mechanical properties. In response, an iterative material <span class="hlt">finite</span> element (FE) <span class="hlt">elasticity</span> reconstruction method using <span class="hlt">strain</span> measurements has been implemented for the solution of these inverse problems. Although this approach could resolve the mechanical characterization of VPs, it suffers from major limitations since (i) it is not adapted to characterize VPs exhibiting high material discontinuities between inclusions, and (ii) does not permit real time <span class="hlt">elasticity</span> reconstruction for clinical use. The present theoretical study was therefore designed to develop a direct material-FE algorithm for <span class="hlt">elasticity</span> reconstruction problems which accounts for material heterogeneities. We originally modified and adapted the extended FE method (Xfem), used mainly in crack analysis, to model material heterogeneities. This new algorithm was successfully applied to six coronary lesions of patients imaged in vivo with intravascular ultrasound. The results demonstrated that the mean relative absolute errors of the reconstructed Young's moduli obtained for the arterial wall, fibrosis, necrotic core, and calcified regions of the VPs decreased from 95.3±15.56%, 98.85±72.42%, 103.29±111.86% and 95.3±10.49%, respectively, to values smaller than 2.6 × 10-8±5.7 × 10-8% (i.e. close to the exact solutions) when including modified-Xfem method into our direct <span class="hlt">elasticity</span> reconstruction method.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2016CompM..57..193K&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2016CompM..57..193K&link_type=ABSTRACT"><span id="translatedtitle">Mixed boundary conditions for FFT-based homogenization at <span class="hlt">finite</span> <span class="hlt">strains</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kabel, Matthias; Fliegener, Sascha; Schneider, Matti</p> <p>2016-02-01</p> <p>In this article we introduce a Lippmann-Schwinger formulation for the unit cell problem of periodic homogenization of <span class="hlt">elasticity</span> at <span class="hlt">finite</span> <span class="hlt">strains</span> incorporating arbitrary mixed boundary conditions. Such problems occur frequently, for instance when validating computational results with tensile tests, where the deformation gradient in loading direction is fixed, as is the stress in the corresponding orthogonal plane. Previous Lippmann-Schwinger formulations involving mixed boundary can only describe tensile tests where the vector of applied force is proportional to a coordinate direction. Utilizing suitable orthogonal projectors we develop a Lippmann-Schwinger framework for arbitrary mixed boundary conditions. The resulting fixed point and Newton-Krylov algorithms preserve the positive characteristics of existing FFT-algorithms. We demonstrate the power of the proposed methods with a series of numerical examples, including continuous fiber reinforced laminates and a complex nonwoven structure of a long fiber reinforced thermoplastic, resulting in a speed-up of some computations by a factor of 1000.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014JMPSo..68..161P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014JMPSo..68..161P"><span id="translatedtitle">Singularity-free dislocation dynamics with <span class="hlt">strain</span> gradient <span class="hlt">elasticity</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Po, Giacomo; Lazar, Markus; Seif, Dariush; Ghoniem, Nasr</p> <p>2014-08-01</p> <p>The singular nature of the <span class="hlt">elastic</span> fields produced by dislocations presents conceptual challenges and computational difficulties in the implementation of discrete dislocation-based models of plasticity. In the context of classical <span class="hlt">elasticity</span>, attempts to regularize the <span class="hlt">elastic</span> fields of discrete dislocations encounter intrinsic difficulties. On the other hand, in gradient <span class="hlt">elasticity</span>, the issue of singularity can be removed at the outset and smooth <span class="hlt">elastic</span> fields of dislocations are available. In this work we consider theoretical and numerical aspects of the non-singular theory of discrete dislocation loops in gradient <span class="hlt">elasticity</span> of Helmholtz type, with interest in its applications to three dimensional dislocation dynamics (DD) simulations. The gradient solution is developed and compared to its singular and non-singular counterparts in classical <span class="hlt">elasticity</span> using the unified framework of eigenstrain theory. The fundamental equations of curved dislocation theory are given as non-singular line integrals suitable for numerical implementation using fast one-dimensional quadrature. These include expressions for the interaction energy between two dislocation loops and the line integral form of the generalized solid angle associated with dislocations having a spread core. The single characteristic length scale of Helmholtz <span class="hlt">elasticity</span> is determined from independent molecular statics (MS) calculations. The gradient solution is implemented numerically within our variational formulation of DD, with several examples illustrating the viability of the non-singular solution. The displacement field around a dislocation loop is shown to be smooth, and the loop self-energy non-divergent, as expected from atomic configurations of crystalline materials. The loop nucleation energy barrier and its dependence on the applied shear stress are computed and shown to be in good agreement with atomistic calculations. DD simulations of Lome-Cottrell junctions in Al show that the strength of the</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/18996702','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/18996702"><span id="translatedtitle"><span class="hlt">Finite</span>-element study of <span class="hlt">strain</span> field in <span class="hlt">strained</span>-Si MOSFET.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Liu, H H; Duan, X F; Xu, Q X</p> <p>2009-02-01</p> <p>The <span class="hlt">strain</span> field in the channel of a p-type metal-oxide-semiconductor field effect transistor fabricated by integrating Ge pre-amorphization implantation for source/drain regions is evaluated using a <span class="hlt">finite</span>-element method combining with large angle convergent-beam electron diffraction (LACBED). The <span class="hlt">finite</span>-element calculation shows that there is a very large compressive <span class="hlt">strain</span> in the top layer of the channel region caused by a low dose of Ge ion implantation in the source and drain extension regions. Moreover, a transition region is formed in the bottom of the channel region and the top of the Si substrate. These calculation results are in good agreement with the LACBED experiments. PMID:18996702</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/1177388','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/1177388"><span id="translatedtitle">An <span class="hlt">Elastic</span> Plastic Contact Model with <span class="hlt">Strain</span> Hardening for the LAMMPS Granular Package</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Kuhr, Bryan; Brake, Matthew Robert; Lechman, Jeremy B.</p> <p>2015-03-01</p> <p>The following details the implementation of an analytical <span class="hlt">elastic</span> plastic contact model with <span class="hlt">strain</span> hardening for normal im pacts into the LAMMPS granular package. The model assumes that, upon impact, the co llision has a period of <span class="hlt">elastic</span> loading followed by a period of mixed <span class="hlt">elastic</span> plas tic loading, with contributions to each mechanism estimated by a hyperbolic seca nt weight function. This function is implemented in the LAMMPS source code as the pair style gran/ep/history. Preliminary tests, simulating the pouring of pure nickel spheres, showed the <span class="hlt">elastic</span>/plastic model took 1.66x as long as similar runs using gran/hertz/history.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_4");'>4</a></li> <li><a href="#" onclick='return showDiv("page_5");'>5</a></li> <li class="active"><span>6</span></li> <li><a href="#" onclick='return showDiv("page_7");'>7</a></li> <li><a href="#" onclick='return showDiv("page_8");'>8</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_6 --> <div id="page_7" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_5");'>5</a></li> <li><a href="#" onclick='return showDiv("page_6");'>6</a></li> <li class="active"><span>7</span></li> <li><a href="#" onclick='return showDiv("page_8");'>8</a></li> <li><a href="#" onclick='return showDiv("page_9");'>9</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="121"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013AGUFMMR13A2246R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013AGUFMMR13A2246R"><span id="translatedtitle">On the influence of <span class="hlt">strain</span> rate in acousto-<span class="hlt">elasticity</span> : experimental results for Berea sandstone</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Riviere, J. V.; Candela, T.; Scuderi, M.; Marone, C.; Guyer, R. A.; Johnson, P. A.</p> <p>2013-12-01</p> <p><span class="hlt">Elastic</span> nonlinear effects are pervasive in the Earth, including during strong ground motion, tidal forcing and earthquake slip processes. We study <span class="hlt">elastic</span> nonlinear effects in the laboratory with the goal of developing new methods to probe <span class="hlt">elastic</span> changes in the Earth, and to characterize and understand their origins. Here we report on nonlinear, frequency dispersion effects by applying a method termed dynamic acousto-<span class="hlt">elasticity</span> (DAE), analogous to quasi-static acousto-<span class="hlt">elasticity</span>. DAE allows one to obtain the <span class="hlt">elastic</span> behavior over the entire dynamic cycle, detailing the full nonlinear behavior under tension and compression, including hysteresis and memory effects. We perform DAE on samples of Berea sandstone subject to 0.5 MPa uniaxial and biaxial loading conditions with oscillating loads at frequencies from 0.001 to 10 Hz and amplitudes of a few 100 kPa. We compare results to DAE measurements made in the kHz range. We observe that the average decrease in modulus due to nonlinear material softening increases with frequency, suggesting a frequency and/or a <span class="hlt">strain</span> rate dependence. Previous quasi-static measurements (Claytor et al., GRL 2009) show that stress-<span class="hlt">strain</span> nonlinear hysteretic behavior disappears when the experiment is performed at a very low <span class="hlt">strain</span>-rate, implying that a rate dependent nonlinear <span class="hlt">elastic</span> model would be useful (Gusev et al., PRB 2004). Our results also suggest that when <span class="hlt">elastic</span> nonlinear Earth processes are studied, stress forcing frequency is an important consideration, and may lead to unexpected behaviors.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/750170','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/750170"><span id="translatedtitle">Spatial parallelism of a 3D <span class="hlt">finite</span> difference, velocity-stress <span class="hlt">elastic</span> wave propagation code</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Minkoff, S.E.</p> <p>1999-12-01</p> <p><span class="hlt">Finite</span> difference methods for solving the wave equation more accurately capture the physics of waves propagating through the earth than asymptotic solution methods. Unfortunately, <span class="hlt">finite</span> difference simulations for 3D <span class="hlt">elastic</span> wave propagation are expensive. The authors model waves in a 3D isotropic <span class="hlt">elastic</span> earth. The wave equation solution consists of three velocity components and six stresses. The partial derivatives are discretized using 2nd-order in time and 4th-order in space staggered <span class="hlt">finite</span> difference operators. Staggered schemes allow one to obtain additional accuracy (via centered <span class="hlt">finite</span> differences) without requiring additional storage. The serial code is most unique in its ability to model a number of different types of seismic sources. The parallel implementation uses the MPI library, thus allowing for portability between platforms. Spatial parallelism provides a highly efficient strategy for parallelizing <span class="hlt">finite</span> difference simulations. In this implementation, one can decompose the global problem domain into one-, two-, and three-dimensional processor decompositions with 3D decompositions generally producing the best parallel speedup. Because I/O is handled largely outside of the time-step loop (the most expensive part of the simulation) the authors have opted for straight-forward broadcast and reduce operations to handle I/O. The majority of the communication in the code consists of passing subdomain face information to neighboring processors for use as ghost cells. When this communication is balanced against computation by allocating subdomains of reasonable size, they observe excellent scaled speedup. Allocating subdomains of size 25 x 25 x 25 on each node, they achieve efficiencies of 94% on 128 processors. Numerical examples for both a layered earth model and a homogeneous medium with a high-velocity blocky inclusion illustrate the accuracy of the parallel code.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/15182','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/15182"><span id="translatedtitle">Spatial Parallelism of a 3D <span class="hlt">Finite</span> Difference, Velocity-Stress <span class="hlt">Elastic</span> Wave Propagation Code</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>MINKOFF,SUSAN E.</p> <p>1999-12-09</p> <p><span class="hlt">Finite</span> difference methods for solving the wave equation more accurately capture the physics of waves propagating through the earth than asymptotic solution methods. Unfortunately. <span class="hlt">finite</span> difference simulations for 3D <span class="hlt">elastic</span> wave propagation are expensive. We model waves in a 3D isotropic <span class="hlt">elastic</span> earth. The wave equation solution consists of three velocity components and six stresses. The partial derivatives are discretized using 2nd-order in time and 4th-order in space staggered <span class="hlt">finite</span> difference operators. Staggered schemes allow one to obtain additional accuracy (via centered <span class="hlt">finite</span> differences) without requiring additional storage. The serial code is most unique in its ability to model a number of different types of seismic sources. The parallel implementation uses the MP1 library, thus allowing for portability between platforms. Spatial parallelism provides a highly efficient strategy for parallelizing <span class="hlt">finite</span> difference simulations. In this implementation, one can decompose the global problem domain into one-, two-, and three-dimensional processor decompositions with 3D decompositions generally producing the best parallel speed up. Because i/o is handled largely outside of the time-step loop (the most expensive part of the simulation) we have opted for straight-forward broadcast and reduce operations to handle i/o. The majority of the communication in the code consists of passing subdomain face information to neighboring processors for use as ''ghost cells''. When this communication is balanced against computation by allocating subdomains of reasonable size, we observe excellent scaled speed up. Allocating subdomains of size 25 x 25 x 25 on each node, we achieve efficiencies of 94% on 128 processors. Numerical examples for both a layered earth model and a homogeneous medium with a high-velocity blocky inclusion illustrate the accuracy of the parallel code.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016GeoJI.tmp..108Z','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016GeoJI.tmp..108Z"><span id="translatedtitle">A new spectral <span class="hlt">finite</span> volume method for <span class="hlt">elastic</span> wave modelling on unstructured meshes</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Zhang, Wensheng; Zhuang, Yuan; Chung, Eric T.</p> <p>2016-04-01</p> <p>In this paper, we consider a new spectral <span class="hlt">finite</span> volume method for the <span class="hlt">elastic</span> wave equations. Our new <span class="hlt">finite</span> volume method is based on a piecewise constant approximation on a fine mesh and a high-order polynomial reconstruction on a coarser mesh. Our new method is constructed based on two existing techniques, the high-order <span class="hlt">finite</span> volume method and the spectral <span class="hlt">finite</span> volume method. In fact, we will construct a new method to take advantage of both methods. More precisely, our method has two distinctive features. The first one is that the local polynomial reconstructions are performed on the coarse triangles, and the reconstruction matrices for all the coarse triangles are the same. This fact enhances the parallelization of our algorithm. We will present a parallel implementation of our method and show excellent efficiency results. The second one is that, by using a suitable number of finer triangles with a coarse triangle, we obtain an over-determined reconstruction system, which can enhance the robustness of the reconstruction process. To derive our scheme, standard <span class="hlt">finite</span> volume technique is applied to each fine triangle, and the high-order reconstructed polynomials, computed on coarse triangles, are used to compute numerical fluxes. We will present numerical results to show the performance of our method. Our method is presented for 2D problems, but the same methodology can be applied to 3D.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20160006415','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20160006415"><span id="translatedtitle"><span class="hlt">Elastic</span> and Piezoelectric Properties of Boron Nitride Nanotube Composites. Part II; <span class="hlt">Finite</span> Element Model</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Kim, H. Alicia; Hardie, Robert; Yamakov, Vesselin; Park, Cheol</p> <p>2015-01-01</p> <p>This paper is the second part of a two-part series where the first part presents a molecular dynamics model of a single Boron Nitride Nanotube (BNNT) and this paper scales up to multiple BNNTs in a polymer matrix. This paper presents <span class="hlt">finite</span> element (FE) models to investigate the effective <span class="hlt">elastic</span> and piezoelectric properties of (BNNT) nanocomposites. The nanocomposites studied in this paper are thin films of polymer matrix with aligned co-planar BNNTs. The FE modelling approach provides a computationally efficient way to gain an understanding of the material properties. We examine several FE models to identify the most suitable models and investigate the effective properties with respect to the BNNT volume fraction and the number of nanotube walls. The FE models are constructed to represent aligned and randomly distributed BNNTs in a matrix of resin using 2D and 3D hollow and 3D filled cylinders. The homogenisation approach is employed to determine the overall <span class="hlt">elastic</span> and piezoelectric constants for a range of volume fractions. These models are compared with an analytical model based on Mori-Tanaka formulation suitable for <span class="hlt">finite</span> length cylindrical inclusions. The model applies to primarily single-wall BNNTs but is also extended to multi-wall BNNTs, for which preliminary results will be presented. Results from the Part 1 of this series can help to establish a constitutive relationship for input into the <span class="hlt">finite</span> element model to enable the modeling of multiple BNNTs in a polymer matrix.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19860016596','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19860016596"><span id="translatedtitle">A fourth order accurate <span class="hlt">finite</span> difference scheme for the computation of <span class="hlt">elastic</span> waves</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Bayliss, A.; Jordan, K. E.; Lemesurier, B. J.; Turkel, E.</p> <p>1986-01-01</p> <p>A <span class="hlt">finite</span> difference for <span class="hlt">elastic</span> waves is introduced. The model is based on the first order system of equations for the velocities and stresses. The differencing is fourth order accurate on the spatial derivatives and second order accurate in time. The model is tested on a series of examples including the Lamb problem, scattering from plane interf aces and scattering from a fluid-<span class="hlt">elastic</span> interface. The scheme is shown to be effective for these problems. The accuracy and stability is insensitive to the Poisson ratio. For the class of problems considered here it is found that the fourth order scheme requires for two-thirds to one-half the resolution of a typical second order scheme to give comparable accuracy.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19770003340','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19770003340"><span id="translatedtitle">Some convergence properties of <span class="hlt">finite</span> element approximations of problems in nonlinear <span class="hlt">elasticity</span> with multi-valued solutions</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Oden, J. T.</p> <p>1976-01-01</p> <p>Some results of studies of convergence and accuracy of <span class="hlt">finite</span> element approximations of certain nonlinear problems encountered in <span class="hlt">finite</span> <span class="hlt">elasticity</span> are presented. A general technique for obtaining error bounds is also described together with an existence theorem. Numerical results obtained by solving a representative problem are also included.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013RMRE...46..315P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013RMRE...46..315P"><span id="translatedtitle">Is there Link between the Type of the Volumetric <span class="hlt">Strain</span> Curve and <span class="hlt">Elastic</span> Constants, Porosity, Stress and <span class="hlt">Strain</span> Characteristics ?</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Palchik, V.</p> <p>2013-03-01</p> <p>The stress [crack damage stress ( σ cd) and uniaxial compressive strength ( σ c)] and <span class="hlt">strain</span> characteristics [maximum total volumetric <span class="hlt">strain</span> ( ɛ cd), axial failure <span class="hlt">strain</span> ( ɛ af)], porosity ( n) and <span class="hlt">elastic</span> constants [<span class="hlt">elastic</span> modulus ( E) and Poisson's ratio ( ν)] and their ratios were coordinated with the existence of two different types (type 1 and type 2) of volumetric <span class="hlt">strain</span> curve. Type 1 volumetric <span class="hlt">strain</span> curve has a reversal point and, therefore, σ cd is less than the uniaxial compressive strength ( σ c). Type 2 has no reversal point, and the bulk volume of rock decreases until its failure occurs (i.e., σ cd = σ c). It is confirmed that the ratio between the <span class="hlt">elastic</span> modulus ( E) and the parameter λ = n/ ɛ cd strongly affects the crack damage stress ( σ cd) for both type 1 and type 2 volumetric <span class="hlt">strain</span> curves. It is revealed that heterogeneous carbonate rock samples exhibit different types of the volumetric <span class="hlt">strain</span> curve even within the same rock formation, and the range of σ cd/ σ c = 0.54-1 for carbonate rocks is wider than the range (0.71 < σ cd/ σ c < 0.84) obtained by other researchers for granites, sandstones and quartzite. It is established that there is no connection between the type of the volumetric <span class="hlt">strain</span> curve and values of n, E, σ cd, ν, E/(1 - 2 ν), M R = E/ σ c and E/ λ. On the other hand, the type of volumetric <span class="hlt">strain</span> curve is connected with the values of λ and the ratio between the axial failure <span class="hlt">strain</span> ( ɛ af) and the maximum total volumetric <span class="hlt">strain</span> ( ɛ cd). It is argued that in case of small ɛ af/ ɛ cd-small λ, volumetric <span class="hlt">strain</span> curve follows the type 2.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015CompM..56.1039W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015CompM..56.1039W"><span id="translatedtitle">A <span class="hlt">strain</span>-morphed nonlocal meshfree method for the regularized particle simulation of <span class="hlt">elastic</span>-damage induced <span class="hlt">strain</span> localization problems</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Wu, C. T.; Wu, Youcai; Koishi, M.</p> <p>2015-12-01</p> <p>In this work, a <span class="hlt">strain</span>-morphed nonlocal meshfree method is developed to overcome the computational challenges for the simulation of <span class="hlt">elastic</span>-damage induced <span class="hlt">strain</span> localization problem when the spatial domain integration is performed based on the background cells and Gaussian quadrature rule. The new method is established by introducing the decomposed <span class="hlt">strain</span> fields from a meshfree <span class="hlt">strain</span> smoothing to the penalized variational formulation. While the stabilization <span class="hlt">strain</span> field circumvents the onerous zero-energy modes inherent in the direct nodal integration scheme, the regularization <span class="hlt">strain</span> field aims to avoid the pathological localization of deformation in Galerkin meshfree solution using the weak-discontinuity approach. A <span class="hlt">strain</span> morphing algorithm is introduced to couple the locality and non-locality of the decomposed <span class="hlt">strain</span> approximations such that the continuity condition in the coupled <span class="hlt">strain</span> field is met under the Galerkin meshfree framework using the direct nodal integration scheme. Three numerical benchmarks are examined to demonstrate the effectiveness and accuracy of the proposed method for the regularization of <span class="hlt">elastic</span>-damage induced <span class="hlt">strain</span> localization problems.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19960025213','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19960025213"><span id="translatedtitle">Non-Reflecting Regions for <span class="hlt">Finite</span> Difference Methods in Modeling of <span class="hlt">Elastic</span> Wave Propagation in Plates</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Kishoni, Doron; Taasan, Shlomo</p> <p>1994-01-01</p> <p>Solution of the wave equation using techniques such as <span class="hlt">finite</span> difference or <span class="hlt">finite</span> element methods can model <span class="hlt">elastic</span> wave propagation in solids. This requires mapping the physical geometry into a computational domain whose size is governed by the size of the physical domain of interest and by the required resolution. This computational domain, in turn, dictates the computer memory requirements as well as the calculation time. Quite often, the physical region of interest is only a part of the whole physical body, and does not necessarily include all the physical boundaries. Reduction of the calculation domain requires positioning an artificial boundary or region where a physical boundary does not exist. It is important however that such a boundary, or region, will not affect the internal domain, i.e., it should not cause reflections that propagate back into the material. This paper concentrates on the issue of constructing such a boundary region.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010MsT..........8P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010MsT..........8P"><span id="translatedtitle"><span class="hlt">Finite</span> Element Modeling of the Behavior of Armor Materials Under High <span class="hlt">Strain</span> Rates and Large <span class="hlt">Strains</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Polyzois, Ioannis</p> <p></p> <p>For years high strength steels and alloys have been widely used by the military for making armor plates. Advances in technology have led to the development of materials with improved resistance to penetration and deformation. Until recently, the behavior of these materials under high <span class="hlt">strain</span> rates and large <span class="hlt">strains</span> has been primarily based on laboratory testing using the Split Hopkinson Pressure Bar apparatus. With the advent of sophisticated computer programs, computer modeling and <span class="hlt">finite</span> element simulations are being developed to predict the deformation behavior of these metals for a variety of conditions similar to those experienced during combat. In the present investigation, a modified direct impact Split Hopkinson Pressure Bar apparatus was modeled using the <span class="hlt">finite</span> element software ABAQUS 6.8 for the purpose of simulating high <span class="hlt">strain</span> rate compression of specimens of three armor materials: maraging steel 300, high hardness armor (HHA), and aluminum alloy 5083. These armor materials, provided by the Canadian Department of National Defence, were tested at the University of Manitoba by others. In this study, the empirical Johnson-Cook visco-plastic and damage models were used to simulate the deformation behavior obtained experimentally. A series of stress-time plots at various projectile impact momenta were produced and verified by comparison with experimental data. The impact momentum parameter was chosen rather than projectile velocity to normalize the initial conditions for each simulation. Phenomena such as the formation of adiabatic shear bands caused by deformation at high <span class="hlt">strains</span> and <span class="hlt">strain</span> rates were investigated through simulations. It was found that the Johnson-Cook model can accurately simulate the behavior of body-centered cubic (BCC) metals such as steels. The maximum shear stress was calculated for each simulation at various impact momenta. The <span class="hlt">finite</span> element model showed that shear failure first occurred in the center of the cylindrical specimen and</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/24113298','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/24113298"><span id="translatedtitle">Cement lines and interlamellar areas in compact bone as <span class="hlt">strain</span> amplifiers - contributors to <span class="hlt">elasticity</span>, fracture toughness and mechanotransduction.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Nobakhti, Sabah; Limbert, Georges; Thurner, Philipp J</p> <p>2014-01-01</p> <p>Bone is multi-scale hierarchical composite material making the prediction of fragility, as well as pinning it to a certain cause, complicated. For proper mechanical simulation and reflection of bone properties in models, microscopic structural features of bone tissue need to be included. This study sets out to gain a mechanistic insight into the role of various microstructural features of bone tissue in particular cement lines and interlamellar areas. Further the hypothesis that compliant interlamellar areas and cement lines within osteonal bone act as <span class="hlt">strain</span> amplifiers was explored. To this end, a series of experimentally-based micromechanical <span class="hlt">finite</span> element models of bovine osteonal bone were developed. Different levels of detail for the bone microstructure were considered and combined with the results of physical three-point bending tests and an analytical composite model of a single osteon. The objective was to examine local and global effects of interface structures. The geometrical and microstructural characteristics of the bone samples were derived from microscopy imaging. Parametric <span class="hlt">finite</span> element studies were conducted to determine optimal values of the <span class="hlt">elastic</span> modulus of interstitial bone and interlamellar areas. The average isotropic <span class="hlt">elastic</span> modulus of interfaces suggested in this study is 88.5MPa. Based on the modelling results, it is shown that interfaces are areas of accumulated <span class="hlt">strain</span> in bone and are likely to act as potential paths for crack propagation. The <span class="hlt">strain</span> amplification capability of interface structures in the order of 10 predicted by the models suggests a new explanation for the levels of <span class="hlt">strain</span> required in bone homoeostasis for maintenance and adaptation. PMID:24113298</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/663574','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/663574"><span id="translatedtitle"><span class="hlt">Elastic</span>-plastic <span class="hlt">strain</span> acceptance criterion for structures subject to rapidly applied transient dynamic loading</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Solonick, W.</p> <p>1996-11-01</p> <p>Rapidly applied transient dynamic loads produce stresses and deflections in structures that typically exceed those from static loading conditions. Previous acceptance criteria for structures designed for rapidly applied transient dynamic loading limited stresses to those determined from <span class="hlt">elastic</span> analysis. Different stress limits were established for different grades of structure depending upon the amount of permanent set considered acceptable. Structure allowed to sustain very limited permanent set is designed to stress limits not significantly greater than yield stress. Greater permanent set in structure under rapidly applied transient dynamic loading conditions is permitted by establishing stress limits that are significantly greater than yield stress but still provide adequate safety margin (with respect to failure). This paper presents a <span class="hlt">strain</span>-based <span class="hlt">elastic</span>-plastic (i.e., inelastic) analysis criterion developed as an alternative to the more conservative stress-based <span class="hlt">elastic</span> analysis stress criterion for structures subjected to rapidly applied transient dynamic loading. The <span class="hlt">strain</span> limits established are based on a fraction of the <span class="hlt">strain</span> at ultimate stress obtained from an engineering stress/<span class="hlt">strain</span> curve of the material. <span class="hlt">Strains</span> limits are categorized by type as membrane or surface and by region as general, local, or concentrated. The application of the <span class="hlt">elastic</span>-plastic criterion provides a more accurate, less conservative design/analysis basis for structures than that used in <span class="hlt">elastic</span> stress-based analysis criteria, while still providing adequate safety margins.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/815192','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/815192"><span id="translatedtitle"><span class="hlt">Elastic</span>-Plastic <span class="hlt">Strain</span> Acceptance Criteria for Structures Subject to Rapidly Applied Transient Dynamic Loading</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>W.R. Solonick</p> <p>2003-04-01</p> <p>Rapidly applied transient dynamic loads produce stresses and deflections in structures that typically exceed those from static loading conditions. Previous acceptance criteria for structures designed for rapidly applied transient dynamic loading limited stresses to those determined from <span class="hlt">elastic</span> analysis. Different stress limits were established for different grades of structure depending upon the amount of permanent set considered acceptable. Structure allowed to sustain very limited permanent set is designed to stress limits not significantly greater than yield stress. Greater permanent set in structure under rapidly applied transient dynamic loading conditions is permitted by establishing stress limits that are significantly greater than yield stress but still provide adequate safety margin (with respect to failure). This paper presents a <span class="hlt">strain</span>-based <span class="hlt">elastic</span>-plastic (i.e., inelastic) analysis criterion developed as an alternative to the more conservative stress-based <span class="hlt">elastic</span> analysis stress criterion for structures subjected to rapidly applied transient dynamic loading. The <span class="hlt">strain</span> limits established are based on material ductility considerations only and are set as a fraction of the <span class="hlt">strain</span> at ultimate stress obtained from an engineering stress/<span class="hlt">strain</span> curve of the material. <span class="hlt">Strains</span> limits are categorized by type as membrane or surface and by region as general, local , or concentrated. The application of the <span class="hlt">elastic</span>-plastic criterion provides a more accurate, less conservative design/analysis basis for structures than that used in <span class="hlt">elastic</span> stress-based analysis criteria, while still providing adequate safety margins.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19940010246','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19940010246"><span id="translatedtitle"><span class="hlt">Elastic</span>-plastic <span class="hlt">finite</span> element analyses of an unidirectional, 9 vol percent tungsten fiber reinforced copper matrix composite</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Sanfeliz, Jose G.</p> <p>1993-01-01</p> <p>Micromechanical modeling via <span class="hlt">elastic</span>-plastic <span class="hlt">finite</span> element analyses were performed to investigate the effects that the residual stresses and the degree of matrix work hardening (i.e., cold-worked, annealed) have upon the behavior of a 9 vol percent, unidirectional W/Cu composite, undergoing tensile loading. The inclusion of the residual stress-containing state as well as the simulated matrix material conditions proved to be significant since the Cu matrix material exhibited plastic deformation, which affected the subsequent tensile response of the composite system. The stresses generated during cooldown to room temperature from the manufacturing temperature were more of a factor on the annealed-matrix composite, since they induced the softened matrix to plastically flow. This event limited the total load-carrying capacity of this matrix-dominated, ductile-ductile type material system. Plastic deformation of the hardened-matrix composite during the thermal cooldown stage was not considerable, therefore, the composite was able to sustain a higher stress before showing any appreciable matrix plasticity. The predicted room temperature, stress-<span class="hlt">strain</span> response, and deformation stages under both material conditions represented upper and lower bounds characteristic of the composite's tensile behavior. The initial deformation stage for the hardened material condition showed negligible matrix plastic deformation while for the annealed state, its initial deformation stage showed extensive matrix plasticity. Both material conditions exhibited a final deformation stage where the fiber and matrix were <span class="hlt">straining</span> plastically. The predicted stress-<span class="hlt">strain</span> results were compared to the experimental, room temperature, tensile stress-<span class="hlt">strain</span> curve generated from this particular composite system. The analyses indicated that the actual thermal-mechanical state of the composite's Cu matrix, represented by the experimental data, followed the annealed material condition.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2016JPCM...28C5302T&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2016JPCM...28C5302T&link_type=ABSTRACT"><span id="translatedtitle">Directional anisotropy, <span class="hlt">finite</span> size effect and <span class="hlt">elastic</span> properties of hexagonal boron nitride</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Thomas, Siby; Ajith, K. M.; Valsakumar, M. C.</p> <p>2016-07-01</p> <p>Classical molecular dynamics simulations have been performed to analyze the <span class="hlt">elastic</span> and mechanical properties of two-dimensional (2D) hexagonal boron nitride (h-BN) using a Tersoff-type interatomic empirical potential. We present a systematic study of h-BN for various system sizes. Young’s modulus and Poisson’s ratio are found to be anisotropic for <span class="hlt">finite</span> sheets whereas they are isotropic for the infinite sheet. Both of them increase with system size in accordance with a power law. It is concluded from the computed values of <span class="hlt">elastic</span> constants that h-BN sheets, <span class="hlt">finite</span> or infinite, satisfy Born’s criterion for mechanical stability. Due to the the strong in-plane sp2 bonds and the small mass of boron and nitrogen atoms, h-BN possesses high longitudinal and shear velocities. The variation of bending rigidity with system size is calculated using the Foppl–von Karman approach by coupling the in-plane bending and out-of-plane stretching modes of the 2D h-BN.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015JMPSo..74..175H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015JMPSo..74..175H"><span id="translatedtitle">A micromechanical damage and fracture model for polymers based on fractional <span class="hlt">strain</span>-gradient <span class="hlt">elasticity</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Heyden, S.; Li, B.; Weinberg, K.; Conti, S.; Ortiz, M.</p> <p>2015-01-01</p> <p>We formulate a simple one-parameter macroscopic model of distributed damage and fracture of polymers that is amenable to a straightforward and efficient numerical implementation. We show that the macroscopic model can be rigorously derived, in the sense of optimal scaling, from a micromechanical model of chain <span class="hlt">elasticity</span> and failure regularized by means of fractional <span class="hlt">strain</span>-gradient <span class="hlt">elasticity</span>. In particular, we derive optimal scaling laws that supply a link between the single parameter of the macroscopic model, namely, the critical energy-release rate of the material, and micromechanical parameters pertaining to the <span class="hlt">elasticity</span> and strength of the polymer chains and to the <span class="hlt">strain</span>-gradient <span class="hlt">elasticity</span> regularization. We show how the critical energy-release rate of specific materials can be determined from test data. Finally, we demonstrate the scope and fidelity of the model by means of an example of application, namely, Taylor-impact experiments of polyurea 1000 rods.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015JGE....12..435A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015JGE....12..435A"><span id="translatedtitle"><span class="hlt">Finite</span> difference <span class="hlt">elastic</span> wave modeling with an irregular free surface using ADER scheme</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Almuhaidib, Abdulaziz M.; Nafi Toksöz, M.</p> <p>2015-06-01</p> <p>In numerical modeling of seismic wave propagation in the earth, we encounter two important issues: the free surface and the topography of the surface (i.e. irregularities). In this study, we develop a 2D <span class="hlt">finite</span> difference solver for the <span class="hlt">elastic</span> wave equation that combines a 4th- order ADER scheme (Arbitrary high-order accuracy using DERivatives), which is widely used in aeroacoustics, with the characteristic variable method at the free surface boundary. The idea is to treat the free surface boundary explicitly by using ghost values of the solution for points beyond the free surface to impose the physical boundary condition. The method is based on the velocity-stress formulation. The ultimate goal is to develop a numerical solver for the <span class="hlt">elastic</span> wave equation that is stable, accurate and computationally efficient. The solver treats smooth arbitrary-shaped boundaries as simple plane boundaries. The computational cost added by treating the topography is negligible compared to flat free surface because only a small number of grid points near the boundary need to be computed. In the presence of topography, using 10 grid points per shortest shear-wavelength, the solver yields accurate results. Benchmark numerical tests using several complex models that are solved by our method and other independent accurate methods show an excellent agreement, confirming the validity of the method for modeling <span class="hlt">elastic</span> waves with an irregular free surface.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/24084656','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/24084656"><span id="translatedtitle"><span class="hlt">Elastic</span> bending modulus of single-layer molybdenum disulfide (MoS2): <span class="hlt">finite</span> thickness effect.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Jiang, Jin-Wu; Qi, Zenan; Park, Harold S; Rabczuk, Timon</p> <p>2013-11-01</p> <p>We derive, from an empirical interaction potential, an analytic formula for the <span class="hlt">elastic</span> bending modulus of single-layer MoS2 (SLMoS2). By using this approach, we do not need to define or estimate a thickness value for SLMoS2, which is important due to the substantial controversy in defining this value for two-dimensional or ultrathin nanostructures such as graphene and nanotubes. The obtained <span class="hlt">elastic</span> bending modulus of 9.61 eV in SLMoS2 is significantly higher than the bending modulus of 1.4 eV in graphene, and is found to be within the range of values that are obtained using thin shell theory with experimentally obtained values for the <span class="hlt">elastic</span> constants of SLMoS2. This increase in bending modulus as compared to monolayer graphene is attributed, through our analytic expression, to the <span class="hlt">finite</span> thickness of SLMoS2. Specifically, while each monolayer of S atoms contributes 1.75 eV to the bending modulus, which is similar to the 1.4 eV bending modulus of monolayer graphene, the additional pairwise and angular interactions between out of plane Mo and S atoms contribute 5.84 eV to the bending modulus of SLMoS2. PMID:24084656</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4667184','PMC'); return false;" href="http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4667184"><span id="translatedtitle">Revealing ultralarge and localized <span class="hlt">elastic</span> lattice <span class="hlt">strains</span> in Nb nanowires embedded in NiTi matrix</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Zang, Ketao; Mao, Shengcheng; Cai, Jixiang; Liu, Yinong; Li, Haixin; Hao, Shijie; Jiang, Daqiang; Cui, Lishan</p> <p>2015-01-01</p> <p>Freestanding nanowires have been found to exhibit ultra-large <span class="hlt">elastic</span> <span class="hlt">strains</span> (4 to 7%) and ultra-high strengths, but exploiting their intrinsic superior mechanical properties in bulk forms has proven to be difficult. A recent study has demonstrated that ultra-large <span class="hlt">elastic</span> <span class="hlt">strains</span> of ~6% can be achieved in Nb nanowires embedded in a NiTi matrix, on the principle of lattice <span class="hlt">strain</span> matching. To verify this hypothesis, this study investigated the <span class="hlt">elastic</span> deformation behavior of a Nb nanowire embedded in NiTi matrix by means of in situ transmission electron microscopic measurement during tensile deformation. The experimental work revealed that ultra-large local <span class="hlt">elastic</span> lattice <span class="hlt">strains</span> of up to 8% are induced in the Nb nanowire in regions adjacent to stress-induced martensite domains in the NiTi matrix, whilst other parts of the nanowires exhibit much reduced lattice <span class="hlt">strains</span> when adjacent to the untransformed austenite in the NiTi matrix. These observations provide a direct evidence of the proposed mechanism of lattice <span class="hlt">strain</span> matching, thus a novel approach to designing nanocomposites of superior mechanical properties. PMID:26625854</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_5");'>5</a></li> <li><a href="#" onclick='return showDiv("page_6");'>6</a></li> <li class="active"><span>7</span></li> <li><a href="#" onclick='return showDiv("page_8");'>8</a></li> <li><a href="#" onclick='return showDiv("page_9");'>9</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_7 --> <div id="page_8" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_6");'>6</a></li> <li><a href="#" onclick='return showDiv("page_7");'>7</a></li> <li class="active"><span>8</span></li> <li><a href="#" onclick='return showDiv("page_9");'>9</a></li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="141"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015JMPSo..78..298L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015JMPSo..78..298L"><span id="translatedtitle">A higher-order nonlocal <span class="hlt">elasticity</span> and <span class="hlt">strain</span> gradient theory and its applications in wave propagation</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Lim, C. W.; Zhang, G.; Reddy, J. N.</p> <p>2015-05-01</p> <p>In recent years there have been many papers that considered the effects of material length scales in the study of mechanics of solids at micro- and/or nano-scales. There are a number of approaches and, among them, one set of papers deals with Eringen's differential nonlocal model and another deals with the <span class="hlt">strain</span> gradient theories. The modified couple stress theory, which also accounts for a material length scale, is a form of a <span class="hlt">strain</span> gradient theory. The large body of literature that has come into existence in the last several years has created significant confusion among researchers about the length scales that these various theories contain. The present paper has the objective of establishing the fact that the length scales present in nonlocal <span class="hlt">elasticity</span> and <span class="hlt">strain</span> gradient theory describe two entirely different physical characteristics of materials and structures at nanoscale. By using two principle kernel functions, the paper further presents a theory with application examples which relates the classical nonlocal <span class="hlt">elasticity</span> and <span class="hlt">strain</span> gradient theory and it results in a higher-order nonlocal <span class="hlt">strain</span> gradient theory. In this theory, a higher-order nonlocal <span class="hlt">strain</span> gradient <span class="hlt">elasticity</span> system which considers higher-order stress gradients and <span class="hlt">strain</span> gradient nonlocality is proposed. It is based on the nonlocal effects of the <span class="hlt">strain</span> field and first gradient <span class="hlt">strain</span> field. This theory intends to generalize the classical nonlocal <span class="hlt">elasticity</span> theory by introducing a higher-order <span class="hlt">strain</span> tensor with nonlocality into the stored energy function. The theory is distinctive because the classical nonlocal stress theory does not include nonlocality of higher-order stresses while the common <span class="hlt">strain</span> gradient theory only considers local higher-order <span class="hlt">strain</span> gradients without nonlocal effects in a global sense. By establishing the constitutive relation within the thermodynamic framework, the governing equations of equilibrium and all boundary conditions are derived via the variational</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016TePhL..42..121G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016TePhL..42..121G"><span id="translatedtitle">Determination of third-order <span class="hlt">elastic</span> moduli via parameters of bulk <span class="hlt">strain</span> solitons</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Garbuzov, F. E.; Samsonov, A. M.; Semenov, A. A.; Shvartz, A. G.</p> <p>2016-02-01</p> <p>A method is proposed aimed for determination of the third-order <span class="hlt">elastic</span> moduli (Murnaghan moduli) based on the estimation of measured parameters of bulk <span class="hlt">strain</span> solitons in the three main waveguide configurations, a rod, a plate, and a shell. Formulas connecting the third-order moduli of the waveguide material and the parameters of a solitary <span class="hlt">strain</span> wave (amplitude, velocity, full width at half-maximum) are derived. If the soliton parameters measured in three waveguide types manufactured from the same material are available, determination of the third-order <span class="hlt">elastic</span> moduli is reduced to the solution of a system of three algebraic equations with a nondegenerate matrix.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/1051435','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/1051435"><span id="translatedtitle">Application Of <span class="hlt">Elastic</span> Perfectly Plastic Cyclic Analysis To Assessment Of Creep <span class="hlt">Strain</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Carter, Peter; Jetter, Robert I; Sham, Sam</p> <p>2012-01-01</p> <p>A cyclic <span class="hlt">elastic</span>-perfectly plastic analysis method is proposed which provides a conservative estimate to cyclic creep <span class="hlt">strain</span> accumulation within the ratchet boundary. The method is to check for ratcheting based on an <span class="hlt">elastic</span>-perfectly material with a temperature-dependent pseudo yield stress defined by temperature, time and stress to give 1% creep <span class="hlt">strain</span>. It does not require stress classification and is also applicable to a full range of temperature above and below the creep regime. This simplified method could be used as a rapid screening calculation, with full time-dependent creep analysis used if necessary.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/25585402','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/25585402"><span id="translatedtitle">Analytical phase-tracking-based <span class="hlt">strain</span> estimation for ultrasound <span class="hlt">elasticity</span>.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Yuan, Lili; Pedersen, Peder C</p> <p>2015-01-01</p> <p>A new <span class="hlt">strain</span> estimator for quasi-static elastography is presented, based on tracking of the analytical signal phase as a function of the external force. Two implementations are introduced: zero-phase search with moving window (SMW) and zero-phase band tracking using connected component labeling (CCL). Low analytical signal amplitude caused by local destructive interference is associated with large error in the phase trajectories, and amplitude thresholding can thus be used to terminate the phase tracking along a particular path. Interpolation is then applied to estimate displacement in the eliminated path. The paper describes first a mathematical analysis based on 1-D multi-scatter modeling, followed by a statistical study of the displacement and <span class="hlt">strain</span> error. Simulation and experiment with an inhomogeneous phantom indicate that SMW and CCL are capable of reliably estimating tissue displacement and <span class="hlt">strain</span> over a larger range of deformation than standard timedomain cross-correlation (SCC). Results also show that SMW is roughly 40 times faster than SCC with comparable or even better accuracy. CCL is slower than SMW, but more noise robust. Simulation assessment at compression level 3% and 6% with SNR 20 dB demonstrates average <span class="hlt">strain</span> error for SMW and CCL of 10%, whereas SCC achieves 18%. PMID:25585402</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1997PhDT.......174H&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1997PhDT.......174H&link_type=ABSTRACT"><span id="translatedtitle">Statistical model for the prediction of <span class="hlt">elastic</span> wave scattering from <span class="hlt">finite</span> complicated shells</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>He, Hua</p> <p></p> <p>This thesis develops a simple statistical model to estimate bistatic <span class="hlt">elastic</span> scattering from <span class="hlt">finite</span> complicated shells in the mid-frequency range, 3 < ka/ < 10. The model has three parts: (1) sound power injection into the shell; (2) coupling among the <span class="hlt">elastic</span> waves in the shell and wave power equipartition (3) sound radiation from the shell. Within 30o of beam aspect, sound power injection into the shell is mainly caused by acoustic trace matching, and is estimated by using an infinitely long shell model. Once trace matched, the compressional and shear waves can couple to each other and to the subsonic flexural waves at shell discontinuities such as bulkheads and endcaps. Under extensive wave conversion, wave power, defined as energy density multiplied by axial group speed, is hypothesized to be equipartitioned among the <span class="hlt">elastic</span> wave types. Numerical calculations are conducted and the results show that the wave power equipartition hypothesis is plausible for a <span class="hlt">finite</span> endcapped shell with four heavy deep rings. Using the wave power equipartition hypothesis, the shell motion is then converted to sound pressure in the surrounding fluid using Green's theorem. The sound radiation is further extended to the time domain, using random phase realizations and a decay rate model, which considers various dissipation mechanisms in the shells. The predicted target strength is compared with measured data for the ringed shell and the internalled shell, with the internal structures resiliently mounted to the rings. In terms of the mean target strength over the frequency region 3 < ka/ < 10 and the observation region within 30o of beam aspect, the prediction differs from the measured data by less than 2.5 dB for the second and third roundtrip of the trace matched wave in the shells, as well as for a time integrated case. The ring influence on <span class="hlt">elastic</span> wave speeds is also studied. Inclusion of the influence in the model does not generally yield a better agreement with the</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19940025112','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19940025112"><span id="translatedtitle">Computation of vibration mode <span class="hlt">elastic</span>-rigid and effective weight coefficients from <span class="hlt">finite</span>-element computer program output</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Levy, R.</p> <p>1991-01-01</p> <p>Post-processing algorithms are given to compute the vibratory <span class="hlt">elastic</span>-rigid coupling matrices and the modal contributions to the rigid-body mass matrices and to the effective modal inertias and masses. Recomputation of the <span class="hlt">elastic</span>-rigid coupling matrices for a change in origin is also described. A computational example is included. The algorithms can all be executed by using standard <span class="hlt">finite</span>-element program eigenvalue analysis output with no changes to existing code or source programs.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2005JSG....27.2135V','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2005JSG....27.2135V"><span id="translatedtitle">Influence of object concentration on <span class="hlt">finite</span> <span class="hlt">strain</span> and effective viscosity contrast: insights from naturally deformed packstones</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Vitale, Stefano; Mazzoli, Stefano</p> <p></p> <p>Deformed conglomerates and ooidal/oncoidal packstones are commonly used to evaluate <span class="hlt">finite</span> <span class="hlt">strain</span> in deformed sedimentary successions. In order to obtain a correct estimate of <span class="hlt">finite</span> <span class="hlt">strain</span>, it is necessary to consider not only the different behaviour of matrix and objects, but also object concentration. The analysis of two-component rocks characterised by high values of packing commonly results in a substantial underestimate of bulk <span class="hlt">strain</span> and of viscosity contrast between objects and matrix. In this study, the effects of the volumetric fraction of competent inclusions on both object and bulk measured <span class="hlt">finite</span> <span class="hlt">strain</span>, as well as on apparent viscosity contrast, have been investigated in naturally deformed packstones characterised by variable object concentration on the scale of the hand specimen (and hence for homogenous viscosity contrast). Object <span class="hlt">finite</span> <span class="hlt">strain</span> has been obtained by Rf/ ϕ analysis, whereas the Fry method provides a measure of whole-rock <span class="hlt">strain</span> that is also a function of inclusion concentration. Therefore, the <span class="hlt">finite</span> <span class="hlt">strain</span> measured by the Fry method is better termed effective bulk <span class="hlt">strain</span>. In order to investigate the role of object concentration, this parameter has been plotted against object and effective bulk <span class="hlt">strain</span>, and also against viscosity contrast. These diagrams show that: (i) for high values of packing, measured object and effective bulk <span class="hlt">strain</span> show values that are significantly lower with respect to the calculated maximum value (that would result in the ideal case of no particle interaction and represents therefore the real bulk <span class="hlt">strain</span> of the samples); (ii) the viscosity contrast shows lower values with respect to the calculated maximum one (that is equal for the three principal sections of the <span class="hlt">finite</span> <span class="hlt">strain</span> ellipsoid), and as packing reaches the maximum value, the viscosity contrast approaches a unit value. Empirical equations have also been found that link object concentration with both object and effective bulk <span class="hlt">finite</span> <span class="hlt">strain</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=19900037329&hterms=assumed+strain&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3Dassumed%2Bstrain','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=19900037329&hterms=assumed+strain&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3Dassumed%2Bstrain"><span id="translatedtitle">A variational justification of the assumed natural <span class="hlt">strain</span> formulation of <span class="hlt">finite</span> elements. I - Variational principles. II - The C(0) four-node plate element</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Militello, Carmelo; Felippa, Carlos A.</p> <p>1990-01-01</p> <p>The assumed natural <span class="hlt">strain</span> formulation of <span class="hlt">finite</span> elements is interpreted from a variational standpoint. The approach is based on hybrid extensions of the Reissner-type functional which uses the <span class="hlt">strains</span> and displacements as independent fields. Consideration is restricted to linear <span class="hlt">elasticity</span>. The four-node C(0) plate-bending quadrilateral is used as a specific example to illustrate the application of the present interpretation. A key finding is that any change in the <span class="hlt">strain</span>-displacement interpolation from the variationally consistent interpolation must be associated in some way to the addition of incompatible displacement modes.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012JaJAP..51g6702J','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012JaJAP..51g6702J"><span id="translatedtitle">Determination of Constant <span class="hlt">Strain</span> Gradients of <span class="hlt">Elastically</span> Bent Crystal Using X-ray Mirage Fringes</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Jongsukswat, Sukswat; Fukamachi, Tomoe; Hirano, Kenji; Ju, Dongying; Negishi, Riichirou; Shimojo, Masayuki; Hirano, Keiichi; Kawamura, Takaaki</p> <p>2012-07-01</p> <p>Two experimental approaches are studied to determine a parameter of the <span class="hlt">strain</span> gradient in an <span class="hlt">elastically</span> bent crystal. In one approach, the parameter is determined by measuring the third peak of the X-ray mirage interference fringes and in the other, by measuring the region where no mirage diffraction beam reaches on the lateral surface of the crystal. Using the X-rays from synchrotron radiation, the mirage fringes have been observed in the 220 reflection of the Si crystal whose <span class="hlt">strain</span> is controlled in cantilever bending. These two approaches both give accurate values of the parameter of the <span class="hlt">strain</span> gradient, showing good agreement with the values calculated using <span class="hlt">elastic</span> theory. In addition, the residual <span class="hlt">strain</span> due to gravity is observed by measuring mirage fringes when the bending force becomes zero.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19740006471','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19740006471"><span id="translatedtitle">Three-dimensional <span class="hlt">elastic</span> stress and displacement analysis of <span class="hlt">finite</span> geometry solids containing cracks</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Gyekenyesi, J. P.; Mendelson, A.</p> <p>1974-01-01</p> <p>The line method of analysis is applied to the Navier-Cauchy equations of <span class="hlt">elastic</span> equilibrium to calculate the displacement distributions in various bodies containing cracks. The application of this method to these equations leads to coupled sets of simultaneous ordinary differential equations whose solutions are obtained along sets of lines in a discretized region. When decoupling the equations and their boundary conditions is not possible, the use of a successive approximation procedure permits the analytical solution of the resulting ordinary differential equations. The results obtained show a considerable potential for using this method in the three-dimensional analysis of <span class="hlt">finite</span> geometry solids and suggest a possible extension of this technique to nonlinear material behavior.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=19850038605&hterms=crack+growth+analysis&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3Dcrack%2Bgrowth%2Banalysis','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=19850038605&hterms=crack+growth+analysis&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3Dcrack%2Bgrowth%2Banalysis"><span id="translatedtitle">An <span class="hlt">elastic</span>-plastic <span class="hlt">finite</span> element analysis of crack initiation, stable crack growth, and instability</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Newman, J. C., Jr.</p> <p>1984-01-01</p> <p>Studies have been conducted to develop efficient techniques to simulate crack extension and to examine various local and global fracture criteria. Of the considered criteria, the crack-tip-opening angle (CTOA) or displacement (CTOD) at a specified distance from the crack tip was shown to be most suited for modeling stable crack growth and instability during the fracture process. The results obtained in a number of studies show the necessity for studying different crack configurations when assessing the validity of any fracture criteria. One of the objectives of the present investigation is related to a critical evaluation of the CTOD growth criterion using an <span class="hlt">elastic</span>-plastic <span class="hlt">finite</span> element analysis under monotonic loading to failure. The analysis was found to predict three stages of crack growth behavior under monotonic loading to failure. Calculated CTOD values agreed well with experimental values for crack growth initiation.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19730012184','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19730012184"><span id="translatedtitle"><span class="hlt">Elastic</span> plate spallation</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Oline, L.; Medaglia, J.</p> <p>1972-01-01</p> <p>The dynamic <span class="hlt">finite</span> element method was used to investigate <span class="hlt">elastic</span> stress waves in a plate. <span class="hlt">Strain</span> displacement and stress <span class="hlt">strain</span> relations are discussed along with the stiffness and mass matrix. The results of studying point load, and distributed load over small, intermediate, and large radii are reported. The derivation of <span class="hlt">finite</span> element matrices, and the derivation of lumped and consistent matrices for one dimensional problems with Laplace transfer solutions are included. The computer program JMMSPALL is also included.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/10955613','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/10955613"><span id="translatedtitle">Sound propagation over layered poro-<span class="hlt">elastic</span> ground using a <span class="hlt">finite</span>-difference model</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Dong; Kaynia; Madshus; Hovem</p> <p>2000-08-01</p> <p>This article presents an axisymmetric pressure-velocity <span class="hlt">finite</span>-difference formulation (PV-FD) based on Biot's poro-<span class="hlt">elastic</span> theory for modeling sound propagation in a homogeneous atmosphere over layered poro-<span class="hlt">elastic</span> ground. The formulation is coded in a computer program and a simulation of actual measurements from airblast tests is carried out. The article presents typical results of simulation comprising synthetic time histories of overpressure in the atmosphere and ground vibration as well as snapshots of the response of the atmosphere-ground system at selected times. Comparisons with the measurements during airblast tests performed in Haslemoen, Norway, as well as the simulations by a frequency-wave number FFP formulation are presented to confirm the soundness of the proposed model. In particular, the generation of Mach surfaces in the ground motion, which is the result of the sound speed being greater than the Rayleigh wave velocity in the ground, is demonstrated with the help of snapshot plots. PMID:10955613</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016SPIE.9804E..26T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016SPIE.9804E..26T"><span id="translatedtitle"><span class="hlt">Finite</span> element simulation for damage detection of surface rust in steel rebars using <span class="hlt">elastic</span> waves</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Tang, Qixiang; Yu, Tzuyang</p> <p>2016-04-01</p> <p>Steel rebar corrosion reduces the integrity and service life of reinforced concrete (RC) structures and causes their gradual and sudden failures. Early stage detection of steel rebar corrosion can improve the efficiency of routine maintenance and prevent sudden failures from happening. In this paper, detecting the presence of surface rust in steel rebars is investigated by the <span class="hlt">finite</span> element method (FEM) using surface-generated <span class="hlt">elastic</span> waves. Simulated wave propagation mimics the sensing scheme of a fiber optic acoustic generator mounted on the surface of steel rebars. Formation of surface rust in steel rebars is modeled by changing material's property at local elements. In this paper, various locations of a fiber optic acoustic transducer and a receiver were considered. Megahertz <span class="hlt">elastic</span> waves were used and different sizes of surface rust were applied. Transient responses of surface displacement and pressure were studied. It is found that surface rust is most detectable when the rust location is between the transducer and the receiver. Displacement response of intact steel rebar is needed in order to obtain background-subtracted response with a better signal-to-noise ratio. When the size of surface rust increases, reduced amplitude in displacement was obtained by the receiver.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/645602','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/645602"><span id="translatedtitle">Application of equivalent <span class="hlt">elastic</span> methods in three-dimensional <span class="hlt">finite</span> element structural analysis</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Jones, D.P.; Gordon, J.L.; Hutula, D.N.; Holliday, J.E.; Jandrasits, W.G.</p> <p>1998-02-01</p> <p>This paper describes use of equivalent solid (EQS) modeling to obtain efficient solutions to perforated material problems using three-dimensional <span class="hlt">finite</span> element analysis (3D-FEA) programs. It is shown that the accuracy of EQS methods in 3D-FEA depends on providing sufficient equivalent <span class="hlt">elastic</span> properties to allow the EQS material to respond according to the <span class="hlt">elastic</span> symmetry of the pattern. Peak stresses and ligament stresses are calculated from the EQS stresses by an appropriate 3D-FEA submodel approach. The method is demonstrated on the problem of a transversely pressurized simply supported plate with a central divider lane separating two perforated regions with circular penetrations arranged in a square pattern. A 3D-FEA solution for a model that incorporates each penetration explicitly is used for comparison with results from an EQS solution for the plate. Results for deflection and stresses from the EQS solution are within 3% of results from the explicit 3D-FE model. A solution to the sample problem is also provided using the procedures in the ASME B and PV Code. The ASME B and PV Code formulas for plate deflection were shown to overestimate the stiffening effects of the divider lane and the outer stiffening ring.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AcAau.119....1A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AcAau.119....1A"><span id="translatedtitle">Bending analysis of embedded carbon nanotubes resting on an <span class="hlt">elastic</span> foundation using <span class="hlt">strain</span> gradient theory</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Akgöz, Bekir; Civalek, Ömer</p> <p>2016-02-01</p> <p>In this study, static bending response of single-walled carbon nanotubes (SWCNTs) embedded in an <span class="hlt">elastic</span> medium is investigated on the basis of higher-order shear deformation microbeam models in conjunction with modified <span class="hlt">strain</span> gradient theory. The governing differential equations and related boundary conditions are obtained by implementing a variational principle. The interactions between SWCNTs and surrounding <span class="hlt">elastic</span> medium are simulated by Winkler <span class="hlt">elastic</span> foundation model. The Navier-type solution is utilized to obtain an analytical solution for the bending problem of the simply supported embedded SWCNTs under uniform and sinusoidal loads. The influences of material length scale parameter-to-diameter ratio, slenderness ratio, loading type, shear correction factor and Winkler modulus on deflections of the embedded SWCNTs are discussed in detail. The present results illustrate that the bending behavior of SWCNTs is dependent on the small-size, stiffness of the <span class="hlt">elastic</span> foundation and also effects of shear deformation, especially for smaller slenderness ratios.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016GeoRL..43.3226R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016GeoRL..43.3226R"><span id="translatedtitle">Frequency, pressure, and <span class="hlt">strain</span> dependence of nonlinear <span class="hlt">elasticity</span> in Berea Sandstone</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Rivière, Jacques; Pimienta, Lucas; Scuderi, Marco; Candela, Thibault; Shokouhi, Parisa; Fortin, Jérôme; Schubnel, Alexandre; Marone, Chris; Johnson, Paul A.</p> <p>2016-04-01</p> <p>Acoustoelasticity measurements in a sample of room dry Berea sandstone are conducted at various loading frequencies to explore the transition between the quasi-static (f→0) and dynamic (few kilohertz) nonlinear <span class="hlt">elastic</span> response. We carry out these measurements at multiple confining pressures and perform a multivariate regression analysis to quantify the dependence of the harmonic content on <span class="hlt">strain</span> amplitude, frequency, and pressure. The modulus softening (equivalent to the harmonic at 0f) increases by a factor 2-3 over 3 orders of magnitude increase in frequency. Harmonics at 2f, 4f, and 6f exhibit similar behaviors. In contrast, the harmonic at 1f appears frequency independent. This result corroborates previous studies showing that the nonlinear <span class="hlt">elasticity</span> of rocks can be described with a minimum of two physical mechanisms. This study provides quantitative data that describes the rate dependency of nonlinear <span class="hlt">elasticity</span>. These findings can be used to improve theories relating the macroscopic <span class="hlt">elastic</span> response to microstructural features.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014IJCEM..15..422P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014IJCEM..15..422P"><span id="translatedtitle">Sensitivity Analysis of Linear <span class="hlt">Elastic</span> Cracked Structures Using Generalized <span class="hlt">Finite</span> Element Method</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Pal, Mahendra Kumar; Rajagopal, Amirtham</p> <p>2014-09-01</p> <p>In this work, a sensitivity analysis of linear <span class="hlt">elastic</span> cracked structures using two-scale Generalized <span class="hlt">Finite</span> Element Method (GFEM) is presented. The method is based on computation of material derivatives, mutual potential energies, and direct differentiation. In a computational setting, the discrete form of the mutual potential energy release rate is simple and easy to calculate, as it only requires the multiplication of the displacement vectors and stiffness sensitivity matrices. By judiciously choosing the velocity field, the method only requires displacement response in a sub-domain close to the crack tip, thus making the method computationally efficient. The method thus requires an exact computation of displacement response in a sub-domain close to the crack tip. To this end, in this study we have used a two-scale GFEM for sensitivity analysis. GFEM is based on the enrichment of the classical <span class="hlt">finite</span> element approximation. These enrichment functions incorporate the discontinuity response in the domain. Three numerical examples which comprise mode-I and mixed mode deformations are presented to evaluate the accuracy of the fracture parameters calculated by the proposed method.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2016GeoJI.206..292Z&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2016GeoJI.206..292Z&link_type=ABSTRACT"><span id="translatedtitle">A new spectral <span class="hlt">finite</span> volume method for <span class="hlt">elastic</span> wave modelling on unstructured meshes</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Zhang, Wensheng; Zhuang, Yuan; Chung, Eric T.</p> <p>2016-07-01</p> <p>In this paper, we consider a new spectral <span class="hlt">finite</span> volume method (FVM) for the <span class="hlt">elastic</span> wave equations. Our new FVM is based on a piecewise constant approximation on a fine mesh and a high-order polynomial reconstruction on a coarser mesh. Our new method is constructed based on two existing techniques, the high-order FVM and the spectral FVM. In fact, we will construct a new method to take advantage of both methods. More precisely, our method has two distinctive features. The first one is that the local polynomial reconstructions are performed on the coarse triangles and the reconstruction matrices for all the coarse triangles are the same. This fact enhances the parallelization of our algorithm. We will present a parallel implementation of our method and show excellent efficiency results. The second one is that, by using a suitable number of finer triangles with a coarse triangle, we obtain an overdetermined reconstruction system, which can enhance the robustness of the reconstruction process. To derive our scheme, standard <span class="hlt">finite</span> volume technique is applied to each fine triangle, and the high-order reconstructed polynomials, computed on coarse triangles, are used to compute numerical fluxes. We will present numerical results to show the performance of our method. Our method is presented for 2-D problems, but the same methodology can be applied to 3-D.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/27140623','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/27140623"><span id="translatedtitle"><span class="hlt">Strain</span>-enhanced stress relaxation impacts nonlinear <span class="hlt">elasticity</span> in collagen gels.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Nam, Sungmin; Hu, Kenneth H; Butte, Manish J; Chaudhuri, Ovijit</p> <p>2016-05-17</p> <p>The extracellular matrix (ECM) is a complex assembly of structural proteins that provides physical support and biochemical signaling to cells in tissues. The mechanical properties of the ECM have been found to play a key role in regulating cell behaviors such as differentiation and malignancy. Gels formed from ECM protein biopolymers such as collagen or fibrin are commonly used for 3D cell culture models of tissue. One of the most striking features of these gels is that they exhibit nonlinear <span class="hlt">elasticity</span>, undergoing <span class="hlt">strain</span> stiffening. However, these gels are also viscoelastic and exhibit stress relaxation, with the resistance of the gel to a deformation relaxing over time. Recent studies have suggested that cells sense and respond to both nonlinear <span class="hlt">elasticity</span> and viscoelasticity of ECM, yet little is known about the connection between nonlinear <span class="hlt">elasticity</span> and viscoelasticity. Here, we report that, as <span class="hlt">strain</span> is increased, not only do biopolymer gels stiffen but they also exhibit faster stress relaxation, reducing the timescale over which <span class="hlt">elastic</span> energy is dissipated. This effect is not universal to all biological gels and is mediated through weak cross-links. Mechanistically, computational modeling and atomic force microscopy (AFM) indicate that <span class="hlt">strain</span>-enhanced stress relaxation of collagen gels arises from force-dependent unbinding of weak bonds between collagen fibers. The broader effect of <span class="hlt">strain</span>-enhanced stress relaxation is to rapidly diminish <span class="hlt">strain</span> stiffening over time. These results reveal the interplay between nonlinear <span class="hlt">elasticity</span> and viscoelasticity in collagen gels, and highlight the complexity of the ECM mechanics that are likely sensed through cellular mechanotransduction. PMID:27140623</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_6");'>6</a></li> <li><a href="#" onclick='return showDiv("page_7");'>7</a></li> <li class="active"><span>8</span></li> <li><a href="#" onclick='return showDiv("page_9");'>9</a></li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_8 --> <div id="page_9" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_7");'>7</a></li> <li><a href="#" onclick='return showDiv("page_8");'>8</a></li> <li class="active"><span>9</span></li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="161"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015APS..SHK.D4005C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015APS..SHK.D4005C"><span id="translatedtitle"><span class="hlt">Elastic</span> precursor shock waves in tantalum at very high <span class="hlt">strain</span> rates</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Crowhurst, Jonathan; Armstrong, Michael; Gates, Sean; Radousky, Harry; Zaug, Joseph</p> <p>2015-06-01</p> <p>We have obtained data from micron-thick tantalum films using our ultrafast laser shock platform. By measuring free surface velocity time histories at breakout, and shock wave arrival times at different film thicknesses, we have been able to estimate the dependence of particle and shock velocities on propagation distances and <span class="hlt">strain</span> rates. We will show how <span class="hlt">elastic</span> precursor shock waves depend on <span class="hlt">strain</span> rate in the regime up to and above 109 s-1. We find that while <span class="hlt">elastic</span> amplitudes are very large at very early times decay occurs rapidly as propagation distance increases. Finally we will consider the prospects for using these data to obtain the dynamic strength of tantalum at these very high <span class="hlt">strain</span> rates. This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract No. DE-AC52-07NA27344 with Laboratory directed Research and Development funding (12ERD042).</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015APS..MARA34002C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015APS..MARA34002C"><span id="translatedtitle"><span class="hlt">Elastic</span> precursor shock waves in tantalum at very high <span class="hlt">strain</span> rates</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Crowhurst, Jonathan; Armstrong, Michael; Radousky, Harry; Zaug, Joseph; Gates, Sean</p> <p>2015-03-01</p> <p>We have obtained data from micron-thick tantalum films using our ultrafast laser shock platform. By measuring free surface velocity time histories at breakout, and shock wave arrival times at different film thicknesses, we have been able to estimate the dependence of particle and shock velocities on propagation distances and <span class="hlt">strain</span> rates. We will show how <span class="hlt">elastic</span> precursor shock waves depend on <span class="hlt">strain</span> rate in the regime up to and above 109 s-1. We find that while <span class="hlt">elastic</span> amplitudes are very large at very early times decay occurs rapidly as propagation distance increases. Finally we will consider the prospects for using these data to obtain the dynamic strength of tantalum at these very high <span class="hlt">strain</span> rates. This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract No. DE-AC52-07NA27344 with Laboratory directed Research and Development funding (12ERD042).</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/16686414','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/16686414"><span id="translatedtitle">Biotelemetric passive sensor injected within tendon for <span class="hlt">strain</span> and <span class="hlt">elasticity</span> measurement.