Conceptual finite element study for comparison among superior, anterior, and spiral clavicle plate fixations for midshaft clavicle fracture.

PubMed

Huang, Teng-Le; Chen, Wen-Chuan; Lin, Kun-Jhih; Tsai, Cheng-Lun; Lin, Kang-Ping; Wei, Hung-Wen

2016-10-01

Open reduction internal fixation technique has been generally accepted for treatment of midshaft clavicle fractures. Both superior and anterior clavicle plates have been reported in clinical or biomechanical researches, while presently the spiral clavicle plate design has been introduced improved biomechanical behavior over conventional designs. In order to objectively realize the multi-directional biomechanical performances among the three geometries for clavicle plate designs, a current conceptual finite element study has been conducted with identical cross-sectional features for clavicle plates. The conceptual superior, anterior, and spiral clavicle plate models were constructed for virtual reduction and fixation to an OTA 15-B1.3 midshaft transverse fracture of clavicle. Mechanical load cases including cantilever bending, axial compression, inferior bending, and axial torsion have been applied for confirming the multi-directional structural stability and implant safety in biomechanical perspective. Results revealed that the anterior clavicle plate model represented lowest plate stress under all loading cases. The superior clavicle plate model showed greater axial compressive stiffness, while the anterior clavicle plate model performed greater rigidity under cantilever bending load. Three model represented similar structural stiffness under axial torsion. Played as a transition structure between superior and anterior clavicle plate, the spiral clavicle plate model revealed comparable results with acceptable multi-directional biomechanical behavior. The concept of spiral clavicle plate design is worth considering in practical application in clinics. Implant safety should be further investigated by evidences in future mechanical tests and clinical observations. Copyright © 2016 IPEM. Published by Elsevier Ltd. All rights reserved.

A refined shear deformation theory for the analysis of laminated plates

NASA Technical Reports Server (NTRS)

Reddy, J. N.

1986-01-01

A refined, third-order plate theory that accounts for the transverse shear strains is presented, the Navier solutions are derived for certain simply supported cross-ply and antisymmetric angle-ply laminates, and finite-element models are developed for general laminates. The new theory does not require the shear correction factors of the first-order theory (i.e., the Reissner-Mindlin plate theory) because the transverse shear stresses are represented parabolically in the present theory. A mixed finite-element model that uses independent approximations of the generalized displacements and generalized moments, and a displacement model that uses only the generalized displacements as degrees of freedom are developed. The displacement model requires C sup 1-continuity of the transverse deflection across the inter-element boundaries, whereas the mixed model requires a C sup 0-element. Also, the mixed model does not require continuous approximations (between elements) of the bending moments. Numerical results are presented to show the accuracy of the present theory in predicting the transverse stresses. Numerical results are also presented for the nonlinear bending of plates, and the results compare well with the experimental results available in the literature.

Layerwise Finite Elements for Smart Piezoceramic Composite Plates in Thermal Environments

NASA Technical Reports Server (NTRS)

Saravanos, Dimitris A.; Lee, Ho-Jun

1996-01-01

Analytical formulations are presented which account for the coupled mechanical, electrical, and thermal response of piezoelectric composite laminates and plate structures. A layerwise theory is formulated with the inherent capability to explicitly model the active and sensory response of piezoelectric composite plates having arbitrary laminate configurations in thermal environments. Finite element equations are derived and implemented for a bilinear 4-noded plate element. Application cases demonstrate the capability to manage thermally induced bending and twisting deformations in symmetric and antisymmetric composite plates with piezoelectric actuators, and show the corresponding electrical response of distributed piezoelectric sensors. Finally, the resultant stresses in the thermal piezoelectric composite laminates are investigated.

A Low Frequency FBG Accelerometer with Symmetrical Bended Spring Plates.

PubMed

Liu, Fufei; Dai, Yutang; Karanja, Joseph Muna; Yang, Minghong

2017-01-22

To meet the requirements for low-frequency vibration monitoring, a new type of FBG (fiber Bragg grating) accelerometer with a bended spring plate is proposed. Two symmetrical bended spring plates are used as elastic elements, which drive the FBG to produce axial strains equal in magnitude but opposite in direction when exciting vibrations exist, leading to doubling the wavelength shift of the FBG. The mechanics model and a numerical method are presented in this paper, with which the influence of the structural parameters on the sensitivity and the eigenfrequency are discussed. The test results show that the sensitivity of the accelerometer is more than 1000 pm/g when the frequency is within the 0.7-20 Hz range.

Development of quadrilateral spline thin plate elements using the B-net method

NASA Astrophysics Data System (ADS)

Chen, Juan; Li, Chong-Jun

2013-08-01

The quadrilateral discrete Kirchhoff thin plate bending element DKQ is based on the isoparametric element Q8, however, the accuracy of the isoparametric quadrilateral elements will drop significantly due to mesh distortions. In a previouswork, we constructed an 8-node quadrilateral spline element L8 using the triangular area coordinates and the B-net method, which can be insensitive to mesh distortions and possess the second order completeness in the Cartesian coordinates. In this paper, a thin plate spline element is developed based on the spline element L8 and the refined technique. Numerical examples show that the present element indeed possesses higher accuracy than the DKQ element for distorted meshes.

A closed form large deformation solution of plate bending with surface effects.

PubMed

Liu, Tianshu; Jagota, Anand; Hui, Chung-Yuen

2017-01-04

We study the effect of surface stress on the pure bending of a finite thickness plate under large deformation. The surface is assumed to be isotropic and its stress consists of a part that can be interpreted as a residual stress and a part that stiffens as the surface increases its area. Our results show that residual surface stress and surface stiffness can both increase the overall bending stiffness but through different mechanisms. For sufficiently large residual surface tension, we discover a new type of instability - the bending moment reaches a maximum at a critical curvature. Effects of surface stress on different stress components in the bulk of the plate are discussed and the possibility of self-bending due to asymmetry of the surface properties is also explored. The results of our calculations provide insights into surface stress effects in the large deformation regime and can be used as a test for implementation of finite element methods for surface elasticity.

Titanium Elastic Nail (TEN) versus Reconstruction Plate Repair of Midshaft Clavicular Fractures: A Finite Element Study

PubMed Central

Liu, Yanjie; Zhang, Wen; Pan, Yao; Zhang, Wei; Zhang, Changqing; Zeng, Bingfang; Chen, Yunfeng

2015-01-01

Background The biomechanical characteristics of midshaft clavicular fractures treated with titanium elastic nail (TEN) is unclear. This study aimed to present a biomechanical finite element analysis of biomechanical characteristics involved in TEN fixation and reconstruction plate fixation for midshaft clavicular fractures. Methods Finite element models of the intact clavicle and of midshaft clavicular fractures fixed with TEN and with a reconstruction plate were built. The distal clavicle displacement, peak stress, and stress distribution on the 3 finite element models were calculated under the axial compression and cantilever bending. Results In both loading configurations, TEN generated the highest displacement of the distal clavicle, followed by the intact clavicle and the reconstruction plate. TEN showed higher peak bone and implant stresses, and is more likely to fail in both loading configurations compared with the reconstruction plate. TEN led to a stress distribution similar to that of the intact clavicle in both loading configurations, whereas the stress distribution with the reconstruction plate was nonphysiological in cantilever bending. Conclusions TEN is generally preferable for treating simple displaced fractures of the midshaft clavicle, because it showed a stress distribution similar to the intact clavicle. However, TEN provides less stability, and excessive exercise of and weight bearing on the ipsilateral shoulder should be avoided in the early postoperative period. Fixation with a reconstruction plate was more stable but showed obvious stress shielding. Therefore, for patients with a demand for early return to activity, reconstruction plate fixation may be preferred. PMID:25965409

Three-dimensional microarchitecture of the plates (primary, secondary, and carinar process) in the developing tooth of Lytechinus variegatus revealed by synchrotron X-ray absorption microtomography (microCT).

PubMed

Stock, S R; Ignatiev, K I; Dahl, T; Veis, A; De Carlo, F

2003-12-01

This paper reports the first noninvasive, volumetric study of entire cross-sections of a sea urchin tooth in which the individual calcite structural elements could be resolved. Two cross-sectionally intact fragments of a Lytechinus variegatus tooth were studied with synchrotron microCT (microcomputed tomography) with 1.66 microm voxels (volume elements). These fragments were from the plumula, that is the tooth zone with rapidly increasing levels of mineral; one fragment was from a position aboral of where the keel developed and the second was from the zone where the keel was developing. The primary plates, secondary plates, carinar process plates, prisms, and elements of the lamellar-needle complex were resolved. Comparison of the microCT data with optical micrographs of stained thin sections confirmed the identifications and measured dimensions of the characteristic microarchitectural features. The interplay of reinforcing structures (plates and prisms) was more clearly revealed in the volumetric numerical data sets than in single or sequential slices. While it is well known that the primary plates and prisms in camarodont teeth are situated to improve resistance to bending (which can be termed primary bending), the data presented provide a new understanding of the mechanical role of the carinar process plates, that is, a geometry consistent with that required in the keel to resist lateral or transverse bending of the tooth about a second axis. The increase in robustness of teeth incorporating lateral keel reinforcement suggests that the relative development of carinar processes (toward a geometry similar to that of L. variegatus) is a character which can be used to infer which sea urchins among the stirodonts are most primitive and among the camarodonts which are more primitive.

Effect of Plate Hardening Behavior on the Deformation of Stainless Steel Metal Bellows

NASA Astrophysics Data System (ADS)

Hao, Zengliang; Luo, Shuyi; Zhao, He; Zhang, Chunxiang; Luo, Junting

2017-11-01

Tensile tests of original plate samples from three types of stainless steel metal bellows were performed at room temperature. The constitutive equations for the three hardening curves were obtained and fitted. The analysis results of the microstructure and fracture morphology of the tensile specimens show that the grain size of the plate with a high logarithmic-exponential hardening rate is uneven and the dimple of the shear fracture is elongated into an ellipse. By contrast, the grain size of the plate with a relatively low linear hardening rate is even and the dimple of the fracture is uniformly equiaxial. Finite element simulations of the hydraulic bulging and repeated limit bending deformation of the metal bellows of the three types of materials were also conducted. The repeated limit bending deformation process was tested experimentally. Although the effect of the hardening exponent on the residual stress of the metal bellows after hydraulic bulging is minimal, this exponent considerably influences the repeated limit bending deformation of the metal bellows after subsequent use. The trough hardening phenomenon is serious in the repeated limit bending process. Moreover, when the hardening exponent of the original plate is high, the resistance to bending fracture at the trough area is poor.

Piezoelectrostatic generator

NASA Technical Reports Server (NTRS)

Robertson, Glen A. (Inventor)

1990-01-01

A piezoelectrostatic generator includes a plurality of elongated piezoelectric elements having first and second ends, with the first ends fixedly mounted in a cylindrical housing and the second extending radially inwardly toward an axis. A shaft movable along the axis is connected to the inner ends of the elements to produce bending forces in piezoelectric strips within the elements. Each element includes a pair of strips mounted in surface contact and in electrical series to produce a potential upon bending. Electrodes spaced from the strips by a solid dielectric material act as capacitor plates to collect the potential charge.

A refined mixed shear flexible finite element for the nonlinear analysis of laminated plates

NASA Technical Reports Server (NTRS)

Putcha, N. S.; Reddy, J. N.

1986-01-01

The present study is concerned with the development of a mixed shear flexible finite element with relaxed continuity for the geometrically linear and nonlinear analysis of laminated anisotropic plates. The formulation of the element is based on a refined higher-order theory. This theory satisfies the zero transverse shear stress boundary conditions on the top and bottom faces of the plate. Shear correction coefficients are not needed. The developed element consists of 11 degrees-of-freedom per node, taking into account three displacements, two rotations, and six moment resultants. An evaluation of the element is conducted with respect to the accuracy obtained in the bending of laminated anistropic rectangular plates with different lamination schemes, loadings, and boundary conditions.

Deflection of cross-ply composite laminates induced by piezoelectric actuators.

PubMed

Her, Shiuh-Chuan; Lin, Chi-Sheng

2010-01-01

The coupling effects between the mechanical and electric properties of piezoelectric materials have drawn significant attention for their potential applications as sensors and actuators. In this investigation, two piezoelectric actuators are symmetrically surface bonded on a cross-ply composite laminate. Electric voltages with the same amplitude and opposite sign are applied to the two symmetric piezoelectric actuators, resulting in the bending effect on the laminated plate. The bending moment is derived by using the classical laminate theory and piezoelectricity. The analytical solution of the flexural displacement of the simply supported composite plate subjected to the bending moment is solved by using the plate theory. The analytical solution is compared with the finite element solution to show the validation of present approach. The effects of the size and location of the piezoelectric actuators on the response of the composite laminate are presented through a parametric study. A simple model incorporating the classical laminate theory and plate theory is presented to predict the deformed shape of the simply supported laminate plate.

Surface crack problems in plates

NASA Technical Reports Server (NTRS)

Joseph, P. F.; Erdogan, F.

1989-01-01

The mode I crack problem in plates under membrane loading and bending is reconsidered. The purpose is to examine certain analytical features of the problem further and to provide some new results. The formulation and the results given by the classical and the Reissner plate theories for through and part-through cracks are compared. For surface cracks the three-dimensional finite element solution is used as the basis of comparison. The solution is obtained and results are given for the crack/contact problem in a plate with a through crack under pure bending and for the crack interaction problem. Also, a procedure is developed to treat the problem of subcritical crack growth and to trace the evolution of the propagating crack.

Numerical Manifold Method for the Forced Vibration of Thin Plates during Bending

PubMed Central

Jun, Ding; Song, Chen; Wei-Bin, Wen; Shao-Ming, Luo; Xia, Huang

2014-01-01

A novel numerical manifold method was derived from the cubic B-spline basis function. The new interpolation function is characterized by high-order coordination at the boundary of a manifold element. The linear elastic-dynamic equation used to solve the bending vibration of thin plates was derived according to the principle of minimum instantaneous potential energy. The method for the initialization of the dynamic equation and its solution process were provided. Moreover, the analysis showed that the calculated stiffness matrix exhibited favorable performance. Numerical results showed that the generalized degrees of freedom were significantly fewer and that the calculation accuracy was higher for the manifold method than for the conventional finite element method. PMID:24883403

Developments in variational methods for high performance plate and shell elements

NASA Technical Reports Server (NTRS)

Felippa, Carlos A.; Militello, Carmelo

1991-01-01

High performance elements are simple finite elements constructed to deliver engineering accuracy with coarse arbitrary grids. This is part of a series on the variational foundations of high-performance elements, with emphasis on plate and shell elements constructed with the free formulation (FF) and assumed natural strain (ANS) methods. Parameterized variational principles are studied that provide a common foundation for the FF and ANS methods, as well as for a combination of both. From this unified formulation a variant of the ANS formulation, called the assumed natural deviatoric strain (ANDES) formulation, emerges as an important special case. The first ANDES element, a high-performance 9 degrees of freedom triangular Kirchhoff plate bending element, is briefly described to illustrate the use of the new formulation.

Line-spring model for surface cracks in a Reissner plate

NASA Technical Reports Server (NTRS)

Delale, F.; Erdogan, F.

1981-01-01

In this paper the line-spring model developed by Rice and Levy for a surface crack in elastic plates is reconsidered. The problem is formulated by using Reissner's plate bending theory. For the plane strain problem of a strip containing an edge crack and subjected to tension and bending new expressions for stress intensity factors are used which are valid up to a depth-to-thickness ratio of 0.8. The stress intensity factors for a semi-elliptic and a rectangular crack are calculated. Considering the simplicity of the technique and the severity of the underlying assumptions, the results compare rather well with the existing finite element solutions.

A theory for the fracture of thin plates subjected to bending and twisting moments

NASA Technical Reports Server (NTRS)

Hui, C. Y.; Zehnder, Alan T.

1993-01-01

Stress fields near the tip of a through crack in an elastic plate under bending and twisting moments are reviewed assuming both Kirchhoff and Reissner plate theories. The crack tip displacement and rotation fields based on the Reissner theory are calculated. These results are used to calculate the J-integral (energy release rate) for both Kirchhoff and Reissner plate theories. Invoking Simmonds and Duva's (1981) result that the value of the J-integral based on either theory is the same for thin plates, a universal relationship between the Kirchhoff theory stress intensity factors and the Reissner theory stress intensity factors is obtained for thin plates. Calculation of Kirchhoff theory stress intensity factors from finite elements based on energy release rate is illustrated. It is proposed that, for thin plates, fracture toughness and crack growth rates be correlated with the Kirchhoff theory stress intensity factors.

Large-displacement structural durability analyses of simple bend specimen emulating rocket nozzle liners

NASA Technical Reports Server (NTRS)

Arya, Vinod K.; Halford, Gary R.

1994-01-01

Large-displacement elastic and elastic-plastic, finite-element stress-strain analyses of an oxygen-tree high-conductivity (OFHC) copper plate specimen were performed using an updated Lagrangian formulation. The plate specimen is intended for low-cost experiments that emulate the most important thermomechanical loading and failure modes of a more complex rocket nozzle. The plate, which is loaded in bending at 593 C, contains a centrally located and internally pressurized channel. The cyclic crack initiation lives were estimated using the results from the analyses and isothermal strain-controlled low-cycle fatigue data for OFHC copper. A comparison of the predicted and experimental cyclic lives showed that an elastic analysis predicts a longer cyclic life than that observed in experiments by a factor greater than 4. The results from elastic-plastic analysis for the plate bend specimen, however, predicted a cyclic life in close agreement with experiment, thus justifying the need for the more rigorous stress-strain analysis.

Anatomical Thin Titanium Mesh Plate Structural Optimization for Zygomatic-Maxillary Complex Fracture under Fatigue Testing.

PubMed

Wang, Yu-Tzu; Huang, Shao-Fu; Fang, Yu-Ting; Huang, Shou-Chieh; Cheng, Hwei-Fang; Chen, Chih-Hao; Wang, Po-Fang; Lin, Chun-Li

2018-01-01

This study performs a structural optimization of anatomical thin titanium mesh (ATTM) plate and optimal designed ATTM plate fabricated using additive manufacturing (AM) to verify its stabilization under fatigue testing. Finite element (FE) analysis was used to simulate the structural bending resistance of a regular ATTM plate. The Taguchi method was employed to identify the significance of each design factor in controlling the deflection and determine an optimal combination of designed factors. The optimal designed ATTM plate with patient-matched facial contour was fabricated using AM and applied to a ZMC comminuted fracture to evaluate the resting maxillary micromotion/strain under fatigue testing. The Taguchi analysis found that the ATTM plate required a designed internal hole distance to be 0.9 mm, internal hole diameter to be 1 mm, plate thickness to be 0.8 mm, and plate height to be 10 mm. The designed plate thickness factor primarily dominated the bending resistance up to 78% importance. The averaged micromotion (displacement) and strain of the maxillary bone showed that ZMC fracture fixation using the miniplate was significantly higher than those using the AM optimal designed ATTM plate. This study concluded that the optimal designed ATTM plate with enough strength to resist the bending effect can be obtained by combining FE and Taguchi analyses. The optimal designed ATTM plate with patient-matched facial contour fabricated using AM provides superior stabilization for ZMC comminuted fractured bone segments.

A higher-order theory for geometrically nonlinear analysis of composite laminates

NASA Technical Reports Server (NTRS)

Reddy, J. N.; Liu, C. F.

1987-01-01

A third-order shear deformation theory of laminated composite plates and shells is developed, the Navier solutions are derived, and its finite element models are developed. The theory allows parabolic description of the transverse shear stresses, and therefore the shear correction factors of the usual shear deformation theory are not required in the present theory. The theory also accounts for the von Karman nonlinear strains. Closed-form solutions of the theory for rectangular cross-ply and angle-ply plates and cross-ply shells are developed. The finite element model is based on independent approximations of the displacements and bending moments (i.e., mixed finite element model), and therefore, only C sup o -approximation is required. The finite element model is used to analyze cross-ply and angle-ply laminated plates and shells for bending and natural vibration. Many of the numerical results presented here should serve as references for future investigations. Three major conclusions resulted from the research: First, for thick laminates, shear deformation theories predict deflections, stresses and vibration frequencies significantly different from those predicted by classical theories. Second, even for thin laminates, shear deformation effects are significant in dynamic and geometrically nonlinear analyses. Third, the present third-order theory is more accurate compared to the classical and firt-order theories in predicting static and dynamic response of laminated plates and shells made of high-modulus composite materials.

Notch sensitivity jeopardizes titanium locking plate fatigue strength.

PubMed

Tseng, Wo-Jan; Chao, Ching-Kong; Wang, Chun-Chin; Lin, Jinn

2016-12-01

Notch sensitivity may compromise titanium-alloy plate fatigue strength. However, no studies providing head-to-head comparisons of stainless-steel or titanium-alloy locking plates exist. Custom-designed identically structured locking plates were made from stainless steel (F138 and F1314) or titanium alloy. Three screw-hole designs were compared: threaded screw-holes with angle edges (type I); threaded screw-holes with chamfered edges (type II); and non-threaded screw-holes with chamfered edges (type III). The plates' bending stiffness, bending strength, and fatigue life, were investigated. The stress concentration at the screw threads was assessed using finite element analyses (FEA). The titanium plates had higher bending strength than the F1314 and F138 plates (2.95:1.56:1) in static loading tests. For all metals, the type-III plate fatigue life was highest, followed by type-II and type-I. The type-III titanium plates had longer fatigue lives than their F138 counterparts, but the type-I and type-II titanium plates had significantly shorter fatigue lives. All F1314 plate types had longer fatigue lives than the type-III titanium plates. The FEA showed minimal stress difference (0.4%) between types II and III, but the stress for types II and III was lower (11.9% and 12.4%) than that for type I. The screw threads did not cause stress concentration in the locking plates in FEA, but may have jeopardized the fatigue strength, especially in the notch-sensitive titanium plates. Improvement to the locking plate design is necessary. Copyright © 2016 Elsevier Ltd. All rights reserved.

A geometric nonlinear degenerated shell element using a mixed formulation with independently assumed strain fields. Final Report; Ph.D. Thesis, 1989

NASA Technical Reports Server (NTRS)

Graf, Wiley E.

1991-01-01

A mixed formulation is chosen to overcome deficiencies of the standard displacement-based shell model. Element development is traced from the incremental variational principle on through to the final set of equilibrium equations. Particular attention is paid to developing specific guidelines for selecting the optimal set of strain parameters. A discussion of constraint index concepts and their predictive capability related to locking is included. Performance characteristics of the elements are assessed in a wide variety of linear and nonlinear plate/shell problems. Despite limiting the study to geometric nonlinear analysis, a substantial amount of additional insight concerning the finite element modeling of thin plate/shell structures is provided. For example, in nonlinear analysis, given the same mesh and load step size, mixed elements converge in fewer iterations than equivalent displacement-based models. It is also demonstrated that, in mixed formulations, lower order elements are preferred. Additionally, meshes used to obtain accurate linear solutions do not necessarily converge to the correct nonlinear solution. Finally, a new form of locking was identified associated with employing elements designed for biaxial bending in uniaxial bending applications.

Optimum structural design with plate bending elements - A survey

NASA Technical Reports Server (NTRS)

Haftka, R. T.; Prasad, B.

1981-01-01

A survey is presented of recently published papers in the field of optimum structural design of plates, largely with respect to the minimum-weight design of plates subject to such constraints as fundamental frequency maximization. It is shown that, due to the availability of powerful computers, the trend in optimum plate design is away from methods tailored to specific geometry and loads and toward methods that can be easily programmed for any kind of plate, such as finite element methods. A corresponding shift is seen in optimization from variational techniques to numerical optimization algorithms. Among the topics covered are fully stressed design and optimality criteria, mathematical programming, smooth and ribbed designs, design against plastic collapse, buckling constraints, and vibration constraints.

Stress-intensity factors for small surface and corner cracks in plates

NASA Technical Reports Server (NTRS)

Raju, I. S.; Atluri, S. N.; Newman, J. C., Jr.

1988-01-01

Three-dimensional finite-element and finite-alternating methods were used to obtain the stress-intensity factors for small surface and corner cracked plates subjected to remote tension and bending loads. The crack-depth-to-crack-length ratios (a/c) ranged from 0.2 to 1 and the crack-depth-to-plate-thickness ratios (a/t) ranged from 0.05 to 0.2. The performance of the finite-element alternating method was studied on these crack configurations. A study of the computational effort involved in the finite-element alternating method showed that several crack configurations could be analyzed with a single rectangular mesh idealization, whereas the conventional finite-element method requires a different mesh for each configuration. The stress-intensity factors obtained with the finite-element-alternating method agreed well (within 5 percent) with those calculated from the finite-element method with singularity elements.

Sensitivity studies of pediatric material properties on juvenile lumbar spine responses using finite element analysis.

PubMed

Jebaseelan, D Davidson; Jebaraj, C; Yoganandan, Narayan; Rajasekaran, S; Kanna, Rishi M

2012-05-01

The objective of the study was to determine the sensitivity of material properties of the juvenile spine to its external and internal responses using a finite element model under compression, and flexion-extension bending moments. The methodology included exercising the 8-year-old juvenile lumbar spine using parametric procedures. The model included the vertebral centrum, growth plates, laminae, pedicles, transverse processes and spinous processes; disc annulus and nucleus; and various ligaments. The sensitivity analysis was conducted by varying the modulus of elasticity for various components. The first simulation was done using mean material properties. Additional simulations were done for each component corresponding to low and high material property variations. External displacement/rotation and internal stress-strain responses were determined under compression and flexion-extension bending. Results indicated that, under compression, disc properties were more sensitive than bone properties, implying an elevated role of the disc under this mode. Under flexion-extension moments, ligament properties were more dominant than the other components, suggesting that various ligaments of the juvenile spine play a key role in modulating bending behaviors. Changes in the growth plate stress associated with ligament properties explained the importance of the growth plate in the pediatric spine with potential implications in progressive deformities.

Shear-flexible finite-element models of laminated composite plates and shells

NASA Technical Reports Server (NTRS)

Noor, A. K.; Mathers, M. D.

1975-01-01

Several finite-element models are applied to the linear static, stability, and vibration analysis of laminated composite plates and shells. The study is based on linear shallow-shell theory, with the effects of shear deformation, anisotropic material behavior, and bending-extensional coupling included. Both stiffness (displacement) and mixed finite-element models are considered. Discussion is focused on the effects of shear deformation and anisotropic material behavior on the accuracy and convergence of different finite-element models. Numerical studies are presented which show the effects of increasing the order of the approximating polynomials, adding internal degrees of freedom, and using derivatives of generalized displacements as nodal parameters.

Calculation of the bending of electromechanical aircraft element made of the carbon fiber

NASA Astrophysics Data System (ADS)

Danilova-Volkovskaya, Galina; Chepurnenko, Anton; Begak, Aleksandr; Savchenko, Andrey

2017-10-01

We consider a method of calculation of an orthotropic plate with variable thickness. The solution is performed numerically by the finite element method. The calculation is made for the springs of a hang glider made of carbon fiber. The comparison of the results with Sofistik software complex is given.

Biomechanical comparison of straight and helical compression plates for fixation of transverse and oblique bone fractures: Modeling and experiments.

PubMed

Sezek, Sinan; Aksakal, Bunyamin; Gürger, Murat; Malkoc, Melih; Say, Y

2016-08-12

Total deformation and stability of straight and helical compression plates were studied by means of the finite element method (FEM) and in vitro biomechanical experiments. Fixations of transverse (TF) and oblique (45°) bone (OF) fractures have been analyzed on sheep tibias by designing the straight compression (SP) and Helical Compression Plate (HP) models. The effects of axial compression, bending and torsion loads on both plating systems were analyzed in terms of total displacements. Numerical models and experimental models suggested that under compression loadings, bone fracture gap closures for both fracture types were found to be in the favor of helical plate designs. The helical plate (HP) fixations provided maximum torsional resistance compared to the (SP) fixations. The fracture gap closure and stability of helical plate fixation for transverse fractures was determined to be higher than that found for the oblique fractures. The comparison of average compression stress, bending and torsion moments showed that the FEM and experimental results are in good agreement and such designs are likely to have a positive impact in future bone fracture fixation designs.

A new multipartite plate system for anterior cervical spine surgery; finite element analysis.

PubMed

Şimşek, Hakan; Zorlu, Emre; Kaya, Serdar; Baydoğan, Murat; Atabey, Cem; Çolak, Ahmet

2017-12-19

There are numerous available plates, almost all of which are compact one-piece plates. During the placement of relatively long plates in the treatment of multi-level cervical pathologies, instrument related complications might appear. In order to overcome this potential problem, a novel 'articulated plate system' is designed. We aimed to delineate finite element analysis and mechanical evaluations. A new plate system consisting of multi partite structure for anterior cervical stabilization was designed. Segmental plates were designed for application onto the ventral surface of the vertebral body. Plates differed from 9 to13 mm in length. There are rods at one end and hooks at the other end. Terminal points consisted of either hooks or rods at one end but the other ends are blind. Finite element and mechanical tests of the construct were performed applying bending, axial loading, and distraction forces. Finite element and mechanical testing results yielded the cut off values for functional failure and breakage of the system. The articulated system proved to be mechanically safe and it lets extension of the system on either side as needed. Ease of application needs further verification via a cadaveric study.

Theoretical prediction on corrugated sandwich panels under bending loads

NASA Astrophysics Data System (ADS)

Shu, Chengfu; Hou, Shujuan

2018-05-01

In this paper, an aluminum corrugated sandwich panel with triangular core under bending loads was investigated. Firstly, the equivalent material parameters of the triangular corrugated core layer, which could be considered as an orthotropic panel, were obtained by using Castigliano's theorem and equivalent homogeneous model. Secondly, contributions of the corrugated core layer and two face panels were both considered to compute the equivalent material parameters of the whole structure through the classical lamination theory, and these equivalent material parameters were compared with finite element analysis solutions. Then, based on the Mindlin orthotropic plate theory, this study obtain the closed-form solutions of the displacement for a corrugated sandwich panel under bending loads in specified boundary conditions, and parameters study and comparison by the finite element method were executed simultaneously.

Experimental and simulation study of flexural behaviour of woven Glass/Epoxy laminated composite plate

NASA Astrophysics Data System (ADS)

Sahoo, Sushree S.; Singh, Vijay K.; Panda, Subrata K.

2015-02-01

Flexural behaviour of cross ply laminated woven Glass/Epoxy composite plate has been investigated in this article. Flexural responses are examined by a three point bend test and tensile test carried out on INSTRON 5967 and Universal Testing Machine INSTRON 1195 respectively. The finite element model is developed in ANSYS parametric design language code and discretised using an eight nodded structural shell element. Convergence behaviour of the simulation result has been performed and validated by comparing the results with experimental values. The effects of various parameters such as side-to-thickness ratio, modular ratio on flexural behaviour of woven Glass/Epoxy laminated composite plate are discussed in details.

Assessment of carbon fibre composite fracture fixation plate using finite element analysis.

PubMed

Saidpour, Seyed H

2006-07-01

In the internal fixation of fractured bone by means of bone-plates fastened to the bone on its tensile surface, an on-going concern has been the excessive stress shielding of the bone by the excessively-stiff stainless-steel plate. The compressive stress shielding at the fracture-interface immediately after fracture-fixation delays callus formation and bone healing. Likewise, the tensile stress shielding in the layer of bone underneath the plate can cause osteoporosis and decrease in tensile strength of this layer. In this study a novel forearm internal fracture fixation plate made from short carbon fibre reinforced plastic (CFRP) was used in an attempt to address the problem. Accordingly, it has been possible to analyse the stress distribution in the composite plates using finite-element modelling. A three-dimensional, quarter-symmetric finite element model was generated for the plate system. The stress state in the underlying bone was examined for several loading conditions. Based on the analytical results the composite plate system is likely to reduce stress-shielding effects at the fracture site when subjected to bending and torsional loads. The design of the plate was further optimised by reducing the width around the innermost holes.

A simple and efficient shear-flexible plate bending element

NASA Technical Reports Server (NTRS)

Chaudhuri, Reaz A.

1987-01-01

A shear-flexible triangular element formulation, which utilizes an assumed quadratic displacement potential energy approach and is numerically integrated using Gauss quadrature, is presented. The Reissner/Mindlin hypothesis of constant cross-sectional warping is directly applied to the three-dimensional elasticity theory to obtain a moderately thick-plate theory or constant shear-angle theory (CST), wherein the middle surface is no longer considered to be the reference surface and the two rotations are replaced by the two in-plane displacements as nodal variables. The resulting finite-element possesses 18 degrees of freedom (DOF). Numerical results are obtained for two different numerical integration schemes and a wide range of meshes and span-to-thickness ratios. These, when compared with available exact, series or finite-element solutions, demonstrate accuracy and rapid convergence characteristics of the present element. This is especially true in the case of thin to very thin plates, when the present element, used in conjunction with the reduced integration scheme, outperforms its counterpart, based on discrete Kirchhoff constraint theory (DKT).

Design Methods for Load-bearing Elements from Crosslaminated Timber

NASA Astrophysics Data System (ADS)

Vilguts, A.; Serdjuks, D.; Goremikins, V.

2015-11-01

Cross-laminated timber is an environmentally friendly material, which possesses a decreased level of anisotropy in comparison with the solid and glued timber. Cross-laminated timber could be used for load-bearing walls and slabs of multi-storey timber buildings as well as decking structures of pedestrian and road bridges. Design methods of cross-laminated timber elements subjected to bending and compression with bending were considered. The presented methods were experimentally validated and verified by FEM. Two cross-laminated timber slabs were tested at the action of static load. Pine wood was chosen as a board's material. Freely supported beam with the span equal to 1.9 m, which was loaded by the uniformly distributed load, was a design scheme of the considered plates. The width of the plates was equal to 1 m. The considered cross-laminated timber plates were analysed by FEM method. The comparison of stresses acting in the edge fibres of the plate and the maximum vertical displacements shows that both considered methods can be used for engineering calculations. The difference between the results obtained experimentally and analytically is within the limits from 2 to 31%. The difference in results obtained by effective strength and stiffness and transformed sections methods was not significant.

Three-dimensional finite element analysis of occipitocervical fixation using an anterior occiput-to-axis locking plate system: a pilot study.

PubMed

Cai, Xianhua; Yu, Yang; Liu, Zhichao; Zhang, Meichao; Huang, Weibing

2014-08-01

Although there are many techniques for occipitocervical fixation, there have been no reports regarding occipitocervical fixation via the use of an anterior anatomical locking plate system. The biomechanics of this new system were analyzed by a three-dimensional finite element to provide a theoretical basis for clinical application. This was a modeling study. We studied a 27-year-old healthy male volunteer in whom cervical disease was excluded via X-ray examination. The states of stress and strain of these two internal fixation devices were analyzed. A three-dimensional finite element model of normal occiput-C2 was established based on the anatomical data from a Chinese population. An unstable model of occipital-cervical region was established by subtracting several unit structures from the normal model. An anterior occiput-to-axis locking titanium plate system was then applied and an anterior occiput-to-axis screw fixation was performed on the unstable model. Limitation of motion was performed on the surface of the fixed model, and physiological loads were imposed on the surface of the skull base. Under various loads from different directions, the peak values of displacement of the anterior occiput-to-axis locking titanium plate system decreased 15.5%, 12.5%, 14.4%, and 23.7%, respectively, under the loads of flexion, extension, lateral bending, and axial rotation. Compared with the anterior occiput-to-axis screw fixation, the peak values of stress of the anterior occiput-to-axis locking titanium plate system also decreased 3.9%, 2.9%, 9.7%, and 7.2%, respectively, under the loads of flexion, extension, lateral bending, and axial rotation. The anterior occiput-to-axis locking titanium plate system proved superior to the anterior occiput-to-axis screw system both in the stress distribution and fixation stability based on finite element analysis. It provides a new clinical option for anterior occipitocervical fixation. Copyright © 2014 Elsevier Inc. All rights reserved.

Magnetostrictive clad steel plates for high-performance vibration energy harvesting

NASA Astrophysics Data System (ADS)

Yang, Zhenjun; Nakajima, Kenya; Onodera, Ryuichi; Tayama, Tsuyoki; Chiba, Daiki; Narita, Fumio

2018-02-01

Energy harvesting technology is becoming increasingly important with the appearance of the Internet of things. In this study, a magnetostrictive clad steel plate for harvesting vibration energy was proposed. It comprises a cold-rolled FeCo alloy and cold-rolled steel joined together by thermal diffusion bonding. The performances of the magnetostrictive FeCo clad steel plate and conventional FeCo plate cantilevers were compared under bending vibration; the results indicated that the clad steel plate construct exhibits high voltage and power output compared to a single-plate construct. Finite element analysis of the cantilevers under bending provided insights into the magnetic features of a clad steel plate, which is crucial for its high performance. For comparison, the experimental results of a commercial piezoelectric bimorph cantilever were also reported. In addition, the cold-rolled FeCo and Ni alloys were joined by thermal diffusion bonding, which exhibited outstanding energy harvesting performance. The larger the plate volume, the more the energy generated. The results of this study indicated not only a promising application for the magnetostrictive FeCo clad steel plate as an efficient energy harvester, related to small vibrations, but also the notable feasibility for the formation of integrated units to support high-power trains, automobiles, and electric vehicles.

Analysis of bending wave transmission using beam tracing with advanced statistical energy analysis for periodic box-like structures affected by spatial filtering

NASA Astrophysics Data System (ADS)

Wilson, D.; Hopkins, C.

2015-04-01

For bending wave transmission across periodic box-like arrangements of plates, the effects of spatial filtering can be significant and this needs to be considered in the choice of prediction model. This paper investigates the errors that can occur with Statistical Energy Analysis (SEA) and the potential of using Advanced SEA (ASEA) to improve predictions. The focus is on the low- and mid-frequency range where plates only support local modes with low mode counts and the in situ modal overlap is relatively high. To increase the computational efficiency when using ASEA on large systems, a beam tracing method is introduced which groups together all rays with the same heading into a single beam. Based on a diffuse field on the source plate, numerical experiments are used to determine the angular distribution of incident power on receiver plate edges on linear and cuboid box-like structures. These show that on receiver plates which do not share a boundary with the source plate, the angular distribution on the receiver plate boundaries differs significantly from a diffuse field. SEA and ASEA predictions are assessed through comparison with finite element models. With rain-on-the-roof excitation on the source plate, the results show that compared to SEA, ASEA provides significantly better estimates of the receiver plate energy, but only where there are at least one or two bending modes in each one-third octave band. Whilst ASEA provides better accuracy than SEA, discrepancies still exist which become more apparent when the direct propagation path crosses more than three nominally identical structural junctions.

Global Dynamic Numerical Simulations of Plate Tectonic Reorganizations

NASA Astrophysics Data System (ADS)

Morra, G.; Quevedo, L.; Butterworth, N.; Matthews, K. J.; Müller, D.

2010-12-01

We use a new numerical approach for global geodynamics to investigate the origin of present global plate motion and to identify the causes of the last two global tectonic reorganizations occurred about 50 and 100 million years ago (Ma) [1]. While the 50 Ma event is the most well-known global plate-mantle event, expressed by the bend in the Hawaiian-Emperor volcanic chain, a prominent plate reorganization at about 100 Ma, although presently little studied, is clearly indicated by a major bend in the fracture zones in the Indian Ocean and by a change in Pacific plate motion [2]. Our workflow involves turning plate reconstructions into surface meshes that are subsequently employed as initial conditions for global Boundary Element numerical models. The tectonic setting that anticipates the reorganizations is processed with the software GPlates, combining the 3D mesh of the paleo-plate morphology and the reconstruction of paleo-subducted slabs, elaborated from tectonic history [3]. All our models involve the entire planetary system, are fully dynamic, have free surface, are characterized by a spectacular computational speed due to the simultaneous use of the multi-pole algorithm and the Boundary Element formulation and are limited only by the use of sharp material property variations [4]. We employ this new tool to unravel the causes of plate tectonic reorganizations, producing and comparing global plate motion with the reconstructed ones. References: [1] Torsvik, T., Müller, R.D., Van der Voo, R., Steinberger, B., and Gaina, C., 2008, Global Plate Motion Frames: Toward a unified model: Reviews in Geophysics, VOL. 46, RG3004, 44 PP., 2008 [2] Wessel, P. and Kroenke, L.W. Pacific absolute plate motion since 145 Ma: An assessment of the fixed hot spot hypothesis. Journal of Geophysical Research, Vol 113, B06101, 2008 [3] L. Quevedo, G. Morra, R. D. Mueller. Parallel Fast Multipole Boundary Element Method for Crustal Dynamics, Proceeding 9th World Congress and 4th Asian Pacific Congress on Computational Mechanics, July 2010, iopscience.iop.org/1757-899X/10/1/012012. [4] G. Morra, P. Chatelain, P. Tackley and P. Koumoutzakos, 2007, Large scale three-dimensional boundary element simulation of subduction, in Proceeding International Conference on Computational Science - Part III, LNCS 4489, pp. 1122-1129. Interaction between two subducting slabs.

BUCKY instruction manual, version 3.3

NASA Technical Reports Server (NTRS)

Smith, James P.

1994-01-01

The computer program BUCKY is a p-version finite element package for the solution of structural problems. The current version of BUCKY solves the 2-D plane stress, 3-D plane stress plasticity, 3-D axisymmetric, Mindlin and Kirchoff plate bending, and buckling problems. The p-version of the finite element method is a highly accurate version of the traditional finite element method. Example cases are presented to show the accuracy and application of BUCKY.

On optimization of a composite bone plate using the selective stress shielding approach.

PubMed

Samiezadeh, Saeid; Tavakkoli Avval, Pouria; Fawaz, Zouheir; Bougherara, Habiba

2015-02-01

Bone fracture plates are used to stabilize fractures while allowing for adequate compressive force on the fracture ends. Yet the high stiffness of conventional bone plates significantly reduces compression at the fracture site, and can lead to subsequent bone loss upon healing. Fibre-reinforced composite bone plates have been introduced to address this drawback. However, no studies have optimized their configurations to fulfill the requirements of proper healing. In the present study, classical laminate theory and the finite element method were employed for optimization of a composite bone plate. A hybrid composite made of carbon fibre/epoxy with a flax/epoxy core, which was introduced previously, was optimized by varying the laminate stacking sequence and the contribution of each material, in order to minimize the axial stiffness and maximize the torsional stiffness for a given range of bending stiffness. The initial 14×4(14) possible configurations were reduced to 13 after applying various design criteria. A comprehensive finite element model, validated against a previous experimental study, was used to evaluate the mechanical performance of each composite configuration in terms of its fracture stability, load sharing, and strength in transverse and oblique Vancouver B1 fracture configurations at immediately post-operative, post-operative, and healed bone stages. It was found that a carbon fibre/epoxy plate with an axial stiffness of 4.6 MN, and bending and torsional stiffness of 13 and 14 N·m(2), respectively, showed an overall superiority compared with other laminate configurations. It increased the compressive force at the fracture site up to 14% when compared to a conventional metallic plate, and maintained fracture stability by ensuring the fracture fragments' relative motions were comparable to those found during metallic plate fixation. The healed stage results revealed that implantation of the titanium plate caused a 40.3% reduction in bone stiffness, while the composite plate lowered the stiffness by 32.9% as compared to the intact femur. This study proposed a number of guidelines for the design of composite bone plates. The findings suggest that a composite bone plate could be customized to allow for moderate compressive force on the fracture ends, while remaining relatively rigid in bending and torsion and strong enough to withstand external loads when a fracture gap is present. The results indicate that the proposed composite bone plate could be a potential candidate for bone fracture plate applications. Copyright © 2014 Elsevier Ltd. All rights reserved.

Evaluation on Bending Properties of Biomaterial GUM Metal Meshed Plates for Bone Graft Applications

NASA Astrophysics Data System (ADS)

Suzuki, Hiromichi; He, Jianmei

2017-11-01

There are three bone graft methods for bone defects caused by diseases such as cancer and accident injuries: Autogenous bone grafts, Allografts and Artificial bone grafts. In this study, meshed GUM Metal plates with lower elasticity, high strength and high biocompatibility are introduced to solve the over stiffness & weight problems of ready-used metal implants. Basic mesh shapes are designed and applied to GUM Metal plates using 3D CAD modeling tools. Bending properties of prototype meshed GUM Metal plates are evaluated experimentally and analytically. Meshed plate specimens with 180°, 120° and 60° axis-symmetrical types were fabricated for 3-point bending tests. The pseudo bending elastic moduli of meshed plate specimens obtained from 3-point bending test are ranged from 4.22 GPa to 16.07 GPa, within the elasticity range of natural cortical bones from 2.0 GPa to 30.0 GPa. Analytical approach method is validated by comparison with experimental and analytical results for evaluation on bending property of meshed plates.

Evaluation of Transverse Thermal Stresses in Composite Plates Based on First-Order Shear Deformation Theory

NASA Technical Reports Server (NTRS)

Rolfes, R.; Noor, A. K.; Sparr, H.

1998-01-01

A postprocessing procedure is presented for the evaluation of the transverse thermal stresses in laminated plates. The analytical formulation is based on the first-order shear deformation theory and the plate is discretized by using a single-field displacement finite element model. The procedure is based on neglecting the derivatives of the in-plane forces and the twisting moments, as well as the mixed derivatives of the bending moments, with respect to the in-plane coordinates. The calculated transverse shear stiffnesses reflect the actual stacking sequence of the composite plate. The distributions of the transverse stresses through-the-thickness are evaluated by using only the transverse shear forces and the thermal effects resulting from the finite element analysis. The procedure is implemented into a postprocessing routine which can be easily incorporated into existing commercial finite element codes. Numerical results are presented for four- and ten-layer cross-ply laminates subjected to mechanical and thermal loads.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gyrya, Vitaliy; Mourad, Hashem Mohamed

We present a family of C1-continuous high-order Virtual Element Methods for Poisson-Kirchho plate bending problem. The convergence of the methods is tested on a variety of meshes including rectangular, quadrilateral, and meshes obtained by edge removal (i.e. highly irregular meshes). The convergence rates are presented for all of these tests.

Active vibration control of structures undergoing bending vibrations

NASA Technical Reports Server (NTRS)

Pla, Frederic G. (Inventor); Rajiyah, Harindra (Inventor)

1995-01-01

An active vibration control subassembly for a structure (such as a jet engine duct or a washing machine panel) undergoing bending vibrations caused by a source (such as the clothes agitator of the washing machine) independent of the subassembly. A piezoceramic actuator plate is vibratable by an applied electric AC signal. The plate is connected to the structure such that vibrations in the plate induced by the AC signal cause canceling bending vibrations in the structure and such that the plate is compressively pre-stressed along the structure when the structure is free of any bending vibrations. The compressive prestressing increases the amplitude of the canceling bending vibrations before the critical tensile stress level of the plate is reached. Preferably, a positive electric DC bias is also applied to the plate in its poling direction.

Combined tension and bending testing of tapered composite laminates

NASA Astrophysics Data System (ADS)

O'Brien, T. Kevin; Murri, Gretchen B.; Hagemeier, Rick; Rogers, Charles

1994-11-01

A simple beam element used at Bell Helicopter was incorporated in the Computational Mechanics Testbed (COMET) finite element code at the Langley Research Center (LaRC) to analyze the responce of tappered laminates typical of flexbeams in composite rotor hubs. This beam element incorporated the influence of membrane loads on the flexural response of the tapered laminate configurations modeled and tested in a combined axial tension and bending (ATB) hydraulic load frame designed and built at LaRC. The moments generated from the finite element model were used in a tapered laminated plate theory analysis to estimate axial stresses on the surface of the tapered laminates due to combined bending and tension loads. Surfaces strains were calculated and compared to surface strains measured using strain gages mounted along the laminate length. The strain distributions correlated reasonably well with the analysis. The analysis was then used to examine the surface strain distribution in a non-linear tapered laminate where a similarly good correlation was obtained. Results indicate that simple finite element beam models may be used to identify tapered laminate configurations best suited for simulating the response of a composite flexbeam in a full scale rotor hub.

An assumed-stress hybrid 4-node shell element with drilling degrees of freedom

NASA Technical Reports Server (NTRS)

Aminpour, M. A.

1992-01-01

An assumed-stress hybrid/mixed 4-node quadrilateral shell element is introduced that alleviates most of the deficiencies associated with such elements. The formulation of the element is based on the assumed-stress hybrid/mixed method using the Hellinger-Reissner variational principle. The membrane part of the element has 12 degrees of freedom including rotational or 'drilling' degrees of freedom at the nodes. The bending part of the element also has 12 degrees of freedom. The bending part of the element uses the Reissner-Mindlin plate theory which takes into account the transverse shear contributions. The element formulation is derived from an 8-node isoparametric element by expressing the midside displacement degrees of freedom in terms of displacement and rotational degrees of freedom at corner nodes. The element passes the patch test, is nearly insensitive to mesh distortion, does not 'lock', possesses the desirable invariance properties, has no hidden spurious modes, and for the majority of test cases used in this paper produces more accurate results than the other elements employed herein for comparison.

Effects of bending and heat on the ductility and fracture toughness of flange plate.

DOT National Transportation Integrated Search

2012-05-01

Bridge fabricators for the Texas Department of Transportation (TxDOT) have occasionally experienced the : formation of cracks in flange plate during bending operations, particularly when heat is applied. Bending the : flange plate is necessary for ce...

Numerical and experimental study on multi-pass laser bending of AH36 steel strips

NASA Astrophysics Data System (ADS)

Fetene, Besufekad N.; Kumar, Vikash; Dixit, Uday S.; Echempati, Raghu

2018-02-01

Laser bending is a process of bending of plates, small sized sheets, strips and tubes, in which a moving or stationary laser beam heats the workpiece to achieve the desired curvature due to thermal stresses. Researchers studied the effects of different process parameters related to the laser source, material and workpiece geometry on laser bending of metal sheets. The studies are focused on large sized sheets. The workpiece geometry parameters like sheet thickness, length and width also affect the bend angle considerably. In this work, the effects of width and thickness on multi-pass laser bending of AH36 steel strips were studied experimentally and numerically. Finite element model using ABAQUS® was developed to investigate the size effect on the prediction of the bend angle. Microhardness and flexure tests showed an increase in the flexural strength as well as microhardness in the scanned zone. The microstructures of the bent strips also supported the physical observations.

Surface cracks in a plate of finite width under tension or bending

NASA Technical Reports Server (NTRS)

Erdogan, F.; Boduroglu, H.

1984-01-01

The problem of a finite plate containing collinear surface cracks is considered and solved by using the line spring model with plane elasticity and Reissner's plate theory. The main focus is on the effect of interaction between two cracks or between cracks and stress-free plate boundaries on the stress intensity factors in an effort to provide extensive numerical results which may be useful in applications. Some sample results are obtained and are compared with the existing finite element results. Then the problem is solved for a single (internal) crack, two collinear cracks, and two corner cracks for wide range of relative dimensions. Particularly in corner cracks, the agreement with the finite element solution is surprisingly very good. The results are obtained for semi-elliptic and rectangular crack profiles which may, in practice, correspond to two limiting cases of the actual profile of a subcritically growing surface crack.

Surface cracks in a plate of finite width under extension or bending

NASA Technical Reports Server (NTRS)

Erdogan, F.; Boduroglu, H.

1984-01-01

In this paper the problem of a finite plate containing collinear surface cracks is considered. The problem is solved by using the line spring model with plane elasticity and Reissner's plate theory. The main purpose of the study is to investigate the effect of interaction between two cracks or between cracks and stress-free plate boundaries on the stress intensity factors and to provide extensive numerical results which may be useful in applications. First, some sample results are obtained and are compared with the existing finite element results. Then the problem is solved for a single (internal) crack, two collinear cracks and two corner cracks for wide range of relative dimensions. Particularly in corner cracks the agreement with the finite element solution is surprisingly very good. The results are obtained for semielliptic and rectangular crack profiles which may, in practice, correspond to two limiting cases of the actual profile of a subcritically growing surface crack.

Damage tolerance of bonded composite aircraft repairs for metallic structures

NASA Astrophysics Data System (ADS)

Clark, Randal John

This thesis describes the development and validation of methods for damage tolerance substantiation of bonded composite repairs applied to cracked plates. This technology is used to repair metal aircraft structures, offering improvements in fatigue life, cost, manufacturability, and inspectability when compared to riveted repairs. The work focuses on the effects of plate thickness and bending on repair life, and covers fundamental aspects of fracture and fatigue of cracked plates and bonded joints. This project falls under the UBC Bonded Composite Repair Program, which has the goal of certification and widespread use of bonded repairs in civilian air transportation. This thesis analyses the plate thickness and transverse stress effects on fracture of repaired plates and the related problem of induced geometrically nonlinear bending in unbalanced (single-sided) repairs. The author begins by developing a classification scheme for assigning repair damage tolerance substantiation requirements based upon stress-based adhesive fracture/fatigue criteria and the residual strength of the original structure. The governing equations for bending of cracked plates are then reformulated and line-spring models are developed for linear and nonlinear coupled bending and extension of reinforced cracks. The line-spring models were used to correct the Wang and Rose energy method for the determination of the long-crack limit stress intensity, and to develop a new interpolation model for repaired cracks of arbitrary length. The analysis was validated using finite element models and data from mechanical tests performed on hybrid bonded joints and repair specimens that are representative of an in-service repair. This work will allow designers to evaluate the damage tolerance of the repaired plate, the adhesive, and the composite patch, which is an airworthiness requirement under FAR (Federal Aviation Regulations) 25.571. The thesis concludes by assessing the remaining barriers to certification of bonded repairs, discussing the results of the analysis, and making suggestions for future work. The developed techniques should also prove to be useful for the analysis of fibre-reinforced metal laminates and other layered structures. Some concepts are general and should be useful in the analysis of any plate with large in-plane stress gradients that lead to significant transverse stresses.

50-Ma Initiation of Hawaiian-Emperor Bend Records Major Change in Pacific Plate Motion

NASA Astrophysics Data System (ADS)

Sharp, Warren D.; Clague, David A.

2006-09-01

The Hawaiian-Emperor bend has played a prominent yet controversial role in deciphering past Pacific plate motions and the tempo of plate motion change. New ages for volcanoes of the central and southern Emperor chain define large changes in volcanic migration rate with little associated change in the chain's trend, which suggests that the bend did not form by slowing of the Hawaiian hot spot. Initiation of the bend near Kimmei seamount about 50 million years ago (MA) was coincident with realignment of Pacific spreading centers and early magmatism in western Pacific arcs, consistent with formation of the bend by changed Pacific plate motion.

Development and applications of a flat triangular element for thin laminated shells

NASA Astrophysics Data System (ADS)

Mohan, P.

Finite element analysis of thin laminated shells using a three-noded flat triangular shell element is presented. The flat shell element is obtained by combining the Discrete Kirchhoff Theory (DKT) plate bending element and a membrane element similar to the Allman element, but derived from the Linear Strain Triangular (LST) element. The major drawback of the DKT plate bending element is that the transverse displacement is not explicitly defined within the interior of the element. In the present research, free vibration analysis is performed both by using a lumped mass matrix and a so called consistent mass matrix, obtained by borrowing shape functions from an existing element, in order to compare the performance of the two methods. Several numerical examples are solved to demonstrate the accuracy of the formulation for both small and large rotation analysis of laminated plates and shells. The results are compared with those available in the existing literature and those obtained using the commercial finite element package ABAQUS and are found to be in good agreement. The element is employed for two main applications involving large flexible structures. The first application is the control of thermal deformations of a spherical mirror segment, which is a segment of a multi-segmented primary mirror used in a space telescope. The feasibility of controlling the surface distortions of the mirror segment due to arbitrary thermal fields, using discrete and distributed actuators, is studied. The second application is the analysis of an inflatable structure, being considered by the US Army for housing vehicles and personnel. The updated Lagrangian formulation of the flat shell element has been developed primarily for the nonlinear analysis of the tent structure, since such a structure is expected to undergo large deformations and rotations under the action of environmental loads like the wind and snow loads. The follower effects of the pressure load have been included in the updated Lagrangian formulation of the flat shell element and have been validated using standard examples in the literature involving deformation-dependent pressure loads. The element can be used to obtain the nonlinear response of the tent structure under wind and snow loads. (Abstract shortened by UMI.)