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Pichorim, Sérgio Francisco; Abatti, Paulo José</p> <p>2006-05-01</p> <p>A passive and injectable (using hypodermic needle) biotelemetric sensor for measurements of tendon length changes has been developed. From these measurements tendon <span class="hlt">strain</span> and Young's modulus of <span class="hlt">elasticity</span> can be derived. The sensor (about 2.1 x 29 mm) is a LC circuit fixed in tendon by metallic anchors (barbs), where the value of the resonance frequency is modulated by displacement of a mobile ferrite core. The sensor was injected into digital extensor tendon of pig, allowing the determination of its stress-<span class="hlt">strain</span> curve and, consequently, of Young's modulus of <span class="hlt">elasticity</span> of the tendon. Practical results, such as sensitivity of 18.199 kHz/mm (correlation coefficient of 0.9891) for <span class="hlt">strains</span> up to 5.17%, mechanical hysteresis of 6.5%, and Young's modulus of 0.9146 GPa for a pig tendon (post mortem), are presented and discussed. PMID:16686414</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2008JCoAM.221..234B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2008JCoAM.221..234B"><span id="translatedtitle">Dual mixed <span class="hlt">finite</span> element methods for the <span class="hlt">elasticity</span> problem with Lagrange multipliers</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Boulaajine, L.; Nicaise, S.; Paquet, L.; Rafilipojaona</p> <p>2008-11-01</p> <p>We study a dual mixed formulation of the <span class="hlt">elasticity</span> system in a polygonal domain of the plane with mixed boundary conditions and its numerical approximation. The (essential) Neumann boundary conditions (or traction boundary condition) are imposed using a discontinuous Lagrange multiplier corresponding to the trace of the displacement field. Moreover, a <span class="hlt">strain</span> tensor is introduced as a new unknown and its symmetry is relaxed, also by the use of a Lagrange multiplier (the rotation). The singular behaviour of the solution requires us to use refined meshes to restore optimal rates of convergence. Uniform error estimates in the Lamé coefficient [lambda] are obtained for large [lambda]. The hybridization of the problem is performed and numerical tests are presented confirming our theoretical results.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016CompM.tmp...26G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016CompM.tmp...26G"><span id="translatedtitle">On the modelling of complex kinematic hardening and nonquadratic anisotropic yield criteria at <span class="hlt">finite</span> <span class="hlt">strains</span>: application to sheet metal forming</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Grilo, Tiago J.; Vladimirov, Ivaylo N.; Valente, Robertt A. F.; Reese, Stefanie</p> <p>2016-02-01</p> <p>In the present paper, a <span class="hlt">finite</span> <span class="hlt">strain</span> model for complex combined isotropic-kinematic hardening is presented. It accounts for <span class="hlt">finite</span> <span class="hlt">elastic</span> and <span class="hlt">finite</span> plastic <span class="hlt">strains</span> and is suitable for any anisotropic yield criterion. In order to model complex cyclic hardening phenomena, the kinematic hardening is described by several back stress components. To that end, a new procedure is proposed in which several multiplicative decompositions of the plastic part of the deformation gradient are considered. The formulation incorporates a completely general format of the yield function, which means that any yield function can by employed by following a procedure that ensures the principle of material frame indifference. The constitutive equations are derived in a thermodynamically consistent way and numerically integrated by means of a backward-Euler algorithm based on the exponential map. The performance of the constitutive model is assessed via numerical simulations of industry-relevant sheet metal forming processes (U-channel forming and draw/re-draw of a panel benchmarks), the results of which are compared to experimental data. The comparison between numerical and experimental results shows that the use of multiple back stress components is very advantageous in the description of springback. This holds in particular if one carries out a comparison with the results of using only one component. Moreover, the numerically obtained results are in excellent agreement with the experimental data.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2016CompM..57..931G&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2016CompM..57..931G&link_type=ABSTRACT"><span id="translatedtitle">On the modelling of complex kinematic hardening and nonquadratic anisotropic yield criteria at <span class="hlt">finite</span> <span class="hlt">strains</span>: application to sheet metal forming</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Grilo, Tiago J.; Vladimirov, Ivaylo N.; Valente, Robertt A. F.; Reese, Stefanie</p> <p>2016-06-01</p> <p>In the present paper, a <span class="hlt">finite</span> <span class="hlt">strain</span> model for complex combined isotropic-kinematic hardening is presented. It accounts for <span class="hlt">finite</span> <span class="hlt">elastic</span> and <span class="hlt">finite</span> plastic <span class="hlt">strains</span> and is suitable for any anisotropic yield criterion. In order to model complex cyclic hardening phenomena, the kinematic hardening is described by several back stress components. To that end, a new procedure is proposed in which several multiplicative decompositions of the plastic part of the deformation gradient are considered. The formulation incorporates a completely general format of the yield function, which means that any yield function can by employed by following a procedure that ensures the principle of material frame indifference. The constitutive equations are derived in a thermodynamically consistent way and numerically integrated by means of a backward-Euler algorithm based on the exponential map. The performance of the constitutive model is assessed via numerical simulations of industry-relevant sheet metal forming processes (U-channel forming and draw/re-draw of a panel benchmarks), the results of which are compared to experimental data. The comparison between numerical and experimental results shows that the use of multiple back stress components is very advantageous in the description of springback. This holds in particular if one carries out a comparison with the results of using only one component. Moreover, the numerically obtained results are in excellent agreement with the experimental data.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/27402932','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/27402932"><span id="translatedtitle">Large <span class="hlt">elastic</span> <span class="hlt">strain</span> and elastocaloric effect caused by lattice softening in an iron-palladium alloy.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Kakeshita, Tomoyuki; Xiao, Fei; Fukuda, Takashi</p> <p>2016-08-13</p> <p>A Fe-31.2Pd (at.%) alloy exhibits a weak first-order martensitic transformation from a cubic structure to a tetragonal structure near 230 K. This transformation is associated with significant softening of <span class="hlt">elastic</span> constant C'. Because of the softening, the alloy shows a large <span class="hlt">elastic</span> <span class="hlt">strain</span> of more than 6% in the [001] direction. In addition, the alloy has a critical point and shows a high elastocaloric effect in a wide temperature range for both the parent and the martensite phases.This article is part of the themed issue 'Taking the temperature of phase transitions in cool materials'. PMID:27402932</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/22280602','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/22280602"><span id="translatedtitle"><span class="hlt">Elastic</span> <span class="hlt">strains</span> at interfaces in InAs/AlSb multilayer structures for quantum cascade lasers</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Nicolai, J.; Gatel, Ch.; Warot-Fonrose, B.; Ponchet, A.; Teissier, R.; Baranov, A. N.; Magen, C.</p> <p>2014-01-20</p> <p>InAs/AlSb multilayers similar to those used in quantum cascade lasers have been grown by molecular beam epitaxy on (001) InAs substrates. <span class="hlt">Elastic</span> <span class="hlt">strain</span> is investigated by high resolution transmission electron microscopy. Thin interfacial regions with lattice distortions significantly different from the <span class="hlt">strain</span> of the AlSb layers themselves are revealed from the geometrical phase analysis. <span class="hlt">Strain</span> profiles are qualitatively compared to the chemical contrast of high angle annular dark field images obtained by scanning transmission electron microscopy. The <span class="hlt">strain</span> and chemical profiles are correlated with the growth sequences used to form the interfaces. Tensile <span class="hlt">strained</span> AlAs-like interfaces tend to form predominantly due to the high thermal stability of AlAs. Strongly asymmetric interfaces, AlAs-rich and (Al, In)Sb, respectively, can also be achieved by using appropriate growth sequences.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/26211247','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/26211247"><span id="translatedtitle">[Three-dimensional <span class="hlt">Finite</span> Element Analysis of Biomechanical Effect of Rigid Fixation and <span class="hlt">Elastic</span> Fixation on Lumbar Interbody Fusion].</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Wei, Jiangbo; Song, Yueming; Liu, Limin; Zhou, Chunguan; Yang, Xi</p> <p>2015-04-01</p> <p>This study was aimed to compare the mechanical characteristics under different physiological load conditions with three-dimensional <span class="hlt">finite</span> element model of rigid fixation and <span class="hlt">elastic</span> fixation in the lumbar. We observed the stress distribution characteristics of a sample of healthy male volunteer modeling under vertical, flexion and extension torque situation. The outcomes showed that there existed 4-6 times pressure on the connecting rod of rigid fixation compared with the <span class="hlt">elastic</span> fixations under different loads, and the stress peak and area of force on <span class="hlt">elastic</span> fixation were much higher than that of the rigid fixations. The <span class="hlt">elastic</span> fixation has more biomechanical advantages than rigid fixation in promoting interbody lumbar fusion after surgery. PMID:26211247</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/11737110','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/11737110"><span id="translatedtitle">Anisotropic <span class="hlt">elasticity</span> of cortical and cancellous bone in the posterior mandible increases peri-implant stress and <span class="hlt">strain</span> under oblique loading.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>O'Mahony, A M; Williams, J L; Spencer, P</p> <p>2001-12-01</p> <p>The aim of this study was to compare implant-bone interface stresses and peri-implant principal <span class="hlt">strains</span> in anisotropic versus isotropic three-dimensional <span class="hlt">finite</span> element models of an osseointegrated implant in the posterior mandible. We obtained anisotropic (transversely isotropic) <span class="hlt">elastic</span> constants for mandibular bone and derived equivalent isotropic constants by averaging over all possible spatial orientations. A <span class="hlt">finite</span> element model was constructed using ten-node tetrahedral p-elements, providing curved edges where necessary and increasing the accuracy of the results in regions of high stress gradients. Perfect bonding was assumed at the implant-bone interface. An oblique load was applied at the coronal aspect of the crown with 100 N vertical and 20 N bucco-to-lingual components. Implant-bone interface stresses exceeded reported bond strengths and principal <span class="hlt">strains</span> reached yield <span class="hlt">strain</span> levels in the cortical crest. Anisotropy increased what were already high levels of stress and <span class="hlt">strain</span> in the isotropic case by 20 to 30% in the cortical crest. In cancellous bone, anisotropy increased what were relatively low levels of interface stress in the isotropic case by three- to four-fold to exceed bond strength levels. Anisotropy has subtle, yet significant effects on interface stresses and peri-implant <span class="hlt">strains</span> and careful consideration should be given to its use in <span class="hlt">finite</span> element studies of dental implants. PMID:11737110</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/26240030','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/26240030"><span id="translatedtitle">Stress and <span class="hlt">strain</span> distribution in demineralized enamel: A micro-CT based <span class="hlt">finite</span> element study.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Neves, Aline Almeida; Coutinho, Eduardo; Alves, Haimon Diniz Lopes; de Assis, Joaquim Teixeira</p> <p>2015-10-01</p> <p>Physiological oral mechanical forces may play a role on the progression of enamel carious lesions to cavitation. Thus, the aim of this study was to describe, by 3D <span class="hlt">finite</span> element analysis, stress, and <span class="hlt">strain</span> patterns in sound and carious enamel after a simulated occlusal load. Micro-CT based models were created and meshed with tetrahedral elements (based on an extracted third molar), namely: a sound (ST) and a carious tooth (CT). For the CT, enamel material properties were assigned according to the micro-CT gray values. Below the threshold corresponding to the enamel lesion (2.5 g/cm(3) ) lower and isotropic <span class="hlt">elastic</span> modulus was assigned (E = 18 GPa against E1  = 80 GPa, E2  = E3  = 20 GPa for sound enamel). Both models were imported into a FE solver where boundary conditions were assigned and a pressure load (500 MPa) was applied at the occlusal surface. A linear static analysis was performed, considering anisotropy in sound enamel. ST showed a more efficient transfer of maximum principal stress from enamel to the dentin layer, while for the CT, enamel layer was subjected to higher and concentrated loads. Maximum principal <span class="hlt">strain</span> distributions were seen at the carious enamel surface, especially at the central fossa, correlating to the enamel cavity seen at the original micro-CT model. It is possible to conclude that demineralized enamel compromises appropriate stress transfer from enamel to dentin, contributing to the odds of fracture and cavitation. Enamel fracture over a dentin lesion may happen as one of the normal pathways to caries progression and may act as a confounding factor during clinical diagnostic decisions. PMID:26240030</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2006MMTA...37.3629P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2006MMTA...37.3629P"><span id="translatedtitle">Synchrotron X-ray measurement and <span class="hlt">finite</span> element analysis of residual <span class="hlt">strain</span> in tungsten inert gas welded aluminum alloy 2024</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Preston, R. V.; Shercliff, H. R.; Withers, P. J.; Hughes, D. J.; Smith, S. D.; Webster, P. J.</p> <p>2006-12-01</p> <p>Residual <span class="hlt">strains</span> have been measured in a tungsten inert gas (TIG) butt-welded 2024 aluminum alloy plate using synchrotron X-ray diffraction. Novel two-dimensional <span class="hlt">strain</span> maps spanning the entire plate reveal steep gradients in residual stress and provide detailed validation data for <span class="hlt">finite</span> element (FE) analysis. Two variants of a FE model have been used to predict the residual <span class="hlt">strain</span> distributions, incorporating different levels of plate constraint. The model uses decoupled thermal and <span class="hlt">elastic</span>-plastic mechanical analyses and successfully predicts the longitudinal and transverse residual <span class="hlt">strain</span> field over the entire weld. For butt weld geometries, the degree of transverse constraint is shown to be a significant boundary condition, compared to simpler bead-on-plate analyses. The importance of transverse residual <span class="hlt">strains</span> for detailed model validation is highlighted, together with the need for care in selecting the location for line scans. The residual stress is largest in the heat-affected zone (HAZ), being equal to the local postweld yield stress, though the strength increases subsequently by natural aging. In addition, a halving of the diffraction line width has been observed local to the weld, and this correlates with the microstructural changes in the region.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013FrME....8..181M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013FrME....8..181M"><span id="translatedtitle">A model for creep life prediction of thin tube using <span class="hlt">strain</span> energy density as a function of stress triaxiality under quasistatic loading employing <span class="hlt">elastic</span>-creep & <span class="hlt">elastic</span>-plastic-creep deformation</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Mahmood, Tahir; Kanapathipillai, Sangarapillai; Chowdhury, Mahiuddin</p> <p>2013-06-01</p> <p>This paper demonstrates the application of a new multiaxial creep damage model developed by authors using stress traixiality to predict the failure time of a component made of 0.5%Cr-0.5%Mo-0.25%V low alloy steel. The model employs <span class="hlt">strain</span> energy density and assumes that the uniaxial <span class="hlt">strain</span> energy density of a component can be easily calculated and can be converted to multi-axial <span class="hlt">strain</span> energy density by multiplying it to a function of stress trixiality which is a ratio of mean stress to equivalent stress. For comparison, an <span class="hlt">elastic</span>-creep and <span class="hlt">elastic</span>-plastic-creep <span class="hlt">finite</span> element analysis (FEA) is performed to get multi-axial <span class="hlt">strain</span> energy density of the component which is compared with the calculated <span class="hlt">strain</span> energy density for both cases. The verification and application of the model are demonstrated by applying it to thin tube for which the experimental data are available. The predicted failure times by the model are compared with the experimental results. The results show that the proposed model is capable of predicting failure times of the component made of the above-mentioned material with an accuracy of 4.0%.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015CompM..55..673A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015CompM..55..673A"><span id="translatedtitle">A semi-implicit <span class="hlt">finite</span> <span class="hlt">strain</span> shell algorithm using in-plane <span class="hlt">strains</span> based on least-squares</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Areias, P.; Rabczuk, T.; de Sá, J. César; Natal Jorge, R.</p> <p>2015-04-01</p> <p>The use of a semi-implicit algorithm at the constitutive level allows a robust and concise implementation of low-order effective shell elements. We perform a semi-implicit integration in the stress update algorithm for <span class="hlt">finite</span> <span class="hlt">strain</span> plasticity: rotation terms (highly nonlinear trigonometric functions) are integrated explicitly and correspond to a change in the (in this case evolving) reference configuration and relative Green-Lagrange <span class="hlt">strains</span> (quadratic) are used to account for change in the equilibrium configuration implicitly. We parametrize both reference and equilibrium configurations, in contrast with the so-called objective stress integration algorithms which use a common configuration. A <span class="hlt">finite</span> <span class="hlt">strain</span> quadrilateral element with least-squares assumed in-plane shear <span class="hlt">strains</span> (in curvilinear coordinates) and classical transverse shear assumed <span class="hlt">strains</span> is introduced. It is an alternative to enhanced-assumed-<span class="hlt">strain</span> (EAS) formulations and, contrary to this, produces an element satisfying ab-initio the Patch test. No additional degrees-of-freedom are present, contrasting with EAS. Least-squares fit allows the derivation of invariant <span class="hlt">finite</span> <span class="hlt">strain</span> elements which are both in-plane and out-of-plane shear-locking free and amenable to standardization in commercial codes. Two thickness parameters per node are adopted to reproduce the Poisson effect in bending. Metric components are fully deduced and exact linearization of the shell element is performed. Both isotropic and anisotropic behavior is presented in elasto-plastic and hyperelastic examples.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/957782','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/957782"><span id="translatedtitle">Defect-induced incompatability of <span class="hlt">elastic</span> <span class="hlt">strains</span>: dislocations within the Landau theory of martensitic phase transformations</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Groger, Roman1; Lockman, Turab; Saxena, Avadh</p> <p>2008-01-01</p> <p>In dislocation-free martensites the components of the <span class="hlt">elastic</span> <span class="hlt">strain</span> tensor are constrained by the Saint-Venant compatibility condition which guarantees continuity of the body during external loading. However, in dislocated materials the plastic part of the distortion tensor introduces a displacement mismatch that is removed by <span class="hlt">elastic</span> relaxation. The <span class="hlt">elastic</span> <span class="hlt">strains</span> are then no longer compatible in the sense of the Saint-Venant law and the ensuing incompatibility tensor is shown to be proportional to the gradients of the Nye dislocation density tensor. We demonstrate that the presence of this incompatibility gives rise to an additional long-range contribution in the inhomogeneous part of the Landau energy functional and to the corresponding stress fields. Competition among the local and long-range interactions results in frustration in the evolving order parameter (<span class="hlt">elastic</span>) texture. We show how the Peach-Koehler forces and stress fields for any distribution of dislocations in arbitrarily anisotropic media can be calculated and employed in a Fokker-Planck dynamics for the dislocation density. This approach represents a self-consistent scheme that yields the evolutions of both the order parameter field and the continuous dislocation density. We illustrate our method by studying the effects of dislocations on microstructure, particularly twinned domain walls, in an Fe-Pd alloy undergoing a martensitic transformation.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/687523','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/687523"><span id="translatedtitle">Application of equivalent <span class="hlt">elastic</span> methods in three-dimensional <span class="hlt">finite</span> element structural analysis</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Jones, D.P.; Gordon, J.L.; Hutula, D.N.; Holliday, J.E.; Jandrasits, W.G.</p> <p>1999-08-01</p> <p>This paper describes use of equivalent solid (EQS) modeling to obtain efficient solutions to perforated material problems using three-dimensional <span class="hlt">finite</span> element analysis (3-D-FEA) programs. It is shown that EQS modeling in 3-D-FEA requires an EQS constitutive relationship with a sufficient number of independent constants to allow the EQS material to respond according to the <span class="hlt">elastic</span> symmetry of the penetration pattern. It is also shown that a 3-D-FEA submodel approach to calculate peak stresses and ligament stresses from EQS results is very accurate and preferred over more traditional stress multiplier approaches. The method is demonstrated on the problem of a transversely pressurized simply supported plate with a central divider lane separating two perforated regions with circular penetrations arranged in a square pattern. A 3-D-FEA solution for a model that incorporates each penetration explicitly is used for comparison with results from an EQS solution for the plate. Results for deflection and stresses from the EQS solution are within 3% of results from the explicit 3-D-FE model. A solution to the sample problem is also provided using the procedures in the ASME B and PV Code. The ASME B and PV Code formulas for plate deflection were shown to overestimate the stiffening effects of the divider lane and the outer stiffening ring.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/1156935','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/1156935"><span id="translatedtitle">A 3D Orthotropic <span class="hlt">Strain</span>-Rate Dependent <span class="hlt">Elastic</span> Damage Material Model.</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>English, Shawn Allen</p> <p>2014-09-01</p> <p>A three dimensional orthotropic <span class="hlt">elastic</span> constitutive model with continuum damage and cohesive based fracture is implemented for a general polymer matrix composite lamina. The formulation assumes the possibility of distributed (continuum) damage followed b y localized damage. The current damage activation functions are simply partially interactive quadratic <span class="hlt">strain</span> criteria . However, the code structure allows for changes in the functions without extraordinary effort. The material model formulation, implementation, characterization and use cases are presented.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009SPIE.7292E..0SM','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009SPIE.7292E..0SM"><span id="translatedtitle">High-fidelity conical piezoelectric transducers and <span class="hlt">finite</span> element models utilized to quantify <span class="hlt">elastic</span> waves generated from ball collisions</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>McLaskey, Gregory C.; Glaser, Steven D.</p> <p>2009-03-01</p> <p>Experimental studies were performed using high-fidelity broadband Glaser-NIST conical transducers to quantify stress waves produced by the <span class="hlt">elastic</span> collision of a tiny ball and a massive plate. These sensors are sensitive to surface-normal displacements down to picometers in amplitude, in a frequency range of 20 kHz to over 1 MHz. Both the collision and the resulting transient <span class="hlt">elastic</span> waves are modeled with the <span class="hlt">finite</span> element program ABAQUS and described theoretically through a marriage of the Hertz theory of contact and a full elastodynamic Green's function found using generalized ray theory. The calculated displacements were compared to those measured through the Glaser-NIST sensors.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/27093600','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/27093600"><span id="translatedtitle">Local, atomic-level <span class="hlt">elastic</span> <span class="hlt">strain</span> measurements of metallic glass thin films by electron diffraction.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Ebner, C; Sarkar, R; Rajagopalan, J; Rentenberger, C</p> <p>2016-06-01</p> <p>A novel technique is used to measure the atomic-level <span class="hlt">elastic</span> <span class="hlt">strain</span> tensor of amorphous materials by tracking geometric changes of the first diffuse ring of selected area electron diffraction patterns (SAD). An automatic procedure, which includes locating the centre and fitting an ellipse to the diffuse ring with sub-pixel precision is developed for extracting the 2-dimensional <span class="hlt">strain</span> tensor from the SAD patterns. Using this technique, atomic-level principal <span class="hlt">strains</span> from micrometre-sized regions of freestanding amorphous Ti0.45Al0.55 thin films were measured during in-situ TEM tensile deformation. The thin films were deformed using MEMS based testing stages that allow simultaneous measurement of the macroscopic stress and <span class="hlt">strain</span>. The calculated atomic-level principal <span class="hlt">strains</span> show a linear dependence on the applied stress, and good correspondence with the measured macroscopic <span class="hlt">strains</span>. The calculated Poisson's ratio of 0.23 is reasonable for brittle metallic glasses. The technique yields a <span class="hlt">strain</span> accuracy of about 1×10(-4) and shows the potential to obtain localized <span class="hlt">strain</span> profiles/maps of amorphous thin film samples. PMID:27093600</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016PhRvB..93x5107S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016PhRvB..93x5107S"><span id="translatedtitle">Unified ab initio formulation of flexoelectricity and <span class="hlt">strain</span>-gradient <span class="hlt">elasticity</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Stengel, Massimiliano</p> <p>2016-06-01</p> <p>The theory of flexoelectricity and that of nonlocal <span class="hlt">elasticity</span> are closely related, and are often considered together when modeling <span class="hlt">strain</span>-gradient effects in solids. Here I show, based on a first-principles lattice-dynamical analysis, that their relationship is much more intimate than previously thought, and their consistent simultaneous treatment is crucial for obtaining correct physical answers. In particular, I identify a gauge invariance in the theory, whereby the energies associated to <span class="hlt">strain</span>-gradient <span class="hlt">elasticity</span> and flexoelectrically induced electric fields are individually reference dependent, and only when summed up they yield a well-defined result. To illustrate this, I construct a minimal thermodynamic functional incorporating <span class="hlt">strain</span>-gradient effects, and establish a formal link between the continuum description and ab initio phonon dispersion curves to calculate the relevant tensor quantities. As a practical demonstration, I apply such a formalism to bulk SrTiO3, where I find an unusually strong contribution of nonlocal <span class="hlt">elasticity</span>, mediated by the interaction between the ferroelectric soft mode and the transverse acoustic branches. These results have important implications towards the construction of well-defined thermodynamic theories where flexoelectricity and ferroelectricity coexist. More generally, they open exciting new avenues for the implementation of hierarchical multiscale concepts in the first-principles simulation of crystalline insulators.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_7");'>7</a></li> <li><a href="#" onclick='return showDiv("page_8");'>8</a></li> <li class="active"><span>9</span></li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_9 --> <div id="page_10" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_8");'>8</a></li> <li><a href="#" onclick='return showDiv("page_9");'>9</a></li> <li class="active"><span>10</span></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="181"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/944324','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/944324"><span id="translatedtitle">A stable <span class="hlt">finite</span> difference method for the <span class="hlt">elastic</span> wave equation on complex geometries with free surfaces</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Appelo, D; Petersson, N A</p> <p>2007-12-17</p> <p>The isotropic <span class="hlt">elastic</span> wave equation governs the propagation of seismic waves caused by earthquakes and other seismic events. It also governs the propagation of waves in solid material structures and devices, such as gas pipes, wave guides, railroad rails and disc brakes. In the vast majority of wave propagation problems arising in seismology and solid mechanics there are free surfaces. These free surfaces have, in general, complicated shapes and are rarely flat. Another feature, characterizing problems arising in these areas, is the strong heterogeneity of the media, in which the problems are posed. For example, on the characteristic length scales of seismological problems, the geological structures of the earth can be considered piecewise constant, leading to models where the values of the <span class="hlt">elastic</span> properties are also piecewise constant. Large spatial contrasts are also found in solid mechanics devices composed of different materials welded together. The presence of curved free surfaces, together with the typical strong material heterogeneity, makes the design of stable, efficient and accurate numerical methods for the <span class="hlt">elastic</span> wave equation challenging. Today, many different classes of numerical methods are used for the simulation of <span class="hlt">elastic</span> waves. Early on, most of the methods were based on <span class="hlt">finite</span> difference approximations of space and time derivatives of the equations in second order differential form (displacement formulation), see for example [1, 2]. The main problem with these early discretizations were their inability to approximate free surface boundary conditions in a stable and fully explicit manner, see e.g. [10, 11, 18, 20]. The instabilities of these early methods were especially bad for problems with materials with high ratios between the P-wave (C{sub p}) and S-wave (C{sub s}) velocities. For rectangular domains, a stable and explicit discretization of the free surface boundary conditions is presented in the paper [17] by Nilsson et al. In summary</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19740006477','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19740006477"><span id="translatedtitle"><span class="hlt">Finite</span> element stress analysis of polymers at high <span class="hlt">strains</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Durand, M.; Jankovich, E.</p> <p>1973-01-01</p> <p>A numerical analysis is presented for the problem of a flat rectangular rubber membrane with a circular rigid inclusion undergoing high <span class="hlt">strains</span> due to the action of an axial load. The neo-hookean constitutive equations are introduced into the general purpose TITUS program by means of equivalent hookean constants and initial <span class="hlt">strains</span>. The convergence is achieved after a few iterations. The method is not limited to any specific program. The results are in good agreement with those of a company sponsored photoelastic stress analysis. The theoretical and experimental deformed shapes also agree very closely with one another. For high <span class="hlt">strains</span> it is demonstrated that using the conventional HOOKE law the stress concentration factor obtained is unreliable in the case of rubberlike material.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3972043','PMC'); return false;" href="http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3972043"><span id="translatedtitle">In vivo bone <span class="hlt">strain</span> and <span class="hlt">finite</span> element modeling of the mandible of Alligator mississippiensis</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Porro, Laura B; Metzger, Keith A; Iriarte-Diaz, Jose; Ross, Callum F</p> <p>2013-01-01</p> <p>Forces experienced during feeding are thought to strongly influence the morphology of the vertebrate mandible; in vivo <span class="hlt">strain</span> data are the most direct evidence for deformation of the mandible induced by these loading regimes. Although many studies have documented bone <span class="hlt">strains</span> in the mammalian mandible, no information is available on <span class="hlt">strain</span> magnitudes, orientations or patterns in the sauropsid lower jaw during feeding. Furthermore, <span class="hlt">strain</span> gage experiments record the mechanical response of bone at a few locations, not across the entire mandible. In this paper, we present bone <span class="hlt">strain</span> data recorded at various sites on the lower jaw of Alligator mississippiensis during in vivo feeding experiments. These data are used to understand how changes in loading regime associated with changes in bite location are related to changes in <span class="hlt">strain</span> regime on the working and balancing sides of the mandible. Our results suggest that the working side mandible is bent dorsoventrally and twisted about its long-axis during biting, and the balancing side experiences primarily dorsoventral bending. <span class="hlt">Strain</span> orientations are more variable on the working side than on the balancing side with changes in bite point and between experiments; the balancing side exhibits higher <span class="hlt">strain</span> magnitudes. In the second part of this paper, we use principal <span class="hlt">strain</span> orientations and magnitudes recorded in vivo to evaluate a <span class="hlt">finite</span> element model of the alligator mandible. Our comparison demonstrates that <span class="hlt">strain</span> orientations and mandibular deformation predicted by the model closely match in vivo results; however, absolute <span class="hlt">strain</span> magnitudes are lower in the <span class="hlt">finite</span> element model. PMID:23855772</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/21920526','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/21920526"><span id="translatedtitle">Stress distributions and material properties determined in articular cartilage from MRI-based <span class="hlt">finite</span> <span class="hlt">strains</span>.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Butz, Kent D; Chan, Deva D; Nauman, Eric A; Neu, Corey P</p> <p>2011-10-13</p> <p>The noninvasive measurement of <span class="hlt">finite</span> <span class="hlt">strains</span> in biomaterials and tissues by magnetic resonance imaging (MRI) enables mathematical estimates of stress distributions and material properties. Such methods allow for non-contact and patient-specific modeling in a manner not possible with traditional mechanical testing or <span class="hlt">finite</span> element techniques. Here, we employed three constitutive (i.e. linear Hookean, and nonlinear Neo-Hookean and Mooney-Rivlin) relations with known loading conditions and MRI-based <span class="hlt">finite</span> <span class="hlt">strains</span> to estimate stress patterns and material properties in the articular cartilage of tibiofemoral joints. Displacement-encoded MRI was used to determine two-dimensional <span class="hlt">finite</span> <span class="hlt">strains</span> in juvenile porcine joints, and an iterative technique estimated stress distributions and material properties with defined constitutive relations. Stress distributions were consistent across all relations, although the stress magnitudes varied. Material properties for femoral and tibial cartilage were found to be consistent with those reported in literature. Further, the stress estimates from Hookean and Neo-Hookean, but not Mooney-Rivlin, relations agreed with <span class="hlt">finite</span> element-based simulations. A nonlinear Neo-Hookean relation provided the most appropriate model for the characterization of complex and spatially dependent stresses using two-dimensional MRI-based <span class="hlt">finite</span> <span class="hlt">strain</span>. These results demonstrate the feasibility of a new and computationally efficient technique incorporating MRI-based deformation with mathematical modeling to non-invasively evaluate the mechanical behavior of biological tissues and materials. PMID:21920526</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014JMPSo..65...93M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014JMPSo..65...93M"><span id="translatedtitle">Phase field modeling of fracture in rubbery polymers. Part I: <span class="hlt">Finite</span> <span class="hlt">elasticity</span> coupled with brittle failure</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Miehe, Christian; Schänzel, Lisa-Marie</p> <p>2014-04-01</p> <p>This work presents a new phase field model for rate-independent crack propagation in rubbery polymers at large <span class="hlt">strains</span> and considers details of its numerical implementation. The approach accounts for micro-mechanically based features of both the <span class="hlt">elastic</span> bulk response as well as the crack toughness of idealized polymer networks. The proposed diffusive crack modeling based on the introduction of a crack phase field overcomes difficulties associated with the computational realization of sharp crack discontinuities, in particular when it comes to complex crack topologies. The crack phase field governs a crack density function, which describes the macroscopic crack surface in the polymer per unit of the reference volume. It provides the basis for the constitutive modeling of a degrading free energy storage and a crack threshold function with a Griffith-type critical energy release rate, that governs the crack propagation in the polymer. Both the energy storage as well as the critical energy release due to fracture can be related to classical statistical network theories of polymers. The proposed framework of diffusive fracture in polymers is formulated in terms of a rate-type variational principle that determines the evolution of the coupled primary variable fields, i.e. the deformation field and the crack phase field. On the computational side, we outline a staggered solution procedure based on a one-pass operator split of the coupled equations, that successively updates in a typical time step the crack phase field and the displacement field. Such a solution algorithm is extremely robust, easy to implement and ideally suited for engineering problems. We finally demonstrate the performance of the phase field formulation of fracture at large <span class="hlt">strains</span> by means of representative numerical examples.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/27079489','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/27079489"><span id="translatedtitle">Experimental study and <span class="hlt">finite</span> element analysis based on equivalent load method for laser ultrasonic measurement of <span class="hlt">elastic</span> constants.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Zhan, Yu; Liu, Changsheng; Zhang, Fengpeng; Qiu, Zhaoguo</p> <p>2016-07-01</p> <p>The laser ultrasonic generation of Rayleigh surface wave and longitudinal wave in an <span class="hlt">elastic</span> plate is studied by experiment and <span class="hlt">finite</span> element method. In order to eliminate the measurement error and the time delay of the experimental system, the linear fitting method of experimental data is applied. The <span class="hlt">finite</span> element analysis software ABAQUS is used to simulate the propagation of Rayleigh surface wave and longitudinal wave caused by laser excitation on a sheet metal sample surface. The equivalent load method is proposed and applied. The pulsed laser is equivalent to the surface load in time and space domain to meet the Gaussian profile. The relationship between the physical parameters of the laser and the load is established by the correction factor. The numerical solution is in good agreement with the experimental result. The simple and effective numerical and experimental methods for laser ultrasonic measurement of the <span class="hlt">elastic</span> constants are demonstrated. PMID:27079489</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/25818950','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/25818950"><span id="translatedtitle">Development of Ti-Nb-Zr alloys with high <span class="hlt">elastic</span> admissible <span class="hlt">strain</span> for temporary orthopedic devices.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Ozan, Sertan; Lin, Jixing; Li, Yuncang; Ipek, Rasim; Wen, Cuie</p> <p>2015-07-01</p> <p>A new series of beta Ti-Nb-Zr (TNZ) alloys with considerable plastic deformation ability during compression test, high <span class="hlt">elastic</span> admissible <span class="hlt">strain</span>, and excellent cytocompatibility have been developed for removable bone tissue implant applications. TNZ alloys with nominal compositions of Ti-34Nb-25Zr, Ti-30Nb-32Zr, Ti-28Nb-35.4Zr and Ti-24.8Nb-40.7Zr (wt.% hereafter) were fabricated using the cold-crucible levitation technique, and the effects of alloying element content on their microstructures, mechanical properties (tensile strength, yield strength, compressive yield strength, Young's modulus, <span class="hlt">elastic</span> energy, toughness, and micro-hardness), and cytocompatibilities were investigated and compared. Microstructural examinations revealed that the TNZ alloys consisted of β phase. The alloy samples displayed excellent ductility with no cracking, or fracturing during compression tests. Their tensile strength, Young's modulus, elongation at rupture, and <span class="hlt">elastic</span> admissible <span class="hlt">strain</span> were measured in the ranges of 704-839 MPa, 62-65 GPa, 9.9-14.8% and 1.08-1.31%, respectively. The tensile strength, Young's modulus and elongation at rupture of the Ti-34Nb-25Zr alloy were measured as 839 ± 31.8 MPa, 62 ± 3.6 GPa, and 14.8 ± 1.6%, respectively; this alloy exhibited the <span class="hlt">elastic</span> admissible <span class="hlt">strain</span> of approximately 1.31%. Cytocompatibility tests indicated that the cell viability ratios (CVR) of the alloys are greater than those of the control group; thus the TNZ alloys possess excellent cytocompatibility. PMID:25818950</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=19850029452&hterms=Factor+AF2&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3DFactor%2BAF2','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=19850029452&hterms=Factor+AF2&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3DFactor%2BAF2"><span id="translatedtitle">Strainrange partitioning - A total <span class="hlt">strain</span> range version. [for creep fatigue life prediction by summing inelastic and <span class="hlt">elastic</span> <span class="hlt">strain</span>-range-life relations for two Ni base superalloys</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Halford, G. R.; Saltsman, J. F.</p> <p>1983-01-01</p> <p>Procedures are presented for expressing the Strainrange Partitioning (SRP) method for creep fatigue life prediction in terms of total <span class="hlt">strain</span> range. Inelastic and <span class="hlt">elastic</span> <span class="hlt">strain</span>-range - life relations are summed to give total <span class="hlt">strain</span>-range - life relations. The life components due to inelastic <span class="hlt">strains</span> are dealt with using conventional SRP procedures while the life components due to <span class="hlt">elastic</span> <span class="hlt">strains</span> are expressed as families of time-dependent terms for each type of SRP cycle. Cyclic constitutive material behavior plays an important role in establishing the <span class="hlt">elastic</span> <span class="hlt">strain</span>-range life relations as well as the partitioning of the inelastic <span class="hlt">strains</span>. To apply the approach, however, it is not necessary to have to determine the magnitude of the inelastic <span class="hlt">strain</span> range. The total <span class="hlt">strain</span> SRP approach is evaluated and verified using two nickel base superalloys, AF2-1DA and Rene 95. Excellent agreement is demonstrated between observed and predicted cyclic lifetimes with 70 to 80 percent of the predicted lives falling within factors of two of the observed lives. The total <span class="hlt">strain</span>-range SRP approach should be of considerable practical value to designers who are faced with creep-fatigue problems for which the inelastic <span class="hlt">strains</span> cannot be calculated with sufficient accuracy to make reliable life predictions by the conventional inelastic <span class="hlt">strain</span> range SRP approach.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016JCoPh.305...44R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016JCoPh.305...44R"><span id="translatedtitle">Non-conforming curved <span class="hlt">finite</span> element schemes for time-dependent <span class="hlt">elastic</span>-acoustic coupled problems</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Rodríguez-Rozas, Ángel; Diaz, Julien</p> <p>2016-01-01</p> <p>High-order numerical methods for solving time-dependent acoustic-<span class="hlt">elastic</span> coupled problems are introduced. These methods, based on <span class="hlt">Finite</span> Element techniques, allow for a flexible coupling between the fluid and the solid domain by using non-conforming meshes and curved elements. Since characteristic waves travel at different speeds through different media, specific levels of granularity for the mesh discretization are required on each domain, making impractical a possible conforming coupling in between. Advantageously, physical domains may be independently discretized in our framework due to the non-conforming feature. Consequently, an important increase in computational efficiency may be achieved compared to other implementations based on conforming techniques, namely by reducing the total number of degrees of freedom. Differently from other non-conforming approaches proposed so far, our technique is relatively simpler and requires only a geometrical adjustment at the coupling interface at a preprocessing stage, so that no extra computations are necessary during the time evolution of the simulation. On the other hand, as an advantage of using curvilinear elements, the geometry of the coupling interface between the two media of interest is faithfully represented up to the order of the scheme used. In other words, higher order schemes are in consonance with higher order approximations of the geometry. Concerning the time discretization, we analyze both explicit and implicit schemes. These schemes are energy conserving and, for the explicit case, the stability is guaranteed by a CFL condition. In order to illustrate the accuracy and convergence of these methods, a set of representative numerical tests are presented.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015NatCo...6E8985L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015NatCo...6E8985L"><span id="translatedtitle">Giant <span class="hlt">elastic</span> tunability in <span class="hlt">strained</span> BiFeO3 near an electrically induced phase transition</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Li, Q.; Cao, Y.; Yu, P.; Vasudevan, R. K.; Laanait, N.; Tselev, A.; Xue, F.; Chen, L. Q.; Maksymovych, P.; Kalinin, S. V.; Balke, N.</p> <p>2015-11-01</p> <p><span class="hlt">Elastic</span> anomalies are signatures of phase transitions in condensed matters and have traditionally been studied using various techniques spanning from neutron scattering to static mechanical testing. Here, using band-excitation <span class="hlt">elastic</span>/piezoresponse spectroscopy, we probed sub-MHz <span class="hlt">elastic</span> dynamics of a tip bias-induced rhombohedral-tetragonal phase transition of <span class="hlt">strained</span> (001)-BiFeO3 (rhombohedral) ferroelectric thin films from ~103 nm3 sample volumes. Near this transition, we observed that the Young's modulus intrinsically softens by over 30% coinciding with two- to three-fold enhancement of local piezoresponse. Coupled with phase-field modelling, we also addressed the influence of polarization switching and mesoscopic structural heterogeneities (for example, domain walls) on the kinetics of this phase transition, thereby providing fresh insights into the morphotropic phase boundary in ferroelectrics. Furthermore, the giant electrically tunable <span class="hlt">elastic</span> stiffness and corresponding electromechanical properties observed here suggest potential applications of BiFeO3 in next-generation frequency-agile electroacoustic devices, based on the utilization of the soft modes underlying successive ferroelectric phase transitions.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/pages/biblio/1296688-frequency-pressure-strain-dependence-nonlinear-elasticity-berea-sandstone','SCIGOV-DOEP'); return false;" href="http://www.osti.gov/pages/biblio/1296688-frequency-pressure-strain-dependence-nonlinear-elasticity-berea-sandstone"><span id="translatedtitle">Frequency, pressure and <span class="hlt">strain</span> dependence of nonlinear <span class="hlt">elasticity</span> in Berea Sandstone</span></a></p> <p><a target="_blank" href="http://www.osti.gov/pages">DOE PAGESBeta</a></p> <p>Riviere, Jacques; Johnson, Paul Allan; Marone, Chris; Pimienta, Lucas; Scuderi, Marco; Candela, Thibault; Shokouhi, Parisa; Schubnel, Alexandre; Fortin, Jerome</p> <p>2016-04-14</p> <p>Acoustoelasticity measurements in a sample of room dry Berea sandstone are conducted at various loading frequencies to explore the transition between the quasi-static ( f → 0) and dynamic (few kilohertz) nonlinear <span class="hlt">elastic</span> response. We carry out these measurements at multiple confining pressures and perform a multivariate regression analysis to quantify the dependence of the harmonic content on <span class="hlt">strain</span> amplitude, frequency, and pressure. The modulus softening (equivalent to the harmonic at 0f) increases by a factor 2–3 over 3 orders of magnitude increase in frequency. Harmonics at 2f, 4f, and 6f exhibit similar behaviors. In contrast, the harmonic at 1fmore » appears frequency independent. This result corroborates previous studies showing that the nonlinear <span class="hlt">elasticity</span> of rocks can be described with a minimum of two physical mechanisms. This study provides quantitative data that describes the rate dependency of nonlinear <span class="hlt">elasticity</span>. Furthermore, these findings can be used to improve theories relating the macroscopic <span class="hlt">elastic</span> response to microstructural features.« less</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4673877','PMC'); return false;" href="http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4673877"><span id="translatedtitle">Giant <span class="hlt">elastic</span> tunability in <span class="hlt">strained</span> BiFeO3 near an electrically induced phase transition</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Li, Q; Cao, Y.; Yu, P.; Vasudevan, R. K.; Laanait, N.; Tselev, A.; Xue, F.; Chen, L. Q.; Maksymovych, P.; Kalinin, S. V.; Balke, N.</p> <p>2015-01-01</p> <p><span class="hlt">Elastic</span> anomalies are signatures of phase transitions in condensed matters and have traditionally been studied using various techniques spanning from neutron scattering to static mechanical testing. Here, using band-excitation <span class="hlt">elastic</span>/piezoresponse spectroscopy, we probed sub-MHz <span class="hlt">elastic</span> dynamics of a tip bias-induced rhombohedral−tetragonal phase transition of <span class="hlt">strained</span> (001)-BiFeO3 (rhombohedral) ferroelectric thin films from ∼103 nm3 sample volumes. Near this transition, we observed that the Young's modulus intrinsically softens by over 30% coinciding with two- to three-fold enhancement of local piezoresponse. Coupled with phase-field modelling, we also addressed the influence of polarization switching and mesoscopic structural heterogeneities (for example, domain walls) on the kinetics of this phase transition, thereby providing fresh insights into the morphotropic phase boundary in ferroelectrics. Furthermore, the giant electrically tunable <span class="hlt">elastic</span> stiffness and corresponding electromechanical properties observed here suggest potential applications of BiFeO3 in next-generation frequency-agile electroacoustic devices, based on the utilization of the soft modes underlying successive ferroelectric phase transitions. PMID:26597483</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/pages/biblio/1244194-giant-elastic-tunability-strained-bifeo3-near-electrically-induced-phase-transition','SCIGOV-DOEP'); return false;" href="http://www.osti.gov/pages/biblio/1244194-giant-elastic-tunability-strained-bifeo3-near-electrically-induced-phase-transition"><span id="translatedtitle">Giant <span class="hlt">elastic</span> tunability in <span class="hlt">strained</span> BiFeO3 near an electrically induced phase transition</span></a></p> <p><a target="_blank" href="http://www.osti.gov/pages">DOE PAGESBeta</a></p> <p>Yu, Pu; Vasudevan, Rama K.; Tselev, Alexander; Xue, Fei; Chen, Long -Qing; Maksymovych, Petro; Kalinin, Sergei V.; Balke, Nina; Li, Q.; Cao, Y.; et al</p> <p>2015-01-01</p> <p><span class="hlt">Elastic</span> anomalies are signatures of phase transitions in condensed matters and have traditionally been studied using various techniques spanning from neutron scattering to static mechanical testing. Here, using band-excitation <span class="hlt">elastic</span>/piezoresponse spectroscopy, we probed sub-MHz <span class="hlt">elastic</span> dynamics of a tip bias-induced rhombohedral–tetragonal phase transition of <span class="hlt">strained</span> (001)-BiFeO3 (rhombohedral) ferroelectric thin films from ~103 nm3 sample volumes. Near this transition, we observed that the Young's modulus intrinsically softens by over 30% coinciding with 2-3 folds enhancement of local piezoresponse. Coupled with phase-field modeling, we also addressed the influence of polarization switching and mesoscopic structural heterogeneities (e.g., domain walls) on the kinetics ofmore » this phase transition, thereby providing fresh insights into the morphotropic phase boundary (MPB) in ferroelectrics. Moreover, the giant electrically tunable <span class="hlt">elastic</span> stiffness and corresponding electromechanical properties observed here suggest potential applications of BiFeO3 in next-generation frequency-agile electroacoustic devices, based on utilization of the soft modes underlying successive ferroelectric phase transitions.« less</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/26597483','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/26597483"><span id="translatedtitle">Giant <span class="hlt">elastic</span> tunability in <span class="hlt">strained</span> BiFeO3 near an electrically induced phase transition.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Li, Q; Cao, Y; Yu, P; Vasudevan, R K; Laanait, N; Tselev, A; Xue, F; Chen, L Q; Maksymovych, P; Kalinin, S V; Balke, N</p> <p>2015-01-01</p> <p><span class="hlt">Elastic</span> anomalies are signatures of phase transitions in condensed matters and have traditionally been studied using various techniques spanning from neutron scattering to static mechanical testing. Here, using band-excitation <span class="hlt">elastic</span>/piezoresponse spectroscopy, we probed sub-MHz <span class="hlt">elastic</span> dynamics of a tip bias-induced rhombohedral-tetragonal phase transition of <span class="hlt">strained</span> (001)-BiFeO3 (rhombohedral) ferroelectric thin films from ∼10(3) nm(3) sample volumes. Near this transition, we observed that the Young's modulus intrinsically softens by over 30% coinciding with two- to three-fold enhancement of local piezoresponse. Coupled with phase-field modelling, we also addressed the influence of polarization switching and mesoscopic structural heterogeneities (for example, domain walls) on the kinetics of this phase transition, thereby providing fresh insights into the morphotropic phase boundary in ferroelectrics. Furthermore, the giant electrically tunable <span class="hlt">elastic</span> stiffness and corresponding electromechanical properties observed here suggest potential applications of BiFeO3 in next-generation frequency-agile electroacoustic devices, based on the utilization of the soft modes underlying successive ferroelectric phase transitions. PMID:26597483</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20020027541','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20020027541"><span id="translatedtitle"><span class="hlt">Finite-Strain</span> Fractional-Order Viscoelastic (FOV) Material Models and Numerical Methods for Solving Them</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Freed, Alan D.; Diethelm, Kai; Gray, Hugh R. (Technical Monitor)</p> <p>2002-01-01</p> <p>Fraction-order viscoelastic (FOV) material models have been proposed and studied in 1D since the 1930's, and were extended into three dimensions in the 1970's under the assumption of infinitesimal <span class="hlt">straining</span>. It was not until 1997 that Drozdov introduced the first <span class="hlt">finite-strain</span> FOV constitutive equations. In our presentation, we shall continue in this tradition by extending the standard, FOV, fluid and solid, material models introduced in 1971 by Caputo and Mainardi into 3D constitutive formula applicable for <span class="hlt">finite-strain</span> analyses. To achieve this, we generalize both the convected and co-rotational derivatives of tensor fields to fractional order. This is accomplished by defining them first as body tensor fields and then mapping them into space as objective Cartesian tensor fields. Constitutive equations are constructed using both variants for fractional rate, and their responses are contrasted in simple shear. After five years of research and development, we now possess a basic suite of numerical tools necessary to study <span class="hlt">finite-strain</span> FOV constitutive equations and their iterative refinement into a mature collection of material models. Numerical methods still need to be developed for efficiently solving fraction al-order integrals, derivatives, and differential equations in a <span class="hlt">finite</span> element setting where such constitutive formulae would need to be solved at each Gauss point in each element of a <span class="hlt">finite</span> model, which can number into the millions in today's analysis.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015JCoPh.295..161G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015JCoPh.295..161G"><span id="translatedtitle">Generalized Multiscale <span class="hlt">Finite</span>-Element Method (GMsFEM) for <span class="hlt">elastic</span> wave propagation in heterogeneous, anisotropic media</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Gao, Kai; Fu, Shubin; Gibson, Richard L.; Chung, Eric T.; Efendiev, Yalchin</p> <p>2015-08-01</p> <p>It is important to develop fast yet accurate numerical methods for seismic wave propagation to characterize complex geological structures and oil and gas reservoirs. However, the computational cost of conventional numerical modeling methods, such as <span class="hlt">finite</span>-difference method and <span class="hlt">finite</span>-element method, becomes prohibitively expensive when applied to very large models. We propose a Generalized Multiscale <span class="hlt">Finite</span>-Element Method (GMsFEM) for <span class="hlt">elastic</span> wave propagation in heterogeneous, anisotropic media, where we construct basis functions from multiple local problems for both the boundaries and interior of a coarse node support or coarse element. The application of multiscale basis functions can capture the fine scale medium property variations, and allows us to greatly reduce the degrees of freedom that are required to implement the modeling compared with conventional <span class="hlt">finite</span>-element method for wave equation, while restricting the error to low values. We formulate the continuous Galerkin and discontinuous Galerkin formulation of the multiscale method, both of which have pros and cons. Applications of the multiscale method to three heterogeneous models show that our multiscale method can effectively model the <span class="hlt">elastic</span> wave propagation in anisotropic media with a significant reduction in the degrees of freedom in the modeling system.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/1221548','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/1221548"><span id="translatedtitle">Generalized multiscale <span class="hlt">finite</span>-element method (GMsFEM) for <span class="hlt">elastic</span> wave propagation in heterogeneous, anisotropic media</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Gao, Kai; Fu, Shubin; Gibson, Richard L.; Chung, Eric T.; Efendiev, Yalchin</p> <p>2015-04-14</p> <p>It is important to develop fast yet accurate numerical methods for seismic wave propagation to characterize complex geological structures and oil and gas reservoirs. However, the computational cost of conventional numerical modeling methods, such as <span class="hlt">finite</span>-difference method and <span class="hlt">finite</span>-element method, becomes prohibitively expensive when applied to very large models. We propose a Generalized Multiscale <span class="hlt">Finite</span>-Element Method (GMsFEM) for <span class="hlt">elastic</span> wave propagation in heterogeneous, anisotropic media, where we construct basis functions from multiple local problems for both the boundaries and interior of a coarse node support or coarse element. The application of multiscale basis functions can capture the fine scale medium property variations, and allows us to greatly reduce the degrees of freedom that are required to implement the modeling compared with conventional <span class="hlt">finite</span>-element method for wave equation, while restricting the error to low values. We formulate the continuous Galerkin and discontinuous Galerkin formulation of the multiscale method, both of which have pros and cons. Applications of the multiscale method to three heterogeneous models show that our multiscale method can effectively model the <span class="hlt">elastic</span> wave propagation in anisotropic media with a significant reduction in the degrees of freedom in the modeling system.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/pages/biblio/1221548-generalized-multiscale-finite-element-method-gmsfem-elastic-wave-propagation-heterogeneous-anisotropic-media','SCIGOV-DOEP'); return false;" href="http://www.osti.gov/pages/biblio/1221548-generalized-multiscale-finite-element-method-gmsfem-elastic-wave-propagation-heterogeneous-anisotropic-media"><span id="translatedtitle">Generalized multiscale <span class="hlt">finite</span>-element method (GMsFEM) for <span class="hlt">elastic</span> wave propagation in heterogeneous, anisotropic media</span></a></p> <p><a target="_blank" href="http://www.osti.gov/pages">DOE PAGESBeta</a></p> <p>Gao, Kai; Fu, Shubin; Gibson, Richard L.; Chung, Eric T.; Efendiev, Yalchin</p> <p>2015-04-14</p> <p>It is important to develop fast yet accurate numerical methods for seismic wave propagation to characterize complex geological structures and oil and gas reservoirs. However, the computational cost of conventional numerical modeling methods, such as <span class="hlt">finite</span>-difference method and <span class="hlt">finite</span>-element method, becomes prohibitively expensive when applied to very large models. We propose a Generalized Multiscale <span class="hlt">Finite</span>-Element Method (GMsFEM) for <span class="hlt">elastic</span> wave propagation in heterogeneous, anisotropic media, where we construct basis functions from multiple local problems for both the boundaries and interior of a coarse node support or coarse element. The application of multiscale basis functions can capture the fine scale mediummore » property variations, and allows us to greatly reduce the degrees of freedom that are required to implement the modeling compared with conventional <span class="hlt">finite</span>-element method for wave equation, while restricting the error to low values. We formulate the continuous Galerkin and discontinuous Galerkin formulation of the multiscale method, both of which have pros and cons. Applications of the multiscale method to three heterogeneous models show that our multiscale method can effectively model the <span class="hlt">elastic</span> wave propagation in anisotropic media with a significant reduction in the degrees of freedom in the modeling system.« less</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/22465640','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/22465640"><span id="translatedtitle">Generalized Multiscale <span class="hlt">Finite</span>-Element Method (GMsFEM) for <span class="hlt">elastic</span> wave propagation in heterogeneous, anisotropic media</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Gao, Kai; Fu, Shubin; Gibson, Richard L.; Chung, Eric T.; Efendiev, Yalchin</p> <p>2015-08-15</p> <p>It is important to develop fast yet accurate numerical methods for seismic wave propagation to characterize complex geological structures and oil and gas reservoirs. However, the computational cost of conventional numerical modeling methods, such as <span class="hlt">finite</span>-difference method and <span class="hlt">finite</span>-element method, becomes prohibitively expensive when applied to very large models. We propose a Generalized Multiscale <span class="hlt">Finite</span>-Element Method (GMsFEM) for <span class="hlt">elastic</span> wave propagation in heterogeneous, anisotropic media, where we construct basis functions from multiple local problems for both the boundaries and interior of a coarse node support or coarse element. The application of multiscale basis functions can capture the fine scale medium property variations, and allows us to greatly reduce the degrees of freedom that are required to implement the modeling compared with conventional <span class="hlt">finite</span>-element method for wave equation, while restricting the error to low values. We formulate the continuous Galerkin and discontinuous Galerkin formulation of the multiscale method, both of which have pros and cons. Applications of the multiscale method to three heterogeneous models show that our multiscale method can effectively model the <span class="hlt">elastic</span> wave propagation in anisotropic media with a significant reduction in the degrees of freedom in the modeling system.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/26133455','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/26133455"><span id="translatedtitle">Phase field modelling of <span class="hlt">strain</span> induced crystal growth in an <span class="hlt">elastic</span> matrix.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Laghmach, Rabia; Candau, Nicolas; Chazeau, Laurent; Munch, Etienne; Biben, Thierry</p> <p>2015-06-28</p> <p>When a crystal phase grows in an amorphous matrix, such as a crystallisable elastomer, containing cross-links and/or entanglements, these "topological constraints" need to be pushed away from the crystal phase to allow further crystallization. The accumulation of these topological constraints in the vicinity of the crystal interface may store <span class="hlt">elastic</span> energy and affect the phase transition. To evaluate the consequences of such mechanism, we introduce a phase field model based on the Flory theory of entropic <span class="hlt">elasticity</span>. We show that the growth process is indeed sensibly affected, in particular, an exponential increase of the surface energy with the displacement of the interface is induced. This explains the formation of stable nano-crystallites as it is observed in the <span class="hlt">Strain</span> Induced Crystallization (SIC) of natural rubber. Although simple, the model developed here is able to account for many interesting features of SIC, for instance, the crystallite shapes and their sizes which depend on the applied deformation. PMID:26133455</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_8");'>8</a></li> <li><a href="#" onclick='return showDiv("page_9");'>9</a></li> <li class="active"><span>10</span></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_10 --> <div id="page_11" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_9");'>9</a></li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li class="active"><span>11</span></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="201"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015JChPh.142x4905L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015JChPh.142x4905L"><span id="translatedtitle">Phase field modelling of <span class="hlt">strain</span> induced crystal growth in an <span class="hlt">elastic</span> matrix</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Laghmach, Rabia; Candau, Nicolas; Chazeau, Laurent; Munch, Etienne; Biben, Thierry</p> <p>2015-06-01</p> <p>When a crystal phase grows in an amorphous matrix, such as a crystallisable elastomer, containing cross-links and/or entanglements, these "topological constraints" need to be pushed away from the crystal phase to allow further crystallization. The accumulation of these topological constraints in the vicinity of the crystal interface may store <span class="hlt">elastic</span> energy and affect the phase transition. To evaluate the consequences of such mechanism, we introduce a phase field model based on the Flory theory of entropic <span class="hlt">elasticity</span>. We show that the growth process is indeed sensibly affected, in particular, an exponential increase of the surface energy with the displacement of the interface is induced. This explains the formation of stable nano-crystallites as it is observed in the <span class="hlt">Strain</span> Induced Crystallization (SIC) of natural rubber. Although simple, the model developed here is able to account for many interesting features of SIC, for instance, the crystallite shapes and their sizes which depend on the applied deformation.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016InvPr..32f5002B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016InvPr..32f5002B"><span id="translatedtitle">Isotropic realizability of a <span class="hlt">strain</span> field for the two‑dimensional incompressible <span class="hlt">elasticity</span> system</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Briane, M.</p> <p>2016-06-01</p> <p>In the paper we study the problem of the isotropic realizability in {{{R}}}2 of a regular <span class="hlt">strain</span> field e(U)=\\tfrac{1}{2}({DU}+{{DU}}T) for the incompressible <span class="hlt">elasticity</span> system, namely the existence of a positive shear modulus μ \\gt 0 solving the <span class="hlt">elasticity</span> system in {{{R}}}2 with the prescribed field e(U). We show that if e(U) does not vanish at some point, then the isotropic realizability holds in the neighborhood of that point. The global realizability in {{{R}}}2 or in the torus is much more delicate, since it involves the global existence of a regular solution to a semilinear wave equation, the coefficients of which depend on the derivatives of U. Using this semilinear wave equation we prove a small perturbation result: if DU is periodic and close enough to its average value for the C 4‑norm, then the associated <span class="hlt">strain</span> field is isotropically realizable in a given disk centered at the origin. On the other hand, a counterexample shows that the global realizability in {{{R}}}2 may hold without the realizability in the torus, and it is discussed in connection with the associated semilinear wave equation. The case where the <span class="hlt">strain</span> field vanishes is illustrated by an example. The singular case of a rank-one laminate field is also investigated.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2016PhRvE..94b3003M&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2016PhRvE..94b3003M&link_type=ABSTRACT"><span id="translatedtitle">Hydrodynamic description of <span class="hlt">elastic</span> or viscoelastic composite materials: Relative <span class="hlt">strains</span> as macroscopic variables</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Menzel, Andreas M.</p> <p>2016-08-01</p> <p>One possibility to adjust material properties to a specific need is to embed units of one substance into a matrix of another substance. Even materials that are readily tunable during operation can be generated in this way. In (visco)<span class="hlt">elastic</span> substances, both the matrix material as well as the inclusions and/or their immediate environment can be dynamically deformed. If the typical dynamic response time of the inclusions and their surroundings approach the macroscopic response time, their deformation processes need to be included into a dynamic macroscopic characterization. Along these lines, we present a hydrodynamic description of (visco)<span class="hlt">elastic</span> composite materials. For this purpose, additional <span class="hlt">strain</span> variables reflect the state of the inclusions and their immediate environment. These additional <span class="hlt">strain</span> variables in general are not set by a coarse-grained macroscopic displacement field. Apart from that, during our derivation, we also include the macroscopic variables of relative translations and relative rotations that were previously introduced in different contexts. As a central point, our approach reveals and classifies the importance of a macroscopic variable termed relative <span class="hlt">strains</span>. We analyze two simplified minimal example geometries as an illustration.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016MTDM...20..139Z','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016MTDM...20..139Z"><span id="translatedtitle">Approximate analytical solution for the problem of an inclusion in a viscoelastic solid under <span class="hlt">finite</span> <span class="hlt">strains</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Zingerman, K. M.; Shavyrin, D. A.</p> <p>2016-06-01</p> <p>The approximate analytical solution of a quasi-static plane problem of the theory of viscoelasticity is obtained under <span class="hlt">finite</span> <span class="hlt">strains</span>. This is the problem of the stress-<span class="hlt">strain</span> state in an infinite body with circular viscoelastic inclusion. The perturbation technique, Laplace transform, and complex Kolosov-Muskhelishvili's potentials are used for the solution. The numerical results are presented. The nonlinear effects and the effects of viscosity are estimated.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/20634548','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/20634548"><span id="translatedtitle"><span class="hlt">Elastic</span> <span class="hlt">strain</span> tensor measurement using electron backscatter diffraction in the SEM.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Dingley, David J; Wilkinson, Angus J; Meaden, Graham; Karamched, Phani S</p> <p>2010-08-01</p> <p>The established electron backscatter diffraction (EBSD) technique for obtaining crystallographic information in the SEM has been adapted to permit <span class="hlt">elastic</span> <span class="hlt">strain</span> measurement. Basically, the displacement of crystallographic features in an EBSD pattern, such as zone axes, which result from <span class="hlt">strain</span> in a crystal, is determined by comparing those same features as they appear in a pattern from an unstrained region of the crystal. The comparison is made by cross-correlation of selected regions in the two patterns. Tests show that the sensitivity to displacement measurement is 1 part in 10 000, which translates to a <span class="hlt">strain</span> sensitivity of 2 parts in 10 000. Eight components of the <span class="hlt">strain</span> tensor are determined directly and the ninth is calculated using the fact that the free surface of the sample is traction-free. Examples discussed are taken from studies of a lenticular fracture in germanium, the <span class="hlt">strain</span> distribution surrounding a carbide precipitate in a nickel base alloy and grain boundary studies in another nickel base alloy. PMID:20634548</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4816497','PMC'); return false;" href="http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4816497"><span id="translatedtitle">Dynamic <span class="hlt">finite-strain</span> modelling of the human left ventricle in health and disease using an immersed boundary-<span class="hlt">finite</span> element method</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Gao, Hao; Carrick, David; Berry, Colin; Griffith, Boyce E.; Luo, Xiaoyu</p> <p>2016-01-01</p> <p>Detailed models of the biomechanics of the heart are important both for developing improved interventions for patients with heart disease and also for patient risk stratification and treatment planning. For instance, stress distributions in the heart affect cardiac remodelling, but such distributions are not presently accessible in patients. Biomechanical models of the heart offer detailed three-dimensional deformation, stress and <span class="hlt">strain</span> fields that can supplement conventional clinical data. In this work, we introduce dynamic computational models of the human left ventricle (LV) that are derived from clinical imaging data obtained from a healthy subject and from a patient with a myocardial infarction (MI). Both models incorporate a detailed invariant-based orthotropic description of the passive <span class="hlt">elasticity</span> of the ventricular myocardium along with a detailed biophysical model of active tension generation in the ventricular muscle. These constitutive models are employed within a dynamic simulation framework that accounts for the inertia of the ventricular muscle and the blood that is based on an immersed boundary (IB) method with a <span class="hlt">finite</span> element description of the structural mechanics. The geometry of the models is based on data obtained non-invasively by cardiac magnetic resonance (CMR). CMR imaging data are also used to estimate the parameters of the passive and active constitutive models, which are determined so that the simulated end-diastolic and end-systolic volumes agree with the corresponding volumes determined from the CMR imaging studies. Using these models, we simulate LV dynamics from enddiastole to end-systole. The results of our simulations are shown to be in good agreement with subject-specific CMR-derived <span class="hlt">strain</span> measurements and also with earlier clinical studies on human LV <span class="hlt">strain</span> distributions. PMID:27041786</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19790008473','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19790008473"><span id="translatedtitle">Three-dimensional <span class="hlt">finite</span>-element <span class="hlt">elastic</span> analysis of a thermally cycled single-edge wedge geometry specimen</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Bizon, P. T.; Hill, R. J.; Guilliams, B. P.; Drake, S. K.; Kladden, J. L.</p> <p>1979-01-01</p> <p>An <span class="hlt">elastic</span> stress analysis was performed on a wedge specimen (prismatic bar with single-wedge cross section) subjected to thermal cycles in fluidized beds. Seven different combinations consisting of three alloys (NASA TAZ-8A, 316 stainless steel, and A-286) and four thermal cycling conditions were analyzed. The analyses were performed as a joint effort of two laboratories using different models and computer programs (NASTRAN and ISO3DQ). Stress, <span class="hlt">strain</span>, and temperature results are presented.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/5489817','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/5489817"><span id="translatedtitle">Comparison of experiment and theory for <span class="hlt">elastic</span>-plastic plane <span class="hlt">strain</span> crack growth</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Hermann, L; Rice, J R</p> <p>1980-02-01</p> <p>Recent theoretical results on <span class="hlt">elastic</span>-plastic plane <span class="hlt">strain</span> crack growth, and experimental results for crack growth in a 4140 steel in terms of the theoretical concepts are reviewed. The theory is based on a recent asymptotic analysis of crack surface opening and <span class="hlt">strain</span> distributions at a quasi-statically advancing crack tip in an ideally-plastic solid. The analysis is incomplete in that some of the parameters which appear in it are known only approximately, especially at large scale yielding. Nevertheless, it suffices to derive a relation between the imposed loading and amount of crack growth, prior to general yielding, based on the assumption that a geometrically similar near-tip crack profile is maintained during growth. The resulting predictions for the variation of J with crack growth are found to fit well to the experimental results obtained on deeply cracked compact specimens.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015CompM..55..229K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015CompM..55..229K"><span id="translatedtitle">Automatic implementation of <span class="hlt">finite</span> <span class="hlt">strain</span> anisotropic hyperelastic models using hyper-dual numbers</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kiran, Ravi; Khandelwal, Kapil</p> <p>2015-01-01</p> <p>The main aim of this paper is to automate the implementation of <span class="hlt">finite</span> <span class="hlt">strain</span> anisotropic hyperelastic models into a general <span class="hlt">finite</span> element framework. The automation presented in this paper enables the end-user to implement a hyperelastic model by programming its Helmholtz free energy function alone. The automation is achieved by employing hyper-dual number system to evaluate analytical quality derivatives. New perturbation techniques are introduced and are employed to extend the hyper-dual numbers system to evaluate tensor derivatives. The capability of the proposed automation scheme is demonstrated by implementing five <span class="hlt">finite</span> <span class="hlt">strain</span> anisotropic hyperelastic models. The merits and demerits of the proposed automation scheme are compared to an automation scheme based on the central difference method.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19920005175','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19920005175"><span id="translatedtitle">A variational justification of the assumed natural <span class="hlt">strain</span> formulation of <span class="hlt">finite</span> elements</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Militello, Carmelo; Felippa, Carlos A.</p> <p>1991-01-01</p> <p>The objective is to study the assumed natural <span class="hlt">strain</span> (ANS) formulation of <span class="hlt">finite</span> elements from a variational standpoint. The study is based on two hybrid extensions of the Reissner-type functional that uses <span class="hlt">strains</span> and displacements as independent fields. One of the forms is a genuine variational principle that contains an independent boundary traction field, whereas the other one represents a restricted variational principle. Two procedures for element level elimination of the <span class="hlt">strain</span> field are discussed, and one of them is shown to be equivalent to the inclusion of incompatible displacement modes. Also, the 4-node C(exp 0) plate bending quadrilateral element is used to illustrate applications of this theory.