Aeroservoelastic Tailoring with Piezoelectric Materials: Actuator Optimization Studies

DTIC Science & Technology

1994-02-09

publcreease AirFre usfied tof Scentrolstrctua defleactio ofarstcsstm.h robe iSP tofrish geometrica Arrangemien fo8c1ecnro;adotmm1oeaeo5uraepnl o control...of the plate. The differential bending induces warping in the - correct " direction of twisL 2.3 The elemental model The basic building block finite

Benchmarking the QUAD4/TRIA3 element

NASA Technical Reports Server (NTRS)

Pitrof, Stephen M.; Venkayya, Vipperla B.

1993-01-01

The QUAD4 and TRIA3 elements are the primary plate/shell elements in NASTRAN. These elements enable the user to analyze thin plate/shell structures for membrane, bending and shear phenomena. They are also very new elements in the NASTRAN library. These elements are extremely versatile and constitute a substantially enhanced analysis capability in NASTRAN. However, with the versatility comes the burden of understanding a myriad of modeling implications and their effect on accuracy and analysis quality. The validity of many aspects of these elements were established through a series of benchmark problem results and comparison with those available in the literature and obtained from other programs like MSC/NASTRAN and CSAR/NASTRAN. Never-the-less such a comparison is never complete because of the new and creative use of these elements in complex modeling situations. One of the important features of QUAD4 and TRIA3 elements is the offset capability which allows the midsurface of the plate to be noncoincident with the surface of the grid points. None of the previous elements, with the exception of bar (beam), has this capability. The offset capability played a crucial role in the design of QUAD4 and TRIA3 elements. It allowed modeling layered composites, laminated plates and sandwich plates with the metal and composite face sheets. Even though the basic implementation of the offset capability is found to be sound in the previous applications, there is some uncertainty in relatively simple applications. The main purpose of this paper is to test the integrity of the offset capability and provide guidelines for its effective use. For the purpose of simplicity, references in this paper to the QUAD4 element will also include the TRIA3 element.

Buckling behavior of compression-loaded symmetrically-laminated angle-ply plates with holes

NASA Technical Reports Server (NTRS)

Nemeth, M. P.

1986-01-01

An approximate analysis for buckling of a rectangular specially-orthotropic plate with a central circular hole is applied to symmetrically-laminated angle-ply plates. Results obtained from finite element analyses and experiments indicate that the approximate analysis predicts accurately the buckling loads of (+/-theta sub m)s plates with integer values of m not below 6 and with hole diameters up to 50 percent of the plate width. Moreover, the results indicate that the approximate analysis can be used to predict the buckling trends of plates with hole diameters up to 70 percent of the plate width. Results of a parametric study indicate the influence of hole size, plate aspect ratio, loading conditions, boundary conditions, and orthotropy on the buckling load. Results are also presented that indicate the relationship of the bending stiffness and the prebuckling load distribution to the buckling load of a plate with a hole.

Biomechanical assessment and 3D finite element analysis of the treatment of tibial fractures using minimally invasive percutaneous plates

PubMed Central

Hu, Xin-Jia; Wang, Hua

2017-01-01

The aim of the present study was to investigate the biomechanical effects of varying the length of a limited contact-dynamic compression plate (LC-DCP) and the number and position of screws on middle tibial fractures, and to provide biomechanical evidence regarding minimally invasive plate osteosynthesis (MIPO). For biomechanical testing, 60 tibias from cadavers (age at mortality, 20–40 years) were used to create middle and diagonal fracture models without defects. Tibias were randomly grouped and analyzed by biomechanic and three-dimensional (3D) finite element analysis. The differences among LC-DCPs of different lengths (6-, 10- and 14-hole) with 6 screws, 14-hole LC-DCPs with different numbers of screws (6, 10 and 14), and 14-hole LC-DCPs with 6 screws at different positions with regard to mechanical characteristics, including compressing, torsion and bending, were examined. The 6-hole LC-DCP had greater vertical compression strain compared with the 10- and 14-hole LC-DCPs (P<0.01), and the 14-hole LC-DCP had greater lateral strain than the 6- and 10-hole LC-DCPs (P<0.01). Furthermore, significant differences in torque were observed among the LC-DPs of different lengths (P<0.01). For 14-hole LC-DCPs with different numbers of screws, no significant differences in vertical strain, lateral strain or torque were detected (P>0.05). However, plates with 14 screws had greater vertical strain compared with those fixed with 6 or 10 screws (P<0.01). For 4-hole LC-DCPs with screws at different positions, vertical compression strain values were lowest for plates with screws at positions 1, 4, 7, 8, 11 and 14 (P<0.01). The lateral strain values and vertical strain values for plates with screws at positions 1, 3, 6, 9, 12 and 14 were significantly lower compared with those at the other positions (P<0.01), and torque values were also low. Thus, the 14-hole LC-DCP was the most stable against vertical compression, torsion and bending, and the 6-hole LC-DCP was the least stable. However, the use of 14 screws with a 14-hole LC-DCP provided less stability against bending than did 6 or 10 screws. Furthermore, fixation with distributed screws, in which some screws were close to the fracture line, provided good stability against compression and torsion, while fixation with screws at the ends of the LC-DCP provided poor stability against bending, compressing and torsion. PMID:28781632

Buckling Analysis of Angle-ply Composite and Sandwich Plates by Combination of Geometric Stiffness Matrix

NASA Astrophysics Data System (ADS)

Zhen, Wu; Wanji, Chen

2007-05-01

Buckling response of angle-ply laminated composite and sandwich plates are analyzed using the global-local higher order theory with combination of geometric stiffness matrix in this paper. This global-local theory completely fulfills the free surface conditions and the displacement and stress continuity conditions at interfaces. Moreover, the number of unknowns in this theory is independent of the number of layers in the laminate. Based on this global-local theory, a three-noded triangular element satisfying C1 continuity conditions has also been proposed. The bending part of this element is constructed from the concept of DKT element. In order to improve the accuracy of the analysis, a method of modified geometric stiffness matrix has been introduced. Numerical results show that the present theory not only computes accurately the buckling response of general laminated composite plates but also predicts the critical buckling loads of soft-core sandwiches. However, the global higher-order theories as well as first order theories might encounter some difficulties and overestimate the critical buckling loads for soft-core sandwich plates.

Finite element analysis of locking plate and two types of intramedullary nails for treating mid-shaft clavicle fractures.

PubMed

Ni, Ming; Niu, Wenxin; Wong, Duo Wai-Chi; Zeng, Wei; Mei, Jiong; Zhang, Ming

2016-08-01

Both plate and intramedullary nail fixations, including straight and anatomic nails, have been clinically adopted for the treatment of displaced mid-shaft clavicle fractures. However, the biomechanical performances of these fixations and implants have not been well evaluated. This study aims to compare the construct stability, stress distribution and fracture micro-motion of three fixations based on finite element (FE) method. The FE model of clavicle was reconstructed from CT images of a male volunteer. A mid-shaft fracture gap was created in the intact clavicle. Three fixation styles were simulated including locking plate (LP), anatomic intramedullary nail (CRx), and straight intramedullary nail (RCP). Two loading scenarios (axial compression and inferior bending) were applied at the distal end of the clavicle to simulate arm abduction, while the sternal end was fixed. Under both conditions, the LP was the stiffest, followed by the CRx, and the RCP was the weakest. LP also displayed a more evenly stress distribution for both implant and bone. RCP had a higher stress compared with CRx in both conditions. Moreover, all implants sustained higher stress level under the loading condition of bending than compression. The plate fixation significantly stabilizes the fracture gap, reduces the implant stress, and serves as the recommended fixation for the mid-shaft clavicle fracture. The CRx is an alternative device to treat clavicle shaft fracture, but the shoulder excessive activities should be avoided after operation. Copyright © 2016 Elsevier Ltd. All rights reserved.

Analytic and Computational Perspectives of Multi-Scale Theory for Homogeneous, Laminated Composite, and Sandwich Beams and Plates

NASA Technical Reports Server (NTRS)

Tessler, Alexander; Gherlone, Marco; Versino, Daniele; DiSciuva, Marco

2012-01-01

This paper reviews the theoretical foundation and computational mechanics aspects of the recently developed shear-deformation theory, called the Refined Zigzag Theory (RZT). The theory is based on a multi-scale formalism in which an equivalent single-layer plate theory is refined with a robust set of zigzag local layer displacements that are free of the usual deficiencies found in common plate theories with zigzag kinematics. In the RZT, first-order shear-deformation plate theory is used as the equivalent single-layer plate theory, which represents the overall response characteristics. Local piecewise-linear zigzag displacements are used to provide corrections to these overall response characteristics that are associated with the plate heterogeneity and the relative stiffnesses of the layers. The theory does not rely on shear correction factors and is equally accurate for homogeneous, laminated composite, and sandwich beams and plates. Regardless of the number of material layers, the theory maintains only seven kinematic unknowns that describe the membrane, bending, and transverse shear plate-deformation modes. Derived from the virtual work principle, RZT is well-suited for developing computationally efficient, C(sup 0)-continuous finite elements; formulations of several RZT-based elements are highlighted. The theory and its finite element approximations thus provide a unified and reliable computational platform for the analysis and design of high-performance load-bearing aerospace structures.

Analytic and Computational Perspectives of Multi-Scale Theory for Homogeneous, Laminated Composite, and Sandwich Beams and Plates

NASA Technical Reports Server (NTRS)

Tessler, Alexander; Gherlone, Marco; Versino, Daniele; Di Sciuva, Marco

2012-01-01

This paper reviews the theoretical foundation and computational mechanics aspects of the recently developed shear-deformation theory, called the Refined Zigzag Theory (RZT). The theory is based on a multi-scale formalism in which an equivalent single-layer plate theory is refined with a robust set of zigzag local layer displacements that are free of the usual deficiencies found in common plate theories with zigzag kinematics. In the RZT, first-order shear-deformation plate theory is used as the equivalent single-layer plate theory, which represents the overall response characteristics. Local piecewise-linear zigzag displacements are used to provide corrections to these overall response characteristics that are associated with the plate heterogeneity and the relative stiffnesses of the layers. The theory does not rely on shear correction factors and is equally accurate for homogeneous, laminated composite, and sandwich beams and plates. Regardless of the number of material layers, the theory maintains only seven kinematic unknowns that describe the membrane, bending, and transverse shear plate-deformation modes. Derived from the virtual work principle, RZT is well-suited for developing computationally efficient, C0-continuous finite elements; formulations of several RZT-based elements are highlighted. The theory and its finite elements provide a unified and reliable computational platform for the analysis and design of high-performance load-bearing aerospace structures.

Biomechanical analysis of fixation of middle third fractures of the clavicle.

PubMed

Drosdowech, Darren S; Manwell, Stuart E E; Ferreira, Louis M; Goel, Danny P; Faber, Kenneth J; Johnson, James A

2011-01-01

This biomechanical study compares four different techniques of fixation of middle third clavicular fractures. Twenty fresh-frozen clavicles were randomized into four groups. Each group used a different fixation device (3.5 Synthes reconstruction plate, 3.5 Synthes limited contact dynamic compression plate, 3.5 Synthes locking compression plate, and 4.5 DePuy Rockwood clavicular pin). All constructs were mechanically tested in bending and torque modes both with and without a simulated inferior cortical defect. Bending load to failure was also conducted. The four groups were compared using an analysis of variance test. The plate constructs were stiffer than the pin during both pure bending and torque loads with or without an inferior cortical defect. Bending load to failure with an inferior cortical defect revealed that the reconstruction plate was weaker compared with the other three groups. The limited contact and locking plates were stiffer than the reconstruction plate but demonstrated statistical significance only with the cortical defect. As hypothesized, the 3.5 limited contact dynamic compression plate and 3.5 locking compression plate demonstrated the greatest resistance to bending and torque loads, especially in the presence of simulated comminution of a middle third clavicular fracture. The reconstruction plate demonstrated lower stiffness and strength values compared with the other plates, especially with a cortical defect, whereas the pin showed poor resistance to bending and torque loads in all modes of testing. This information may help surgeons to choose the most appropriate method of fixation when treating fractures of the middle third of the clavicle.

Elastic/viscoplastic behavior of fiber-reinforced thermoplastic composites

NASA Technical Reports Server (NTRS)

Wang, C.; Sun, C. T.; Gates, T. S.

1990-01-01

An elastic/viscoplastic constitutive model was used to characterize the nonlinear and rate dependent behavior of a continuous fiber-reinforced thermoplastic composite. This model was incorporated into a finite element program for the analysis of laminated plates and shells. Details on the finite element formulation with the proposed constitutive model were presented. The numerical results were compared with experimental data for uniaxial tension and three-point bending tests of (+ or - 45 deg)3s APC-2 laminates.

Finite element based N-Port model for preliminary design of multibody systems

NASA Astrophysics Data System (ADS)

Sanfedino, Francesco; Alazard, Daniel; Pommier-Budinger, Valérie; Falcoz, Alexandre; Boquet, Fabrice

2018-02-01

This article presents and validates a general framework to build a linear dynamic Finite Element-based model of large flexible structures for integrated Control/Structure design. An extension of the Two-Input Two-Output Port (TITOP) approach is here developed. The authors had already proposed such framework for simple beam-like structures: each beam was considered as a TITOP sub-system that could be interconnected to another beam thanks to the ports. The present work studies bodies with multiple attaching points by allowing complex interconnections among several sub-structures in tree-like assembly. The TITOP approach is extended to generate NINOP (N-Input N-Output Port) models. A Matlab toolbox is developed integrating beam and bending plate elements. In particular a NINOP formulation of bending plates is proposed to solve analytic two-dimensional problems. The computation of NINOP models using the outputs of a MSC/Nastran modal analysis is also investigated in order to directly use the results provided by a commercial finite element software. The main advantage of this tool is to provide a model of a multibody system under the form of a block diagram with a minimal number of states. This model is easy to operate for preliminary design and control. An illustrative example highlights the potential of the proposed approach: the synthesis of the dynamical model of a spacecraft with two deployable and flexible solar arrays.

Boundary element analysis of post-tensioned slabs

NASA Astrophysics Data System (ADS)

Rashed, Youssef F.

2015-06-01

In this paper, the boundary element method is applied to carry out the structural analysis of post-tensioned flat slabs. The shear-deformable plate-bending model is employed. The effect of the pre-stressing cables is taken into account via the equivalent load method. The formulation is automated using a computer program, which uses quadratic boundary elements. Verification samples are presented, and finally a practical application is analyzed where results are compared against those obtained from the finite element method. The proposed method is efficient in terms of computer storage and processing time as well as the ease in data input and modifications.

Elasto-plastic bending of cracked plates, including the effects of crack closure. Ph.D. Thesis

NASA Technical Reports Server (NTRS)

Jones, D. P.

1972-01-01

A capability for solving elasto-plastic plate bending problems is developed using assumptions consistent with Kirchhoff plate theory. Both bending and extensional modes of deformation are admitted with the two modes becoming coupled as yielding proceeds. Equilibrium solutions are obtained numerically by determination of the stationary point of a functional which is analogous to the potential strain energy. The stationary value of the functional for each load increment is efficiently obtained through use of the conjugate gradient. This technique is applied to the problem of a large centrally through cracked plate subject to remote circular bending. Comparison is drawn between two cases of the bending problem. The first neglects the possibility of crack face interference with bending, and the second includes a kinematic prohibition against the crack face from passing through the symmetry plane. Results are reported which isolate the effects of elastoplastic flow and crack closure.

On mixed and displacement finite element models of a refined shear deformation theory for laminated anisotropic plates

NASA Technical Reports Server (NTRS)

Reddy, J. N.

1986-01-01

An improved plate theory that accounts for the transverse shear deformation is presented, and mixed and displacement finite element models of the theory are developed. The theory is based on an assumed displacement field in which the inplane displacements are expanded in terms of the thickness coordinate up to the cubic term and the transverse deflection is assumed to be independent of the thickness coordinate. The governing equations of motion for the theory are derived from the Hamilton's principle. The theory eliminates the need for shear correction factors because the transverse shear stresses are represented parabolically. A mixed finite element model that uses independent approximations of the displacements and moments, and a displacement model that uses only displacements as degrees of freedom are developed. A comparison of the numerical results for bending with the exact solutions of the new theory and the three-dimensional elasticity theory shows that the present theory (and hence the finite element models) is more accurate than other plate-theories of the same order.

Thermoelastic Formulation of Stiffened, Unsymmetric Composite Panels for Finite Element Analysis of High Speed Aircraft

NASA Technical Reports Server (NTRS)

Collier, Craig S.

2004-01-01

An emerging technology need for capturing 3-D panel thermoelastic response with 2-D planar finite element models (FEMs) is aided with an equivalent plate stiffness and thermal coefficient formulation. The formulation is general and applies to all panel concepts. Included with the formulation is the ability to provide membrane-bending coupling of unsymmetric sections and calculation of all thermal expansion and bending responses from in-plane and through-the-thickness temperature gradients. Thermal residual strains for both the laminates and plies are included. The general formulation is defined and then applied to a hat-shaped, corrugated stiffened panel. Additional formulations are presented where required to include all of the hat's unique characteristics. Each formulation is validated independently with 3-D FEA.

Ex vivo biomechanical evaluation of pigeon (Columba livia) cadaver intact humeri and ostectomized humeri stabilized with caudally applied titanium locking plate or stainless steel nonlocking plate constructs.

PubMed

Darrow, Brett G; Biskup, Jeffrey J; Weigel, Joseph P; Jones, Michael P; Xie, Xie; Liaw, Peter K; Tharpe, Josh L; Sharma, Aashish; Penumadu, Dayakar

2017-05-01

OBJECTIVE To evaluate mechanical properties of pigeon (Columba livia) cadaver intact humeri versus ostectomized humeri stabilized with a locking or nonlocking plate. SAMPLE 30 humeri from pigeon cadavers. PROCEDURES Specimens were allocated into 3 groups and tested in bending and torsion. Results for intact pigeon humeri were compared with results for ostectomized humeri repaired with a titanium 1.6-mm screw locking plate or a stainless steel 1.5-mm dynamic compression plate; the ostectomized humeri mimicked a fracture in a thin cortical bone. Locking plates were secured with locking screws (2 bicortical and 4 monocortical), and nonlocking plates were secured with bicortical nonlocking screws. Constructs were cyclically tested nondestructively in 4-point bending and then tested to failure in bending. A second set of constructs were cyclically tested non-destructively and then to failure in torsion. Stiffness, strength, and strain energy of each construct were compared. RESULTS Intact specimens were stiffer and stronger than the repair groups for all testing methods, except for nonlocking constructs, which were significantly stiffer than intact specimens under cyclic bending. Intact bones had significantly higher strain energies than locking plates in both bending and torsion. Locking and nonlocking plates were of equal strength and strain energy, but not stiffness, in bending and were of equal strength, stiffness, and strain energy in torsion. CONCLUSIONS AND CLINICAL RELEVANCE Results for this study suggested that increased torsional strength may be needed before bone plate repair can be considered as the sole fixation method for avian species.

On a generalized laminate theory with application to bending, vibration, and delamination buckling in composite laminates

DOE Office of Scientific and Technical Information (OSTI.GOV)

Barbero, E.J.

1989-01-01

In this study, a computational model for accurate analysis of composite laminates and laminates with including delaminated interfaces is developed. An accurate prediction of stress distributions, including interlaminar stresses, is obtained by using the Generalized Laminate Plate Theory of Reddy in which layer-wise linear approximation of the displacements through the thickness is used. Analytical as well as finite-element solutions of the theory are developed for bending and vibrations of laminated composite plates for the linear theory. Geometrical nonlinearity, including buckling and postbuckling are included and used to perform stress analysis of laminated plates. A general two dimensional theory of laminatedmore » cylindrical shells is also developed in this study. Geometrical nonlinearity and transverse compressibility are included. Delaminations between layers of composite plates are modelled by jump discontinuity conditions at the interfaces. The theory includes multiple delaminations through the thickness. Geometric nonlinearity is included to capture layer buckling. The strain energy release rate distribution along the boundary of delaminations is computed by a novel algorithm. The computational models presented herein are accurate for global behavior and particularly appropriate for the study of local effects.« less

Investigation of stress concentration at corner points for orthotropic plate bending problem

NASA Astrophysics Data System (ADS)

Vasilyan, N. G.

2018-04-01

This article deals with the bending problem for an orthotropic semi-infinite plate strip when three edges of the plate are hinged and the fourth edge goes to infinity. The plate is loaded with distributed load of intensity q(y). A. Nadai’s approach is applied, which says that to obtain the solution at a far distance from the edge, it is necessary to solve the problem of cylindrical bending. The generalized shearing forces on the fixed edge are investigated.

Finite elements based on consistently assumed stresses and displacements

NASA Technical Reports Server (NTRS)

Pian, T. H. H.

1985-01-01

Finite element stiffness matrices are derived using an extended Hellinger-Reissner principle in which internal displacements are added to serve as Lagrange multipliers to introduce the equilibrium constraint in each element. In a consistent formulation the assumed stresses are initially unconstrained and complete polynomials and the total displacements are also complete such that the corresponding strains are complete in the same order as the stresses. Several examples indicate that resulting properties for elements constructed by this consistent formulation are ideal and are less sensitive to distortions of element geometries. The method has been used to find the optimal stress terms for plane elements, 3-D solids, axisymmetric solids, and plate bending elements.

A standing wave linear ultrasonic motor operating in in-plane expanding and bending modes.

PubMed

Chen, Zhijiang; Li, Xiaotian; Ci, Penghong; Liu, Guoxi; Dong, Shuxiang

2015-03-01

A novel standing wave linear ultrasonic motor operating in in-plane expanding and bending modes was proposed in this study. The stator (or actuator) of the linear motor was made of a simple single Lead Zirconate Titanate (PZT) ceramic square plate (15 × 15 × 2 mm(3)) with a circular hole (D = 6.7 mm) in the center. The geometric parameters of the stator were computed with the finite element analysis to produce in-plane bi-mode standing wave vibration. The calculated results predicted that a driving tip attached at midpoint of one edge of the stator can produce two orthogonal, approximate straight-line trajectories, which can be used to move a slider in linear motion via frictional forces in forward or reverse direction. The investigations showed that the proposed linear motor can produce a six times higher power density than that of a previously reported square plate motor.

Non-linear analysis of wave progagation using transform methods and plates and shells using integral equations

NASA Astrophysics Data System (ADS)

Pipkins, Daniel Scott

Two diverse topics of relevance in modern computational mechanics are treated. The first involves the modeling of linear and non-linear wave propagation in flexible, lattice structures. The technique used combines the Laplace Transform with the Finite Element Method (FEM). The procedure is to transform the governing differential equations and boundary conditions into the transform domain where the FEM formulation is carried out. For linear problems, the transformed differential equations can be solved exactly, hence the method is exact. As a result, each member of the lattice structure is modeled using only one element. In the non-linear problem, the method is no longer exact. The approximation introduced is a spatial discretization of the transformed non-linear terms. The non-linear terms are represented in the transform domain by making use of the complex convolution theorem. A weak formulation of the resulting transformed non-linear equations yields a set of element level matrix equations. The trial and test functions used in the weak formulation correspond to the exact solution of the linear part of the transformed governing differential equation. Numerical results are presented for both linear and non-linear systems. The linear systems modeled are longitudinal and torsional rods and Bernoulli-Euler and Timoshenko beams. For non-linear systems, a viscoelastic rod and Von Karman type beam are modeled. The second topic is the analysis of plates and shallow shells under-going finite deflections by the Field/Boundary Element Method. Numerical results are presented for two plate problems. The first is the bifurcation problem associated with a square plate having free boundaries which is loaded by four, self equilibrating corner forces. The results are compared to two existing numerical solutions of the problem which differ substantially.

A 4-node assumed-stress hybrid shell element with rotational degrees of freedom

NASA Technical Reports Server (NTRS)

Aminpour, Mohammad A.

1990-01-01

An assumed-stress hybrid/mixed 4-node quadrilateral shell element is introduced that alleviates most of the deficiencies associated with such elements. The formulation of the element is based on the assumed-stress hybrid/mixed method using the Hellinger-Reissner variational principle. The membrane part of the element has 12 degrees of freedom including rotational or drilling degrees of freedom at the nodes. The bending part of the element also has 12 degrees of freedom. The bending part of the element uses the Reissner-Mindlin plate theory which takes into account the transverse shear contributions. The element formulation is derived from an 8-node isoparametric element. This process is accomplished by assuming quadratic variations for both in-plane and out-of-plane displacement fields and linear variations for both in-plane and out-of-plane rotation fields along the edges of the element. In addition, the degrees of freedom at midside nodes are approximated in terms of the degrees of freedom at corner nodes. During this process the rotational degrees of freedom at the corner nodes enter into the formulation of the element. The stress field are expressed in the element natural-coordinate system such that the element remains invariant with respect to node numbering.

Effects of cutouts on the behavior of symmetric composite laminates subjected to bending and twisting loads

NASA Technical Reports Server (NTRS)

Prasad, C. B.; Shuart, M. J.; Bains, N. J.; Rouse, M.

1993-01-01

Composite structures are used for a wide variety of aerospace applications. Practical structures contain cutouts and these structures are subjected to in-plane and out-of-plane loading conditions. Structurally efficient designs for composite structures require a thorough understanding of the effects of cutouts on the response of composite plates subjected to inplane or out-of-plane loadings. Most investigations of the behavior of composite plates with cutouts have considered in-plane loadings only. Out-of-plane loadings suchas bending or twisting have received very limited attention. The response of homogeneous plates (e.g., isotropic or orthotropic plates) subjected to bending or twisting moments has been studied analytically. These analyses are for infinite plates and neglect finite-plate effects. Recently, analytical and experimental studies were conducted to determine the effects of cutouts on the response of laminated composite plates subjected to bending moments. No analytical or experimental results are currently available for the effects of cutouts on the response of composite laminates subjected to twisting moments.

Three-Dimensional Effects of Crack Closure in Laminated Composite Plates Subjected to Bending Loads

DTIC Science & Technology

1994-06-01

Approved by: •UW. Kwon, Thesis Advisor wathe D.K~elleher, Chairman Department of Mechanical Engineering ii ABSTRACT Fracture is one of the dominant...5 A. OVERVIEW .......................................... 5 B. CONSTITUTIVE EQUATION .............................. 9 1. Isotropic...the elemental nodes. B. CONSTITUTIVE EQUATION The material property matrix [D] is a symmetric matrix which includes elasticity moduli and Poisson’s

Numerical analysis of the vibroacoustic properties of plates with embedded grids of acoustic black holes.

PubMed

Conlon, Stephen C; Fahnline, John B; Semperlotti, Fabio

2015-01-01

The concept of an Acoustic Black Hole (ABH) has been developed and exploited as an approach for passively attenuating structural vibration. The basic principle of the ABH relies on proper tailoring of the structure geometrical properties in order to produce a gradual reduction of the flexural wave speed, theoretically approaching zero. For practical systems the idealized "zero" wave speed condition cannot be achieved so the structural areas of low wave speed are treated with surface damping layers to allow the ABH to approach the idealized dissipation level. In this work, an investigation was conducted to assess the effects that distributions of ABHs embedded in plate-like structures have on both vibration and structure radiated sound, focusing on characterizing and improving low frequency performance. Finite Element and Boundary Element models were used to assess the vibration response and radiated sound power performance of several plate configurations, comparing baseline uniform plates with embedded periodic ABH designs. The computed modal loss factors showed the importance of the ABH unit cell low order modes in the overall vibration reduction effectiveness of the embedded ABH plates at low frequencies where the free plate bending wavelengths are longer than the scale of the ABH.