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/25197258','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/25197258"><span id="translatedtitle">Cones of localized shear <span class="hlt">strain</span> in incompressible <span class="hlt">elasticity</span> with prestress: Green's function and integral representations.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Argani, L P; Bigoni, D; Capuani, D; Movchan, N V</p> <p>2014-09-01</p> <p>The infinite-body three-dimensional Green's function set (for incremental displacement and mean stress) is derived for the incremental deformation of a uniformly <span class="hlt">strained</span> incompressible, nonlinear <span class="hlt">elastic</span> body. Particular cases of the developed formulation are the Mooney-Rivlin <span class="hlt">elasticity</span> and the J2-deformation theory of plasticity. These Green's functions are used to develop a boundary integral equation framework, by introducing an ad hoc potential, which paves the way for a boundary element formulation of three-dimensional problems of incremental <span class="hlt">elasticity</span>. Results are used to investigate the behaviour of a material deformed near the limit of ellipticity and to reveal patterns of shear failure. In fact, within the investigated three-dimensional framework, localized deformations emanating from a perturbation are shown to be organized in conical geometries rather than in planar bands, so that failure is predicted to develop through curved and thin surfaces of intense shearing, as can for instance be observed in the cup-cone rupture of ductile metal bars. PMID:25197258</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012AcMSn..28...91N','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012AcMSn..28...91N"><span id="translatedtitle">C 1 natural element method for <span class="hlt">strain</span> gradient linear <span class="hlt">elasticity</span> and its application to microstructures</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Nie, Zhi-Feng; Zhou, Shen-Jie; Han, Ru-Jun; Xiao, Lin-Jing; Wang, Kai</p> <p>2012-02-01</p> <p>C 1 natural element method ( C 1 NEM) is applied to <span class="hlt">strain</span> gradient linear <span class="hlt">elasticity</span>, and size effects on microstructures are analyzed. The shape functions in C 1 NEM are built upon the natural neighbor interpolation (NNI), with interpolation realized to nodal function and nodal gradient values, so that the essential boundary conditions (EBCs) can be imposed directly in a Galerkin scheme for partial differential equations (PDEs). In the present paper, C 1 NEM for <span class="hlt">strain</span> gradient linear <span class="hlt">elasticity</span> is constructed, and several typical examples which have analytical solutions are presented to illustrate the effectiveness of the constructed method. In its application to microstructures, the size effects of bending stiffness and stress concentration factor (SCF) are studied for microspeciem and microgripper, respectively. It is observed that the size effects become rather strong when the width of spring for microgripper, the radius of circular perforation and the long axis of elliptical perforation for microspeciem come close to the material characteristic length scales. For the U-shaped notch, the size effects decline obviously with increasing notch radius, and decline mildly with increasing length of notch.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2004JSV...276..615P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2004JSV...276..615P"><span id="translatedtitle">Stability of <span class="hlt">elastic</span> and viscoelastic plates in a gas flow taking into account shear <span class="hlt">strains</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Potapov, V. D.</p> <p>2004-09-01</p> <p>It is well known that the internal friction in a material can have a considerable destabilizing effect on the stability of non-conservative systems. Apart from the Voigt model, the viscoelastic body model is sometimes utilized to describe material damping. This relates the stability problem for non-conservative <span class="hlt">elastic</span> systems with that for viscoelastic system. The Bubnov-Galerkin method is usually applied for solving the problems. In this case, the displacement functions are represented by series in terms of natural vibration modes ϕ i( x) of the <span class="hlt">elastic</span> system. To provide a high degree of accuracy for the solution, one should involve a fairly large number of modes. For a viscoelastic plate, the number of terms to be kept in the expansion of the deflection can be substantially more. One should bear in mind, however, that as the number of modes preserved in the expansion increases, the influence of shear <span class="hlt">strains</span> and rotational inertia on the behavior of the solution becomes more pronounced. In view of this, it is important to study the stability of non-conservative viscoelastic systems with the shear <span class="hlt">strain</span> and rotational inertia being taken into account. In the present paper this problem is solved for a viscoelastic plate in a supersonic gas flow.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2006PhyD..217..153S&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2006PhyD..217..153S&link_type=ABSTRACT"><span id="translatedtitle">Multi phase field model for solid state transformation with <span class="hlt">elastic</span> <span class="hlt">strain</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Steinbach, I.; Apel, M.</p> <p>2006-05-01</p> <p>A multi phase field model is presented for the investigation of the effect of transformation <span class="hlt">strain</span> on the transformation kinetics, morphology and thermodynamic stability in multi phase materials. The model conserves homogeneity of stress in the diffuse interface between <span class="hlt">elastically</span> inhomogeneous phases, in which respect it differs from previous models. The model is formulated consistently with the multi phase field model for diffusional and surface driven phase transitions [I. Steinbach, F. Pezzolla, B. Nestler, M. Seeßelberg, R. Prieler, G.J. Schmitz, J.L.L. Rezende, A phase field concept for multiphase systems, Physica D 94 (1996) 135-147; J. Tiaden, B. Nestler, H.J. Diepers, I. Steinbach, The multiphase-field model with an integrated concept for modeling solute diffusion, Physica D 115 (1998) 73-86; I. Steinbach, F. Pezzolla, A generalized field method for multiphase transformations using interface fields, Physica D 134 (1999) 385] and gives a consistent description of interfacial tension, multi phase thermodynamics and <span class="hlt">elastic</span> stress balance in multiple junctions between an arbitrary number of grains and phases. Some aspects of the model are demonstrated with respect to numerical accuracy and the relation between transformation <span class="hlt">strain</span>, external stress and thermodynamic equilibrium.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3668218','PMC'); return false;" href="http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3668218"><span id="translatedtitle">Computational simulation of the bone remodeling using the <span class="hlt">finite</span> element method: an <span class="hlt">elastic</span>-damage theory for small displacements</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p></p> <p>2013-01-01</p> <p>Background The resistance of the bone against damage by repairing itself and adapting to environmental conditions is its most important property. These adaptive changes are regulated by physiological process commonly called the bone remodeling. Better understanding this process requires that we apply the theory of <span class="hlt">elastic</span>-damage under the hypothesis of small displacements to a bone structure and see its mechanical behavior. Results The purpose of the present study is to simulate a two dimensional model of a proximal femur by taking into consideration <span class="hlt">elastic</span>-damage and mechanical stimulus. Here, we present a mathematical model based on a system of nonlinear ordinary differential equations and we develop the variational formulation for the mechanical problem. Then, we implement our mathematical model into the <span class="hlt">finite</span> element method algorithm to investigate the effect of the damage. Conclusion The results are consistent with the existing literature which shows that the bone stiffness drops in damaged bone structure under mechanical loading. PMID:23663260</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/2637','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/2637"><span id="translatedtitle">A Family of Uniform <span class="hlt">Strain</span> Tetrahedral Elements and a Method for Connecting Dissimilar <span class="hlt">Finite</span> Element Meshes</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Dohrmann, C.R.; Heinstein, M.W.; Jung, J.; Key, S.W.</p> <p>1999-01-01</p> <p>This report documents a collection of papers on a family of uniform <span class="hlt">strain</span> tetrahedral <span class="hlt">finite</span> elements and their connection to different element types. Also included in the report are two papers which address the general problem of connecting dissimilar meshes in two and three dimensions. Much of the work presented here was motivated by the development of the tetrahedral element described in the report "A Suitable Low-Order, Eight-Node Tetrahedral <span class="hlt">Finite</span> Element For Solids," by S. W. Key {ital et al.}, SAND98-0756, March 1998. Two basic issues addressed by the papers are: (1) the performance of alternative tetrahedral elements with uniform <span class="hlt">strain</span> and enhanced uniform <span class="hlt">strain</span> formulations, and (2) the proper connection of tetrahedral and other element types when two meshes are "tied" together to represent a single continuous domain.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/948345','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/948345"><span id="translatedtitle">On the Relationship between Stress and <span class="hlt">Elastic</span> <span class="hlt">Strain</span> for Porous and Fractured Rock</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Liu, Hui-Hai; Rutqvist, Jonny; Berryman, James G.</p> <p>2008-02-25</p> <p>Modeling the mechanical deformations of porous and fractured rocks requires a stress-<span class="hlt">strain</span> relationship. Experience with inherently heterogeneous earth materials suggests that different varieties of Hook's law should be applied within regions of the rock having significantly different stress-<span class="hlt">strain</span> behavior, e.g., such as solid phase and various void geometries. We apply this idea by dividing a rock body conceptually into two distinct parts. The natural <span class="hlt">strain</span> (volume change divided by rock volume at the current stress state), rather than the engineering <span class="hlt">strain</span> (volume change divided by the unstressed rock volume), should be used in Hooke's law for accurate modeling of the <span class="hlt">elastic</span> deformation of that part of the pore volume subject to a relatively large degree of relative deformation (i.e., cracks or fractures). This approach permits the derivation of constitutive relations between stress and a variety of mechanical and/or hydraulic rock properties. We show that the theoretical predictions of this method are generally consistent with empirical expressions (from field data) and also laboratory rock experimental data.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016PMag...96.1420L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016PMag...96.1420L"><span id="translatedtitle">Transformation-rate maxima during lath martensite formation: plastic vs. <span class="hlt">elastic</span> shape <span class="hlt">strain</span> accommodation</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Loewy, Sarah; Rheingans, Bastian; Mittemeijer, Eric J.</p> <p>2016-05-01</p> <p>Recently, a modulated formation behaviour of lath martensite in Fe-Ni(-based) alloys was observed, exhibiting a series of transformation-rate maxima. This peculiar transformation behaviour was explained on the basis of the hierarchical microstructure of lath martensite, minimising the net shape <span class="hlt">strain</span> associated with martensite formation, by a block-by-block formation of martensite packages occurring simultaneously in all packages. In the present work, the martensitic transformation upon slow cooling of two Fe-Ni alloys, containing 22 and 25 at.% of Ni, respectively, was investigated by high-resolution dilatometry with the aim of identifying the influence of alloy composition on the modulated transformation behaviour. The differences observed for the two alloys, a more rapid sequence of the transformation-rate maxima and a narrower temperature range in case of Fe-25 at.% Ni, can be explained consistently as a consequence of the lower transformation temperatures in Fe-25 at.% Ni, highlighting the role of temporary accommodation of the shape <span class="hlt">strain</span> during formation of the lath martensite microstructure: the depression of the transformation toward lower temperatures leads to a higher strength of the austenite, hence resulting in a more <span class="hlt">elastic</span> (less plastic) temporary accommodation of the shape <span class="hlt">strain</span> upon block formation and thereby in a more effective mutual compensation of the shape <span class="hlt">strain</span> by neighbouring blocks. A kinetic model on the basis of energy-change considerations is presented which is able to describe the observed modulated transformation behaviour.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2011NatNa...6..788L&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2011NatNa...6..788L&link_type=ABSTRACT"><span id="translatedtitle">Skin-like pressure and <span class="hlt">strain</span> sensors based on transparent <span class="hlt">elastic</span> films of carbon nanotubes</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Lipomi, Darren J.; Vosgueritchian, Michael; Tee, Benjamin C.-K.; Hellstrom, Sondra L.; Lee, Jennifer A.; Fox, Courtney H.; Bao, Zhenan</p> <p>2011-12-01</p> <p>Transparent, <span class="hlt">elastic</span> conductors are essential components of electronic and optoelectronic devices that facilitate human interaction and biofeedback, such as interactive electronics, implantable medical devices and robotic systems with human-like sensing capabilities. The availability of conducting thin films with these properties could lead to the development of skin-like sensors that stretch reversibly, sense pressure (not just touch), bend into hairpin turns, integrate with collapsible, stretchable and mechanically robust displays and solar cells, and also wrap around non-planar and biological surfaces such as skin and organs, without wrinkling. We report transparent, conducting spray-deposited films of single-walled carbon nanotubes that can be rendered stretchable by applying <span class="hlt">strain</span> along each axis, and then releasing this <span class="hlt">strain</span>. This process produces spring-like structures in the nanotubes that accommodate <span class="hlt">strains</span> of up to 150% and demonstrate conductivities as high as 2,200 S cm-1 in the stretched state. We also use the nanotube films as electrodes in arrays of transparent, stretchable capacitors, which behave as pressure and <span class="hlt">strain</span> sensors.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/25173237','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/25173237"><span id="translatedtitle">Determination of the <span class="hlt">elastic</span> properties of rabbit vocal fold tissue using uniaxial tensile testing and a tailored <span class="hlt">finite</span> element model.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Latifi, Neda; Miri, Amir K; Mongeau, Luc</p> <p>2014-11-01</p> <p>The aim of the present study was to quantify the effects of the specimen shape on the accuracy of mechanical properties determined from a shape-specific model generation strategy. Digital images of five rabbit vocal folds (VFs) in their initial undeformed conditions were used to build corresponding specific solid models. The displacement field of the VFs under uniaxial tensile test was then measured over the visible portion of the surface using digital image correlation. A three-dimensional <span class="hlt">finite</span> element model was built, using ABAQUS, for each solid model, while imposing measured boundary conditions. An inverse-problem method was used, assuming a homogeneous isotropic linear <span class="hlt">elastic</span> constitutive model. Unknown <span class="hlt">elastic</span> properties were identified iteratively through an error minimization technique between simulated and measured force-time data. The longitudinal <span class="hlt">elastic</span> moduli of the five rabbit VFs were calculated and compared to values from a simple analytical method and those obtained by approximating the cross-section as elliptical. The use of shape-specific models significantly reduced the standard deviation of the Young׳s moduli of the tested specimens. However, a non-parametric statistical analysis test, i.e., the Friedman test, yielded no statistically significant differences between the shape-specific method and the elliptic cylindrical <span class="hlt">finite</span> element model. Considering the required procedures to reconstruct the shape-specific <span class="hlt">finite</span> element model for each tissue specimen, it might be expedient to use the simpler method when large numbers of tissue specimens are to be compared regarding their Young׳s moduli. PMID:25173237</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_9");'>9</a></li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li class="active"><span>11</span></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_11 --> <div id="page_12" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li class="active"><span>12</span></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="221"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/24948642','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/24948642"><span id="translatedtitle">Tendon <span class="hlt">elastic</span> <span class="hlt">strain</span> energy in the human ankle plantar-flexors and its role with increased running speed.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Lai, Adrian; Schache, Anthony G; Lin, Yi-Chung; Pandy, Marcus G</p> <p>2014-09-01</p> <p>The human ankle plantar-flexors, the soleus and gastrocnemius, utilize tendon <span class="hlt">elastic</span> <span class="hlt">strain</span> energy to reduce muscle fiber work and optimize contractile conditions during running. However, studies to date have considered only slow to moderate running speeds up to 5 m s(-1). Little is known about how the human ankle plantar-flexors utilize tendon <span class="hlt">elastic</span> <span class="hlt">strain</span> energy as running speed is advanced towards maximum sprinting. We used data obtained from gait experiments in conjunction with musculoskeletal modeling and optimization techniques to calculate muscle-tendon unit (MTU) work, tendon <span class="hlt">elastic</span> <span class="hlt">strain</span> energy and muscle fiber work for the ankle plantar-flexors as participants ran at five discrete steady-state speeds ranging from jogging (~2 m s(-1)) to sprinting (≥8 m s(-1)). As running speed progressed from jogging to sprinting, the contribution of tendon <span class="hlt">elastic</span> <span class="hlt">strain</span> energy to the positive work generated by the MTU increased from 53% to 74% for the soleus and from 62% to 75% for the gastrocnemius. This increase was facilitated by greater muscle activation and the relatively isometric behavior of the soleus and gastrocnemius muscle fibers. Both of these characteristics enhanced tendon stretch and recoil, which contributed to the bulk of the change in MTU length. Our results suggest that as steady-state running speed is advanced towards maximum sprinting, the human ankle plantar-flexors continue to prioritize the storage and recovery of tendon <span class="hlt">elastic</span> <span class="hlt">strain</span> energy over muscle fiber work. PMID:24948642</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19790004293','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19790004293"><span id="translatedtitle"><span class="hlt">Elastic</span>-Plastic <span class="hlt">Finite</span> Element Analysis of Fatigue Crack Growth in Mode 1 and Mode 2 Conditions</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Nakagaki, M.; Atluri, S. N.</p> <p>1978-01-01</p> <p>Presented is an alternate cost-efficient and accurate <span class="hlt">elastic</span>-plastic <span class="hlt">finite</span> element procedure to analyze fatigue crack closure and its effects under general spectrum loading. Both Modes 1 and 2 type cycling loadings are considered. Also presented are the results of an investigation, using the newly developed procedure, of various factors that cause crack growth acceleration or retardation and delay effects under high-to-low, low-to-high, single overload, and constant amplitude type cyclic loading in a Mode 1 situation. Further, the results of an investigation of a centercracked panel under external pure shear (Mode 2) cyclic loading, of constant amplitude, are reported.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4312579','PMC'); return false;" href="http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4312579"><span id="translatedtitle"><span class="hlt">Strain</span> Amplification Analysis of an Osteocyte under Static and Cyclic Loading: A <span class="hlt">Finite</span> Element Study</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Xian, Cory J.</p> <p>2015-01-01</p> <p>Osteocytes, the major type of bone cells which reside in their lacunar and canalicular system within the bone matrix, function as biomechanosensors and biomechanotransducers of the bone. Although biomechanical behaviour of the osteocyte-lacunar-canalicular system has been investigated in previous studies mostly using computational 2-dimensional (2D) geometric models, only a few studies have used the 3-dimensional (3D) <span class="hlt">finite</span> element (FE) model. In the current study, a 3D FE model was used to predict the responses of <span class="hlt">strain</span> distributions of osteocyte-lacunar-canalicular system analyzed under static and cyclic loads. The <span class="hlt">strain</span> amplification factor was calculated for all simulations. Effects on the <span class="hlt">strain</span> of the osteocyte system were investigated under 500, 1500, 2000, and 3000 microstrain loading magnitudes and 1, 5, 10, 40, and 100 Hz loading frequencies. The maximum <span class="hlt">strain</span> was found to change with loading magnitude and frequency. It was observed that maximum <span class="hlt">strain</span> under 3000-microstrain loading was higher than those under 500, 1500, and 2000 microstrains. When the loading <span class="hlt">strain</span> reached the maximum magnitude, the <span class="hlt">strain</span> amplification factor of 100 Hz was higher than those of the other frequencies. Data from this 3D FE model study suggests that the <span class="hlt">strain</span> amplification factor of the osteocyte-lacunar-canalicular system increases with loading frequency and loading <span class="hlt">strain</span> increasing. PMID:25664319</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/22319376','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/22319376"><span id="translatedtitle">The effect of tensile hysteresis and contact resistance on the performance of <span class="hlt">strain</span>-resistant <span class="hlt">elastic</span>-conductive webbing.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Shyr, Tien-Wei; Shie, Jing-Wen; Jhuang, Yan-Er</p> <p>2011-01-01</p> <p>To use e-textiles as a <span class="hlt">strain</span>-resistance sensor they need to be both <span class="hlt">elastic</span> and conductive. Three kinds of <span class="hlt">elastic</span>-conductive webbings, including flat, tubular, and belt webbings, made of Lycra fiber and carbon coated polyamide fiber, were used in this study. The <span class="hlt">strain</span>-resistance properties of the webbings were evaluated in stretch-recovery tests and measured within 30% <span class="hlt">strain</span>. It was found that tensile hysteresis and contact resistance significantly influence the tensile <span class="hlt">elasticity</span> and the resistance sensitivity of the webbings. The results showed that the webbing structure definitely contributes to the tensile hysteresis and contact resistance. The smaller the friction is among the yarns in the belt webbing, the smaller the tensile hysteresis loss. However the close proximity of the conductive yarns in flat and tubular webbings results in a lower contact resistance. PMID:22319376</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3274011','PMC'); return false;" href="http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3274011"><span id="translatedtitle">The Effect of Tensile Hysteresis and Contact Resistance on the Performance of <span class="hlt">Strain</span>-Resistant <span class="hlt">Elastic</span>-Conductive Webbing</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Shyr, Tien-Wei; Shie, Jing-Wen; Jhuang, Yan-Er</p> <p>2011-01-01</p> <p>To use e-textiles as a <span class="hlt">strain</span>-resistance sensor they need to be both <span class="hlt">elastic</span> and conductive. Three kinds of <span class="hlt">elastic</span>-conductive webbings, including flat, tubular, and belt webbings, made of Lycra fiber and carbon coated polyamide fiber, were used in this study. The <span class="hlt">strain</span>-resistance properties of the webbings were evaluated in stretch-recovery tests and measured within 30% <span class="hlt">strain</span>. It was found that tensile hysteresis and contact resistance significantly influence the tensile <span class="hlt">elasticity</span> and the resistance sensitivity of the webbings. The results showed that the webbing structure definitely contributes to the tensile hysteresis and contact resistance. The smaller the friction is among the yarns in the belt webbing, the smaller the tensile hysteresis loss. However the close proximity of the conductive yarns in flat and tubular webbings results in a lower contact resistance. PMID:22319376</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2004AGUFM.G21A0108N&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2004AGUFM.G21A0108N&link_type=ABSTRACT"><span id="translatedtitle">Evaluation Of <span class="hlt">Elastic</span> <span class="hlt">Strain</span> Accumulation In The Southern Indian Peninsula By GPS-Geodesy</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Narayanababu, R.; Ec, M.; Tummala, C.</p> <p>2004-12-01</p> <p>The computed <span class="hlt">elastic</span> <span class="hlt">strain</span> accumulation in the southern Indian peninsula from the GPS derived velocity fields of the global network of GPS stations, in and around the Indian plate which includes Maitri, Indian Antarctic Station, show a significant departure from rigid plate behaviour in a manner consistent with the mapped intra plate stress field, observations of deformations and seismicity in the region. Our results of intraplate <span class="hlt">strain</span> accumulation within Antarctica Plate covering three sites MAIT, CAS1 and DAV1 are 1.8x10-9yr-1, 1.6x10-9yr-1 and 1.1x10-9yr-1, respectively. Similarly, the estimates of interplate <span class="hlt">strain</span> accumulation between Antarctica and other plates Somalia (SEY1), Africa (HARO), Australia (YAR1), and diffuse plate boundary between India and Australia (COCO) are found to be 1.1x10-9yr-1, 1.0x10-10yr-1, 1.27x10-8yr-1 and 1.18x10-8yr-1, respectively. These estimates are in good agreement with the earlier studies on estimation of global <span class="hlt">strain</span> rate. The combined GPS and seismic analysis confirm the emergence of diffuse plate boundary between India and Australia and relates to the late Miocene Himalayan uplift. The calculated stress field in the West of the Indian Peninsula has a roughly N-S directed tensional and E-W oriented compressional character and the velocity vectors of all other sites throw a significant insight into the plausible causes of the <span class="hlt">strain</span> accumulation processes in the Indian Ocean and the northward movement of Indian plate.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015JMPSo..78...94G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015JMPSo..78...94G"><span id="translatedtitle">The stability of <span class="hlt">elastically</span> <span class="hlt">strained</span> nanorings and the formation of quantum dot molecules</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Gill, Simon P. A.</p> <p>2015-05-01</p> <p>Self-assembled nanorings have recently been identified in a number of heteroepitaxially <span class="hlt">strained</span> material systems. Under some circumstances these rings have been observed to break up into ring-shaped quantum dot molecules. A general non-linear model for the <span class="hlt">elastic</span> <span class="hlt">strain</span> energy of non-axisymmetric epitaxially <span class="hlt">strained</span> nanostructures beyond the small slope assumption is developed. This model is then used to investigate the stability of <span class="hlt">strained</span> nanorings evolving via surface diffusion subject to perturbations around their circumference. An expression for the fastest growing mode is determined and related to experimental observations. The model predicts a region of stability for rings below a critical radius, and also a region for larger rings which have a proportionally small thickness. The predictions of the model are shown to be consistent with the available results. For the heteroepitaxial InP on In0.5Ga0.5P system investigated by Jevasuwan et al. (2013), the nanorings are found to be stable below a certain critical size. This is in good quantitative agreement with the model predictions. At larger sizes, the rings are unstable. The number of dots in the resulting quantum dot molecule is similar to the mode number for the fastest growing mode. Second order terms show that the number of dots is expected to reduce as the height of the ring increases in proportion to its thickness. The <span class="hlt">strained</span> In0.4Ga0.6As on GaAs nanorings of Hanke et al. (2007) are always stable and this is in accordance with the findings of the analysis. The Au nanorings of Ruffino et al. (2011) are stable as well, even as they expand during annealing. This observation is also shown to be consistent with the proposed model, which is expected to be useful in the design and tailoring of heteroepitaxial systems for the self-organisation of quantum dot molecules.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/755313','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/755313"><span id="translatedtitle">An <span class="hlt">elastic</span>-perfectly plastic flow model for <span class="hlt">finite</span> element analysis of perforated materials</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Jones, D.P.; Gordon, J.L.; Hutula, D.N.; Banas, D.; Newman, J.B.</p> <p>1999-02-01</p> <p>This paper describes the formulation of an <span class="hlt">elastic</span>-perfectly plastic flow theory applicable to equivalent solid [EQS] modeling of perforated materials. An equilateral triangular array of circular penetrations is considered. The usual assumptions regarding geometry and loading conditions applicable to the development of <span class="hlt">elastic</span> constants for EQS modeling of perforated plates are considered to apply here. An <span class="hlt">elastic</span>-perfectly plastic [EPP] EQS model is developed for a collapse surface that includes fourth-order stress terms. The fourth order yield function has been shown to be appropriate for plates with a triangular array of circular holes. A complete flow model is formulated using the consistent tangent modulus approach based on the fourth order yield function.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016PMag...96.1643G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016PMag...96.1643G"><span id="translatedtitle">Stored energy in metallic glasses due to <span class="hlt">strains</span> within the <span class="hlt">elastic</span> limit</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Greer, A. L.; Sun, Y. H.</p> <p>2016-06-01</p> <p>Room temperature loading of metallic glasses, at stresses below the macroscopic yield stress, raises their enthalpy and causes creep. Thermal cycling of metallic glasses between room temperature and 77 K also raises their enthalpy. In both cases, the enthalpy increases are comparable to those induced by heavy plastic deformation, but, as we show, the origins must be quite different. For plastic deformation, the enthalpy increase is a fraction (<10%) of the work done (WD) (and, in this sense, the behaviour is similar to that of conventional polycrystalline metals and alloys). In contrast, the room temperature creep and the thermal cycling involve small <span class="hlt">strains</span> well within the <span class="hlt">elastic</span> limit; in these cases, the enthalpy increase in the glass exceeds the WD, by as much as three orders of magnitude. We argue that the increased enthalpy can arise only from an endothermic disordering process drawing heat from the surroundings. We examine the mechanisms of this process. The increased enthalpy ('stored energy') is a measure of rejuvenation and appears as an exothermic heat of relaxation on heating the glass. The profile of this heat release (the 'relaxation spectrum') is analysed for several metallic glasses subjected to various treatments. Thus, the effects of the small-<span class="hlt">strain</span> processing (creep and thermal cycling) can be better understood, and we can explore the potential for improving properties, in particular the plasticity, of metallic glasses. Metallic glasses can exhibit a wide range of enthalpy at a given temperature, and small-<span class="hlt">strain</span> processing may assist in accessing this for practical purposes.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/17227094','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/17227094"><span id="translatedtitle"><span class="hlt">Finite</span> element modeling for <span class="hlt">strain</span> rate dependency of fracture resistance in compact bone.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Charoenphan, S; Polchai, A</p> <p>2007-02-01</p> <p>Crack growths in compact bones driven by various <span class="hlt">strain</span> rate levels were studied using <span class="hlt">finite</span> element modeling. The energy resistance curves in bovine femur cortical bones were characterized, whereas the orthotropic viscoelasticity in bone materials was accounted for to assess the effect of <span class="hlt">strain</span> rate on the energy resistance curve. The models were also used to justify the anticipated plane <span class="hlt">strain</span> response as a result of rather thick specimens used in experiments. Similarities were found between the experimental and model results when crack resistance ability exhibited in bones with slow loading rates, while unstable crack growth existed in bones with rapid loading rates. The critical energy release rates slightly decreased with the increase in <span class="hlt">strain</span> rates. The hybrid experimental and computational method introduced in this study could be beneficial for application in fracture study in which standard experiments cannot be validly performed. PMID:17227094</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/1044892','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/1044892"><span id="translatedtitle">An explicit <span class="hlt">finite</span> element formulation for dynamic <span class="hlt">strain</span> localization and damage evolution in metals</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Mourad, Hashem M; Bronkhorst, Curt A; Addessio, Francis L</p> <p>2010-12-16</p> <p>An explicit <span class="hlt">finite</span> element formulation, used to study the behavior and failure mechanisms of metallic materials under high <span class="hlt">strain</span> rate loading, is presented. The formulation is based on the assumed-<span class="hlt">strain</span> approach of Fish and Belytschko [1988], which allows localization bands to be embedded within an element, thereby alleviating mesh sensitivity and reducing the required computational effort. The behavior of the material outside localization bands (and of the virgin material prior to the onset of <span class="hlt">strain</span> localization) is represented using a Gurson-type coupled plasticity-damage model based on the work of Johnson and Addessio [1988]. Assuming adiabatic conditions, the response of the localization band material is represented by a set of constitutive equations for large elasticviscoplastic deformations in metals at high <span class="hlt">strain</span> rates and high homologous temperatures (see Brown et al. [1989]). Computational results are compared to experimental data for different metallic alloys to illustrate the advantages of the proposed modeling strategy.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/1228004','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/1228004"><span id="translatedtitle">Wave propagation in anisotropic <span class="hlt">elastic</span> materials and curvilinear coordinates using a summation-by-parts <span class="hlt">finite</span> difference method</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Petersson, N. Anders; Sjogreen, Bjorn</p> <p>2015-07-20</p> <p>We develop a fourth order accurate <span class="hlt">finite</span> difference method for solving the three-dimensional <span class="hlt">elastic</span> wave equation in general heterogeneous anisotropic materials on curvilinear grids. The proposed method is an extension of the method for isotropic materials, previously described in the paper by Sjögreen and Petersson (2012) [11]. The method we proposed discretizes the anisotropic <span class="hlt">elastic</span> wave equation in second order formulation, using a node centered <span class="hlt">finite</span> difference method that satisfies the principle of summation by parts. The summation by parts technique results in a provably stable numerical method that is energy conserving. Also, we generalize and evaluate the super-grid far-field technique for truncating unbounded domains. Unlike the commonly used perfectly matched layers (PML), the super-grid technique is stable for general anisotropic material, because it is based on a coordinate stretching combined with an artificial dissipation. Moreover, the discretization satisfies an energy estimate, proving that the numerical approximation is stable. We demonstrate by numerical experiments that sufficiently wide super-grid layers result in very small artificial reflections. Applications of the proposed method are demonstrated by three-dimensional simulations of anisotropic wave propagation in crystals.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/pages/biblio/1228004-wave-propagation-anisotropic-elastic-materials-curvilinear-coordinates-using-summation-parts-finite-difference-method','SCIGOV-DOEP'); return false;" href="http://www.osti.gov/pages/biblio/1228004-wave-propagation-anisotropic-elastic-materials-curvilinear-coordinates-using-summation-parts-finite-difference-method"><span id="translatedtitle">Wave propagation in anisotropic <span class="hlt">elastic</span> materials and curvilinear coordinates using a summation-by-parts <span class="hlt">finite</span> difference method</span></a></p> <p><a target="_blank" href="http://www.osti.gov/pages">DOE PAGESBeta</a></p> <p>Petersson, N. Anders; Sjogreen, Bjorn</p> <p>2015-07-20</p> <p>We develop a fourth order accurate <span class="hlt">finite</span> difference method for solving the three-dimensional <span class="hlt">elastic</span> wave equation in general heterogeneous anisotropic materials on curvilinear grids. The proposed method is an extension of the method for isotropic materials, previously described in the paper by Sjögreen and Petersson (2012) [11]. The method we proposed discretizes the anisotropic <span class="hlt">elastic</span> wave equation in second order formulation, using a node centered <span class="hlt">finite</span> difference method that satisfies the principle of summation by parts. The summation by parts technique results in a provably stable numerical method that is energy conserving. Also, we generalize and evaluate the super-grid far-fieldmore » technique for truncating unbounded domains. Unlike the commonly used perfectly matched layers (PML), the super-grid technique is stable for general anisotropic material, because it is based on a coordinate stretching combined with an artificial dissipation. Moreover, the discretization satisfies an energy estimate, proving that the numerical approximation is stable. We demonstrate by numerical experiments that sufficiently wide super-grid layers result in very small artificial reflections. Applications of the proposed method are demonstrated by three-dimensional simulations of anisotropic wave propagation in crystals.« less</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19840009553','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19840009553"><span id="translatedtitle">A <span class="hlt">finite</span> difference scheme for the equilibrium equations of <span class="hlt">elastic</span> bodies</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Phillips, T. N.; Rose, M. E.</p> <p>1984-01-01</p> <p>A compact difference scheme is described for treating the first-order system of partial differential equations which describe the equilibrium equations of an <span class="hlt">elastic</span> body. An algebraic simplification enables the solution to be obtained by standard direct or iterative techniques.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009OptLE..47..352N','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009OptLE..47..352N"><span id="translatedtitle">Mesoscopic <span class="hlt">strain</span> fields in woven composites: Experiments vs. <span class="hlt">finite</span> element modeling</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Nicoletto, Gianni; Anzelotti, Giancarlo; Riva, Enrica</p> <p>2009-03-01</p> <p>Detailed determination of <span class="hlt">strain</span> in woven composite materials is fundamental for understanding their mechanics and for validating sophisticated computational models. The digital image correlation technique is briefly presented and applied to the full-field <span class="hlt">strain</span> determination in a twill-weave carbon-fiber-reinforced-plastic (CFRP) composite under in-plane loading. The experimental results are used to assess companion results obtained with an ad hoc <span class="hlt">finite</span> element-based model. The DIC vs. FEM comparison is carried out at the mesoscopic scale.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/26192949','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/26192949"><span id="translatedtitle">Evaluation of Axonal <span class="hlt">Strain</span> as a Predictor for Mild Traumatic Brain Injuries Using <span class="hlt">Finite</span> Element Modeling.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Giordano, Chiara; Kleiven, Svein</p> <p>2014-11-01</p> <p><span class="hlt">Finite</span> element (FE) models are often used to study the biomechanical effects of traumatic brain injury (TBI). Measures based on mechanical responses, such as principal <span class="hlt">strain</span> or invariants of the <span class="hlt">strain</span> tensor, are used as a metric to predict the risk of injury. However, the reliability of inferences drawn from these models depends on the correspondence between the mechanical measures and injury data, as well as the establishment of accurate thresholds of tissue injury. In the current study, a validated anisotropic FE model of the human head is used to evaluate the hypothesis that <span class="hlt">strain</span> in the direction of fibers (axonal <span class="hlt">strain</span>) is a better predictor of TBI than maximum principal <span class="hlt">strain</span> (MPS), anisotropic equivalent <span class="hlt">strain</span> (AESM) and cumulative <span class="hlt">strain</span> damage measure (CSDM). An analysis of head kinematics-based metrics, such as head injury criterion (HIC) and brain injury criterion (BrIC), is also provided. Logistic regression analysis is employed to compare binary injury data (concussion/no concussion) with continuous <span class="hlt">strain</span>/kinematics data. The threshold corresponding to 50% of injury probability is determined for each parameter. The predictive power (area under the ROC curve, AUC) is calculated from receiver operating characteristic (ROC) curve analysis. The measure with the highest AUC is considered to be the best predictor of mTBI. Logistic regression shows a statistical correlation between all the mechanical predictors and injury data for different regions of the brain. Peaks of axonal <span class="hlt">strain</span> have the highest AUC and determine a <span class="hlt">strain</span> threshold of 0.07 for corpus callosum and 0.15 for the brainstem, in agreement with previously experimentally derived injury thresholds for reversible axonal injury. For a data set of mild TBI from the national football league, the <span class="hlt">strain</span> in the axonal direction is found to be a better injury predictor than MPS, AESM, CSDM, BrIC and HIC. PMID:26192949</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20050185211','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20050185211"><span id="translatedtitle">Structural Health Monitoring Using High-Density Fiber Optic <span class="hlt">Strain</span> Sensor and Inverse <span class="hlt">Finite</span> Element Methods</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Vazquez, Sixto L.; Tessler, Alexander; Quach, Cuong C.; Cooper, Eric G.; Parks, Jeffrey; Spangler, Jan L.</p> <p>2005-01-01</p> <p>In an effort to mitigate accidents due to system and component failure, NASA s Aviation Safety has partnered with industry, academia, and other governmental organizations to develop real-time, on-board monitoring capabilities and system performance models for early detection of airframe structure degradation. NASA Langley is investigating a structural health monitoring capability that uses a distributed fiber optic <span class="hlt">strain</span> system and an inverse <span class="hlt">finite</span> element method for measuring and modeling structural deformations. This report describes the constituent systems that enable this structural monitoring function and discusses results from laboratory tests using the fiber <span class="hlt">strain</span> sensor system and the inverse <span class="hlt">finite</span> element method to demonstrate structural deformation estimation on an instrumented test article</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2016JMPSo..88..204L&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2016JMPSo..88..204L&link_type=ABSTRACT"><span id="translatedtitle">Molecular simulation guided constitutive modeling on <span class="hlt">finite</span> <span class="hlt">strain</span> viscoelasticity of elastomers</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Li, Ying; Tang, Shan; Kröger, Martin; Liu, Wing Kam</p> <p>2016-03-01</p> <p>Viscoelasticity characterizes the most important mechanical behavior of elastomers. Understanding the viscoelasticity, especially <span class="hlt">finite</span> <span class="hlt">strain</span> viscoelasticity, of elastomers is the key for continuation of their dedicated use in industrial applications. In this work, we present a mechanistic and physics-based constitutive model to describe and design the <span class="hlt">finite</span> <span class="hlt">strain</span> viscoelastic behavior of elastomers. Mathematically, the viscoelasticity of elastomers has been decomposed into hyperelastic and viscous parts, which are attributed to the nonlinear deformation of the cross-linked polymer network and the diffusion of free chains, respectively. The hyperelastic deformation of a cross-linked polymer network is governed by the cross-linking density, the molecular weight of the polymer strands between cross-linkages, and the amount of entanglements between different chains, which we observe through large scale molecular dynamics (MD) simulations. Moreover, a recently developed non-affine network model (Davidson and Goulbourne, 2013) is confirmed in the current work to be able to capture these key physical mechanisms using MD simulation. The energy dissipation during a loading and unloading process of elastomers is governed by the diffusion of free chains, which can be understood through their reptation dynamics. The viscous stress can be formulated using the classical tube model (Doi and Edwards, 1986); however, it cannot be used to capture the energy dissipation during <span class="hlt">finite</span> deformation. By considering the tube deformation during this process, as observed from the MD simulations, we propose a modified tube model to account for the <span class="hlt">finite</span> deformation behavior of free chains. Combing the non-affine network model for hyperelasticity and modified tube model for viscosity, both understood by molecular simulations, we develop a mechanism-based constitutive model for <span class="hlt">finite</span> <span class="hlt">strain</span> viscoelasticity of elastomers. All the parameters in the proposed constitutive model have</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/1132568','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/1132568"><span id="translatedtitle">Spectral Modeling of Residual Stress and Stored <span class="hlt">Elastic</span> <span class="hlt">Strain</span> Energy in Thermal Barrier Coatings</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Donegan, Sean; Rolett, Anthony</p> <p>2013-12-31</p> <p>Solutions to the thermoelastic problem are important for characterizing the response under temperature change of refractory systems. This work extends a spectral fast Fourier transform (FFT) technique to analyze the thermoelastic behavior of thermal barrier coatings (TBCs), with the intent of probing the local origins of failure in TBCs. The thermoelastic FFT (teFFT) approach allows for the characterization of local thermal residual stress and <span class="hlt">strain</span> fields, which constitute the origins of failure in TBC systems. A technique based on statistical extreme value theory known as peaks-over-threshold (POT) is developed to quantify the extreme values ("hot spots") of stored <span class="hlt">elastic</span> <span class="hlt">strain</span> energy (i.e., <span class="hlt">elastic</span> energy density, or EED). The resolution dependence of the teFFT method is assessed through a sensitivity study of the extreme values in EED. The sensitivity study is performed both for the local (point-by-point) eld distributions as well as the grain scale eld distributions. A convergence behavior to a particular distribution shape is demonstrated for the local elds. The grain scale fields are shown to exhibit a possible convergence to a maximum level of EED. To apply the teFFT method to TBC systems, 3D synthetic microstructures are created to approximate actual TBC microstructures. The morphology of the grains in each constituent layer as well as the texture is controlled. A variety of TBC materials, including industry standard materials and potential future materials, are analyzed using the teFFT. The resulting hot spots are quantified using the POT approach. A correlation between hot spots in EED and interface rumpling between constituent layers is demonstrated, particularly for the interface between the bond coat (BC) and the thermally grown oxide (TGO) layer.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4646616','PMC'); return false;" href="http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4646616"><span id="translatedtitle">The <span class="hlt">Elastic</span> Behaviour of Sintered Metallic Fibre Networks: A <span class="hlt">Finite</span> Element Study by Beam Theory</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Bosbach, Wolfram A.</p> <p>2015-01-01</p> <p>Background The <span class="hlt">finite</span> element method has complimented research in the field of network mechanics in the past years in numerous studies about various materials. Numerical predictions and the planning efficiency of experimental procedures are two of the motivational aspects for these numerical studies. The widespread availability of high performance computing facilities has been the enabler for the simulation of sufficiently large systems. Objectives and Motivation In the present study, <span class="hlt">finite</span> element models were built for sintered, metallic fibre networks and validated by previously published experimental stiffness measurements. The validated models were the basis for predictions about so far unknown properties. Materials and Methods The <span class="hlt">finite</span> element models were built by transferring previously published skeletons of fibre networks into <span class="hlt">finite</span> element models. Beam theory was applied as simplification method. Results and Conclusions The obtained material stiffness isn’t a constant but rather a function of variables such as sample size and boundary conditions. Beam theory offers an efficient <span class="hlt">finite</span> element method for the simulated fibre networks. The experimental results can be approximated by the simulated systems. Two worthwhile aspects for future work will be the influence of size and shape and the mechanical interaction with matrix materials. PMID:26569603</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li class="active"><span>12</span></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_12 --> <div id="page_13" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li class="active"><span>13</span></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="241"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/1238736','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/1238736"><span id="translatedtitle">Direct synchrotron x-ray measurements of local <span class="hlt">strain</span> fields in <span class="hlt">elastically</span> and plastically bent metallic glasses</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Wu, Yuan; Stoica, Alexandru Dan; Ren, Yang; Ma, Dong; Gao, Yanfei F.; Bei, Hongbin</p> <p>2015-09-03</p> <p><i>In situ</i> high-energy synchrotron X-ray diffraction was conducted on <span class="hlt">elastically</span> and plastically bent bulk metallic glass (BMG) thin plates, from which distinct local <span class="hlt">elastic</span> <span class="hlt">strain</span> fields were mapped spatially. These directly measured residual <span class="hlt">strain</span> fields can be nicely interpreted by our stress analysis, and also validate a previously proposed indirect residual-stress-measurement method by relating nanoindentation hardness to residual stresses. Local shear <span class="hlt">strain</span> variations on the cross sections of these thin plates were found in the plastically bent BMG, which however cannot be determined from the indirect indentation method. As a result, this study has important implications in designing and manipulating internal <span class="hlt">strain</span> fields in BMGs for the purpose of ductility enhancement.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/pages/biblio/1238736-direct-synchrotron-ray-measurements-local-strain-fields-elastically-plastically-bent-metallic-glasses','SCIGOV-DOEP'); return false;" href="http://www.osti.gov/pages/biblio/1238736-direct-synchrotron-ray-measurements-local-strain-fields-elastically-plastically-bent-metallic-glasses"><span id="translatedtitle">Direct synchrotron x-ray measurements of local <span class="hlt">strain</span> fields in <span class="hlt">elastically</span> and plastically bent metallic glasses</span></a></p> <p><a target="_blank" href="http://www.osti.gov/pages">DOE PAGESBeta</a></p> <p>Wu, Yuan; Stoica, Alexandru Dan; Ren, Yang; Ma, Dong; Gao, Yanfei F.; Bei, Hongbin</p> <p>2015-09-03</p> <p>In situ high-energy synchrotron X-ray diffraction was conducted on <span class="hlt">elastically</span> and plastically bent bulk metallic glass (BMG) thin plates, from which distinct local <span class="hlt">elastic</span> <span class="hlt">strain</span> fields were mapped spatially. These directly measured residual <span class="hlt">strain</span> fields can be nicely interpreted by our stress analysis, and also validate a previously proposed indirect residual-stress-measurement method by relating nanoindentation hardness to residual stresses. Local shear <span class="hlt">strain</span> variations on the cross sections of these thin plates were found in the plastically bent BMG, which however cannot be determined from the indirect indentation method. As a result, this study has important implications in designing and manipulatingmore » internal <span class="hlt">strain</span> fields in BMGs for the purpose of ductility enhancement.« less</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/24001928','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/24001928"><span id="translatedtitle">Validation of density-<span class="hlt">elasticity</span> relationships for <span class="hlt">finite</span> element modeling of human pelvic bone by modal analysis.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Scholz, Roger; Hoffmann, Falk; von Sachsen, Sandra; Drossel, Welf-Guntram; Klöhn, Carsten; Voigt, Christian</p> <p>2013-10-18</p> <p>In total hip arthroplasty and particularly in revision surgery, computer assisted pre-operative prediction of the best possible anchorage strategy for implant fixation would be a great help to the surgeon. Computer simulation relies on validated numerical models. In the current study, three density-<span class="hlt">elasticity</span> relationships (No. 1-3) from the literature for inhomogeneous material parameter assignment from CT data in automated <span class="hlt">finite</span> element (FE) modeling of long bones were evaluated for their suitability for FE modeling of human pelvic bone. Numerical modal analysis was conducted on 10 FE models of hemipelvic bone specimens and compared to the gold standard provided by experimental modal analysis results from a previous in-vitro study on the same specimens. Overall, calculated resonance frequencies came out lower than measured values. Magnitude of mean relative deviation of numerical resonance frequencies with regard to measured values is lowest for the density-<span class="hlt">elasticity</span> relationship No. 3 (-15.9%) and considerably higher for both density-<span class="hlt">elasticity</span> relationships No. 1 (-41.1%) and No. 2 (-45.0%). Mean MAC values over all specimens amount to 77.8% (No. 1), 78.5% (No. 2), and 83.0% (No. 3). MAC results show, that mode shapes are only slightly influenced by material distribution. Calculated resonance frequencies are generally lower than measured values, which indicates, that numerical models lack stiffness. Even when using the best suited (No. 3) out of three investigated density-<span class="hlt">elasticity</span> relationships, in FE modeling of pelvic bone a considerable underestimation of model stiffness has to be taken into account. PMID:24001928</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/21783112','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/21783112"><span id="translatedtitle">The effect of <span class="hlt">strain</span> rate on fracture toughness of human cortical bone: a <span class="hlt">finite</span> element study.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Ural, Ani; Zioupos, Peter; Buchanan, Drew; Vashishth, Deepak</p> <p>2011-10-01</p> <p>Evaluating the mechanical response of bone under high loading rates is crucial to understanding fractures in traumatic accidents or falls. In the current study, a computational approach based on cohesive <span class="hlt">finite</span> element modeling was employed to evaluate the effect of <span class="hlt">strain</span> rate on fracture toughness of human cortical bone. Two-dimensional compact tension specimen models were simulated to evaluate the change in initiation and propagation fracture toughness with increasing <span class="hlt">strain</span> rate (range: 0.08-18 s(-1)). In addition, the effect of porosity in combination with <span class="hlt">strain</span> rate was assessed using three-dimensional models of micro-computed tomography-based compact tension specimens. The simulation results showed that bone's resistance against the propagation of a crack decreased sharply with increase in <span class="hlt">strain</span> rates up to 1 s(-1) and attained an almost constant value for <span class="hlt">strain</span> rates larger than 1 s(-1). On the other hand, initiation fracture toughness exhibited a more gradual decrease throughout the <span class="hlt">strain</span> rates. There was a significant positive correlation between the experimentally measured number of microcracks and the fracture toughness found in the simulations. Furthermore, the simulation results showed that the amount of porosity did not affect the way initiation fracture toughness decreased with increasing <span class="hlt">strain</span> rates, whereas it exacerbated the same <span class="hlt">strain</span> rate effect when propagation fracture toughness was considered. These results suggest that <span class="hlt">strain</span> rates associated with falls lead to a dramatic reduction in bone's resistance against crack propagation. The compromised fracture resistance of bone at loads exceeding normal activities indicates a sharp reduction and/or absence of toughening mechanisms in bone during high <span class="hlt">strain</span> conditions associated with traumatic fracture. PMID:21783112</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3143384','PMC'); return false;" href="http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3143384"><span id="translatedtitle">THE EFFECT OF <span class="hlt">STRAIN</span> RATE ON FRACTURE TOUGHNESS OF HUMAN CORTICAL BONE: A <span class="hlt">FINITE</span> ELEMENT STUDY</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Ural, Ani; Zioupos, Peter; Buchanan, Drew; Vashishth, Deepak</p> <p>2011-01-01</p> <p>Evaluating the mechanical response of bone under high loading rates is crucial to understanding fractures in traumatic accidents or falls. In the current study, a computational approach based on cohesive <span class="hlt">finite</span> element modeling was employed to evaluate the effect of <span class="hlt">strain</span> rate on fracture toughness of human cortical bone. Two-dimensional compact tension specimen models were simulated to evaluate the change in initiation and propagation fracture toughness with increasing <span class="hlt">strain</span> rate (range: 0.08 to 18 s−1). In addition, the effect of porosity in combination with <span class="hlt">strain</span> rate was assessed using three-dimensional models of microcomputed tomography-based compact tension specimens. The simulation results showed that bone’s resistance against the propagation of fracture decreased sharply with increase in <span class="hlt">strain</span> rates up to 1 s−1 and attained an almost constant value for <span class="hlt">strain</span> rates larger than 1 s−1. On the other hand, initiation fracture toughness exhibited a more gradual decrease throughout the <span class="hlt">strain</span> rates. There was a significant positive correlation between the experimentally measured number of microcracks and the fracture toughness found in the simulations. Furthermore, the simulation results showed that the amount of porosity did not affect the way initiation fracture toughness decreased with increasing <span class="hlt">strain</span> rates, whereas it exacerbated the same <span class="hlt">strain</span> rate effect when propagation fracture toughness was considered. These results suggest that <span class="hlt">strain</span> rates associated with falls lead to a dramatic reduction in bone’s resistance against crack propagation. The compromised fracture resistance of bone at loads exceeding normal activities indicates a sharp reduction and/or absence of toughening mechanisms in bone during high <span class="hlt">strain</span> conditions associated with traumatic fracture. PMID:21783112</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19840015853','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19840015853"><span id="translatedtitle">CLFE2D: A generalized plane <span class="hlt">strain</span> <span class="hlt">finite</span> element program laminated composites subject to mechanical and hygrothermal loading</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Buczek, M. B.; Gregory, M. A.; Herakovich, C. T.</p> <p>1983-01-01</p> <p>CLFE2D is a two dimensional generalized plane <span class="hlt">strain</span> <span class="hlt">finite</span> element code, using a linear, four node, general quadrilateral, isoparametric element. The program is developed to calculate the displacements, <span class="hlt">strains</span>, stresses, and <span class="hlt">strain</span> energy densities in a <span class="hlt">finite</span> width composite laminate. CLFE2D offers any combination of the following load types: nodal displacements, nodal forces, uniform normal <span class="hlt">strain</span>, or hygrothermal. The program allows the user to input one set of three dimensional orthotropic material properties. The user can then specify the angle of material principal orientation for each element in the mesh. Output includes displacements, stresses, <span class="hlt">strains</span> and <span class="hlt">strain</span> densities at points selected by the user. An option is also available to plot the underformed and deformed <span class="hlt">finite</span> element meshes.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/pages/biblio/1259578-finite-element-simulation-ray-microdiffraction-study-strain-partitioning-layered-nanocomposite','SCIGOV-DOEP'); return false;" href="http://www.osti.gov/pages/biblio/1259578-finite-element-simulation-ray-microdiffraction-study-strain-partitioning-layered-nanocomposite"><span id="translatedtitle"><span class="hlt">Finite</span> Element Simulation and X-Ray Microdiffraction Study of <span class="hlt">Strain</span> Partitioning in a Layered Nanocomposite</span></a></p> <p><a target="_blank" href="http://www.osti.gov/pages">DOE PAGESBeta</a></p> <p>Barabash, R. I.; Agarwal, V.; Koric, S.; Jasiuk, I.; Tischler, J. Z.</p> <p>2016-01-01</p> <p>Tmore » he depth-dependent <span class="hlt">strain</span> partitioning across the interfaces in the growth direction of the NiAl/Cr(Mo) nanocomposite between the Cr and NiAl lamellae was directly measured experimentally and simulated using a <span class="hlt">finite</span> element method (FEM). Depth-resolved X-ray microdiffraction demonstrated that in the as-grown state both Cr and NiAl lamellae grow along the 111 direction with the formation of as-grown distinct residual ~0.16% compressive <span class="hlt">strains</span> for Cr lamellae and ~0.05% tensile <span class="hlt">strains</span> for NiAl lamellae.hree-dimensional simulations were carried out using an implicit FEM. First simulation was designed to study residual <span class="hlt">strains</span> in the composite due to cooling resulting in formation of crystals. <span class="hlt">Strains</span> in the growth direction were computed and compared to those obtained from the microdiffraction experiments. Second simulation was conducted to understand the combined <span class="hlt">strains</span> resulting from cooling and mechanical indentation of the composite. Numerical results in the growth direction of crystal were compared to experimental results confirming the experimentally observed trends.« less</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2003PhDT.......212S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2003PhDT.......212S"><span id="translatedtitle">High pressure and high <span class="hlt">strain</span> rate behavior of cementitious materials: Experiments and <span class="hlt">elastic</span>/viscoplastic modeling</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Schmidt, Martin Jeffrey</p> <p></p> <p> response as the quasistatic tests conducted at the same level of confinement. A decrease in <span class="hlt">strain</span> rate sensitivity with increasing confining pressure was observed. A new <span class="hlt">elastic</span>/viscoplastic model that captures compressibility and dilatancy, as well as <span class="hlt">strain</span> rate effects has been developed for concrete. (Abstract shortened by UMI.)</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/6860496','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/6860496"><span id="translatedtitle">Numerical implementation of inelastic time dependent and time independent, <span class="hlt">finite</span> <span class="hlt">strain</span> constitutive equtions in solids</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Key, S.W.; Krieg, R.D.</p> <p>1980-01-01</p> <p>A number of complex issues are addressed which will allow the incorporation of <span class="hlt">finite</span> <span class="hlt">strain</span>, inelastic material behavior into the piecewise numerical construction of solutions in solid mechanics. Without recourse to extensive continuum mechanics preliminaries, an elementary time independent plasticity model, an elementary time dependent creep model, and a viscoelastic model are introduced as examples of constitutive equations which are routinely used in engineering calculations. The constitutive equations are all suitable for problems involving large deformations and <span class="hlt">finite</span> <span class="hlt">strains</span>. The plasticity and creep models are in rate form and use the symmetric part of the velocity gradient or the stretching to compute the co-rotational time derivative of the Cauchy stress. The viscoelastic model computes the current value of the Cauchy stress from a hereditary integral of a materially invariant form of the stretching history. The current configuration is selected for evaluation of equilibrium as opposed to either the reference configuration or the last established equilibrium configuration. The process of <span class="hlt">strain</span> incrementation is examined in some depth and the stretching evaluated at the midinterval multiplied by the time step is identified as the appropriate <span class="hlt">finite</span> <span class="hlt">strain</span> increment to use with the selected form of the constitutive equations. Discussed is the conversion of rotation rates based on the spin into incremental orthogonal rotations which are then used to update stresses and state variables due to rigid body rotation during the load increment. Comments and references to the literature are directed at numerical integration of the constitutive equations with an emphasis on doing this accurately, if not exactly, for any time step and stretching. This material taken collectively provides an approach to numerical implementation which is marked by its simplicity.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AGUFM.T21B4590H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AGUFM.T21B4590H"><span id="translatedtitle">Basal shear stress below <span class="hlt">elastic</span> crust of the Tibetan plateau inferred from three-dimensional <span class="hlt">finite</span> element modeling</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>He, J.; Xiao, J.; Pan, Z.</p> <p>2014-12-01</p> <p>Associated with northward convergence of the India continent, the surface motion of the Tibetan plateau, documented mainly by dense geodetic GPS measurements, changes greatly both on magnitude and on direction in different tectonic units. The most remarkable discordance of surface motion is around the eastern Himalayan syntaxis, where GPS velocity field is rotated gradually to oppositional direction near the southeastern Tibetan plateau with respect to the northward convergence of the India continent. Such a velocity field could be result from lateral boundary conditions, since the strength of lithosphere is probably weaker in the Tibetan plateau than in the surrounding regions. However, whether the surface motion of the Tibetan plateau is affected by basal shear at base of the <span class="hlt">elastic</span> crust, that could exist if the coupling condition between the <span class="hlt">elastic</span> and the viscous crust were changed, is unclear. Here, we developed a large-scale three-dimensional <span class="hlt">finite</span> element model to explore the possible existence of basal shear below the Tibetan plateau and the surrounding regions. In the model, the lateral boundaries are specified with far-field boundary condition; the blocks surrounding the Tibetan plateaulike the Tarim, the Ordos, and the South China are treat as rigid blocks; and the mean thickness of <span class="hlt">elastic</span> crust is assumed about 25km. Then, the magnitude and distribution of basal shear stress is automatically searchedin numerical calculation to fit surface (GPS) motion of the Tibetan plateau. We find that to better fit surface motion of the Tibetan plateau, negligible basal shear stress on the base of <span class="hlt">elastic</span> crust is needed below majority of the western and the central Tibetan plateau; Whereas, around the eastern and the southeastern Tibetan plateau, especially between the Xianshuhestrike-slip fault and the eastern Himalayan syntaxis, at least ~1.5-3.0 Mpaof basal shear stress is needed to cause rotational surface motion as GPS measurements documented. This</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2011CompM..48..551R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011CompM..48..551R"><span id="translatedtitle">Efficiency comparison of an augmented <span class="hlt">finite</span> element formulation with standard return mapping algorithms for <span class="hlt">elastic</span>-inelastic materials</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Rempler, H.-U.; Wieners, C.; Ehlers, W.</p> <p>2011-11-01</p> <p>The numerical simulation of <span class="hlt">elastic</span>-inelastic material behaviour is reviewed and an alternative method, i. e., an augmented <span class="hlt">Finite</span> Element (FE) formulation is presented. For the augmented FE formulation, the history variables, which provide the information of inelastic deformations from previous time-steps, are represented as FE functions. The discretisation of the augmented system results in additional degrees of freedom (DOF). As a result, generally accepted standard formulations for evaluating inelastic deformations in a numeric sub-step can now be replaced by a fully coupled Newton method. Then, it is not required to solve additional local systems. Both numerical methods are exemplarily applied to a viscoplastic Perzyna-type regularisation of softening material behaviour within a geometrically linear approach in order to simulate the development of shear bands occurring in a tensile bar. Numerical studies prove comparative results, while exhibiting a computational speed-up for the augmented FE formulation.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014CG.....70..181R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014CG.....70..181R"><span id="translatedtitle"><span class="hlt">Finite</span>-difference staggered grids in GPUs for anisotropic <span class="hlt">elastic</span> wave propagation simulation</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Rubio, Felix; Hanzich, Mauricio; Farrés, Albert; de la Puente, Josep; María Cela, José</p> <p>2014-09-01</p> <p>The 3D <span class="hlt">elastic</span> wave equations can be used to simulate the physics of waves traveling through the Earth more precisely than acoustic approximations. However, this improvement in quality has a counterpart in the cost of the numerical scheme. A possible strategy to mitigate that expense is using specialized, high-performing architectures such as GPUs. Nevertheless, porting and optimizing a code for such a platform require a deep understanding of both the underlying hardware architecture and the algorithm at hand. Furthermore, for very large problems, multiple GPUs must work concurrently, which adds yet another layer of complexity to the codes. In this work, we have tackled the problem of porting and optimizing a 3D <span class="hlt">elastic</span> wave propagation engine which supports both standard- and fully-staggered grids to multi-GPU clusters. At the single GPU level, we have proposed and evaluated many optimization strategies and adopted the best performing ones for our final code. At the distributed memory level, a domain decomposition approach has been used which allows for good scalability thanks to using asynchronous communications and I/O.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009JEMat..38..410Y','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009JEMat..38..410Y"><span id="translatedtitle">Predicting the Drop Performance of Solder Joints by Evaluating the <span class="hlt">Elastic</span> <span class="hlt">Strain</span> Energy from High-Speed Ball Pull Tests</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>You, Taehoon; Kim, Yunsung; Kim, Jina; Lee, Jaehong; Jung, Byungwook; Moon, Jungtak; Choe, Heeman</p> <p>2009-03-01</p> <p>Despite being expensive and time consuming, board-level drop testing has been widely used to assess the drop or impact resistance of the solder joints in handheld microelectronic devices, such as cellphones and personal digital assistants (PDAs). In this study, a new test method, which is much simpler and quicker, is proposed. The method involves evaluating the <span class="hlt">elastic</span> <span class="hlt">strain</span> energy and relating it to the impact resistance of the solder joint by considering the Young’s modulus of the bulk solder and the fracture stress of the solder joint during a ball pull test at high <span class="hlt">strain</span> rates. The results show that solder joints can be ranked in order of descending <span class="hlt">elastic</span> <span class="hlt">strain</span> energy as follows: Sn-37Pb, Sn-1Ag-0.5Cu, Sn-3Ag-0.5Cu, and Sn-4Ag-0.5Cu. This order is consistent with the actual drop performances of the samples.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015JSV...344..158N','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015JSV...344..158N"><span id="translatedtitle">Numerical modeling of three-dimensional open <span class="hlt">elastic</span> waveguides combining semi-analytical <span class="hlt">finite</span> element and perfectly matched layer methods</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Nguyen, K. L.; Treyssède, F.; Hazard, C.</p> <p>2015-05-01</p> <p>Among the numerous techniques of non-destructive evaluation, <span class="hlt">elastic</span> guided waves are of particular interest to evaluate defects inside industrial and civil elongated structures owing to their ability to propagate over long distances. However for guiding structures buried in large solid media, waves can be strongly attenuated along the guide axis due to the energy radiation into the surrounding medium, usually considered as unbounded. Hence, searching the less attenuated modes becomes necessary in order to maximize the inspection distance. In the numerical modeling of embedded waveguides, the main difficulty is to account for the unbounded section. This paper presents a numerical approach combining a semi-analytical <span class="hlt">finite</span> element method and a perfectly matched layer (PML) technique to compute the so-called trapped and leaky modes in three-dimensional embedded <span class="hlt">elastic</span> waveguides of arbitrary cross-section. Two kinds of PML, namely the Cartesian PML and the radial PML, are considered. In order to understand the various spectral objects obtained by the method, the PML parameters effects upon the eigenvalue spectrum are highlighted through analytical studies and numerical experiments. Then, dispersion curves are computed for test cases taken from the literature in order to validate the approach.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/21570077','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/21570077"><span id="translatedtitle">Nanoindentation testing and <span class="hlt">finite</span> element simulations of cortical bone allowing for anisotropic <span class="hlt">elastic</span> and inelastic mechanical response.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Carnelli, Davide; Lucchini, Riccardo; Ponzoni, Matteo; Contro, Roberto; Vena, Pasquale</p> <p>2011-07-01</p> <p>Anisotropy is one of the most peculiar aspects of cortical bone mechanical behaviour, and the numerical approach can be successfully used to investigate aspects of bone tissue mechanics that analytical methods solve in approximate way or do not cover. In this work, nanoindentation experimental tests and <span class="hlt">finite</span> element simulations were employed to investigate the <span class="hlt">elastic</span>-inelastic anisotropic mechanical properties of cortical bone. The model allows for anisotropic <span class="hlt">elastic</span> and post-yield behaviour of the tissue. A tension-compression mismatch and direction-dependent yield stresses are allowed for. Indentation experiments along the axial and transverse directions were simulated with the purpose to predict the indentation moduli and hardnesses along multiple orientations. Results showed that the experimental transverse-to-axial ratio of indentation moduli, equal to 0.74, is predicted with a ∼3% discrepancy regardless the post-yield material behaviour; whereas, the transverse-to-axial hardness ratio, equal to 0.86, can be correctly simulated (discrepancy ∼6% w.r.t. the experimental results) only employing an anisotropic post-<span class="hlt">elastic</span> constitutive model. Further, direct comparison between the experimental and simulated indentation tests evidenced a good agreement in the loading branch of the indentation curves and in the peak loads for a transverse-to-axial yield stress ratio comparable to the experimentally obtained transverse-to-axial hardness ratio. In perspective, the present work results strongly support the coupling between indentation experiments and FEM simulations to get a deeper knowledge of bone tissue mechanical behaviour at the microstructural level. The present model could be used to assess the effect of variations of constitutive parameters due to age, injury, and/or disease on bone mechanical performance in the context of indentation testing. PMID:21570077</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014SPIE.9157E..2HM','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014SPIE.9157E..2HM"><span id="translatedtitle">Thermal <span class="hlt">strain</span> along optical fiber in lightweight composite FOG : Brillouin-based distributed measurement and <span class="hlt">finite</span> element analysis</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Minakuchi, Shu; Sanada, Teruhisa; Takeda, Nobuo; Mitani, Shinji; Mizutani, Tadahito; Sasaki, Yoshinobu; Shinozaki, Keisuke</p> <p>2014-05-01</p> <p>Thermal <span class="hlt">strain</span> significantly affects stability of fiber optic gyroscope (FOG) performance. This study investigates thermal <span class="hlt">strain</span> development in a lightweight carbon fiber reinforced plastic (CFRP) FOG under thermal vacuum condition simulating space environment. First, we measure thermal <span class="hlt">strain</span> distribution along an optical fiber in a CFRP FOG using a Brillouin-based high-spatial resolution system. The key <span class="hlt">strain</span> profile is clarified and the <span class="hlt">strain</span> development is simulated using <span class="hlt">finite</span> element analysis. Finally, several constituent materials for FOG are quantitatively compared from the aspect of the maximum thermal <span class="hlt">strain</span> and the density, confirming the clear advantage of CFRP.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/6385152','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/6385152"><span id="translatedtitle">Preferred orientation in carbon and boron nitride: Does a thermodynamic theory of <span class="hlt">elastic</span> <span class="hlt">strain</span> energy get it right. [C; BN</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>McCarty, K.F. )</p> <p>1999-09-01</p> <p>We address whether the <span class="hlt">elastic</span> <span class="hlt">strain</span>-energy theory (minimizing the Gibbs energy of a stressed crystal) of McKenzie and co-workers [D. R. McKenzie and M. M. M. Bilek, J. Vac. Sci. Technol. A [bold 16], 2733 (1998)] adequately explains the preferred orientation observed in carbon and BN films. In the formalism, the Gibbs energy of the cubic materials diamond and cubic boron includes the <span class="hlt">strain</span> that occurs when the phases form, through specific structural transformations, from graphitic precursors. This treatment violates the requirement of thermodynamics that the Gibbs energy be a path-independent, state function. If the cubic phases are treated using the same (path-independent) formalism applied to the graphitic materials, the crystallographic orientation of lowest Gibbs energy is not that observed experimentally. For graphitic (hexagonal) carbon and BN, an <span class="hlt">elastic</span> <span class="hlt">strain</span> approach seems inappropriate because the compressive stresses in energetically deposited films are orders of magnitude higher than the <span class="hlt">elastic</span> limit of the materials. Furthermore, using the known <span class="hlt">elastic</span> constants of either ordered or disordered graphitic materials, the theory does not predict the orientation observed by experiment. [copyright] [ital 1999 American Vacuum Society.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015JPCM...27e5401B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015JPCM...27e5401B"><span id="translatedtitle">Determination of gradient <span class="hlt">elastic</span> tensors: stress and <span class="hlt">strain</span> dependencies of electric field gradients in cubic and hexagonal systems</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Brüsewitz, C.; Vetter, U.; Hofsäss, H.</p> <p>2015-02-01</p> <p>We present ab-initio calculations of the independent components of gradient <span class="hlt">elastic</span> tensors, so-called gradient <span class="hlt">elastic</span> constants, which relate electric field gradient tensors to stress or <span class="hlt">strain</span> tensors. The constants of cubic and hexagonal metals, MAX phases, and zinc oxide were determined within the framework of density functional theory by using the augmented plane waves plus local orbitals method implemented in the WIEN2k code. Comparison with experimental gradient <span class="hlt">elastic</span> constants and electric field gradients' stress dependencies suggest an accuracy of about 30% of the calculated constants, independent of the probe that detects the field gradient being self- or foreign-atom. Changes in the electric field gradient take place by <span class="hlt">strain</span>-induced asymmetric occupations of the p and d states in the valence region for all investigated materials. Volume and structural dependencies of the electric field gradient can directly be determined from this fundamental approach and are, for hexagonal closed packed metals, consistent with vanishing electric field gradients around ideal close packing and volume dependencies larger than one. The concept of these calculations is applicable in any hyperfine interaction method and, thus, can be used to gain information about intrinsic <span class="hlt">strains</span> in systems where the experimental gradient <span class="hlt">elastic</span> constants are inaccessible.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=19850061642&hterms=Energy+intensity&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DTitle%26N%3D0%26No%3D10%26Ntt%3DEnergy%2Bintensity','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=19850061642&hterms=Energy+intensity&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DTitle%26N%3D0%26No%3D10%26Ntt%3DEnergy%2Bintensity"><span id="translatedtitle"><span class="hlt">Strain</span> energy release rate determination of stress intensity factors by <span class="hlt">finite</span> element methods</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Walsh, R. M., Jr.; Pipes, R. B.</p> <p>1985-01-01</p> <p>The stiffness derivative <span class="hlt">finite</span> element technique is used to determine the Mode I stress intensity factors for three-crack configurations. The geometries examined include the double edge notch, single edge notch, and the center crack. The results indicate that when the specified guidelines of the Stiffness Derivative Method are used, a high degree of accuracy can be achieved with an optimized, relatively coarse <span class="hlt">finite</span> element mesh composed of standard, four-node, plane <span class="hlt">strain</span>, quadrilateral elements. The numerically generated solutions, when compared with analytical ones, yield results within 0.001 percent of each other for the double edge crack, 0.858 percent for the single edge crack, and 2.021 percent for the center crack.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2008JPS...180..343W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2008JPS...180..343W"><span id="translatedtitle">Comparative <span class="hlt">finite</span> element analysis of the stress-<span class="hlt">strain</span> states in three different bonded solid oxide fuel cell seal designs</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Weil, K. S.; Koeppel, B. J.</p> <p></p> <p>One of the critical issues in designing and fabricating a high performance planar solid oxide fuel cell (pSOFC) stack is the development of the appropriate materials and techniques for hermetically sealing the metal and ceramic components. A second critical issue is ensuring that the brittle ceramic cell constituents, i.e. the electrodes and electrolyte, exhibit high mechanical reliability by mitigating potential sources of thermal-mechanically induced stresses that can lead to fracture during operation and/or shutdown. A foil-based sealing approach is currently being developed that appears to offer good hermeticity and mechanical integrity, while minimizing the generation of high stresses in either of the joint's substrate materials. Based on the concept's viability, demonstrated in prior experimental work, numerical analyses were conducted to evaluate the behavior and benefits of the seal in a configuration prototypic of current pSOFC stack designs. This paper presents recent results from <span class="hlt">finite</span> element (FE) simulations of a planar cell using the foil-based seal, along with companion analyses of the more conventionally employed glass-ceramic and brazed joints. The stresses and deformations of the components were evaluated at isothermal operating and shutdown temperatures. The results indicate that the foil seal is able to accommodate a significant degree of thermal mismatch <span class="hlt">strain</span> between the metallic support structure and the ceramic cell via <span class="hlt">elastic</span> deformations of the foil and plasticity in the foil-to-cell braze layer. Consequently the cell stresses in this type of seal are predicted to be much lower than those in the glass-ceramic and brazed designs, which is expected to lead to improved stack reliability. This ability to accommodate large thermal <span class="hlt">strain</span> mismatches allows the design requirement of thermal expansion matching between ceramic and metal stack components to be relaxed and expands the list of candidate materials that can be considered for the</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li class="active"><span>13</span></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_13 --> <div id="page_14" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li class="active"><span>14</span></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="261"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014JGRB..119.5052L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014JGRB..119.5052L"><span id="translatedtitle">Subduction-induced mantle flow, <span class="hlt">finite</span> <span class="hlt">strain</span>, and seismic anisotropy: Numerical modeling</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Li, Zhong-Hai; Di Leo, Jeanette F.; Ribe, Neil M.</p> <p>2014-06-01</p> <p>Surface measurements of shear wave splitting patterns are widely used to infer the mantle circulation around subducting slabs; however, the relation between mantle flow and seismic anisotropy is still elusive. <span class="hlt">Finite</span> <span class="hlt">strain</span> is a direct measurement of time-dependent deformation and has been proposed as a proxy for the crystal-preferred orientation (CPO) of mantle minerals. We have conducted a series of numerical models to systematically investigate the mantle flow, <span class="hlt">finite</span> <span class="hlt">strain</span>, olivine CPO, and SKS wave splitting in oceanic subduction zones with variable slab width. They demonstrate that the preferred orientations of olivine a axes generally agree with the long (extensional) axes of the <span class="hlt">finite</span> <span class="hlt">strain</span> ellipsoid (FSE), even in these very complex mantle flow fields; however, neither the a axis nor the FSE axes necessarily aligns with the instantaneous mantle velocity vector. We identify two domains with distinct deformation mechanisms in the central subplate mantle, where simple shear induced by plate advance dominates at shallow depths and produces trench-normal fast splitting, while pure shear induced by slab rollback dominates the deeper mantle and results in trench-parallel fast splitting. The SKS splitting patterns are thus dependent on the competing effects of these two mechanisms and also on the subduction partition ratio γ = Xp/Xt: trench parallel when γ< 1 and trench normal when γ>1. In addition, different mantle deformation mechanisms and SKS splitting patterns are observed in the mantle wedge and around the slab edges, which may aid in the general interpretation of seismic anisotropy observations in natural subduction zones.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19880019811','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19880019811"><span id="translatedtitle">Improved <span class="hlt">finite</span> strip Mindlin plate bending element using assumed shear <span class="hlt">strain</span> distributions</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Chulya, Abhisak; Thompson, Robert L.</p> <p>1988-01-01</p> <p>A linear <span class="hlt">finite</span> strip plate element based on Mindlin/Reissner plate theory is developed. The analysis is suitable for both thin and thick plates. In the formulation new transverse shear <span class="hlt">strains</span> are introduced and assumed constant in each two-code linear strip. The element stiffness matrix is explicitly formulated for efficient computation and computer implementation. Numerical results showing the efficiency and predictive capability of the element for the analysis of plates are presented for different support and loading conditions and a wide range of thicknesses. No sign of shear locking phenomenon was observed with the newly developed element.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=19900029668&hterms=theories+elements&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3Dtheories%2Belements','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=19900029668&hterms=theories+elements&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3Dtheories%2Belements"><span id="translatedtitle">Assumed <span class="hlt">strain</span> distributions for a <span class="hlt">finite</span> strip plate bending element using Mindlin-Reissner plate theory</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Chulya, Abhisak; Mullen, Robert L.</p> <p>1989-01-01</p> <p>A linear <span class="hlt">finite</span> strip plate element based on Mindlin-Reissner plate theory is developed. The analysis is suitable for both thin and thick plates. In the formulation, new transverse shear <span class="hlt">strains</span> are introduced and assumed constant in each two-node linear strip. The element stiffness matrix is explicitly formulated for efficient computation and computer implementation. Numerical results showing the efficiency and predictive capability of the element for the analysis of plates are presented for different support and loading conditions and a wide range of thicknesses. No sign of shear locking is observed with the newly developed element.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2004AGUFM.T33A1327T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2004AGUFM.T33A1327T"><span id="translatedtitle"><span class="hlt">Finite</span> <span class="hlt">strain</span> and relative rheology from field exposures of mantle peridotite, Twin Sisters, Washington</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Tikoff, B.; Larson, C. E.; Newman, J.; Little, T.</p> <p>2004-12-01</p> <p>We present estimates of <span class="hlt">finite</span> <span class="hlt">strain</span> and relative rheology of naturally deformed mantle materials based on field observations in the Twin Sisters Range of Washington state. The Twin Sisters ultramafic body is a 16 by 5.5 km body located 30 km east of Bellingham, Washington. The outcrops show virtually no serpentinization away from the metamorphic sole. We conducted detailed structural mapping in a 100 by 150 meter field area located east of the crest of the Twin Sisters range and approximately midway between the north and south ends. The foliation strikes ~155 and the lineation pitches 40 S. Folded orthopyroxenite dikes within the host dunite allow us to characterize the <span class="hlt">finite</span> <span class="hlt">strain</span>. Dikes trending NE-SE were folded, while dikes trending NW-SE were elongated or boudinaged. Using the method of Talbot (1970), the principal stretch directions in the horizontal plane were calculated using the deformed dikes. We calculated a maximum stretch of 1.596 oriented at 151 (similar to the trace of the foliation) and a minimum stretch of 0.286 in direction 061. Assuming that the lineation and foliation represent the orientation of S1 and the S1S2 plane, respectively, a <span class="hlt">finite</span> <span class="hlt">strain</span> ellipsoid was determined. The best fitting answer defines an oblate ellipsoid with S1=3.15, S2=1.11, and S3=0.286. Thus, on this outcrop, the Twin Sisters dunite has an oblate-shaped <span class="hlt">finite</span> <span class="hlt">strain</span> ellipsoid whose long axis plunges 40 to the SE. The same area provides constraints on relative rheology. Folded orthopyroxenite dikes show a linear relationship between fold wavelength and dike thickness, indicating that they initiated as buckle folds. Using dynamic instability analysis, the orthopyroxene within the dikes is calculated to have ~31 times the effective viscosity of olivine of the dunite matrix, assuming a power law exponenent of n=3 (dislocation creep) for both the dikes and the matrix. Although not investigated in detail, similar orientations of fabrics are observed throughout the Twin</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3045472','PMC'); return false;" href="http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3045472"><span id="translatedtitle">In Situ Parameter Identification of Optimal Density-<span class="hlt">Elastic</span> Modulus Relationships in Subject-Specific <span class="hlt">Finite</span> Element Models of the Proximal Femur</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Cong, Alexander; Buijs, Jorn Op Den; Dragomir-Daescu, Dan</p> <p>2010-01-01</p> <p>Quantitative computed tomography based <span class="hlt">finite</span> element analysis of the femur is currently being investigated as a method for non-invasive stiffness and strength predictions of the proximal femur. The specific objective of this study was to determine better conversion relationships from QCT-derived bone density to <span class="hlt">elastic</span> modulus, in order to achieve accurate predictions of the overall femoral stiffness in a fall-on-the-hip loading configuration. Twenty-two femurs were scanned, segmented and meshed for <span class="hlt">finite</span> element analysis. The <span class="hlt">elastic</span> moduli of the elements were assigned according to the average density in the element. The femurs were then tested to fracture and force-displacement data was collected to calculate femoral stiffness. Using a training set of nine femurs, <span class="hlt">finite</span> element analyses were performed and the parameters of the density-<span class="hlt">elastic</span> modulus relationship were iteratively adjusted to obtain optimal stiffness predictions in a least-squares sense. The results were then validated on the remaining 13 femurs. Our novel procedure resulted in parameter identification of both power and sigmoid functions for density-<span class="hlt">elastic</span> modulus conversion for this specific loading scenario. Our in situ estimated power law achieved improved predictions compared to published power laws, and the sigmoid function yielded even smaller prediction errors. In the future, these results will be used to further improve the femoral strength predictions of our <span class="hlt">finite</span> element models. PMID:21030287</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19880013023','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19880013023"><span id="translatedtitle">An efficient Mindlin <span class="hlt">finite</span> strip plate element based on assumed <span class="hlt">strain</span> distribution</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Chulya, Abhisak; Thompson, Robert L.</p> <p>1988-01-01</p> <p>A simple two node, linear, <span class="hlt">finite</span> strip plate bending element based on Mindlin-Reissner plate theory for the analysis of very thin to thick bridges, plates, and axisymmetric shells is presented. The new transverse shear <span class="hlt">strains</span> are assumed for constant distribution in the two node linear strip. The important aspect is the choice of the points that relate the nodal displacements and rotations through the locking transverse shear <span class="hlt">strains</span>. The element stiffness matrix is explicitly formulated for efficient computation and ease in computer implementation. Numerical results showing the efficiency and predictive capability of the element for analyzing plates with different supports, loading conditions, and a wide range of thicknesses are given. The results show no sign of the shear locking phenomenon.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016CompM..57..149A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016CompM..57..149A"><span id="translatedtitle">A phase-field model for ductile fracture at <span class="hlt">finite</span> <span class="hlt">strains</span> and its experimental verification</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ambati, Marreddy; Kruse, Roland; De Lorenzis, Laura</p> <p>2016-01-01</p> <p>In this paper, a phase-field model for ductile fracture previously proposed in the kinematically linear regime is extended to the three-dimensional <span class="hlt">finite</span> <span class="hlt">strain</span> setting, and its predictions are qualitatively and quantitatively compared with several experimental results, both from ad-hoc tests carried out by the authors and from the available literature. The proposed model is based on the physical assumption that fracture occurs when a scalar measure of the accumulated plastic <span class="hlt">strain</span> reaches a critical value, and such assumption is introduced through the dependency of the phase-field degradation function on this scalar measure. The proposed model is able to capture the experimentally observed sequence of elasto-plastic deformation, necking and fracture phenomena in flat specimens; the occurrence of cup-and-cone fracture patterns in axisymmetric specimens; the role played by notches and by their size on the measured displacement at fracture; and the sequence of distinct cracking events observed in more complex specimens.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20160006299','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20160006299"><span id="translatedtitle"><span class="hlt">Strain</span>-Based Damage Determination Using <span class="hlt">Finite</span> Element Analysis for Structural Health Management</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Hochhalter, Jacob D.; Krishnamurthy, Thiagaraja; Aguilo, Miguel A.</p> <p>2016-01-01</p> <p>A damage determination method is presented that relies on in-service <span class="hlt">strain</span> sensor measurements. The method employs a gradient-based optimization procedure combined with the <span class="hlt">finite</span> element method for solution to the forward problem. It is demonstrated that <span class="hlt">strains</span>, measured at a limited number of sensors, can be used to accurately determine the location, size, and orientation of damage. Numerical examples are presented to demonstrate the general procedure. This work is motivated by the need to provide structural health management systems with a real-time damage characterization. The damage cases investigated herein are characteristic of point-source damage, which can attain critical size during flight. The procedure described can be used to provide prognosis tools with the current damage configuration.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20050092367','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20050092367"><span id="translatedtitle">FIDDLE: A Computer Code for <span class="hlt">Finite</span> Difference Development of Linear <span class="hlt">Elasticity</span> in Generalized Curvilinear Coordinates</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Kaul, Upender K.</p> <p>2005-01-01</p> <p>A three-dimensional numerical solver based on <span class="hlt">finite</span>-difference solution of three-dimensional elastodynamic equations in generalized curvilinear coordinates has been developed and used to generate data such as radial and tangential stresses over various gear component geometries under rotation. The geometries considered are an annulus, a thin annular disk, and a thin solid disk. The solution is based on first principles and does not involve lumped parameter or distributed parameter systems approach. The elastodynamic equations in the velocity-stress formulation that are considered here have been used in the solution of problems of geophysics where non-rotating Cartesian grids are considered. For arbitrary geometries, these equations along with the appropriate boundary conditions have been cast in generalized curvilinear coordinates in the present study.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/26746160','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/26746160"><span id="translatedtitle">Guided wave mode selection for inhomogeneous <span class="hlt">elastic</span> waveguides using frequency domain <span class="hlt">finite</span> element approach.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Chillara, Vamshi Krishna; Ren, Baiyang; Lissenden, Cliff J</p> <p>2016-04-01</p> <p>This article describes the use of the frequency domain <span class="hlt">finite</span> element (FDFE) technique for guided wave mode selection in inhomogeneous waveguides. Problems with Rayleigh-Lamb and Shear-Horizontal mode excitation in isotropic homogeneous plates are first studied to demonstrate the application of the approach. Then, two specific cases of inhomogeneous waveguides are studied using FDFE. Finally, an example of guided wave mode selection for inspecting disbonds in composites is presented. Identification of sensitive and insensitive modes for defect inspection is demonstrated. As the discretization parameters affect the accuracy of the results obtained from FDFE, effect of spatial discretization and the length of the domain used for the spatial fast Fourier transform are studied. Some recommendations with regard to the choice of the above parameters are provided. PMID:26746160</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012AGUFM.S33B2561M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012AGUFM.S33B2561M"><span id="translatedtitle">Investigating <span class="hlt">Elastic</span> Anisotropy of the Leech River Complex, Vancouver Island using <span class="hlt">finite</span>-frequency sensitivity kernels</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Matharu, G.; Bostock, M. G.; Christensen, N. I.; Tromp, J.; Peter, D. B.</p> <p>2012-12-01</p> <p>The Leech River Complex (LRC) of southern Vancouver Island is part of a once continuous belt of Cretaceous sandstone, mudstone and volcanics that formed an accretionary wedge along the northwestern margin of North America. Metamorphism at 50 Ma to prehnite-pumpellyite, greenschist, amphibolite and blueschist facies produced pervasive foliations with strong phyllosilicate lattice preferred orientations. Laboratory measurements and in-situ S-wave splitting analysis of tectonic tremor wavetrains indicate that this fabric produces substantial S-wave anisotropy of up to 30%. In this study we seek to gain further understanding on the nature of anisotropy within the LRC using high signal to noise ratio low frequency earthquake (LFE) templates and 3-D simulations from the spectral element method (SEM). The LFEs are characterized by impulsive, double couple, point sources and lie along a surface between 27 and 37 km depth that is inferred to be the plate boundary, immediately underlying the LRC. The SEM modelling employs a regional mesh that incorporates realistic topography, bathymetry and a 3-D tomographic P-wave velocity model of southern Vancouver Island. It allows us to readily simulate wave propagation in general anisotropic media with up to 21 independent <span class="hlt">elastic</span> constants. We will investigate the orientation and distribution of anisotropy within the LRC by employing sensitivity kernels determined using adjoint methods in conjunction with SEM.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014JSG....68..112V','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014JSG....68..112V"><span id="translatedtitle"><span class="hlt">Finite</span> <span class="hlt">strain</span> estimation from deformed elliptical markers: The minimized Ribar (MIRi) iterative method</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Vitale, Stefano</p> <p>2014-11-01</p> <p>A new technique for estimating the <span class="hlt">finite</span> <span class="hlt">strain</span> of deformed elliptical markers is presented. This method is based on the property of the arithmetic mean Rfbar of the deformed object aspect ratios Rf to reach its minimum value in the undeformed state when they correspond to the initial aspect ratios Ri. The minimized Ribar (MIRi) iterative method furnishes the best results when, in the pre-<span class="hlt">strain</span> state, the markers are uniformly orientated for every aspect ratio (Ri) class. A Matlab code, provided in this study, finds the best values of <span class="hlt">strain</span> Rs and maximum stretching direction X that minimize the arithmetic mean Ribar by means of several iterations. In order to define the uncertainties of Rs and X, the code: (i) re-samples h-times the original (Ri, θ) dataset; (ii) assigns random values to the initial long axis angles θ; (iii) deforms newly the synthetic dataset; (iv) re-applies the MIRi method; and finally (v) estimates the standard deviation for the (Rs, X) values. Tests of the method on synthetic aggregates of elliptical markers and two naturally deformed rocks provide <span class="hlt">strain</span> values that are compared with estimations from other available methods.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/26277458','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/26277458"><span id="translatedtitle">Bone stress and <span class="hlt">strain</span> modification in diastema closure: 3D analysis using <span class="hlt">finite</span> element method.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Geramy, Allahyar; Bouserhal, Joseph; Martin, Domingo; Baghaeian, Pedram</p> <p>2015-09-01</p> <p>The aim of this study was to analyse the stress and <span class="hlt">strain</span> distribution in the alveolar bone between two central incisors in the process of diastema closure with a constant force. A 3-dimensional computer modeling based on <span class="hlt">finite</span> element techniques was used for this purpose. A model of an anterior segment of the mandible containing cortical bone, spongy bone, gingivae, PDL and two central incisors with a bracket in the labial surface of each tooth were designed. The von Mises stress and <span class="hlt">strain</span> was evaluated in alveolar bone along a path of nodes defined in a cresto-apical direction in the midline between two teeth. It was observed that stress and <span class="hlt">strain</span> of alveolar bone increased in midline with a constant force to close the diastema regardless of the type of movement in gradual steps of diastema closure, however the stress was higher in the tipping movement than the bodily so it can be suggested that a protocol of force system modification should be introduced to compensate for the stress and <span class="hlt">strain</span> changes caused by the reduced distance to avoid the unwanted stress alteration during the diastema closure. PMID:26277458</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3039785','PMC'); return false;" href="http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3039785"><span id="translatedtitle">In vivo bone <span class="hlt">strain</span> and <span class="hlt">finite</span>-element modeling of the craniofacial haft in catarrhine primates</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Ross, Callum F; Berthaume, Michael A; Dechow, Paul C; Iriarte-Diaz, Jose; Porro, Laura B; Richmond, Brian G; Spencer, Mark; Strait, David</p> <p>2011-01-01</p> <p>Hypotheses regarding patterns of stress, <span class="hlt">strain</span> and deformation in the craniofacial skeleton are central to adaptive explanations for the evolution of primate craniofacial form. The complexity of craniofacial skeletal morphology makes it difficult to evaluate these hypotheses with in vivo bone <span class="hlt">strain</span> data. In this paper, new in vivo bone <span class="hlt">strain</span> data from the intraorbital surfaces of the supraorbital torus, postorbital bar and postorbital septum, the anterior surface of the postorbital bar, and the anterior root of the zygoma are combined with published data from the supraorbital region and zygomatic arch to evaluate the validity of a <span class="hlt">finite</span>-element model (FEM) of a macaque cranium during mastication. The behavior of this model is then used to test hypotheses regarding the overall deformation regime in the craniofacial haft of macaques. This FEM constitutes a hypothesis regarding deformation of the facial skeleton during mastication. A simplified verbal description of the deformation regime in the macaque FEM is as follows. Inferior bending and twisting of the zygomatic arches about a rostrocaudal axis exerts inferolaterally directed tensile forces on the lateral orbital wall, bending the wall and the supraorbital torus in frontal planes and bending and shearing the infraorbital region and anterior zygoma root in frontal planes. Similar deformation regimes also characterize the crania of Homo and Gorilla under in vitro loading conditions and may be shared among extant catarrhines. Relatively high <span class="hlt">strain</span> magnitudes in the anterior root of the zygoma suggest that the morphology of this region may be important for resisting forces generated during feeding. PMID:21105871</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2002PhRvB..65j4104L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2002PhRvB..65j4104L"><span id="translatedtitle">Symmetry-general least-squares extraction of <span class="hlt">elastic</span> data for <span class="hlt">strained</span> materials from ab initio calculations of stress</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Le Page, Yvon; Saxe, Paul</p> <p>2002-03-01</p> <p>A symmetry-general approach for the least-squares, therefore precise, extraction of <span class="hlt">elastic</span> coefficients for <span class="hlt">strained</span> materials is reported. It analyzes stresses calculated ab initio for properly selected <span class="hlt">strains</span>. The problem, its implementation, and its solution strategy all differ radically from a previous energy-<span class="hlt">strain</span> approach that we published last year, but the normal equations turn out to be amenable to the same constrainment scheme that makes both approaches symmetry general. The symmetry considerations governing the automated selection of appropriately <span class="hlt">strained</span> models and their Cartesian systems are detailed. The extension to materials under general stress is discussed and implemented. VASP was used for ab initio calculation of stresses. A comprehensive range of examples includes a triclinic material (kyanite) and simple materials with a range of symmetries at zero pressure, MgO under hydrostatic pressure, Ti4As3 under [001] uniaxial <span class="hlt">strain</span>, and Si under [001] uniaxial stress. The MgO case agrees with recent experimental work including <span class="hlt">elastic</span> coefficients as well as their first and second derivatives. The curves of <span class="hlt">elastic</span> coefficients for Si show a gradual increase in the 33 compliance coefficient, leading to a collapse of the material at -11.7 GPa, compared with -12.0 GPa experimentally. Interpretation of results for Be using two approximations [local density (LDA), generalized gradient (GGA)], two approaches (stress <span class="hlt">strain</span> and energy <span class="hlt">strain</span>), two potential types (projector augmented wave and ultrasoft), and two quantum engines (VASP and ORESTES) expose the utmost importance of the cell data used for the <span class="hlt">elastic</span> calculations and the lesser importance of the other factors. For stiffness at relaxed cell data, differences are shown to originate mostly in the considerable overestimation of the residual compressive stresses at x-ray cell data by LDA, resulting in a smaller relaxed cell, thus larger values for diagonal stiffness coefficients. The symmetry</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2008JSG....30.1264M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2008JSG....30.1264M"><span id="translatedtitle">The effect of non-passive clast behaviour in the estimation of <span class="hlt">finite</span> <span class="hlt">strain</span> in sedimentary rocks</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Meere, Patrick A.; Mulchrone, Kieran F.; Sears, James W.; Bradway, Michael D.</p> <p>2008-10-01</p> <p>Existing methodologies that use ellipsoidal objects for the analysis of geological <span class="hlt">strain</span> typically assume that these objects acted passively during deformation. This assumption, when not valid, can lead to significant underestimates of <span class="hlt">strain</span> in rocks deformed under low-grade conditions in orogenic forelands. This is especially true when clastic sedimentary rocks are utilized to measure <span class="hlt">strain</span>; the competency contrast between clasts and matrix possibly leading to marked 'non-passive' behaviour. The systematic nature of this <span class="hlt">finite</span> <span class="hlt">strain</span> underestimation may allow for a correction of <span class="hlt">strain</span> estimates when this type of behaviour is evident.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4645108','PMC'); return false;" href="http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4645108"><span id="translatedtitle">Full <span class="hlt">elastic</span> <span class="hlt">strain</span> and stress tensor measurements from individual dislocation cells in copper through-Si vias</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Levine, Lyle E.; Okoro, Chukwudi; Xu, Ruqing</p> <p>2015-01-01</p> <p>Nondestructive measurements of the full <span class="hlt">elastic</span> <span class="hlt">strain</span> and stress tensors from individual dislocation cells distributed along the full extent of a 50 µm-long polycrystalline copper via in Si is reported. Determining all of the components of these tensors from sub-micrometre regions within deformed metals presents considerable challenges. The primary issues are ensuring that different diffraction peaks originate from the same sample volume and that accurate determination is made of the peak positions from plastically deformed samples. For these measurements, three widely separated reflections were examined from selected, individual grains along the via. The lattice spacings and peak positions were measured for multiple dislocation cell interiors within each grain and the cell-interior peaks were sorted out using the measured included angles. A comprehensive uncertainty analysis using a Monte Carlo uncertainty algorithm provided uncertainties for the <span class="hlt">elastic</span> <span class="hlt">strain</span> tensor and stress tensor components. PMID:26594371</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/1248965','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/1248965"><span id="translatedtitle">Full <span class="hlt">elastic</span> <span class="hlt">strain</span> and stress tensor measurements from individual dislocation cells in copper through-Si vias</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Levine, Lyle E.; Okoro, Chukwudi A.; Xu, Ruqing</p> <p>2015-09-30</p> <p>We report non-destructive measurements of the full <span class="hlt">elastic</span> <span class="hlt">strain</span> and stress tensors from individual dislocation cells distributed along the full extent of a 50 mm-long polycrystalline copper via in Si is reported. Determining all of the components of these tensors from sub-micrometre regions within deformed metals presents considerable challenges. The primary issues are ensuring that different diffraction peaks originate from the same sample volume and that accurate determination is made of the peak positions from plastically deformed samples. For these measurements, three widely separated reflections were examined from selected, individual grains along the via. The lattice spacings and peak positions were measured for multiple dislocation cell interiors within each grain and the cell-interior peaks were sorted out using the measured included angles. A comprehensive uncertainty analysis using a Monte Carlo uncertainty algorithm provided uncertainties for the <span class="hlt">elastic</span> <span class="hlt">strain</span> tensor and stress tensor components.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/pages/biblio/1248965-full-elastic-strain-stress-tensor-measurements-from-individual-dislocation-cells-copper-through-si-vias','SCIGOV-DOEP'); return false;" href="http://www.osti.gov/pages/biblio/1248965-full-elastic-strain-stress-tensor-measurements-from-individual-dislocation-cells-copper-through-si-vias"><span id="translatedtitle">Full <span class="hlt">elastic</span> <span class="hlt">strain</span> and stress tensor measurements from individual dislocation cells in copper through-Si vias</span></a></p> <p><a target="_blank" href="http://www.osti.gov/pages">DOE PAGESBeta</a></p> <p>Levine, Lyle E.; Okoro, Chukwudi A.; Xu, Ruqing</p> <p>2015-09-30</p> <p>We report non-destructive measurements of the full <span class="hlt">elastic</span> <span class="hlt">strain</span> and stress tensors from individual dislocation cells distributed along the full extent of a 50 mm-long polycrystalline copper via in Si is reported. Determining all of the components of these tensors from sub-micrometre regions within deformed metals presents considerable challenges. The primary issues are ensuring that different diffraction peaks originate from the same sample volume and that accurate determination is made of the peak positions from plastically deformed samples. For these measurements, three widely separated reflections were examined from selected, individual grains along the via. The lattice spacings and peak positionsmore » were measured for multiple dislocation cell interiors within each grain and the cell-interior peaks were sorted out using the measured included angles. A comprehensive uncertainty analysis using a Monte Carlo uncertainty algorithm provided uncertainties for the <span class="hlt">elastic</span> <span class="hlt">strain</span> tensor and stress tensor components.« less</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/26594371','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/26594371"><span id="translatedtitle">Full <span class="hlt">elastic</span> <span class="hlt">strain</span> and stress tensor measurements from individual dislocation cells in copper through-Si vias.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Levine, Lyle E; Okoro, Chukwudi; Xu, Ruqing</p> <p>2015-11-01</p> <p>Nondestructive measurements of the full <span class="hlt">elastic</span> <span class="hlt">strain</span> and stress tensors from individual dislocation cells distributed along the full extent of a 50 µm-long polycrystalline copper via in Si is reported. Determining all of the components of these tensors from sub-micrometre regions within deformed metals presents considerable challenges. The primary issues are ensuring that different diffraction peaks originate from the same sample volume and that accurate determination is made of the peak positions from plastically deformed samples. For these measurements, three widely separated reflections were examined from selected, individual grains along the via. The lattice spacings and peak positions were measured for multiple dislocation cell interiors within each grain and the cell-interior peaks were sorted out using the measured included angles. A comprehensive uncertainty analysis using a Monte Carlo uncertainty algorithm provided uncertainties for the <span class="hlt">elastic</span> <span class="hlt">strain</span> tensor and stress tensor components. PMID:26594371</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li class="active"><span>14</span></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_14 --> <div id="page_15" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li class="active"><span>15</span></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="281"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFMEP53A0959Z','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFMEP53A0959Z"><span id="translatedtitle">Equivalent-bodyforce Approach on Modeling <span class="hlt">Elastic</span> Dislocation Problem Using <span class="hlt">Finite</span> Element Method</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Zhang, B.; Zhang, H.; Shi, Y.</p> <p>2015-12-01</p> <p>Dislocation theory is well applied to calculate coseismic and postseismic effects. A key signature of the theory is that the solution of displacement is discontinuous. Various numerical methods can handle such discontinuous problems using a mesh which includes the discontinuous plane explicitly. However, generating such a mesh could be challenging and time consuming. We introduce an equivalent-bodyforce approach to handle discontinuities appearing in <span class="hlt">elastic</span> dislocation theory. This approach gets rid of meshing the fault plane explicitly and simplifies the FEM modeling process. Based on Burridge and Knopoff's work, we deduced a close-formed formula representing equivalent-bodyforce in FEM framework. Then compared our numerical results with Okada's analytical solution in a test case in order to check the correctness of our formula and codes. At last, the 2011 Mw9.0 Tohoku-Oki earthquake was studied. We compared our numerical results with GPS observations to check the correctness of our formula and codes again, and discussed the co-seismic effects in North China of this earthquake. In the test case, our numerical results differ from Okada's analytical solution less than 3% in most computing regions. In modelling co-seismic effects of the 2011 Mw9.0 Tohoku-Oki earthquake, our numerical results of displacement field agree well with GPS observations in both direction and magnitude. The co-seismic stress changes in North China are in east-west tension with a magnitude about 1kPa. The north-south compression is one order of magnitude lower. The coulomb failure stress changes on active faults in North China are negative which indicates more stable, except at the north end of the Tanlu fault zone where the coulomb failure stress change is about 100Pa. Equivalent-bodyforce approach is applicable and accurate in FEM modeling. The 2011 Mw9.0 Tohoku-Oki earthquake makes faults in North China more stable except the north end of the Tanlu fault zone.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/947026','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/947026"><span id="translatedtitle">Prediction of the <span class="hlt">Elastic</span>-Plastic Stress/<span class="hlt">Strain</span> Response for Injection-Molded Long-Fiber Thermoplastics</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Nguyen, Ba Nghiep; Bapanapalli, Satish K.; Kunc, Vlastimil; Phelps, Jay; Tucker III, Charles L.</p> <p>2009-01-26</p> <p>This paper proposes a model to predict the <span class="hlt">elastic</span>-plastic response of injection-molded long-fiber thermoplastics (LFTs). The model accounts for <span class="hlt">elastic</span> fibers embedded in a thermoplastic resin that exhibits the <span class="hlt">elastic</span>-plastic behavior obeying the Ramberg-Osgood relation and J-2 deformation theory of plasticity. It also accounts for fiber length and orientation distributions in the composite formed by the injection-molding process. Fiber orientation was predicted using the anisotropic rotary diffusion model recently developed by Phelps and Tucker for LFTs. An incremental procedure using the Eshelby’s equivalent inclusion method and the Mori-Tanaka model is proposed to compute the overall stress increment resulting from an overall <span class="hlt">strain</span> increment for an aligned fiber composite that contains the same fiber volume fraction and length distribution as the actual composite. The incremental response of the later is then obtained from the solution for the aligned fiber composite that is averaged over all possible fiber orientations using the orientation averaging method. Failure during incremental loading is predicted using the Van Hattum-Bernado model. The <span class="hlt">elastic</span>-plastic and strength prediction model for LFTs was validated against the experimental stress-<span class="hlt">strain</span> results obtained for long glass fiber/polypropylene specimens.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1995pvp..confQ..23D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1995pvp..confQ..23D"><span id="translatedtitle">Validation of favor code linear <span class="hlt">elastic</span> fracture solutions for <span class="hlt">finite</span>-length flaw geometries</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Dickson, T. L.; Keeney, J. A.; Bryson, J. W.</p> <p>1995-02-01</p> <p>One of the current tasks within the U.S. Nuclear Regulatory Commission (NRC)-funded Heavy Section Steel Technology Program (HSST) at Oak Ridge National Laboratory (ORNL) is the continuing development of the FAVOR (Fracture, analysis of Vessels: Oak Ridge) computer code. FAVOR performs structural integrity analyses of embrittled nuclear reactor pressure vessels (RPVs) with stainless steel cladding, to evaluate compliance with the applicable regulatory criteria. Since the initial release of FAVOR, the HSST program has continued to enhance the capabilities of the FAVOR code. ABAQUS, a nuclear quality assurance certified (NQA-1) general multidimensional <span class="hlt">finite</span> element code with fracture mechanics capabilities, was used to generate a database of stress-intensity-factor influence coefficients (SIFIC's) for a range of axially and circumferentially oriented semieliptical inner-surface flaw geometries applicable to RPV's with an internal radius (Ri) to wall thickness (w) ratio of 10. This database of SIRC's has been incorporated into a development version of FAVOR, providing it with the capability to perform deterministic and probabilistic fracture analyses of RPVs subjected to transients, such as pressurized thermal shock (PTS), for various flaw geometries. This paper discusses the SIFIC database, comparisons with other investigators, and some of the benchmark verification problem specifications and solutions.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/22470146','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/22470146"><span id="translatedtitle">Distribution of <span class="hlt">elastic</span> <span class="hlt">strains</span> appearing in gallium arsenide as a result of doping with isovalent impurities of phosphorus and indium</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Pavlov, D. A.; Bidus, N. V.; Bobrov, A. I.; Vikhrova, O. V.; Volkova, E. I.; Zvonkov, B. N.; Malekhonova, N. V.; Sorokin, D. S.</p> <p>2015-01-15</p> <p>The distribution of <span class="hlt">elastic</span> <span class="hlt">strains</span> in a system consisting of a quantum-dot layer and a buried GaAs{sub x}P{sub 1−x} layer is studied using geometric phase analysis. A hypothesis is offered concerning the possibility of controlling the process of the formation of InAs quantum dots in a GaAs matrix using a local isovalent phosphorus impurity.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016EGUGA..18.5522Z','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016EGUGA..18.5522Z"><span id="translatedtitle">Equivalent-bodyforce approach on modeling <span class="hlt">elastic</span> dislocation problem using <span class="hlt">finite</span> element method</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Zhang, Bei; Zhang, Huai; Shi, Yaolin</p> <p>2016-04-01</p> <p>Dislocation theory is well applied to calculate coseismic and postseismic effects. A key signature of the theory is that the solution of displacement is discontinuous. Various numerical methods can handle such discontinuous problems using a mesh which includes the discontinuous plane as boundary between cells. However, generating such a mesh could be challenging and time consuming. We introduce an equivalent-bodyforce approach to handle discontinuities appearing in <span class="hlt">elastic</span> dislocation theory. This approach gets rid of meshing the fault plane explicitly and simplifies the FEM modeling process. Based on Burridge and Knopoff's work, we deduced a close-formed formula representing equivalent-bodyforce in FEM framework. Then compared our numerical results with Okada's analytical solution in a test case in order to check the correctness of our formula and codes. At last, the 2011 Mw9.0 Tohoku-Oki earthquake was studied. We compared our numerical results with GPS observations to check the correctness of our formula and codes again, and discussed the co-seismic effects in North China of this earthquake. In the test case, our numerical results differ from Okada's analytical solution less than 3% in most computing regions. In modelling co-seismic effects of the 2011 Mw9.0 Tohoku-Oki earthquake, our numerical results of displacement field agree well with GPS observations in both direction and magnitude. The co-seismic stress changes in North China are in east-west tension with a magnitude about 1kPa. The north-south compression is one order of magnitude lower. The coulomb failure stress changes on active faults in North China are negative which indicates more stable, except at the north end of the Tanlu fault zone where the coulomb failure stress change is about 100Pa. Equivalent-bodyforce approach is applicable and accurate in FEM modeling. The 2011 Mw9.0 Tohoku-Oki earthquake makes faults in North China more stable except the north end of the Tanlu fault zone.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015JSG....73..114R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015JSG....73..114R"><span id="translatedtitle">Kinematic, <span class="hlt">finite</span> <span class="hlt">strain</span> and vorticity analysis of the Sisters Shear Zone, Stewart Island, New Zealand</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ring, Uwe; Bernet, Matthias; Tulloch, Andy</p> <p>2015-04-01</p> <p>The Sisters Shear Zone (SSZ) on Stewart Island, New Zealand, is a greenschist-facies extensional shear zone active prior to and possibly during the development of the Pacific-Antarctica spreading ridge at ∼76 Ma. We report quantitative kinematic and rotation data as well as apatite fission-track (AFT) ages from the SSZ. Early kinematic indicators associated with the NNE-trending stretching lineation formed under upper greenschist-facies metamorphism and show alternating top-to-the-NNW and top-to-the-SSE senses of shear. During progressive exhumation lowermost greenschist-facies and brittle-ductile kinematic indicators depict a more uniform top-to-the-SSE sense of shear in the topmost SSZ just below the detachment plane. Deformed metagranites in the SSZ allow the reconstruction of deformation and flow parameters. The mean kinematic vorticity number (Wm) ranges from 0.10 to 0.89; smaller numbers prevail in the deeper parts of the shear zone with a higher degree of simple shear deformation in the upper parts of the shear zone (deeper and upper parts relate to present geometry). High <span class="hlt">finite</span> <span class="hlt">strain</span> intensity correlates with low Wm and high Wm numbers near the detachment correlate with relatively weak <span class="hlt">strain</span> intensity. <span class="hlt">Finite</span> <span class="hlt">strain</span> shows oblate geometries. Overall, our data indicate vertical and possibly temporal variations in deformation of the SSZ. Most AFT ages cluster around 85-75 Ma. We interpret the AFT ages to reflect the final stages of continental break-up just before and possibly during the initiation of sea-floor spreading between New Zealand and Antarctica.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015JAG...122...40Y','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015JAG...122...40Y"><span id="translatedtitle">Optimal rotated staggered-grid <span class="hlt">finite</span>-difference schemes for <span class="hlt">elastic</span> wave modeling in TTI media</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Yang, Lei; Yan, Hongyong; Liu, Hong</p> <p>2015-11-01</p> <p>The rotated staggered-grid <span class="hlt">finite</span>-difference (RSFD) is an effective approach for numerical modeling to study the wavefield characteristics in tilted transversely isotropic (TTI) media. But it surfaces from serious numerical dispersion, which directly affects the modeling accuracy. In this paper, we propose two different optimal RSFD schemes based on the sampling approximation (SA) method and the least-squares (LS) method respectively to overcome this problem. We first briefly introduce the RSFD theory, based on which we respectively derive the SA-based RSFD scheme and the LS-based RSFD scheme. Then different forms of analysis are used to compare the SA-based RSFD scheme and the LS-based RSFD scheme with the conventional RSFD scheme, which is based on the Taylor-series expansion (TE) method. The contrast in numerical accuracy analysis verifies the greater accuracy of the two proposed optimal schemes, and indicates that these schemes can effectively widen the wavenumber range with great accuracy compared with the TE-based RSFD scheme. Further comparisons between these two optimal schemes show that at small wavenumbers, the SA-based RSFD scheme performs better, while at large wavenumbers, the LS-based RSFD scheme leads to a smaller error. Finally, the modeling results demonstrate that for the same operator length, the SA-based RSFD scheme and the LS-based RSFD scheme can achieve greater accuracy than the TE-based RSFD scheme, while for the same accuracy, the optimal schemes can adopt shorter difference operators to save computing time.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2005AGUFM.T12B..07K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2005AGUFM.T12B..07K"><span id="translatedtitle"><span class="hlt">Finite</span> <span class="hlt">Strain</span> in the Forearc Mantle: Testing the B-type Fabric Anisotropy Hypothesis</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kneller, E. A.; van Keken, P.; Karato, S.; Park, J.</p> <p>2005-12-01</p> <p>Seismic observations from many subduction zones show that the seismically fast direction is perpendicular to the direction of convergence. This is opposite of what is expected from models that assume flow is parallel to plate motion and the seismically fast axis of olivine [100] aligns sub-parallel to the shear direction (A-type fabric). Recent deformation experiments on olivine aggregates show that under low-temperature and high-stress conditions, the fast axis of olivine aligns sub-perpendicular to the shear direction (B-type fabric)(Jung and Karato, 2001; Katayama et al., 2004). B-type fabric has potential to explain convergence-perpendicular anisotropy in subduction zones with flow parallel to plate motion. Kneller et al. (2005) used combined data from deformation experiments on olivine aggregates and dynamical models of subduction zones to predict the distribution of B-type fabric in the mantle wedge. This study predicted that the forearc mantle has suitable thermal and stress conditions for B-type fabric and a rapid transition toward the backarc to conditions more suitable for other olivine fabrics. A vertical projection of the volcanic arc into the mantle wedge is predicted to mark the fabric transition between B-type and A-, E-, or C-type fabrics depending on water content. An important aspect not thoroughly investigated by our previous research is <span class="hlt">finite</span> <span class="hlt">strain</span> accumulation across the predicted fabric transition. In this study we present <span class="hlt">finite</span> <span class="hlt">strain</span> calculation for non-Newtonian subduction zone models with composite water-dependent rheology. This composite rheology includes experimentally based Peierls, dislocation, and diffusion creep. We predict greater than 100 % <span class="hlt">strain</span> accumulation across 75 km for material traveling into the forearc mantle. This <span class="hlt">strain</span> accumulation may be sufficient to produce a well developed B-type fabric. Furthermore, material enters the forearc mantle from a low-<span class="hlt">strain</span>-rate thermal boundary layer at the base of the overriding</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/23293070','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/23293070"><span id="translatedtitle">Structure-based <span class="hlt">finite</span> <span class="hlt">strain</span> modelling of the human left ventricle in diastole.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Wang, H M; Gao, H; Luo, X Y; Berry, C; Griffith, B E; Ogden, R W; Wang, T J</p> <p>2013-01-01</p> <p><span class="hlt">Finite</span> <span class="hlt">strain</span> analyses of the left ventricle provide important information on heart function and have the potential to provide insights into the biomechanics of myocardial contractility in health and disease. Systolic dysfunction is the most common cause of heart failure; however, abnormalities of diastolic function also contribute to heart failure, and are associated with conditions including left ventricular hypertrophy and diabetes. The clinical significance of diastolic abnormalities is less well understood than systolic dysfunction, and specific treatments are presently lacking. To obtain qualitative and quantitative information on heart function in diastole, we develop a three-dimensional computational model of the human left ventricle that is derived from noninvasive imaging data. This anatomically realistic model has a rule-based fibre structure and a structure-based constitutive model. We investigate the sensitivity of this comprehensive model to small changes in the constitutive parameters and to changes in the fibre distribution. We make extensive comparisons between this model and similar models that employ different constitutive models, and we demonstrate qualitative and quantitative differences in stress and <span class="hlt">strain</span> distributions for the different constitutive models. We also provide an initial validation of our model through comparisons to experimental data on stress and <span class="hlt">strain</span> distributions in the left ventricle. PMID:23293070</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1993PhDT........44C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1993PhDT........44C"><span id="translatedtitle">Plane <span class="hlt">strain</span> <span class="hlt">finite</span> element analysis of sheet forming operations including bending effects</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Cho, Uk Youn</p> <p>1993-01-01</p> <p>An improved <span class="hlt">finite</span> element method suitable for the plane-<span class="hlt">strain</span> analysis of sheet metal forming operations is presented. The method incorporates a computationally efficient shell model and a consistent frictional contact algorithm through an implicit updated Lagrangian formulation. The workpiece material model is rigid-viscoplastic with a choice of power law hardening and plastic normal anisotropy and is capable of modeling a wide variety of sheet metals. A simplified nonlinear incremental shell theory is employed along with an optional reduced integration through the thickness for computational efficiency, while retaining the advantages of the kinematic model containing the bending effects. Complex tool geometry can be handled by discrete data points, by primitives (lines and arcs), or by analytical functions. The capabilities of the method are demonstrated through verification problems and comparisons with experimental data, benchmark results, and published data for several practical problems of the sheet metal forming industry. The problems include stretching and/or deep drawing operations, simulation of automobile panel section, and brake bending operation. As an independent investigation from the first portion of the dissertation, measured data from a set of simple bending experiments of two types of aluminum are presented and analyzed. Generated data from the experiments include <span class="hlt">strain</span> histories (loading and unloading), spring back information (spring back angle and <span class="hlt">strains</span>), and friction coefficients. As a by-product, a simple way of estimating the friction coefficient (Coulomb's law) during a bending operation is proposed and demonstrated.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2013AGUFMMR41A2339C&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2013AGUFMMR41A2339C&link_type=ABSTRACT"><span id="translatedtitle">The Effect of Single Crystal <span class="hlt">Elastic</span> and Plastic Anisotropy on <span class="hlt">Strain</span> Heterogeneity: Comparison of Olivine to Other Common Minerals</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Cline, C. J., II; Burnley, P. C.</p> <p>2013-12-01</p> <p>In order to extrapolate the rheological behavior of polycrystalline earth materials to conditions and timescales that are unachievable in a laboratory setting, some sort of model is required. Numerical models are particularly appealing for this task but for these models to provide a sound platform for extrapolation they must be based on a complete understanding of all deformation mechanics that are operating in the real material. In a simplified description these mechanics can be thought of as having three components 1) the individual grains, 2) the grain boundaries and 3) the macroscopic aggregate response, which can be thought of as the interaction of the other two components within the polycrystal. Traditionally, the aggregate response is thought to represent the summed or average behavior of all individual grains deforming under the influence of the macroscopic stress tensor but; recent work within our lab using <span class="hlt">finite</span> element models (FEM) has shown that local stress fields within the aggregate are not representative of the macroscopic stress tensor and can vary in both direction and magnitude. These variations in the stress tensor produce a pattern similar to force chains that are observed in deformation experiments on granular materials; and appear to be a direct consequence of stress percolation which is controlled by the anisotropy of the <span class="hlt">elastic</span> and plastic strengths of the individual grains. To test this hypothesis we will conduct a suite of deformation experiments utilizing multiple monomineralic polycrystals that have a range of single crystal anisotropies. In order to infer the direction of stress acting on each grain and reconstruct the total modulation of stress direction throughout the sample, we have chosen materials that form microstructures that are sensitive to stress direction, such as deformation twins and kink bands. This experimental technique will allow for a direct comparison between the single crystal anisotropy of a material and the</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015GeoJI.202.1908B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015GeoJI.202.1908B"><span id="translatedtitle">An efficient method of 3-D <span class="hlt">elastic</span> full waveform inversion using a <span class="hlt">finite</span>-difference injection method for time-lapse imaging</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Borisov, Dmitry; Singh, Satish C.; Fuji, Nobuaki</p> <p>2015-09-01</p> <p>Seismic full waveform inversion is an objective method to estimate <span class="hlt">elastic</span> properties of the subsurface and is an important area of research, particularly in seismic exploration community. It is a data-fitting approach, where the difference between observed and synthetic data is minimized iteratively. Due to a very high computational cost, the practical implementation of waveform inversion has so far been restricted to a 2-D geometry with different levels of physics incorporated in it (e.g. <span class="hlt">elasticity</span>/viscoelasticity) or to a 3-D geometry but using an acoustic approximation. However, the earth is three-dimensional, <span class="hlt">elastic</span> and heterogeneous and therefore a full 3-D <span class="hlt">elastic</span> inversion is required in order to obtain more accurate and valuable models of the subsurface. Despite the recent increase in computing power, the application of 3-D <span class="hlt">elastic</span> full waveform inversion to real-scale problems remains quite challenging on the current computer architecture. Here, we present an efficient method to perform 3-D <span class="hlt">elastic</span> full waveform inversion for time-lapse seismic data using a <span class="hlt">finite</span>-difference injection method. In this method, the wavefield is computed in the whole model and is stored on a surface above a <span class="hlt">finite</span> volume where the model is perturbed and localized inversion is performed. Comparison of the final results using the 3-D <span class="hlt">finite</span>-difference injection method and conventional 3-D inversion performed within the whole volume shows that our new method provides significant reductions in computational time and memory requirements without any notable loss in accuracy. Our approach shows a big potential for efficient reservoir monitoring in real time-lapse experiments.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AIPC.1650.1730P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AIPC.1650.1730P"><span id="translatedtitle">Modelling NDE pulse-echo inspection of misorientated planar rough defects using an <span class="hlt">elastic</span> <span class="hlt">finite</span> element method</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Pettit, J. R.; Walker, A. E.; Lowe, M. J. S.</p> <p>2015-03-01</p> <p>Pulse-echo ultrasonic NDE examination of large pressure vessel forgings is a design and construction code requirement in the power generation industry. Such inspections aim to size and characterise potential defects that may have formed during the forging process. Typically these defects have a range of orientations and surface roughnesses which can greatly affect ultrasonic wave scattering behaviour. Ultrasonic modelling techniques can provide insight into defect response and therefore aid in characterisation. However, analytical approaches to solving these scattering problems can become inaccurate, especially when applied to increasingly complex defect geometries. To overcome these limitations a <span class="hlt">elastic</span> <span class="hlt">Finite</span> Element (FE) method has been developed to simulate pulse-echo inspections of embedded planar defects. The FE model comprises a significantly reduced spatial domain allowing for a Monte-Carlo based approach to consider multiple realisations of defect orientation and surface roughness. The results confirm that defects aligned perpendicular to the path of beam propagation attenuate ultrasonic signals according to the level of surface roughness. However, for defects orientated away from this plane, surface roughness can increase the magnitude of the scattered component propagating back along the path of the incident beam. This study therefore highlights instances where defect roughness increases the magnitude of ultrasonic scattered signals, as opposed to attenuation which is more often assumed.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/22391230','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/22391230"><span id="translatedtitle">Modelling NDE pulse-echo inspection of misorientated planar rough defects using an <span class="hlt">elastic</span> <span class="hlt">finite</span> element method</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Pettit, J. R.; Lowe, M. J. S.; Walker, A. E.</p> <p>2015-03-31</p> <p>Pulse-echo ultrasonic NDE examination of large pressure vessel forgings is a design and construction code requirement in the power generation industry. Such inspections aim to size and characterise potential defects that may have formed during the forging process. Typically these defects have a range of orientations and surface roughnesses which can greatly affect ultrasonic wave scattering behaviour. Ultrasonic modelling techniques can provide insight into defect response and therefore aid in characterisation. However, analytical approaches to solving these scattering problems can become inaccurate, especially when applied to increasingly complex defect geometries. To overcome these limitations a <span class="hlt">elastic</span> <span class="hlt">Finite</span> Element (FE) method has been developed to simulate pulse-echo inspections of embedded planar defects. The FE model comprises a significantly reduced spatial domain allowing for a Monte-Carlo based approach to consider multiple realisations of defect orientation and surface roughness. The results confirm that defects aligned perpendicular to the path of beam propagation attenuate ultrasonic signals according to the level of surface roughness. However, for defects orientated away from this plane, surface roughness can increase the magnitude of the scattered component propagating back along the path of the incident beam. This study therefore highlights instances where defect roughness increases the magnitude of ultrasonic scattered signals, as opposed to attenuation which is more often assumed.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2011JChPh.135e4902H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011JChPh.135e4902H"><span id="translatedtitle">The molecular kink paradigm for rubber <span class="hlt">elasticity</span>: Numerical simulations of explicit polyisoprene networks at low to moderate tensile <span class="hlt">strains</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Hanson, David E.</p> <p>2011-08-01</p> <p>Based on recent molecular dynamics and ab initio simulations of small isoprene molecules, we propose a new ansatz for rubber <span class="hlt">elasticity</span>. We envision a network chain as a series of independent molecular kinks, each comprised of a small number of backbone units, and the <span class="hlt">strain</span> as being imposed along the contour of the chain. We treat chain extension in three distinct force regimes: (Ia) near zero <span class="hlt">strain</span>, where we assume that the chain is extended within a well defined tube, with all of the kinks participating simultaneously as entropic <span class="hlt">elastic</span> springs, (II) when the chain becomes sensibly straight, giving rise to a purely enthalpic stretching force (until bond rupture occurs) and, (Ib) a linear entropic regime, between regimes Ia and II, in which a force limit is imposed by tube deformation. In this intermediate regime, the molecular kinks are assumed to be gradually straightened until the chain becomes a series of straight segments between entanglements. We assume that there exists a tube deformation tension limit that is inversely proportional to the chain path tortuosity. Here we report the results of numerical simulations of explicit three-dimensional, periodic, polyisoprene networks, using these extension-only force models. At low <span class="hlt">strain</span>, crosslink nodes are moved affinely, up to an arbitrary node force limit. Above this limit, non-affine motion of the nodes is allowed to relax unbalanced chain forces. Our simulation results are in good agreement with tensile stress vs. <span class="hlt">strain</span> experiments.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/25109692','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/25109692"><span id="translatedtitle">Ultrasound <span class="hlt">strain</span> zero-crossing <span class="hlt">elasticity</span> measurement in assessment of renal allograft cortical hardness: a preliminary observation.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Gao, Jing; Rubin, Jonathan M</p> <p>2014-09-01</p> <p>To determine whether ultrasound <span class="hlt">strain</span> zero-crossing <span class="hlt">elasticity</span> measurement can be used to discriminate moderate cortical fibrosis or inflammation in renal allografts, we prospectively assessed cortical hardness with quasi-static ultrasound elastography in 38 renal transplant patients who underwent kidney biopsy from January 2013 to June 2013. With the Banff score criteria for renal cortical fibrosis as gold standard, 38 subjects were divided into two groups: group 1 (n = 18) with ≤25% cortical fibrosis and group 2 (n = 20) with >26% cortical fibrosis. We then divided this population again into group 3 (n = 20) with ≤ 25% inflammation and group 4 (n = 18) with >26% inflammation based on the Banff score for renal parenchyma inflammation. To estimate renal cortical hardness in both population divisions, we propose an ultrasound <span class="hlt">strain</span> relative zero-crossing <span class="hlt">elasticity</span> measurement (ZC) method. In this technique, the relative return to baseline, that is zero <span class="hlt">strain</span>, of <span class="hlt">strain</span> in the renal cortex is compared with that of <span class="hlt">strain</span> in reference soft tissue (between the abdominal wall and pelvic muscles). Using the ZC point on the reference <span class="hlt">strain</span> decompression slope as standard, we determined when cortical <span class="hlt">strain</span> crossed zero during decompression. ZC was negative when cortical <span class="hlt">strain</span> did not return or returned after the reference, whereas ZC was positive when cortical <span class="hlt">strain</span> returned ahead of the reference. Fisher's exact test was used to examine the significance of differences in ZC between groups 1 and 2 and between groups 3 and 4. The accuracy of ZC in determining moderate cortical fibrosis and moderate inflammation was examined by receiver operating characteristic analysis. The intra-class correlation coefficient and analysis of variance were used to test inter-rater reliability and reproducibility. ZC had good inter-observer agreement (ICC = 0.912) and reproducibility (p = 0.979). ZCs were negative in 18 of 18 cases in group 1 and positive in 19 of 20 cases in</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2016CMT....28..993D&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2016CMT....28..993D&link_type=ABSTRACT"><span id="translatedtitle">A thermo-mechanically coupled <span class="hlt">finite</span> <span class="hlt">strain</span> model considering inelastic heat generation</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Dunić, Vladimir; Busarac, Nenad; Slavković, Vukašin; Rosić, Bojana; Niekamp, Rainer; Matthies, Hermann; Slavković, Radovan; Živković, Miroslav</p> <p>2016-07-01</p> <p>The procedure for reuse of <span class="hlt">finite</span> element method (FEM) programs for heat transfer and structure analysis to solve advanced thermo-mechanical problems is presented as powerful algorithm applicable for coupling of other physical fields (magnetic, fluid flow, etc.). In this case, nonlinear Block-Gauss-Seidel partitioned algorithm strongly couples the heat transfer and structural FEM programs by a component-based software engineering. Component template library provides possibility to exchange the data between the components which solve the corresponding subproblems. The structural component evaluates the dissipative energy induced by inelastic <span class="hlt">strain</span>. The heat transfer component computes the temperature change due to the dissipation. The convergence is guaranteed by posing the global convergence criterion on the previously locally converged coupled variables. This enables reuse of software and allows the numerical simulation of thermo-sensitive problems.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016JIEIC.tmp...27R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016JIEIC.tmp...27R"><span id="translatedtitle"><span class="hlt">Finite</span> Element Analysis of Cross Rolling on AISI 304 Stainless Steel: Prediction of Stress and <span class="hlt">Strain</span> Fields</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Rout, Matruprasad; Pal, Surjya Kanta; Singh, Shiv Brat</p> <p>2016-05-01</p> <p>Studies on the effect of <span class="hlt">strain</span> path during rolling has been carried out for a long time, but the same has not been done using <span class="hlt">Finite</span> Element Analysis (FEA). Change in <span class="hlt">strain</span> path affects the state variables in the rolled plate like stress, <span class="hlt">strain</span>, temperature etc. In the current work, <span class="hlt">Finite</span> Element Analysis for cross rolling of AISI 304 austenitic stainless steel has been carried out by rotating the plate by 90° in between the passes. To analyze stress and <span class="hlt">strain</span> fields in the material for cross rolling, a full 3D model of work-roll and plate has been developed using rigid-viscoplastic <span class="hlt">finite</span> element method. The stress and <span class="hlt">strain</span> fields, considering von-Mises yield criteria, are calculated by using updated Lagrangian method. In addition to these, the model also calculates the normal pressure and <span class="hlt">strain</span> rate distribution in the plate during cross rolling. The nature of the variations of stress and <span class="hlt">strain</span> fields in the plate, predicted by the model, is in good agreement with the previously published works for unidirectional rolling.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015JSemi..36c2002Y','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015JSemi..36c2002Y"><span id="translatedtitle">Effect of uniaxial <span class="hlt">strain</span> on the structural, electronic and <span class="hlt">elastic</span> properties of orthorhombic BiMnO3</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Yang, Pei; Haibin, Wu</p> <p>2015-03-01</p> <p>We study the <span class="hlt">elastic</span> constants and electronic properties of orthorhombic BiMnO3 under uniaxial <span class="hlt">strain</span> along the c-axis using the first-principles method. It is found that, beyond the range -0.025 < ɛ < 0.055, the predicted stiffness constants cij cannot demand the Born stability criteria and the compliance constant s44 shows abrupt changes, which accompany phase transition. In addition, the results for magnetism moments and polycrystalline properties are also reported. Additionally, under compressive <span class="hlt">strain</span>, a band gap transition from the indirect to the direct occurs within -0.019 < ɛ < -0.018. Furthermore, the response of the band gap of orthorhombic BiMnO3 to uniaxial <span class="hlt">strain</span> is studied.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2016JEMat.tmp..394M&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2016JEMat.tmp..394M&link_type=ABSTRACT"><span id="translatedtitle">Band-Gap Modulation of GeCH3 Nanoribbons Under <span class="hlt">Elastic</span> <span class="hlt">Strain</span>: A Density Functional Theory Study</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ma, ShengQian; Li, Feng; Jiang, ChunLing</p> <p>2016-06-01</p> <p>Using the density functional theory method, we researched the band-gap modulation of GeCH3 nanoribbons under uniaxial <span class="hlt">elastic</span> <span class="hlt">strain</span>. The results indicated that the band gap of GeCH3 nanoribbons could be tuned along two directions, namely, stretching or compressing ribbons when ɛ was changed from -10% to 10% in 6-zigzag, 10-zigzag, 13-armchair, and 17-armchair nanoribbons, respectively. The band gap greatly changed with <span class="hlt">strain</span>. In the case of tension, the amount of change in the band gap was bigger. But in the case of compression, the gradient was steeper. The band gap had a nearly linear relationship when ɛ ranges from 0% to 10%. We also investigated if the band gap is changed with widths. The results showed variation of the band gap did not rely on widths. Therefore, the GeCH3 nanoribbons had the greatest potential application in <span class="hlt">strain</span> sensors and optical electronics at the nanoscale.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li class="active"><span>15</span></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_15 --> <div id="page_16" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li class="active"><span>16</span></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="301"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015EPJWC..9404011T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015EPJWC..9404011T"><span id="translatedtitle"><span class="hlt">Finite</span> <span class="hlt">strain</span> formulation of viscoelastic damage model for simulation of fabric reinforced polymers under dynamic loading</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Treutenaere, S.; Lauro, F.; Bennani, B.; Matsumoto, T.; Mottola, E.</p> <p>2015-09-01</p> <p>The use of fabric reinforced polymers in the automotive industry is growing significantly. The high specific stiffness and strength, the ease of shaping as well as the great impact performance of these materials widely encourage their diffusion. The present model increases the predictability of explicit <span class="hlt">finite</span> element analysis and push the boundaries of the ongoing phenomenological model. Carbon fibre composites made up various preforms were tested by applying different mechanical load up to dynamic loading. This experimental campaign highlighted the physical mechanisms affecting the initial mechanical properties, namely intra- and interlaminar matrix damage, viscoelasticty and fibre failure. The intralaminar behaviour model is based on the explicit formulation of the matrix damage model developed by the ONERA as the given damage formulation correlates with the experimental observation. Coupling with a Maxwell-Wiechert model, the viscoelasticity is included without losing the direct explicit formulation. Additionally, the model is formulated under a total Lagrangian scheme in order to maintain consistency for <span class="hlt">finite</span> <span class="hlt">strain</span>. Thus, the material frame-indifference as well as anisotropy are ensured. This allows reorientation of fibres to be taken into account particularly for in-plane shear loading. Moreover, fall within the framework of the total Lagrangian scheme greatly makes the parameter identification easier, as based on the initial configuration. This intralaminar model thus relies upon a physical description of the behaviour of fabric composites and the numerical simulations show a good correlation with the experimental results.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/1093017','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/1093017"><span id="translatedtitle">Prediction of the <span class="hlt">Elastic</span>-Plastic Stress/<span class="hlt">Strain</span> Response for Injection-Molded Long-Fiber Thermoplastics</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Nguyen, Ba N.; Kunc, Vlastimil; Phelps, Jay H; TuckerIII, Charles L.; Bapanapalli, Satish K</p> <p>2009-01-01</p> <p>This paper proposes a model to predict the <span class="hlt">elastic</span>-plastic response of injection-molded long-fiber thermoplastics (LFTs). The model accounts for <span class="hlt">elastic</span> fibers embedded in a thermoplastic resin that exhibits the <span class="hlt">elastic</span>-plastic behavior obeying the Ramberg-Osgood relation and J-2 deformation theory of plasticity. It also accounts for fiber length and orientation distributions in the composite formed by the injection-molding process. Fiber orientation was predicted using an anisotropic rotary diffusion model recently developed for LFTs. An incremental procedure using Eshelby's equivalent inclusion method and the Mori-Tanaka assumption is proposed to compute the overall stress increment resulting from an overall <span class="hlt">strain</span> increment for an aligned-fiber composite that contains the same fiber volume fraction and length distribution as the actual composite. The incremental response of the latter is then obtained from the solution for the aligned-fiber composite by averaging over all fiber orientations. Failure during incremental loading is predicted using the Van Hattum-Bernado model. The model is validated against the experimental stress-<span class="hlt">strain</span> results obtained for long-glass-fiber/polypropylene specimens.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/1244194','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/1244194"><span id="translatedtitle">Giant <span class="hlt">elastic</span> tunability in <span class="hlt">strained</span> BiFeO<sub>3</sub> near an electrically induced phase transition</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Yu, Pu; Vasudevan, Rama K.; Tselev, Alexander; Xue, Fei; Chen, Long -Qing; Maksymovych, Petro; Kalinin, Sergei V.; Balke, Nina; Li, Q.; Cao, Y.; Laanait, N.</p> <p>2015-01-01</p> <p><span class="hlt">Elastic</span> anomalies are signatures of phase transitions in condensed matters and have traditionally been studied using various techniques spanning from neutron scattering to static mechanical testing. Here, using band-excitation <span class="hlt">elastic</span>/piezoresponse spectroscopy, we probed sub-MHz <span class="hlt">elastic</span> dynamics of a tip bias-induced rhombohedral–tetragonal phase transition of <span class="hlt">strained</span> (001)-BiFeO<sub>3</sub> (rhombohedral) ferroelectric thin films from ~10<sup>3</sup> nm<sup>3</sup> sample volumes. Near this transition, we observed that the Young's modulus intrinsically softens by over 30% coinciding with 2-3 folds enhancement of local piezoresponse. Coupled with phase-field modeling, we also addressed the influence of polarization switching and mesoscopic structural heterogeneities (e.g., domain walls) on the kinetics of this phase transition, thereby providing fresh insights into the morphotropic phase boundary (MPB) in ferroelectrics. Moreover, the giant electrically tunable <span class="hlt">elastic</span> stiffness and corresponding electromechanical properties observed here suggest potential applications of BiFeO<sub>3</sub> in next-generation frequency-agile electroacoustic devices, based on utilization of the soft modes underlying successive ferroelectric phase transitions.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/544223','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/544223"><span id="translatedtitle">An experimentally verified <span class="hlt">finite</span> element study of the stress-<span class="hlt">strain</span> response of crack geometries experiencing large-scale yielding</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Panontin, T.L.; Sheppard, S.D.