Pressures in Tumuli: A Study of Tumuli Formation

NASA Technical Reports Server (NTRS)

Hansen, James E.

2005-01-01

Tumuli form via localized inflation in surface lava flows. These domed features have widths of 10-20 m, lengths of 10-150 m, and heights of 1-9 m. The axial fracture exposes a brittle crust overlying a ductilely deformed layer. The total crustal thickness is typically less than lm. Tumuli are observed on both terrestrial and martian lava flow surfaces, and provide insight on the flow formation processes and rates. Past studies have estimated the inflation pressure using a bending model for a circular, thin elastic plate, assuming small deflection (Rossi and Gudmundson, 1996). This formulation results in unrealistic pressures for some tumuli. We thus examine alternative models, including those with different shapes, bending of the ductile crust, large deflection, plastic deformation, and thick plate bending. Using the thickness of the ductile crust in the equations for thin, circular plates reduces most pressures to reasonable values. Alternative plate shapes do not cause a significant reduction in inflation pressure. Although the large deflection equations should be applicable based on the plate thickness to tumuli height ratios, they give even less realistic pressures. Tumuli with unrealistic pressures appear to have exceeded the critical bending moment, and have relatively thick crusts, requiring thick plate bending models.

Analysis of residual stress and hardness in regions of pre-manufactured and manual bends in fixation plates for maxillary advancement.

PubMed

Araújo, Marcelo Marotta; Lauria, Andrezza; Mendes, Marcelo Breno Meneses; Claro, Ana Paula Rosifini Alves; Claro, Cristiane Aparecida de Assis; Moreira, Roger William Fernandes

2015-12-01

The aim of this study was to analyze, through Vickers hardness test and photoelasticity analysis, pre-bent areas, manually bent areas, and areas without bends of 10-mm advancement pre-bent titanium plates (Leibinger system). The work was divided into three groups: group I-region without bend, group II-region of 90° manual bend, and group III-region of 90° pre-fabricated bends. All the materials were evaluated through hardness analysis by the Vickers hardness test, stress analysis by residual images obtained in a polariscope, and photoelastic analysis by reflection during the manual bending. The data obtained from the hardness tests were statistically analyzed using ANOVA and Tukey's tests at a significance level of 5 %. The pre-bent plate (group III) showed hardness means statistically significantly higher (P < 0.05) than those of the other groups (I-region without bends, II-90° manually bent region). Through the study of photoelastic reflection, it was possible to identify that the stress gradually increased, reaching a pink color (1.81 δ / λ), as the bending was performed. A general analysis of the results showed that the bent plate region of pre-bent titanium presented the best results.

Comparison of theoretical and experimental determination of the flexing of scratch drive actuator plates

NASA Astrophysics Data System (ADS)

Li, Lijie; Brown, James G.; Uttamchandani, Deepak G.

2002-09-01

The scratch drive actuator (SDA) is a key element in microelectromechanical System (MEMS) technology. The actuator can be designed to travel very long distance with precise step size. Various articles describe the characteristics of scratch drive actuators.3, 6, 8 The MEMS designer needs models of SDA in order to incorporate them into their Microsystems applications. The objective of our effort is to develop models for SDA when it is in the working state. In this paper, a suspended SDA plate actuated by electrostatic force is analyzed. A mathematical model is established based on electrostatic coupled mechanical theory. Two phases have been calculated because the plate will contact the bottom surface due to the electrostatic force. One phase is named non-contact mode, and another is named contact mode. From these two models, the relationship between applied voltage and contact distance has been obtained. The geometrical model of bending plate is established to determine the relationship between contact distance and step size. Therefore we can use those two results to obtain the result of step size versus applied voltage that we expect. Finally, couple-field electro-mechanical simulation has been done by commercial software IntelliSuite. We assume that the dimension of SDA plate and bushing are fixed. All the material properties are from JDSU Cronos MUMPs. A Veeco NT1000 surface profiling tool has been used to investigate the bending of SDA plate. The results of experimental and theoretical are compared.

How fault evolution changes strain partitioning and fault slip rates in Southern California: Results from geodynamic modeling

NASA Astrophysics Data System (ADS)

Ye, Jiyang; Liu, Mian

2017-08-01

In Southern California, the Pacific-North America relative plate motion is accommodated by the complex southern San Andreas Fault system that includes many young faults (<2 Ma). The initiation of these young faults and their impact on strain partitioning and fault slip rates are important for understanding the evolution of this plate boundary zone and assessing earthquake hazard in Southern California. Using a three-dimensional viscoelastoplastic finite element model, we have investigated how this plate boundary fault system has evolved to accommodate the relative plate motion in Southern California. Our results show that when the plate boundary faults are not optimally configured to accommodate the relative plate motion, strain is localized in places where new faults would initiate to improve the mechanical efficiency of the fault system. In particular, the Eastern California Shear Zone, the San Jacinto Fault, the Elsinore Fault, and the offshore dextral faults all developed in places of highly localized strain. These younger faults compensate for the reduced fault slip on the San Andreas Fault proper because of the Big Bend, a major restraining bend. The evolution of the fault system changes the apportionment of fault slip rates over time, which may explain some of the slip rate discrepancy between geological and geodetic measurements in Southern California. For the present fault configuration, our model predicts localized strain in western Transverse Ranges and along the dextral faults across the Mojave Desert, where numerous damaging earthquakes occurred in recent years.

Biomechanical comparison of a novel transoral atlantoaxial anchored cage with established fixation technique - a finite element analysis.

PubMed

Zhang, Bao-cheng; Liu, Hai-bo; Cai, Xian-hua; Wang, Zhi-hua; Xu, Feng; Kang, Hui; Ding, Ran; Luo, Xiao-qing

2015-09-22

The transoral atlantoaxial reduction plate (TARP) fixation has been introduced to achieve reduction, decompression, fixation and fusion of C1-C2 through a transoral-only approach. However, it may also be associated with potential disadvantages, including dysphagia and load shielding of the bone graft. To prevent potential disadvantages related to TARP fixation, a novel transoral atlantoaxial fusion cage with integrated plate (Cage + Plate) device for stabilization of the C1-C2 segment is designed. The aims of the present study were to compare the biomechanical differences between Cage + Plate device and Cage + TARP device for the treatment of basilar invagination (BI) with irreducible atlantoaxial dislocation (IAAD). A detailed, nonlinear finite element model (FEM) of the intact upper cervical spine had been developed and validated. Then a FEM of an unstable BI model treated with Cage + Plate fixation, was compared to that with Cage + TARP fixation. All models were subjected to vertical load with pure moments in flexion, extension, lateral bending and axial rotation. Range of motion (ROM) of C1-C2 segment and maximum von Mises Stress of the C2 endplate and bone graft were quantified for the two devices. Both devices significantly reduced ROM compared with the intact state. In comparison with the Cage + Plate model, the Cage + TARP model reduced the ROM by 82.5 %, 46.2 %, 10.0 % and 74.3 % in flexion, extension, lateral bending, and axial rotation. The Cage + Plate model showed a higher increase stresses on C2 endplate and bone graft than the Cage + TARP model in all motions. Our results indicate that the novel Cage + Plate device may provide lower biomechanical stability than the Cage + TARP device in flexion, extension, and axial rotation, however, it may reduce stress shielding of the bone graft for successful fusion and minimize the risk of postoperative dysphagia. Clinical trials are now required to validate the reproducibility and advantages of our findings using this anchored cage for the treatment of BI with IAAD.

Computer program to compute buckling loads of simply supported anisotropic plates

NASA Technical Reports Server (NTRS)

Chamis, C. C.

1973-01-01

Program handles several types of composites and several load conditions for each plate, both compressive or tensile membrane loads, and bending-stretching coupling via the concept of reduced bending rigidities. Vibration frequencies of homogeneous or layered anisotropic plates can be calculated by slightly modifying the program.

Self-bending elastic waves and obstacle circumventing in wireless power transfer

NASA Astrophysics Data System (ADS)

Tol, S.; Xia, Y.; Ruzzene, M.; Erturk, A.

2017-04-01

We demonstrate self-bending of elastic waves along convex trajectories by means of geometric and phased arrays. Potential applications include ultrasonic imaging and manipulation, wave focusing, and wireless power transfer around obstacles. The basic concept is illustrated through a geometric array, which is designed to implement a phase delay profile among the array elements that leads to self-bending along a specified circular trajectory. Experimental validation is conducted for the lowest asymmetric Lamb wave mode in a thin plate over a range of frequencies to investigate the bandwidth of the approach. Experiments also illustrate the functionality of the array as a transmitter to deliver elastic wave energy to a receiver/harvester located behind a large obstacle for electrical power extraction. It is shown that the trajectory is not distorted by the presence of the obstacle and circumventing is achieved. A linear phased array counterpart of the geometric array is then constructed to illustrate the concept by imposing proper time delays to the array elements, which allows the generation of different trajectories using the same line source. This capability is demonstrated by tailoring the path diameter in the phased array setting, which offers the flexibility and versatility to induce a variety of convex trajectories for self-bending elastic waves.

Can Thermal Bending Fracture Ice Shelves?

NASA Astrophysics Data System (ADS)

MacAyeal, D. R.; Sergienko, O. V.; Banwell, A. F.; Willis, I.; Macdonald, G. J.; Lin, J.

2017-12-01

Visco-elastic plates will bend if the temperature on one side is cooled. If the plate is constrained to float, as for sea ice floes, this bending will lead to tensile stresses that can fracture the ice. The hydroacoustic regime below sea ice displays increased fracture-sourced noise when air temperatures above the ice cools with the diurnal cycle. The McMurdo Ice Shelf, Antarctica, also displays a massive increase in seismicity during the cooling phase of the diurnal cycle, and this motivates the question: Can surface cooling (or other forcing with thermal consequences) drive through-thickness fracture leading to iceberg calving? Past study of this question for sea ice gives an upper limit of ice-plate thickness (order meters) for which diurnal-scale thermal bending fracture can occur; but could cooling with longer time scales induce fracture of thicker ice plates? Given the seismic evidence of thermal bending fracture on the McMurdo Ice Shelf, the authors examine this question further.

Experimental Spin Testing of Integrally Damped Composite Plates

NASA Technical Reports Server (NTRS)

Kosmatka, John

1998-01-01

The experimental behavior of spinning laminated composite pretwisted plates (turbo-fan blade-like) with small (less than 10% by volume) integral viscoelastic damping patches was investigated at NASA-Lewis Research Center. Ten different plate sets were experimentally spin tested and the resulting data was analyzed. The first-four plate sets investigated tailoring patch locations and definitions to damp specific modes on spinning flat graphite/epoxy plates as a function of rotational speed. The remaining six plate sets investigated damping patch size and location on specific modes of pretwisted (30 degrees) graphite/epoxy plates. The results reveal that: (1) significant amount of damping can be added using a small amount of damping material, (2) the damped plates experienced no failures up to the tested 28,000 g's and 750,000 cycles, (3) centrifugal loads caused an increase in bending frequencies and corresponding reductions in bending damping levels that are proportional to the bending stiffness increase, and (4) the centrifugal loads caused a decrease in torsion natural frequency and increase in damping levels of pretwisted composite plates.

A preliminary study of bending stiffness alteration in shape changing nitinol plates for fracture fixation.

PubMed

Olender, Gavin; Pfeifer, Ronny; Müller, Christian W; Gösling, Thomas; Barcikowski, Stephan; Hurschler, Christof

2011-05-01

Nitinol is a promising biomaterial based on its remarkable shape changing capacity, biocompatibility, and resilient mechanical properties. Until now, very limited applications have been tested for the use of Nitinol plates for fracture fixation in orthopaedics. Newly designed fracture-fixation plates are tested by four-point bending to examine a change in equivalent bending stiffness before and after shape transformation. The goal of stiffness alterable bone plates is to optimize the healing process during osteosynthesis in situ that is customized in time of onset, percent change as well as being performed non-invasively for the patient. The equivalent bending stiffness in plates of varying thicknesses changed before and after shape transformation in the range of 24-73% (p values <0.05 for all tests). Tests on a Nitinol plate of 3.0 mm increased in stiffness from 0.81 to 0.98 Nm² (corresponding standard deviation 0.08 and 0.05) and shared a good correlation to results from numerical calculation. The stiffness of the tested fracture-fixation plates can be altered in a consistent matter that would be predicted by determining the change of the cross-sectional area moment of inertia.

Electrically-induced stresses and deflection in multiple plates

NASA Astrophysics Data System (ADS)

Hu, Jih-Perng; Tichler, P. R.

1992-04-01

Thermohydraulic tests are being planned at the High Flux Beam Reactor of Brookhaven National Laboratory, in which direct electrical heating of metal plates will simulate decay heating in parallel plate-type fuel elements. The required currents are high if plates are made of metal with a low electrical resistance, such as aluminum. These high currents will induce either attractive or repulsive forces between adjacent current-carrying plates. Such forces, if strong enough, will cause the plates to deflect and so change the geometry of the coolant channel between the plates. Since this is undesirable, an analysis was made to evaluate the magnitude of the deflection and related stresses. In contrast to earlier publications in which either a concentrated or a uniform load was assumed, in this paper an exact force distribution on the plate is analytically solved and then used for stress and deflection calculations, assuming each plate to be a simply supported beam. Results indicate that due to superposition of the induced forces between plates in a multiple-and-parallel plate array, the maximum deflection and bending stress occur at the midpoint of the outermost plate. The maximum shear stress, which is inversely proportional to plate thickness, occurs at both ends of the outermost plate.

How broad and deep is the region of chemical alteration of oceanic plates at trenches?

NASA Astrophysics Data System (ADS)

Ranero, C. R.; Grevemeyer, I.; Barckhausen, U.

2017-12-01

Different lines of evidence indicate that oceanic plates are affected by pervasive bending-related deformation approaching ocean trenches. Results from active-seismic work support that deformation provides paths for exchange between hydrosphere and lithosphere, possibly causing chemical alteration of the incoming lithosphere. Much work focused on the potential transformation of peridotite to serpentine in the uppermost mantle of incoming plates, but there is no consensus on the region where it may occur or the intensity of alteration, let alone on limiting factors for the process. Teleseismic (large-great) earthquakes with normal-fault mechanism in the outer rise region have been often called to speculate on the depth of penetration of plate hydration. However, large-great outer-rise earthquakes may be related to stress changes due to slab pull after decoupling along the inter-plate boundary, and not necessarily controlled by bending stresses only. If so, the majority of the time the depth of water percolation may be related to local bending stresses expressed by micro-earthquakes rather than large events. Seismic images and multibeam bathymetry from lithosphere of similar thermal thickness from different trenches display a remarkable variability of the intensity of bending-related deformation along the subduction zones where plate age does not change significantly indicating that the intensity of deformation (not the depth) and perhaps hydration is very variable in space and not controlled by plate age. Seismic images showing hundreds of kilometers perpendicular to the trench into the incoming plate show that the bending-related deformation reaches mantle under the outer rise, well before the lithosphere plunges into the trench and develops the marked bend-faulting fabric observable in bathymetric maps. Thus, alteration occurs in a hundreds-of-km wide area, with deformation intensity related to local characteristics, and deformation depth to plate age.

Analysis of a Circular Composite Disk Subjected to Edge Rotations and Hydrostatic Pressure

NASA Technical Reports Server (NTRS)

Oliver, Stanley T.

2004-01-01

The structural analysis results for a graphite/epoxy quasi-isotropic circular plate subjected to a forced rotation at the boundary and pressure is presented. The analysis is to support a specialized material characterization test for composite cryogenic tanks. Finite element models were used to ensure panel integrity and determine the pressure necessary to achieve a predetermined equal biaxial strain value. The displacement results due to the forced rotation at the boundary led to a detailed study of the bending stiffness matrix [D]. The variation of the bending stiffness terms as a function of angular position is presented graphically, as well as, an illustrative technique of considering the laminate as an I-beam.

Surface and through crack problems in orthotropic plates

NASA Technical Reports Server (NTRS)

Erdogan, F.; Wu, B.-H.

1988-01-01

The present treatment of the general mode I crack problem in bending- and membrane-loaded orthotropic plates proceeds by formulating the bending problem for a series of planar and through-cracks; by independently varying the six independent constants, the effect of material orthotropy on the stress intensity factor is determined. The surface-crack problem is then formulated by means of the line-spring model, using a transverse-shear theory of plate bending. Attention is given to composite laminates with through-cracks or semielliptic surface cracks. A significant effect is noted for material orthotropy.

A note on the effect of bending stiffness of stringers attached to a plate with a crack

NASA Technical Reports Server (NTRS)

Arin, K.

1974-01-01

An infinite stringer partially bonded to a plate through a layer of adhesive is considered. The stringer had bending as well as longitudinal stiffness. The effect of the stringer's bending rigidity on the stress intensity factor at the tip of the crack is illustrated. Shear stress distribution between the plate and the stringer and the stress intensity factors are obtained from the solution of a system of Fredholm integral equations. The continuity of displacements along the line of bond is represented by the equations.

On the correct representation of bending and axial deformation in the absolute nodal coordinate formulation with an elastic line approach

NASA Astrophysics Data System (ADS)

Gerstmayr, Johannes; Irschik, Hans

2008-12-01

In finite element methods that are based on position and slope coordinates, a representation of axial and bending deformation by means of an elastic line approach has become popular. Such beam and plate formulations based on the so-called absolute nodal coordinate formulation have not yet been verified sufficiently enough with respect to analytical results or classical nonlinear rod theories. Examining the existing planar absolute nodal coordinate element, which uses a curvature proportional bending strain expression, it turns out that the deformation does not fully agree with the solution of the geometrically exact theory and, even more serious, the normal force is incorrect. A correction based on the classical ideas of the extensible elastica and geometrically exact theories is applied and a consistent strain energy and bending moment relations are derived. The strain energy of the solid finite element formulation of the absolute nodal coordinate beam is based on the St. Venant-Kirchhoff material: therefore, the strain energy is derived for the latter case and compared to classical nonlinear rod theories. The error in the original absolute nodal coordinate formulation is documented by numerical examples. The numerical example of a large deformation cantilever beam shows that the normal force is incorrect when using the previous approach, while a perfect agreement between the absolute nodal coordinate formulation and the extensible elastica can be gained when applying the proposed modifications. The numerical examples show a very good agreement of reference analytical and numerical solutions with the solutions of the proposed beam formulation for the case of large deformation pre-curved static and dynamic problems, including buckling and eigenvalue analysis. The resulting beam formulation does not employ rotational degrees of freedom and therefore has advantages compared to classical beam elements regarding energy-momentum conservation.

Diffraction of Harmonic Flexural Waves in a Cracked Elastic Plate Carrying Electrical Current

NASA Technical Reports Server (NTRS)

Ambur, Damodar R.; Hasanyan, Davresh; Librescu, iviu; Qin, Zhanming

2005-01-01

The scattering effect of harmonic flexural waves at a through crack in an elastic plate carrying electrical current is investigated. In this context, the Kirchhoffean bending plate theory is extended as to include magnetoelastic interactions. An incident wave giving rise to bending moments symmetric about the longitudinal z-axis of the crack is applied. Fourier transform technique reduces the problem to dual integral equations, which are then cast to a system of two singular integral equations. Efficient numerical computation is implemented to get the bending moment intensity factor for arbitrary frequency of the incident wave and of arbitrary electrical current intensity. The asymptotic behaviour of the bending moment intensity factor is analysed and parametric studies are conducted.

The Effect of Applied Tensile Stress on Localized Corrosion in Sensitized AA5083

DTIC Science & Technology

2015-09-01

of stainless steel 4-point bending rig used to apply elastic stress to aluminum plate samples. (Bottom) Stress- strain data based on displacement and...ASTM-G39, from [25]. ..........................20 Figure 13. Photograph of stainless steel 4-point bending rig used to apply elastic stress to...aluminum plate samples, from [8]. ....................................................20 Figure 14. Photograph of stainless steel 4-point bending rig

Nonlinear thermal dynamic analysis of graphit/aluminum composite plates

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tenneti, R.; Chandrashekhara, K.

1994-09-01

Because of the increased application of composite materials in high-temperature environments, the thermoelastic analysis of laminated composite structures is important. Many researchers have applied the classical lamination theory to analyze laminated plates under thermomechanical loading, which neglects shear deformation effects. The transverse shear deformation effects are not negligible as the ratios of inplane elastic modulus to transverse shear modulus are relatively large for fiber-reinforced composite laminates. The application of first-order shear deformation theory for the thermoelastic analysis of laminated plates has been reported by only a few investigators. Reddy and Hsu have considered the thermal bending of laminated plates. Themore » analytical and finite element solutions for the thermal bucking of laminated plates have been reported by Tauchert and Chandrashekara, respectively. However, the first-order shear deformation theory, based on the assumption of constant distribution of transverse shear through the thickness, requires a shear correction factor to account for the parabolic shear strain distribution. Higher order theories have been proposed which eliminate the need for a shear correction factor. In the present work, nonlinear dynamic analysis of laminated plates subjected to rapid heating is investigated using a higher order shear deformation theory. A C(sup 0) finite element model with seven degrees of freedom per node is implmented and numerical results are presented for laminated graphite/aluminum plates.« less

Formation of Island Arc-Trench System due to Plate Subduction on the Basis of Elastic Dislocation Theory

NASA Astrophysics Data System (ADS)

Fukahata, Y.; Matsu'ura, M.

2015-12-01

The most conspicuous cumulative deformation in subduction zones is the formation of island arc-trench system. A pair of anomalies in topography and free-air gravity, high in the arc and low around the trench, is observed without exceptions all over the world. Since the 1960s, elastic dislocation theory has been widely used to interpret coseismic crustal deformation. For the modeling of longer-term crustal deformation, it is necessary to consider viscoelastic properties of the asthenosphere. By simply applying elastic-viscoelastic dislocation theory to plate subduction, Matsu'ura and Sato (1989, GJI) have shown that some crustal deformation remains after the completion of one earthquake cycle, which means that crustal deformation accumulates with time in a long term due to plate subduction. In fact, by constructing a plate interface model in and around Japan, Hashimoto, Fukui and Matsu'ura (2004, PAGEOPH) have demonstrated that the computed vertical displacements due to steady plate subduction well explain the observed free-air gravity anomaly pattern. Recently, we got a lucid explanation of crustal deformation due to plate subduction. In subduction zones, oceanic plates bend and descend into the mantle. Because the bending of oceanic plates is usually not spontaneous, there exists kinematic interaction between the oceanic and overriding plates, which causes cumulative deformation of the overriding plate. This may be understood based on the law of action and reaction: one is bending of an oceanic plate and the other is deformation of the overriding plate. As a special case, it is useful to consider plate subduction along a part of true circle. In this case, crustal deformation due to steady subduction is solely caused by the effect of gravity, because dislocation along a circle does not cause any intrinsic internal deformation. When an oceanic plate is descending along an arcuate plate interface from the right-hand side, according to dislocation theory, the oceanic plate rotates anti-clockwise and the overriding plate rotates clockwise. The gravity, however, requires both plates at a distance from the trench to remain in the original gravitational equilibrium, which results in upward bending of both plates. As subduction proceeds, the deformation of the upward bending accumulates with time.

Thermochronology, Uplift and Erosion at the Australian-Pacific Plate Boundary Alpine Fault restraining bend, New Zealand

NASA Astrophysics Data System (ADS)

Sagar, M. W.; Seward, D.; Norton, K. P.

2016-12-01

The 650 km-long Australian-Pacific plate boundary Alpine Fault is remarkably straight at a regional scale, except for a prominent S-shaped bend in the northern South Island. This is a restraining bend and has been referred to as the `Big Bend' due to similarities with the Transverse Ranges section of the San Andreas Fault. The Alpine Fault is the main source of seismic hazard in the South Island, yet there are no constraints on slip rates at the Big Bend. Furthermore, the timing of Big Bend development is poorly constrained to the Miocene. To address these issues we are using the fission-track (FT) and 40Ar/39Ar thermochronometers, together with basin-averaged cosmogenic nuclide 10Be concentrations to constrain the onset and rate of Neogene-Quaternary exhumation of the Australian and Pacific plates at the Big Bend. Exhumation rates at the Big Bend are expected to be greater than those for adjoining sections of the Alpine Fault due to locally enhanced shortening. Apatite FT ages and modelled thermal histories indicate that exhumation of the Australian Plate had begun by 13 Ma and 3 km of exhumation has occurred since that time, requiring a minimum exhumation rate of 0.2 mm/year. In contrast, on the Pacific Plate, zircon FT cooling ages suggest ≥7 km of exhumation in the past 2-3 Ma, corresponding to a minimum exhumation rate of 2 mm/year. Preliminary assessment of stream channel gradients either side of the Big Bend suggests equilibrium between uplift and erosion. The implication of this is that Quaternary erosion rates estimated from 10Be concentrations will approximate uplift rates. These uplift rates will help to better constrain the dip-slip rate of the Alpine Fault, which will allow the National Seismic Hazard Model to be updated.

Analysis for stresses and buckling of heated composite stiffened panels and other structures, phase 3

NASA Technical Reports Server (NTRS)

Viswanathan, A. V.; Tamekuni, M.

1973-01-01

Analytical methods based on linear theory are presented for predicting the thermal stresses in and the buckling of heated structures with arbitrary uniform cross section. The structure is idealized as an assemblage of laminated plate-strip elements, curved and planar, and beam elements. Uniaxially stiffened plates and shells of arbitrary cross section are typical examples. For the buckling analysis the structure or selected elements may be subjected to mechanical loads, in additional to thermal loads, in any desired combination of inplane transverse load and axial compression load. The analysis is also applicable to stiffened structures under inplane loads varying through the cross section, as in stiffened shells under bending. The buckling analysis is general and covers all modes of instability. The analysis has been applied to a limited number of problems and the results are presented. These while showing the validity and the applicability of the method do not reflect its full capability.

Pressure distribution under flexible polishing tools. I - Conventional aspheric optics

NASA Astrophysics Data System (ADS)

Mehta, Pravin K.; Hufnagel, Robert E.

1990-10-01

The paper presents a mathematical model, based on Kirchoff's thin flat plate theory, developed to determine polishing pressure distribution for a flexible polishing tool. A two-layered tool in which bending and compressive stiffnesses are equal is developed, which is formulated as a plate on a linearly elastic foundation. An equivalent eigenvalue problem and solution for a free-free plate are created from the plate formulation. For aspheric, anamorphic optical surfaces, the tool misfit is derived; it is defined as the result of movement from the initial perfect fit on the optic to any other position. The Polisher Design (POD) software for circular tools on aspheric optics is introduced. NASTRAN-based finite element analysis results are compared with the POD software, showing high correlation. By employing existing free-free eigenvalues and eigenfunctions, the work may be extended to rectangular polishing tools as well.

Effect of screw position on single cycle to failure in bending and torsion of a locking plate-rod construct in a synthetic feline femoral gap model.

PubMed

Niederhäuser, Simone K; Tepic, Slobodan; Weber, Urs T

2015-05-01

To evaluate the effect of screw position on strength and stiffness of a combination locking plate-rod construct in a synthetic feline femoral gap model. 30 synthetic long-bone models derived from beechwood and balsa wood. 3 constructs (2 locking plate-rod constructs and 1 locking plate construct; 10 specimens/construct) were tested in a diaphyseal bridge plating configuration by use of 4-point bending and torsion. Variables included screw position (near the fracture gap and far from the fracture gap) and application of an intramedullary pin. Constructs were tested to failure in each loading mode to determine strength and stiffness. Failure was defined as plastic deformation of the plate or breakage of the bone model or plate. Strength, yield angle, and stiffness were compared by use of a Wilcoxon test. Placement of screws near the fracture gap did not increase bending or torsional stiffness in the locking plate-rod constructs, assuming the plate was placed on the tension side of the bone. Addition of an intramedullary pin resulted in a significant increase in bending strength of the construct. Screw positioning did not have a significant effect on any torsion variables. Results of this study suggested that, in the investigated plate-rod construct, screw insertion adjacent to the fracture lacked mechanical advantages over screw insertion at the plate ends. For surgeons attempting to minimize soft tissue dissection, the decision to make additional incisions for screw placement should be considered with even more caution.

Reissner-Mindlin Legendre Spectral Finite Elements with Mixed Reduced Quadrature

DOE Office of Scientific and Technical Information (OSTI.GOV)

Brito, K. D.; Sprague, M. A.

2012-10-01

Legendre spectral finite elements (LSFEs) are examined through numerical experiments for static and dynamic Reissner-Mindlin plate bending and a mixed-quadrature scheme is proposed. LSFEs are high-order Lagrangian-interpolant finite elements with nodes located at the Gauss-Lobatto-Legendre quadrature points. Solutions on unstructured meshes are examined in terms of accuracy as a function of the number of model nodes and total operations. While nodal-quadrature LSFEs have been shown elsewhere to be free of shear locking on structured grids, locking is demonstrated here on unstructured grids. LSFEs with mixed quadrature are, however, locking free and are significantly more accurate than low-order finite-elements for amore » given model size or total computation time.« less

Full title: Biomechanical comparison between stainless steel, titanium and carbon-fiber reinforced polyetheretherketone volar locking plates for distal radius fractures.

PubMed

Mugnai, Raffaele; Tarallo, Luigi; Capra, Francesco; Catani, Fabio

2018-05-25

As the popularity of volar locked plate fixation for distal radius fractures has increased, so have the number and variety of implants, including variations in plate design, the size and angle of the screws, the locking screw mechanism, and the material of the plates. carbon-fiber reinforced polyetheretherketone (CFR-PEEK) plate features similar biomechanical properties to metallic plates, representing, therefore, an optimal alternative for the treatment of distal radius fractures. three different materials-composed plates were evaluated: stainless steel volar lateral column (Zimmer); titanium DVR (Hand Innovations); CFR-PEEK DiPHOS-RM (Lima Corporate). Six plates for each type were implanted in sawbones and an extra-articular rectangular osteotomy was created. Three plates for each material were tested for load to failure and bending stiffness in axial compression. Moreover, 3 constructs for each plate were evaluated after dynamically loading for 6000 cycles of fatigue. the mean bending stiffness pre-fatigue was significantly higher for the stainless steel plate. The titanium plate yielded the higher load to failure both pre and post fatigue. After cyclic loading, the bending stiffness increased by a mean of 24% for the stainless steel plate; 33% for the titanium; and 17% for the CFR-PEEK plate. The mean load to failure post-fatigue increased by a mean of 10% for the stainless steel and 14% for CFR-PEEK plates, whereas it decreased (-16%) for the titanium plate. Statistical analysis between groups reported significant values (p <.001) for all comparisons except for Hand Innovations vs. Zimmer bending stiffness post fatigue (p = .197). the significant higher load to failure of the titanium plate, makes it indicated for patients with higher functional requirements or at higher risk of trauma in the post-operative period. The CFR-PEEK plate showed material-specific disadvantages, represented by little tolerance to plastic deformation, and lower load to failure. N/A. Copyright © 2018. Published by Elsevier Masson SAS.

Biomechanical comparison of double-row locking plates versus single- and double-row non-locking plates in a comminuted metacarpal fracture model.

PubMed

Gajendran, Varun K; Szabo, Robert M; Myo, George K; Curtiss, Shane B

2009-12-01

Open or unstable metacarpal fractures frequently require open reduction and internal fixation. Locking plate technology has improved fixation of unstable fractures in certain settings. In this study, we hypothesized that there would be a difference in strength of fixation using double-row locking plates compared with single- and double-row non-locking plates in comminuted metacarpal fractures. We tested our hypothesis in a gap metacarpal fracture model simulating comminution using fourth-generation, biomechanical testing-grade composite sawbones. The metacarpals were divided into 6 groups of 15 bones each. Groups 1 and 4 were plated with a standard 6-hole, 2.3-mm plate in AO fashion. Groups 2 and 5 were plated with a 6-hole double-row 3-dimensional non-locking plate with bicortical screws aimed for convergence. Groups 3 and 6 were plated with a 6-hole double-row 3-dimensional locking plate with unicortical screws. The plated metacarpals were then tested to failure against cantilever apex dorsal bending (groups 1-3) and torsion (groups 4-6). The loads to failure in groups 1 to 3 were 198 +/- 18, 223 +/- 29, and 203 +/- 19 N, respectively. The torques to failure in groups 4 to 6 were 2,033 +/- 155, 3,190 +/- 235, and 3,161 +/- 268 N mm, respectively. Group 2 had the highest load to failure, whereas groups 5 and 6 shared the highest torques to failure (p < .05). Locking and non-locking double-row plates had equivalent bending and torsional stiffness, significantly higher than observed for the single-row non-locking plate. No other statistical differences were noted between groups. When subjected to the physiologically relevant forces of apex dorsal bending and torsion in a comminuted metacarpal fracture model, double-row 3-dimensional non-locking plates provided superior stability in bending and equivalent stability in torsion compared with double-row 3-dimensional locking plates, whereas single-row non-locking plates provided the least stability.

Analysis of metal-matrix composite structures. I - Micromechanics constitutive theory. II - Laminate analyses

NASA Technical Reports Server (NTRS)

Arenburg, R. T.; Reddy, J. N.

1991-01-01

The micromechanical constitutive theory is used to examine the nonlinear behavior of continuous-fiber-reinforced metal-matrix composite structures. Effective lamina constitutive relations based on the Abouli micromechanics theory are presented. The inelastic matrix behavior is modeled by the unified viscoplasticity theory of Bodner and Partom. The laminate constitutive relations are incorporated into a first-order deformation plate theory. The resulting boundary value problem is solved by utilizing the finite element method. Attention is also given to computational aspects of the numerical solution, including the temporal integration of the inelastic strains and the spatial integration of bending moments. Numerical results the nonlinear response of metal matrix composites subjected to extensional and bending loads are presented.

A shell approach for fibrous reinforcement forming simulations

NASA Astrophysics Data System (ADS)

Liang, B.; Colmars, J.; Boisse, P.

2018-05-01

Because of the slippage between fibers, the basic assumptions of classical plate and shell theories are not verified by fiber reinforcement during a forming. However, simulations of reinforcement forming use shell finite elements when wrinkles development is important. A shell formulation is proposed for the forming simulations of continuous fiber reinforcements. The large tensile stiffness leads to the quasi inextensibility in the fiber directions. The fiber bending stiffness determines the curvature of the reinforcement. The calculation of tensile and bending virtual works are based on the precise geometry of the single fiber. Simulations and experiments are compared for different reinforcements. It is shown that the proposed fibrous shell approach not only correctly simulates the deflections but also the rotations of the through thickness material normals.

Electrically-induced stresses and deflection in multiple plates

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hu, Jih-Perng; Tichler, P.R.

Thermohydraulic tests are being planned at the High Flux Beam Reactor of Brookhaven National Laboratory, in which direct electrical heating of metal plates will simulate decay heating in parallel plate-type fuel elements. The required currents are high if plates are made of metal with a low electrical resistance, such as aluminum. These high currents will induce either attractive or repulsive forces between adjacent current-carrying plates. Such forces, if strong enough, will cause the plates to deflect and so change the geometry of the coolant channel between the plates. Since this is undesirable, an analysis has been made to evaluate themore » magnitude of the deflection and related stresses. In contrast to earlier publications in which either a concentrated or a uniform load was assumed, in this paper an exact force distribution on the plate is analytically solved and then used for stress and deflection calculations, assuming each plate to be a simply supported beam. Results indicate that due to superposition of the induced forces between plates in a multiple-and-parallel plate array, the maximum deflection and bending stress occur at the midpoint of the outermost plate. The maximum shear stress, which is inversely proportional to plate thickness, occurs at both ends of the outermost plate.« less

Combined mode I stress intensity factors of slanted cracks

NASA Astrophysics Data System (ADS)

Ismail, A. E.; Rahman, M. Q. Abdul; Ghazali, M. Z. Mohd; Zulafif Rahim, M.; Rasidi Ibrahim, M.; Fahrul Hassan, Mohd; Nor, Nik Hisyamudin Muhd; Ariffin, A. M. T.; Zaini Yunos, Muhamad

2017-08-01

The solutions of stress intensity factors (SIFs) for slanted cracks in plain strain plate are hard to find in open literature. There are some previous solutions of SIFs available, however the studies are not completed except for the case of plain stress. The slanted cracks are modelled numerically using ANSYS finite element program. There are ten slanted angles and seven relative crack depths are used and the plate contains cracks which is assumed to fulfil the plain strain condition. The plate is then stressed under tension and bending loading and the SIFs are determined according to the displacement extrapolation method. Based on the numerical analysis, both slanted angles and relative crack length, a/L played an important role in determining the modes I and II SIFs. As expected the SIFs increased when a/L is increased. Under tension force, the introduction of slanted angles increased the SIFs. Further increment of angles reduced the SIFs however they are still higher than the SIFs obtained using normal cracks. Under bending moment, the present of slanted angles are significantly reduced the SIFs compared with the normal cracks. Under similar loading, mode II SIFs increased as function of a/L and slanted angles where increasing such parameters increasing the mode II SIFs.

An Investigation into the Application of Generalized Differential Quadrature Method to Bending Analysis of Composite Sandwich Plates

NASA Astrophysics Data System (ADS)

Ghassemi, Aazam; Yazdani, Mostafa; Hedayati, Mohamad

2017-12-01

In this work, based on the First Order Shear Deformation Theory (FSDT), an attempt is made to explore the applicability and accuracy of the Generalized Differential Quadrature Method (GDQM) for bending analysis of composite sandwich plates under static loading. Comparative studies of the bending behavior of composite sandwich plates are made between two types of boundary conditions for different cases. The effects of fiber orientation, ratio of thickness to length of the plate, the ratio of thickness of core to thickness of the face sheet are studied on the transverse displacement and moment resultants. As shown in this study, the role of the core thickness in deformation of these plates can be reversed by the stiffness of the core in comparison with sheets. The obtained graphs give very good results due to optimum design of sandwich plates. In Comparison with existing solutions, fast convergent rates and high accuracy results can be achieved by the GDQ method.

Biomechanical comparison of orthogonal versus parallel double plating systems in intraarticular distal humerus fractures.

PubMed

Atalar, Ata C; Tunalı, Onur; Erşen, Ali; Kapıcıoğlu, Mehmet; Sağlam, Yavuz; Demirhan, Mehmet S

2017-01-01

In intraarticular distal humerus fractures, internal fixation with double plates is the gold standard treatment. However the optimal plate configuration is not clear in the literature. The aim of this study was to compare the biomechanical stability of the parallel and the orthogonal anatomical locking plating systems in intraarticular distal humerus fractures in artificial humerus models. Intraarticular distal humerus fracture (AO13-C2) with 5 mm metaphyseal defect was created in sixteen artificial humeral models. Models were fixed with either orthogonal or parallel plating systems with locking screws (Acumed elbow plating systems). Both systems were tested for their stiffness with loads in axial compression, varus, valgus, anterior and posterior bending. Then plastic deformation after cyclic loading in posterior bending and load to failure in posterior bending were tested. The failure mechanisms of all the samples were observed. Stiffness values in every direction were not significantly different among the orthogonal and the parallel plating groups. There was no statistical difference between the two groups in plastic deformation values (0.31 mm-0.29 mm) and load to failure tests in posterior bending (372.4 N-379.7 N). In the orthogonal plating system most of the failures occurred due to the proximal shaft fracture, whereas in the parallel plating system failure occurred due to the shift of the most distal screw in proximal fragment. Our study showed that both plating systems had similar biomechanical stabilities when anatomic plates with distal locking screws were used in intraarticular distal humerus fractures in artificial humerus models. Copyright © 2016 Turkish Association of Orthopaedics and Traumatology. Production and hosting by Elsevier B.V. All rights reserved.

Moment distributions around holes in symmetric composite laminates subjected to bending moments

NASA Technical Reports Server (NTRS)

Prasad, C. B.; Shuart, M. J.

1989-01-01

An analytical investigation of the effects of holes on the moment distribution of symmetric composite laminates subjected to bending moments is described. A general, closed-form solution for the moment distribution of an infinite anisotropic plate is derived, and this solution is used to determine stress distributions both on the hole boundary and throughout the plate. Results are presented for several composite laminates that have holes and are subjected to either pure bending or cylindrical bending. Laminates with a circular hole or with an elliptical hole are studied. Laminate moment distributions are discussed, and ply stresses are described.

Low cost fabrication development for oxide dispersion strengthened alloy vanes

NASA Technical Reports Server (NTRS)

Perkins, R. J.; Bailey, P. G.

1978-01-01

Viable processes were developed for secondary working of oxide dispersion strengthened (ODS) alloys to near-net shapes (NNS) for aircraft turbine vanes. These processes were shown capable of producing required microstructure and properties for vane applications. Material cost savings of 40 to 50% are projected for the NNS process over the current procedures which involve machining from rectangular bar. Additional machining cost savings are projected. Of three secondary working processes evaluated, directional forging and plate bending were determined to be viable NNS processes for ODS vanes. Directional forging was deemed most applicable to high pressure turbine (HPT) vanes with their large thickness variations while plate bending was determined to be most cost effective for low pressure turbine (LPT) vanes because of their limited thickness variations. Since the F101 LPT vane was selected for study in this program, development of plate bending was carried through to establishment of a preliminary process. Preparation of ODS alloy plate for bending was found to be a straight forward process using currently available bar stock, providing that the capability for reheating between roll passes is available. Advanced ODS-NiCrAl and ODS-FeCrAl alloys were utilized on this program. Workability of all alloys was adequate for directional forging and plate bending, but only the ODS-FeCrAl had adequate workability for shaped preform extrustion.

Solving the Problem of Linear Viscoelasticity for Piecewise-Homogeneous Anisotropic Plates

NASA Astrophysics Data System (ADS)

Kaloerov, S. A.; Koshkin, A. A.

2017-11-01

An approximate method for solving the problem of linear viscoelasticity for thin anisotropic plates subject to transverse bending is proposed. The method of small parameter is used to reduce the problem to a sequence of boundary problems of applied theory of bending of plates solved using complex potentials. The general form of complex potentials in approximations and the boundary conditions for determining them are obtained. Problems for a plate with elliptic elastic inclusions are solved as an example. The numerical results for a plate with one, two elliptical (circular), and linear inclusions are analyzed.

Benchmark Computation and Finite Element Performance Evaluation for a Rhombic Plate Bending Problem

DTIC Science & Technology

1987-09-01

Physical Science and Technology University of Maryland, College Park, MD 20742, USA and Dip. Matematica - Universita di Pavia - 27100 Pavia - ITALY DTIC...University of Maryland, College Park,, MD 20742, USA , and Dip. Matematica - Universita di Pavia - 27100 Pavia - ITALY SFor Oe" -- 4- I , CA& 11 --l...drawn when based on the state of the art of both theoretical and experience field. The reliability has to be understood not only with respect to a

Modelling of thick composites using a layerwise laminate theory

NASA Technical Reports Server (NTRS)

Robbins, D. H., Jr.; Reddy, J. N.

1993-01-01

The layerwise laminate theory of Reddy (1987) is used to develop a layerwise, two-dimensional, displacement-based, finite element model of laminated composite plates that assumes a piecewise continuous distribution of the tranverse strains through the laminate thickness. The resulting layerwise finite element model is capable of computing interlaminar stresses and other localized effects with the same level of accuracy as a conventional 3D finite element model. Although the total number of degrees of freedom are comparable in both models, the layerwise model maintains a 2D-type data structure that provides several advantages over a conventional 3D finite element model, e.g. simplified input data, ease of mesh alteration, and faster element stiffness matrix formulation. Two sample problems are provided to illustrate the accuracy of the present model in computing interlaminar stresses for laminates in bending and extension.

Design of beam deflector, splitters, wave plates and metalens using photonic elements with dielectric metasurface

NASA Astrophysics Data System (ADS)

Zhang, Qing; Li, Maozhong; Liao, Tingdi; Cui, Xudong

2018-03-01

Under the trend of miniaturization and reduction of system complexity, conventional bulky photonic elements are expected to be replaced by new compact and ultrathin dielectric metasurface elements. In this letter, we propose an αTiO2 dielectric metasurface (DM) platform that could be exploited to design high efficiency wave-front control devices at visible wavelength. Combining with fundamental principles and full wave simulations (Lumerical FDTD 3D solver ®), we successfully realize four DM devices, such as anomalous beam deflectors, polarization insensitive metalens, wave plates and polarization beam splitters. All these devices can achieve high transmission efficiencies (larger than 80%). Among them, the anomalous refraction beam deflectors can bend light propagation to any desired directions; the polarization insensitive metalens maintains diffraction limited focus (focal spot as small as 0.67 λ); the quarter-wave and half-wave plates have broadband working wavelengths from 550 to 1000 nm; and the polarization beam splitter can split an arbitrarily polarized incident beam into two orthogonally polarized beams, the TM components is deflected to the right side, and the TE components is deflected to the left side. These devices may find applications in the areas of imaging, polarization control, spectroscopy, and on-chip optoelectronic systems etc., and our studies may richen the design of all-dielectric optical elements at visible wavelength.

Linking Incoming Plate Faulting and Intermediate Depth Seismicity

NASA Astrophysics Data System (ADS)

Kwong, K. B.; van Zelst, I.; Tong, X.; Eimer, M. O.; Naif, S.; Hu, Y.; Zhan, Z.; Boneh, Y.; Schottenfels, E.; Miller, M. S.; Moresi, L. N.; Warren, J. M.; Wiens, D. A.

2017-12-01

Intermediate depth earthquakes, occurring between 70-350 km depth, are often attributed to dehydration reactions within the subducting plate. It is proposed that incoming plate normal faulting associated with plate bending at the trench may control the amount of hydration in the plate by producing large damage zones that create pathways for the infiltration of seawater deep into the subducting mantle. However, a relationship between incoming plate seismicity, faulting, and intermediate depth seismicity has not been established. We compiled a global dataset consisting of incoming plate earthquake moment tensor (CMT) solutions, focal depths, bend fault spacing and offset measurements, along with plate age and convergence rates. In addition, a global intermediate depth seismicity dataset was compiled with parameters such as the maximum seismic moment and seismicity rate, as well as thicknesses of double seismic zones. The maximum fault offset in the bending region has a strong correlation with the intermediate depth seismicity rate, but a more modest correlation with other parameters such as convergence velocity and plate age. We estimated the expected rate of seismic moment release for the incoming plate faults using mapped fault scarps from bathymetry. We compare this with the cumulative moment from normal faulting earthquakes in the incoming plate from the global CMT catalog to determine whether outer rise fault movement has an aseismic component. Preliminary results from Tonga and the Middle America Trench suggest there may be an aseismic component to incoming plate bending faulting. The cumulative seismic moment calculated for the outer rise faults will also be compared to the cumulative moment from intermediate depth earthquakes to assess whether these parameters are related. To support the observational part of this study, we developed a geodynamic numerical modeling study to systematically explore the influence of parameters such as plate age and convergence rate on the offset, depth, and spacing of outer rise faults. We then compare these robust constraints on outer rise faulting to the observed widths of intermediate depth earthquakes globally.

Pacific plate motion change caused the Hawaiian-Emperor Bend

PubMed Central

Torsvik, Trond H.; Doubrovine, Pavel V.; Steinberger, Bernhard; Gaina, Carmen; Spakman, Wim; Domeier, Mathew

2017-01-01

A conspicuous 60° bend of the Hawaiian-Emperor Chain in the north-western Pacific Ocean has variously been interpreted as the result of an abrupt Pacific plate motion change in the Eocene (∼47 Ma), a rapid southward drift of the Hawaiian hotspot before the formation of the bend, or a combination of these two causes. Palaeomagnetic data from the Emperor Seamounts prove ambiguous for constraining the Hawaiian hotspot drift, but mantle flow modelling suggests that the hotspot drifted 4–9° south between 80 and 47 Ma. Here we demonstrate that southward hotspot drift cannot be a sole or dominant mechanism for formation of the Hawaiian-Emperor Bend (HEB). While southward hotspot drift has resulted in more northerly positions of the Emperor Seamounts as they are observed today, formation of the HEB cannot be explained without invoking a prominent change in the direction of Pacific plate motion around 47 Ma. PMID:28580950

Repair & Reinforcing Pallet Stringers With Metal Plates

Treesearch

John W. Clarke; Thomas E. McLain; Marshall S. White; Philip A. Araman

1993-01-01

Notches significantly reduce the bending strength and life expectancy of stringer-class pallets with partial 4-way entry. Common failures include cracking between the notches (BN), bending failures in the region above the notch (AN) and splitting of end feet. In recent years, several suppliers and manufacturers of metal connector plates (MCPs) have developed equipment...

Modeling bicortical screws under a cantilever bending load.

PubMed

James, Thomas P; Andrade, Brendan A

2013-12-01

Cyclic loading of surgical plating constructs can precipitate bone screw failure. As the frictional contact between the plate and the bone is lost, cantilever bending loads are transferred from the plate to the head of the screw, which over time causes fatigue fracture from cyclic bending. In this research, analytical models using beam mechanics theory were developed to describe the elastic deflection of a bicortical screw under a statically applied load. Four analytical models were developed to simulate the various restraint conditions applicable to bicortical support of the screw. In three of the models, the cortical bone near the tip of the screw was simulated by classical beam constraints (1) simply supported, (2) cantilever, and (3) split distributed load. In the final analytical model, the cortices were treated as an elastic foundation, whereby the response of the constraint was proportional to screw deflection. To test the predictive ability of the new analytical models, 3.5 mm cortical bone screws were tested in a synthetic bone substitute. A novel instrument was developed to measure the bending deflection of screws under radial loads (225 N, 445 N, and 670 N) applied by a surrogate surgical plate at the head of the screw. Of the four cases considered, the analytical model utilizing an elastic foundation most accurately predicted deflection at the screw head, with an average difference of 19% between the measured and predicted results. Determination of the bending moments from the elastic foundation model revealed that a maximum moment of 2.3 N m occurred near the middle of the cortical wall closest to the plate. The location of the maximum bending moment along the screw axis was consistent with the fracture location commonly observed in clinical practice.

Failure mode and bending moment of canine pancarpal arthrodesis constructs stabilized with two different implant systems.

PubMed

Wininger, Fred A; Kapatkin, Amy S; Radin, Alex; Shofer, Frances S; Smith, Gail K

2007-12-01

To compare failure mode and bending moment of a canine pancarpal arthrodesis construct using either a 2.7 mm/3.5 mm hybrid dynamic compression plate (HDCP) or a 3.5 mm dynamic compression plate (DCP). Paired in vitro biomechanical testing of canine pancarpal arthrodesis constructs stabilized with either a 2.7/3.5 HDCP or 3.5 DCP. Paired cadaveric canine antebrachii (n=5). Pancarpal arthrodesis constructs were loaded to failure (point of maximum load) in 4-point bending using a materials-testing machine. Using this point of failure, bending moments were calculated from system variables for each construct and the 2 plating systems compared using a paired t-test. To examine the relationship between metacarpal diameter and screw diameter failure loads, linear regression was used and Pearson' correlation coefficient was calculated. Significance was set at P<.05. HDCP failed at higher loads than DCP for 9 of 10 constructs. The absolute difference in failure rates between the 2 plates was 0.552+/-0.182 N m, P=.0144 (95% confidence interval: -0.58 to 1.68). This is an 8.1% mean difference in bending strength. There was a significant linear correlation r=0.74 (P-slope=.014) and 0.8 (P-slope=.006) between metacarpal diameter and failure loads for the HDCP and 3.5 DCP, respectively. There was a small but significant difference between bending moment at failure between 2.7/3.5 HDCP and 3.5 DCP constructs; however, the difference may not be clinically evident in all patients. The 2.7/3.5 HDCP has physical and mechanical properties making it a more desirable plate for pancarpal arthrodesis.

Static bending deflection and free vibration analysis of moderate thick symmetric laminated plates using multidimensional wave digital filters

NASA Astrophysics Data System (ADS)

Tseng, Chien-Hsun

2018-06-01

This paper aims to develop a multidimensional wave digital filtering network for predicting static and dynamic behaviors of composite laminate based on the FSDT. The resultant network is, thus, an integrated platform that can perform not only the free vibration but also the bending deflection of moderate thick symmetric laminated plates with low plate side-to-thickness ratios (< = 20). Safeguarded by the Courant-Friedrichs-Levy stability condition with the least restriction in terms of optimization technique, the present method offers numerically high accuracy, stability and efficiency to proceed a wide range of modulus ratios for the FSDT laminated plates. Instead of using a constant shear correction factor (SCF) with a limited numerical accuracy for the bending deflection, an optimum SCF is particularly sought by looking for a minimum ratio of change in the transverse shear energy. This way, it can predict as good results in terms of accuracy for certain cases of bending deflection. Extensive simulation results carried out for the prediction of maximum bending deflection have demonstratively proven that the present method outperforms those based on the higher-order shear deformation and layerwise plate theories. To the best of our knowledge, this is the first work that shows an optimal selection of SCF can significantly increase the accuracy of FSDT-based laminates especially compared to the higher order theory disclaiming any correction. The highest accuracy of overall solution is compared to the 3D elasticity equilibrium one.

Biomechanical study of prophylactic internal fixation of the radial osteocutaneous donor site using the sheep tibia model.

PubMed

Avery, C M E; Best, A; Patterson, P; Rolton, J; Ponter, A R S

2007-09-01

This study investigated the strengthening effect of different types of plate and position after osteotomy of the sheep tibia, which is a model for the radial osteocutaneous donor site. Fifty matched pairs of adult sheep tibias were tested in torsion and four-point bending. Firstly, the weakening effect of an osteotomy was compared with the intact bone. Then pairs of bones with an osteotomy were compared with and without reinforcement with different types of 3.5mm plate. The plate was placed in either the anterior (over the defect) or posterior (on the intact cortex) position. In torsion the mean strength of the intact bone was 45% greater than after osteotomy (P=0.02). The reinforced bone was on average 61% stronger than the unreinforced bone (P<0.001). In bending the mean strength of the intact bone was 188% greater than after osteotomy (P=0.02). The reinforced bone was on average 184% stronger then the unreinforced bone (P<0.001). The tibia was able to withstand much greater loads in bending. The dynamic compression plate was the strongest reinforcement in both torsion and bending. The position of the plate did not alter the strengthening effect in torsion but the posterior position resisted greater bending loads (P=0.01). This may not be relevant in clinical practice as the radius is likely to fracture first as a result of lower torsional forces.

Research on Characteristics of New Energy Dissipation With Symmetrical Structure

NASA Astrophysics Data System (ADS)

Ming, Wen; Huang, Chun-mei; Huang, Hao-wen; Wang, Xin-fang

2018-03-01

Utilizing good energy consumption capacity of arc steel bar, a new energy dissipation with symmetrical structure was proposed in this article. On the base of collection experimental data of damper specimen Under low cyclic reversed loading, finite element models were built by using ANSYS software, and influences of parameter change (Conduction rod diameter, Actuation plate thickness, Diameter of arc steel rod, Curved bars initial bending) on energy dissipation performance were analyzed. Some useful conclusions which can lay foundations for practical application were drawn.

Standing wave acoustic levitation on an annular plate

NASA Astrophysics Data System (ADS)

Kandemir, Mehmet Hakan; Çalışkan, Mehmet

2016-11-01

In standing wave acoustic levitation technique, a standing wave is formed between a source and a reflector. Particles can be attracted towards pressure nodes in standing waves owing to a spring action through which particles can be suspended in air. This operation can be performed on continuous structures as well as in several numbers of axes. In this study an annular acoustic levitation arrangement is introduced. Design features of the arrangement are discussed in detail. Bending modes of the annular plate, known as the most efficient sound generation mechanism in such structures, are focused on. Several types of bending modes of the plate are simulated and evaluated by computer simulations. Waveguides are designed to amplify waves coming from sources of excitation, that are, transducers. With the right positioning of the reflector plate, standing waves are formed in the space between the annular vibrating plate and the reflector plate. Radiation forces are also predicted. It is demonstrated that small particles can be suspended in air at pressure nodes of the standing wave corresponding to a particular bending mode.