</p> <p>1997-12-01</p> <p>Large-<span class="hlt">strain</span>, 3-D <span class="hlt">finite</span> element analyses with incremental plasticity were performed for a variety of crack geometries to study local crack-tip stress-<span class="hlt">strain</span> fields and associated global fracture parameters under conditions of large-scale yielding. The geometries analyzed include thin, single-edge crack tension, single-edge crack bending, and center-crack tension fracture specimens with varying crack depth (a/W) ratios. Two materials were investigated: a high-hardening, low-strength steel and a moderate-hardening, high-strength steel. Mesh refinement studies were performed to ensure convergence of the <span class="hlt">finite</span> element predictions. The studies examine the effects of in-plane crack-tip element size, initial crack-tip radius size, and number of through-thickness layers on predicted distributions of crack-tip stress and plastic <span class="hlt">strain</span> and predicted values of the J-integral and CTOD. In addition, the <span class="hlt">finite</span> element predictions of specimen behavior were verified experimentally by direct measurements, namely load displacement, load longitudinal <span class="hlt">strain</span>, and load CTOS, made during and following testing of the fracture specimens. Representative results of the <span class="hlt">finite</span> element analyses are presented and compared to previously published data where pertinent. Results from the mesh refinement studies and the verification testing are shown. Predicted trends among the specimens and materials in local distributions of crack-tip plastic <span class="hlt">strain</span>, triaxiality, and opening stress as well as in global parameters, J-integral and m-factor, are discussed.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2015CompM..55..921E&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2015CompM..55..921E&link_type=ABSTRACT"><span id="translatedtitle">Energy-momentum conserving higher-order time integration of nonlinear dynamics of <span class="hlt">finite</span> <span class="hlt">elastic</span> fiber-reinforced continua</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Erler, Norbert; Groß, Michael</p> <p>2015-05-01</p> <p>Since many years the relevance of fibre-reinforced polymers is steadily increasing in fields of engineering, especially in aircraft and automotive industry. Due to the high strength in fibre direction, but the possibility of lightweight construction, these composites replace more and more traditional materials as metals. Fibre-reinforced polymers are often manufactured from glass or carbon fibres as attachment parts or from steel or nylon cord as force transmission parts. Attachment parts are mostly subjected to small <span class="hlt">strains</span>, but force transmission parts usually suffer large deformations in at least one direction. Here, a geometrically nonlinear formulation is necessary. Typical examples are helicopter rotor blades, where the fibres have the function to stabilize the structure in order to counteract large centrifugal forces. For long-run analyses of rotor blade deformations, we have to apply numerically stable time integrators for anisotropic materials. This paper presents higher-order accurate and numerically stable time stepping schemes for nonlinear <span class="hlt">elastic</span> fibre-reinforced continua with anisotropic stress behaviour.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/16961185','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/16961185"><span id="translatedtitle">Three-dimensional <span class="hlt">finite</span> element stress and <span class="hlt">strain</span> analysis of a transfemoral osseointegration implant.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Xu, Wei; Xu, Dong Hao; Crocombe, A D</p> <p>2006-08-01</p> <p>The percutaneous transfemoral osseointegration implant is an alternative technique for direct prosthetic limb attachment. In order to investigate the stress and <span class="hlt">strain</span> in the transfemoral osseointegration implant system, <span class="hlt">finite</span> element (FE) analyses were carried out using three-dimensional femur-implant models and the commercial FE software ABAQUS. The three-dimensional femoral model was reconstructed from presurgery CT scans of an above-knee amputee. The implant was then inserted into the femoral model using Boolean operations in CAD software. Under a typical walking load, stress and <span class="hlt">strain</span> from the femur-implant FE model were investigated. Stress concentrations were found near to the distal and proximal regions of the femur. To study the effect of different contact ratios between femur and implant, FE analyses were carried out using different implant diameters. The results showed that there were local stress variations near the contact discontinuity areas. A comparison was also made between the results of this study and a previous study using axisymmetric FE models. The results of the two studies revealed different stress levels, but good correlation was found in the overall stress distribution. PMID:16961185</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/24378472','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/24378472"><span id="translatedtitle">Quantitative investigation of ligament <span class="hlt">strains</span> during physical tests for sacroiliac joint pain using <span class="hlt">finite</span> element analysis.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Kim, Yoon Hyuk; Yao, Zhidong; Kim, Kyungsoo; Park, Won Man</p> <p>2014-06-01</p> <p>It may be assumed that the stability is affected when some ligaments are injured or loosened, and this joint instability causes sacroiliac joint pain. Several physical examinations have been used to diagnose sacroiliac pain and to isolate the source of the pain. However, more quantitative and objective information may be necessary to identify unstable or injured ligaments during these tests due to the lack of understanding of the quantitative relationship between the physical tests and the biomechanical parameters that may be related to pains in the sacroiliac joint and the surrounding ligaments. In this study, a three-dimensional <span class="hlt">finite</span> element model of the sacroiliac joint was developed and the biomechanical conditions for six typical physical tests such as the compression test, distraction test, sacral apex pressure test, thigh thrust test, Patrick's test, and Gaenslen's test were modelled. The sacroiliac joint contact pressure and ligament <span class="hlt">strain</span> were investigated for each test. The values of contact pressure and the combination of most highly <span class="hlt">strained</span> ligaments differed markedly among the tests. Therefore, these findings in combination with the physical tests would be helpful to identify the pain source and to understand the pain mechanism. Moreover, the technology provided in this study might be a useful tool to evaluate the physical tests, to improve the present test protocols, or to develop a new physical test protocol. PMID:24378472</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2001PhDT........27E','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2001PhDT........27E"><span id="translatedtitle">Study of the stress-<span class="hlt">strain</span> behavior of floodable rockfills by means of <span class="hlt">finite</span> difference formulated numerical simulations and instrumentation records</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Escuder Bueno, Ignacio</p> <p></p> <p>This Thesis studies the stress-<span class="hlt">strain</span> behavior of floodable rockfills, using data obtained from quality control of materials, control of construction and instrumentation records. As a case of study, a rockfill part of the final works for a new Madrid-Valencia motorway, located at Contreras Reservoir is used. Data were collected during construction (December 1997--August 1998) and are extended to July of 2000. After reviewing the state of art on properties of usual materials, models of behaviour, numerical tools and experiences dealing with studies based in combined analysis and field measurements, several works have been developed. Namely the synthesis of all available data, study of construction procedures, implementation of an analysis methodology and its application to the study of the stress-<span class="hlt">strain</span> behavior during and after construction. FLAC 2D (Itasca, 1994), an explicit <span class="hlt">finite</span> difference code, has been selected as numerical tool to perform the analysis, and results have been compared with measurements registered by total pressure and settlement cells. In order to improve the quality of analysis and to make use of all collected records to calibrate the models (taken on a weekly basis), the real constructive sequency has been simulated. Numerical calculation based in linear <span class="hlt">elastic</span>, non linear <span class="hlt">elastic</span>, elastoplastic and viscoelastic models have been performed. Newly developed routines have permitted to accomplish the upgrading of tangent parameters involved in non-linear hyperbolic formulation, calculation of creep deformation and settlements due to reservoir filling. As a result of the works, the stress-<span class="hlt">strain</span> behavior of the structure has been characterized, the importance of creep deformation from first stages of construction has been identified, and capability of usually assumed models in reproducing observed behavior has been evaluated.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=20130012796&hterms=database&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3Ddatabase','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=20130012796&hterms=database&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3Ddatabase"><span id="translatedtitle"><span class="hlt">Elastic</span>-Plastic J-Integral Solutions or Surface Cracks in Tension Using an Interpolation Methodology. Appendix C -- <span class="hlt">Finite</span> Element Models Solution Database File, Appendix D -- Benchmark <span class="hlt">Finite</span> Element Models Solution Database File</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Allen, Phillip A.; Wells, Douglas N.</p> <p>2013-01-01</p> <p>No closed form solutions exist for the <span class="hlt">elastic</span>-plastic J-integral for surface cracks due to the nonlinear, three-dimensional nature of the problem. Traditionally, each surface crack must be analyzed with a unique and time-consuming nonlinear <span class="hlt">finite</span> element analysis. To overcome this shortcoming, the authors have developed and analyzed an array of 600 3D nonlinear <span class="hlt">finite</span> element models for surface cracks in flat plates under tension loading. The solution space covers a wide range of crack shapes and depths (shape: 0.2 less than or equal to a/c less than or equal to 1, depth: 0.2 less than or equal to a/B less than or equal to 0.8) and material flow properties (<span class="hlt">elastic</span> modulus-to-yield ratio: 100 less than or equal to E/ys less than or equal to 1,000, and hardening: 3 less than or equal to n less than or equal to 20). The authors have developed a methodology for interpolating between the goemetric and material property variables that allows the user to reliably evaluate the full <span class="hlt">elastic</span>-plastic J-integral and force versus crack mouth opening displacement solution; thus, a solution can be obtained very rapidly by users without <span class="hlt">elastic</span>-plastic fracture mechanics modeling experience. Complete solutions for the 600 models and 25 additional benchmark models are provided in tabular format.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/21922957','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/21922957"><span id="translatedtitle">The use of a constant load to generate equivalent viscoelastic <span class="hlt">strain</span> in <span class="hlt">finite</span> element analysis of cemented prosthetic joints subjected to cyclic loading.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Lu, Z; McKellop, H A</p> <p>2011-08-01</p> <p>Polymers such as polymethyl-methacrylate (PMMA) surgical cement undergo <span class="hlt">elastic</span> and viscoelastic deformation (creep) in response to physiological cyclic loading. Theoretically, the effect of gradual creep deformation on the stresses, <span class="hlt">strains</span>, and displacements of a prosthetic joint can be evaluated by running a <span class="hlt">finite</span> element analysis (FEA) model through a large number of loading cycles. However, with complex (i.e. realistic) models, this approach may require extensive computational time, and may accumulate unacceptably large numerical errors over the many iterations of the model. The present study utilized a Fourier series to represent a periodic stress and incorporated it in the linear viscoelastic constitutive equation. It was demonstrated that, for a linear viscoelastic material, the time average (i.e. the constant in the Fourier series) of the cyclic stress determined the accumulated creep <span class="hlt">strain</span> and the sinusoidal components of the stress produced the periodic creep <span class="hlt">strain</span> with a zero average and negligible amplitude. For a geometrically linear FEA model, the solution based on a cyclic stress can be readily applied to an external cyclic load, that is, the creep <span class="hlt">strain</span> is determined by the time average of the cyclic load. While femoral component models were considered as geometrically non-linear, an FEA model of a femur implanted with an Exeter hip prosthesis showed that there was only a minor difference between the profile of the applied sinusoidal load and that of the resulting displacement. In such cases, applying the time average of a cyclic load to calculate the resulting creep <span class="hlt">strain</span> with a given duration of loading should expect to provide acceptable accuracy, with a marked reduction in the computational time. PMID:21922957</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=19750055656&hterms=rock+mechanics&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3Drock%2Bmechanics','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=19750055656&hterms=rock+mechanics&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3Drock%2Bmechanics"><span id="translatedtitle">Rock <span class="hlt">elastic</span> properties and near-surface structure at Taurus-Littrow. [<span class="hlt">strain</span> measurement of lunar basalt and breccia</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Trice, R.; Warren, N.; Anderson, O. L.</p> <p>1974-01-01</p> <p>Linear <span class="hlt">strain</span> measurements are presented for two lunar basalts, 14310,82 and 71055,15 and one breccia, 15498,23 to 5 kb hydrostatic pressure. Compressional and shear acoustic velocities to 5 kb are also presented for the basalts, 14310,82 and 71055,15. These <span class="hlt">elastic</span> properties, along with geological, seismological and rock mechanics considerations are consistent with a model of the structure of the Taurus-Littrow valley as follows, a thin surface regolith overlying a fractured mixture of basalt flows and ejecta material which in turn overlies a coherent breccia of highland ejecta debris.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4222193','PMC'); return false;" href="http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4222193"><span id="translatedtitle">Approaches to accommodate noisy data in the direct solution of inverse problems in incompressible plane-<span class="hlt">strain</span> <span class="hlt">elasticity</span></span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Albocher, U.; Barbone, P.E.; Richards, M.S.; Oberai, A.A.; Harari, I.</p> <p>2014-01-01</p> <p>We apply the adjoint weighted equation method (AWE) to the direct solution of inverse problems of incompressible plane <span class="hlt">strain</span> <span class="hlt">elasticity</span>. We show that based on untreated noisy displacements, the reconstruction of the shear modulus can be very poor. We link this poor performance to loss of coercivity of the weak form when treating problems with discontinuous coefficients. We demonstrate that by smoothing the displacements and appending a regularization term to the AWE formulation, a dramatic improvement in the reconstruction can be achieved. With these improvements, the advantages of the AWE method as a direct solution approach can be extended to a wider range of problems. PMID:25383085</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/1031358','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/1031358"><span id="translatedtitle">Measuring Depth-dependent Dislocation Densities and <span class="hlt">Elastic</span> <span class="hlt">Strains</span> in an Indented Ni-based Superalloy</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Barabash, O.M.; Santella, M.; Barabash, R.I.; Ice, G.E.; Tischler, J.</p> <p>2011-12-14</p> <p>The indentation-induced <span class="hlt">elastic</span>-plastic zone in an IN 740 Ni-based superalloy was studied by three-dimensional (3-D) x-ray microdiffraction and electron back scattering diffraction (EBSD). Large lattice reorientations and the formation of geometrically necessary dislocations are observed in the area with a radius of {approx}75 {mu}m. A residual compression zone is found close to the indent edge. An <span class="hlt">elastic</span>-plastic transition is observed at {approx}20 {mu}m from the indent edge. Depth dependent dislocation densities are determined at different distances from the indent edge.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AGUFM.T53E..02D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AGUFM.T53E..02D"><span id="translatedtitle">Circum-Slab Mantle Deformation: Insights from <span class="hlt">Finite</span> <span class="hlt">Strain</span> and Seismic Anisotropy</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Di Leo, J. F.; Li, Z. H.; Ribe, N. M.; Walker, A.; Wookey, J. M.; Kendall, J. M.</p> <p>2014-12-01</p> <p>Recent numerical modeling studies of the time-dependent development of texture and seismic anisotropy during subduction have shed light on how the mantle deforms as a slab subducts. It is thus becoming more and more clear that the term "mantle flow" may be too ambiguous in the context of subduction. For instance, it has been suggested that trench-parallel shear wave splitting fast directions (from SKS and source-side S splitting) on the seaward side need not necessarily be the result of trench-parallel movement (i.e., "flow") of mantle material, but are rather due to pure shear deformation in the sub-slab mantle. Here we present results of a numerical modeling study where we have systematically investigated how mantle propagation, <span class="hlt">finite</span> <span class="hlt">strain</span>, olivine lattice-preferred orientation (LPO), and SKS splitting vary with slab width in a fully dynamic 3-D subduction model. We find that even in the complex circum-slab flow field, the <span class="hlt">finite</span> <span class="hlt">strain</span> ellipsoid (FSE) is a good proxy for LPO. However, it does not necessarily align with the instantaneous mantle flow velocity vector. We identify two distinct domains with different deformation types in the central sub-slab upper mantle: simple shear induced by plate advance dominates at shallow depths and results in trench-normal fast splitting, while pure shear due to slab rollback dominates in the deeper mantle (above 410 km) and produces trench-parallel fast orientations. In our models, the SKS splitting pattern strongly depends on these two competing effects as well as the subduction partition ratio, γ = Xp/Xt, where Xp and Xt are the lengths of plate advance and trench retreat, respectively. If γ < 1 (narrow slabs, < 1000 km), trench-parallel fast directions are produced. In contrast, γ > 1 (wide slabs, > 1000 km), results in trench-normal fast splitting. This may explain the observed dichotomy in natural subduction zones of sub-slab fast splitting patterns (away from slab edges) usually being either trench-parallel or</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=19910000329&hterms=plywood&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3Dplywood','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=19910000329&hterms=plywood&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3Dplywood"><span id="translatedtitle">Triangular Element For Analyzing <span class="hlt">Elasticity</span> Of Laminates</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Martin, C. Wayne; Lung, S. F.; Gupta, K. K.</p> <p>1991-01-01</p> <p>Flat triangular element developed for use in <span class="hlt">finite</span>-element analyses of stress and <span class="hlt">strain</span> in laminated plates made of such materials as plywood or advanced fiber/epoxy composite materials. Has multiple layers, each of which can have different isotropic or orthotropic <span class="hlt">elastic</span> properties. Many such elements used in <span class="hlt">finite</span>-element mesh to calculate stiffness of plate. Formulation of element straight-forward, and calculation of its stiffness matrix simple and fast.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/1002812','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/1002812"><span id="translatedtitle">Indentation-induced localized deformation and <span class="hlt">elastic</span> <span class="hlt">strain</span> partitioning in composites at submicron length scale</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Barabash, R.I.; Bei, H.; Gao, Y.F.; Ice, G.E.</p> <p>2010-10-26</p> <p>Three-dimensional spatially resolved <span class="hlt">strains</span> were mapped in a model NiAl/Mo composite after nanoindentation. The depth-dependent <span class="hlt">strain</span> distributed in the two phases and partitioned across the composite interfaces is directly measured at submicron length scale using X-ray microdiffraction and compared with a detailed micromechanical stress analysis. It is shown that indentation-induced deformation in the composite material is distinct from deformation expected in a single-phase material. This difference arises in part from residual thermal <span class="hlt">strains</span> in both phases of the composite in the as-grown state. Interplay between residual thermal <span class="hlt">strains</span> and external mechanical <span class="hlt">strain</span> results in a complex distribution of dilatational <span class="hlt">strain</span> in the Mo fibers and NiAl matrix and is distinct in different locations within the indented area. Reversal of the <span class="hlt">strain</span> sign (e.g., alternating tensile/compressive/tensile <span class="hlt">strain</span> distribution) is observed in the NiAl matrix. Bending of the Mo fibers during indentation creates relatively large 1.5{sup o} misorientations between the different fibers and NiAl matrix. Compressive <span class="hlt">strain</span> along the <0 0 1> direction reached -0.017 in the Mo fibers and -0.007 in the NiAl matrix.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/27070511','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/27070511"><span id="translatedtitle">Surface-Controlled Orientational Transitions in <span class="hlt">Elastically</span> <span class="hlt">Strained</span> Films of Liquid Crystal That Are Triggered by Vapors of Toluene.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Bedolla Pantoja, Marco A; Abbott, Nicholas L</p> <p>2016-05-25</p> <p>We report the fabrication of chemically patterned microwells that enable the rapid and facile preparation (by spin coating and patterned dewetting) of thin films of liquid crystals (LCs) that have precise thicknesses (0.7-30 μm), are supported on chemically defined substrates, and have free upper surfaces. We use these microwells to prepare <span class="hlt">elastically</span> <span class="hlt">strained</span> nematic LC films supported on silica glass, gold, or polystyrene substrates and thereby characterize the response of the <span class="hlt">strained</span> LC films to vapors of toluene. We report that low concentrations of toluene vapor (<500 ppm) can partition into the LC to lower the anchoring energy of the LC on these substrates, thus allowing the <span class="hlt">elastic</span> energy of the <span class="hlt">strained</span> LC film to drive the LC films through an orientational transition. The central role of the toluene-induced change in surface anchoring energy is supported by additional experiments in which the response of the nematic LC to changes in film thickness and substrate identity are quantified. A simple thermodynamic model captures these trends and yielded estimates of anchoring energies (8-22 μJ/m(2)). Significantly, the orientational transitions observed in these <span class="hlt">strained</span> LC thin films occur at concentrations of toluene vapor that are almost 1 order of magnitude below those which lead to bulk phase transitions, and they are not triggered by exposure to water vapor. Overall, these results hint at principles for the design of responsive LC-based materials that can be triggered by concentrations of aromatic, volatile organic compounds that are relevant to human health. PMID:27070511</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/pages/biblio/1146110-analytical-elastic-plastic-contact-model-strain-hardening-frictional-effects-normal-oblique-impacts','SCIGOV-DOEP'); return false;" href="http://www.osti.gov/pages/biblio/1146110-analytical-elastic-plastic-contact-model-strain-hardening-frictional-effects-normal-oblique-impacts"><span id="translatedtitle">An analytical <span class="hlt">elastic</span> plastic contact model with <span class="hlt">strain</span> hardening and frictional effects for normal and oblique impacts</span></a></p> <p><a target="_blank" href="http://www.osti.gov/pages">DOE PAGESBeta</a></p> <p>Brake, M. R. W.</p> <p>2015-02-17</p> <p>Impact between metallic surfaces is a phenomenon that is ubiquitous in the design and analysis of mechanical systems. We found that to model this phenomenon, a new formulation for frictional elastic–plastic contact between two surfaces is developed. The formulation is developed to consider both frictional, oblique contact (of which normal, frictionless contact is a limiting case) and <span class="hlt">strain</span> hardening effects. The constitutive model for normal contact is developed as two contiguous loading domains: the <span class="hlt">elastic</span> regime and a transitionary region in which the plastic response of the materials develops and the <span class="hlt">elastic</span> response abates. For unloading, the constitutive model ismore » based on an <span class="hlt">elastic</span> process. Moreover, the normal contact model is assumed to only couple one-way with the frictional/tangential contact model, which results in the normal contact model being independent of the frictional effects. Frictional, tangential contact is modeled using a microslip model that is developed to consider the pressure distribution that develops from the elastic–plastic normal contact. This model is validated through comparisons with experimental results reported in the literature, and is demonstrated to be significantly more accurate than 10 other normal contact models and three other tangential contact models found in the literature.« less</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/1146110','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/1146110"><span id="translatedtitle">An analytical <span class="hlt">elastic</span> plastic contact model with <span class="hlt">strain</span> hardening and frictional effects for normal and oblique impacts</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Brake, M. R. W.</p> <p>2015-02-17</p> <p>Impact between metallic surfaces is a phenomenon that is ubiquitous in the design and analysis of mechanical systems. We found that to model this phenomenon, a new formulation for frictional elastic–plastic contact between two surfaces is developed. The formulation is developed to consider both frictional, oblique contact (of which normal, frictionless contact is a limiting case) and <span class="hlt">strain</span> hardening effects. The constitutive model for normal contact is developed as two contiguous loading domains: the <span class="hlt">elastic</span> regime and a transitionary region in which the plastic response of the materials develops and the <span class="hlt">elastic</span> response abates. For unloading, the constitutive model is based on an <span class="hlt">elastic</span> process. Moreover, the normal contact model is assumed to only couple one-way with the frictional/tangential contact model, which results in the normal contact model being independent of the frictional effects. Frictional, tangential contact is modeled using a microslip model that is developed to consider the pressure distribution that develops from the elastic–plastic normal contact. This model is validated through comparisons with experimental results reported in the literature, and is demonstrated to be significantly more accurate than 10 other normal contact models and three other tangential contact models found in the literature.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014PhDT.......226A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014PhDT.......226A"><span id="translatedtitle">Overall mechanical response of soft composite materials with particulate microstructure at <span class="hlt">finite</span> <span class="hlt">strains</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Avazmohammadi, Reza</p> <p></p> <p> behavior of particulate composites consisting of elasto-viscoplastic matrices and <span class="hlt">elastic</span>, spheroidal particles, subjected to small <span class="hlt">strains</span>. Here, we explore the effect of the local properties and loading conditions on the effective behavior and field statistics in these composites for the case of <span class="hlt">elastic</span>-ideally plastic matrices.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li class="active"><span>16</span></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_16 --> <div id="page_17" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li class="active"><span>17</span></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="321"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2016CPL...658..130D&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2016CPL...658..130D&link_type=ABSTRACT"><span id="translatedtitle"><span class="hlt">Elastic</span> <span class="hlt">strain</span> effects on the photocatalytic TiO2 nanofilm: Utilizing the martensitic surface relief of FeNiCoTi alloy substrate</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Du, Minshu; Wan, Qiong; Wang, Zhongqiang; Cui, Lishan</p> <p>2016-08-01</p> <p>The application of <span class="hlt">elastic</span> <span class="hlt">strain</span> is a promising approach for tuning bandgap of semiconductors; however, the attainment of a simple method for introducing <span class="hlt">strain</span> has been a major challenge. Here, martensitic surface relief of FeNiCoTi substrate was utilized to tensilely <span class="hlt">strain</span> TiO2 nanofilm successfully. The <span class="hlt">elastic</span> <span class="hlt">strain</span> effects of photocatalysis were also investigated. It was showed that tensile <span class="hlt">strain</span> reduced the bandgap of TiO2 nanofilm by 50 meV and contributed to a 33.8% faster photodegradation rate of methyl orange, also the photocurrent of the water oxidation reaction of <span class="hlt">strained</span> TiO2 was 1.4 times as high as that of unstrained nanofilm.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/23804949','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/23804949"><span id="translatedtitle">Determination of remodeling parameters for a <span class="hlt">strain</span>-adaptive <span class="hlt">finite</span> element model of the distal ulna.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Neuert, Mark A C; Dunning, Cynthia E</p> <p>2013-09-01</p> <p><span class="hlt">Strain</span> energy-based adaptive material models are used to predict bone resorption resulting from stress shielding induced by prosthetic joint implants. Generally, such models are governed by two key parameters: a homeostatic <span class="hlt">strain</span>-energy state (K) and a threshold deviation from this state required to initiate bone reformation (s). A refinement procedure has been performed to estimate these parameters in the femur and glenoid; this study investigates the specific influences of these parameters on resulting density distributions in the distal ulna. A <span class="hlt">finite</span> element model of a human ulna was created using micro-computed tomography (µCT) data, initialized to a homogeneous density distribution, and subjected to approximate in vivo loading. Values for K and s were tested, and the resulting steady-state density distribution compared with values derived from µCT images. The sensitivity of these parameters to initial conditions was examined by altering the initial homogeneous density value. The refined model parameters selected were then applied to six additional human ulnae to determine their performance across individuals. Model accuracy using the refined parameters was found to be comparable with that found in previous studies of the glenoid and femur, and gross bone structures, such as the cortical shell and medullary canal, were reproduced. The model was found to be insensitive to initial conditions; however, a fair degree of variation was observed between the six specimens. This work represents an important contribution to the study of changes in load transfer in the distal ulna following the implementation of commercial orthopedic implants. PMID:23804949</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/12455844','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/12455844"><span id="translatedtitle">Analysis of <span class="hlt">strain</span> and stress in the equine hoof capsule using <span class="hlt">finite</span> element methods: comparison with principal <span class="hlt">strains</span> recorded in vivo.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Thomason, J J; McClinchey, H L; Jofriet, J C</p> <p>2002-11-01</p> <p><span class="hlt">Finite</span>-element (FE) methods have great potential in equine biomechanics in evaluating mechanical stresses and <span class="hlt">strains</span> in tissues deep within the hoof. In this study, we critically assessed that potential by comparing results of FE analyses of capsular <span class="hlt">strain</span> with in vivo data. Nine FE models were developed, corresponding to the shape of hooves for which in vivo principal <span class="hlt">strain</span> data are available. Each model had the wall, laminar junction, sole and distal phalanx (PIII). In a first loading condition (LC1), force is distributed uniformly to the bearing surface of the wall to determine reaction forces and moment on PIII. These reaction forces were subsequently applied to PIII in loading condition 2 (LC2) to simulate loading via the skeleton. Magnitude of the force resultant was equivalent to the vertical force on the hoof at midstance. Principal compressive <span class="hlt">strains</span> epsilon2 were calculated at the locations of 5 rosette gauges on the real hooves and are compared with the in vivo <span class="hlt">strains</span> at midstance. FE <span class="hlt">strains</span> were from 16 to 221% of comparable in vivo values, averaging 104%. All models in this, and reports by other workers, show predominance of stress and <span class="hlt">strain</span> at the toe to a greater extent than in the real hoof. The primary conclusion is that FE modelling of <span class="hlt">strain</span> in the hoof capsule or deeper tissues of individual horses should not be attempted without corroborating experimental data. PMID:12455844</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19930004485','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19930004485"><span id="translatedtitle"><span class="hlt">Elastic</span> and plastic <span class="hlt">strain</span> measurement in high temperature environment using laser speckle</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Chiang, Fu-Pen</p> <p>1992-01-01</p> <p>Two laser speckle methods are described to measure <span class="hlt">strain</span> in high temperature environment and thermal <span class="hlt">strain</span> caused by high temperature. Both are non-contact, non-destructive and remote sensing techniques that can be automated. The methods have different but overlapping ranges of application with one being more suitable for large plastic deformation.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19970018530','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19970018530"><span id="translatedtitle">ZIP2DL: An <span class="hlt">Elastic</span>-Plastic, Large-Rotation <span class="hlt">Finite</span>-Element Stress Analysis and Crack-Growth Simulation Program</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Deng, Xiaomin; Newman, James C., Jr.</p> <p>1997-01-01</p> <p>ZIP2DL is a two-dimensional, <span class="hlt">elastic</span>-plastic finte element program for stress analysis and crack growth simulations, developed for the NASA Langley Research Center. It has many of the salient features of the ZIP2D program. For example, ZIP2DL contains five material models (linearly <span class="hlt">elastic</span>, <span class="hlt">elastic</span>-perfectly plastic, power-law hardening, linear hardening, and multi-linear hardening models), and it can simulate mixed-mode crack growth for prescribed crack growth paths under plane stress, plane <span class="hlt">strain</span> and mixed state of stress conditions. Further, as an extension of ZIP2D, it also includes a number of new capabilities. The large-deformation kinematics in ZIP2DL will allow it to handle <span class="hlt">elastic</span> problems with large <span class="hlt">strains</span> and large rotations, and <span class="hlt">elastic</span>-plastic problems with small <span class="hlt">strains</span> and large rotations. Loading conditions in terms of surface traction, concentrated load, and nodal displacement can be applied with a default linear time dependence or they can be programmed according to a user-defined time dependence through a user subroutine. The restart capability of ZIP2DL will make it possible to stop the execution of the program at any time, analyze the results and/or modify execution options and resume and continue the execution of the program. This report includes three sectons: a theoretical manual section, a user manual section, and an example manual secton. In the theoretical secton, the mathematics behind the various aspects of the program are concisely outlined. In the user manual section, a line-by-line explanation of the input data is given. In the example manual secton, three types of examples are presented to demonstrate the accuracy and illustrate the use of this program.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2016CMAME.306..151S&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2016CMAME.306..151S&link_type=ABSTRACT"><span id="translatedtitle">Efficient implicit integration for <span class="hlt">finite-strain</span> viscoplasticity with a nested multiplicative split</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Shutov, A. V.</p> <p>2016-07-01</p> <p>An efficient and reliable stress computation algorithm is presented, which is based on implicit integration of the local evolution equations of multiplicative <span class="hlt">finite-strain</span> plasticity/viscoplasticity. The algorithm is illustrated by an example involving a combined nonlinear isotropic/kinematic hardening; numerous backstress tensors are employed for a better description of the material behavior. The considered material model exhibits the so-called weak invariance under arbitrary isochoric changes of the reference configuration, and the presented algorithm retains this useful property. Even more: the weak invariance serves as a guide in constructing this algorithm. The constraint of inelastic incompressibility is exactly preserved as well. The proposed method is first-order accurate. Concerning the accuracy of the stress computation, the new algorithm is comparable to the Euler Backward method with a subsequent correction of incompressibility (EBMSC) and the classical exponential method (EM). Regarding the computational efficiency, the new algorithm is superior to the EBMSC and EM. Some accuracy tests are presented using parameters of the aluminum alloy 5754-O and the 42CrMo4 steel. FEM solutions of two boundary value problems using MSC.MARC are presented to show the correctness of the numerical implementation.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4038650','PMC'); return false;" href="http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4038650"><span id="translatedtitle">DT-REFinD: Diffusion Tensor Registration With Exact <span class="hlt">Finite-Strain</span> Differential</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Vercauteren, Tom; Fillard, Pierre; Peyrat, Jean-Marc; Pennec, Xavier; Golland, Polina; Ayache, Nicholas; Clatz, Olivier</p> <p>2014-01-01</p> <p>In this paper, we propose the DT-REFinD algorithm for the diffeomorphic nonlinear registration of diffusion tensor images. Unlike scalar images, deforming tensor images requires choosing both a reorientation strategy and an interpolation scheme. Current diffusion tensor registration algorithms that use full tensor information face difficulties in computing the differential of the tensor reorientation strategy and consequently, these methods often approximate the gradient of the objective function. In the case of the <span class="hlt">finite-strain</span> (FS) reorientation strategy, we borrow results from the pose estimation literature in computer vision to derive an analytical gradient of the registration objective function. By utilizing the closed-form gradient and the velocity field representation of one parameter subgroups of diffeomorphisms, the resulting registration algorithm is diffeomorphic and fast. We contrast the algorithm with a traditional FS alternative that ignores the reorientation in the gradient computation. We show that the exact gradient leads to significantly better registration at the cost of computation time. Independently of the choice of Euclidean or Log-Euclidean interpolation and sum of squared differences dissimilarity measure, the exact gradient achieves better alignment over an entire spectrum of deformation penalties. Alignment quality is assessed with a battery of metrics including tensor overlap, fractional anisotropy, inverse consistency and closeness to synthetic warps. The improvements persist even when a different reorientation scheme, preservation of principal directions, is used to apply the final deformations. PMID:19556193</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010ApSS..256.5210G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010ApSS..256.5210G"><span id="translatedtitle">Influence of <span class="hlt">elastic</span> <span class="hlt">strains</span> on the adsorption process in porous materials. Thermodynamics and experiment</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Grosman, A.; Ortega, C.</p> <p>2010-06-01</p> <p>If we disregard the shape of the boundary hysteresis loop, H1 for SBA-15, MCM-41 and KIT-6, H2 for p +-type porous silicon and porous glass, the hysteretic features inside the loop are qualitatively the same for all these systems and show that none of them are composed of independent pores whether the pores are interconnected or not. We hence believe that the physical parameter which couples the pores is not the interconnectivity but the <span class="hlt">elastic</span> deformation of the porous matrix. The thermodynamic approach we develop includes the <span class="hlt">elastic</span> energy of the solid. We show that the variation of the surface free energy, which is proportional to the deformation of the porous matrix, is an important component of the total free energy. With porous silicon, we experimentally show that a stress external to the porous matrix exerted by the substrate on which it is supported significantly increases the total free energy and the adsorbed amount and decreases the condensation pressure compared to that of the same porous matrix detached from its substrate which is the relaxed state of the supported layer. This stress can be partly relaxed by making thicker porous layers due to the breaking of Si-Si bonds. This results in the shift of the isotherms towards that of the membrane. We propose a new interaction mechanism occurring through the pore wall <span class="hlt">elastic</span> deformation in which the external mechanical stress is imposed on a given pore by its neighbours.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19880004353','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19880004353"><span id="translatedtitle"><span class="hlt">Strain</span>-energy-release rate analysis of the end-notched flexure specimen using the <span class="hlt">finite</span>-element method</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Salpekar, S. A.; Raju, I. S.; Obrien, T. K.</p> <p>1987-01-01</p> <p>Two-dimensional <span class="hlt">finite</span>-element analysis of the end-notched flexure specimen was performed using 8-node isoparametric, parabolic elements to evaluate compliance and mode II <span class="hlt">strain</span> energy release rates, G sub II. The G sub II values were computed using two different techniques: the virtural crack-closure technique (VCCT) and the rate of change of compliance with crack length (compliance derivative method). The analysis was performed for various crack-length-to-semi-span (a/L) ratios ranging from 0.2 to 0.9. Three material systems representing a wide range of material properties were analyzed. The compliance and <span class="hlt">strain</span> energy release rates of the specimen calculated with the present <span class="hlt">finite</span>-element analysis agree very well with beam theory equations including transverse shear. The G sub II values calculated using the compliance derivative method compared extremely well with those calculated using the VCCT. The G sub II values obtained by the compliance derivative method using the top or bottom beam deflections agreed closely with each other. The <span class="hlt">strain</span> energy release rates from a plane-stress analysis were higher than the plane-<span class="hlt">strain</span> values by only a small percentage, indicating that either assumption may be used in the analysis. The G sub II values for one material system calculated from the <span class="hlt">finite</span>-element analysis agreed with one solution in the literature and disagreed with the other solution in the literature.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/14977217','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/14977217"><span id="translatedtitle">Effect of a degraded core on the mechanical behaviour of tissue-engineered cartilage constructs: a poro-<span class="hlt">elastic</span> <span class="hlt">finite</span> element analysis.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Kelly, D J; Prendergast, P J</p> <p>2004-01-01</p> <p>The structure and functionality of tissue-engineered cartilage is determined by the tissue culture conditions and mechanical conditioning during growth. The quality of tissue-engineered cartilage can be evaluated using tests such as the confined compression test. Tissue-engineered cartilage constructs usually consist of an outer layer of cartilage and an inner core of either undeveloped cartilage or degrading scaffold material. A biphasic poro-<span class="hlt">elastic</span> <span class="hlt">finite</span> element model was used to demonstrate how such a core influences the reaction force-time curve obtained from a confined compression test. The <span class="hlt">finite</span> element model predicted that higher volumes of degraded scaffold in the inner core would reduce the aggregate modulus calculated from the confined compression test and raised the estimate of tissue permeability. The predicted aggregate modulus reduced from 0.135 MPa, for a homogenous construct, to 0.068 MPa, for a construct that was only 70% cartilaginous. It was found that biphasic poro-<span class="hlt">elastic</span> <span class="hlt">finite</span> modelling should be used in preference to a one-dimensional model that assumed homogeneity in estimating the properties of tissue-engineered cartilage. PMID:14977217</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016JAP...119b5302O','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016JAP...119b5302O"><span id="translatedtitle">Extraction of <span class="hlt">elastic</span> modulus of porous ultra-thin low-k films by two-dimensional <span class="hlt">finite</span>-element simulations of nanoindentation</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Okudur, O. O.; Vanstreels, K.; De Wolf, I.; Hangen, U.</p> <p>2016-01-01</p> <p>Continuous scaling of integrated circuits has led to the introduction of highly porous low dielectric constant (low-k) materials, whose inferior mechanical properties raise concerns regarding the reliability of integrated circuits. Nanoindentation is proven to be a straightforward method to study mechanical properties of films. However, in the case of low-k, the measurement and analysis are complex due to the porous nature of the films and reduced film thicknesses which give rise to substrate effects. A methodology that combines nanoindentation experiments with <span class="hlt">finite</span>-element simulations is proposed and validated in this study to extract the substrate-free <span class="hlt">elastic</span> modulus of porous ultra-thin low-k films. Furthermore, it is shown that imperfections of the nanoindentation probe significantly affect the <span class="hlt">finite</span>-element results. An effective analytical method that captures the actual nanoindenter behavior upon indentation is proposed by taking both tip radius and conical imperfections into account. Using this method combined with <span class="hlt">finite</span> element modeling, the <span class="hlt">elastic</span> modulus of sub-100 nm thick low-k films is successfully extracted. Standard indentation tests clearly overestimated the actual modulus for such thin films, which emphasizes the importance of the proposed methodology.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015ApPhL.106w3702H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015ApPhL.106w3702H"><span id="translatedtitle">Analysis of the effects of curvature and thickness on <span class="hlt">elastic</span> wave velocity in cornea-like structures by <span class="hlt">finite</span> element modeling and optical coherence elastography</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Han, Zhaolong; Li, Jiasong; Singh, Manmohan; Aglyamov, Salavat R.; Wu, Chen; Liu, Chih-hao; Larin, Kirill V.</p> <p>2015-06-01</p> <p>Wave models that have been used to extract the biomechanical properties of the cornea from the propagation of an <span class="hlt">elastic</span> wave are based on an assumption of thin-plate geometry. However, this assumption does not account for the effects of corneal curvature and thickness. This study conducts <span class="hlt">finite</span> element (FE) simulations on four types of cornea-like structures as well as optical coherence elastography (OCE) experiments on contact lenses and tissue-mimicking phantoms to investigate the effects of curvature and thickness on the group velocity of an <span class="hlt">elastic</span> wave. The <span class="hlt">elastic</span> wave velocity as determined by FE simulations and OCE of a spherical shell section decreased from ˜2.8 m/s to ˜2.2 m/s as the radius of curvature increased from 19.1 mm to 47.7 mm and increased from ˜3.0 m/s to ˜4.1 m/s as the thickness of the agar phantom increased from 1.9 mm to 5.6 mm. Both the FE simulation and OCE results confirm that the group velocity of the <span class="hlt">elastic</span> wave decreases with radius of curvature but increases with thickness. These results demonstrate that the effects of the curvature and thickness must be considered in the further development of accurate wave models for reconstructing biomechanical properties of the cornea.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4464060','PMC'); return false;" href="http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4464060"><span id="translatedtitle">Analysis of the effects of curvature and thickness on <span class="hlt">elastic</span> wave velocity in cornea-like structures by <span class="hlt">finite</span> element modeling and optical coherence elastography</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Li, Jiasong; Singh, Manmohan; Aglyamov, Salavat R.; Wu, Chen; Liu, Chih-hao; Larin, Kirill V.</p> <p>2015-01-01</p> <p>Wave models that have been used to extract the biomechanical properties of the cornea from the propagation of an <span class="hlt">elastic</span> wave are based on an assumption of thin-plate geometry. However, this assumption does not account for the effects of corneal curvature and thickness. This study conducts <span class="hlt">finite</span> element (FE) simulations on four types of cornea-like structures as well as optical coherence elastography (OCE) experiments on contact lenses and tissue-mimicking phantoms to investigate the effects of curvature and thickness on the group velocity of an <span class="hlt">elastic</span> wave. The <span class="hlt">elastic</span> wave velocity as determined by FE simulations and OCE of a spherical shell section decreased from ∼2.8 m/s to ∼2.2 m/s as the radius of curvature increased from 19.1 mm to 47.7 mm and increased from ∼3.0 m/s to ∼4.1 m/s as the thickness of the agar phantom increased from 1.9 mm to 5.6 mm. Both the FE simulation and OCE results confirm that the group velocity of the <span class="hlt">elastic</span> wave decreases with radius of curvature but increases with thickness. These results demonstrate that the effects of the curvature and thickness must be considered in the further development of accurate wave models for reconstructing biomechanical properties of the cornea. PMID:26130825</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016PhRvB..94e4111M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016PhRvB..94e4111M"><span id="translatedtitle"><span class="hlt">Finite</span>-temperature <span class="hlt">elastic</span> constants of paramagnetic materials within the disordered local moment picture from ab initio molecular dynamics calculations</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Mozafari, E.; Shulumba, N.; Steneteg, P.; Alling, B.; Abrikosov, Igor A.</p> <p>2016-08-01</p> <p>We present a theoretical scheme to calculate the <span class="hlt">elastic</span> constants of magnetic materials in the high-temperature paramagnetic state. Our approach is based on a combination of disordered local moments picture and ab initio molecular dynamics (DLM-MD). Moreover, we investigate a possibility to enhance the efficiency of the simulations of <span class="hlt">elastic</span> properties using the recently introduced method: symmetry imposed force constant temperature-dependent effective potential (SIFC-TDEP). We have chosen cubic paramagnetic CrN as a model system. This is done due to its technological importance and its demonstrated strong coupling between magnetic and lattice degrees of freedom. We have studied the temperature-dependent single-crystal and polycrystalline <span class="hlt">elastic</span> constants of paramagentic CrN up to 1200 K. The obtained results at T = 300 K agree well with the experimental values of polycrystalline <span class="hlt">elastic</span> constants as well as the Poisson ratio at room temperature. We observe that the Young's modulus is strongly dependent on temperature, decreasing by ˜14 % from T = 300 K to 1200 K. In addition we have studied the <span class="hlt">elastic</span> anisotropy of CrN as a function of temperature and we observe that CrN becomes substantially more isotropic as the temperature increases. We demonstrate that the use of Birch law may lead to substantial errors for calculations of temperature induced changes of <span class="hlt">elastic</span> moduli. The proposed methodology can be used for accurate predictions of mechanical properties of magnetic materials at temperatures above their magnetic order-disorder phase transition.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015ApCM...22..711L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015ApCM...22..711L"><span id="translatedtitle"><span class="hlt">Finite</span> Element Analysis of Progressive Failure and <span class="hlt">Strain</span> Localization of Carbon Fiber/Epoxy Composite Laminates by ABAQUS</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Liu, P. F.; Yang, Y. H.; Gu, Z. P.; Zheng, J. Y.</p> <p>2015-12-01</p> <p>Interaction mechanism between the intralaminar damage and interlaminar delamination of composite laminates is always a challenging issue. It is important to consider the progressive failure and <span class="hlt">strain</span> softening behaviors simultaneously during the damage modeling and numerical simulation of composites using FEA. This paper performs three-dimensional <span class="hlt">finite</span> element analysis of the progressive failure and <span class="hlt">strain</span> localization of composites using FEA. An intralaminar progressive failure model based on the <span class="hlt">strain</span> components is proposed and the nonlinear cohesive model is used to predict the delamination growth. In particular, the nonlocal integral theory which introduces a length scale into the governing equations is used to regularize the <span class="hlt">strain</span> localization problems of composite structures. Special <span class="hlt">finite</span> element codes are developed using ABAQUS to predict the intralaminar and interlaminar damage evolution of composites simultaneously. The carbon fiber/epoxy composite laminates with a central hole demonstrates the developed theoretical models and numerical algorithm by discussing the effects of the mesh sizes and layups patterns. It is shown the <span class="hlt">strain</span> localization problem can be well solved in the progressive failure analysis of composites when the energy dissipation due to the damage of the fiber, matrix and interface occurs at a relatively wide area.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/5591849','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/5591849"><span id="translatedtitle">ACCEPT: a three-dimensional <span class="hlt">finite</span> element program for large deformation <span class="hlt">elastic</span>-plastic-creep analysis of pressurized tubes (LWBR/AWBA Development Program)</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Hutula, D.N.; Wiancko, B.E.</p> <p>1980-03-01</p> <p>ACCEPT is a three-dimensional <span class="hlt">finite</span> element computer program for analysis of large-deformation <span class="hlt">elastic</span>-plastic-creep response of Zircaloy tubes subjected to temperature, surface pressures, and axial force. A twenty-mode, tri-quadratic, isoparametric element is used along with a Zircaloy materials model. A linear time-incremental procedure with residual force correction is used to solve for the time-dependent response. The program features an algorithm which automatically chooses the time step sizes to control the accuracy and numerical stability of the solution. A contact-separation capability allows modeling of interaction of reactor fuel rod cladding with fuel pellets or external supports.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2005ApPhL..86f1909T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2005ApPhL..86f1909T"><span id="translatedtitle">Direct evidence for compressive <span class="hlt">elastic</span> <span class="hlt">strain</span> at ground surfaces of nanocomposite ceramics</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Tanner, B. K.; Wu, H. Z.; Roberts, S. G.</p> <p>2005-02-01</p> <p>High-resolution grazing incidence x-ray powder diffraction has been used to provide direct evidence for the existence of a uniform compressive <span class="hlt">strain</span> close to the surface of ground alumina/SiC nanocomposites. No such <span class="hlt">strain</span> is found in ground surfaces of single-phase alumina or polished surfaces of nanocomposite. The <span class="hlt">strain</span> in the ground nanocomposite is found to be perpendicular to the grinding direction and disappears on annealing at 1250°C. Such a compressive stress provides a mechanism for enhancing the strength of the nanocomposite, by opposing any tensile loading tending to open surface flaws. The origin of the stresses probably lies in the enhanced grain boundary strength in the nanocomposite alumina-silicon carbide compared to alumina.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4732735','PMC'); return false;" href="http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4732735"><span id="translatedtitle"><span class="hlt">Strain</span>-rate Dependence of <span class="hlt">Elastic</span> Modulus Reveals Silver Nanoparticle Induced Cytotoxicity</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Caporizzo, Matthew Alexander; Roco, Charles M.; Ferrer, Maria Carme Coll; Grady, Martha E.; Parrish, Emmabeth; Eckmann, David M.; Composto, Russell John</p> <p>2015-01-01</p> <p>Force-displacement measurements are taken at different rates with an atomic force microscope to assess the correlation between cell health and cell viscoelasticity in THP-1 cells that have been treated with a novel drug carrier. A variable indentation-rate viscoelastic analysis, VIVA, is employed to identify the relaxation time of the cells that are known to exhibit a frequency dependent stiffness. The VIVA agrees with a fluorescent viability assay. This indicates that dextran-lysozyme drug carriers are biocompatible and deliver concentrated toxic material (rhodamine or silver nanoparticles) to the cytoplasm of THP-1 cells. By modelling the frequency dependence of the <span class="hlt">elastic</span> modulus, the VIVA provides three metrics of cytoplasmic viscoelasticity: a low frequency modulus, a high frequency modulus and viscosity. The signature of cytotoxicity by rhodamine or silver exposure is a frequency independent twofold increase in the <span class="hlt">elastic</span> modulus and cytoplasmic viscosity, while the cytoskeletal relaxation time remains unchanged. This is consistent with the known toxic mechanism of silver nanoparticles, where metabolic stress causes an increase in the rigidity of the cytoplasm. A variable indentation-rate viscoelastic analysis is presented as a straightforward method to promote the self-consistent comparison between cells. This is paramount to the development of early diagnosis and treatment of disease. PMID:26834855</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009APS..SHK.D4001R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009APS..SHK.D4001R"><span id="translatedtitle">The Young's modulus of 1018 steel and 6061-T6 aluminum measured from quasi-static to <span class="hlt">elastic</span> precursor <span class="hlt">strain</span>-rates</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Rae, Philip; Trujillo, Carl; Gray, Rusty</p> <p>2009-06-01</p> <p>It is commonly assumed in engineering and physics that the <span class="hlt">elastic</span> moduli of metals is independent of <span class="hlt">strain</span>-rate, but is a weak function of temperature. An extensive literature search however has failed to find any citable reference in which the Young's modulus of any pedigreed metal was measured over a wide variety of <span class="hlt">strain</span>-rates. To rectify this, samples of pedigreed 1018 steel and 6061-T6 aluminum have been tested at <span class="hlt">strain</span>-rates from 10-4 s-1 to 10^6 s-1. Low <span class="hlt">strain</span>-rate data (10-4-10-2 s-1)was obtained from commercial bonded <span class="hlt">strain</span> gauges. Intermediate rate data ( 10-4 s-1) was obtained from time of flight ultrasonic measurements. Shock rate data was obtained by examining the <span class="hlt">elastic</span> precursor using shock pins and PDV (photonic Doppler velocimetry). Correction for the adiabatic versus thermal nature of the disparate <span class="hlt">strain</span>-rate regimes have been made. Additionally, the implications of the uniaxial <span class="hlt">strain</span> nature of the shock <span class="hlt">elastic</span> precursor are examined with respect to comparison with uniaxial stress lower rate data.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/26067742','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/26067742"><span id="translatedtitle">A Coupled Experiment-<span class="hlt">finite</span> Element Modeling Methodology for Assessing High <span class="hlt">Strain</span> Rate Mechanical Response of Soft Biomaterials.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Prabhu, Rajkumar; Whittington, Wilburn R; Patnaik, Sourav S; Mao, Yuxiong; Begonia, Mark T; Williams, Lakiesha N; Liao, Jun; Horstemeyer, M F</p> <p>2015-01-01</p> <p>This study offers a combined experimental and <span class="hlt">finite</span> element (FE) simulation approach for examining the mechanical behavior of soft biomaterials (e.g. brain, liver, tendon, fat, etc.) when exposed to high <span class="hlt">strain</span> rates. This study utilized a Split-Hopkinson Pressure Bar (SHPB) to generate <span class="hlt">strain</span> rates of 100-1,500 sec(-1). The SHPB employed a striker bar consisting of a viscoelastic material (polycarbonate). A sample of the biomaterial was obtained shortly postmortem and prepared for SHPB testing. The specimen was interposed between the incident and transmitted bars, and the pneumatic components of the SHPB were activated to drive the striker bar toward the incident bar. The resulting impact generated a compressive stress wave (i.e. incident wave) that traveled through the incident bar. When the compressive stress wave reached the end of the incident bar, a portion continued forward through the sample and transmitted bar (i.e. transmitted wave) while another portion reversed through the incident bar as a tensile wave (i.e. reflected wave). These waves were measured using <span class="hlt">strain</span> gages mounted on the incident and transmitted bars. The true stress-<span class="hlt">strain</span> behavior of the sample was determined from equations based on wave propagation and dynamic force equilibrium. The experimental stress-<span class="hlt">strain</span> response was three dimensional in nature because the specimen bulged. As such, the hydrostatic stress (first invariant) was used to generate the stress-<span class="hlt">strain</span> response. In order to extract the uniaxial (one-dimensional) mechanical response of the tissue, an iterative coupled optimization was performed using experimental results and <span class="hlt">Finite</span> Element Analysis (FEA), which contained an Internal State Variable (ISV) material model used for the tissue. The ISV material model used in the FE simulations of the experimental setup was iteratively calibrated (i.e. optimized) to the experimental data such that the experiment and FEA <span class="hlt">strain</span> gage values and first invariant of stresses were in</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li class="active"><span>17</span></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_17 --> <div id="page_18" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li class="active"><span>18</span></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="341"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=19760048246&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3Do','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=19760048246&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3Do"><span id="translatedtitle"><span class="hlt">Finite</span> element solutions for crack-tip behavior in small-scale yielding</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Tracey, D. M.</p> <p>1976-01-01</p> <p>The subject considered is the stress and deformation fields in a cracked <span class="hlt">elastic</span>-plastic power law hardening material under plane <span class="hlt">strain</span> tensile loading. An incremental plasticity <span class="hlt">finite</span> element formulation is developed for accurate analysis of the complete field problem including the extensively deformed near tip region, the <span class="hlt">elastic</span>-plastic region, and the remote <span class="hlt">elastic</span> region. The formulation has general applicability and was used to solve the small scale yielding problem for a set of material hardening exponents. Distributions of stress, <span class="hlt">strain</span>, and crack opening displacement at the crack tip and through the <span class="hlt">elastic</span>-plastic zone are presented as a function of the <span class="hlt">elastic</span> stress intensity factor and material properties.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016SPIE.9790E..06C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016SPIE.9790E..06C"><span id="translatedtitle">Fast myocardial <span class="hlt">strain</span> estimation from 3D ultrasound through <span class="hlt">elastic</span> image registration with analytic regularization</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Chakraborty, Bidisha; Heyde, Brecht; Alessandrini, Martino; D'hooge, Jan</p> <p>2016-04-01</p> <p>Image registration techniques using free-form deformation models have shown promising results for 3D myocardial <span class="hlt">strain</span> estimation from ultrasound. However, the use of this technique has mostly been limited to research institutes due to the high computational demand, which is primarily due to the computational load of the regularization term ensuring spatially smooth cardiac <span class="hlt">strain</span> estimates. Indeed, this term typically requires evaluating derivatives of the transformation field numerically in each voxel of the image during every iteration of the optimization process. In this paper, we replace this time-consuming step with a closed-form solution directly associated with the transformation field resulting in a speed up factor of ~10-60,000, for a typical 3D B-mode image of 2503 and 5003 voxels, depending upon the size and the parametrization of the transformation field. The performance of the numeric and the analytic solutions was contrasted by computing tracking and <span class="hlt">strain</span> accuracy on two realistic synthetic 3D cardiac ultrasound sequences, mimicking two ischemic motion patterns. Mean and standard deviation of the displacement errors over the cardiac cycle for the numeric and analytic solutions were 0.68+/-0.40 mm and 0.75+/-0.43 mm respectively. Correlations for the radial, longitudinal and circumferential <span class="hlt">strain</span> components at end-systole were 0.89, 0.83 and 0.95 versus 0.90, 0.88 and 0.92 for the numeric and analytic regularization respectively. The analytic solution matched the performance of the numeric solution as no statistically significant differences (p>0.05) were found when expressed in terms of bias or limits-of-agreement.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/930417','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/930417"><span id="translatedtitle">Diffraction Profiles of <span class="hlt">Elasticity</span> Bent Single Crystals with Constant <span class="hlt">Strain</span> Gradients</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Yan,H.; Kalenci, O.; Noyan, I.</p> <p>2007-01-01</p> <p>This work presents a set of equations that can be used to predict the dynamical diffraction profile from a non-transparent single crystal with a constant <span class="hlt">strain</span> gradient examined in Bragg reflection geometry with a spherical incident X-ray beam. In agreement with previous work, the present analysis predicts two peaks: a primary diffraction peak, which would have still been observed in the absence of the <span class="hlt">strain</span> gradient and which exits the specimen surface at the intersection point of the incident beam with the sample surface, and a secondary (mirage) peak, caused by the deflection of the wavefield within the material, which exits the specimen surface further from this intersection point. The integrated intensity of the mirage peak increases with increasing <span class="hlt">strain</span> gradient, while its separation from the primary reflection peak decreases. The directions of the rays forming the mirage peak are parallel to those forming the primary diffraction peak. However, their spatial displacement might cause (fictitious) angular shifts in diffractometers equipped with area detectors or slit optics. The analysis results are compared with experimental data from an Si single-crystal strip bent in cantilever configuration, and the implications of the mirage peak for Laue analysis and high-precision diffraction measurements are discussed.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1982MTA....13..595A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1982MTA....13..595A"><span id="translatedtitle"><span class="hlt">Finite</span> Element Method (FEM) Calculations of Stress-<span class="hlt">Strain</span> Behavior of Alpha-Beta Ti-Mn Alloys: Part I. Stress-<span class="hlt">Strain</span> Relations</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ankem, Sreeramamurthy; Margolin, Harold</p> <p>1982-04-01</p> <p>By use of a NASTRAN18 Computer Program, the <span class="hlt">Finite</span> Element Method (FEM) has been employed to calculate the effect of particle size, matrix, and volume fraction on the stress-<span class="hlt">strain</span> relations of α -β titanium alloys. It was found that for a given volume fraction, the calculated stress-<span class="hlt">strain</span> curve was higher for a finer particle size than for a coarse particle size within the range of the <span class="hlt">strains</span> considered, and this behavior was seen for all the different volume fraction alloys considered. For a 50:50 vol pct α -β alloy, the stress-<span class="hlt">strain</span> curve with β, the stronger phase, as the matrix was higher than that with α, the softer phase, as the matrix. The calculated stress-<span class="hlt">strain</span> curves for four different vol pct α alloys were compared with their corresponding experimental curves, and in general, good agreement was found. Whenever there were discrepancies, they were discussed by comparing the morphology of the mesh used in the calculations with the morphology of the actual materials.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015CG.....78..123B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015CG.....78..123B"><span id="translatedtitle"><span class="hlt">Strain</span>Modeler: A MATHEMATICA™-based program for 3D analysis of <span class="hlt">finite</span> and progressive <span class="hlt">strain</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Bobillo-Ares, Nilo C.; Aller, Jesús; Bastida, Fernando; Menéndez, Omar; Lisle, Richard J.</p> <p>2015-05-01</p> <p><span class="hlt">Strain</span>Modeler is a program constructed in the MATHEMATICA™ environment that performs 3D progressive <span class="hlt">strain</span> calculations for lines and planes undergoing any sequence of homogeneous deformations. The main inputs to the system define the initial line or plane to be deformed and the deformation sequence to be applied, including combinations of simple shear, pure shear and volume change. For the deformation of lines, the output of the program is the change of attitude of the initial line, which can be represented by graphics or plotted in an equal-area projection. For the deformation of planes, the program has several outputs: (i) change of attitude of the initial plane; (ii) magnitudes and ratio of the semi-axes of the <span class="hlt">strain</span> ellipse on the deformed plane; (iii) orientation of the major and minor axes of the <span class="hlt">strain</span> ellipse on the deformed plane; (iv) orientations of the axial planes of the folds formed on the deformed plane, and (v) area change on the deformed plane. The variation of any of these parameters can be shown against a linear parameter only linked to the number of steps involved in the deformation, as a kind of "time" line, or it can be shown against the variation of a parameter of the <span class="hlt">strain</span> ellipsoid (e. g.: major axis/minor axis ratio). A sequence of directions can be also visualized as a curve in an equal-area plot. Three applications of the program are presented. In the first, the deformation by simple shear of a plane with any orientation is analyzed. In the second, we explore the formation of recumbent folds in layers with different initial orientations for simple shear and pure shear deformations. In the third, we use <span class="hlt">Strain</span>Modeler to analyze the deformation of a set of folds located in a ductile shear zone in the Variscan Belt of NW Spain.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/963866','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/963866"><span id="translatedtitle">Impact of dislocation cell <span class="hlt">elastic</span> <span class="hlt">strain</span> variations on line profiles from deformed copper.</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Levine, L. E.; Larson, B. C.; Tischler, J. Z.; Geantil, P.; Kassner, M. E.; Liu, W.; Stoudt, M. R.; NIST; ORNL; Univ. of Southern California</p> <p>2008-01-01</p> <p>Energy scanned, sub-micrometer X-ray beams were used to obtain diffraction line profiles from individual dislocation cells in copper single crystals deformed in compression. Sub-micrometer depth resolution was provided by translating a wire through the diffracted beams and using triangulation to determine the depths of the diffracting volumes. Connection to classic volume-averaged results was made by adding the line profiles from 52 spatially resolved dislocation cell measurements. The resulting sub profile is smooth and symmetric, in agreement with early assumptions; the mean <span class="hlt">strain</span> and full width half maximum are consistent with the average of the parameters extracted from the more exact individual dislocation cell measurements.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/989816','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/989816"><span id="translatedtitle">The young's modulus of 1018 steel and 67061-T6 aluminum measured from quasi-static to <span class="hlt">elastic</span> precursor <span class="hlt">strain</span>-rates</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Rae, Philip J; Trujillo, Carl; Lovato, Manuel</p> <p>2009-01-01</p> <p>The assumption that Young's modulus is <span class="hlt">strain</span>-rate invariant is tested for 6061-T6 aluminium alloy and 1018 steel over 10 decades of <span class="hlt">strain</span>-rate. For the same billets of material, 3 quasi-static <span class="hlt">strain</span>-rates are investigated with foil <span class="hlt">strain</span> gauges at room temperature. The ultrasonic sound speeds are measured and used to calculate the moduli at approximately 10{sup 4} s{sup -1}. Finally, ID plate impact is used to generate an <span class="hlt">elastic</span> pre-cursor in the alloys at a <span class="hlt">strain</span>-rate of approximately 10{sup 6} s{sup -1} from which the longitudinal sound speed may be obtained. It is found that indeed the Young's modulus is <span class="hlt">strain</span>-rate independent within the experimental accuracy.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013APLM....1b2106M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013APLM....1b2106M"><span id="translatedtitle">Microlattices as architected thin films: Analysis of mechanical properties and high <span class="hlt">strain</span> <span class="hlt">elastic</span> recovery</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Maloney, Kevin J.; Roper, Christopher S.; Jacobsen, Alan J.; Carter, William B.; Valdevit, Lorenzo; Schaedler, Tobias A.</p> <p>2013-08-01</p> <p>Ordered periodic microlattices with densities from 0.5 mg/cm3 to 500 mg/cm3 are fabricated by depositing various thin film materials (Au, Cu, Ni, SiO2, poly(C8H4F4)) onto sacrificial polymer lattice templates. Young's modulus and strength are measured in compression and the density scaling is determined. At low relative densities, recovery from compressive <span class="hlt">strains</span> of 50% and higher is observed, independent of lattice material. An analytical model is shown to accurately predict the transition between recoverable "pseudo-superelastic" and irrecoverable plastic deformation for all constituent materials. These materials are of interest for energy storage applications, deployable structures, and for acoustic, shock, and vibration damping.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/815195','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/815195"><span id="translatedtitle">Material Properties Test to Determine Ultimate <span class="hlt">Strain</span> and True Stress-True <span class="hlt">Strain</span> Curves for High Yield Steels</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>K.R. Arpin; T.F. Trimble</p> <p>2003-04-01</p> <p>This testing was undertaken to develop material true stress-true <span class="hlt">strain</span> curves for <span class="hlt">elastic</span>-plastic material behavior for use in performing transient analysis. Based on the conclusions of this test, the true stress-true <span class="hlt">strain</span> curves derived herein are valid for use in <span class="hlt">elastic</span>-plastic <span class="hlt">finite</span> element analysis for structures fabricated from these materials. In addition, for the materials tested herein, the ultimate <span class="hlt">strain</span> values are greater than those values cited as the limits for the <span class="hlt">elastic</span>-plastic <span class="hlt">strain</span> acceptance criteria for transient analysis.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2002SPIE.4934..128B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2002SPIE.4934..128B"><span id="translatedtitle"><span class="hlt">Finite</span> element modeling to determine thermal residual <span class="hlt">strain</span> distribution of bonded composite repairs for structural health monitoring design</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Baker, Wayne; Jones, Rhys; Davis, Claire; Galea, Stephen C.</p> <p>2002-11-01</p> <p>The economic implication of fleet upgrades, particularly in Australia with military aircraft such as the F-111 and F/A-18, has led to an increasing reliance on composite repair technology to address fatigue and corrosion-affected aircraft components. The increasing use of such repairs has led to a research effort to develop various in-situ health monitoring systems that may be incorporated with a repair. This paper reports on the development of a theoretical methodology that uses <span class="hlt">finite</span> element analysis (FEA) to model the <span class="hlt">strain</span> profiles which optical sensors, on or within the patch, will be exposed to under various operational scenarios, including load and disbond. Numerical techniques are then used to predict the fibre Bragg grating (FBG) reflections which occur with these <span class="hlt">strain</span> profiles. The quality of these reflection are a key consideration when designing FBG based structural health monitoring (SHM) systems. This information can be used to optimise the location of both surface mounted, and embedded sensors, and determine feasibility of SHM system design. Research was conducted into the thermal residual <span class="hlt">strain</span> (TRS) within the patch. A <span class="hlt">finite</span> element study revealed the presence of significant thermal residual <span class="hlt">strain</span> gradients along the surface of the tapered region of the patch. As Bragg gratings are particularly sensitive to <span class="hlt">strain</span> gradients, (producing a result similar to a chirped grating) the <span class="hlt">strain</span> gradient on the composite at potential sensor locations both under load, and in the event of disbond was considered. A sufficiently high gradient leads to an altered Bragg reflection. These spurious reflections need to be considered, and theoretically obtained reflections can provide information to allow for load scenarios where the Bragg shift is not a smooth, well defined peak. It can also be shown that embedded fibres offer a higher average thermal residual <span class="hlt">strain</span> reading, while being subject to a much lower <span class="hlt">strain</span> gradient. This particularly favors the</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=341061','PMC'); return false;" href="http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=341061"><span id="translatedtitle">DNAaseI-hypersensitive minichromosomes of SV40 possess an <span class="hlt">elastic</span> torsional <span class="hlt">strain</span> in DNA.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Luchnik, A N; Bakayev, V V; Yugai, A A; Zbarsky, I B; Georgiev, G P</p> <p>1985-01-01</p> <p>Previously, we have shown that DNA in a small fraction (2-5%) of SV40 minichromosomes was torsionally <span class="hlt">strained</span> and could be relaxed by treating minichromosomes with topoisomerase I. This fraction was enriched with endogeneous RNA polymerase II (Luchnik et al., 1982, EMBO J., 1, 1353). Here we show that one and the same fraction of SV40 minichromosomes is hypersensitive to DNAase I and is relaxable by topoisomerase I. Moreover, this fraction completely loses its hypersensitivity to DNAase I upon relaxation. The possibility that this fraction of minichromosomes can be represented by naked DNA is ruled out by the results of studying the kinetics of minichromosome digestion by DNAase I in comparison to digestion of pure SV40 DNA and by measuring the buoyant density of SV40 chromatin in equilibrium CsCl gradient. Our data obtained with SV40 minichromosomes may be relevant to the mechanism responsible for DNAase I hypersensitivity in the loops or domains of cellular chromatin. Images PMID:2987817</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2000CompM..25...66G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2000CompM..25...66G"><span id="translatedtitle">Nonlinear material parameter estimation for characterizing hyper <span class="hlt">elastic</span> large <span class="hlt">strain</span> models</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Gendy, A. S.; Saleeb, A. F.