On the role of tip curvature on flapping plates.

PubMed

Martin, Nathan; Gharib, Morteza

2018-01-09

During the flapping motion of a fish's tail, the caudal fin exhibits antero-posterior bending and dorso-ventral bending, the latter of which is referred to as chord-wise bending herein. The impact of chord-wise tip curvature on the hydrodynamic forces for flapping plates is investigated to explore potential mechanisms to improve the maneuverability or the performance of autonomous underwater vehicles. First, actuated chord-wise tip curvature is explored. Comparison of rigid curved geometries to a rigid flat plate as a baseline suggests that an increased curvature decreases the generated forces. An actuated plate with a dynamic tip curvature is created to illustrate a modulation of this decrease in forces. Second, the impact of curvature is isolated using curved plates with an identical planform area. Comparison of rigid curved geometries as a baseline corroborates the result that an increased curvature decreases the generated forces, with the exception that presenting a concave geometry into the flow increases the thrust and the efficiency. A passively-actuated plate is designed to capitalize on this effect by presenting a concave geometry into the flow throughout the cycle. The dynamically and passively actuated plates show potential to improve the maneuverability and the efficiency of autonomous underwater vehicles, respectively.

Development of robust flexible OLED encapsulations using simulated estimations and experimental validations

NASA Astrophysics Data System (ADS)

Lee, Chang-Chun; Shih, Yan-Shin; Wu, Chih-Sheng; Tsai, Chia-Hao; Yeh, Shu-Tang; Peng, Yi-Hao; Chen, Kuang-Jung

2012-07-01

This work analyses the overall stress/strain characteristic of flexible encapsulations with organic light-emitting diode (OLED) devices. A robust methodology composed of a mechanical model of multi-thin film under bending loads and related stress simulations based on nonlinear finite element analysis (FEA) is proposed, and validated to be more reliable compared with related experimental data. With various geometrical combinations of cover plate, stacked thin films and plastic substrate, the position of the neutral axis (NA) plate, which is regarded as a key design parameter to minimize stress impact for the concerned OLED devices, is acquired using the present methodology. The results point out that both the thickness and mechanical properties of the cover plate help in determining the NA location. In addition, several concave and convex radii are applied to examine the reliable mechanical tolerance and to provide an insight into the estimated reliability of foldable OLED encapsulations.

Deformation of island-arc lithosphere due to steady plate subduction

NASA Astrophysics Data System (ADS)

Fukahata, Yukitoshi; Matsu'ura, Mitsuhiro

2016-02-01

Steady plate subduction elastically brings about permanent lithospheric deformation in island arcs, though this effect has been neglected in most studies based on elastic dislocation theory. We investigate the characteristics of the permanent lithospheric deformation using a kinematic model, in which steady slip motion is given along a plate interface in the elastic lithosphere overlying the viscoelastic asthenosphere under gravity. As a rule of thumb, long-term lithospheric deformation can be understood as a bending of an elastic plate floating on non-viscous fluid, because the asthenosphere behaves like water on the long term. The steady slip below the lithosphere-asthenosphere boundary does not contribute to long-term lithospheric deformation. Hence, the key parameters that control the lithospheric deformation are only the thickness of the lithosphere and the geometry of the plate interface. Slip on a plate interface generally causes substantial vertical displacement, and gravity always tries to retrieve the original gravitational equilibrium. For a curved plate interface gravity causes convex upward bending of the island-arc lithosphere, while for a planar plate interface gravity causes convex downward bending. Larger curvature and thicker lithosphere generally results in larger deformation. When the curvature changes along the plate interface, internal deformation is also involved intrinsically, which modifies the deformation field due to gravity. Because the plate interface generally has some curvature, at least near the trench, convex upward bending of the island-arc lithosphere, which involves uplift of island-arc and subsidence around the trench, is always realized. On the other hand, the deformation field of the island-arc lithosphere sensitively depends on lithospheric thickness and plate interface geometry. These characteristics obtained by the numerical simulation are consistent with observed topography and free-air gravity anomalies in subduction zones: a pair of topography and gravity anomalies, high in the arc and low around the trench, is observed without exceptions all over the world, while there are large variety in the amplitude and horizontal scale of the topography and gravity anomalies.

An Older, Slower Hawaii-Emperor Bend

NASA Astrophysics Data System (ADS)

Sharp, W. D.; Clague, D. A.

2002-12-01

The Hawaii-Emperor Bend is widely interpreted to indicate a profound change in the direction of Pacific Plate motion at about 43 Ma. This interpretation rests on the assumption that the Hawaiian hotspot has remained fixed; however, the fixity of the Hawaiian hotspot has long been challenged on the basis of plate-circuit reconstructions and considerations of mantle dynamics. Moreover, paleomagnetists (e.g., Tarduno and Cottrell, 1997) have suggested that prior to formation of the Bend the Hawaiian hotspot moved southward relative to Earth's spin axis at cm-per-year rates--that is, the Bend may primarily record slowing of the hotspot's own motion. If so, the rate of volcanic migration along the chain--which must be the vector sum of hotspot and Pacific Plate motions--should slow at the Bend. Published interpretations of Hawaii-Emperor seamount ages portray a uniform volcanic migration rate of about 8 cm per year through the Bend; however, many of the ages underlying these interpretations are whole-rock K-Ar and Ar-Ar total fusion ages of uncertain reliability. We report 15 new Ar-Ar plateau ages of milligram quantities of selected feldspars and hornblendes from 6 seamounts that bracket the Bend, extending from 1350 km north of the Bend to 225 km east of the Bend. The dated rocks are post-shield, transitional to alkalic basalts and trachytes that--by analogy with Quaternary Hawaiian volcanoes--erupted between 1 and 2 m.y. after passage of the seamount over the leading edge of the hotspot. Accordingly, north of the Bend, from Suiko seamount (age = 61.3 +/-0.5 Ma, 2σ ) to Koko seamount (50.6 +/-0.2 Ma), volcanism apparently migrated at about 10 cm per year during formation of the southern Emperor Chain. Through the Bend, from Koko seamount via Kimmei (47.3 +/-0.4 Ma), Diakakuji (46.7 +/-0.2 Ma), Abbott (41.5 +/-0.3 Ma) and Colahan (38.8 +/-0.2 Ma) seamounts, migration of volcanism slowed to 5.2 +/-0.6 cm per year--qualitatively consistent with hotspot motion that slowed or stopped near the Bend. Slower migration of volcanism around the Bend accentuates a precipitous drop in eruption rate that accompanied the Bend's inception. Furthermore, the new, older age of Koko seamount indicates that the Bend began to form at about 50 Ma. Therefore, inception of the Bend coincided with--and may have been causally linked to--reorganization of northern Pacific spreading ridges between marine magnetic anomalies 22 and 24, corresponding to 49-53 Ma on the Cande and Kent (1995) geomagnetic polarity time scale. Thus a change in direction of Pacific Plate motion may yet prove to have played a role in forming the Bend, though earlier than previously believed.

Dynamic responses of graphite/epoxy laminated beam to impact of elastic spheres

NASA Technical Reports Server (NTRS)

Sun, C. T.; Wang, T.

1982-01-01

Wave propagation in 90/45/90/-45/902s and 0/45/0/-45/02s laminates of a graphite/epoxy composite due to impact of a steel ball was investigated experimentally and also by using a high order beam finite element. Dynamic strain responses at several locations were obtained using strain gages. The finite element program which incorporated statically determined contact laws was employed to calculate the contact force history as well as the target beam dynamic deformation. The comparison of the finite element solutions with the experimental data indicated that the static contact laws for loading and unloading (developed under this grant) are adequate for the dynamic impact analysis. It was found that for the 0/45/0/-45/02s laminate which has a much larger longitudinal bending rigidity, the use of beam finite elements is not suitable and plate finite element should be used instead.

Finite element stress, vibration, and buckling analysis of laminated beams with the use of refined elements

NASA Astrophysics Data System (ADS)

Borovkov, Alexei I.; Avdeev, Ilya V.; Artemyev, A.

1999-05-01

In present work, the stress, vibration and buckling finite element analysis of laminated beams is performed. Review of the equivalent single-layer (ESL) laminate theories is done. Finite element algorithms and procedures integrated into the original FEA program system and based on the classical laminated plate theory (CLPT), first-order shear deformation theory (FSDT), third-order theory of Reddy (TSDT-R) and third- order theory of Kant (TSDT-K) with the use of the Lanczos method for solving of the eigenproblem are developed. Several numerical tests and examples of bending, free vibration and buckling of multilayered and sandwich beams with various material, geometry properties and boundary conditions are solved. New effective higher-order hierarchical element for the accurate calculation of transverse shear stress is proposed. The comparative analysis of results obtained by the considered models and solutions of 2D problems of the heterogeneous anisotropic elasticity is fulfilled.

A unified theory for laminated plates

NASA Astrophysics Data System (ADS)

Guiamatsia Tafeuvoukeng, Irene

A literature survey on plate and beam theories show how the advent of the finite element method and the variational method circa 1940 have been a great stimulant for the research in this field. The initial thin plate formulation has been incrementally expanded to treat the isotropic thick plate, the anisotropic single layer, and then laminated plates. It appears however that current formulations still fall into one of two categories: (1) The formulation is tailored for a specific laminate and/or loading case; (2) or the formulation is too complicated to be of practical relevance. In this work a new unifying approach to laminated plate formulation is presented. All laminated plates, including sandwich panels, subjected to any surface load and with any boundary conditions are treated within a single model. In addition, the fundamental behavior of the plate as a two-dimensional structural element is explained. The novel idea is the introduction of fundamental state solutions, which are analytical far field stress and strain solutions of the laminated plate subjected to a set of hierarchical primary loads, the fundamental loads. These loads are carefully selected to form a basis of the load space, and corresponding solutions are superposed to obtain extremely accurate predictions of the three dimensional solution. six,y,z =aklx,y sikl z where i = 1,..., 6; 1=1,...,l max is a substate of the kth fundamental state k=1,2,3,... Typically, a fundamental state solution is expressed as a through-thickness function (z), while the amplitudes of each fundamental load are found from two dimensional finite element solution as a function of in-plane coordinates (x,y). Three major contributions are produced in this work: (1) A complete calibration of the plate as a two-dimensional structure is performed with pure bending and constant shear fundamental states. (2) There are four independent ways to apply a constant shear resultant on a plate, as opposed to one for a beam. This makes it impossible to define a unique 2 x 2 transverse shear stiffness matrix. Therefore the traditional problem of the shear correction factor loses all relevance. It is however shown that an explicit transverse constitutive relation can be obtained for isotropic-layered laminates or single-layers. (3) Higher accuracy, three-dimensional solutions are obtained using a two-dimensional finite element model with a complexity level (degrees of freedom) similar to the Reissner-Mindlin plate. The proof of concept is realized using Pagano solution for rectangular plates under sinusoidal load, for a sandwich panel. Additional comparisons are also performed for four and six-layer symmetric and antisymmetric laminates, between the new plate theory results and full three-dimensional finite element solutions.

On the relative significance of lithospheric weakening mechanisms for sustained plate tectonics

NASA Astrophysics Data System (ADS)

Araceli Sanchez-Maes, Sophia

2018-01-01

Plate tectonics requires the bending of strong plates at subduction zones, which is difficult to achieve without a secondary weakening mechanism. Two classes of weakening mechanisms have been proposed for the generation of ongoing plate tectonics, distinguished by whether or not they require water. Here we show that the energy budget of global subduction zones offers a simple yet decisive test on their relative significance. Theoretical studies of mantle convection suggest bending dissipation to occupy only 10-20 % of total dissipation in the mantle, and our results indicate that the hydrous mechanism in the shallow part of plates is essential to satisfy the requirement. Thus, surface oceans are required for the long-term operation of plate tectonics on terrestrial worlds. Establishing this necessary and observable condition for sustained plate tectonics carries important implications for planetary habitability at large.

Lattice Truss Structural Response Using Energy Methods

NASA Technical Reports Server (NTRS)

Kenner, Winfred Scottson

1996-01-01

A deterministic methodology is presented for developing closed-form deflection equations for two-dimensional and three-dimensional lattice structures. Four types of lattice structures are studied: beams, plates, shells and soft lattices. Castigliano's second theorem, which entails the total strain energy of a structure, is utilized to generate highly accurate results. Derived deflection equations provide new insight into the bending and shear behavior of the four types of lattices, in contrast to classic solutions of similar structures. Lattice derivations utilizing kinetic energy are also presented, and used to examine the free vibration response of simple lattice structures. Derivations utilizing finite element theory for unique lattice behavior are also presented and validated using the finite element analysis code EAL.

Shape sensing methods: Review and experimental comparison on a wing-shaped plate

NASA Astrophysics Data System (ADS)

Gherlone, Marco; Cerracchio, Priscilla; Mattone, Massimiliano

2018-05-01

Shape sensing, i.e., the reconstruction of the displacement field of a structure from some discrete surface strain measurements, is a fundamental capability for the structural health management of critical components. In this paper, a review of the shape sensing methodologies available in the open literature and of the different applications is provided. Then, for the first time, an experimental comparative study is presented among the main approaches in order to highlight their relative merits in presence of uncertainties affecting real applications. These approaches are, namely, the inverse Finite Element Method, the Modal Method and Ko's Displacement Theory. A brief description of these methods is followed by the presentation of the experimental test results. A cantilevered, wing-shaped aluminum plate is let deform under its own weight, leading to bending and twisting. Using the experimental strain measurements as input data, the deflection field of the plate is reconstructed using the three aforementioned approaches and compared with the actual measured deflection. The inverse Finite Element Method is proven to be slightly more accurate and particularly attractive because it is versatile with respect to the boundary conditions and it does not require any information about material properties and loading conditions.

A comparison of parallel and diverging screw angles in the stability of locked plate constructs.

PubMed

Wähnert, D; Windolf, M; Brianza, S; Rothstock, S; Radtke, R; Brighenti, V; Schwieger, K

2011-09-01

We investigated the static and cyclical strength of parallel and angulated locking plate screws using rigid polyurethane foam (0.32 g/cm(3)) and bovine cancellous bone blocks. Custom-made stainless steel plates with two conically threaded screw holes with different angulations (parallel, 10° and 20° divergent) and 5 mm self-tapping locking screws underwent pull-out and cyclical pull and bending tests. The bovine cancellous blocks were only subjected to static pull-out testing. We also performed finite element analysis for the static pull-out test of the parallel and 20° configurations. In both the foam model and the bovine cancellous bone we found the significantly highest pull-out force for the parallel constructs. In the finite element analysis there was a 47% more damage in the 20° divergent constructs than in the parallel configuration. Under cyclical loading, the mean number of cycles to failure was significantly higher for the parallel group, followed by the 10° and 20° divergent configurations. In our laboratory setting we clearly showed the biomechanical disadvantage of a diverging locking screw angle under static and cyclical loading.

APPLE - An aeroelastic analysis system for turbomachines and propfans

NASA Technical Reports Server (NTRS)

Reddy, T. S. R.; Bakhle, Milind A.; Srivastava, R.; Mehmed, Oral

1992-01-01

This paper reviews aeroelastic analysis methods for propulsion elements (advanced propellers, compressors and turbines) being developed and used at NASA Lewis Research Center. These aeroelastic models include both structural and aerodynamic components. The structural models include the typical section model, the beam model with and without disk flexibility, and the finite element blade model with plate bending elements. The aerodynamic models are based on the solution of equations ranging from the two-dimensional linear potential equation for a cascade to the three-dimensional Euler equations for multi-blade configurations. Typical results are presented for each aeroelastic model. Suggestions for further research are indicated. All the available aeroelastic models and analysis methods are being incorporated into a unified computer program named APPLE (Aeroelasticity Program for Propulsion at LEwis).

Finite element analysis and genetic algorithm optimization design for the actuator placement on a large adaptive structure

NASA Astrophysics Data System (ADS)

Sheng, Lizeng

The dissertation focuses on one of the major research needs in the area of adaptive/intelligent/smart structures, the development and application of finite element analysis and genetic algorithms for optimal design of large-scale adaptive structures. We first review some basic concepts in finite element method and genetic algorithms, along with the research on smart structures. Then we propose a solution methodology for solving a critical problem in the design of a next generation of large-scale adaptive structures---optimal placements of a large number of actuators to control thermal deformations. After briefly reviewing the three most frequently used general approaches to derive a finite element formulation, the dissertation presents techniques associated with general shell finite element analysis using flat triangular laminated composite elements. The element used here has three nodes and eighteen degrees of freedom and is obtained by combining a triangular membrane element and a triangular plate bending element. The element includes the coupling effect between membrane deformation and bending deformation. The membrane element is derived from the linear strain triangular element using Cook's transformation. The discrete Kirchhoff triangular (DKT) element is used as the plate bending element. For completeness, a complete derivation of the DKT is presented. Geometrically nonlinear finite element formulation is derived for the analysis of adaptive structures under the combined thermal and electrical loads. Next, we solve the optimization problems of placing a large number of piezoelectric actuators to control thermal distortions in a large mirror in the presence of four different thermal loads. We then extend this to a multi-objective optimization problem of determining only one set of piezoelectric actuator locations that can be used to control the deformation in the same mirror under the action of any one of the four thermal loads. A series of genetic algorithms, GA Version 1, 2 and 3, were developed to find the optimal locations of piezoelectric actuators from the order of 1021 ˜ 1056 candidate placements. Introducing a variable population approach, we improve the flexibility of selection operation in genetic algorithms. Incorporating mutation and hill climbing into micro-genetic algorithms, we are able to develop a more efficient genetic algorithm. Through extensive numerical experiments, we find that the design search space for the optimal placements of a large number of actuators is highly multi-modal and that the most distinct nature of genetic algorithms is their robustness. They give results that are random but with only a slight variability. The genetic algorithms can be used to get adequate solution using a limited number of evaluations. To get the highest quality solution, multiple runs including different random seed generators are necessary. The investigation time can be significantly reduced using a very coarse grain parallel computing. Overall, the methodology of using finite element analysis and genetic algorithm optimization provides a robust solution approach for the challenging problem of optimal placements of a large number of actuators in the design of next generation of adaptive structures.

On the role of CFRP reinforcement for wood beams stiffness

NASA Astrophysics Data System (ADS)

Ianasi, A. C.

2015-11-01

In recent years, carbon fiber composites have been increasingly used in different ways in reinforcing structural elements. Specifically, the use of composite materials as a reinforcement for wood beams under bending loads requires paying attention to several aspects of the problem such as the number of the composite layers applied on the wood beams. Study consolidation of composites revealed that they are made by bonding fibrous material impregnated with resin on the surface of various elements, to restore or increase the load carrying capacity (bending, cutting, compression or torque) without significant damage of their rigidity. Fibers used in building applications can be fiberglass, aramid or carbon. Items that can be strengthened are concrete, brick, wood, steel and stone, and in terms of structural beams, walls, columns and floors. This paper describes an experimental study which was designed to evaluate the effect of composite material on the stiffness of the wood beams. It proposes a summary of the fundamental principles of analysis of composite materials and the design and use. The type of reinforcement used on the beams is the carbon fiber reinforced polymer (CFRP) sheet and plates and also an epoxy resin for bonding all the elements. Structural epoxy resins remain the primary choice of adhesive to form the bond to fiber-reinforced plastics and are the generally accepted adhesives in bonded CFRP-wood connections. The advantages of using epoxy resin in comparison to common wood-laminating adhesives are their gap-filling qualities and the low clamping pressures that are required to form the bond between carbon fiber plates or sheets and the wood beams. Mechanical tests performed on the reinforced wood beams showed that CFRP materials may produce flexural displacement and lifting increases of the beams. Observations of the experimental load-displacement relationships showed that bending strength increased for wood beams reinforced with CFRP composite plates and sheets compared to those without CFRP reinforcement. The main conclusion of the tests is that the tensioning forces allow beam taking a maximum load for a while, something that is particularly useful when we consider a real construction, so in case of excess lift beam, we have time to take strengthening measures and when is about a catastrophic request (earthquake) the construction remain partially functional. The experiments have shown that the method of increasing resistance of wood constructions with composite materials is good for it. The solution is easy to implement and has low costs.

Modified equations of finite-size layered plates made of orthotropic material. Comparison of the results of numerical calculations with analytical solutions

NASA Astrophysics Data System (ADS)

Volchkov, Yu. M.

2017-09-01

This paper describes the modified bending equations of layered orthotropic plates in the first approximation. The approximation of the solution of the equation of the three-dimensional theory of elasticity by the Legendre polynomial segments is used to obtain differential equations of the elastic layer. For the approximation of equilibrium equations and boundary conditions of three-dimensional theory of elasticity, several approximations of each desired function (stresses and displacements) are used. The stresses at the internal points of the plate are determined from the defining equations for the orthotropic material, averaged with respect to the plate thickness. The construction of the bending equations of layered plates for each layer is carried out with the help of the elastic layer equations and the conjugation conditions on the boundaries between layers, which are conditions for the continuity of normal stresses and displacements. The numerical solution of the problem of bending of the rectangular layered plate obtained with the help of modified equations is compared with an analytical solution. It is determined that the maximum error in determining the stresses does not exceed 3 %.

The adjustment of mantle plumes to changes in plate motion

NASA Astrophysics Data System (ADS)

Griffiths, Ross W.; Richards, Mark A.

1989-05-01

The relative motion of hotspots and lithospheric plates implies a velocity shear in the underlying mantle, causing horizontal advection of mantle plumes as they rise toward the lithosphere. Consequent tilting of plumes parallel to the direction of plate motion indicates that plumes must undergo a period of readjustment after the velocity vector for plate motion is altered. Thus the shape of bends in the surface tracks of hotspots, resulting from changes in plate motion, will reflect the plume adjustment. Laboratory experiments, as well as computations using a simple theory developed in Richards & Griffiths [1988] for the dynamics of continuous plume conduits, demonstrate that the bend in the surface track has a radius of curvature approximately equal to the maximum horizontal deflection of the conduit. Thus the sharpness of the bend at an age of 43Ma in the Hawaiian-Emperor volcanic chain implies that the deflection of the underlying plume in that case was small (<200 km). This small deflection is expected for plumes carrying large buoyancy fluxes, and it indicates that tilting of the conduit is unlikely to be sufficient to cause diapiric instability.

Study of interface influence on bending performance of CFRP with embedded optical fibers

NASA Astrophysics Data System (ADS)

Liu, Rong-mei; Liang, Da-kai

2008-11-01

Studies showed that the bending strength of composite would be affected by embedded optical fibers. Interface strength between the embedded optical fiber and the matrix was studied in this paper. Based on the single fiber pull out tests, the interfacial shear strength between the coating and the clad is the weakest. The shear strength of the optical fiber used in this study is near to 0.8MPa. In order to study the interfacial effect on bending property of generic smart structure, a quasi-isotropic composite laminates were produced from Toray T300C/ epoxy prepreg. Optical fibers were embedded within different orientation plies of the plates, with the optical fibers embedded in the same direction. Accordingly, five different types of plates were produced. Impact tests were carried out on the 5 different plate types. It is shown that when the fiber was embedded at the upper layer, the bending strength drops mostly. The bending normal stress on material arrives at the maximum. So does the normal stress applied on the optical fiber at the surface. Therefore, destructions could originate at the interface between the coating and the clad foremost. The ultimate strength of the smart structure will be affected furthest.

Fabrication of a high-precision spherical micromirror by bending a silicon plate with a metal pad.

PubMed

Wu, Tong; Hane, Kazuhiro

2011-09-20

We demonstrate here the fabrication of a smooth mirror surface by bending a thin silicon plate. A spherical surface is achieved by the bending moment generated in the circumference of the micromirror. Both convex and concave spherical micromirrors are realized through the anodic bonding of silicon and Pyrex glass. Since the mirror surface is originated from the polished silicon surface and no additional etching is introduced for manufacturing, the surface roughness is thus limited to the polishing error. This novel approach opens possibilities for fabricating a smooth surface for micromirror and microlens applications.

Intra- and intertrench variations in flexural bending of the Manila, Mariana and global trenches: implications on plate weakening in controlling trench dynamics

NASA Astrophysics Data System (ADS)

Zhang, Fan; Lin, Jian; Zhou, Zhiyuan; Yang, Hongfeng; Zhan, Wenhuan

2018-02-01

We conducted detailed analyses of a global array of trenches, revealing systematic intra- and intertrench variations in plate bending characteristics. The intratrench variations of the Manila and Mariana Trenches were analysed in detail as end-member cases of the relatively young (16-36 Ma) and old (140-160 Ma) subducting plates, respectively. Meanwhile, the intertrench variability was investigated for a global array of additional trenches including the Philippine, Kuril, Japan, Izu-Bonin, Aleutian, Tonga-Kermadec, Middle America, Peru, Chile, Sumatra and Java Trenches. Results of the analysis show that the trench relief (W0) and width (X0) of all systems are controlled primarily by the faulting-reduced elastic thickness near the trench axis (Tem) and affected only slightly by the initial unfaulted thickness (TeM) of the incoming plate. The reduction in Te has caused significant deepening and narrowing of trench valleys. For the cases of relatively young or old plates, the plate age could be a dominant factor in controlling the trench bending shape, regardless the variations in axial loadings. Our calculations also show that the axial loading and stresses of old subducting plates can vary significantly along the trench axis. In contrast, the young subducting plates show much smaller values and variations in axial loading and stresses.

The Hawaii-Emperor Bend: Clearly a Record of Pacific Plate Motion Change

NASA Astrophysics Data System (ADS)

Wessel, P.; Harada, Y.; Kroenke, L. W.; Sterling, A.

2003-12-01

As most introductory textbooks will point out, the conventional explanation for the ˜120° change in the trends of the Hawaiian and Emperor chains is a ˜60° change in plate motion over a fixed plume in the mantle. Recently, however, new paleomagnetic and radiometric age data from the Emperor Seamounts have led some scientists to reject the conventional view of the origin of the Hawaii-Emperor bend in favor of a mobile plume. Yet, at the brink of being explained away as the mere consequence of a drifting plume, the fixed hotspot hypothesis now gains support from newly reported radiometric dates of rock samples from seamounts at the bend which reveal an age much older than expected. Unlike the previous younger age ( ˜43 Ma), the older age ( ˜47 Ma) allows the bend to be directly correlated with a period of pronounced, global tectonic reorganizations around Chron 21. Here we present a new Pacific absolute plate motion model, derived from 15 hotspot chains, which does not require hotspot drift in order to satisfy geometric and chronological constraints. By considering this absolute plate motion model with available Pacific paleomagnetic poles we find support for the notion that the spin axis was closer to the Hawaiian hotspot during the formation of the Emperor chain, and this interpretation (polar wander, not hotspot drift) also explains the paleomagnetic latitudes from the Emperor seamounts as well as the lack of coral reefs materials in the drill holes north of Koko Guyot. However, this interpretation is not unique, and drift cannot be summarily ruled out. Yet, if Pacific plumes are drifting then they appear to be moving in unison. Careful examination of the Pacific seafloor reveals additional Pacific trails with bends that appear to be contemporaneous with the Hawaii-Emperor Bend, although conclusive radiometric age data are lacking. Our plate motion model predicts hotspot tracks that fit these bends. Considering all these lines of evidence the fixed hotspot hypothesis is granted a new lease on life.

Constraints from Seamounts on Pacific Plate or Plume Motion Prior to 80 Ma.

NASA Astrophysics Data System (ADS)

Konter, J. G.; Koppers, A. A. P.; Jackson, M. G.; Finlayson, V.; Konrad, K.

2015-12-01

The Hawaii-Emperor and Louisville hotspot tracks have long dominated the data set constraining absolute plate motion models. However, prior to ~80 Ma, multiple shorter, discontinuous hotspot trails and oceanic plateaus have been used to constrain absolute plate motion. Based on this earlier work, a clear Hawaii-Emperor style bend seems apparent around 100 Ma in the West Pacific Seamount Province (WPSP). More importantly, the ongoing debate on a plate versus plume motion origin for the Hawaii-Emperor Bend is applicable here, as the ~100 Ma bend may correspond to a global plate reorganization (Matthews et al., EPSL, 2012). Data for a comparison of bends comes from three groups with similar geographic patterns: 1) Mid-Pacific Mountains, Line Islands; 2) Shatsky Rise, Hess Rise, Musician and Wentworth Seamounts; and 3) Wake Seamounts, Marshall Islands, Magellan Seamounts. Both groups 1 and 2 feature a large igneous province (LIP) at their oldest end: Shatsky Rise and the Mid-Pacific Mountains. According to plate reconstructions these LIPs were constructed near all-ridge triple junctions, thus potential plume-ridge interactions need to be clarified before these LIPs can be used to define an absolute mantle reference frame. In contrast, the volcanoes of the third group (Wake, Marshall, Magellan) did erupt truly intra-plate and we therefore argue that this group provides a constraint on plate motion beyond 80 Ma that is independent of plume-ridge interactions. Since the volcanoes in this group are part of the WPSP, which is densely populated with seamounts, a combination of 40Ar/39Ar ages and Sr-Nd-Pb-Hf isotopes is needed to distinguish different hotspot tracks in this region. Backtracking each volcano through its age to its original eruptive location and using compositional color-coding, reveals groupings and patterns that vary by plate motion model, while the temporal patterns of backtracked locations inform us about potential plume motions.

Is a 50 Ma Event Recorded in the Absolute Plate Motion of Africa?

NASA Astrophysics Data System (ADS)

Maher, S. M.; Wessel, P.; Müller, R.; Harada, Y.

2012-12-01

There is considerable evidence for a global plate tectonic reorganization at ~Chron 21, as suggested by observed changes in global relative plate motion (RPM). The timings of these events appear to coincide with the age of the Hawaiian Emperor Bend (HEB), i.e., ~47-50 Ma. This 120° bend has traditionally been the poster child for the fixed hotspot hypothesis, suggesting the Pacific plate underwent a change in absolute plate motion (APM) as it moved over a more or less stationary Hawaiian hotspot. However, palaeomagnetic evidence favors southward motion of the Hawaii hotspot during the Emperor stage, limiting the amount of APM change required. In the Indo-Atlantic realm, RPMs involving Africa all seem compatible with a change in Africa APM around ~50 Ma. If this global plate reorganization took place there should also be physical evidence on the Africa plate itself due to the change in Africa APM. A candidate for such evidence may be the Réunion-Mascarene bend, which exhibits many HEB-like features. However, the Réunion hotspot also created the Chagos-Laccadive ridge as it encountered (and later crossed) the Carlsberg Ridge, and the oldest Mascarene section closest to the Seychelles may be continental in origin; thus there is some uncertainty in how to interpret the geometry. Furthermore, published APM models have had difficulty modeling this abrupt change in orientation. To reexamine this problem we derived a new Africa APM model that goes back to ~65 Ma using the Hybrid Polygonal Finite Rotation Method. The modeling incorporates the geometry and ages of seamount chains on the Africa plate and their associated hotspots as suitable constraints on an Africa APM model. The present as well as earlier positions of hotspots can be adjusted to get the best fit for the model. We examine how models with or without a ~50 Ma bend satisfy the geometries and age progressions of hotspot chains on the Africa plate and how well the predictions match observed paleolatitudes.

Various methods of determining the natural frequencies and damping of composite cantilever plates. 1. Exact solution for the binomial model of deformation

NASA Astrophysics Data System (ADS)

Skel'chik, V. S.; Ryabov, V. M.

1996-11-01

On the basis of the classical theory of thin anisotropic laminated plates the article analyzes the free vibrations of rectangular cantilever plates made of fibrous composites. The application of Kantorovich's method for the binomial representation of the shape of the elastic surface of a plate yielded for two unknown functions a system of two connected differential equations and the corresponding boundary conditions at the place of constraint and at the free edge. The exact solution for the frequencies and forms of the free vibrations was found with the use of Laplace transformation with respect to the space variable. The magnitudes of several first dimensionless frequencies of the bending and torsional vibrations of the plate were calculated for a wide range of change of two dimensionless complexes, with the dimensions of the plate and the anisotropy of the elastic properties of the material taken into account. The article shows that with torsional vibrations the warping constraint at the fixed end explains the apparent dependence of the shear modulus of the composite on the length of the specimen that had been discovered earlier on in experiments with a torsional pendulum. It examines the interaction and transformation of the second bending mode and of the first torsional mode of the vibrations. It analyzes the asymptotics of the dimensionless frequencies when the length of the plate is increased, and it shows that taking into account the bending-torsion interaction in strongly anisotropic materials type unidirectional carbon reinforced plastic can reduce substantially the frequencies of the bending vibrations but has no effect (within the framework of the binomial model) on the frequencies of the torsional vibrations.

Vectorization and parallelization of the finite strip method for dynamic Mindlin plate problems

NASA Technical Reports Server (NTRS)

Chen, Hsin-Chu; He, Ai-Fang

1993-01-01

The finite strip method is a semi-analytical finite element process which allows for a discrete analysis of certain types of physical problems by discretizing the domain of the problem into finite strips. This method decomposes a single large problem into m smaller independent subproblems when m harmonic functions are employed, thus yielding natural parallelism at a very high level. In this paper we address vectorization and parallelization strategies for the dynamic analysis of simply-supported Mindlin plate bending problems and show how to prevent potential conflicts in memory access during the assemblage process. The vector and parallel implementations of this method and the performance results of a test problem under scalar, vector, and vector-concurrent execution modes on the Alliant FX/80 are also presented.

Biomechanical properties of an advanced new carbon/flax/epoxy composite material for bone plate applications.

PubMed

Bagheri, Zahra S; El Sawi, Ihab; Schemitsch, Emil H; Zdero, Rad; Bougherara, Habiba

2013-04-01

This work is part of an ongoing program to develop a new carbon fiber/flax/epoxy (CF/flax/epoxy) hybrid composite material for use as an orthopaedic long bone fracture plate, instead of a metal plate. The purpose of this study was to evaluate the mechanical properties of this new novel composite material. The composite material had a "sandwich structure", in which two thin sheets of CF/epoxy were attached to each outer surface of the flax/epoxy core, which resulted in a unique structure compared to other composite plates for bone plate applications. Mechanical properties were determined using tension, three-point bending, and Rockwell hardness tests. Also, scanning electron microscopy (SEM) was used to characterize the failure mechanism of specimens in tension and three-point bending tests. The results of mechanical tests revealed a considerably high ultimate strength in both tension (399.8MPa) and flexural loading (510.6MPa), with a higher elastic modulus in bending tests (57.4GPa) compared to tension tests (41.7GPa). The composite material experienced brittle catastrophic failure in both tension and bending tests. The SEM images, consistent with brittle failure, showed mostly fiber breakage and fiber pull-out at the fractured surfaces with perfect bonding at carbon fibers and flax plies. Compared to clinically-used orthopaedic metal plates, current CF/flax/epoxy results were closer to human cortical bone, making the material a potential candidate for use in long bone fracture fixation. Copyright © 2013 Elsevier Ltd. All rights reserved.

Biomechanical Study of the Fixation Strength of Anteromedial Plating for Humeral Shaft Fractures.

PubMed

Zheng, Yin-Feng; Zhou, Jun-Lin; Wang, Xiao-Hong; Shan, Lei; Liu, Yang

2016-08-05

Open reduction and internal fixation with plate and screws are the gold standard for the surgical treatment of humeral shaft fractures, this study was to compare the mechanical properties of anteromedial, anterolateral, and posterior plating for humeral shaft fractures. A distal third humeral shaft fracture model was constructed using fourth-generation sawbones (#3404, composite bone). A total of 24 sawbones with a distal third humeral shaft fracture was randomly divided into three Groups: A, B, and C (n = 8 in each group) for anteromedial, anterolateral, and posterior plating, respectively. All sawbones were subjected to horizontal torsional fatigue tests, horizontal torsional and axial compressive fatigue tests, four-point bending fatigue tests in anteroposterior (AP) and mediolateral (ML) directions and horizontal torsional destructive tests. In the horizontal torsional fatigue tests, the mean torsional angle amplitude in Groups A, B, and C were 6.12°, 6.53°, and 6.81°. In horizontal torsional and axial compressive fatigue tests, the mean torsional angle amplitude in Groups A, B, and C were 5.66°, 5.67°, and 6.36°. The mean plate displacement amplitude was 0.05 mm, 0.08 mm, and 0.10 mm. Group A was smaller than Group C (P < 0.05). In AP four-point bending fatigue tests, the mean plate displacement amplitude was 0.16 mm, 0.13 mm, and 0.20 mm. Group B was smaller than Group C (P < 0.05). In ML four-point bending fatigue tests, the mean plate displacement amplitude were 0.16 mm, 0.19 mm, and 0.17 mm. In horizontal torsional destructive tests, the mean torsional rigidity in Groups A, B, and C was 0.82, 0.75, and 0.76 N·m/deg. The yielding torsional angle was 24.50°, 25.70°, and 23.86°. The mean yielding torque was 18.46, 18.05, and 16.83 N·m, respectively. Anteromedial plating was superior to anterolateral or posterior plating in all mechanical tests except in AP four-point bending fatigue tests compared to the anterolateral plating group. We can suggest that anteromedial plating is a clinically safe and effective way for humeral shaft fractures.

Handbook of structural stability part VI : strength of stiffened curved plates and shells

NASA Technical Reports Server (NTRS)

Becker, Herbert

1958-01-01

A comprehensive review of failure of stiffened curved plates and shells is presented. Panel instability in stiffened curved plates and general instability of stiffened cylinders are discussed. The loadings considered for the plates are axial, shear, and the combination of the two. For the cylinders, bending, external pressure, torsion, transverse shear, and combinations of these loads are considered. When possible, test data and theory were correlated. General instability in stiffened cylinders was investigated. For bending and torsion loads, test data and theory were correlated. For external pressure several existing theories were compared. As a result of this investigation a unified theoretical approach to analysis of general instability in stiffened cylinders was developed. (author)

Formulas for the elastic constants of plates with integral waffle-like stiffening

NASA Technical Reports Server (NTRS)

Dow, Norris R; Libove, Charles; Hubka, Ralph E

1954-01-01

Formulas are derived for the fifteen elastic constants associated with bending, stretching, twisting, and shearing of plates with closely spaced integral ribbing in a variety of configurations and proportions. In the derivation the plates are considered, conceptually, as more uniform orthotropic plates somewhat on the order of plywood. The constants, which include the effectiveness of the ribs for resisting deformations other than bending and stretching in their longitudinal directions, are defined in terms of four coefficients, and theoretical and experimental methods for the evaluation of these coefficients are discussed. Four of the more important elastic constants are predicted by these formulas and are compared with test results. Good correlation is obtained. (author)

Stress Intensity Factors for Part-Through Surface Cracks in Hollow Cylinders

NASA Technical Reports Server (NTRS)

Mettu, Sambi R.; Raju, Ivatury S.; Forman, Royce G.

1992-01-01

Flaws resulting from improper welding and forging are usually modeled as cracks in flat plates, hollow cylinders or spheres. The stress intensity factor solutions for these crack cases are of great practical interest. This report describes some recent efforts at improving the stress intensity factor solutions for cracks in such geometries with emphasis on hollow cylinders. Specifically, two crack configurations for cylinders are documented. One is that of a surface crack in an axial plane and the other is a part-through thumb-nail crack in a circumferential plane. The case of a part-through surface crack in flat plates is used as a limiting case for very thin cylinders. A combination of the two cases for cylinders is used to derive a relation for the case of a surface crack in a sphere. Solutions were sought which cover the entire range of the geometrical parameters such as cylinder thickness, crack aspect ratio and crack depth. Both the internal and external position of the cracks are considered for cylinders and spheres. The finite element method was employed to obtain the basic solutions. Power-law form of loading was applied in the case of flat plates and axial cracks in cylinders and uniform tension and bending loads were applied in the case of circumferential (thumb-nail) cracks in cylinders. In the case of axial cracks, the results for tensile and bending loads were used as reference solutions in a weight function scheme so that the stress intensity factors could be computed for arbitrary stress gradients in the thickness direction. For circumferential cracks, since the crack front is not straight, the above technique could not be used. Hence for this case, only the tension and bending solutions are available at this time. The stress intensity factors from the finite element method were tabulated so that results for various geometric parameters such as crack depth-to-thickness ratio (a/t), crack aspect ratio (a/c) and internal radius-to-thickness ratio (R/t) or the crack length-to-width ratio (2c/W) could be obtained by interpolation and extrapolation. Such complete tables were then incorporated into the NASA/FLAGRO computer program which is widely used by the aerospace community for fracture mechanics analysis.

Indian and African plate motions driven by the push force of the Réunion plume head.

PubMed

Cande, Steven C; Stegman, Dave R

2011-07-06

Mantle plumes are thought to play an important part in the Earth's tectonics, yet it has been difficult to isolate the effect that plumes have on plate motions. Here we analyse the plate motions involved in two apparently disparate events--the unusually rapid motion of India between 67 and 52 million years ago and a contemporaneous, transitory slowing of Africa's motion--and show that the events are coupled, with the common element being the position of the Indian and African plates relative to the location of the Réunion plume head. The synchroneity of these events suggests that they were both driven by the force of the Réunion plume head. The recognition of this plume force has substantial tectonic implications: the speed-up and slowdown of India, the possible cessation of convergence between Africa and Eurasia in the Palaeocene epoch and the enigmatic bends of the fracture zones on the Southwest Indian Ridge can all be attributed to the Réunion plume. ©2011 Macmillan Publishers Limited. All rights reserved

Vibration characteristics of 1/8-scale dynamic models of the space-shuttle solid-rocket boosters

NASA Technical Reports Server (NTRS)

Leadbetter, S. A.; Stephens, W.; Sewall, J. L.; Majka, J. W.; Barret, J. R.

1976-01-01

Vibration tests and analyses of six 1/8 scale models of the space shuttle solid rocket boosters are reported. Natural vibration frequencies and mode shapes were obtained for these aluminum shell models having internal solid fuel configurations corresponding to launch, midburn (maximum dynamic pressure), and near endburn (burnout) flight conditions. Test results for longitudinal, torsional, bending, and shell vibration frequencies are compared with analytical predictions derived from thin shell theory and from finite element plate and beam theory. The lowest analytical longitudinal, torsional, bending, and shell vibration frequencies were within + or - 10 percent of experimental values. The effects of damping and asymmetric end skirts on natural vibration frequency were also considered. The analytical frequencies of an idealized full scale space shuttle solid rocket boosted structure are computed with and without internal pressure and are compared with the 1/8 scale model results.

Vibrational Analysis of Engine Components Using Neural-Net Processing and Electronic Holography

NASA Technical Reports Server (NTRS)

Decker, Arthur J.; Fite, E. Brian; Mehmed, Oral; Thorp, Scott A.

1997-01-01

The use of computational-model trained artificial neural networks to acquire damage specific information from electronic holograms is discussed. A neural network is trained to transform two time-average holograms into a pattern related to the bending-induced-strain distribution of the vibrating component. The bending distribution is very sensitive to component damage unlike the characteristic fringe pattern or the displacement amplitude distribution. The neural network processor is fast for real-time visualization of damage. The two-hologram limit makes the processor more robust to speckle pattern decorrelation. Undamaged and cracked cantilever plates serve as effective objects for testing the combination of electronic holography and neural-net processing. The requirements are discussed for using finite-element-model trained neural networks for field inspections of engine components. The paper specifically discusses neural-network fringe pattern analysis in the presence of the laser speckle effect and the performances of two limiting cases of the neural-net architecture.

Vibrational Analysis of Engine Components Using Neural-Net Processing and Electronic Holography

NASA Technical Reports Server (NTRS)

Decker, Arthur J.; Fite, E. Brian; Mehmed, Oral; Thorp, Scott A.

1998-01-01

The use of computational-model trained artificial neural networks to acquire damage specific information from electronic holograms is discussed. A neural network is trained to transform two time-average holograms into a pattern related to the bending-induced-strain distribution of the vibrating component. The bending distribution is very sensitive to component damage unlike the characteristic fringe pattern or the displacement amplitude distribution. The neural network processor is fast for real-time visualization of damage. The two-hologram limit makes the processor more robust to speckle pattern decorrelation. Undamaged and cracked cantilever plates serve as effective objects for testing the combination of electronic holography and neural-net processing. The requirements are discussed for using finite-element-model trained neural networks for field inspections of engine components. The paper specifically discusses neural-network fringe pattern analysis in the presence of the laser speckle effect and the performances of two limiting cases of the neural-net architecture.

The design and experiment of a novel ultrasonic motor based on the combination of bending modes.

PubMed

Yan, Jipeng; Liu, Yingxiang; Liu, Junkao; Xu, Dongmei; Chen, Weishan

2016-09-01

This paper presents a new-type linear ultrasonic motor which takes advantage of the combination of two orthogonal bending vibration modes. The proposed ultrasonic motor consists of eight pieces of PZT ceramic plates and a metal beam that includes two cone-shaped horns and a cylindrical driving foot. The finite element analyses were finished to verify the working principle of the proposed motor. The mode shapes of the motor were obtained by modal analysis; the elliptical trajectories of nodes on the driving foot were obtained by time-domain analysis. Based on the analyses, a prototype of the proposed motor was fabricated and measured. The mechanical output characteristics were obtained by experiments. The maximal velocity of the proposed motor is 735mm/s and the maximal thrust is 1.1N. Copyright © 2016 Elsevier B.V. All rights reserved.

Equivalent-Continuum Modeling With Application to Carbon Nanotubes

NASA Technical Reports Server (NTRS)

Odegard, Gregory M.; Gates, Thomas S.; Nicholson, Lee M.; Wise, Kristopher E.

2002-01-01

A method has been proposed for developing structure-property relationships of nano-structured materials. This method serves as a link between computational chemistry and solid mechanics by substituting discrete molecular structures with equivalent-continuum models. It has been shown that this substitution may be accomplished by equating the vibrational potential energy of a nano-structured material with the strain energy of representative truss and continuum models. As important examples with direct application to the development and characterization of single-walled carbon nanotubes and the design of nanotube-based devices, the modeling technique has been applied to determine the effective-continuum geometry and bending rigidity of a graphene sheet. A representative volume element of the chemical structure of graphene has been substituted with equivalent-truss and equivalent continuum models. As a result, an effective thickness of the continuum model has been determined. This effective thickness has been shown to be significantly larger than the interatomic spacing of graphite. The effective thickness has been shown to be significantly larger than the inter-planar spacing of graphite. The effective bending rigidity of the equivalent-continuum model of a graphene sheet was determined by equating the vibrational potential energy of the molecular model of a graphene sheet subjected to cylindrical bending with the strain energy of an equivalent continuum plate subjected to cylindrical bending.

A Review of Recent Aeroelastic Analysis Methods for Propulsion at NASA Lewis Research Center

NASA Technical Reports Server (NTRS)

Reddy, T. S. R.; Bakhle, Milind A.; Srivastava, R.; Mehmed, Oral; Stefko, George L.

1993-01-01

This report reviews aeroelastic analyses for propulsion components (propfans, compressors and turbines) being developed and used at NASA LeRC. These aeroelastic analyses include both structural and aerodynamic models. The structural models include a typical section, a beam (with and without disk flexibility), and a finite-element blade model (with plate bending elements). The aerodynamic models are based on the solution of equations ranging from the two-dimensional linear potential equation to the three-dimensional Euler equations for multibladed configurations. Typical calculated results are presented for each aeroelastic model. Suggestions for further research are made. Many of the currently available aeroelastic models and analysis methods are being incorporated in a unified computer program, APPLE (Aeroelasticity Program for Propulsion at LEwis).

Stress concentration investigations using NASTRAN

NASA Technical Reports Server (NTRS)

Gillcrist, M. C.; Parnell, L. A.

1986-01-01

Parametic investigations are performed using several two dimensional finite element formulations to determine their suitability for use in predicting extremum stresses in marine propellers. Comparisons are made of two NASTRAN elements (CTRIM6 and CTRAIA2) wherein elasticity properties have been modified to yield plane strain results. The accuracy of the elements is investigated by comparing finite element stress predictions with experimentally determined stresses in two classical cases: (1) tension in a flat plate with a circular hole; and (2) a filleted flat bar subjected to in-plane bending. The CTRIA2 element is found to provide good results. The displacement field from a three dimensional finite element model of a representative marine propeller is used as the boundary condition for the two dimensional plane strain investigations of stresses in the propeller blade and fillet. Stress predictions from the three dimensional analysis are compared with those from the two dimensional models. The validity of the plane strain modifications to the NASTRAN element is checked by comparing the modified CTRIA2 element stress predictions with those of the ABAQUS plane strain element, CPE4.

Fracture study of windshield glass panes

NASA Technical Reports Server (NTRS)

Yeh, H. Y.

1987-01-01

The major stresses which cause crack propagation in windshield glass panes are induced by bending moments which result from the pressure differentials across the panes. Hence the stress intensity factors for the finite plate with the semi-elliptical surface flaw and edge crack under the bending moments are examined. The results show that the crack growth will be upperbound if it is computed by using the stress intensity factor for the finite plate with the edge crack subjected to pure bending moments. Furthermore, if the ratio of crack depth to plate thickness, a/t, is within 0.3, the stress intensity factor can be conservatively assumed to be constant at the value of a/t equal to zero. A simplified equation to predict the structural life of glass panes is derived based on constant stress intensity factor. The accuracy of structural life is mainly dependent on how close the empirical parameter, m, can be estimated.

The surface crack problem in an orthotropic plate under bending and tension

NASA Technical Reports Server (NTRS)

Wu, Bing-Hua; Erdogan, F.

1987-01-01

The elasticity problem for an infinite orthotropic flat plate containing a series of through and part through cracks and subjected to bending and tension loads is considered. The problem is formulated by using Reissner's plate bending theory and considering three-dimensional material orthotropy. The Line-spring model developed by Rice and Levy is used to formulate the surface crack problem in which a total of nine material constants were used. The effects of material orthotropy on the stress intensity factors was determined, the interaction between two asymmetrically arranged collinear cracks was investigated, and extensive numerical results regarding the stress intensity factors are provided. The problem is reduced to a system of singular integral equations which is solved by using the Gauss-Chebyshev quadrature formulas. The calculated results show that the material orthotropy does have a significant effect on the stress intensity factor.

The surface crack problem in an orthotropic plate under bending and tension

NASA Technical Reports Server (NTRS)

Wu, B. H.; Erdogan, F.

1986-01-01

The elasticity problem for an infinite orthotropic flat plate containing a series of through and part-through cracks and subjected to bending and tension loads is considered. The problem is formulated by using Reissner's plate bending theory and considering three dimensional materials orthotropy. The Line-spring model developed by Rice and Levy is used to formulate the surface crack problem in which a total of nine material constants has been used. The main purpose of this study is to determine the effect of material orthotropy on the stress intensity factors, to investigate the interaction between two asymmetrically arranged collinear cracks, and to provide extensive numerical results regarding the stress intensity factors. The problem is reduced to a system of singular integral equations which is solved by using the Gauss-Chebyshev quadrature formulas. The calculated results show that the material orthotropy does have a significant effect on the stress intensity factor.

Deformation in Micro Roll Forming of Bipolar Plate

NASA Astrophysics Data System (ADS)

Zhang, P.; Pereira, M.; Rolfe, B.; Daniel, W.; Weiss, M.

2017-09-01

Micro roll forming is a new processing technology to produce bipolar plates for Proton Exchange Membrane Fuel Cells (PEMFC) from thin stainless steel foil. To gain a better understanding of the deformation of the material in this process, numerical studies are necessary before experimental implementation. In general, solid elements with several layers through the material thickness are required to analyse material thinning in processes where the deformation mode is that of bending combined with tension, but this results in high computational costs. This pure solid element approach is especially time-consuming when analysing roll forming processes which generally involves feeding a long strip through a number of successive roll stands. In an attempt to develop a more efficient modelling approach without sacrificing accuracy, two solutions are numerically analysed with ABAQUS/Explicit in this paper. In the first, a small patch of solid elements over the strip width and in the centre of the “pre-cut” sheet is coupled with shell elements while in the second approach pure shell elements are used to discretize the full sheet. In the first approach, the shell element enables accounting for the effect of material being held in the roll stands on material flow while solid elements can be applied to analyse material thinning in a small discrete area of the sheet. Experimental micro roll forming trials are performed to prove that the coupling of solid and shell elements can give acceptable model accuracy while using shell elements alone is shown to result in major deviations between numerical and experimental results.

Active shape control of composite blades using shape memory actuation

NASA Astrophysics Data System (ADS)

Chandra, Ramesh

2001-10-01

This paper presents active shape control of composite beams using shape memory actuation. Shape memory alloy (SMA) bender elements trained to memorize bending shape were used to induce bending and twisting deformations in composite beams. Bending-torsion coupled graphite-epoxy and kevlar-epoxy composite beams with Teflon inserts were manufactured using an autoclave-molding technique. Teflon inserts were replaced by trained SMA bender elements. Composite beams with SMA bender elements were activated by heating these using electrical resistive heating and the bending and twisting deformations of the beams were measured using a mirror and laser system. The structural response of the composite beams activated by SMA elements was predicted using the Vlasov theory, where these beams were modeled as open sections with many branches. The bending moment induced by a SMA bender element was calculated from its experimentally determined memorized shape. The bending, torsion, and bending-torsion coupling stiffness coefficients of these beams were obtained using analytical formulation of an open-section composite beam with many branches (Vlasov theory).

Approximate analytical solutions in the analysis of thin elastic plates

NASA Astrophysics Data System (ADS)

Goloskokov, Dmitriy P.; Matrosov, Alexander V.

2018-05-01

Two approaches to the construction of approximate analytical solutions for bending of a rectangular thin plate are presented: the superposition method based on the method of initial functions (MIF) and the one built using the Green's function in the form of orthogonal series. Comparison of two approaches is carried out by analyzing a square plate clamped along its contour. Behavior of the moment and the shear force in the neighborhood of the corner points is discussed. It is shown that both solutions give identical results at all points of the plate except for the neighborhoods of the corner points. There are differences in the values of bending moments and generalized shearing forces in the neighborhoods of the corner points.

Comminuted supracondylar femoral fractures: a biomechanical analysis comparing the stability of medial versus lateral plating in axial loading.

PubMed

Briffa, Nikolai; Karthickeyan, Raju; Jacob, Joshua; Khaleel, Arshad

2016-11-01

The aim of this study was to compare the biomechanical properties of medial and lateral plating of a medially comminuted supracondylar femoral fracture. A supracondylar femoral fracture model comparing two fixation methods was tested cyclically in axial loading. One-centimetre supracondylar gap osteotomies were created in six synthetic femurs approximately 6 cm proximal to the knee joint. There were two constructs investigated: group 1 and group 2 were stabilized with an 8-hole LC-DCP, medially and laterally, respectively. Both construct groups were axially loaded. Global displacement (total length), wedge displacement, bending moment and strain were measured. Medial plating showed a significantly decreased displacement, bending moment and strain at the fracture site in axial loading. Medial plating of a comminuted supracondylar femur fracture is more stable than lateral plating.

Finite element analysis of stress distribution on the mandible and condylar fracture osteosynthesis during various clenching tasks.