</p> <p></p> <p>An automated, systematic, and computationally efficient methodology to estimate the material parameters for characterizing general nonlinear material models for large <span class="hlt">strain</span> analysis (e.g., hyperelastic and hyper foam materials) is presented. Such constitutive material models often require a large number of material constants to describe a host of physical phenomena and complicated deformation mechanisms. Extracting such material constants for a model from the volumes of data generated in the test laboratory is usually a very difficult, and frustrating. The integrated code COMPARE (that is an acronym of Constitutive Material PARameter Estimator) is being developed to enable the determination of an ``optimum'' set material parameters by minimizing the errors between the experimental test data and the predicted response. The key ingredients of COMPARE are listed as follows: (i) primal analysis tools (response functionals) for differential form of constitutive models; (ii) sensitivity analysis; (iii) optimization technique of an error/cost function; and (iv) graphical user interface. The code COMPARE casts the estimation of the material parameters as a minimum-error, weighted-multiobjective, optimization problem. Detailed derivations and results generated by applying the proposed technique to a comprehensive set of test data are given. These results have clearly demonstrated the great practical utility of the automated scheme developed.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2016PhRvE..94b3107X&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2016PhRvE..94b3107X&link_type=ABSTRACT"><span id="translatedtitle"><span class="hlt">Finite</span>-wavelength surface-tension-driven instabilities in soft solids, including instability in a cylindrical channel through an <span class="hlt">elastic</span> solid</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Xuan, Chen; Biggins, John</p> <p>2016-08-01</p> <p>We deploy linear stability analysis to find the threshold wavelength (λ ) and surface tension (γ ) of Rayleigh-Plateau type "peristaltic" instabilities in incompressible neo-Hookean solids in a range of cylindrical geometries with radius R0. First we consider a solid cylinder, and recover the well-known, infinite-wavelength instability for γ ≥6 μ R0 , where μ is the solid's shear modulus. Second, we consider a volume-conserving (e.g., fluid filled and sealed) cylindrical cavity through an infinite solid, and demonstrate infinite-wavelength instability for γ ≥2 μ R0 . Third, we consider a solid cylinder embedded in a different infinite solid, and find a <span class="hlt">finite</span>-wavelength instability with λ ∝R0 , at surface tension γ ∝μ R0 , where the constants depend on the two solids' modulus ratio. Finally, we consider an empty cylindrical channel (or filled with expellable fluid) through an infinite solid, and find an instability with <span class="hlt">finite</span> wavelength, λ ≈2 R0 , for γ ≥2.543 ...μ R0 . Using <span class="hlt">finite-strain</span> numerics, we show such a channel jumps at instability to a highly peristaltic state, likely precipitating it's blockage or failure. We argue that <span class="hlt">finite</span> wavelengths are generic for elastocapillary instabilities, with the simple cylinder's infinite wavelength being the exception rather than the rule.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/27007776','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/27007776"><span id="translatedtitle">Quantitative comparison of ligament formulation and pre-<span class="hlt">strain</span> in <span class="hlt">finite</span> element analysis of the human lumbar spine.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Hortin, Mitchell S; Bowden, Anton E</p> <p>2016-11-01</p> <p>Data has been published that quantifies the nonlinear, anisotropic material behaviour and pre-<span class="hlt">strain</span> behaviour of the anterior longitudinal, supraspinous (SSL), and interspinous ligaments of the human lumbar spine. Additionally, data has been published on localized material properties of the SSL. These results have been incrementally incorporated into a previously validated <span class="hlt">finite</span> element model of the human lumbar spine. Results suggest that the effects of increased ligament model fidelity on bone <span class="hlt">strain</span> energy were moderate and the effects on disc pressure were slight, and do not justify a change in modelling strategy for most clinical applications. There were significant effects on the ligament stresses of the ligaments that were directly modified, suggesting that these phenomena should be included in FE models where ligament stresses are the desired metric. PMID:27007776</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/11201407','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/11201407"><span id="translatedtitle"><span class="hlt">Finite</span> element analysis of bone stress and <span class="hlt">strain</span> around a distal osseointegrated implant for prosthetic limb attachment.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Xu, W; Crocombe, A D; Hughes, S C</p> <p>2000-01-01</p> <p>Direct skeletal attachment techniques have recently been identified as an alternative method for percutaneous attachment of prosthetic limbs. Osseointegrated implants for prosthetic attachments are subjected to a complex load condition. This <span class="hlt">finite</span> element study investigates the effect of varying geometries of the implant on the stress and <span class="hlt">strain</span> distribution in the area of the bone/implant interface. Simplified three-dimensional axisymmetric models of the femur and seven implants with different core diameters, external diameters, implant lengths and thread pitches were derived. The resulting stress and <span class="hlt">strain</span> distributions were compared. The significance of each implant geometry was identified for improving implant design in the light of benefit to the bone/implant osseointegration and the bone remodelling of the femur. PMID:11201407</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4601018','PMC'); return false;" href="http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4601018"><span id="translatedtitle"><span class="hlt">Finite</span> element modelling predicts changes in joint shape and cell behaviour due to loss of muscle <span class="hlt">strain</span> in jaw development</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Brunt, Lucy H.; Norton, Joanna L.; Bright, Jen A.; Rayfield, Emily J.; Hammond, Chrissy L.</p> <p>2015-01-01</p> <p>Abnormal joint morphogenesis is linked to clinical conditions such as Developmental Dysplasia of the Hip (DDH) and to osteoarthritis (OA). Muscle activity is known to be important during the developmental process of joint morphogenesis. However, less is known about how this mechanical stimulus affects the behaviour of joint cells to generate altered morphology. Using zebrafish, in which we can image all joint musculoskeletal tissues at high resolution, we show that removal of muscle activity through anaesthetisation or genetic manipulation causes a change to the shape of the joint between the Meckel's cartilage and Palatoquadrate (the jaw joint), such that the joint develops asymmetrically leading to an overlap of the cartilage elements on the medial side which inhibits normal joint function. We identify the time during which muscle activity is critical to produce a normal joint. Using <span class="hlt">Finite</span> Element Analysis (FEA), to model the <span class="hlt">strains</span> exerted by muscle on the skeletal elements, we identify that minimum principal <span class="hlt">strains</span> are located at the medial region of the joint and interzone during mouth opening. Then, by studying the cells immediately proximal to the joint, we demonstrate that biomechanical <span class="hlt">strain</span> regulates cell orientation within the developing joint, such that when muscle-induced <span class="hlt">strain</span> is removed, cells on the medial side of the joint notably change their orientation. Together, these data show that biomechanical forces are required to establish symmetry in the joint during development. PMID:26253758</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3774949','PMC'); return false;" href="http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3774949"><span id="translatedtitle">Stress-<span class="hlt">strain</span> distribution at bone-implant interface of two splinted overdenture systems using 3D <span class="hlt">finite</span> element analysis</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p></p> <p>2013-01-01</p> <p>PURPOSE This study was accomplished to assess the biomechanical state of different retaining methods of bar implant-overdenture. MATERIALS AND METHODS Two 3D <span class="hlt">finite</span> element models were designed. The first model included implant overdenture retained by Hader-clip attachment, while the second model included two extracoronal resilient attachment (ERA) studs added distally to Hader splint bar. A non-linear frictional contact type was assumed between overdentures and mucosa to represent sliding and rotational movements among different attachment components. A 200 N was applied at the molar region unilaterally and perpendicular to the occlusal plane. Additionally, the mandible was restrained at their ramus ends. The maximum equivalent stress and <span class="hlt">strain</span> (von Mises) were recorded and analyzed at the bone-implant interface level. RESULTS The values of von Mises stress and <span class="hlt">strain</span> of the first model at bone-implant interface were higher than their counterparts of the second model. Stress concentration and high value of <span class="hlt">strain</span> were recognized surrounding implant of the unloaded side in both models. CONCLUSION There were different patterns of stress-<span class="hlt">strain</span> distribution at bone-implant interface between the studied attachment designs. Hader bar-clip attachment showed better biomechanical behavior than adding ERA studs distal to hader bar. PMID:24049576</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/20846282','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/20846282"><span id="translatedtitle"><span class="hlt">Strain</span> in the ostrich mandible during simulated pecking and validation of specimen-specific <span class="hlt">finite</span> element models.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Rayfield, Emily J</p> <p>2011-01-01</p> <p><span class="hlt">Finite</span> element (FE) analysis is becoming a frequently used tool for exploring the craniofacial biomechanics of extant and extinct vertebrates. Crucial to the application of the FE analysis is the knowledge of how well FE results replicate reality. Here I present a study investigating how accurately FE models can predict experimentally derived <span class="hlt">strain</span> in the mandible of the ostrich Struthio camelus, when both the model and the jaw are subject to identical conditions in an in-vitro loading environment. Three isolated ostrich mandibles were loaded hydraulically at the beak tip with forces similar to those measured during force transducer pecking experiments. <span class="hlt">Strains</span> were recorded at four gauge sites at the dorsal and ventral dentary, and medial and lateral surangular. Specimen-specific FE models were created from computed tomography scans of each ostrich and loaded in an identical fashion as in the in-vitro test. The results show that the <span class="hlt">strain</span> magnitudes, orientation, patterns and maximum : minimum principal <span class="hlt">strain</span> ratios are predicted very closely at the dentary gauge sites, even though the FE models have isotropic and homogeneous material properties and solid internal geometry. Although the <span class="hlt">strain</span> magnitudes are predicted at the postdentary sites, the <span class="hlt">strain</span> orientations and ratios are inaccurate. This mismatch between the dentary and postdentary predictions may be due to the presence of intramandibular sutures or the greater amount of cancellous bone present in the postdentary region of the mandible and requires further study. This study highlights the predictive potential of even simple FE models for studies in extant and extinct vertebrates, but also emphasizes the importance of geometry and sutures. It raises the question of whether different parameters are of lesser or greater importance to FE validation for different taxonomic groups. PMID:20846282</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3039780','PMC'); return false;" href="http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3039780"><span id="translatedtitle"><span class="hlt">Strain</span> in the ostrich mandible during simulated pecking and validation of specimen-specific <span class="hlt">finite</span> element models</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Rayfield, Emily J</p> <p>2011-01-01</p> <p><span class="hlt">Finite</span> element (FE) analysis is becoming a frequently used tool for exploring the craniofacial biomechanics of extant and extinct vertebrates. Crucial to the application of the FE analysis is the knowledge of how well FE results replicate reality. Here I present a study investigating how accurately FE models can predict experimentally derived <span class="hlt">strain</span> in the mandible of the ostrich Struthio camelus, when both the model and the jaw are subject to identical conditions in an in-vitro loading environment. Three isolated ostrich mandibles were loaded hydraulically at the beak tip with forces similar to those measured during force transducer pecking experiments. <span class="hlt">Strains</span> were recorded at four gauge sites at the dorsal and ventral dentary, and medial and lateral surangular. Specimen-specific FE models were created from computed tomography scans of each ostrich and loaded in an identical fashion as in the in-vitro test. The results show that the <span class="hlt">strain</span> magnitudes, orientation, patterns and maximum : minimum principal <span class="hlt">strain</span> ratios are predicted very closely at the dentary gauge sites, even though the FE models have isotropic and homogeneous material properties and solid internal geometry. Although the <span class="hlt">strain</span> magnitudes are predicted at the postdentary sites, the <span class="hlt">strain</span> orientations and ratios are inaccurate. This mismatch between the dentary and postdentary predictions may be due to the presence of intramandibular sutures or the greater amount of cancellous bone present in the postdentary region of the mandible and requires further study. This study highlights the predictive potential of even simple FE models for studies in extant and extinct vertebrates, but also emphasizes the importance of geometry and sutures. It raises the question of whether different parameters are of lesser or greater importance to FE validation for different taxonomic groups. PMID:20846282</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2016GeoJI.206..114I&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2016GeoJI.206..114I&link_type=ABSTRACT"><span id="translatedtitle">An <span class="hlt">elastic</span>/viscoelastic <span class="hlt">finite</span> element analysis method for crustal deformation using a 3-D island-scale high-fidelity model</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ichimura, Tsuyoshi; Agata, Ryoichiro; Hori, Takane; Hirahara, Kazuro; Hashimoto, Chihiro; Hori, Muneo; Fukahata, Yukitoshi</p> <p>2016-07-01</p> <p>As a result of the accumulation of high-resolution observation data, 3-D high-fidelity crustal structure data for large domains are becoming available. However, it has been difficult to use such data to perform <span class="hlt">elastic</span>/viscoelastic crustal deformation analyses in large domains with quality assurance of the numerical simulation that guarantees convergence of the numerical solution with respect to the discretization size because the costs of analysis are significantly high. This paper proposes a method of constructing a high-fidelity crustal structure <span class="hlt">finite</span> element (FE) model using high-fidelity crustal structure data and fast FE analysis to reduce the costs of analysis (based on automatic FE model generation for parallel computation, OpenMP/MPI hybrid parallel computation on distributed memory computers, a geometric multigrid, variable preconditioning and multiple precision arithmetic). Using the proposed methods, we construct 10 billion degree-of-freedom high-fidelity crustal structure FE models for the entire Japan, and conduct <span class="hlt">elastic</span>/viscoelastic crustal deformation analysis using this model with enough high accuracy of the numerical simulation.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li class="active"><span>18</span></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_18 --> <div id="page_19" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li class="active"><span>19</span></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="361"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015SMaS...24b5026S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015SMaS...24b5026S"><span id="translatedtitle"><span class="hlt">Finite</span> element analysis of the macro fiber composite actuator: macroscopic <span class="hlt">elastic</span> and piezoelectric properties and active control thereof by means of negative capacitance shunt circuit</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Steiger, Kateřina; Mokrý, Pavel</p> <p>2015-02-01</p> <p>The <span class="hlt">finite</span> element method (FEM) model of a piezoelectric macro fiber composite (MFC) is presented. Using a specially developed numerical model, the complete set of macroscopic values of <span class="hlt">elastic</span> compliance and piezoelectric tensors is computed. These values are useful in numerical FEM simulations of more complex systems such as noise and vibration suppression devices or active acoustic metamaterials, where the MFC actuator can be approximated by a plate-like uniform piezoelectric material. Using this approach, a great reduction of the FEM model complexity can be achieved. The computed numerical macroscopic values of the MFC actuator are compared with MFC manufacturer's data and with data obtained using different computational methods. A demonstration of active tuning of effective <span class="hlt">elastic</span> constants of the piezoelectric MFC actuator by means of a shunt electric circuit is presented. The effective material constants are computed using the FEM model developed. The effect of the shunt circuit capacitance on the effective anisotropic Young's moduli is analyzed in detail. A method for finding the proper shunt circuit adjustment that yields the maximum values of the MFC actuator Young's modulus is shown. Possible applications to noise and vibration suppression are discussed.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016GeoJI.tmp...84I','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016GeoJI.tmp...84I"><span id="translatedtitle">An <span class="hlt">Elastic</span>/Viscoelastic <span class="hlt">Finite</span> Element Analysis Method for Crustal Deformation using a 3D Island-scale High-fidelity Model</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ichimura, Tsuyoshi; Agata, Ryoichiro; Hori, Takane; Hirahara, Kazuro; Hashimoto, Chihiro; Hori, Muneo; Fukahata, Yukitoshi</p> <p>2016-04-01</p> <p>As a result of the accumulation of high-resolution observation data, three-dimensional high-fidelity crustal structure data for large domains are becoming available. However, it has been difficult to use such data to perform <span class="hlt">elastic</span>/viscoelastic crustal deformation analyses in large domains with quality assurance of the numerical simulation that guarantees convergence of the numerical solution with respect to the discretisation size, because the costs of analysis are significantly high. This paper proposes a method of constructing a high-fidelity crustal structure <span class="hlt">finite</span> element (FE) model using high-fidelity crustal structure data and fast FE analysis to reduce the costs of analysis (based on automatic FE model generation for parallel computation, OpenMP/MPI hybrid parallel computation on distributed memory computers, a geometric multigrid, variable preconditioning, and multiple precision arithmetic). Using the proposed methods, we construct 10 billion degree-of-freedom high-fidelity crustal structure FE models for the entire Japan, and conduct <span class="hlt">elastic</span>/viscoelastic crustal deformation analysis using this model with enough high accuracy of the numerical simulation.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2007AIPC..908..847P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2007AIPC..908..847P"><span id="translatedtitle">Study on the Influence of the Refinement of a 3-D <span class="hlt">Finite</span> Element Mesh in Springback Evaluation of Plane-<span class="hlt">Strain</span> Channel Sections</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Padmanabhan, R.; Oliveira, M. C.; Baptista, A. J.; Alves, J. L.; Menezes, L. F.</p> <p>2007-05-01</p> <p>Springback phenomenon associated with the <span class="hlt">elastic</span> properties of sheet metals makes the design of forming dies a complex task. Thus, to develop consistent algorithms for springback compensation an accurate prediction of the amount of springback is mandatory. The numerical simulation using the <span class="hlt">finite</span> element method is consensually the only feasible method to predict springback. However, springback prediction is a very complicated task and highly sensitive to various numerical parameters of <span class="hlt">finite</span> elements (FE), such as: type, order, integration scheme, shape and size, as well the time integration formulae and the unloading strategy. All these numerical parameters make numerical simulation of springback more sensitive to numerical tolerances than the forming operation. In case of an unconstrained cylindrical bending, the in-plane to thickness FE size ratio is more relevant than the number of FE layers through-thickness, for the numerical prediction of final stress and <span class="hlt">strain</span> states, variables of paramount importance for an accurate springback prediction. The aim of the present work is to evaluate the influence of the refinement of a 3-D FE mesh, namely the in-plane mesh refinement and the number of through-thickness FE layers, in springback prediction. The selected example corresponds to the first stage of the "Numisheet'05 Benchmark♯3", which consists basically in the sheet forming of a channel section in an industrial-scale channel draw die. The physical drawbeads are accurately taken into account in the numerical model in order to accurately reproduce its influence during the forming process simulation. FEM simulations were carried out with the in-house code DD3IMP. Solid <span class="hlt">finite</span> elements were used. They are recommended for accuracy in FE springback simulation when the ratio between the tool radius and blank thickness is lower than 5-6. In the selected example the drawbead radius is 4.0 mm. The influence of the FE mesh refinement in springback prediction is</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AcMSn.tmp...23O','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AcMSn.tmp...23O"><span id="translatedtitle">Analytical and <span class="hlt">finite</span>-element study of optimal <span class="hlt">strain</span> distribution in various beam shapes for energy harvesting applications</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ooi, B. L.; Gilbert, J. M.; Aziz, A. Rashid A.</p> <p>2016-05-01</p> <p>Owing to the increasing demand for harvesting energy from environmental vibration for use in self-powered electronic applications, cantilever-based vibration energy harvesting has attracted considerable interest from various parties and has become one of the most common approaches to converting redundant mechanical energy into electrical energy. As the output voltage produced from a piezoelectric material depends largely on the geometric shape and the size of the beam, there is a need to model and compare the performance of cantilever beams of differing geometries. This paper presents the study of <span class="hlt">strain</span> distribution in various shapes of cantilever beams, including a convex and concave edge profile elliptical beam that have not yet been discussed in any prior literature. Both analytical and <span class="hlt">finite</span>-element models are derived and the resultant <span class="hlt">strain</span> distributions in the beam are computed based on a MATLAB solver and ANSYS <span class="hlt">finite</span>-element analysis tools. An optimum geometry for a vibration-based energy harvesting system is verified. Finally, experimental results comparing the power density for triangular and rectangular piezoelectric beams are also presented to validate the findings of the study, and the claim, as suggested in the literature, is verified.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2016AcMSn..32..670O&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2016AcMSn..32..670O&link_type=ABSTRACT"><span id="translatedtitle">Analytical and <span class="hlt">finite</span>-element study of optimal <span class="hlt">strain</span> distribution in various beam shapes for energy harvesting applications</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ooi, B. L.; Gilbert, J. M.; Aziz, A. Rashid A.</p> <p>2016-08-01</p> <p>Owing to the increasing demand for harvesting energy from environmental vibration for use in self-powered electronic applications, cantilever-based vibration energy harvesting has attracted considerable interest from various parties and has become one of the most common approaches to converting redundant mechanical energy into electrical energy. As the output voltage produced from a piezoelectric material depends largely on the geometric shape and the size of the beam, there is a need to model and compare the performance of cantilever beams of differing geometries. This paper presents the study of <span class="hlt">strain</span> distribution in various shapes of cantilever beams, including a convex and concave edge profile elliptical beam that have not yet been discussed in any prior literature. Both analytical and <span class="hlt">finite</span>-element models are derived and the resultant <span class="hlt">strain</span> distributions in the beam are computed based on a MATLAB solver and ANSYS <span class="hlt">finite</span>-element analysis tools. An optimum geometry for a vibration-based energy harvesting system is verified. Finally, experimental results comparing the power density for triangular and rectangular piezoelectric beams are also presented to validate the findings of the study, and the claim, as suggested in the literature, is verified.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016GeoJI.tmp...39H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016GeoJI.tmp...39H"><span id="translatedtitle">An error analysis of higher-order <span class="hlt">finite</span> element methods: Effect of degenerate coupling on simulation of <span class="hlt">elastic</span> wave propagation</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Hasegawa, Kei; Geller, Robert J.; Hirabayashi, Nobuyasu</p> <p>2016-02-01</p> <p>We present a theoretical analysis of the error of synthetic seismograms computed by higher-order <span class="hlt">finite</span> element methods (ho-FEMs). We show the existence of a previously unrecognized type of error due to degenerate coupling between waves with the same frequency but different wavenumbers. These results are confirmed by simple numerical experiments using the spectral element method (SEM) as an example of ho-FEMs. Errors of the type found by this study may occur generally in applications of ho-FEMs.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3141343','PMC'); return false;" href="http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3141343"><span id="translatedtitle">Large Diameter Femoral Heads Impose Significant Alterations on the <span class="hlt">Strains</span> Developed on Femoral Component and Bone: A <span class="hlt">Finite</span> Element Analysis</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Theodorou, E.G; Provatidis, C.G; Babis, G.C; Georgiou, C.S; Megas, P.D</p> <p>2011-01-01</p> <p>Total Hip Arthroplasty aims at fully recreating a functional hip joint. Over the past years modular implant systems have become common practice and are widely used, due to the surgical options they provide. In addition Big Femoral Heads have also been implemented in the process, providing more flexibility for the surgeon. The current study aims at investigating the effects that femoral heads of bigger diameter may impose on the mechanical behavior of the bone-implant assembly. Using data acquired by Computed Tomographies and a Coordinate Measurement Machine, a cadaveric femur and a Profemur-E modular stem were fully digitized, leading to a three dimensional <span class="hlt">finite</span> element model in ANSYS Workbench. <span class="hlt">Strains</span> and stresses were then calculated, focusing on areas of clinical interest, based on Gruen zones: the calcar and the corresponding below the greater trochanter area in the proximal femur, the stem tip region and a profile line along linea aspera. The performed <span class="hlt">finite</span> elements analysis revealed that the use of large diameter heads produces significant changes in <span class="hlt">strain</span> development within the bone volume, especially in the lateral side. The application of Frost’s law in bone remodeling, validated the hypothesis that for all diameters normal bone growth occurs. However, in the calcar area lower <span class="hlt">strain</span> values were recorded, when comparing with the reference model featuring a 28mm femoral head. Along line aspera and for the stem tip area, higher values were recorded. Finally, stresses calculated on the modular neck revealed increased values, but without reaching the yield strength of the titanium alloy used. PMID:21792381</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2015EPJWC..9404022S&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2015EPJWC..9404022S&link_type=ABSTRACT"><span id="translatedtitle"><span class="hlt">Strain</span>-rate sensitivity of foam materials: A numerical study using 3D image-based <span class="hlt">finite</span> element model</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Sun, Yongle; Li, Q. M.; Withers, P. J.</p> <p>2015-09-01</p> <p>Realistic simulations are increasingly demanded to clarify the dynamic behaviour of foam materials, because, on one hand, the significant variability (e.g. 20% scatter band) of foam properties and the lack of reliable dynamic test methods for foams bring particular difficulty to accurately evaluate the <span class="hlt">strain</span>-rate sensitivity in experiments; while on the other hand numerical models based on idealised cell structures (e.g. Kelvin and Voronoi) may not be sufficiently representative to capture the actual structural effect. To overcome these limitations, the <span class="hlt">strain</span>-rate sensitivity of the compressive and tensile properties of closed-cell aluminium Alporas foam is investigated in this study by means of meso-scale realistic <span class="hlt">finite</span> element (FE) simulations. The FE modelling method based on X-ray computed tomography (CT) image is introduced first, as well as its applications to foam materials. Then the compression and tension of Alporas foam at a wide variety of applied nominal <span class="hlt">strain</span>-rates are simulated using FE model constructed from the actual cell geometry obtained from the CT image. The stain-rate sensitivity of compressive strength (collapse stress) and tensile strength (0.2% offset yield point) are evaluated when considering different cell-wall material properties. The numerical results show that the rate dependence of cell-wall material is the main cause of the <span class="hlt">strain</span>-rate hardening of the compressive and tensile strengths at low and intermediate <span class="hlt">strain</span>-rates. When the <span class="hlt">strain</span>-rate is sufficiently high, shock compression is initiated, which significantly enhances the stress at the loading end and has complicated effect on the stress at the supporting end. The plastic tensile wave effect is evident at high <span class="hlt">strain</span>-rates, but shock tension cannot develop in Alporas foam due to the softening associated with single fracture process zone occurring in tensile response. In all cases the micro inertia of individual cell walls subjected to localised deformation is found to</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014Geote..48..483K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014Geote..48..483K"><span id="translatedtitle"><span class="hlt">Finite</span> <span class="hlt">strain</span> analysis of metavolcanics and metapyroclastics in gold-bearing shear zone of the Dungash area, Central Eastern Desert, Egypt</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kassem, Osama M. K.; Abd El Rahim, Said H.</p> <p>2014-11-01</p> <p>The Dungash gold mine area is situated in an EW-trending quartz vein along a shear zone in metavolcanic and metasedimentary host rocks in the Eastern Desert of Egypt. These rocks are associated with the major geologic structures, which are attributed to various deformational stages of the Neoproterozoic basement rocks. Field geology, <span class="hlt">finite</span> <span class="hlt">strain</span> and microstructural analyses were carried out and the relation-ships between the lithological contacts and major/minor structures have been studied. The R f/ϕ and Fry methods were applied on the metavolcano-sedimentary and metapyroclastic samples from 5 quartz veins samples, 7 metavolcanics samples, 3 metasedimentary samples and 4 metapyroclastic samples in Dungash area. <span class="hlt">Finite-strain</span> data show that a low to moderate range of deformation of the metavolcano-sedimentary samples and axial ratios in the XZ section range from 1.70 to 4.80 for the R f/ϕ method and from 1.65 to 4.50 for the Fry method. We conclude that <span class="hlt">finite</span> <span class="hlt">strain</span> in the deformed rocks is of the same order of magnitude for all units of metavolcano-sedimentary rocks. Furthermore, the contact between principal rock units is sheared in the Dungash area under brittle to semi-ductile deformation conditions. In this case, the accumulated <span class="hlt">finite</span> <span class="hlt">strain</span> is associated with the deformation during thrusting to assemble nappe structure. It indicates that the sheared contacts have been formed during the accumulation of <span class="hlt">finite</span> <span class="hlt">strain</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/1072213','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/1072213"><span id="translatedtitle">RELEASE OF <span class="hlt">ELASTIC</span> <span class="hlt">STRAIN</span> ENERGY AS ACOUSTIC EMISSION DURING THE REVERSE THERMOELASTIC PHASE TRANSFORMATION IN Au-47.5 at.percent Cd ALLOY</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Baram, J.; Avissar, J.; Gefen, Y.; Rosen, M.</p> <p>1980-05-01</p> <p>The objective of this paper is to present experimental evidence concerning the acoustic energy evolved during the heating and cooling phase changes in Au-47.5 at.% Cd polycrystals. The results are examined from the point of view of the stored <span class="hlt">elastic</span> <span class="hlt">strain</span> energy during the martensite formation, and the frictional work that is dissipated by the movement of martensite interfaces in either direction, upon heating and cooling.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2014JAP...115n3902D&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2014JAP...115n3902D&link_type=ABSTRACT"><span id="translatedtitle">Static and reversible <span class="hlt">elastic</span> <span class="hlt">strain</span> effects on magnetic order of La0.7Ca0.3MnO3/SrTiO3 superlattices</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Das, Sujit; Herklotz, Andreas; Jia Guo, Er; Dörr, Kathrin</p> <p>2014-04-01</p> <p>[La0.7Ca0.3MnO3(2.6 nm)/SrTiO3(6.3 nm)]15 superlattices (SLs) have been simultaneously grown by Pulsed Laser Deposition (PLD) on different oxide substrates in an attempt to obtain different residual <span class="hlt">strain</span> states. The substrates are (100)-oriented SrTiO3 (STO), LaAlO3 (LAO), and piezoelectric 0.72Pb (Mg1.3 Nb2.3)3-0.28PbTiO3 (PMN-PT). The La0.7Ca0.3MnO3 layers show tensile <span class="hlt">strain</span> of ɛ = 1% on LAO and stronger <span class="hlt">strain</span> on STO and PMN-PT (ɛ = 1.7%). The magnetization has been measured and is found to be quite different for the three SLs. Reversible biaxial compression of Δɛ=-0.1% using the PMN-PT substrate helps one to estimate which part of the differences in magnetic order among the samples is induced by <span class="hlt">elastic</span> <span class="hlt">strain</span>. The influence of <span class="hlt">elastic</span> <span class="hlt">strain</span> is found to be substantial, but does not completely account for the different behavior of the samples.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2004JSMEA..47...35S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2004JSMEA..47...35S"><span id="translatedtitle">A Determination Procedure for Element Elimination Criterion in <span class="hlt">Finite</span> Element Analysis of High-<span class="hlt">Strain</span>-Rate Impact/Penetration Phenomena</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Shin, Hyunho; Lee, Hun-Joo; Yoo, Yo-Han; Lee, Woong</p> <p></p> <p>A determination procedure for element elimination criterion in <span class="hlt">finite</span> element simulation of high-<span class="hlt">strain</span>-rate impact and penetration phenomena, occurring between tungsten heavy alloy long-rod penetrators and steel targets, has been presented with some demonstrations for the validity of the established criterion. The element elimination criterion for the two types of materials have been determined by comparing the simulated depth of penetration (DOP) and deformed shape of the penetrator with previously available experimental results. Although the criterion affects the simulated DOP significantly at the studied impact velocity of 1500m/s, once established, they are shown to be valid in predicting the DOP in the impact velocity range between 1100 and 1750m/s. The events of partial penetration with severe material deformation such as critical ricochet angle and ricochet phenomenology have also been successfully predicted using the established criterion in the similar impact velocity range. Thus it is suggested that the determination procedure for the suitable element erosion criterion is prerequisite in simulating high-<span class="hlt">strain</span>-rate impact/penetration phenomena and the criterion established by the procedure is useful in fairly broad range of the velocity and for other similar high-<span class="hlt">strain</span>-rate events.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4637043','PMC'); return false;" href="http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4637043"><span id="translatedtitle">Assessment of Hip Fracture Risk Using Cross-Section <span class="hlt">Strain</span> Energy Determined by QCT-Based <span class="hlt">Finite</span> Element Modeling</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Kheirollahi, Hossein; Luo, Yunhua</p> <p>2015-01-01</p> <p>Accurate assessment of hip fracture risk is very important to prevent hip fracture and to monitor the effect of a treatment. A subject-specific QCT-based <span class="hlt">finite</span> element model was constructed to assess hip fracture risk at the critical locations of femur during the single-leg stance and the sideways fall. The aim of this study was to improve the prediction of hip fracture risk by introducing a novel failure criterion to more accurately describe bone failure mechanism. Hip fracture risk index was defined using cross-section <span class="hlt">strain</span> energy, which is able to integrate information of stresses, <span class="hlt">strains</span>, and material properties affecting bone failure. It was found that the femoral neck and the intertrochanteric region have higher fracture risk than other parts of the femur, probably owing to the larger content of cancellous bone in these regions. The study results also suggested that women are more prone to hip fracture than men. The findings in this study have a good agreement with those clinical observations reported in the literature. The proposed hip fracture risk index based on <span class="hlt">strain</span> energy has the potential of more accurate assessment of hip fracture risk. However, experimental validation should be conducted before its clinical applications. PMID:26601105</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/25986928','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/25986928"><span id="translatedtitle">Mechanoelectrochemical catalysis of the effect of <span class="hlt">elastic</span> <span class="hlt">strain</span> on a platinum nanofilm for the ORR exerted by a shape memory alloy substrate.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Du, Minshu; Cui, Lishan; Cao, Yi; Bard, Allen J</p> <p>2015-06-17</p> <p>Both the ligand effect and surface <span class="hlt">strain</span> can affect the electrocatalytic reactivity. In that matter exists a need to be fundamentally understood; however, there is no effective strategy to isolate the <span class="hlt">strain</span> effect in electrocatalytic systems. In this research we show how the <span class="hlt">elastic</span> <span class="hlt">strain</span> in a platinum nanofilm varies the catalytic activity for the oxygen reduction reaction, a key barrier to the wide applications of fuel cells. NiTi shape memory alloy was selected as the substrate to <span class="hlt">strain</span> engineer the deposited Pt nanofilm in both compressively and tensilely <span class="hlt">strained</span> states by taking advantage of the two-way shape memory effect for the first time. We demonstrate that compressive <span class="hlt">strain</span> weakens the Pt surface adsorption and hence improves the ORR activity, which reflects in a 52% enhancement of the kinetic rate constant and a 27 mV positive shift of the half-wave potential for the compressively <span class="hlt">strained</span> 5 nm Pt compared to the pristine Pt. Tensile <span class="hlt">strain</span> has the opposite effect, which is in general agreement with the proposed d-band theory. PMID:25986928</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/20552248','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/20552248"><span id="translatedtitle">Three-dimensional <span class="hlt">elastic</span> image registration based on <span class="hlt">strain</span> energy minimization: application to prostate magnetic resonance imaging.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Zhang, Bao; Arola, Dwayne D; Roys, Steve; Gullapalli, Rao P</p> <p>2011-08-01</p> <p>The use of magnetic resonance (MR) imaging in conjunction with an endorectal coil is currently the clinical standard for the diagnosis of prostate cancer because of the increased sensitivity and specificity of this approach. However, imaging in this manner provides images and spectra of the prostate in the deformed state because of the insertion of the endorectal coil. Such deformation may lead to uncertainties in the localization of prostate cancer during therapy. We propose a novel 3-D <span class="hlt">elastic</span> registration procedure that is based on the minimization of a physically motivated <span class="hlt">strain</span> energy function that requires the identification of similar features (points, curves, or surfaces) in the source and target images. The Gauss-Seidel method was used in the numerical implementation of the registration algorithm. The registration procedure was validated on synthetic digital images, MR images from prostate phantom, and MR images obtained on patients. The registration error, assessed by averaging the displacement of a fiducial landmark in the target to its corresponding point in the registered image, was 0.2 ± 0.1 pixels on synthetic images. On the prostate phantom and patient data, the registration errors were 1.0 ± 0.6 pixels (0.6 ± 0.4 mm) and 1.8 ± 0.7 pixels (1.1 ± 0.4 mm), respectively. Registration also improved image similarity (normalized cross-correlation) from 0.72 ± 0.10 to 0.96 ± 0.03 on patient data. Registration results on digital images, phantom, and prostate data in vivo demonstrate that the registration procedure can be used to significantly improve both the accuracy of localized therapies such as brachytherapy or external beam therapy and can be valuable in the longitudinal follow-up of patients after therapy. PMID:20552248</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/15008368','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/15008368"><span id="translatedtitle">Coronary stent strut size dependent stress-<span class="hlt">strain</span> response investigated using micromechanical <span class="hlt">finite</span> element models.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Savage, P; O'Donnell, B P; McHugh, P E; Murphy, B P; Quinn, D F</p> <p>2004-02-01</p> <p>Cardiovascular stents are metal scaffolds that are used in the treatment of atherosclerosis. These devices are typically composed of very thin struts (< or = 100 microm thickness, for coronary applications). At this size-scale the question arises as to the suitability of using bulk material properties in stent design. This paper investigates the use of <span class="hlt">finite</span> element analysis to predict the mechanical failure of stent struts, typical of the strut size used in coronary stents. 316 L stainless steel in uniaxial loading was considered. To accurately represent the constitutive behavior of the material at this size-scale, a computational micromechanics approach was taken involving an explicit representation of the grain structure in the steel struts, and the use of crystal plasticity theory to represent the constitutive behavior of the individual grains. The development of the <span class="hlt">finite</span> element models is discussed and results are presented for the predictions of tensile mechanical behavior as a function of strut thickness. The results showed that using this modelling approach, a size effect, already seen experimentally, is produced. This has significant implications for stent design, especially in the context of the desire to produce smaller stents for small bore neurovascular and peripheral artery applications. PMID:15008368</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1982Tectp..88..313P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1982Tectp..88..313P"><span id="translatedtitle"><span class="hlt">Finite</span> <span class="hlt">strains</span> within recumbent folds of the kishorn Nappe, northwest Scotland</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Potts, G. J.</p> <p>1982-10-01</p> <p>This study is based on the Torridonian and Cambro-Ordovician rocks of the Kishorn Nappe on the Isle of Skye and the adjacent mainland of Scotland. Grain shape fabric, Skolithos pipe shape analysis and palaeomagnetic techniques have been used to give an indication of the <span class="hlt">strain</span> distribution and possible mechanisms involved in the generation of the recumbent folds within the Kishorn Nappe. Results indicate that recumbent folding has occurred without internal deformation.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2008cosp...37.3373W&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2008cosp...37.3373W&link_type=ABSTRACT"><span id="translatedtitle">Non-linear visco-<span class="hlt">elastic</span> analysis and the design of super-pressure balloons : stress, <span class="hlt">strain</span> and stability</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Wakefield, David</p> <p></p> <p>Tensys have a long-established background in the shape generation and load analysis of architectural stressed membrane structures. Founded upon their inTENS <span class="hlt">finite</span> element analysis suite, these activities have broadened to encompass ‘lighter than air' structures such as aerostats, hybrid air-vehicles and stratospheric balloons. Since 2004 Tensys have acted as consultants to the NASA Ultra Long Duration Balloon (ULDB) Program. Early implementations of the super-pressure balloon design chosen for ULDB have shown problems of geometric instability, characterised by improper deployment and the potential for overall geometric instability once deployed. The latter has been reproduced numerically using inTENS, and the former are better understood following a series of large-scale hangar tests simulating launch and ascent. In both cases the solution lies in minimising the film lobing between the tendons. These tendons, which span between base and apex end fittings, cause the characteristic pumpkin shape of the balloons and also provide valuable constraint against excessive film deformation. There is also the requirement to generate a biaxial stress field in order to mobilise in-plane shear stiffness. A consequence of reduced lobing between tendons is the development of higher stresses in the balloon film under pressure. The different thermal characteristics between tendons and film lead to further significant meridional stress under low temperature flight conditions. The non-linear viscoelastic response of the envelope film acts positively to help dissipate excessive stress and local concentrations. However, creep over time may produce lobe geometry variations sufficient to compromise the geometric stability of the balloon. The design of a balloon requires an analysis approach that addresses the questions of stress and stability over the duration of a flight by time stepping analyses using an appropriate material model. This paper summarises the Dynamic Relaxation</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/26710676','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/26710676"><span id="translatedtitle"><span class="hlt">Finite</span> element modelling of the common carotid artery in the elderly with physiological intimal thickening using layer-specific stress-released geometries and nonlinear <span class="hlt">elastic</span> properties.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Esmaeili Monir, Hamed; Yamada, Hiroshi; Sakata, Noriyuki</p> <p>2016-09-01</p> <p>To investigate the mechanical effects of tissue responses, such as remodelling, in the arteries of the elderly, it is important to evaluate stress in the intimal layer. In this study, we investigated a novel technique to evaluate the effect of layer-specific characteristics on stress in the arterial wall in an elderly subject. We used <span class="hlt">finite</span> element analysis of a segment of carotid artery with intimal thickening, incorporating stress-released geometries and the stress-<span class="hlt">strain</span> relationships for three separate wall layers. We correlated the stress-<span class="hlt">strain</span> relationships and local curvatures of the layers with the stress on the arterial wall under physiological loading. The simulation results show that both the stress-<span class="hlt">strain</span> relationship and the local curvature of the innermost stress-released layer influence the circumferential stress and its radial gradient. This indicates that intimal stress is influenced significantly by location-dependent intimal remodelling. However, further investigation is needed before conclusive inferences can be drawn. PMID:26710676</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/22263808','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/22263808"><span id="translatedtitle">Improved detection of rough defects for ultrasonic NDE inspections based on <span class="hlt">finite</span> element modeling of <span class="hlt">elastic</span> wave scattering</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Pettit, J. R.; Walker, A.; Lowe, M. J. S.</p> <p>2014-02-18</p> <p>Defects which posses rough surfaces greatly affect ultrasonic wave scattering behaviour, often reducing the magnitude of reflected signals. Ultrasonic inspections rely upon this response for detecting and sizing flaws. For safety critical components reliable characterisation is crucial. Therefore, providing an accurate means to predict reductions in signal amplitude is essential. An extension of Kirchhoff theory has formed the basis for the UK power industry inspection justifications. However, it is widely recognised that these predictions are pessimistic owing to analytical approximations. A numerical full field modelling approach does not fall victim to such limitations. Here, a <span class="hlt">Finite</span> Element model is used to aid in setting a non-conservative reporting threshold during the inspection of a large pressure vessel forging that might contain embedded rough defects. The ultrasonic response from multiple rough surfaces defined by the same statistical class is calculated for normal incident compression waves. The approach is validated by comparing coherent scattering with predictions made by Kirchhoff theory. At lower levels of roughness excellent agreement is observed, whilst higher values confirm the pessimism of Kirchhoff theory. Furthermore, the mean amplitude in the specular direction is calculated. This represents the information obtained during an inspection, indicating that reductions due to increasing roughness are significantly less than the coherent component currently being used.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li class="active"><span>19</span></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_19 --> <div id="page_20" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li class="active"><span>20</span></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="381"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013SPIE.8788E..07T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013SPIE.8788E..07T"><span id="translatedtitle">Holographic Interferometry based on photorefractive crystal to measure 3D thermo-<span class="hlt">elastic</span> distortion of composite structures and comparison with <span class="hlt">finite</span> element models</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Thizy, C.; Eliot, F.; Ballhause, D.; Olympio, K. R.; Kluge, R.; Shannon, A.; Laduree, G.; Logut, D.; Georges, M. P.</p> <p>2013-04-01</p> <p>Thermo-<span class="hlt">elastic</span> distortions of composite structures have been measured by a holographic camera using a BSO photorefractive crystal as the recording medium. The first test campaign (Phase 1) was performed on CFRP struts with titanium end-fittings glued to the tips of the strut. The samples were placed in a vacuum chamber. The holographic camera was located outside the chamber and configured with two illuminations to measure the relative out-of-plane and in-plane (in one direction) displacements. The second test campaign (Phase 2) was performed on a structure composed of a large Silicon Carbide base plate supported by 3 GFRP struts with glued Titanium end-fittings. Thermo-<span class="hlt">elastic</span> distortions have been measured with the same holographic camera used in phase 1, but four illuminations, instead of two, have been used to provide the three components of displacement. This technique was specially developed and validated during the phase 2 in CSL laboratory. The system has been designed to measure an object size of typically 250x250 mm2; the measurement range is such that the sum of the largest relative displacements in the three measurement directions is maximum 20 μm. The validation of the four-illuminations technique led to measurement uncertainties of 120 nm for the relative in-plane and out-of-plane displacements, 230 nm for the absolute in-plane displacement and 400 nm for the absolute out-of-plane displacement. For both campaigns, the test results have been compared to the predictions obtained by <span class="hlt">finite</span> element analyses and the correlation of these results was good.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=19940002917&hterms=finite+math&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3Dfinite%2Bmath','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=19940002917&hterms=finite+math&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3Dfinite%2Bmath"><span id="translatedtitle">MCFET - A MICROSTRUCTURAL LATTICE MODEL FOR <span class="hlt">STRAIN</span> ORIENTED PROBLEMS: A COMBINED MONTE CARLO <span class="hlt">FINITE</span> ELEMENT TECHNIQUE</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Gayda, J.</p> <p>1994-01-01</p> <p>A specialized, microstructural lattice model, termed MCFET for combined Monte Carlo <span class="hlt">Finite</span> Element Technique, has been developed to simulate microstructural evolution in material systems where modulated phases occur and the directionality of the modulation is influenced by internal and external stresses. Since many of the physical properties of materials are determined by microstructure, it is important to be able to predict and control microstructural development. MCFET uses a microstructural lattice model that can incorporate all relevant driving forces and kinetic considerations. Unlike molecular dynamics, this approach was developed specifically to predict macroscopic behavior, not atomistic behavior. In this approach, the microstructure is discretized into a fine lattice. Each element in the lattice is labeled in accordance with its microstructural identity. Diffusion of material at elevated temperatures is simulated by allowing exchanges of neighboring elements if the exchange lowers the total energy of the system. A Monte Carlo approach is used to select the exchange site while the change in energy associated with stress fields is computed using a <span class="hlt">finite</span> element technique. The MCFET analysis has been validated by comparing this approach with a closed-form, analytical method for stress-assisted, shape changes of a single particle in an infinite matrix. Sample MCFET analyses for multiparticle problems have also been run and, in general, the resulting microstructural changes associated with the application of an external stress are similar to that observed in Ni-Al-Cr alloys at elevated temperatures. This program is written in FORTRAN for use on a 370 series IBM mainframe. It has been implemented on an IBM 370 running VM/SP and an IBM 3084 running MVS. It requires the IMSL math library and 220K of RAM for execution. The standard distribution medium for this program is a 9-track 1600 BPI magnetic tape in EBCDIC format.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016ApPhL.109d2902A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016ApPhL.109d2902A"><span id="translatedtitle">Insight into magnetic, ferroelectric and <span class="hlt">elastic</span> properties of <span class="hlt">strained</span> BiFeO3 thin films through Mössbauer spectroscopy</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Agbelele, A.; Sando, D.; Infante, I. C.; Carrétéro, C.; Jouen, S.; Le Breton, J.-M.; Barthélémy, A.; Dkhil, B.; Bibes, M.; Juraszek, J.</p> <p>2016-07-01</p> <p>We have studied the magnetic order of highly <span class="hlt">strained</span> (001)-oriented BiFeO3 (BFO) thin films using 57Fe Conversion Electron Mössbauer Spectrometry. From 90 K to 620 K the films exhibit a collinear antiferromagnetic structure, in contrast with the cycloidal structure observed in bulk BFO. Moreover, we find that both the planar magnetic anisotropy for compressive <span class="hlt">strain</span> and out-of-plane anisotropy for tensile <span class="hlt">strain</span> persist from 90 K up to the Néel temperature (TN), which itself shows only a weak <span class="hlt">strain</span> dependence. An analysis of the line asymmetry of the paramagnetic doublet for temperatures above TN is used to reveal the <span class="hlt">strain</span>-dependent rotation of the polarization direction, consistent with previous observations. Our results show that the lattice dynamics in BFO films are strongly <span class="hlt">strain</span>-dependent, offering avenues toward acoustic phonon devices. Finally, we use the versatility of Mössbauer spectroscopy technique to reveal various multi-property features including magnetic states, polarization direction and <span class="hlt">elastic</span> <span class="hlt">strain</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4694267','PMC'); return false;" href="http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4694267"><span id="translatedtitle">Role of ultrasonography in the evaluation of correlation between <span class="hlt">strain</span> and <span class="hlt">elasticity</span> of common carotid artery in patients with diabetic nephropathy</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Zou, Chunpeng; Jiao, Yan; Li, Xingwang; Zheng, Chao; Chen, Maohua; Hu, Chunhong</p> <p>2015-01-01</p> <p>Objective: This study aimed to investigate the correlation between <span class="hlt">strain</span> and <span class="hlt">elasticity</span> of the common carotid artery (CCA) by ultrasonography and evaluate its clinical significance in patients with diabetic nephropathy (DN). Methods: A total of 68 DN patients and 54 healthy subjects were randomly recruited from the Ultrasound Department from April 2014 to March 2015. The maximum of circumferential <span class="hlt">strain</span> (CSmax), maximum of circumferential <span class="hlt">strain</span> rate (CSRmax), compliance coefficient (CC) and stiffness index (β) of the CCA were determined by ultrasonography in all the patients, and correlation analysis was performed. Results: The CC, CSmax and CSRmax in DN group were significantly lower than in healthy controls (P<0.05), but β was markedly higher than in control group (P<0.05). There was a significantly positive correlation of CSmax and CSRmax with CC and a negative correlation with β in both control group and DN group. Conclusion: There is significant correlation between <span class="hlt">strain</span> and <span class="hlt">elastic</span> of the CCA. CSmax and CSRmax may be used to reflect the mechanical characteristics of CCA. PMID:26770367</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2004JMMM..280..287V','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2004JMMM..280..287V"><span id="translatedtitle">Third-order <span class="hlt">elastic</span> constants of the alloy Fe 72Pt 28</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Vinu, T. P.; Menon, C. S.</p> <p>2004-09-01</p> <p>The complete sets of second- and third-order <span class="hlt">elastic</span> constants of the cubic Fe72Pt28 have been obtained using the <span class="hlt">strain</span> energy density derived from interactions up to three nearest neighbours of each atom in the unit cell. The <span class="hlt">finite</span> <span class="hlt">strain</span> <span class="hlt">elasticity</span> theory has been used to get the <span class="hlt">strain</span> energy density of Fe72Pt28. The <span class="hlt">strain</span> energy density is compared with the <span class="hlt">strain</span>-dependent lattice energy density obtained from the continuum model approximation and the expressions for the second- and third-order <span class="hlt">elastic</span> constants of Fe72Pt28 are given. The second-order potential parameter is deduced from the measured second-order <span class="hlt">elastic</span> constants of Fe72Pt28 and the third-order potential parameter is estimated from the Lennard-Jones inter-atomic potential for Fe72Pt28. The inter-lattice displacements; the three independent second-order <span class="hlt">elastic</span> constants and the six independent third-order <span class="hlt">elastic</span> constants of Fe72Pt28 are also determined. The second-order <span class="hlt">elastic</span> constants are compared with the experimental <span class="hlt">elastic</span> constants of Fe72Pt28. We also study the effect of pressure on the second-order <span class="hlt">elastic</span> constants of Fe72Pt28.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015GeoJI.200..278D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015GeoJI.200..278D"><span id="translatedtitle">A comparison of <span class="hlt">finite</span>-difference and spectral-element methods for <span class="hlt">elastic</span> wave propagation in media with a fluid-solid interface</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>De Basabe, Jonás D.; Sen, Mrinal K.</p> <p>2015-01-01</p> <p>The numerical simulation of wave propagation in media with solid and fluid layers is essential for marine seismic exploration data analysis. The numerical methods for wave propagation that are applicable to this physical settings can be broadly classified as partitioned or monolithic: The partitioned methods use separate simulations in the fluid and solid regions and explicitly satisfy the interface conditions, whereas the monolithic methods use the same method in all the domain without any special treatment of the fluid-solid interface. Despite the accuracy of the partitioned methods, the monolithic methods are more common in practice because of their convenience. In this paper, we analyse the accuracy of several monolithic methods for wave propagation in the presence of a fluid-solid interface. The analysis is based on grid-dispersion criteria and numerical examples. The methods studied here include: the classical <span class="hlt">finite</span>-difference method (FDM) based on the second-order displacement formulation of the <span class="hlt">elastic</span> wave equation (DFDM), the staggered-grid <span class="hlt">finite</span> difference method (SGFDM), the velocity-stress FDM with a standard grid (VSFDM) and the spectral-element method (SEM). We observe that among these, DFDM and the first-order SEM have a large amount of grid dispersion in the fluid region which renders them impractical for this application. On the other hand, SGFDM, VSFDM and SEM of order greater or equal to 2 yield accurate results for the body waves in the fluid and solid regions if a sufficient number of nodes per wavelength is used. All of the considered methods yield limited accuracy for the surface waves because the proper boundary conditions are not incorporated into the numerical scheme. Overall, we demonstrate both by analytic treatment and numerical experiments, that a first-order velocity-stress formulation can, in general, be used in dealing with fluid-solid interfaces without using staggered grids necessarily.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/27435451','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/27435451"><span id="translatedtitle">Programmable shape transformation of <span class="hlt">elastic</span> spherical domes.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Abdullah, Arif M; Braun, Paul V; Hsia, K Jimmy</p> <p>2016-07-20</p> <p>We investigate mismatch <span class="hlt">strain</span> driven programmable shape transformation of spherical domes and report the effects of different geometric and structural characteristics on dome behavior in response to applied mismatch <span class="hlt">strain</span>. We envision a bilayer dome design where the differential swelling of the inner layer with respect to the passive outer layer in response to changes in dome surroundings (such as the introduction of an organic solvent) introduces mismatch <span class="hlt">strain</span> within the bilayer system and causes dome shape transformation. <span class="hlt">Finite</span> element analysis reveals that, in addition to snap-through, spherical domes undergo bifurcation buckling and eventually gradual bending to morph into cylinders with increasing mismatch <span class="hlt">strain</span>. Besides demonstrating how the snap-through energy barrier depends on the spherical dome shape, our analysis identifies three distinct groups of dome geometries based on their mismatch <span class="hlt">strain</span>-transformed configuration relationships. Our experiments with polymer-based <span class="hlt">elastic</span> bilayer domes that exhibit differential swelling in organic solvents qualitatively confirm the <span class="hlt">finite</span> element predictions. We establish that, in addition to externally applied stimuli (mismatch <span class="hlt">strain</span>), bilayer spherical dome morphing can be tuned and hence programmed through its geometry and structural characteristics. Incorporation of an <span class="hlt">elastic</span> instability mechanism such as snap-through within the framework of stimuli-responsive functional devices can improve their response time which is otherwise controlled by diffusion. Hence, our proposed design guidelines can be used to realize deployable, multi-functional, reconfigurable, and therefore, adaptive structures responsive to a diverse set of stimuli across multiple length scales. PMID:27435451</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016JIEIC.tmp...82J','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016JIEIC.tmp...82J"><span id="translatedtitle"><span class="hlt">Finite</span> Element Simulation of Temperature and <span class="hlt">Strain</span> Distribution during Friction Stir Welding of AA2024 Aluminum Alloy</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Jain, Rahul; Pal, Surjya Kanta; Singh, Shiv Brat</p> <p>2016-06-01</p> <p>Friction Stir Welding (FSW) is a solid state joining process and is handy for welding aluminum alloys. <span class="hlt">Finite</span> Element Method (FEM) is an important tool to predict state variables of the process but numerical simulation of FSW is highly complex due to non-linear contact interactions between tool and work piece and interdependency of displacement and temperature. In the present work, a three dimensional coupled thermo-mechanical method based on Lagrangian implicit method is proposed to study the thermal history, <span class="hlt">strain</span> distribution and thermo-mechanical process in butt welding of Aluminum alloy 2024 using DEFORM-3D software. Workpiece is defined as rigid-visco plastic material and sticking condition between tool and work piece is defined. Adaptive re-meshing is used to tackle high mesh distortion. Effect of tool rotational and welding speed on plastic <span class="hlt">strain</span> is studied and insight is given on asymmetric nature of FSW process. Temperature distribution on the workpiece and tool is predicted and maximum temperature is found in workpiece top surface.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015JPhCS.628a2067K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015JPhCS.628a2067K"><span id="translatedtitle">Damage Detection in Wind Turbine Towers using a <span class="hlt">Finite</span> Element Model and Discrete Wavelet Transform of <span class="hlt">Strain</span> Signals</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kenna, A.; Basu, B.</p> <p>2015-07-01</p> <p>Wind turbine support towers at heights in excess of 90m are nowadays being formed in steel, concrete and hybrid concrete and steel structures. As is the case for all towers of this height, the towers will be assembled using a number of segments, which will be connected in some way. These local connections are to be viewed as areas of potential local weakness in the overall tower assembly and require care in terms of design and construction. This work concentrates on identifying local damage which can occur at an interface connection by either material or bolt/tendon failure. Spatial <span class="hlt">strain</span> patterns will be used to try to identify local damage areas around a 3 dimensional tower shell. A <span class="hlt">Finite</span> Element (FE) model will be assembled which will describe a hybrid tower as a continuum of four-noded, two-dimensional Reisser- Mindlin shell elements. In order to simulate local damage, an element around the circumference of the tower interface will be subjected to a reduced stiffness. <span class="hlt">Strain</span> patterns will be observed both in the undamaged and damaged states and these signals will be processed using a Discrete Wavelet Transform (DWT) algorithm to investigate if the damaged element can be identified.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014MMTA...45.6008J','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014MMTA...45.6008J"><span id="translatedtitle">Local and Global Stress-<span class="hlt">Strain</span> Behaviors of Transformation-Induced Plasticity Steel Using the Combined Nanoindentation and <span class="hlt">Finite</span> Element Analysis Method</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Jeong, Hyeok Jae; Lim, Nam Suk; Lee, Bong Ho; Park, Chan Gyung; Lee, Sunghak; Kang, Seong-Hoon; Lee, Ho Won; Kim, Hyoung Seop</p> <p>2014-12-01</p> <p>Transformation-induced plasticity (TRIP) steels have excellent <span class="hlt">strain</span> hardening exponents and resistibility against tensile necking using the <span class="hlt">strain</span>-induced martensite formation that occurs as a result of the plastic deformation and <span class="hlt">strain</span> on the retained austenite phase. Detailed studies on the microstructures and local mechanical properties, as well as global mechanical properties, are necessary in order to thoroughly understand the properties of TRIP steels with multiple phases of ferrite, bainite, retained austenite, and martensite. However, methods for investigating the local properties of the various phases of the TRIP steel are limited due to the very complicated and fine microstructures present in TRIP steel. In this study, the experimental and numerical methods, i.e., the experimental nanoindenting results and the theoretical <span class="hlt">finite</span> element analyses, were combined in order to extract the local stress-<span class="hlt">strain</span> curves of each phase. The local stress-<span class="hlt">strain</span> curves were in good agreement with the values presented in the literature. In particular, the global plastic stress-<span class="hlt">strain</span> behavior of the TRIP steel was predicted using the multiple phase unit cell <span class="hlt">finite</span> element analysis, and this demonstrated the validity of the obtained properties of each local phase. The method of extracting the local stress-<span class="hlt">strain</span> curves from the nanoindenting curves and predicting the global stress-<span class="hlt">strain</span> behavior assists in clarifying the smart design of multi-phase steels.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014MMTA..tmp..391J','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014MMTA..tmp..391J"><span id="translatedtitle">Local and Global Stress-<span class="hlt">Strain</span> Behaviors of Transformation-Induced Plasticity Steel Using the Combined Nanoindentation and <span class="hlt">Finite</span> Element Analysis Method</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Jeong, Hyeok Jae; Lim, Nam Suk; Lee, Bong Ho; Park, Chan Gyung; Lee, Sunghak; Kang, Seong-Hoon; Lee, Ho Won; Kim, Hyoung Seop</p> <p>2014-09-01</p> <p>Transformation-induced plasticity (TRIP) steels have excellent <span class="hlt">strain</span> hardening exponents and resistibility against tensile necking using the <span class="hlt">strain</span>-induced martensite formation that occurs as a result of the plastic deformation and <span class="hlt">strain</span> on the retained austenite phase. Detailed studies on the microstructures and local mechanical properties, as well as global mechanical properties, are necessary in order to thoroughly understand the properties of TRIP steels with multiple phases of ferrite, bainite, retained austenite, and martensite. However, methods for investigating the local properties of the various phases of the TRIP steel are limited due to the very complicated and fine microstructures present in TRIP steel. In this study, the experimental and numerical methods, i.e., the experimental nanoindenting results and the theoretical <span class="hlt">finite</span> element analyses, were combined in order to extract the local stress-<span class="hlt">strain</span> curves of each phase. The local stress-<span class="hlt">strain</span> curves were in good agreement with the values presented in the literature. In particular, the global plastic stress-<span class="hlt">strain</span> behavior of the TRIP steel was predicted using the multiple phase unit cell <span class="hlt">finite</span> element analysis, and this demonstrated the validity of the obtained properties of each local phase. The method of extracting the local stress-<span class="hlt">strain</span> curves from the nanoindenting curves and predicting the global stress-<span class="hlt">strain</span> behavior assists in clarifying the smart design of multi-phase steels.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3413382','PMC'); return false;" href="http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3413382"><span id="translatedtitle">A nonlinear <span class="hlt">elasticity</span> phantom containing spherical inclusions</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Pavan, Theo Z.; Madsen, Ernest L.; Frank, Gary R.; Jiang, Jingfeng; Carneiro, Antonio Adilton O.; Hall, Timothy J.</p> <p>2012-01-01</p> <p>The <span class="hlt">strain</span> image contrast of some in vivo breast lesions changes with increasing applied load. This change is attributed to differences in the nonlinear <span class="hlt">elastic</span> properties of the constituent tissues suggesting some potential to help classify breast diseases by their nonlinear <span class="hlt">elastic</span> properties. A phantom with inclusions and long-term stability is desired to serve as a test bed for nonlinear <span class="hlt">elasticity</span> imaging method development, testing, etc. This study reports a phantom designed to investigate nonlinear <span class="hlt">elastic</span> properties with ultrasound elastographic techniques. The phantom contains four spherical inclusions and was manufactured from a mixture of gelatin, agar and oil. The phantom background and each of the inclusions has distinct Young’s modulus and nonlinear mechanical behavior. This phantom was subjected to large deformations (up to 20%) while scanning with ultrasound, and changes in <span class="hlt">strain</span> image contrast and contrast-to-noise ratio (CNR) between inclusion and background, as a function of applied deformation, were investigated. The changes in contrast over a large deformation range predicted by the <span class="hlt">finite</span> element analysis (FEA) were consistent with those experimentally observed. Therefore, the paper reports a procedure for making phantoms with predictable nonlinear behavior, based on independent measurements of the constituent materials, and shows that the resulting <span class="hlt">strain</span> images (e.g., <span class="hlt">strain</span> contrast) agrees with that predicted with nonlinear FEA. PMID:22772074</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012ChPhL..29b6101C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012ChPhL..29b6101C"><span id="translatedtitle">Dislocation and <span class="hlt">Elastic</span> <span class="hlt">Strain</span> in an InN Film Characterized by Synchrotron Radiation X-Ray Diffraction and Rutherford Backscattering/Channeling</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Cheng, Feng-Feng; Fa, Tao; Wang, Xin-Qiang; Yao, Shu-De</p> <p>2012-02-01</p> <p>Dislocation information and <span class="hlt">strain</span>-related tetragonal distortion as well as crystalline qualities of a 2-μm-thick InN film grown by molecular beam epitaxy (MBE) are characterized by Rutherford backscattering/channeling (RBS/C) and synchrotron radiation x-ray diffraction (SR-XRD). The minimum yield χmin = 2.5% deduced from the RBS/C results indicates a fairly good crystalline quality. From the SR-XRD results, we obtain the values of the screw and edge densities to be ρscrew = 7.0027 × 109 and ρedge = 8.6115 × 109 cm-2, respectively. The tetragonal distortion of the sample is found to be -0.27% by angular scans, which is close to the -0.28% derived by SR-XRD. The value of |e⊥/e∥| = 0.6742 implies that the InN layer is much stiffer along the a axis than that along the c axis, where e∥ is the parallel <span class="hlt">elastic</span> <span class="hlt">strain</span>, and e⊥ is the perpendicular <span class="hlt">elastic</span> <span class="hlt">strain</span>. Photoluminescence results reveal a main peak of 0.653 eV with the linewidth of 60 meV, additional shoulder band could be due to impurities and related defects.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2006JSV...291...19H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2006JSV...291...19H"><span id="translatedtitle">The transient responses of a special non-homogeneous magneto-electro-<span class="hlt">elastic</span> hollow cylinder for axisymmetric plane <span class="hlt">strain</span> problem</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Hou, P. F.; Ding, H. J.; Leung, A. Y. T.</p> <p>2006-03-01</p> <p>By virtue of the introduction of new dependent variable and the separation of variables technique, the transient responses of a special non-homogeneous magneto-electro-<span class="hlt">elastic</span> hollow cylinder are transformed to two Volterra integral equations of the second kind of about two functions with respect to time. These integral equations can be solved successfully by means of the interpolation method. Then, the complete solutions of displacements, stresses, electric potential, electric displacements, magnetic potential and magnetic inductions are obtained. The present method is suitable for a magneto-electro-<span class="hlt">elastic</span> hollow cylinder with an arbitrary thickness subjected to arbitrary axisymmetric mechanical and electromagnetic loads. Numerical results are finally presented.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014OptLE..54...79E','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014OptLE..54...79E"><span id="translatedtitle">In situ identification of <span class="hlt">elastic</span>-plastic <span class="hlt">strain</span> distribution in a microalloyed transformation induced plasticity steel using digital image correlation</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Eskandari, M.; Zarei-Hanzaki, A.; Yadegari, M.; Soltani, N.; Asghari, A.</p> <p>2014-03-01</p> <p>A non-contact <span class="hlt">strain</span> measurement technique, based on an in-situ digital image correlation (DIC) method in association with magnetic martensite point measurement (Feritoscopy testing) was applied to study inhomogeneous deformation corresponding to martensitic transformation of a microalloyed low carbon transformation induced plasticity steel during tensile <span class="hlt">straining</span>. The progress of inhomogeneous deformation is traced by the <span class="hlt">strain</span> maps. The microstructural observation is used to validate the DIC results. The experimental steel shows continuous yielding with a high true fracture strength of 1410±10 MPa at 25 °C along with the lack of tensile necking. The DIC results show that the yield point is controlled by stress-assisted martensite transformation, which in turn induces the <span class="hlt">strain</span> inhomogeneity. The latter starts prior to the yield point after <span class="hlt">straining</span> to 0.016. The microstructural evolution reveals the ɛ-martensite is obtained through stress-assisted martensite formation. After yielding, thanks to the <span class="hlt">strain</span>-induced martensite transformation, the deformation inhomogeneity in <span class="hlt">strain</span> maps is increased with <span class="hlt">strain</span>, corresponding to increasing the volume fraction of martensite. The results suggest that the continuous yielding and initial <span class="hlt">strain</span> hardening is controlled by stress-assisted martensite formation while the higher total elongation to fracture (80%) and the tensile necking behavior is mainly influenced by the <span class="hlt">strain</span>-induced martensite transformation.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4923539','PMC'); return false;" href="http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4923539"><span id="translatedtitle">Influence of Trabecular Bone on Peri-Implant Stress and <span class="hlt">Strain</span> Based on Micro-CT <span class="hlt">Finite</span> Element Modeling of Beagle Dog</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Liao, Sheng-hui; Zhu, Xing-hao; Xie, Jing; Sohodeb, Vikesh Kumar; Ding, Xi</p> <p>2016-01-01</p> <p>The objective of this investigation is to analyze the influence of trabecular microstructure modeling on the biomechanical distribution of the implant-bone interface. Two three-dimensional <span class="hlt">finite</span> element mandible models, one with trabecular microstructure (a refined model) and one with macrostructure (a simplified model), were built. The values of equivalent stress at the implant-bone interface in the refined model increased compared with those of the simplified model and <span class="hlt">strain</span> on the contrary. The distributions of stress and <span class="hlt">strain</span> were more uniform in the refined model of trabecular microstructure, in which stress and <span class="hlt">strain</span> were mainly concentrated in trabecular bone. It was concluded that simulation of trabecular bone microstructure had a significant effect on the distribution of stress and <span class="hlt">strain</span> at the implant-bone interface. These results suggest that trabecular structures could disperse stress and <span class="hlt">strain</span> and serve as load buffers. PMID:27403424</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/27403424','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/27403424"><span id="translatedtitle">Influence of Trabecular Bone on Peri-Implant Stress and <span class="hlt">Strain</span> Based on Micro-CT <span class="hlt">Finite</span> Element Modeling of Beagle Dog.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Liao, Sheng-Hui; Zhu, Xing-Hao; Xie, Jing; Sohodeb, Vikesh Kumar; Ding, Xi</p> <p>2016-01-01</p> <p>The objective of this investigation is to analyze the influence of trabecular microstructure modeling on the biomechanical distribution of the implant-bone interface. Two three-dimensional <span class="hlt">finite</span> element mandible models, one with trabecular microstructure (a refined model) and one with macrostructure (a simplified model), were built. The values of equivalent stress at the implant-bone interface in the refined model increased compared with those of the simplified model and <span class="hlt">strain</span> on the contrary. The distributions of stress and <span class="hlt">strain</span> were more uniform in the refined model of trabecular microstructure, in which stress and <span class="hlt">strain</span> were mainly concentrated in trabecular bone. It was concluded that simulation of trabecular bone microstructure had a significant effect on the distribution of stress and <span class="hlt">strain</span> at the implant-bone interface. These results suggest that trabecular structures could disperse stress and <span class="hlt">strain</span> and serve as load buffers. PMID:27403424</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009EGUGA..1112549P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009EGUGA..1112549P"><span id="translatedtitle">Characterising The Role of Basin Margin Structure On <span class="hlt">Finite</span> <span class="hlt">Strain</span> Patterns Across A 'Cleavage' Front From The Variscan Of Southern Ireland</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Parker, C.; Meere, P.; Mulchrone, K.; Stevenson, C.</p> <p>2009-04-01</p> <p><span class="hlt">Strain</span> analysis is commonly based on the axial ratio measurements of populations of approximately ellipsoid objects (e.g. sedimentary clasts), based on the assumption that these ‘<span class="hlt">strain</span> markers' act passively during deformation. However truly passive <span class="hlt">strain</span> markers are rare due to competency contrasts which can lead to underestimates of <span class="hlt">strain</span> where the <span class="hlt">strain</span> markers are more rigid than the deforming host. (Meere et al., 2007). Therefore we have used a combination of traditional <span class="hlt">strain</span> analysis of sedimentary clasts, field and microstructural observations and anisotropy of magnetic susceptibility (AMS) measurements to quantify and validate the <span class="hlt">finite</span> <span class="hlt">strain</span> patterns across the Irish Variscan cleavage front. This region lies at the northern boundary of the European Rhenohercynian. Deformation of a thick (7 km +) Upper Devonian continental clastic sequence and overlying Carboniferous marine carbonate/clast sequence at the end of the Carboniferous consisted of an initial phase of layer parallel shortening, followed by folding, ongoing cleavage development and late stage accommodation thrusting. AMS data can help to quantify weak or subtle fabrics by effectively measuring the preferred orientation of iron bearing minerals (in this case clay minerals). Preliminary AMS results indicate a gradient in deformation intensity within lithologies across the cleavage front from the south to the north. A microstructural comparison from across the cleavage front is used to characterise the <span class="hlt">strain</span> regime either side of the boundary. Integrating these techniques will refine our current knowledge of spatial distributions of <span class="hlt">strain</span> in the periphery of orogenic forelands.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015EGUGA..17.1458H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015EGUGA..17.1458H"><span id="translatedtitle">Three-dimensional <span class="hlt">finite</span>-element modelling of horizontal surface velocity and <span class="hlt">strain</span> patterns near thrust and normal faults during the earthquake cycle: implications for interpreting geological and geodetic data</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Hampel, Andrea; Hetzel, Ralf</p> <p>2015-04-01</p> <p>In recent years, more and more geological and space-geodetic data on the surface deformation associated with earthquakes on intra-continental normal and thrust faults have become available. Here we use three-dimensional <span class="hlt">finite</span>-element models that account for gravity, far-field ("regional") extension/shortening and postseismic relaxation in a viscoelastic lower crust to quantify the surface deformation caused by an Mw ~7 earthquake on a dip-slip fault. The coseismic deformation is characterized by horizontal shortening in the footwall of the normal fault and extension in the hanging wall of the thrust fault - consistent with <span class="hlt">elastic</span> dislocation models, geological field observations and GPS data from earthquakes in Italy and Taiwan. During the postseismic phase, domains of extensional and contractional <span class="hlt">strain</span> exist next to each other near both fault types. The spatiotemporal evolution of these domains as well as the postseismic velocities and <span class="hlt">strain</span> rates strongly depend on the viscosity of the lower crust. For viscosities of 1e18-1e20 Pa s, the signal from postseismic relaxation is detectible for 20-50 years after the earthquake. If GPS data containing a postseismic relaxation signal are used to derive regional rates, the stations may show rates that are too high or too low or even an apparently wrong tectonic regime. By quantifying the postseismic deformation through space and time, our models help to interpret GPS data and to identify the most suitable locations for GPS stations.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/26944687','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/26944687"><span id="translatedtitle">How accurately can subject-specific <span class="hlt">finite</span> element models predict <span class="hlt">strains</span> and strength of human femora? Investigation using full-field measurements.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Grassi, Lorenzo; Väänänen, Sami P; Ristinmaa, Matti; Jurvelin, Jukka S; Isaksson, Hanna</p> <p>2016-03-21</p> <p>Subject-specific <span class="hlt">finite</span> element models have been proposed as a tool to improve fracture risk assessment in individuals. A thorough laboratory validation against experimental data is required before introducing such models in clinical practice. Results from digital image correlation can provide full-field <span class="hlt">strain</span> distribution over the specimen surface during in vitro test, instead of at a few pre-defined locations as with <span class="hlt">strain</span> gauges. The aim of this study was to validate <span class="hlt">finite</span> element models of human femora against experimental data from three cadaver femora, both in terms of femoral strength and of the full-field <span class="hlt">strain</span> distribution collected with digital image correlation. The results showed a high accuracy between predicted and measured principal <span class="hlt">strains</span> (R(2)=0.93, RMSE=10%, 1600 validated data points per specimen). Femoral strength was predicted using a rate dependent material model with specific <span class="hlt">strain</span> limit values for yield and failure. This provided an accurate prediction (<2% error) for two out of three specimens. In the third specimen, an accidental change in the boundary conditions occurred during the experiment, which compromised the femoral strength validation. The achieved <span class="hlt">strain</span> accuracy was comparable to that obtained in state-of-the-art studies which validated their prediction accuracy against 10-16 <span class="hlt">strain</span> gauge measurements. Fracture force was accurately predicted, with the predicted failure location being very close to the experimental fracture rim. Despite the low sample size and the single loading condition tested, the present combined numerical-experimental method showed that <span class="hlt">finite</span> element models can predict femoral strength by providing a thorough description of the local bone mechanical response. PMID:26944687</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li class="active"><span>20</span></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_20 --> <div id="page_21" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li class="active"><span>21</span></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="401"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1997JApMa..59..193W&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1997JApMa..59..193W&link_type=ABSTRACT"><span id="translatedtitle">An inclusion in one of two joined isotropic <span class="hlt">elastic</span> half-spaces</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Walpole, L. J.</p> <p>1997-10-01</p> <p>Two dissimilar, homogeneous and istropic, <span class="hlt">elastic</span> half-spaces are bonded together over thier infinite plane of contract. An arbitrarily shaped <span class="hlt">finite</span> part of one of them (an inclusion) tends spontaneously to undergo a unifrom infinitesimal <span class="hlt">strain</span>, but, as it remains attached to and restrained by the surrounding material, an equilibrated state of stress and <span class="hlt">strain</span> is established everywhere instead. By adopting a convenient expression for the fundamental field of a point force, we transformed inclusion. For a general shape of the inclussion and for particular spherical and <span class="hlt">finite</span> cylindrical shapes in detail, we consider the evaluation of the <span class="hlt">elastic</span> <span class="hlt">strain</span> energy, especially of the interaction term which depends on the location of the inclusion and both pairs of <span class="hlt">elastic</span> moduli, and which is of great significance in physical applications.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/10115625','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/10115625"><span id="translatedtitle">A theoretical analysis of the effect of uniaxial <span class="hlt">elastic</span> <span class="hlt">strain</span> on the critical temperature of cuprate superconductors</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Welch, D.O.; Baetzold, R.C.</p> <p>1992-12-31</p> <p>Factors which influence the effect of uniaxial stress and <span class="hlt">strain</span> on the superconducting critical temperature are discussed, with emphasis on the effect of uniaxial <span class="hlt">strain</span> on the mobile hole density of YBa{sub 2}Ci{sub 3}O{sub 7}.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/22492651','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/22492651"><span id="translatedtitle">Evolution of bulk <span class="hlt">strain</span> solitons in cylindrical inhomogeneous shells</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Shvartz, A. Samsonov, A.; Dreiden, G.; Semenova, I.</p> <p>2015-10-28</p> <p>Bulk <span class="hlt">strain</span> solitary waves in nonlinearly <span class="hlt">elastic</span> thin-walled cylindrical shells with variable geometrical and physical parameters are studied, and equation for the longitudinal <span class="hlt">strain</span> component with the variable coefficients is derived. A conservative <span class="hlt">finite</span> difference scheme is proposed, and the results of numerical simulation of the <span class="hlt">strain</span> soliton evolution in a shell with the abrupt variations of cross section and physical properties of the material are presented.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AIPC.1685g0014S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AIPC.1685g0014S"><span id="translatedtitle">Evolution of bulk <span class="hlt">strain</span> solitons in cylindrical inhomogeneous shells</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Shvartz, A.; Samsonov, A.; Dreiden, G.; Semenova, I.</p> <p>2015-10-01</p> <p>Bulk <span class="hlt">strain</span> solitary waves in nonlinearly <span class="hlt">elastic</span> thin-walled cylindrical shells with variable geometrical and physical parameters are studied, and equation for the longitudinal <span class="hlt">strain</span> component with the variable coefficients is derived. A conservative <span class="hlt">finite</span> difference scheme is proposed, and the results of numerical simulation of the <span class="hlt">strain</span> soliton evolution in a shell with the abrupt variations of cross section and physical properties of the material are presented.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/25956121','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/25956121"><span id="translatedtitle">Probing the cross-effect of <span class="hlt">strains</span> in non-linear <span class="hlt">elasticity</span> of nearly regular polymer networks by pure shear deformation.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Katashima, Takuya; Urayama, Kenji; Chung, Ung-il; Sakai, Takamasa</p> <p>2015-05-01</p> <p>The pure shear deformation of the Tetra-polyethylene glycol gels reveals the presence of an explicit cross-effect of <span class="hlt">strains</span> in the <span class="hlt">strain</span> energy density function even for the polymer networks with nearly regular structure including no appreciable amount of structural defect such as trapped entanglement. This result is in contrast to the expectation of the classical Gaussian network model (Neo Hookean model), i.e., the vanishing of the cross effect in regular networks with no trapped entanglement. The results show that (1) the cross effect of <span class="hlt">strains</span> is not dependent on the network-strand length; (2) the cross effect is not affected by the presence of non-network strands; (3) the cross effect is proportional to the network polymer concentration including both <span class="hlt">elastically</span> effective and ineffective strands; (4) no cross effect is expected exclusively in zero limit of network concentration in real polymer networks. These features indicate that the real polymer networks with regular network structures have an explicit cross-effect of <span class="hlt">strains</span>, which originates from some interaction between network strands (other than entanglement effect) such as nematic interaction, topological interaction, and excluded volume interaction. PMID:25956121</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/27150599','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/27150599"><span id="translatedtitle">The internal-<span class="hlt">strain</span> tensor of crystals for nuclear-relaxed <span class="hlt">elastic</span> and piezoelectric constants: on the full exploitation of its symmetry features.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Erba, Alessandro</p> <p>2016-05-18</p> <p>Symmetry features of the internal-<span class="hlt">strain</span> tensor of crystals (whose components are mixed second-energy derivatives with respect to atomic displacements and lattice <span class="hlt">strains</span>) are formally presented, which originate from translational-invariance, atomic equivalences, and atomic invariances. A general computational scheme is devised, and implemented into the public Crystal program, for the quantum-mechanical evaluation of the internal-<span class="hlt">strain</span> tensor of crystals belonging to any space-group, which takes full-advantage of the exploitation of these symmetry-features. The gain in computing time due to the full symmetry exploitation is documented to be rather significant not just for high-symmetry crystalline systems such as cubic, hexagonal or trigonal, but also for low-symmetry ones such as monoclinic and orthorhombic. The internal-<span class="hlt">strain</span> tensor is used for the evaluation of the nuclear relaxation term of the fourth-rank <span class="hlt">elastic</span> and third-rank piezoelectric tensors of crystals, where, apart from a reduction of the computing time, the exploitation of symmetry is documented to remarkably increase the numerical precision of computed coefficients. PMID:27150599</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/25190587','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/25190587"><span id="translatedtitle"><span class="hlt">Elastic</span> limit of silicane.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Peng, Qing; De, Suvranu</p> <p>2014-10-21</p> <p>Silicane is a fully hydrogenated silicene-a counterpart of graphene-having promising applications in hydrogen storage with capacities larger than 6 wt%. Knowledge of its <span class="hlt">elastic</span> limit is critical in its applications as well as tailoring its electronic properties by <span class="hlt">strain</span>. Here we investigate the mechanical response of silicane to various <span class="hlt">strains</span> using first-principles calculations based on density functional theory. We illustrate that non-linear <span class="hlt">elastic</span> behavior is prominent in two-dimensional nanomaterials as opposed to bulk materials. The <span class="hlt">elastic</span> limits defined by ultimate tensile <span class="hlt">strains</span> are 0.22, 0.28, and 0.25 along armchair, zigzag, and biaxial directions, respectively, an increase of 29%, 33%, and 24% respectively in reference to silicene. The in-plane stiffness and Poisson ratio are reduced by a factor of 16% and 26%, respectively. However, hydrogenation/dehydrogenation has little effect on its ultimate tensile strengths. We obtained high order <span class="hlt">elastic</span> constants for a rigorous continuum description of the nonlinear <span class="hlt">elastic</span> response. The limitation of second, third, fourth, and fifth order <span class="hlt">elastic</span> constants are in the <span class="hlt">strain</span> range of 0.02, 0.08, and 0.13, and 0.21, respectively. The pressure effect on the second order <span class="hlt">elastic</span> constants and Poisson's ratio were predicted from the third order <span class="hlt">elastic</span> constants. Our results could provide a safe guide for promising applications and <span class="hlt">strain</span>-engineering the functions and properties of silicane monolayers. PMID:25190587</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/26961664','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/26961664"><span id="translatedtitle">Lifelong Cyclic Mechanical <span class="hlt">Strain</span> Promotes Large <span class="hlt">Elastic</span> Artery Stiffening: Increased Pulse Pressure and Old Age-Related Organ Failure.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Thorin-Trescases, Nathalie; Thorin, Eric</p> <p>2016-05-01</p> <p>The arterial wall is under a huge mechanical constraint imposed by the cardiac cycle that is bound to generate damage with time. Each heartbeat indeed imposes a pulsatile pressure that generates a vascular stretch. Lifetime accumulation of pulsatile stretches will eventually induce fatigue of the <span class="hlt">elastic</span> large arterial walls, such as aortic and carotid artery walls, promoting their stiffening that will gradually perturb the normal blood flow and local pressure within the organs, and lead to organ failure. The augmented pulse pressure induced by arterial stiffening favours left ventricular hypertrophy because of the repeated extra work against stiff high-pressure arteries, and tissue damage as a result of excessive pulsatile pressure transmitted into the microcirculation, especially in low resistance/high-flow organs such as the brain and kidneys. Vascular aging is therefore characterized by the stiffening of large <span class="hlt">elastic</span> arteries leading to a gradual increase in pulse pressure with age. In this review we focus on the effect of age-related stiffening of large <span class="hlt">elastic</span> arteries. We report the clinical evidence linking arterial stiffness and organ failure and discuss the molecular pathways that are activated by the increase of mechanical stress in the wall. We also discuss the possible interventions that could limit arterial stiffening with age, such as regular aerobic exercise training, and some pharmacological approaches. PMID:26961664</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/663570','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/663570"><span id="translatedtitle">Cyclic material properties tests supporting <span class="hlt">elastic</span>-plastic analysis development</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Hodge, S.C.; Minicucci, J.M.</p> <p>1996-11-01</p> <p>Correlation studies have shown that hardening models currently available in the ABAQUS <span class="hlt">finite</span> element code (isotropic, kinematic) do not accurately capture the inelastic <span class="hlt">strain</span> reversals that occur due to structural rebounding from a rapidly applied transient dynamic load. The purpose of the Cyclic Material properties Test program was to obtain response data for the first several cycles of inelastic <span class="hlt">strain</span> reversal from a cyclic properties test. This data is needed to develop <span class="hlt">elastic</span>-plastic analysis methods that can accurately predict <span class="hlt">strains</span> and permanent sets in structures due to rapidly applied transient dynamic loading. Test specimens were cycled at inelastic <span class="hlt">strain</span> levels typical of rapidly applied transient dynamic analyses (0.5% to 4.0%). In addition to the inelastic response data, cyclic material properties for high yield strength (80 ksi) steel were determined including a cyclic stress-<span class="hlt">strain</span> curve for a stabilized specimen. Two test methods, the Incremental Step method and the Companion specimen Method, were sued to determine cyclic properties. The incrementally decreasing <span class="hlt">strain</span> amplitudes in the first loading block of the Incremental Step method test is representative of the response of structures subjected to rapidly applied transient dynamic loads. The inelastic <span class="hlt">strain</span> history data generated by this test program will be used to support development of a material model that can accurately predict inelastic material behavior including inelastic <span class="hlt">strain</span> reversals. Additionally, this data can be used to verify material model enhancements to <span class="hlt">elastic</span>-plastic <span class="hlt">finite</span> element analysis codes.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=19920000760&hterms=plastic&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D90%26Ntt%3Dplastic','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=19920000760&hterms=plastic&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D90%26Ntt%3Dplastic"><span id="translatedtitle"><span class="hlt">Elastic</span> And Plastic Deformations In Butt Welds</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Verderaime, V.</p> <p>1992-01-01</p> <p>Report presents study of mathematical modeling of stresses and <span class="hlt">strains</span>, reaching beyond limits of <span class="hlt">elasticity</span>, in bars and plates. Study oriented toward development of capability to predict stresses and resulting <span class="hlt">elastic</span> and plastic <span class="hlt">strains</span> in butt welds.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2007AGUFM.G21C0656S&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2007AGUFM.G21C0656S&link_type=ABSTRACT"><span id="translatedtitle">Dislocation Modeling and Comparison With GPS Data to Assess Possible <span class="hlt">Elastic</span> <span class="hlt">Strain</span> Accumulation in the Central Lesser Antilles: New Constraints From the NSF REU Site in Dominica Between 2001 and 2007</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Staisch, L.; Styron, R. H.; James, S.; Turner, H. L.; Ashlock, A.; Cavness, C. L.; Collier, X.; Fauria, K.; Feinstein, R.; Murphy, R.; Williams, B.; Mattioli, G. S.; Jansma, P. E.; Cothren, J.</p> <p>2007-12-01</p> <p>The Caribbean, North and South American plates are converging at a rate of 2 cm/yr in the central region of the Lesser Antilles arc. Here we report high-precision GPS data in concert with forward modeling of a simplified subduction zone geometry to assess <span class="hlt">strain</span> accumulation for the Lesser Antilles trench. We are able to constrain both vertical and horizontal surface deformation from campaign and continuous GPS observations from 28 geodetic benchmarks located in Guadeloupe, Dominica and Aves Island. Precise station positions were estimated with GIPSY-OASIS II using an absolute point positioning strategy and final, precise orbits, clocks, earth orientation parameters, and x-files. All position estimates were updated to ITRF05 and a revised Caribbean Euler pole was used to place our observations in a CAR-fixed frame. Surface displacements for each site were estimated over 2-7 years. CAR-fixed velocities are projected onto a 500 kilometer transect from the LA trench to Aves Island and compared to calculated displacements for 88 different subduction models. <span class="hlt">Finite</span> dislocations within an <span class="hlt">elastic</span> half-space with variable parameters such as angle of the subducting slab, the downdip extent of the locked zone, and percentage of plate interface locking were investigated. Other parameters, such as trench length and slip remained constant. Using a chi-squared, best-fit statistical criterion, the GPS data constrain the subduction interface to a 75 kilometer downdip extent, a 10° dip angle, and near 50% locking. This implies that the subduction zone offshore Dominica is in an interseismic state, thus accumulating <span class="hlt">strain</span> and causing small westward and upward displacement of the Lesser Antilles relative to the stable Caribbean interior.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015MSMSE..23h5014M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015MSMSE..23h5014M"><span id="translatedtitle">On mechanics and material length scales of failure in heterogeneous interfaces using a <span class="hlt">finite</span> <span class="hlt">strain</span> high performance solver</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Mosby, Matthew; Matouš, Karel</p> <p>2015-12-01</p> <p>Three-dimensional simulations capable of resolving the large range of spatial scales, from the failure-zone thickness up to the size of the representative unit cell, in damage mechanics problems of particle reinforced adhesives are presented. We show that resolving this wide range of scales in complex three-dimensional heterogeneous morphologies is essential in order to apprehend fracture characteristics, such as strength, fracture toughness and shape of the softening profile. Moreover, we show that computations that resolve essential physical length scales capture the particle size-effect in fracture toughness, for example. In the vein of image-based computational materials science, we construct statistically optimal unit cells containing hundreds to thousands of particles. We show that these statistically representative unit cells are capable of capturing the first- and second-order probability functions of a given data-source with better accuracy than traditional inclusion packing techniques. In order to accomplish these large computations, we use a parallel multiscale cohesive formulation and extend it to <span class="hlt">finite</span> <span class="hlt">strains</span> including damage mechanics. The high-performance parallel computational framework is executed on up to 1024 processing cores. A mesh convergence and a representative unit cell study are performed. Quantifying the complex damage patterns in simulations consisting of tens of millions of computational cells and millions of highly nonlinear equations requires data-mining the parallel simulations, and we propose two damage metrics to quantify the damage patterns. A detailed study of volume fraction and filler size on the macroscopic traction-separation response of heterogeneous adhesives is presented.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013JMPSo..61..886S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013JMPSo..61..886S"><span id="translatedtitle">Skeleton-and-bubble model of polyether-polyurethane <span class="hlt">elastic</span> open-cell foams for <span class="hlt">finite</span> element analysis at large deformations</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Sabuwala, Tapan; Gioia, Gustavo</p> <p>2013-03-01</p> <p>We formulate a new micromechanical model of <span class="hlt">elastic</span> open-cell (EOC) foams. In this model, the usual skeleton of open-cell foams is supplemented by fitting a thin-walled bubble within each cavity of the skeleton, as a substitute for the membranes that occlude the "windows" of the foam cells in polyether-polyurethane EOC foams. The model has nine parameters; each parameter has a clear geometrical or mechanical significance, and its value may be readily estimated for any given foam. To calibrate the model, we carry out fully nonlinear, three-dimensional <span class="hlt">finite</span>-element simulations of the experiments of Dai et al. (2011a), in which a set of five polyether-polyurethane EOC foams covering a range of commercially available relative densities was tested under compression along the rise direction, compression along a transverse direction, tension along the rise direction, simple shear combined with compression along the rise direction, and hydrostatic pressure combined with compression along the rise direction. We show that, with a suitable choice of the values of the parameters of the model, the model is capable of reproducing the most salient trends evinced in the experimental stress-stretch curves. Yet the model can no longer reproduce all of these trends if the bubbles be excluded from the model, and we conclude that the bubbles play a crucial role at large deformations. We also show that the stretch fields that obtain in our computational simulations are in good accord with the digital-image-correlation (DIC) measurements of Dai et al. For simple shear combined with compression along the rise direction, the DIC measurements of Dai et al. prove insufficient to our purposes, and we carry out DIC measurements of our own. To demonstrate the performance of the model in a typical application of polyether-polyurethane EOC foams, we carry out experiments and simulations of foam specimens loaded through a cylindrical punch and a spherical punch. We conclude the paper with a</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=19950065596&hterms=sequence+analysis+methods&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3Dsequence%2Banalysis%2Bmethods','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=19950065596&hterms=sequence+analysis+methods&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3Dsequence%2Banalysis%2Bmethods"><span id="translatedtitle">P-<span class="hlt">Finite</span>-Element Program For Analysis Of Plates</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Smith, James P.</p> <p>1995-01-01</p> <p>BUCKY is p-<span class="hlt">finite</span>-element computer program for highly accurate analysis of structures. Used to analyze buckling, bending, and in-plane stress-and-<span class="hlt">strain</span> behaviors of plates. Provides <span class="hlt">elastic</span>-plastic solutions for isotropic plates in states of plane stress, and axisymmetric solution sequence used to treat three-dimensional problems. Computes response of plate to variety of loading and boundary conditions by use of higher-order displacement function in p-<span class="hlt">finite</span>-element method. Enables user to obtain results more accurate than obtained by use of traditional h-<span class="hlt">finite</span> elements. Written in FORTRAN 77.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=19850040999&hterms=kinematic+hardening&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3Dkinematic%2Bhardening','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=19850040999&hterms=kinematic+hardening&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3Dkinematic%2Bhardening"><span id="translatedtitle">A simplified method for <span class="hlt">elastic</span>-plastic-creep structural analysis</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Kaufman, A.</p> <p>1985-01-01</p> <p>A simplified inelastic analysis computer program (ANSYPM) was developed for predicting the stress-<span class="hlt">strain</span> history at the critical location of a thermomechanically cycled structure from an <span class="hlt">elastic</span> solution. The program uses an iterative and incremental procedure to estimate the plastic <span class="hlt">strains</span> from the material stress-<span class="hlt">strain</span> properties and a plasticity hardening model. Creep effects are calculated on the basis of stress relaxation at constant <span class="hlt">strain</span>, creep at constant stress or a combination of stress relaxation and creep accumulation. The simplified method was exercised on a number of problems involving uniaxial and multiaxial loading, isothermal and nonisothermal conditions, dwell times at various points in the cycles, different materials and kinematic hardening. Good agreement was found between these analytical results and nonlinear <span class="hlt">finite</span> element solutions for these problems. The simplified analysis program used less than 1 percent of the CPU time required for a nonlinear <span class="hlt">finite</span> element analysis.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19840006474','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19840006474"><span id="translatedtitle">A simplified method for <span class="hlt">elastic</span>-plastic-creep structural analysis</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Kaufman, A.</p> <p>1984-01-01</p> <p>A simplified inelastic analysis computer program (ANSYPM) was developed for predicting the stress-<span class="hlt">strain</span> history at the critical location of a thermomechanically cycled structure from an <span class="hlt">elastic</span> solution. The program uses an iterative and incremental procedure to estimate the plastic <span class="hlt">strains</span> from the material stress-<span class="hlt">strain</span> properties and a plasticity hardening model. Creep effects are calculated on the basis of stress relaxation at constant <span class="hlt">strain</span>, creep at constant stress or a combination of stress relaxation and creep accumulation. The simplified method was exercised on a number of problems involving uniaxial and multiaxial loading, isothermal and nonisothermal conditions, dwell times at various points in the cycles, different materials and kinematic hardening. Good agreement was found between these analytical results and nonlinear <span class="hlt">finite</span> element solutions for these problems. The simplified analysis program used less than 1 percent of the CPU time required for a nonlinear <span class="hlt">finite</span> element analysis.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/330635','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/330635"><span id="translatedtitle"><span class="hlt">Elastic</span>-plastic analysis of the SS-3 tensile specimen</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Majumdar, S.</p> <p>1998-09-01</p> <p>Tensile tests of most irradiated specimens of vanadium alloys are conducted using the miniature SS-3 specimen which is not ASTM approved. Detailed <span class="hlt">elastic</span>-plastic <span class="hlt">finite</span> element analysis of the specimen was conducted to show that, as long as the ultimate to yield strength ratio is less than or equal to 1.25 (which is satisfied by many irradiated materials), the stress-plastic <span class="hlt">strain</span> curve obtained by using such a specimen is representative of the true material behavior.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010PMag...90.1893S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010PMag...90.1893S"><span id="translatedtitle">A formulation for the characteristic lengths of fcc materials in first <span class="hlt">strain</span> gradient <span class="hlt">elasticity</span> via the Sutton-Chen potential</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Shodja, H. M.; Tehranchi, A.</p> <p>2010-05-01</p> <p>The usual continuum theories are inadequate in predicting the mechanical behavior of solids in the presence of small defects and stress concentrators; it is well known that such continuum methods are unable to detect the change of the size of the inhomogeneities and defects. For these reasons various augmented continuum theories and <span class="hlt">strain</span> gradient theories have been proposed in the literature. The major difficulty in implication of these theories lies in the lack of information about the additional material constants which appear in such theories. For fcc metals, for the calculation of the associated characteristic lengths which arise in first <span class="hlt">strain</span> gradient theory, an atomistic approach based on the Sutton-Chen interatomic potential function is proposed. For the validity of the computed characteristic lengths, the phenomenon of the size effect pertinent to a nano-sized circular void within an fcc (111) plane is examined via both first <span class="hlt">strain</span> gradient theory and lattice statics. Comparison of the results explains the physical ramifications of the characteristic lengths in improving the usual continuum results. Moreover, by reconsideration of the Kelvin problem it is shown that a commonly employed variant of the first <span class="hlt">strain</span> gradient theory is only valid for a few fcc metals.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=19860047244&hterms=Continental+Drift&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3D%2528Continental%2BDrift%2529','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=19860047244&hterms=Continental+Drift&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3D%2528Continental%2BDrift%2529"><span id="translatedtitle"><span class="hlt">Finite</span> <span class="hlt">strain</span> calculations of continental deformation. I - Method and general results for convergent zones. II - Comparison with the India-Asia collision zone</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Houseman, G.; England, P.</p> <p>1986-01-01</p> <p>The present investigation has the objective to perform numerical experiments on a rheologically simple continuum model for the continental lithosphere. It is attempted to obtain a better understanding of the dynamics of continental deformation. Calculations are presented of crustal thickness distributions, stress, <span class="hlt">strain</span>, <span class="hlt">strain</span> rate fields, latitudinal displacements, and <span class="hlt">finite</span> rotations, taking into account as basis a model for continental collision which treats the litoshphere as a thin viscous layer subject to indenting boundary conditions. The results of this paper support the conclusions of England and McKenzie (1982) regarding the role of gravity in governing the deformation of a thin viscous layer subject to indenting boundary conditions. The results of the experiments are compared with observations of topography, stress and <span class="hlt">strain</span> rate fields, and palaeomagnetic latitudinal displacements in Asia.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015PhDT........35B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015PhDT........35B"><span id="translatedtitle">A non-contacting approach for full field dynamic <span class="hlt">strain</span> monitoring of rotating structures using the photogrammetry, <span class="hlt">finite</span> element, and modal expansion techniques</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Baqersad, Javad</p> <p></p> <p>Health monitoring of rotating structures such as wind turbines and helicopter rotors is generally performed using conventional sensors that provide a limited set of data at discrete locations near or on the hub. These sensors usually provide no data on the blades or interior locations where failures may occur. Within this work, an unique expansion algorithm was extended and combined with <span class="hlt">finite</span> element (FE) modeling and an optical measurement technique to identify the dynamic <span class="hlt">strain</span> in rotating structures. The merit of the approach is shown by using the approach to predict the dynamic <span class="hlt">strain</span> on a small non-rotating and rotating wind turbine. A three-bladed wind turbine having 2.3-meter long blades was placed in a semi-built-in boundary condition using a hub, a machining chuck, and a steel block. A <span class="hlt">finite</span> element model of the three wind turbine blades assembled to the hub was created and used to extract resonant frequencies and mode shapes. The FE model was validated and updated using experimental modal tests. For the non-rotating optical test, the turbine was excited using a sinusoidal excitation, a pluck test, arbitrary impacts on three blades, and random force excitations with a mechanical shaker. The response of the structure to the excitations was measured using three-dimensional point tracking. A pair of high-speed cameras was used to measure the displacement of optical targets on the structure when the blades were vibrating. The measured displacements at discrete locations were expanded and applied to the <span class="hlt">finite</span> element model of the structure to extract the full-field dynamic <span class="hlt">strain</span>. The results of the work show an excellent correlation between the <span class="hlt">strain</span> predicted using the proposed approach and the <span class="hlt">strain</span> measured with <span class="hlt">strain</span>-gages for all of the three loading conditions. Similar to the non-rotating case, optical measurements were also preformed on a rotating wind turbine. The point tracking technique measured both rigid body displacement and flexible</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li class="active"><span>21</span></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_21 --> <div id="page_22" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li class="active"><span>22</span></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_24");'>24</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="421"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/24882740','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/24882740"><span id="translatedtitle">Predicting surface <span class="hlt">strains</span> at the human distal radius during an in vivo loading task--<span class="hlt">finite</span> element model validation and application.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Bhatia, Varun A; Edwards, W Brent; Troy, Karen L</p> <p>2014-08-22</p> <p>Bone <span class="hlt">strains</span> resulting from physical activity are thought to be a primary driver of bone adaptation, but cannot be directly noninvasively measured. Because bone adapts nonuniformly, physical activity may make an important independent structural contribution to bone strength that is independent of bone mass and density. Our objective was to create and validate methods for subject-specific <span class="hlt">finite</span> element (FE) model generation that would accurately predict the surface <span class="hlt">strains</span> experienced by the distal radius during an in vivo loading task, and to apply these methods to a group of 23 women aged 23-35 to examine variations in <span class="hlt">strain</span>, bone mass and density, and physical activity. Four cadaveric specimens were experimentally tested and specimen-specific FE models were developed to accurately predict periosteal surface <span class="hlt">strains</span> (root mean square error=16.3%). In the living subjects, when 300 N load was simulated, mean <span class="hlt">strains</span> were significantly inversely correlated with BMC (r=-0.893), BMD (r=-0.892) and physical activity level (r=-0.470). Although the group of subjects was relatively homogenous, BMD varied by two-fold (range: 0.19-0.40 g/cm(3)) and mean energy-equivalent <span class="hlt">strain</span> varied by almost six-fold (range: 226.79-1328.41 με) with a simulated 300 N load. In summary, we have validated methods for estimating surface <span class="hlt">strains</span> in the distal radius that occur while leaning onto the palm of the hand. In our subjects, <span class="hlt">strain</span> varied widely across individuals, and was inversely related to bone parameters that can be measured using clinical CT, and inversely related to physical activity history. PMID:24882740</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4248607','PMC'); return false;" href="http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4248607"><span id="translatedtitle">Predicting Surface <span class="hlt">Strains</span> at the Human Distal Radius during an In Vivo Loading Task – <span class="hlt">Finite</span> Element Model Validation and Application</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Bhatia, Varun A.; Edwards, W. Brent; Troy, Karen L.</p> <p>2014-01-01</p> <p>Bone <span class="hlt">strains</span> resulting from physical activity are thought to be a primary driver of bone adaptation, but cannot be directly noninvasively measured. Because bone adapts nonuniformly, physical activity may make an important independent structural contribution to bone strength that is independent of bone mass and density. Our objective was to create and validate methods for subject-specific <span class="hlt">finite</span> element (FE) model generation that would accurately predict the surface <span class="hlt">strains</span> experienced by the distal radius during an in vivo loading task, and to apply these methods to a group of 23 women age 23-35 to examine variations in <span class="hlt">strain</span>, bone mass and density, and physical activity. Four cadaveric specimens were experimentally tested and specimen-specific FE models were developed to accurately predict periosteal surface <span class="hlt">strains</span> (Root mean square error=16.3%). In the living subjects, when a 300 N load was simulated, mean <span class="hlt">strains</span> were significantly inversely correlated with BMC (r=−0.893), BMD (r=−0.892) and physical activity level (r=−0.470). Although the group of subjects was relatively homogenous, BMD varied by two-fold (range: 0.19 – 0.40 g/cm3) and mean energy-equivalent <span class="hlt">strain</span> varied by almost six-fold (range: 226.79 – 1328.41 με) with a simulated 300 N load. In summary, we have validated methods for estimating surface <span class="hlt">strains</span> in the distal radius that occur while leaning onto the palm of the hand. In our subjects, <span class="hlt">strain</span> varied widely across individuals, and was inversely related to bone parameters that can be measured using clinical CT, and inversely related to physical activity history. PMID:24882740</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/pages/biblio/1185571-strain-effects-intermixing-si-surface-importance-long-range-elastic-corrections-first-principles-calculations','SCIGOV-DOEP'); return false;" href="http://www.osti.gov/pages/biblio/1185571-strain-effects-intermixing-si-surface-importance-long-range-elastic-corrections-first-principles-calculations"><span id="translatedtitle"><span class="hlt">Strain</span> effects and intermixing at the Si surface: Importance of long-range <span class="hlt">elastic</span> corrections in first-principles calculations</span></a></p> <p><a target="_blank" href="http://www.osti.gov/pages">DOE PAGESBeta</a></p> <p>Béland, Laurent Karim; Machado-Charry, Eduardo; Pochet, Pascal; Mousseau, Normand</p> <p>2014-10-06</p> <p>Here we investigate Ge mixing at the Si(001) surface and characterize the 2 N Si(001) reconstruction by means of hybrid quantum and molecular mechanics calculations (QM/MM). Avoiding fake <span class="hlt">elastic</span> dampening, this scheme allows to correctly take into account long range deformation induced by reconstructed and defective surfaces. We focus in particular on the dimer vacancy line (DVL) and its interaction with Ge adatoms. We first show that calculated formation energies for these defects are highly dependent on the choice of chemical potential and that the latter must be chosen carefully. Characterizing the effect of the DVL on the deformation field,more » we also find that the DVL favors Ge segregation in the fourth layer close to the DVL. Using the activation-relaxation technique (ART nouveau) and QM/MM, we show that a complex diffusion path permits the substitution of the Ge atom in the fourth layer, with barriers compatible with mixing observed at intermediate temperature. We also show that the use of QM/MM results in much more signi cant corrections at the saddle points (up to 0.5 eV) that at minima, demonstrating its importance for describing kinetics correctly.« less</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/1185571','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/1185571"><span id="translatedtitle"><span class="hlt">Strain</span> effects and intermixing at the Si surface: Importance of long-range <span class="hlt">elastic</span> corrections in first-principles calculations</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Béland, Laurent Karim; Machado-Charry, Eduardo; Pochet, Pascal; Mousseau, Normand</p> <p>2014-10-06</p> <p>Here we investigate Ge mixing at the Si(001) surface and characterize the 2 N Si(001) reconstruction by means of hybrid quantum and molecular mechanics calculations (QM/MM). Avoiding fake <span class="hlt">elastic</span> dampening, this scheme allows to correctly take into account long range deformation induced by reconstructed and defective surfaces. We focus in particular on the dimer vacancy line (DVL) and its interaction with Ge adatoms. We first show that calculated formation energies for these defects are highly dependent on the choice of chemical potential and that the latter must be chosen carefully. Characterizing the effect of the DVL on the deformation field, we also find that the DVL favors Ge segregation in the fourth layer close to the DVL. Using the activation-relaxation technique (ART nouveau) and QM/MM, we show that a complex diffusion path permits the substitution of the Ge atom in the fourth layer, with barriers compatible with mixing observed at intermediate temperature. We also show that the use of QM/MM results in much more signi cant corrections at the saddle points (up to 0.5 eV) that at minima, demonstrating its importance for describing kinetics correctly.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014PhRvB..90o5302B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014PhRvB..90o5302B"><span id="translatedtitle"><span class="hlt">Strain</span> effects and intermixing at the Si surface: Importance of long-range <span class="hlt">elastic</span> corrections in first-principles calculations</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Béland, Laurent Karim; Machado-Charry, Eduardo; Pochet, Pascal; Mousseau, Normand</p> <p>2014-10-01</p> <p>We investigate Ge mixing at the Si(001) surface and characterize the 2×N Si(001) reconstruction by means of hybrid quantum and molecular mechanics calculations (QM/MM). Avoiding fake <span class="hlt">elastic</span> dampening, this scheme allows to correctly take into account long-range deformation induced by reconstructed and defective surfaces. We focus in particular on the dimer vacancy line (DVL) and its interaction with Ge adatoms. We first show that calculated formation energies for these defects are highly dependent on the choice of chemical potential and that the latter must be chosen carefully. Characterizing the effect of the DVL on the deformation field, we also find that the DVL favors Ge segregation in the fourth layer close to the DVL. Using the activation-relaxation technique (ART nouveau) and QM/MM, we show that a complex diffusion path permits the substitution of the Ge atom in the fourth layer, with barriers compatible with mixing observed at intermediate temperature. We also show that the use of QM/MM results in much more significant corrections at the saddle points (up to 0.5 eV) that at minima, demonstrating its importance for describing kinetics correctly.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2015JTAM...45...69L&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2015JTAM...45...69L&link_type=ABSTRACT"><span id="translatedtitle">Propagation of Surface Waves in a Homogeneous Layer of <span class="hlt">Finite</span> Thickness over an Initially Stressed Functionally Graded Magnetic-Electric-<span class="hlt">Elastic</span> Half-Space</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Li, Li; Wei, P. J.</p> <p>2015-03-01</p> <p>The propagation behaviour of Love wave in an initially stressed functionally graded magnetic-electric-<span class="hlt">elastic</span> half-space carrying a homogeneous layer is investigated. The material parameters in the substrate are assumed to vary exponentially along the thickness direction only. The velocity equations of Love wave are derived on the electrically or magnetically open circuit and short circuit boundary conditions, based on the equations of motion of the graded magnetic-electric-<span class="hlt">elastic</span> mate- rial with the initial stresses and the free traction boundary conditions of surface and the continuous boundary conditions of interface. The dispersive curves are obtained numerically and the influences of the initial stresses and the material gradient index on the dispersive curves are dis- cussed. The investigation provides a basis for the development of new functionally graded magneto-electro-<span class="hlt">elastic</span> surface wave devices.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/24121194','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/24121194"><span id="translatedtitle">Hierarchical modelling of in situ <span class="hlt">elastic</span> deformation of human enamel based on photoelastic and diffraction analysis of stresses and <span class="hlt">strains</span>.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Sui, Tan; Lunt, Alexander J G; Baimpas, Nikolaos; Sandholzer, Michael A; Hu, Jianan; Dolbnya, Igor P; Landini, Gabriel; Korsunsky, Alexander M</p> <p>2014-01-01</p> <p>Human enamel is a typical hierarchical mineralized tissue with a two-level composite structure. To date, few studies have focused on how the mechanical behaviour of this tissue is affected by both the rod orientation at the microscale and the preferred orientation of mineral crystallites at the nanoscale. In this study, wide-angle X-ray scattering was used to determine the internal lattice <span class="hlt">strain</span> response of human enamel samples (with differing rod directions) as a function of in situ uniaxial compressive loading. Quantitative stress distribution evaluation in the birefringent mounting epoxy was performed in parallel using photoelastic techniques. The resulting experimental data was analysed using an advanced multiscale Eshelby inclusion model that takes into account the two-level hierarchical structure of human enamel, and reflects the differing rod directions and orientation distributions of hydroxyapatite crystals. The achieved satisfactory agreement between the model and the experimental data, in terms of the values of multidirectional <span class="hlt">strain</span> components under the action of differently orientated loads, suggests that the multiscale approach captures reasonably successfully the structure-property relationship between the hierarchical architecture of human enamel and its response to the applied forces. This novel and systematic approach can be used to improve the interpretation of the mechanical properties of enamel, as well as of the textured hierarchical biomaterials in general. PMID:24121194</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AGUFM.S23E..05V','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AGUFM.S23E..05V"><span id="translatedtitle">Homogenization of Heterogeneous <span class="hlt">Elastic</span> Materials with Applications to Seismic Anisotropy</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Vel, S. S.; Johnson, S. E.; Okaya, D. A.; Cook, A. C.</p> <p>2014-12-01</p> <p>The velocities of seismic waves passing through a complex Earth volume can be influenced by heterogeneities at length scales shorter than the seismic wavelength. As such, seismic wave propagation analyses can be performed by replacing the actual Earth volume by a homogeneous i.e., "effective", <span class="hlt">elastic</span> medium. Homogenization refers to the process by which the <span class="hlt">elastic</span> stiffness tensor of the effective medium is "averaged" from the <span class="hlt">elastic</span> properties, orientations, modal proportions and spatial distributions of the finer heterogeneities. When computing the homogenized properties of a heterogeneous material, the goal is to compute an effective or bulk <span class="hlt">elastic</span> stiffness tensor that relates the average stresses to the average <span class="hlt">strains</span> in the material. Tensor averaging schemes such as the Voigt and Reuss methods are based on certain simplifying assumptions. The Voigt method assumes spatially uniform <span class="hlt">strains</span> while the Reuss method assumes spatially uniform stresses within the heterogeneous material. Although they are both physically unrealistic, they provide upper and lower bounds for the actual homogenized <span class="hlt">elastic</span> stiffness tensor. In order to more precisely determine the homogenized stiffness tensor, the stress and <span class="hlt">strain</span> distributions must be computed by solving the three-dimensional equations of <span class="hlt">elasticity</span> over the heterogeneous region. Asymptotic expansion homogenization (AEH) is one such structure-based approach for the comprehensive micromechanical analysis of heterogeneous materials. Unlike modal volume methods, the AEH method takes into account how geometrical orientation and alignment can increase <span class="hlt">elastic</span> stiffness in certain directions. We use the AEH method in conjunction with <span class="hlt">finite</span> element analysis to calculate the bulk <span class="hlt">elastic</span> stiffnesses of heterogeneous materials. In our presentation, wave speeds computed using the AEH method are compared with those generated using stiffness tensors derived from commonly-used analytical estimates. The method is illustrated</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/15013920','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/15013920"><span id="translatedtitle"><span class="hlt">Elastic</span> Face, An Anatomy-Based Biometrics Beyond Visible Cue</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Tsap, L V; Zhang, Y; Kundu, S J; Goldgof, D B; Sarkar, S</p> <p>2004-03-29</p> <p>This paper describes a face recognition method that is designed based on the consideration of anatomical and biomechanical characteristics of facial tissues. <span class="hlt">Elastic</span> <span class="hlt">strain</span> pattern inferred from face expression can reveal an individual's biometric signature associated with the underlying anatomical structure, and thus has the potential for face recognition. A method based on the continuum mechanics in <span class="hlt">finite</span> element formulation is employed to compute the <span class="hlt">strain</span> pattern. Experiments show very promising results. The proposed method is quite different from other face recognition methods and both its advantages and limitations, as well as future research for improvement are discussed.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/21516726','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/21516726"><span id="translatedtitle">On the material modelling of anisotropy, hardening and failure of sheet metals in the <span class="hlt">finite</span> <span class="hlt">strain</span> regime</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Vladimirov, I. N.; Tini, V.; Kiliclar, Y.; Reese, S.</p> <p>2011-05-04</p> <p>In this paper, we discuss the application of a newly developed coupled material model of <span class="hlt">finite</span> anisotropic multiplicative plasticity and continuum damage to the numerical prediction of the forming limit diagram at fracture (FLDF). The model incorporates Hill-type plastic anisotropy, nonlinear Armstrong-Frederick kinematic hardening and nonlinear isotropic hardening. The numerical examples examine the simulation of forming limit diagrams at fracture by means of the so-called Nakajima stretching test. Comparisons with experimental data for aluminium sheets show a good agreement with the <span class="hlt">finite</span> element results.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=20040086072&hterms=stairs&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D60%26Ntt%3Dstairs','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=20040086072&hterms=stairs&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D60%26Ntt%3Dstairs"><span id="translatedtitle">A Viscoelastic Hybrid Shell <span class="hlt">Finite</span> Element</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Johnson, Arthur</p> <p>1999-01-01</p> <p>An <span class="hlt">elastic</span> large displacement thick-shell hybrid <span class="hlt">finite</span> element is modified to allow for the calculation of viscoelastic stresses. Internal <span class="hlt">strain</span> variables are introduced at he element's stress nodes and are employed to construct a viscous material model. First order ordinary differential equations relate the internal <span class="hlt">strain</span> variables to the corresponding <span class="hlt">elastic</span> <span class="hlt">strains</span> at the stress nodes. The viscous stresses are computed from the internal <span class="hlt">strain</span> variables using viscous moduli which are a fraction of the <span class="hlt">elastic</span> moduli. The energy dissipated by the action of the viscous stresses in included in the mixed variational functional. Nonlinear quasi-static viscous equilibrium equations are then obtained. Previously developed Taylor expansions of the equilibrium equations are modified to include the viscous terms. A predictor-corrector time marching solution algorithm is employed to solve the algebraic-differential equations. The viscous shell element is employed to numerically simulate a stair-step loading and unloading of an aircraft tire in contact with a frictionless surface.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/15004918','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/15004918"><span id="translatedtitle">Mechanistic Constitutive Models for Rubber <span class="hlt">Elasticity</span> and Viscoelasticity</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Puso, M</p> <p>2003-01-21</p> <p>Physically based models which describe the <span class="hlt">finite</span> <span class="hlt">strain</span> behavior of vulcanized rubber are developed. Constitutive laws for <span class="hlt">elasticity</span> and viscoelasticity are derived by integrating over orientation space the forces due to each individual polymer chain. A novel scheme is presented which effectively approximates these integrals in terms of <span class="hlt">strain</span> and <span class="hlt">strain</span> invariants. In addition, the details involving the implementation of such models into a quasi-static large <span class="hlt">strain</span> <span class="hlt">finite</span> element formulation are provided. In order to account for the <span class="hlt">finite</span> extensibility of a molecular chain, Langevin statistics is used to model the chain response. The classical statistical model of rubber assumes that polymer chains interact only at the chemical crosslinks. It is shown that such model when fitted for uniaxial tension data cannot fit compression or equibiaxial data. A model which incorporates the entanglement interactions of surrounding chains, in addition to the <span class="hlt">finite</span> extensibility of the chains, is shown to give better predictions than the classical model. The technique used for approximating the orientation space integral was applied to both the classical and entanglement models. A viscoelasticity model based on the force equilibration process as described by Doi and Edwards is developed. An assumed form for the transient force in the chain is postulated. The resulting stress tensor is composed of an <span class="hlt">elastic</span> and a viscoelastic portion with the <span class="hlt">elastic</span> stress given by the proposed entanglement model. In order to improve the simulation of experimental data, it was found necessary to include the effect of unattached or dangling polymer chains in the viscoelasticity model. The viscoelastic effect of such chains is the manifestation of a disengagement process. This disengagement model for unattached polymer chains motivated an empirical model which was very successful in simulating the experimental results considered.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/22300008','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/22300008"><span id="translatedtitle">Neutron diffraction study on very high <span class="hlt">elastic</span> <span class="hlt">strain</span> of 6% in an Fe{sub 3}Pt under compressive stress</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Yamaguchi, Takashi; Fukuda, Takashi Kakeshita, Tomoyuki; Harjo, Stefanus; Nakamoto, Tatsushi</p> <p>2014-06-09</p> <p>An Fe{sub 3}Pt alloy with degree of order 0.75 exhibits a second-order-like martensitic transformation from a cubic structure to a tetragonal one at about 90 K; its tetragonality c/a changes nearly continuously from 1 to 0.945 on cooling from 90 K to 14 K. We have investigated the change in lattice parameters in a single crystal of the Fe{sub 3}Pt alloy at 93 K under compressive stresses, σ, applied in the [001] direction by neutron diffraction. The tetragonality c/a has decreased continuously from 1 to 0.907 with an increase in |σ| up to |σ| = 280 MPa; the corresponding lattice <span class="hlt">strain</span> in the [001] direction, due to the continuous structure change, increases from 0% to 6.1%. When the stress of 300 MPa is reached, c/a has changed abruptly from 0.907 to 0.789 due to a first-order martensitic transformation.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/1235302','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/1235302"><span id="translatedtitle">Indentation-derived <span class="hlt">elastic</span> modulus of multilayer thin films: Effect of unloading induced plasticity</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Jamison, Ryan Dale; Shen, Yu -Lin</p> <p>2015-08-13</p> <p>Nanoindentation is useful for evaluating the mechanical properties, such as <span class="hlt">elastic</span> modulus, of multilayer thin film materials. A fundamental assumption in the derivation of the <span class="hlt">elastic</span> modulus from nanoindentation is that the unloading process is purely <span class="hlt">elastic</span>. In this work, the validity of <span class="hlt">elastic</span> assumption as it applies to multilayer thin films is studied using the <span class="hlt">finite</span> element method. The <span class="hlt">elastic</span> modulus and hardness from the model system are compared to experimental results to show validity of the model. Plastic <span class="hlt">strain</span> is shown to increase in the multilayer system during the unloading process. Additionally, the indentation-derived modulus of a monolayer material shows no dependence on unloading plasticity while the modulus of the multilayer system is dependent on unloading-induced plasticity. Lastly, the cyclic behavior of the multilayer thin film is studied in relation to the influence of unloading-induced plasticity. Furthermore, it is found that several cycles are required to minimize unloading-induced plasticity.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/17200819','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/17200819"><span id="translatedtitle">On the measurement of human osteosarcoma cell <span class="hlt">elastic</span> modulus using shear assay experiments.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Cao, Yifang; Bly, Randy; Moore, Will; Gao, Zhan; Cuitino, Alberto M; Soboyejo, Wole</p> <p>2007-01-01</p> <p>This paper presents a method for determining the <span class="hlt">elastic</span> modulus of human osteosarcoma (HOS) cells. The method involves a combination of shear assay experiments and <span class="hlt">finite</span> element analysis. Following in-situ observations of cell deformation during shear assay experiments, a digital image correlation (DIC) technique was used to determine the local displacement and <span class="hlt">strain</span> fields. <span class="hlt">Finite</span> element analysis was then used to determine the Young's moduli of HOS cells. This involved a match of the maximum shear stresses estimated from the experimental shear assay measurements and those calculated from <span class="hlt">finite</span> element simulations. PMID:17200819</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/5215465','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/5215465"><span id="translatedtitle">Comparison of stress distributions in a simple tubular joint using 3-D <span class="hlt">finite</span> element, photoelastic and <span class="hlt">strain</span> gauge techniques</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Fessler, H.; Edwards, C.D.</p> <p>1983-05-01</p> <p>Combined strip and rosette gauge measurements and results from three-dimensional, <span class="hlt">finite</span> element calculations are in excellent agreement with frozen stress photoelastic results for an efficient shape of cast-steel node under axial, brace loading. Three different meshes showed that two layers of elements through the thickness are needed.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/25934322','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/25934322"><span id="translatedtitle">Micromechanical poroelastic <span class="hlt">finite</span> element and shear-lag models of tendon predict large <span class="hlt">strain</span> dependent Poisson's ratios and fluid expulsion under tensile loading.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Ahmadzadeh, Hossein; Freedman, Benjamin R; Connizzo, Brianne K; Soslowsky, Louis J; Shenoy, Vivek B</p> <p>2015-08-01</p> <p>As tendons are loaded, they reduce in volume and exude fluid to the surrounding medium. Experimental studies have shown that tendon stretching results in a Poisson's ratio greater than 0.5, with a maximum value at small <span class="hlt">strains</span> followed by a nonlinear decay. Here we present a computational model that attributes this macroscopic observation to the microscopic mechanism of the load transfer between fibrils under stretch. We develop a <span class="hlt">finite</span> element model based on the mechanical role of the interfibrillar-linking elements, such as thin fibrils that bridge the aligned fibrils or macromolecules such as glycosaminoglycans (GAGs) in the interfibrillar sliding and verify it with a theoretical shear-lag model. We showed the existence of a previously unappreciated structure-function mechanism whereby the Poisson's ratio in tendon is affected by the <span class="hlt">strain</span> applied and interfibrillar-linker properties, and together these features predict tendon volume shrinkage under tensile loading. During loading, the interfibrillar-linkers pulled fibrils toward each other and squeezed the matrix, leading to the Poisson's ratio larger than 0.5 and fluid expulsion. In addition, the rotation of the interfibrillar-linkers with respect to the fibrils at large <span class="hlt">strains</span> caused a reduction in the volume shrinkage and eventual nonlinear decay in Poisson's ratio at large <span class="hlt">strains</span>. Our model also predicts a fluid flow that has a radial pattern toward the surrounding medium, with the larger fluid velocities in proportion to the interfibrillar sliding. PMID:25934322</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014JMPSo..64..396O','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014JMPSo..64..396O"><span id="translatedtitle">A <span class="hlt">finite</span> <span class="hlt">strain</span> thermo-viscoelastic constitutive model to describe the self-heating in elastomeric materials during low-cycle fatigue</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ovalle Rodas, C.; Zaïri, F.; Naït-Abdelaziz, M.</p> <p>2014-03-01</p> <p>A thermo-visco-hyperelastic constitutive model, in accordance with the second thermodynamics principle, is formulated to describe the self-heating evolution in elastomeric materials under cyclic loading. The mechanical part of the model is based upon a Zener rheological representation in which the specific free energy potential is dependent on an added internal variable, allowing the description of the time-dependent mechanical response. The large <span class="hlt">strain</span> mechanical behavior is described using a Langevin spring, while the continuous stress-softening under cyclic loading is taken into account by means of a network alteration kinetics. The thermo-mechanical coupling is defined by postulating the existence of a dissipation pseudo-potential, function of the viscous dilatation tensor. The proposed model is fully three-dimensional and is implemented into a <span class="hlt">finite</span> element code. The model parameters are identified using experimental data obtained on a styrene-butadiene rubber under a given <span class="hlt">strain</span> rate for different <span class="hlt">strain</span> conditions. Predicted evolutions given by the model for other <span class="hlt">strain</span> rates are found in good agreement with the experimental data.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2008JSASS..56..566N','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2008JSASS..56..566N"><span id="translatedtitle">Inverse Analysis of Distributed Load Using <span class="hlt">Strain</span> Data</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Nakamura, Toshiya; Igawa, Hirotaka</p> <p></p> <p>The operational stress data is quite useful in managing the structural integrity and airworthiness of an aircraft. Since the aerodynamic load (pressure) distributes continuously on the structure surface, identifying the load from <span class="hlt">finite</span> number of measured <span class="hlt">strain</span> data is not easy. Although this is an inverse problem, usually used is an empirical correlation between load and <span class="hlt">strain</span> obtained through expensive ground tests. Some analytical studies have been conducted but simple mathematical expressions were assumed to approximate the pressure distribution. In the present study a more flexible approximation of continuous load distribution is proposed. The pressure distribution is identified based on <span class="hlt">finite</span> number of <span class="hlt">strain</span> data with using the conventional <span class="hlt">finite</span> element method and pseudo-inverse matrix. Also an extension is made by coupling an aerodynamical restriction with the <span class="hlt">elastic</span> equation. Numerical examples show that this extension improves the precision of the inverse analysis with very small number of <span class="hlt">strain</span> data.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2008IJMPB..22.1165M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2008IJMPB..22.1165M"><span id="translatedtitle">Effects of <span class="hlt">Strain</span> Rate Dependency of Material Properties in Low Velocity Impact</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Minamoto, Hirofumi; Seifried, Robert; Eberhard, Peter; Kawamura, Shozo</p> <p></p> <p>Impact processes are often analyzed using the coefficient of restitution which represents the kinetic energy loss during impact. In this paper the effect of <span class="hlt">strain</span> rate dependency of the yield stress on the coefficient of restitution is investigated experimentally and numerically for the impact of a steel sphere against a steel rod. <span class="hlt">Finite</span> Element simulations using <span class="hlt">strain</span>-rate dependent material behavior are carried out. In addition, <span class="hlt">Finite</span> Element simulations with <span class="hlt">elastic</span>-plastic material behavior, which ignore the <span class="hlt">strain</span> rate dependency, are carried out as well as <span class="hlt">elastic</span> material behavior. Comparisons between the experiments and the simulations using <span class="hlt">strain</span>-rate dependent material behavior show good agreement, and also prove the strong dependency of the coefficient of restitution on the <span class="hlt">strain</span> rate dependency of the yield stress for steel. The results from both, the experiments and the simulations show also the strong influence of the wave propagation in the rod on the coefficient of restitution.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li class="active"><span>22</span></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_24");'>24</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_22 --> <div id="page_23" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li class="active"><span>23</span></li> <li><a href="#" onclick='return showDiv("page_24");'>24</a></li> <li><a href="#" onclick='return showDiv("page_25");'>25</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="441"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/20545537','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/20545537"><span id="translatedtitle">Stress and <span class="hlt">strain</span> analysis of the bone-implant interface: a comparison of fiber-reinforced composite and titanium implants utilizing 3-dimensional <span class="hlt">finite</span> element study.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Shinya, Akikazu; Ballo, Ahmed M; Lassila, Lippo V J; Shinya, Akiyoshi; Närhi, Timo O; Vallittu, Pekka K</p> <p>2011-03-01</p> <p>This study analyzed stress and <span class="hlt">strain</span> mediated by 2 different implant materials, titanium (Ti) and experimental fiber-reinforced composite (FRC), on the implant and on the bone tissue surrounding the implant. Three-dimensional <span class="hlt">finite</span> element models constructed from a mandibular bone and an implant were subjected to a load of 50 N in vertical and horizontal directions. Postprocessing files allowed the calculation of stress and <span class="hlt">strain</span> within the implant materials and stresses at the bone-to-implant interface (stress path). Maximum stress concentrations were located around the implant on the rim of the cortical bone in both implant materials; Ti and overall stresses decreased toward the Ti implant apex. In the FRC implant, a stress value of 0.6 to 2.0 MPa was detected not only on the screw threads but also on the implant surface between the threads. Clear differences were observed in the <span class="hlt">strain</span> distribution between the materials. Based on the results, the vertical load stress range of the FRC implant was close to the stress level for optimal bone growth. Furthermore, the stress at the bone around the FRC implant was more evenly distributed than that with Ti implant. PMID:20545537</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19800024255','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19800024255"><span id="translatedtitle">Computational strategy for the solution of large <span class="hlt">strain</span> nonlinear problems using the Wilkins explicit <span class="hlt">finite</span>-difference approach</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Hofmann, R.</p> <p>1980-01-01</p> <p>The STEALTH code system, which solves large <span class="hlt">strain</span>, nonlinear continuum mechanics problems, was rigorously structured in both overall design and programming standards. The design is based on the theoretical elements of analysis while the programming standards attempt to establish a parallelism between physical theory, programming structure, and documentation. These features have made it easy to maintain, modify, and transport the codes. It has also guaranteed users a high level of quality control and quality assurance.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=19890035817&hterms=cantilever&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3Dcantilever','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=19890035817&hterms=cantilever&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3Dcantilever"><span id="translatedtitle">Three-dimensional <span class="hlt">elastic</span> analysis of a composite double cantilever beam specimen</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Raju, I. S.; Shivakumar, K. N.; Crews, J. H., Jr.</p> <p>1988-01-01</p> <p>Attention is given to the stresses and the <span class="hlt">strain</span> energy release rate along the delamination front in the present three-dimensional <span class="hlt">elastic</span> analysis of a 24-ply, cocured double-cantilever beam specimen by means of 20-noded parabolic-isoparametric <span class="hlt">finite</span> elements. At the free surface, the <span class="hlt">strain</span> energy release rate was found to be substantially smaller than the plane <span class="hlt">strain</span> value; this is suggested to be due to the free-surface effect that exists where the delamination meets the surface edge.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016GeoJI.205.1532H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016GeoJI.205.1532H"><span id="translatedtitle">An error analysis of higher-order <span class="hlt">finite</span>-element methods: effect of degenerate coupling on simulation of <span class="hlt">elastic</span> wave propagation</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Hasegawa, Kei; Geller, Robert J.; Hirabayashi, Nobuyasu</p> <p>2016-06-01</p> <p>We present a theoretical analysis of the error of synthetic seismograms computed by higher-order <span class="hlt">finite</span>-element methods (ho-FEMs). We show the existence of a previously unrecognized type of error due to degenerate coupling between waves with the same frequency but different wavenumbers. These results are confirmed by simple numerical experiments using the spectral element method as an example of ho-FEMs. Errors of the type found by this study may occur generally in applications of ho-FEMs.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/pages/biblio/1324261-finite-element-model-brittle-fracture-fragmentation','SCIGOV-DOEP'); return false;" href="http://www.osti.gov/pages/biblio/1324261-finite-element-model-brittle-fracture-fragmentation"><span id="translatedtitle"><span class="hlt">Finite</span> element model for brittle fracture and fragmentation</span></a></p> <p><a target="_blank" href="http://www.osti.gov/pages">DOE PAGESBeta</a></p> <p>Li, Wei; Delaney, Tristan J.; Jiao, Xiangmin; Samulyak, Roman; Lu, Cao</p> <p>2016-06-01</p> <p>A new computational model for brittle fracture and fragmentation has been developed based on <span class="hlt">finite</span> element analysis of non-linear <span class="hlt">elasticity</span> equations. The proposed model propagates the cracks by splitting the mesh nodes alongside the most over-<span class="hlt">strained</span> edges based on the principal direction of <span class="hlt">strain</span> tensor. To prevent elements from overlapping and folding under large deformations, robust geometrical constraints using the method of Lagrange multipliers have been incorporated. In conclusion, the model has been applied to 2D simulations of the formation and propagation of cracks in brittle materials, and the fracture and fragmentation of stretched and compressed materials.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/548454','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/548454"><span id="translatedtitle">Vortex induced <span class="hlt">strain</span> effects in anisotropic superconductors</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Miranovic, P.; Dobrosavljevic-Grujic, L.; Kogan, V.G.</p> <p>1996-12-31</p> <p><span class="hlt">Strain</span> in a superconductor, produced by the normal vortex core, can affect both static and dynamic properties of vortices. It causes an additional vortex-vortex interaction which is long-ranged ({approximately} 1/r{sup 2}) as compared with <span class="hlt">finite</span> but much stronger London interaction in the fields far below H{sub c2}. The energy of this magneto-<span class="hlt">elastic</span> interaction is calculated within London model. The role of <span class="hlt">strain</span> effects in forming vortex lattice structure is demonstrated for YBa{sub 2}Cu{sub 3}O{sub 7}.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/645502','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/645502"><span id="translatedtitle"><span class="hlt">Elastic</span>-plastic failure analysis of pressure burst tests of thin toroidal shells</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Jones, D.P.; Holliday, J.E.; Larson, L.D.</p> <p>1998-07-01</p> <p>This paper provides a comparison between test and analysis results for bursting of thin toroidal shells. Testing was done by pressurizing two toroidal shells until failure by bursting. An analytical criterion for bursting is developed based on good agreement between structural instability predicted by large <span class="hlt">strain</span>-large displacement <span class="hlt">elastic</span>-plastic <span class="hlt">finite</span> element analysis and observed burst pressure obtained from test. The failures were characterized by loss of local stability of the membrane section of the shells consistent with the predictions from the <span class="hlt">finite</span> element analysis. Good agreement between measured and predicted burst pressure suggests that incipient structural instability as calculated by an <span class="hlt">elastic</span>-plastic <span class="hlt">finite</span> element analysis is a reasonable way to calculate the bursting pressure of thin membrane structures.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://eric.ed.gov/?q=boyles+AND+law&pg=3&id=EJ054997','ERIC'); return false;" href="http://eric.ed.gov/?q=boyles+AND+law&pg=3&id=EJ054997"><span id="translatedtitle">The First Law of <span class="hlt">Elasticity</span></span></a></p> <p><a target="_blank" href="http://www.eric.ed.gov/ERICWebPortal/search/extended.jsp?_pageLabel=advanced">ERIC Educational Resources Information Center</a></p> <p>Girill, T. R.</p> <p>1972-01-01</p> <p>The Boyle-Mariotte gas law was formulated in terms of pneumatic springs," subsumed by Hooke under his own stress-<span class="hlt">strain</span> relation, and generally regarded as a law of <span class="hlt">elasticity</span>. The subsequent development of Boyle's principle and <span class="hlt">elasticity</span> provide thought-provoking test cases for Kuhn's notations of paradigm and puzzle solving in physics.…</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/27159017','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/27159017"><span id="translatedtitle">An <span class="hlt">elastic</span> second skin.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Yu, Betty; Kang, Soo-Young; Akthakul, Ariya; Ramadurai, Nithin; Pilkenton, Morgan; Patel, Alpesh; Nashat, Amir; Anderson, Daniel G; Sakamoto, Fernanda H; Gilchrest, Barbara A; Anderson, R Rox; Langer, Robert</p> <p>2016-08-01</p> <p>We report the synthesis and application of an <span class="hlt">elastic</span>, wearable crosslinked polymer layer (XPL) that mimics the properties of normal, youthful skin. XPL is made of a tunable polysiloxane-based material that can be engineered with specific <span class="hlt">elasticity</span>, contractility, adhesion, tensile strength and occlusivity. XPL can be topically applied, rapidly curing at the skin interface without the need for heat- or light-mediated activation. In a pilot human study, we examined the performance of a prototype XPL that has a tensile modulus matching normal skin responses at low <span class="hlt">strain</span> (<40%), and that withstands elongations exceeding 250%, <span class="hlt">elastically</span> recoiling with minimal <span class="hlt">strain</span>-energy loss on repeated deformation. The application of XPL to the herniated lower eyelid fat pads of 12 subjects resulted in an average 2-grade decrease in herniation appearance in a 5-point severity scale. The XPL platform may offer advanced solutions to compromised skin barrier function, pharmaceutical delivery and wound dressings. PMID:27159017</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2016NatMa..15..911Y&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2016NatMa..15..911Y&link_type=ABSTRACT"><span id="translatedtitle">An <span class="hlt">elastic</span> second skin</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Yu, Betty; Kang, Soo-Young; Akthakul, Ariya; Ramadurai, Nithin; Pilkenton, Morgan; Patel, Alpesh; Nashat, Amir; Anderson, Daniel G.; Sakamoto, Fernanda H.; Gilchrest, Barbara A.; Anderson, R. Rox; Langer, Robert</p> <p>2016-08-01</p> <p>We report the synthesis and application of an <span class="hlt">elastic</span>, wearable crosslinked polymer layer (XPL) that mimics the properties of normal, youthful skin. XPL is made of a tunable polysiloxane-based material that can be engineered with specific <span class="hlt">elasticity</span>, contractility, adhesion, tensile strength and occlusivity. XPL can be topically applied, rapidly curing at the skin interface without the need for heat- or light-mediated activation. In a pilot human study, we examined the performance of a prototype XPL that has a tensile modulus matching normal skin responses at low <span class="hlt">strain</span> (<40%), and that withstands elongations exceeding 250%, <span class="hlt">elastically</span> recoiling with minimal <span class="hlt">strain</span>-energy loss on repeated deformation. The application of XPL to the herniated lower eyelid fat pads of 12 subjects resulted in an average 2-grade decrease in herniation appearance in a 5-point severity scale. The XPL platform may offer advanced solutions to compromised skin barrier function, pharmaceutical delivery and wound dressings.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015CompM..55...37Z','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015CompM..55...37Z"><span id="translatedtitle">Multiscale modeling of the effect of the interfacial transition zone on the modulus of <span class="hlt">elasticity</span> of fiber-reinforced fine concrete</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Zhang, J. L.; Liu, X.; Yuan, Y.; Mang, H. A.</p> <p>2015-01-01</p> <p>A multiscale model of fiber-reinforced fine concrete is developed, with special emphasis on the interfacial transition zone (ITZ). It does not only allow the prediction of the modulus of <span class="hlt">elasticity</span> but also permits the determination of the <span class="hlt">strain</span> and stress field. The model is based on the mathematical homogenization method and implemented in the frame of the <span class="hlt">finite</span> element method. A comparison of model predictions with experimental results taken from the literature validates the model's effectiveness for prediction of the <span class="hlt">elasticity</span> modulus. The effect of the thickness and of the <span class="hlt">elasticity</span> modulus of the ITZ on the <span class="hlt">elasticity</span> modulus of the homogenized material as well as the influence of the strength of the ITZ on the <span class="hlt">elastic</span> limit of the homogenized material, are investigated numerically. Furthermore, a sensitivity analysis is carried out to evaluate the influence of fine-scale factors on the <span class="hlt">elasticity</span> modulus of ultra-high performance concrete.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19960028587','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19960028587"><span id="translatedtitle">A viscoelastic higher-order beam <span class="hlt">finite</span> element</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Johnson, Arthur R.; Tressler, Alexander</p> <p>1996-01-01</p> <p>A viscoelastic internal variable constitutive theory is applied to a higher-order <span class="hlt">elastic</span> beam theory and <span class="hlt">finite</span> element formulation. The behavior of the viscous material in the beam is approximately modeled as a Maxwell solid. The <span class="hlt">finite</span> element formulation requires additional sets of nodal variables for each relaxation time constant needed by the Maxwell solid. Recent developments in modeling viscoelastic material behavior with <span class="hlt">strain</span> variables that are conjugate to the <span class="hlt">elastic</span> <span class="hlt">strain</span> measures are combined with advances in modeling through-the-thickness stresses and <span class="hlt">strains</span> in thick beams. The result is a viscous thick-beam <span class="hlt">finite</span> element that possesses superior characteristics for transient analysis since its nodal viscous forces are not linearly dependent an the nodal velocities, which is the case when damping matrices are used. Instead, the nodal viscous forces are directly dependent on the material's relaxation spectrum and the history of the nodal variables through a differential form of the constitutive law for a Maxwell solid. The thick beam quasistatic analysis is explored herein as a first step towards developing more complex viscoelastic models for thick plates and shells, and for dynamic analyses. The internal variable constitutive theory is derived directly from the Boltzmann superposition theorem. The mechanical <span class="hlt">strains</span> and the conjugate internal <span class="hlt">strains</span> are shown to be related through a system of first-order, ordinary differential equations. The total time-dependent stress is the superposition of its <span class="hlt">elastic</span> and viscous components. Equations of motion for the solid are derived from the virtual work principle using the total time-dependent stress. Numerical examples for the problems of relaxation, creep, and cyclic creep are carried out for a beam made from an orthotropic Maxwell solid.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19800025285','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19800025285"><span id="translatedtitle"><span class="hlt">Elastic</span>-plastic analysis using a triangular ring element in NASTRAN</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Chen, P. C. T.</p> <p>1980-01-01</p> <p>An <span class="hlt">elastic</span> plastic triangular ring element is implemented in NASTRAN computer program. The plane <span class="hlt">strain</span> problem of partially plastic thick walled cylinder under internal pressure is solved and compared with the earlier <span class="hlt">finite</span> difference solution. A very good agreement has been reached. In order to demonstrate its application to more general problems, an overloaded thread problem for the British Standard Buttress is examined. The maximum axial and principal stresses are located and their values are determined as functions of loadings.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4961073','PMC'); return false;" href="http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4961073"><span id="translatedtitle">Evaluation of a pulsed phase-locked loop system for noninvasive tracking of bone deformation under loading with <span class="hlt">finite</span> element and <span class="hlt">strain</span> analysis</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Serra-Hsu, Frederick; Cheng, Jiqi; Lynch, Ted</p> <p>2016-01-01</p> <p>Ultrasound has been widely used to nondestructively evaluate various materials, including biological tissues. Quantitative ultrasound has been used to assess bone quality and fracture risk. A pulsed phase-locked loop (PPLL) method has been proven for very sensitive tracking of ultrasound time-of-flight (TOF) changes. The objective of this work was to determine if the PPLL TOF tracking is sensitive to bone deformation changes during loading. The ability to noninvasively detect bone deformations has many implications, including assessment of bone strength and more accurate osteoporosis diagnostics and fracture risk prediction using a measure of bone mechanical quality. Fresh sheep femur cortical bone shell samples were instrumented with three 3-element rosette <span class="hlt">strain</span> gauges and then tested under mechanical compression with eight loading levels using an MTS machine. Samples were divided into two groups based on internal marrow cavity content: with original marrow, or replaced with water. During compressive loading ultrasound waves were measured through acoustic transmission across the mid-diaphysis of bone. <span class="hlt">Finite</span> element analysis (FEA) was used to describe ultrasound propagation path length changes under loading based on μCT-determined bone geometry. The results indicated that PPLL output correlates well to measured axial <span class="hlt">strain</span>, with R2 values of 0.70 ± 0.27 and 0.62 ± 0.29 for the marrow and water groups, respectively. The PPLL output correlates better with the ultrasound path length changes extracted from FEA. For the two validated FEA tests, correlation was improved to R2 = 0.993 and R2 = 0.879 through cortical path, from 0.815 and 0.794 via marrow path, respectively. This study shows that PPLL readings are sensitive to displacement changes during external bone loading, which may have potential to noninvasively assess bone <span class="hlt">strain</span> and tissue mechanical properties. PMID:21765205</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=19720053509&hterms=Singularity&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D90%26Ntt%3DSingularity%2Bnear','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=19720053509&hterms=Singularity&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D90%26Ntt%3DSingularity%2Bnear"><span id="translatedtitle">Wave-front singularities for two-dimensional anisotropic <span class="hlt">elastic</span> waves.</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Payton, R. G.</p> <p>1972-01-01</p> <p>Wavefront singularities for the displacement functions, associated with the radiation of linear <span class="hlt">elastic</span> waves from a point source embedded in a <span class="hlt">finitely</span> <span class="hlt">strained</span> two-dimensional <span class="hlt">elastic</span> solid, are examined in detail. It is found that generally the singularities are of order d to the -1/2 power, where d measures distance away from the front. However, in certain exceptional cases singularities of order d to the -n power, where n = 1/4, 2/3, 3/4, may be encountered.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19800016162','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19800016162"><span id="translatedtitle">Implementation of a trapezoidal ring element in NASTRAN for <span class="hlt">elastic</span>-plastic analysis</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Chen, P. C. T.; Ohara, G. P.</p> <p>1980-01-01</p> <p>The explicit expressions for an <span class="hlt">elastic</span>-plastic trapezoidal ring element are presented and implemented in NASTRAN computer program. The material is assumed to obey the von Mises' yield criterion, isotropic hardening rule and the Prandtl-Reuss flow relations. For the purpose of demonstration, two <span class="hlt">elastic</span>-plastic problems are solved and compared with previous results. The first is a plane-<span class="hlt">strain</span> tube under uniform internal pressure and the second, a <span class="hlt">finite</span>-length tube loaded over part of its inner surface. A very good agreement was found in both test problems.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/23796430','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/23796430"><span id="translatedtitle">Material property discontinuities in intervertebral disc porohyperelastic <span class="hlt">finite</span> element models generate numerical instabilities due to volumetric <span class="hlt">strain</span> variations.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Ruiz, C; Noailly, J; Lacroix, D</p> <p>2013-10-01</p> <p>Numerical studies of the intervertebral disc (IVD) are important to better understand the load transfer and the mechanobiological processes within the disc. Among the relevant calculations, fluid-related outputs are critical to describe and explore accurately the tissue properties. Porohyperelastic <span class="hlt">finite</span> element models of IVD can describe accurately the disc behaviour at the organ level and allow the inclusion of fluid effects. However, results may be affected by numerical instabilities when fast load rates are applied. We hypothesized that such instabilities would appear preferentially at material discontinuities such as the annulus-nucleus boundary and should be considered when testing mesh convergence. A L4-L5 IVD model including the nucleus, annulus and cartilage endplates were tested under pure rotational loads, with different levels of mesh refinement. The effect of load relaxation and swelling were also studied. Simulations indicated that fluid velocity oscillations appeared due to numerical instability of the pore pressure spatial derivative at material discontinuities. Applying local refinement only was not enough to eliminate these oscillations. In fact, mesh refinements had to be local, material-dependent, and supplemented by the creation of a material transition zone, including interpolated material properties. Results also indicated that oscillations vanished along load relaxation, and faster attenuation occurred with the incorporation of the osmotic pressure. We concluded that material discontinuities are a major cause of instability for poromechanical calculations in multi-tissue models when load velocities are simulated. A strategy was presented to address these instabilities and recommendations on the use of IVD porohyperelastic models were given. PMID:23796430</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3312381','PMC'); return false;" href="http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3312381"><span id="translatedtitle">EQUIVALENCE BETWEEN SHORT-TIME BIPHASIC AND INCOMPRESSIBLE <span class="hlt">ELASTIC</span> MATERIAL RESPONSES</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Ateshian, Gerard A.; Ellis, Benjamin J.; Weiss, Jeffrey A.</p> <p>2009-01-01</p> <p>Porous-permeable tissues have often been modeled using porous media theories such as the biphasic theory. This study examines the equivalence of the short-time biphasic and incompressible <span class="hlt">elastic</span> responses for arbitrary deformations and constitutive relations from first principles. This equivalence is illustrated in problems of unconfined compression of a disk, and of articular contact under <span class="hlt">finite</span> deformation, using two different constitutive relations for the solid matrix of cartilage, one of which accounts for the large disparity observed between the tensile and compressive moduli in this tissue. Demonstrating this equivalence under general conditions provides a rationale for using available <span class="hlt">finite</span> element codes for incompressible <span class="hlt">elastic</span> materials as a practical substitute for biphasic analyses, so long as only the short-time biphasic response is sought. In practice, an incompressible <span class="hlt">elastic</span> analysis is representative of a biphasic analysis over the short-term response δt≪Δ2/‖C4‖||K||, where Δ is a characteristic dimension, C4 is the <span class="hlt">elasticity</span> tensor and K is the hydraulic permeability tensor of the solid matrix. Certain notes of caution are provided with regard to implementation issues, particularly when <span class="hlt">finite</span> element formulations of incompressible <span class="hlt">elasticity</span> employ an uncoupled <span class="hlt">strain</span> energy function consisting of additive deviatoric and volumetric components. PMID:17536908</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2015AGUFM.T43E..02C&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2015AGUFM.T43E..02C&link_type=ABSTRACT"><span id="translatedtitle">Secular Variation in the Storage and Dissipation of <span class="hlt">Elastic</span> <span class="hlt">Strain</span> Energy Along the Central Altyn Tagh Fault (86-88.5°E), NW China</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Cowgill, E.; Gold, R. D.; Arrowsmith, R.; Friedrich, A. M.</p> <p>2015-12-01</p> <p>In <span class="hlt">elastic</span> rebound theory, hazard increases as interseismic <span class="hlt">strain</span> rebuilds after rupture. This model is challenged by the temporal variation in the pacing of major earthquakes that is both predicted by mechanical models and suggested by some long paleoseismic records (e.g., 1-3). However, the extent of such behavior remains unclear due to a lack of long (5-25 ky) records of fault slip. Using Monte Carlo analysis of 11 offset landforms, we determined a 16-ky record of fault slip for the active, left-lateral Altyn Tagh fault, which bounds the NW margin of the Tibetan Plateau. This history reveals a pulse of accelerated slip between 6.4 and 6.0 ka, during which the fault slipped 9 +14/-2 m at a rate of 23 +35/-5 mm/y, or ~3x the 16 ky average of 8.1 +1.2/-0.9mm/y. These two modes of earthquake behavior suggest temporal variation in the rates of stress storage and release. The simplest explanation for the pulse is a cluster of 2-8 Mw > 7.5 earthquakes. Such supercyclicity has been reported for the Sunda (4) and Cascadia (3) megathrusts, but contrasts with steady slip along the strike-slip Alpine fault (5), for example. A second possibility is that the pulse reflects a single, unusually large rupture. However, this Black Swan event is unlikely: empirical scaling relationships require a Mw 8.2 rupture of the entire 1200-km-long ATF to produce 7 m of average slip. Likewise, Coulomb stress change from rupture on the adjacent North Altyn fault is of modest magnitude and overlap with the ATF. Poor temporal correlation between precipitation and the slip pulse argues against climatically modulated changes in surface loading (lakes/ice) or pore-fluid pressure. "Paleoslip" studies such as this sacrifice the single-event resolution of paleoseismology in exchange for long records that quantify both the timing and magnitude of fault slip averaged over multiple ruptures, and are essential for documenting temporal variations in fault slip as we begin to use calibrated physical</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20050181988','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20050181988"><span id="translatedtitle">Nonlinear Visco-<span class="hlt">Elastic</span> Response of Composites via Micro-Mechanical Models</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Gates, Thomas S.; Sridharan, Srinivasan</p> <p>2005-01-01</p> <p>Micro-mechanical models for a study of nonlinear visco-<span class="hlt">elastic</span> response of composite laminae are developed and their performance compared. A single integral constitutive law proposed by Schapery and subsequently generalized to multi-axial states of stress is utilized in the study for the matrix material. This is used in conjunction with a computationally facile scheme in which hereditary <span class="hlt">strains</span> are computed using a recursive relation suggested by Henriksen. Composite response is studied using two competing micro-models, viz. a simplified Square Cell Model (SSCM) and a <span class="hlt">Finite</span> Element based self-consistent Cylindrical Model (FECM). The algorithm is developed assuming that the material response computations are carried out in a module attached to a general purpose <span class="hlt">finite</span> element program used for composite structural analysis. It is shown that the SSCM as used in investigations of material nonlinearity can involve significant errors in the prediction of transverse Young's modulus and shear modulus. The errors in the <span class="hlt">elastic</span> <span class="hlt">strains</span> thus predicted are of the same order of magnitude as the creep <span class="hlt">strains</span> accruing due to visco-<span class="hlt">elasticity</span>. The FECM on the other hand does appear to perform better both in the prediction of <span class="hlt">elastic</span> constants and the study of creep response.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li class="active"><span>23</span></li> <li><a href="#" onclick='return showDiv("page_24");'>24</a></li> <li><a href="#" onclick='return showDiv("page_25");'>25</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_23 --> <div id="page_24" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li class="active"><span>24</span></li> <li><a href="#" onclick='return showDiv("page_25");'>25</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="461"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2014CompM..53.1341C&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2014CompM..53.1341C&link_type=ABSTRACT"><span id="translatedtitle">On the Assumed Natural <span class="hlt">Strain</span> method to alleviate locking in solid-shell NURBS-based <span class="hlt">finite</span> elements</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Caseiro, J. F.; Valente, R. A. F.; Reali, A.; Kiendl, J.; Auricchio, F.; Alves de Sousa, R. J.</p> <p>2014-06-01</p> <p>In isogeometric analysis (IGA), the functions used to describe the CAD geometry (such as NURBS) are also employed, in an isoparametric fashion, for the approximation of the unknown fields, leading to an exact geometry representation. Since the introduction of IGA, it has been shown that the high regularity properties of the employed functions lead in many cases to superior accuracy per degree of freedom with respect to standard FEM. However, as in Lagrangian elements, NURBS-based formulations can be negatively affected by the appearance of non-physical phenomena that "lock" the solution when constrained problems are considered. In order to alleviate such locking behaviors, the Assumed Natural <span class="hlt">Strain</span> (ANS) method proposed for Lagrangian formulations is extended to NURBS-based elements in the present work, within the context of solid-shell formulations. The performance of the proposed methodology is assessed by means of a set of numerical examples. The results allow to conclude that the employment of the ANS method to quadratic NURBS-based elements successfully alleviates non-physical phenomena such as shear and membrane locking, significantly improving the element performance.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/6920438','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/6920438"><span id="translatedtitle">Wave-induced response of poro-<span class="hlt">elastic</span> offshore foundations</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Toha, F.X.</p> <p>1983-01-01</p> <p>A plane <span class="hlt">strain</span> analysis based on Biot's theory of consolidation is utilized to investigate the pore-water pressures and displacements induced by steady-state linear planar waves beneath offshore gravity structures placed on poro-<span class="hlt">elastic</span> seabed of <span class="hlt">finite</span> thickness. The response is characterized by three controlling parameters, i.e., poroelasticity factor, fluid compressibility factor, and Poisson's Ratio. A parametric study, using a range of the controlling parameters encountered in practice, indicates that the response is governed primarily by the poro-<span class="hlt">elasticity</span> factor and to a lesser extent by Poisson's Ratio (fluid compressibility factor has negligible influence for saturated soils). For offshore gravity structures, the wave-induced moment and horizontal force exerted by the structure on the foundation contribute most to the overall response while the influence of sea water pressure penetration through the sea bottom is, in general, negligible. For smaller structures, however, the latter influence dominates the response for soils as fine as silty sand. The maximum shear <span class="hlt">strain</span> amplitudes evaluated imply that the soil response remains primarily in the linear <span class="hlt">elastic</span> range, even for severe storm loadings. An experimental procedure was developed for the measurement of a composite poro-<span class="hlt">elastic</span> property which combines all the pertinent soil properties. Two test configurations were found to be suitable depending on the hydraulic conductivity of the soil considered. The results of test on nine specimens reconstituted from three soil samples conform with the theoretical estimates and indicate that the developed procedure is viable.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/20366547','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/20366547"><span id="translatedtitle">Wrinkling and <span class="hlt">strain</span> softening in single-wall carbon nanotube membranes.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Hobbie, E K; Simien, D O; Fagan, J A; Huh, J Y; Chung, J Y; Hudson, S D; Obrzut, J; Douglas, J F; Stafford, C M</p> <p>2010-03-26</p> <p>The nonlinear <span class="hlt">elasticity</span> of thin supported membranes assembled from length purified single-wall carbon nanotubes is analyzed through the wrinkling instability that develops under uniaxial compression. In contrast with thin polymer films, pristine nanotube membranes exhibit strong softening under <span class="hlt">finite</span> <span class="hlt">strain</span> associated with bond slip and network fracture. We model the response as a shift in percolation threshold generated by <span class="hlt">strain</span>-induced nanotube alignment in accordance with theoretical predictions. PMID:20366547</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/754909','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/754909"><span id="translatedtitle"><span class="hlt">Elastic</span>-plastic analysis of the PVRC burst disk tests with comparison to the ASME code -- Primary stress limits</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Jones, D.P.; Holliday, J.E.</p> <p>1999-02-01</p> <p>This paper provides a comparison between <span class="hlt">finite</span> element analysis results and test data from the Pressure Vessel Research Council (PVRC) burst disk program. Testing sponsored by the PVRC over 20 years ago was done by pressurizing circular flat disks made from three different materials until failure by bursting. The purpose of this re-analysis is to investigate the use of <span class="hlt">finite</span> element analysis (FEA) to assess the primary stress limits of the ASME Boiler and Pressure Vessel Code (1998) and to qualify the use of <span class="hlt">elastic</span>-plastic (EP-FEA) for limit load calculations. The three materials tested represent the range of strength and ductility found in modern pressure vessel construction and include a low strength high ductility material, a medium strength medium ductility material, and a high strength low ductility low alloy material. Results of <span class="hlt">elastic</span> and EP-FEA are compared to test data. Stresses from the <span class="hlt">elastic</span> analyses are linearized for comparison of Code primary stress limits to test results. <span class="hlt">Elastic</span>-plastic analyses are done using both best-estimate and <span class="hlt">elastic</span>-perfectly plastic (EPP) stress-<span class="hlt">strain</span> curves. Both large <span class="hlt">strain</span>-large displacement (LSLD) and small <span class="hlt">strain</span>-small displacement (SSSD) assumptions are used with the EP-FEA. Analysis results are compared to test results to evaluate the various analysis methods, models, and assumptions as applied to the bursting of thin disks.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19950008040','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19950008040"><span id="translatedtitle"><span class="hlt">Elastic</span>-plastic models for multi-site damage</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Actis, Ricardo L.; Szabo, Barna A.</p> <p>1994-01-01</p> <p>This paper presents recent developments in advanced analysis methods for the computation of stress site damage. The method of solution is based on the p-version of the <span class="hlt">finite</span> element method. Its implementation was designed to permit extraction of linear stress intensity factors using a superconvergent extraction method (known as the contour integral method) and evaluation of the J-integral following an <span class="hlt">elastic</span>-plastic analysis. Coarse meshes are adequate for obtaining accurate results supported by p-convergence data. The <span class="hlt">elastic</span>-plastic analysis is based on the deformation theory of plasticity and the von Mises yield criterion. The model problem consists of an aluminum plate with six equally spaced holes and a crack emanating from each hole. The cracks are of different sizes. The panel is subjected to a remote tensile load. Experimental results are available for the panel. The plasticity analysis provided the same limit load as the experimentally determined load. The results of <span class="hlt">elastic</span>-plastic analysis were compared with the results of linear <span class="hlt">elastic</span> analysis in an effort to evaluate how plastic zone sizes influence the crack growth rates. The onset of net-section yielding was determined also. The results show that crack growth rate is accelerated by the presence of adjacent damage, and the critical crack size is shorter when the effects of plasticity are taken into consideration. This work also addresses the effects of alternative stress-<span class="hlt">strain</span> laws: The <span class="hlt">elastic</span>-ideally-plastic material model is compared against the Ramberg-Osgood model.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19880012097','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19880012097"><span id="translatedtitle">Kinematic support using <span class="hlt">elastic</span> elements</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Geirsson, Arni; Debra, Daniel B.</p> <p>1988-01-01</p> <p>The design of kinematic supports using <span class="hlt">elastic</span> elements is reviewed. The two standard methods (cone, Vee and flat and three Vees) are presented and a design example involving a machine tool metrology bench is given. Design goals included thousandfold <span class="hlt">strain</span> attenuation in the bench relative to the base when the base <span class="hlt">strains</span> due to temperature variations and shifting loads. Space applications are also considered.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/18493785','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/18493785"><span id="translatedtitle">Influence of the benign enlargement of the subarachnoid space on the bridging veins <span class="hlt">strain</span> during a shaking event: a <span class="hlt">finite</span> element study.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Raul, Jean-Sébastien; Roth, Sébastien; Ludes, Bertrand; Willinger, Rémy</p> <p>2008-07-01</p> <p>There is controversy regarding the influence of the benign enlargement of the subarachnoid space on intracranial injuries in the field of the shaken baby syndrome. In the literature, several terminologies exists to define this entity illustrating the lack of unicity on this theme, and often what is "benign" enlargement is mistaken with an old subdural bleeding or with abnormal enlargement due to brain pathology. This certainly led to mistaken conclusions. To investigate the influence of the benign enlargement of the subarachnoid space on child head injury and especially its influence on the bridging veins, we used a <span class="hlt">finite</span> element model of a 6-month-old child head on which the size of the subarachnoid space was modified. Regarding the bridging veins <span class="hlt">strain</span>, which is at the origin of the subdural bleeding when shaking an infant, our results show that the enlargement of the subarachnoid space has a damping effect which reduces the relative brain/skull displacement. Our numerical simulations suggest that the benign enlargement of the subarachnoid space may not be considered as a risk factor for subdural bleeding. PMID:18493785</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/751349','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/751349"><span id="translatedtitle">A <span class="hlt">finite</span> element model of ferroelectric/ferroelastic polycrystals</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>HWANG,STEPHEN C.; MCMEEKING,ROBERT M.</p> <p>2000-02-17</p> <p>A <span class="hlt">finite</span> element model of polarization switching in a polycrystalline ferroelectric/ferroelastic ceramic is developed. It is assumed that a crystallite switches if the reduction in potential energy of the polycrystal exceeds a critical energy barrier per unit volume of switching material. Each crystallite is represented by a <span class="hlt">finite</span> element with the possible dipole directions assigned randomly subject to crystallographic constraints. The model accounts for both electric field induced (i.e. ferroelectric) switching and stress induced (i.e. ferroelastic) switching with piezoelectric interactions. Experimentally measured <span class="hlt">elastic</span>, dielectric, and piezoelectric constants are used consistently, but different effective critical energy barriers are selected phenomenologically. Electric displacement versus electric field, <span class="hlt">strain</span> versus electric field, stress versus <span class="hlt">strain</span>, and stress versus electric displacement loops of a ceramic lead lanthanum zirconate titanate (PLZT) are modeled well below the Curie temperature.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016PhRvB..93u4105H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016PhRvB..93u4105H"><span id="translatedtitle">Nonlinear <span class="hlt">elastic</span> effects in phase field crystal and amplitude equations: Comparison to ab initio simulations of bcc metals and graphene</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Hüter, Claas; Friák, Martin; Weikamp, Marc; Neugebauer, Jörg; Goldenfeld, Nigel; Svendsen, Bob; Spatschek, Robert</p> <p>2016-06-01</p> <p>We investigate nonlinear <span class="hlt">elastic</span> deformations in the phase field crystal model and derived amplitude equation formulations. Two sources of nonlinearity are found, one of them is based on geometric nonlinearity expressed through a <span class="hlt">finite</span> <span class="hlt">strain</span> tensor. This <span class="hlt">strain</span> tensor is based on the inverse right Cauchy-Green deformation tensor and correctly describes the <span class="hlt">strain</span> dependence of the stiffness for anisotropic and isotropic behavior. In isotropic one- and two-dimensional situations, the <span class="hlt">elastic</span> energy can be expressed equivalently through the left deformation tensor. The predicted isotropic low-temperature nonlinear <span class="hlt">elastic</span> effects are directly related to the Birch-Murnaghan equation of state with bulk modulus derivative K'=4 for bcc. A two-dimensional generalization suggests K2D '=5 . These predictions are in agreement with ab initio results for large <span class="hlt">strain</span> bulk deformations of various bcc elements and graphene. Physical nonlinearity arises if the <span class="hlt">strain</span> dependence of the density wave amplitudes is taken into account and leads to <span class="hlt">elastic</span> weakening. For anisotropic deformation, the magnitudes of the amplitudes depend on their relative orientation to the applied <span class="hlt">strain</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015PhRvL.115b5703Z','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015PhRvL.115b5703Z"><span id="translatedtitle">Quantum Critical <span class="hlt">Elasticity</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Zacharias, Mario; Paul, Indranil; Garst, Markus</p> <p>2015-07-01</p> <p>We discuss <span class="hlt">elastic</span> instabilities of the atomic crystal lattice at zero temperature. Because of long-range shear forces of the solid, at such transitions the phonon velocities vanish, if at all, only along certain crystallographic directions, and, consequently, the critical phonon fluctuations are suppressed to a lower dimensional manifold and governed by a Gaussian fixed point. In the case of symmetry-breaking <span class="hlt">elastic</span> transitions, a characteristic critical phonon thermodynamics arises that is found, e.g., to violate Debye's T3 law for the specific heat. We point out that quantum critical <span class="hlt">elasticity</span> is triggered whenever a critical soft mode couples linearly to the <span class="hlt">strain</span> tensor. In particular, this is relevant for the electronic Ising-nematic quantum phase transition in a tetragonal crystal as discussed in the context of certain cuprates, ruthenates, and iron-based superconductors.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/975601','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/975601"><span id="translatedtitle"><span class="hlt">Elastic</span> properties of HMX.</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Sewell, T. D.; Bedrov, D.; Menikoff, Ralph; Smith, G. D.</p> <p>2001-01-01</p> <p>Atomistic molecular dynamics simulations have been used to calculate isothermal <span class="hlt">elastic</span> properties for {beta}-, {alpha}-, and {delta}-HMX. The complete <span class="hlt">elastic</span> tensor for each polymorph was determined at room temperature and pressure via analysis of microscopic <span class="hlt">strain</span> fluctuations using formalism due to Rahman and Parrinello [J. Chem. Phys. 76,2662 (1982)]. Additionally, the isothermal compression curve was computed for {beta}-HMX for 0 {le} p {le} 10.6 GPa; the bulk modulus K and its pressure derivative K{prime} were obtained from two fitting forms employed previously in experimental studies of the {beta}-HMX equation of state. Overall, the results indicate good agreement between the bulk modulus predicted from the measured and calculated compression curves. The bulk modulus determined directly from the <span class="hlt">elastic</span> tensor of {beta}-HMX is in significant disagreement with the compression curve-based results. The explanation for this discrepancy is an area of current research.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/26207483','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/26207483"><span id="translatedtitle">Quantum Critical <span class="hlt">Elasticity</span>.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Zacharias, Mario; Paul, Indranil; Garst, Markus</p> <p>2015-07-10</p> <p>We discuss <span class="hlt">elastic</span> instabilities of the atomic crystal lattice at zero temperature. Because of long-range shear forces of the solid, at such transitions the phonon velocities vanish, if at all, only along certain crystallographic directions, and, consequently, the critical phonon fluctuations are suppressed to a lower dimensional manifold and governed by a Gaussian fixed point. In the case of symmetry-breaking <span class="hlt">elastic</span> transitions, a characteristic critical phonon thermodynamics arises that is found, e.g., to violate Debye's T(3) law for the specific heat. We point out that quantum critical <span class="hlt">elasticity</span> is triggered whenever a critical soft mode couples linearly to the <span class="hlt">strain</span> tensor. In particular, this is relevant for the electronic Ising-nematic quantum phase transition in a tetragonal crystal as discussed in the context of certain cuprates, ruthenates, and iron-based superconductors. PMID:26207483</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009SPIE.7499E..0US','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009SPIE.7499E..0US"><span id="translatedtitle">Reflectance difference laser measurements applied to the study of the stress/<span class="hlt">strain</span> state in materials</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Saucedo-Zárate, Carlos H.; López-López, Maximo; Sánchez-López, Carlos; Correa-Figueroa, Jose Luis; Huerta-Ruelas, Jorge A.</p> <p>2009-09-01</p> <p>Development of experimental setup to study <span class="hlt">strain</span>/stress state in materials emerges from a need to evaluate by a nondestructive and non-invasive technique the performance in new materials like semiconductor heterostructures, composite materials and alloys. The system was designed and built to be used as a multi-functional experimental setup. The main purpose is to characterize materials in <span class="hlt">elastic</span> and plastic regime by reflectance difference laser measurements and <span class="hlt">strain</span> gages. This system allows the generalization of results obtained from a theoretical model based in <span class="hlt">Finite</span> Element Model and experimental measurements taken in <span class="hlt">finite</span> specific points with <span class="hlt">strain</span> gages. A NI™ platform is used for signal conditioning and processing. System built is described which includes an optical setup to measure reflectance difference laser (RDL), and a flexor which applies deformation in a link, with a micrometer. A correlation bigger than 0.95 was found between optical signal, <span class="hlt">strain</span> gage signal, and <span class="hlt">finite</span> element modeling.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2002EGSGA..27.6398S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2002EGSGA..27.6398S"><span id="translatedtitle">Folding of Layers of <span class="hlt">Finite</span> Length</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Schmid, D. W.; Podladchikov, Yu. Yu.; Marques, F.</p> <p></p> <p>All existing folding theories assume that the layers are infinitely long or, which is mathematically equivalent, that the compression is directly applied to the lateral boundaries. These assumptions are not always justified for natural geological sys- tems. In fact we can observe that on all scales, from veins to sub-ducting slabs, the layers are of <span class="hlt">finite</span> length and that there are no distinct, rigid walls pushing the lay- ers from the side. Using the method of Muskhelishvili we have derived the complete two-dimensional solution of an elliptic object embedded in a matrix and subject to far field boundary conditions; pure shear, simple shear and arbitrary combinations thereof. The rheology of the matrix is viscous, the layer may behave either <span class="hlt">elastically</span> or viscous. Using the values from this background state analysis, stress, pressure and <span class="hlt">strain</span> rate, we performed the classical linear stability analysis to examine the mech- anism of folding in the described setup. The resulting expressions maximum growth rates and dominant wavelengths are applicable to general geological systems; in the limit of an infinite aspect ratio of the layer the classical expressions of Biot are ob- tained for all other cases new expressions result. Our main results are: 1. Folding of <span class="hlt">finite</span> length layers is controlled by the ratio of aspect ratio to competence contrast. 2. The described setup explains why in nature only folds can be observed with a rela- tively small wavelength to thickness ratio, suggesting small viscosity contrast 3. The problem of the unknown compressive stress value for the <span class="hlt">elastic</span> layer is solved. 4. For <span class="hlt">finite</span> length <span class="hlt">elastic</span> layers the dominant wavelength selection shows a cubic, instead of square, root dependence. 5. A complete table, describing the folding in all the possible limits is presented and the applicability to natural systems discussed. All the presented results were checked numerically and/or with analogue models.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/22210585','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/22210585"><span id="translatedtitle">Features of the stress-<span class="hlt">strain</span> state of Si/SiO{sub 2}/Ge heterostructures with germanium nanoislands of a limited density</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Kuryliuk, V. V. Korotchenkov, O. A.</p> <p>2013-08-15</p> <p>Within the <span class="hlt">elastic</span> continuum model, with the use of the <span class="hlt">finite</span>-element method, the stress-<span class="hlt">strain</span> state of silicon-germanium heterostructures with semispherical germanium islands grown on an oxidized silicon surface is calculated. It is shown that as the density of islands is increased to limiting values, in the SiGe structure with open quantum dots the value and spatial distribution of the <span class="hlt">elastic-strain</span> fields significantly change. The results of theoretical calculation allow the heterostructure portions with the maximum variation in the stress-<span class="hlt">strain</span> state to be determined. The position of such a portions can be controlled by changing the density of islands.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19720026267','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19720026267"><span id="translatedtitle">Computer program: Jet 3 to calculate the large <span class="hlt">elastic</span> plastic dynamically induced deformations of free and restrained, partial and/or complete structural rings</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Wu, R. W.; Witmer, E. A.</p> <p>1972-01-01</p> <p>A user-oriented FORTRAN 4 computer program, called JET 3, is presented. The JET 3 program, which employs the spatial <span class="hlt">finite</span>-element and timewise <span class="hlt">finite</span>-difference method, can be used to predict the large two-dimensional <span class="hlt">elastic</span>-plastic transient Kirchhoff-type deformations of a complete or partial structural ring, with various support conditions and restraints, subjected to a variety of initial velocity distributions and externally-applied transient forcing functions. The geometric shapes of the structural ring can be circular or arbitrarily curved and with variable thickness. <span class="hlt">Strain</span>-hardening and <span class="hlt">strain</span>-rate effects of the material are taken into account.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1990ZaMP...41..315N','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1990ZaMP...41..315N"><span id="translatedtitle">A critical review of the state of <span class="hlt">finite</span> plasticity</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Naghdi, P. M.</p> <p>1990-05-01</p> <p>The object of this paper is to provide a critical review of the current state of plasticity in the presence of <span class="hlt">finite</span> deformation. In view of the controversy regarding a number of fundamental issues between several existing schools of plasticity, the areas of agreement are described separately from those of disagreement. Attention is mainly focussed on the purely mechanical, rate-independent, theory of <span class="hlt">elastic</span>-plastic materials, although closely related topics such as rate-dependent behavior, thermal effects, experimental and computational aspects, microstructural effects and crystal plasticity are also discussed and potentially fruitful directions are identified. A substantial portion of this review is devoted to the area of disagreement that covers a detailed presentation of argument(s), both pro and con, for all of the basic constitutive ingredients of the rate-independent theory such as the primitive notion or definition of plastic <span class="hlt">strain</span>, the structure of the constitutive equation for the stress response, the yield function, the loading criteria and the flow and the hardening rules. The majority of current research in <span class="hlt">finite</span> plasticity theory, as with its infinitesimal counterpart, still utilizes a (classical) stress-based approach which inherently possesses some shortcomings for the characterization of <span class="hlt">elastic</span>-plastic materials. These and other anomalous behavior of a stress-based formulation are contrasted with the more recent <span class="hlt">strain</span>-based formulation of <span class="hlt">finite</span> plasticity. A number of important features and theoretical advantages of the latter formulation, along with its computational potential and experimental interpretation, are discussed separately.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=19920042526&hterms=STRESS+STRAIN+PARAMETERS&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3DSTRESS%2BSTRAIN%2BPARAMETERS','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=19920042526&hterms=STRESS+STRAIN+PARAMETERS&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3DSTRESS%2BSTRAIN%2BPARAMETERS"><span id="translatedtitle"><span class="hlt">Elastic</span>-plastic analysis of AS4/PEEK composite laminate using a one-parameter plasticity model</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Sun, C. T.; Yoon, K. J.</p> <p>1992-01-01</p> <p>A one-parameter plasticity model was shown to adequately describe the plastic deformation of AS4/PEEK (APC-2) unidirectional thermoplastic composite. This model was verified further for unidirectional and laminated composite panels with and without a hole. The <span class="hlt">elastic</span>-plastic stress-<span class="hlt">strain</span> relations of coupon specimens were measured and compared with those predicted by the <span class="hlt">finite</span> element analysis using the one-parameter plasticity model. The results show that the one-parameter plasticity model is suitable for the analysis of <span class="hlt">elastic</span>-plastic deformation of AS4/PEEK composite laminates.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19850023230','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19850023230"><span id="translatedtitle">Two simplified procedures for predicting cyclic material response from a <span class="hlt">strain</span> history</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Kaufman, A.; Moreno, V.</p> <p>1985-01-01</p> <p>Simplified inelastic analysis procedures were developed at NASA Lewis and Pratt & Whitney Aircraft for predicting the stress-<span class="hlt">strain</span> response at the critical location of a thermomechanically cycled structure. These procedures are intended primarily for use as economical structural analysis tools in the early design stages of aircraft engine hot section components where nonlinear <span class="hlt">finite</span>-element analyses would be prohibitively expensive. Both simplified methods use as input the total <span class="hlt">strain</span> history calculated from a linear <span class="hlt">elastic</span> analysis. The <span class="hlt">elastic</span> results are modified to approximate the characteristics of the inelastic cycle by incremental solution techniques. A von Mises yield criterion is used to determine the onset of active plasticity. The fundamental assumption of these methods is that the inelastic <span class="hlt">strain</span> is local and constrained from redistribution by the surrounding <span class="hlt">elastic</span> material.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/1042055','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/1042055"><span id="translatedtitle"><span class="hlt">Elasticity</span> of Wadsleyite at 12 GPa1073K</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>W Liu; J Kung; B Li; N Nishiyama; Y Wang</p> <p>2011-12-31</p> <p><span class="hlt">Elasticity</span> of (Mg{sub 0.87}Fe{sub 0.13}){sub 2}SiO{sub 4} wadsleyite has been measured at simultaneous high pressure and high temperature to 12 GPa and 1073 K using ultrasonic interferometry in conjunction with synchrotron X-radiation. The <span class="hlt">elastic</span> moduli and their pressure and temperature derivatives are precisely determined using pressure-standard-free third-order and fourth-order <span class="hlt">finite</span> <span class="hlt">strain</span> equations. Combined with previous thermoelastic data on olivine, the density, velocity and acoustic impedance contrasts between {alpha}- and {beta}-(Mg{sub 0.9}Fe{sub 0.1}){sub 2}SiO{sub 4} at 410-km depth are calculated along a 1673 K adiabatic geotherm. Both the third- and fourth-order <span class="hlt">finite</span> <span class="hlt">strain</span> equation fitting results give estimation of {approx}33-58% olivine content in the upper mantle to account for a seismic discontinuity of {approx}5% velocity jumps, and 8.5% (P wave) and 11.1% (S wave) impedance jumps at 410 km depth.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li class="active"><span>24</span></li> <li><a href="#" onclick='return showDiv("page_25");'>25</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_24 --> <div id="page_25" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_24");'>24</a></li> <li class="active"><span>25</span></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="481"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/1955','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/1955"><span id="translatedtitle">A Method for Connecting Dissimilar <span class="hlt">Finite</span> Element Meshes in Three Dimensions</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Dohrmann, C.R.; Heinstein, M.W.; Key, S.W.</p> <p>1998-11-12</p> <p>A method is presented for connecting dissimilar <span class="hlt">finite</span> element meshes in three dimensions. The method combines the concept of master and slave surfaces with the uniform <span class="hlt">strain</span> approach for surface, corrections <span class="hlt">finite</span> elements- By modifyhg the are made to element formulations boundaries of elements on the slave such that first-order patch tests are passed. The method can be used to connect meshes which use different element types. In addition, master and slave surfaces can be designated independently of relative mesh resolutions. Example problems in three-dimensional linear <span class="hlt">elasticity</span> are presented.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://pubs.er.usgs.gov/publication/70021934','USGSPUBS'); return false;" href="http://pubs.er.usgs.gov/publication/70021934"><span id="translatedtitle">Test of two methods for faulting on <span class="hlt">finite</span>-difference calculations</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Andrews, D.J.</p> <p>1999-01-01</p> <p>Tests of two fault boundary conditions show that each converges with second order accuracy as the <span class="hlt">finite</span>-difference grid is refined. The first method uses split nodes so that there are disjoint grids that interact via surface traction. The 3D version described here is a generalization of a method I have used extensively in 2D; it is as accurate as the 2D version. The second method represents fault slip as inelastic <span class="hlt">strain</span> in a fault zone. Offset of stress from its <span class="hlt">elastic</span> value is seismic moment density. Implementation of this method is quite simple in a <span class="hlt">finite</span>-difference scheme using velocity and stress as dependent variables.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2000JMPSo..48...29B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2000JMPSo..48...29B"><span id="translatedtitle"><span class="hlt">Elastic</span> properties of polycrystals—influence of texture and stereology</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Bunge, H. J.; Kiewel, R.; Reinert, Th; Fritsche, L.</p> <p>2000-01-01</p> <p>The macroscopic <span class="hlt">elastic</span> properties of polycrystalline materials depend on the <span class="hlt">elastic</span> properties of the crystallites and the way how these are 'arranged' in the polycrystalline aggregate. This comprises the volume fraction of crystal orientations (texture) as well as their arrangement in space (stereology). It is estimated that the stereological aggregate parameters may contribute up to 25% of the maximum texture influence. Model calculations of the effective macroscopic <span class="hlt">elastic</span> properties were carried out using a grain cluster model which is a <span class="hlt">finite</span> discretization of the aggregate function g( x) describing the complete 'orientation-stereology' of the polycrystalline material. The most important stereological parameters influencing the effective <span class="hlt">elastic</span> constants are grain shape expressed by two axis ratios, grain packing expressed by the space filling factor of the lattice of grain centres and orientation pair correlation of neighbouring grains expressed by the misorientation distribution function. By rotating the orientation of only one grain it can be shown that grain interaction <span class="hlt">strains</span> decrease rapidly and may be neglected beyond the second order neighbours.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015JMPSo..85...16R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015JMPSo..85...16R"><span id="translatedtitle">A model for compression-weakening materials and the <span class="hlt">elastic</span> fields due to contractile cells</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Rosakis, Phoebus; Notbohm, Jacob; Ravichandran, Guruswami</p> <p>2015-12-01</p> <p>We construct a homogeneous, nonlinear <span class="hlt">elastic</span> constitutive law that models aspects of the mechanical behavior of inhomogeneous fibrin networks. Fibers in such networks buckle when in compression. We model this as a loss of stiffness in compression in the stress-<span class="hlt">strain</span> relations of the homogeneous constitutive model. Problems that model a contracting biological cell in a <span class="hlt">finite</span> matrix are solved. It is found that matrix displacements and stresses induced by cell contraction decay slower (with distance from the cell) in a compression weakening material than linear <span class="hlt">elasticity</span> would predict. This points toward a mechanism for long-range cell mechanosensing. In contrast, an expanding cell would induce displacements that decay faster than in a linear <span class="hlt">elastic</span> matrix.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015PhyU...58.1106V','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015PhyU...58.1106V"><span id="translatedtitle"><span class="hlt">Elastic</span> properties of solids at high pressure</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Vekilov, Yu Kh; Krasilnikov, O. M.; Lugovskoy, A. V.</p> <p>2015-11-01</p> <p>This review examines the <span class="hlt">elastic</span> response of solids under load. The definitions of isothermal and adiabatic <span class="hlt">elastic</span> constants of ( n≥2) for a loaded crystal are given. For the case of hydrostatic pressure, two techniques are proposed for calculating the second-, third-, and fourth-order <span class="hlt">elastic</span> constants from the energy-<span class="hlt">strain</span> and stress-<span class="hlt">strain</span> relations. As an example, using the proposed approach within the framework of the density functional theory, the second- to fourth-order <span class="hlt">elastic</span> constants of bcc tungsten are calculated for the pressure range of 0-600 GPa.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/25134434','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/25134434"><span id="translatedtitle">Continuum description of the Poisson's ratio of ligament and tendon under <span class="hlt">finite</span> deformation.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Swedberg, Aaron M; Reese, Shawn P; Maas, Steve A; Ellis, Benjamin J; Weiss, Jeffrey A</p> <p>2014-09-22</p> <p>Ligaments and tendons undergo volume loss when stretched along the primary fiber axis, which is evident by the large, <span class="hlt">strain</span>-dependent Poisson's ratios measured during quasi-static tensile tests. Continuum constitutive models that have been used to describe ligament material behavior generally assume incompressibility, which does not reflect the volumetric material behavior seen experimentally. We developed a <span class="hlt">strain</span> energy equation that describes large, <span class="hlt">strain</span> dependent Poisson's ratios and nonlinear, transversely isotropic behavior using a novel method to numerically enforce the desired volumetric behavior. The Cauchy stress and spatial <span class="hlt">elasticity</span> tensors for this <span class="hlt">strain</span> energy equation were derived and implemented in the FEBio <span class="hlt">finite</span> element software (www.febio.org). As part of this objective, we derived the Cauchy stress and spatial <span class="hlt">elasticity</span> tensors for a compressible transversely isotropic material, which to our knowledge have not appeared previously in the literature. <span class="hlt">Elastic</span> simulations demonstrated that the model predicted the nonlinear, upwardly concave uniaxial stress-<span class="hlt">strain</span> behavior while also predicting a <span class="hlt">strain</span>-dependent Poisson's ratio. Biphasic simulations of stress relaxation predicted a large outward fluid flux and substantial relaxation of the peak stress. Thus, the results of this study demonstrate that the viscoelastic behavior of ligaments and tendons can be predicted by modeling fluid movement when combined with a large Poisson's ratio. Further, the constitutive framework provides the means for accurate simulations of ligament volumetric material behavior without the need to resort to micromechanical or homogenization methods, thus facilitating its use in large scale, whole joint models. PMID:25134434</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4179457','PMC'); return false;" href="http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4179457"><span id="translatedtitle">Continuum Description of the Poisson's Ratio of Ligament and Tendon Under <span class="hlt">Finite</span> Deformation</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Swedberg, Aaron M.; Reese, Shawn P.; Maas, Steve A.; Ellis, Benjamin J.; Weiss, Jeffrey A.</p> <p>2014-01-01</p> <p>Ligaments and tendons undergo volume loss when stretched along the primary fiber axis, which is evident by the large, <span class="hlt">strain</span>-dependent Poisson's ratios measured during quasi-static tensile tests. Continuum constitutive models that have been used to describe ligament material behavior generally assume incompressibility, which does not reflect the volumetric material behavior seen experimentally. We developed a <span class="hlt">strain</span> energy equation that describes large, <span class="hlt">strain</span> dependent Poisson's ratios and nonlinear, transversely isotropic behavior using a novel method to numerically enforce the desired volumetric behavior. The Cauchy stress and spatial <span class="hlt">elasticity</span> tensors for this <span class="hlt">strain</span> energy equation were derived and implemented in the FEBio <span class="hlt">finite</span> element software (www.febio.org). As part of this objective, we derived the Cauchy stress and spatial <span class="hlt">elasticity</span> tensors for a compressible transversely isotropic material, which to our knowledge have not appeared previously in the literature. <span class="hlt">Elastic</span> simulations demonstrated that the model predicted the nonlinear, upwardly concave uniaxial stress-<span class="hlt">strain</span> behavior while also predicting a <span class="hlt">strain</span>-dependent Poisson's ratio. Biphasic simulations of stress relaxation predicted a large outward fluid flux and substantial relaxation of the peak stress. Thus, the results of this study demonstrate that the viscoelastic behavior of ligaments and tendons can be predicted by modeling fluid movement when combined with a large Poisson's ratio. Further, the constitutive framework provides the means for accurate simulations of ligament volumetric material behavior without the need to resort to micromechanical or homogenization methods, thus facilitating its use in large scale, whole joint models. PMID:25134434</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/136325','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/136325"><span id="translatedtitle">Electronic transport in the quasi-one-dimensional conductors, NbSe{sub 3} and Tl{sub 2}Mo{sub 6}Se{sub 6}, under <span class="hlt">elastic</span> <span class="hlt">strain</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Tseng, Yaw-Teng</p> <p>1993-12-31</p> <p>I have investigated two different linear chain compounds; NbSe{sub 3}, a conventional CDW material undergoing two independent charge density wave phase transitions at 144 K and 59 K, and Tl{sub 2}Mo{sub 6}Se{sub 6}, a novel quasi-one-dimensional conductor standing out from its M{sub 2}Mo{sub 6}X{sub 6} family because of its superconductivity at 5-7 K. Under <span class="hlt">elastic</span> <span class="hlt">strain</span> {var_epsilon}, the threshold field E{sub Tau} is greatly increased for the upper CDW but not for the lower CDW. The minimum in E{sub Tau} doubles at {epsilon} = 1% for the upper CDW whereas it increases less than 10% for the lower CDW. Using a plot of the E{sub Tau} vs. the reduced temperature, t = T/T{sub Rho} where T{sub Rho} is the Peierls transition temperature, we show that the t{sub min}, temperature where E{sub Tau} goes through a minimum, is independent of {epsilon}/ Below t{sub min}, <span class="hlt">elastic</span> <span class="hlt">strain</span> experiments can separate E{sub Tau} into two additive terms, E{sub Tau}({epsilon},{Tau}) = E{prime} {sub Tau}(t) + E{double_prime}{sub Tau}({epsilon},t) is independent of t and is equal to Emin below tmin., and E`{sub Tau}(t) is independent of {epsilon} and n{sub i}. We speculate that E{prime}{sub Tau}(t) is due to phase slip, and E{double_prime}{sub Tau}({epsilon},t) is due to impurity pinning. Such a separation is valid for both the upper and lower CDWs. The lower CDW resistance anomaly and thermopower are strongly enhanced by {epsilon}. An interesting feature is that the slope of the piezoresistance dR/D{sigma} and piezothermopower dS/d{sigma} both show a peculiar decrease at {epsilon} = 0.5 {plus_minus} 0.1%. They exhibit a plateau-like region below 40 K. We discuss the results in term of suggested Fermi surfaces topological change using a model in which a electron-like Fermi surface at the zone boundary is depleted under <span class="hlt">elastic</span> <span class="hlt">strain</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/25489098','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/25489098"><span id="translatedtitle">Robust scaling of strength and <span class="hlt">elastic</span> constants and universal cooperativity in disordered colloidal micropillars.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Strickland, Daniel J; Huang, Yun-Ru; Lee, Daeyeon; Gianola, Daniel S</p> <p>2014-12-23</p> <p>We study the uniaxial compressive behavior of disordered colloidal free-standing micropillars composed of a bidisperse mixture of 3- and 6-μm polystyrene particles. Mechanical annealing of confined pillars enables variation of the packing fraction across the phase space of colloidal glasses. The measured normalized strengths and <span class="hlt">elastic</span> moduli of the annealed freestanding micropillars span almost three orders of magnitude despite similar plastic morphology governed by shear banding. We measure a robust correlation between ultimate strengths and <span class="hlt">elastic</span> constants that is invariant to relative humidity, implying a critical <span class="hlt">strain</span> of ∼0.01 that is strikingly similar to that observed in metallic glasses (MGs) [Johnson WL, Samwer K (2005) Phys Rev Lett 95:195501] and suggestive of a universal mode of cooperative plastic deformation. We estimate the characteristic <span class="hlt">strain</span> of the underlying cooperative plastic event by considering the energy necessary to create an Eshelby-like ellipsoidal inclusion in an <span class="hlt">elastic</span> matrix. We find that the characteristic <span class="hlt">strain</span> is similar to that found in experiments and simulations of other disordered solids with distinct bonding and particle sizes, suggesting a universal criterion for the <span class="hlt">elastic</span> to plastic transition in glassy materials with the capacity for <span class="hlt">finite</span> plastic flow. PMID:25489098</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1989apme.proc..138T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1989apme.proc..138T"><span id="translatedtitle">Integrated <span class="hlt">finite</span> element model of composite materials</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Teply, Jan L.; Herbein, William C.</p> <p>1989-05-01</p> <p>Two problems traditionally addressed in the area of micromechanics of composite materials can be briefly summarized as follows: (1) for a macroscopically uniform volume of composite material, which is subjected to macroscopically uniform boundary tractions, displacements or heat influx, find overall thermomechanical properties in terms of the thermomechanical properties of the individual constituents; and (2) for the same material volume and boundary conditions as above, find the local stress, <span class="hlt">strain</span>, and temperature fields in the constituents and on the interfaces. Two different types of micromechanical models are usually applied to the solutions of these two types of problems. For linear <span class="hlt">elastic</span> materials, the micromechanical models to solve problem (1) offer simple solutions of overall thermomechanical properties either in terms of bound which are derived from periodic or random microstructures, or in terms of single estimates, which are derived from a solution of an isolated inclusion. The <span class="hlt">finite</span> element variational approaches are applied to integrate the solutions of problems (1) and (2) into one model. The application of displacement and equilibrium variational approaches to the calculation of overall <span class="hlt">elastic</span>-plastic properties, are extended to the solution of the second problem. The integrated model is then applied to calculate the overall properties and local stress and <span class="hlt">strain</span> fields of boron-aluminum composites subjected to transverse tension, in-plane shear and bending.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19990049216','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19990049216"><span id="translatedtitle">Quasi-Static Viscoelastic <span class="hlt">Finite</span> Element Model of an Aircraft Tire</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Johnson, Arthur R.; Tanner, John A.; Mason, Angela J.</p> <p>1999-01-01</p> <p>An <span class="hlt">elastic</span> large displacement thick-shell mixed <span class="hlt">finite</span> element is modified to allow for the calculation of viscoelastic stresses. Internal <span class="hlt">strain</span> variables are introduced at the element's stress nodes and are employed to construct a viscous material model. First order ordinary differential equations relate the internal <span class="hlt">strain</span> variables to the corresponding <span class="hlt">elastic</span> <span class="hlt">strains</span> at the stress nodes. The viscous stresses are computed from the internal <span class="hlt">strain</span> variables using viscous moduli which are a fraction of the <span class="hlt">elastic</span> moduli. The energy dissipated by the action of the viscous stresses is included in the mixed variational functional. The nonlinear quasi-static viscous equilibrium equations are then obtained. Previously developed Taylor expansions of the nonlinear <span class="hlt">elastic</span> equilibrium equations are modified to include the viscous terms. A predictor-corrector time marching solution algorithm is employed to solve the algebraic-differential equations. The viscous shell element is employed to computationally simulate a stair-step loading and unloading of an aircraft tire in contact with a frictionless surface.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2006teel.book.....M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2006teel.book.....M"><span id="translatedtitle"><span class="hlt">Elasticity</span> theory</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Moraru, Gheorghe; Mursa, Condrat</p> <p>2006-12-01</p> <p>In this book we present the basic concepts of the theory of <span class="hlt">elasticity</span>: stress and deformation states (plane and three-dimensional) and generalized Hooke's law. We present a number of problems which have applications in strength analysis. The book includes a synthesis of the theory of <span class="hlt">elasticity</span> and modern methods of applied mathematics. This book is designed for students, post graduate students and specialists in strength analysis. the book contains a number of appendixes which includes: elements of matrix-calculation, concepts of tensorial calculation, the Fourier transform, the notion of improper integrals,singular and hypersingular integrals, generalized functions, the Dirac Delta function</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=19780046178&hterms=kinematic+hardening&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3Dkinematic%2Bhardening','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=19780046178&hterms=kinematic+hardening&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3Dkinematic%2Bhardening"><span id="translatedtitle"><span class="hlt">Finite</span>-element analysis of crack growth under monotonic and cyclic loading</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Newman, J. C., Jr.</p> <p>1977-01-01</p> <p>An <span class="hlt">elastic</span>-plastic (incremental) <span class="hlt">finite</span>-element analysis, in conjunction with a crack-growth criterion, was used to study crack-growth behavior under monotonic and cyclic loading. The crack-growth criterion was based on crack-tip <span class="hlt">strain</span>. Whenever the crack-tip <span class="hlt">strain</span> equals or exceeds a critical <span class="hlt">strain</span> value, the crack grows. The effects of element-mesh size, critical <span class="hlt">strain</span>, <span class="hlt">strain</span> hardening, and specimen type (tension or bending) on crack growth under monotonic loading were investigated. Crack growth under cyclic loading (constant amplitude and simple variable amplitude) were also studied. A combined hardening theory, which incorporates features of both isotropic and kinematic hardening under cyclic loading, was also developed for smooth yield surfaces and was used in the analysis.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016PhyE...77..138S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016PhyE...77..138S"><span id="translatedtitle">Tunable electronic and magnetic properties of a MoS2 monolayer with vacancies under <span class="hlt">elastic</span> planar <span class="hlt">strain</span>: Ab initio study</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Salami, N.; Shokri, A. A.; Elahi, S. M.</p> <p>2016-03-01</p> <p>Electronic and magnetic properties of a molybdenum disulfide (MoS2) monolayer with some intrinsic and extrinsic vacancies are investigated using ab initio method in the presence of planar <span class="hlt">strain</span> distributions. The calculations are carried out within the density functional theory (DFT) as implemented in SIESTA package. By using fully relaxed structures and applying a full spin-polarized description to the system, we concentrate on created magnetic moment due to the vacancies under different planar <span class="hlt">strains</span>. The results show that the extrinsic MoS6 vacancy induces a net magnetic moment of 6.00 μB per supercell. Also, it is found that the pure MoS2 monolayer for the most cases does not show any magnetic properties under the planar <span class="hlt">strain</span>. While the net magnetic moment of MoS2 monolayer with the vacancies enhances as the planar tensile <span class="hlt">strain</span> is applied. The tunable magnetic moment of MoS2 monolayer may be utilized for the development of spintronic and flexible electronic nano-devices.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015APS..MARA42011D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015APS..MARA42011D"><span id="translatedtitle">Nonlinear <span class="hlt">Elasticity</span> of Bottlebrush Networks and Gels</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Dobrynin, Andrey; Cao, Zhen; Carrillo, Jan-Michael; Sheiko, Sergei</p> <p>2015-03-01</p> <p>Bottlebrush networks are examples of supersoft <span class="hlt">elastic</span> materials that demonstrate highly nonlinear stress-<span class="hlt">strain</span> behavior leading to material hardening with increasing deformation. Using molecular dynamics simulations and theoretical analysis we studied correlations between mechanical properties of bottlebrush networks and molecular parameters. Our simulations showed that both the network shear modulus G and the elongation at break decrease (onset of <span class="hlt">finite</span> extensibility) with increasing the degree of polymerization (DP) of the side chains. The <span class="hlt">finite</span> extensibility behavior is ascribed to the increase of the backbone elongation ratio β with DP of the side chains. Simulation results are in a good agreement with experimental observation of progressive softening of bottlebrush elastomers with increasing length of side chains and predictions of the nonlinear network deformation model which provides universal relationship between nonlinear network deformation modulus as a function of the first deformation invariant I1, bottlebrush backbone elongation ratio β, bottlebrush effective bending constant K and concentration of crosslinks. NSF DMR-1409710, DMR-1407645, DMR-1122483.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=19930050007&hterms=energy+2d&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3Denergy%2B2d','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=19930050007&hterms=energy+2d&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3Denergy%2B2d"><span id="translatedtitle">A method for calculating <span class="hlt">strain</span> energy release rate based on beam theory</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Sun, C. T.; Pandey, R. K.</p> <p>1993-01-01</p> <p>The Timoshenko beam theory was used to model cracked beams and to calculate the total <span class="hlt">strain</span> energy release rate. The root rotation of the beam segments at the crack tip were estimated based on an approximate 2D <span class="hlt">elasticity</span> solution. By including the <span class="hlt">strain</span> energy released due to the root rotations of the beams during crack extension, the <span class="hlt">strain</span> energy release rate obtained using beam theory agrees very well with the 2D <span class="hlt">finite</span> element solution. Numerical examples were given for various beam geometries and loading conditions. Comparisons with existing beam models were also given.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014PhRvL.112n6102I','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014PhRvL.112n6102I"><span id="translatedtitle">Wetting of <span class="hlt">Elastic</span> Solids on Nanopillars</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ignacio, M.; Saito, Y.; Smereka, P.; Pierre-Louis, O.</p> <p>2014-04-01</p> <p>Solids and liquids are both known to exhibit Cassie-Baxter states, where a drop or a solid nanoparticle is maintained on top of pillars due to wetting forces. We point out that due to <span class="hlt">elastic</span> <span class="hlt">strain</span>, solid nanocrystals exhibit a behavior different from that of liquids. First, the equilibrium Cassie-Baxter state on a single pillar exhibits a spontaneous symmetry breaking due to <span class="hlt">elastic</span> effects. The second consequence of <span class="hlt">elasticity</span> is the existence of stable partially impaled states, resulting from a compromise between wetting forces which favor impalement and <span class="hlt">elastic</span> <span class="hlt">strain</span> which resists impalement. Based on kinetic Monte Carlo simulations which include <span class="hlt">elastic</span> <span class="hlt">strain</span>, we discuss these effects and we propose a global phase diagram for the stability of nanocrystals on nanopillars.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=20060026274&hterms=Pumpkin&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3DPumpkin','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=20060026274&hterms=Pumpkin&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3DPumpkin"><span id="translatedtitle">Time-dependent <span class="hlt">strains</span> and stresses in a pumpkin balloon</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Gerngross, T.; Xu, Y.; Pellegrino, S.</p> <p>2006-01-01</p> <p>This paper presents a study of pumpkin-shaped superpressure balloons, consisting of gores made from a thin polymeric film attached to high stiffness, meridional tendons. This type of design is being used for the NASA ULDB balloons. The gore film shows considerable time-dependent stress relaxation, whereas the behaviour of the tendons is essentially time-independent. Upon inflation and pressurization, the "instantaneous", i.e. linear-<span class="hlt">elastic</span> <span class="hlt">strain</span> and stress distribution in the film show significantly higher values in the meridional direction. However, over time, and due to the biaxial visco-<span class="hlt">elastic</span> stress relaxation of the the material, the hoop <span class="hlt">strains</span> increase and the meridional stresses decrease, whereas the remaining <span class="hlt">strain</span> and stress components remain substantially unchanged. These results are important for a correct assessment of the structural integrity of a pumpkin balloon in a long-duration mission, both in terms of the material performance and the overall stability of the shape of the balloon. An experimental investigation of the time dependence of the biaxial <span class="hlt">strain</span> distribution in the film of a 4 m diameter, 48 gore pumpkin balloon is presented. The inflated shape of selected gores has been measured using photogrammetry and the time variation in <span class="hlt">strain</span> components at some particular points of these gores has been measured under constant pressure and temperature. The results show good correlation with a numerical study, using the ABAQUS <span class="hlt">finite</span>-element package, that includes a widely used model of the visco-<span class="hlt">elastic</span> response of the gore material:</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20040028029','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20040028029"><span id="translatedtitle">Significance of <span class="hlt">Strain</span> in Formulation in Theory of Solid Mechanics</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Patnaik, Surya N.; Coroneos, Rula M.; Hopkins, Dale A.</p> <p>2003-01-01</p> <p>The basic theory of solid mechanics was deemed complete circa 1860 when St. Venant provided the <span class="hlt">strain</span> formulation or the field compatibility condition. The <span class="hlt">strain</span> formulation was incomplete. The missing portion has been formulated and identified as the boundary compatibility condition (BCC). The BCC, derived through a variational formulation, has been verified through integral theorem and solution of problems. The BCC, unlike the field counterpart, do not trivialize when expressed in displacements. Navier s method and the stiffness formulation have to account for the extra conditions especially at the inter-element boundaries in a <span class="hlt">finite</span> element model. Completion of the <span class="hlt">strain</span> formulation has led to the revival of the direct force calculation methods: the Integrated Force Method (IFM) and its dual (IFMD) for <span class="hlt">finite</span> element analysis, and the completed Beltrami-Michell formulation (CBMF) in <span class="hlt">elasticity</span>. The benefits from the new methods in <span class="hlt">elasticity</span>, in <span class="hlt">finite</span> element analysis, and in design optimization are discussed. Existing solutions and computer codes may have to be adjusted for the compliance of the new conditions. Complacency because the discipline is over a century old and computer codes have been developed for half a century can lead to stagnation of the discipline.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19910006819','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19910006819"><span id="translatedtitle">Inelastic <span class="hlt">Strain</span> Analysis of Solder Joint in NASA Fatigue Specimen</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Dasgupta, Abhijit; Oyan, Chen</p> <p>1991-01-01</p> <p>The solder fatigue specimen designed by NASA-GSFC/UNISYS is analyzed in order to obtain the inelastic <span class="hlt">strain</span> history during two different representative temperature cycles specified by UNISYS. In previous reports (dated July 25, 1990, and November 15, 1990), results were presented of the <span class="hlt">elastic</span>-plastic and creep analysis for delta T = 31 C cycle, respectively. Subsequent results obtained during the current phase, from viscoplastic <span class="hlt">finite</span> element analysis of the solder fatigue specimen for delta T = 113 C cycle are summarized. Some common information is repeated for self-completeness. Large-deformation continuum formulations in conjunction with a standard linear solid model is utilized for modeling the solder constitutive creep-plasticity behavior. Relevant material properties are obtained from the literature. <span class="hlt">Strain</span> amplitudes, mean <span class="hlt">strains</span>, and residual <span class="hlt">strains</span> (as well as stresses) accumulated due to a representative complete temperature cycle are obtained as a result of this analysis. The partitioning between <span class="hlt">elastic</span> <span class="hlt">strains</span>, time-independent inelastic (plastic) <span class="hlt">strains</span>, and time-dependent inelastic (creep) <span class="hlt">strains</span> is also explicitly obtained for two representative cycles. Detailed plots are presented for two representative temperature cycles. This information forms an important input for fatigue damage models, when predicting the fatigue life of solder joints under thermal cycling</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_24");'>24</a></li> <li class="active"><span>25</span></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_25 --> <center> <div class="footer-extlink text-muted"><small>Some links on this page may take you to non-federal websites. 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