PubMed

Hijazi, Loai; Hejazi, Wael; Darwich, Mhd Ayham; Darwich, Khaldoun

2016-12-01

The purpose of the study was to evaluate the effect of clenching tasks on the stress and strain of condylar osteosynthesis screws and plates, as well as on the stress, strain distribution and displacement on the whole mandible and bone surrounding screws. Three-dimensional finite element models of the mandible, two straight four-hole plates and eight screws were established. Six static clenching tasks were simulated in this study: incisal clench (INC), intercuspal position (ICP), right unilateral molar clench (RMOL), left unilateral molar clench (LMOL), right group function (RGF) and left group function (LGF). Based on the simulation of the six clenching tasks, none of the inserted screws and plates were broken or bended. For the whole mandibular bone, the maximum von Mises stress and von Mises strain observed were yielded by the ICP. For the bone surrounding the inserted screws, the maximum von Mises stress and von Mises strain were yielded by the LMOL (49.2 MPa and 3795.1 μ). Clenching tasks had significant effects on the stress distribution on the condylar osteosynthesis and the bone surrounding screws. Contralateral occlusion task (LMOL) had the maximal results of von Mises stress and strain and healing problems could be occur, this result confirms the importance of soft diet after surgery.

Mode I stress intensity factors of slanted cracks in plates

NASA Astrophysics Data System (ADS)

Ismail, Al Emran; Ghazali, Mohd Zubir Mohd; Nor, Nik Hisyamudin Muhd

2017-01-01

This paper presents the roles of slanted cracks on the stress intensity factors (SIF) under mode I tension and bending loading. Based on the literature survey, lack of solution of SIFs of slanted cracks in plain strain plates are available. In this work, the cracks are modelled numerically using ANSYS finite element program. There are two important parameters such as slanted angles and relative crack length. SIFs at the crack tips are calculated according to domain integral method. Before the model is further used, it is validated with the existing model. It is found that the present model is well agreed with the previous model. According to finite element analysis, there are not only mode I SIFs produced but also mode II. As expected the SIFs increased as the relative crack length increased. However, when slanted angles are introduced (slightly higher than normal crack), the SIFs increased. Once the angles are further increased, the SIFs decreased gradually however they are still higher than the SIFs of normal cracks. For mode II SIFs, higher the slanted angels higher the SIFs. This is due to the fact that when the cracks are slanted, the cracked plates are not only failed due to mode I but a combination between both modes I and II.

Coupling between shear and bending in the analysis of beam problems: Planar case

NASA Astrophysics Data System (ADS)

Shabana, Ahmed A.; Patel, Mohil

2018-04-01

The interpretation of invariants, such as curvatures which uniquely define the bending and twist of space curves and surfaces, is fundamental in the formulation of the beam and plate elastic forces. Accurate representations of curve and surface invariants, which enter into the definition of the strain energy equations, is particularly important in the case of large displacement analysis. This paper discusses this important subject in view of the fact that shear and bending are independent modes of deformation and do not have kinematic coupling; this is despite the fact that kinetic coupling may exist. The paper shows, using simple examples, that shear without bending and bending without shear at an arbitrary point and along a certain direction are scenarios that higher-order finite elements (FE) can represent with a degree of accuracy that depends on the order of interpolation and/or mesh size. The FE representation of these two kinematically uncoupled modes of deformation is evaluated in order to examine the effect of the order of the polynomial interpolation on the accuracy of representing these two independent modes. It is also shown in this paper that not all the curvature vectors contribute to bending deformation. In view of the conclusions drawn from the analysis of simple beam problems, the material curvature used in several previous investigations is evaluated both analytically and numerically. The problems associated with the material curvature matrix, obtained using the rotation of the beam cross-section, and the fundamental differences between this material curvature matrix and the Serret-Frenet curvature matrix are discussed.

Using global, quantitative models of the coupled plates/mantle system to understand Late Miocene dynamics of the Pacific plate

NASA Astrophysics Data System (ADS)

Stotz, Ingo; Iaffaldano, Giampiero; Rhodri Davies, D.

2017-04-01

Knowledge of the evolution of continents, inferred from a variety of geological data, as well as observations of the ocean-floor magnetization pattern provide an increasingly-detailed picture of past and present-day plate motions. These are key to study the evolving balance of shallow- and deep-rooted forces acting upon plates and to unravel the dynamics of the coupled plates/mantle system. Here we focus on the clockwise rotation of the Pacific plate motion relative to the hotspots reference frame between 10 and 5 Ma, which is evidenced by a bend in the Hawaiian sea mount chain (Cox & Engebretson, 1985) as well as by marine magnetic and bathymetric data along the Pacific/Antarctica Ridge (Croon et al., 2008). It has been suggested that such a kinematic change owes to the arrival of the Ontong-Java plateau, the biggest oceanic plateau on the Pacific plate, at the Australia/Pacific subducting margin between 10 and 5 Ma, and to its collision with the Melanesian arc. This could have changed the local buoyancy forces and/or sparked a redistribution of the forces already acting within the Pacific realm, causing the Pacific plate to rotate clockwise. Such hypotheses have never been tested explicitly against the available kinematic reconstructions. We do so by using global numerical models of the coupled plates/mantle system. Our models build on the available codes Terra and Shells. Terra is a global, spherical finite-element code for mantle convection, developed by Baumgardner (1985) and Bunge et al. (1996), and further advanced by Yang (1997; 2000) and Davies et al. (2013), among others. Shells is a thin-sheet, finite-element code for lithosphere dynamics (e.g., Bird, 1998). By merging these two independent models we are able to simulate the rheological behavior of the brittle lithosphere and viscous mantle. We compare the plate velocities output by our models with the available kinematic reconstructions to test the above-mentioned hypotheses, and simulate the impact of the evolving mantle buoyancy-field and plate-boundary forces on the Pacific plate motion. Our approach allows linking geodynamical models and observations on the recent dynamics of the Pacific plate.

Internal and edge cracks in a plate of finite width under bending

NASA Technical Reports Server (NTRS)

Boduroglu, H.; Erdogan, F.

1983-01-01

Internal and edge cracks were studied by using Reissner's transverse shear theory. The effect of stress-free boundaries on the stress intensity factors in plates under bending were investigated. Among the results found, particularly interesting are those relating to the limiting cases of the crack geometries. The numerical results are given for a single internal crack, two collinear cracks, and two edge cracks. The effect of Poisson's ratio on the stress intensity factors was studied.

[Biomechanical research of antegrade intramedullary fixation for the metacarpal fractures].

PubMed

Zhang, Li-shan; Pan, Yong-wei; Tian, Guang-lei; Li, Wen-jun; Xia, Shao-hua; Tao, Jian-feng

2010-04-15

To study the biomechanical characteristics of antegrade intramedullary fixation for metacarpal fractures. From March to May 2008, both the 4th and 5th metacarpals from 25 formalin embalmed cadaver hands had three-point bending test after transverse osteotomy followed by randomly fixation with one of the following three methods: plate and screw, antegrade intramedullary K-wire, crossed K-wire. While, both the 2nd and 3rd metacarpals had torsional loading test after the same management as the 4th and 5th metacarpal had undergone. In the three-point bending test, both the maximum bending moment (M(max)) and bending rigidity (EI) of the antegrade intramedullary K-wire were comparable with those of the plate and screw, and were significantly larger than those of the crossed K-wire. In the torsional loading test, the antegrade intramedullary K-wire had a statistically smaller maximum torque (T(max)) than the plate and screw, and had a comparable T(max) with the crossed K-wire; while, the torsional rigidity (GJ) of the intramedullary K-wire was statistically weaker than that of both the plate and screw and the crossed wire. One single antegrade intramedullary K-wire can provide a satisfactory M(max) and EI for metacarpal fixation and shows relatively weak in the torsional loading test. The injured finger should be well protected to avoid torsional deformity in clinical practice.

A New Absolute Plate Motion Model for Africa

NASA Astrophysics Data System (ADS)

Maher, S. M.; Wessel, P.; Müller, D.; Harada, Y.

2013-12-01

The India-Eurasia collision, a change in relative plate motion between Australia and Antarctica, and the coeval ages of the Hawaiian Emperor Bend (HEB) and Louisville Bend of ~Chron 22-21 all provide convincing evidence of a global tectonic plate reorganization at ~50 Ma. Yet if it were a truly global event, then there should be a contemporaneous change in Africa absolute plate motion (APM) reflected by physical evidence somewhere on the Africa plate. This evidence might be visible in the Reunion-Mascarene bend, which exhibits many HEB-like features such as a large angular change close to ~50 Ma. Recently, the Reunion hotpot trail has been interpreted as a continental feature with incidental hotspot volcanism. Here we propose the alternative hypothesis that the northern portion of the chain between Saya de Malha and the Seychelles (Mascarene Plateau) formed as the Reunion hotspot was situated on the Carlsberg Ridge, contemporaneously forming the Chagos-Laccadive Ridge on the India plate. We have created a 4-stage model that explores how a simple APM model fitting the Mascarene Plateau can also satisfy the age progressions and geometry of other hotspot trails on the Africa plate. This type of model could explain the apparent bifurcation of the Tristan hotspot chain, the age reversals seen along the Walvis Ridge and the diffuse nature of the St. Helena chain. To test this hypothesis we have made a new African APM model that goes back to ~80 Ma using a modified version of the Hybrid Polygonal Finite Rotation Method. This method uses seamount chains and their associated hotspots as geometric constraints for the model, and seamount age dates to determine its motion through time. The positions of the hotspots can be moved to get the best fit for the model and to explore the possibility that the ~50 Ma bend in the Reunion-Mascarene chain reflects Africa plate motion. We will examine how well this model can predict the key features reflecting Africa plate motion and contrast its predictions with other proposed models.

A global/local analysis method for treating details in structural design

NASA Technical Reports Server (NTRS)

Aminpour, Mohammad A.; Mccleary, Susan L.; Ransom, Jonathan B.

1993-01-01

A method for analyzing global/local behavior of plate and shell structures is described. In this approach, a detailed finite element model of the local region is incorporated within a coarser global finite element model. The local model need not be nodally compatible (i.e., need not have a one-to-one nodal correspondence) with the global model at their common boundary; therefore, the two models may be constructed independently. The nodal incompatibility of the models is accounted for by introducing appropriate constraint conditions into the potential energy in a hybrid variational formulation. The primary advantage of this method is that the need for transition modeling between global and local models is eliminated. Eliminating transition modeling has two benefits. First, modeling efforts are reduced since tedious and complex transitioning need not be performed. Second, errors due to the mesh distortion, often unavoidable in mesh transitioning, are minimized by avoiding distorted elements beyond what is needed to represent the geometry of the component. The method is applied reduced to a plate loaded in tension and transverse bending. The plate has a central hole, and various hole sixes and shapes are studied. The method is also applied to a composite laminated fuselage panel with a crack emanating from a window in the panel. While this method is applied herein to global/local problems, it is also applicable to the coupled analysis of independently modeled components as well as adaptive refinement.

A square-plate piezoelectric linear motor operating in two orthogonal and isomorphic face-diagonal-bending modes.

PubMed

Ci, Penghong; Chen, Zhijiang; Liu, Guoxi; Dong, Shuxiang

2014-01-01

We report a piezoelectric linear motor made of a single Pb(Zr,Ti)O3 square-plate, which operates in two orthogonal and isomorphic face-diagonal-bending modes to produce precision linear motion. A 15 × 15 × 2 mm prototype was fabricated, and the motor generated a driving force of up to 1.8 N and a speed of 170 mm/s under an applied voltage of 100 Vpp at the resonance frequency of 136.5 kHz. The motor shows such advantages as large driving force under relatively low driving voltage, simple structure, and stable motion because of its isomorphic face-diagonal-bending mode.

Bending analysis of embedded nanoplates based on the integral formulation of Eringen's nonlocal theory using the finite element method

NASA Astrophysics Data System (ADS)

Ansari, R.; Torabi, J.; Norouzzadeh, A.

2018-04-01

Due to the capability of Eringen's nonlocal elasticity theory to capture the small length scale effect, it is widely used to study the mechanical behaviors of nanostructures. Previous studies have indicated that in some cases, the differential form of this theory cannot correctly predict the behavior of structure, and the integral form should be employed to avoid obtaining inconsistent results. The present study deals with the bending analysis of nanoplates resting on elastic foundation based on the integral formulation of Eringen's nonlocal theory. Since the formulation is presented in a general form, arbitrary kernel functions can be used. The first order shear deformation plate theory is considered to model the nanoplates, and the governing equations for both integral and differential forms are presented. Finally, the finite element method is applied to solve the problem. Selected results are given to investigate the effects of elastic foundation and to compare the predictions of integral nonlocal model with those of its differential nonlocal and local counterparts. It is found that by the use of proposed integral formulation of Eringen's nonlocal model, the paradox observed for the cantilever nanoplate is resolved.

Comparison of conventional reconstruction plate versus direct metal laser sintering plate: an in vitro mechanical characteristics study.

PubMed

Xie, Pusheng; Ouyang, Hanbin; Deng, Yuping; Yang, Yang; Xu, Jing; Huang, Wenhua

2017-09-02

Additive manufacturing (AM) technology has helped to achieve several advances in the medical field, particularly as far as fabrication of implants is concerned. But the application of direct metal laser sintering (DMLS) bone plate is quite limited due to the indeterminate mechanical property. The purposes of this study were to characterize the biomechanical properties of the polished DMLS reconstruction plate and to compare these with the properties of commonly applied implants and to find whether the mechanical performance of DMLS plate meets the requirements for clinical application. In this study, we fabricated two groups of plates by DMLS and computer numerical control (CNC) techniques. After that, we polished all samples and investigated their roughness, components, hardness, static bending, and torsional performance. Moreover, cyclic bending tests and fractographic analysis were conducted. Statistical comparisons of the group by means of monotonic test data were made, and a qualitative comparison was performed to assess failures in fatigue. We found no differences in surface roughness or components after polishing, but the DMLS plate hardness is 7.42% (p < 0.01) greater than that of the CNC plates. Compared with the CNC plates, the DMLS plate static bending and torsional performance were significantly greater. In a dynamic test, the DMLS plates survived 10 6 , 10 6 , 32,731, and 33,264 cycles under 0.6, 0.8, 0.9, and 1 kN cyclic loads, respectively, while the CNC plates survived 10 6 , 10 6 , 10 6 , and 283,714 cycles. These results indicate that the mechanical performances of the DMLS plate are stronger, and the strength under fatigue tests is sufficient. DMLS implant has great potential and may become a better choice for clinical use in the future. However, direct application of these AM instruments in the operating room requires further validation including animal and clinical experiment.

Biomechanical Study of the Fixation Strength of Anteromedial Plating for Humeral Shaft Fractures

PubMed Central

Zheng, Yin-Feng; Zhou, Jun-Lin; Wang, Xiao-Hong; Shan, Lei; Liu, Yang

2016-01-01

Background: Open reduction and internal fixation with plate and screws are the gold standard for the surgical treatment of humeral shaft fractures, this study was to compare the mechanical properties of anteromedial, anterolateral, and posterior plating for humeral shaft fractures. Methods: A distal third humeral shaft fracture model was constructed using fourth-generation sawbones (#3404, composite bone). A total of 24 sawbones with a distal third humeral shaft fracture was randomly divided into three Groups: A, B, and C (n = 8 in each group) for anteromedial, anterolateral, and posterior plating, respectively. All sawbones were subjected to horizontal torsional fatigue tests, horizontal torsional and axial compressive fatigue tests, four-point bending fatigue tests in anteroposterior (AP) and mediolateral (ML) directions and horizontal torsional destructive tests. Results: In the horizontal torsional fatigue tests, the mean torsional angle amplitude in Groups A, B, and C were 6.12°, 6.53°, and 6.81°. In horizontal torsional and axial compressive fatigue tests, the mean torsional angle amplitude in Groups A, B, and C were 5.66°, 5.67°, and 6.36°. The mean plate displacement amplitude was 0.05 mm, 0.08 mm, and 0.10 mm. Group A was smaller than Group C (P < 0.05). In AP four-point bending fatigue tests, the mean plate displacement amplitude was 0.16 mm, 0.13 mm, and 0.20 mm. Group B was smaller than Group C (P < 0.05). In ML four-point bending fatigue tests, the mean plate displacement amplitude were 0.16 mm, 0.19 mm, and 0.17 mm. In horizontal torsional destructive tests, the mean torsional rigidity in Groups A, B, and C was 0.82, 0.75, and 0.76 N·m/deg. The yielding torsional angle was 24.50°, 25.70°, and 23.86°. The mean yielding torque was 18.46, 18.05, and 16.83 N·m, respectively. Conclusions: Anteromedial plating was superior to anterolateral or posterior plating in all mechanical tests except in AP four-point bending fatigue tests compared to the anterolateral plating group. We can suggest that anteromedial plating is a clinically safe and effective way for humeral shaft fractures. PMID:27453236

Numerical analysis of beam with sinusoidally corrugated webs

NASA Astrophysics Data System (ADS)

Górecki, Marcin; Pieńko, Michał; Łagoda, GraŻyna

2018-01-01

The paper presents numerical tests results of the steel beam with sinusoidally corrugated web, which were performed in the Autodesk Algor Simulation Professional 2010. The analysis was preceded by laboratory tests including the beam's work under the influence of the four point bending as well as the study of material characteristics. Significant web's thickness and use of tools available in the software allowed to analyze the behavior of the plate girder as beam, and also to observe the occurrence of stresses in the characteristic element - the corrugated web. The stress distribution observed on the both web's surfaces was analyzed.

Analysis of Delamination Growth from Matrix Cracks in Laminates Subjected to Bending Loads

NASA Technical Reports Server (NTRS)

Murri, G. B.; Guynn, E. G.

1986-01-01

A major source of delamination damage in laminated composite materials is from low-velocity impact. In thin composite laminates under point loads, matrix cracks develop first in the plies, and delaminations then grow from these cracks at the ply interfaces. The purpose of this study was to quantify the combined effects of bending and transverse shear loads on delamination initiation from matrix cracks. Graphite-epoxy laminates with 90 deg. plies on the outside were used to provide a two-dimensional simulation of the damage due to low-velocity impact. Three plate bending problems were considered: a 4-point bending, 3-point bending, and an end-clamped center-loaded plate. Under bending, a matrix crack will form on the tension side of the laminate, through the outer 90 deg. plies and parallel to the fibers. Delaminations will then grow in the interface between the cracked 90 deg. ply and the next adjacent ply. Laminate plate theory was used to derive simple equations relating the total strain energy release rate, G, associated with the delamination growth from a 90 deg. ply crack to the applied bending load and laminate stiffness properties. Three different lay-ups were tested and results compared. Test results verified that the delamination always formed at the interface between the cracked 90 deg. ply and the next adjacent ply. Calculated values for total G sub c from the analysis showed good agreement for all configurations. The analysis was able to predict the delamination onset load for the cases considered. The result indicated that the opening mode component (Mode I) for delamination growth from a matrix crack may be much larger than the component due to interlaminar shear (Mode II).

Corrosion-Fatigue Crack Growth in Plates: A Model Based on the Paris Law

PubMed Central

Toribio, Jesús; Matos, Juan-Carlos; González, Beatriz

2017-01-01

In this paper, a Paris law-based model is presented whereby crack propagation occurs under cyclic loading in air (fatigue) and in an aggressive environment (corrosion-fatigue) for the case of corner cracks (with a wide range of aspect ratios in the matter of the initial cracks) in finite-thickness plates of 316L austenitic stainless steel subjected to tension, bending, or combined (tension + bending) loading. Results show that the cracks tend during their growth towards a preferential propagation path, exhibiting aspect ratios slightly lower than unity only for the case of very shallow cracks, and diminishing as the crack grows (increasing the relative crack depth)—more intensely in the case of bending than in the case of tension (the mixed loading tension/bending representing an intermediate case). In addition, the crack aspect ratios during fatigue propagation evolution are lower in fatigue (in air) than in corrosion-fatigue (in aggressive environment). PMID:28772798

Lithospheric flexure under the Hawaiian volcanic load: Internal stresses and a broken plate revealed by earthquakes

NASA Astrophysics Data System (ADS)

Klein, Fred W.

2016-04-01

Several lines of earthquake evidence indicate that the lithospheric plate is broken under the load of the island of Hawai`i, where the geometry of the lithosphere is circular with a central depression. The plate bends concave downward surrounding a stress-free hole, rather than bending concave upward as with past assumptions. Earthquake focal mechanisms show that the center of load stress and the weak hole is between the summits of Mauna Loa and Mauna Kea where the load is greatest. The earthquake gap at 21 km depth coincides with the predicted neutral plane of flexure where horizontal stress changes sign. Focal mechanism P axes below the neutral plane display a striking radial pattern pointing to the stress center. Earthquakes above the neutral plane in the north part of the island have opposite stress patterns; T axes tend to be radial. The M6.2 Honomu and M6.7 Kiholo main shocks (both at 39 km depth) are below the neutral plane and show radial compression, and the M6.0 Kiholo aftershock above the neutral plane has tangential compression. Earthquakes deeper than 20 km define a donut of seismicity around the stress center where flexural bending is a maximum. The hole is interpreted as the soft center where the lithospheric plate is broken. Kilauea's deep conduit is seismically active because it is in the ring of maximum bending. A simplified two-dimensional stress model for a bending slab with a load at one end yields stress orientations that agree with earthquake stress axes and radial P axes below the neutral plane. A previous inversion of deep Hawaiian focal mechanisms found a circular solution around the stress center that agrees with the model. For horizontal faults, the shear stress within the bending slab matches the slip in the deep Kilauea seismic zone and enhances outward slip of active flanks.

Lithospheric flexure under the Hawaiian volcanic load: Internal stresses and a broken plate revealed by earthquakes

USGS Publications Warehouse

Klein, Fred W.

2016-01-01

Several lines of earthquake evidence indicate that the lithospheric plate is broken under the load of the island of Hawai`i, where the geometry of the lithosphere is circular with a central depression. The plate bends concave downward surrounding a stress-free hole, rather than bending concave upward as with past assumptions. Earthquake focal mechanisms show that the center of load stress and the weak hole is between the summits of Mauna Loa and Mauna Kea where the load is greatest. The earthquake gap at 21 km depth coincides with the predicted neutral plane of flexure where horizontal stress changes sign. Focal mechanism P axes below the neutral plane display a striking radial pattern pointing to the stress center. Earthquakes above the neutral plane in the north part of the island have opposite stress patterns; T axes tend to be radial. The M6.2 Honomu and M6.7 Kiholo main shocks (both at 39 km depth) are below the neutral plane and show radial compression, and the M6.0 Kiholo aftershock above the neutral plane has tangential compression. Earthquakes deeper than 20 km define a donut of seismicity around the stress center where flexural bending is a maximum. The hole is interpreted as the soft center where the lithospheric plate is broken. Kilauea's deep conduit is seismically active because it is in the ring of maximum bending. A simplified two-dimensional stress model for a bending slab with a load at one end yields stress orientations that agree with earthquake stress axes and radial P axes below the neutral plane. A previous inversion of deep Hawaiian focal mechanisms found a circular solution around the stress center that agrees with the model. For horizontal faults, the shear stress within the bending slab matches the slip in the deep Kilauea seismic zone and enhances outward slip of active flanks.

Improved Design Formulae for Buckling of Orthotropic Plates under Combined Loading

NASA Technical Reports Server (NTRS)

Weaver, Paul M.; Nemeth, Michael P.

2008-01-01

Simple, accurate buckling interaction formulae are presented for long orthotropic plates with either simply supported or clamped longitudinal edges and under combined loading that are suitable for design studies. The loads include 1) combined uniaxial compression (or tension) and shear, 2) combined pure inplane bending and 3) shear and combined uniaxial compression (or tension) and pure inplane bending. The interaction formulae are the results of detailed regression analysis of buckling data obtained from a very accurate Rayleigh-Ritz method.

The Use of Doublers in Delamination Toughness Testing

NASA Technical Reports Server (NTRS)

Reeder, James R.; Demarco, Kevin; Whitley, Karen S.

2002-01-01

In this paper, the data reduction equations for common delamination toughness tests are rederived for use with specimens which have bonded doublers. The common toughness tests considered here are the double cantilever beam (DCB) for mode I toughness; the end notch flexure (3ENF) and 4 point ENF (4ENF) for mode II toughness; and the mixed mode bending (MMB) test for testing under combined mode I and mode II loading. Because the addition of the doublers changes the bending stiffness of the specimens, these data reduction equations may need to be corrected. Doublers were added to the delamination test specimens to solve a premature failure problem. Delamination toughness is normally tested using a beam with an imbedded insert so that one end of the specimen is split into two arms. If the specimen is too thin, or if the toughness of the material is too high, an arm of the specimen may fail in bending before the delamination grows. When this occurs, the toughness of the material cannot be determined. To delay the bending failure so that delamination growth occurs, doubler plates were bonded to both top and bottom surfaces of the specimen. A doubler parameter, beta, which describes how much the use of doubler plates changed the ratio of full thickness to delaminated bending stiffnesses, was defined. When changes to the data reduction equations were required, the changes were minor when written in terms of the beta parameter. The doubler plate technique was demonstrated by measuring the mixed-mode fracture toughness of a carbon-carbon composite using test specimens which would otherwise have failed before delamination growth occurred. The doubler plate technique may solve several problems that can be encountered when testing delamination fracture toughness.

A comparison between different finite elements for elastic and aero-elastic analyses.

PubMed

Mahran, Mohamed; ELsabbagh, Adel; Negm, Hani

2017-11-01

In the present paper, a comparison between five different shell finite elements, including the Linear Triangular Element, Linear Quadrilateral Element, Linear Quadrilateral Element based on deformation modes, 8-node Quadrilateral Element, and 9-Node Quadrilateral Element was presented. The shape functions and the element equations related to each element were presented through a detailed mathematical formulation. Additionally, the Jacobian matrix for the second order derivatives was simplified and used to derive each element's strain-displacement matrix in bending. The elements were compared using carefully selected elastic and aero-elastic bench mark problems, regarding the number of elements needed to reach convergence, the resulting accuracy, and the needed computation time. The best suitable element for elastic free vibration analysis was found to be the Linear Quadrilateral Element with deformation-based shape functions, whereas the most suitable element for stress analysis was the 8-Node Quadrilateral Element, and the most suitable element for aero-elastic analysis was the 9-Node Quadrilateral Element. Although the linear triangular element was the last choice for modal and stress analyses, it establishes more accurate results in aero-elastic analyses, however, with much longer computation time. Additionally, the nine-node quadrilateral element was found to be the best choice for laminated composite plates analysis.

Methods for In-Flight Wing Shape Predictions of Highly Flexible Unmanned Aerial Vehicles: Formulation of Ko Displacement Theory

NASA Technical Reports Server (NTRS)

Ko, William L.; Fleischer, Van Tran

2010-01-01

The Ko displacement theory is formulated for a cantilever tubular wing spar under bending, torsion, and combined bending and torsion loading. The Ko displacement equations are expressed in terms of strains measured at multiple sensing stations equally spaced on the surface of the wing spar. The bending and distortion strain data can then be input to the displacement equations to calculate slopes, deflections, and cross-sectional twist angles of the wing spar at the strain-sensing stations for generating the deformed shapes of flexible aircraft wing spars. The displacement equations have been successfully validated for accuracy by finite-element analysis. The Ko displacement theory that has been formulated could also be applied to calculate the deformed shape of simple and tapered beams, plates, and tapered cantilever wing boxes. The Ko displacement theory and associated strain-sensing system (such as fiber optic sensors) form a powerful tool for in-flight deformation monitoring of flexible wings and tails, such as those often employed on unmanned aerial vehicles. Ultimately, the calculated displacement data can be visually displayed in real time to the ground-based pilot for monitoring the deformed shape of unmanned aerial vehicles during flight.

Buckling transition and boundary layer in non-Euclidean plates.

PubMed

Efrati, Efi; Sharon, Eran; Kupferman, Raz

2009-07-01

Non-Euclidean plates are thin elastic bodies having no stress-free configuration, hence exhibiting residual stresses in the absence of external constraints. These bodies are endowed with a three-dimensional reference metric, which may not necessarily be immersible in physical space. Here, based on a recently developed theory for such bodies, we characterize the transition from flat to buckled equilibrium configurations at a critical value of the plate thickness. Depending on the reference metric, the buckling transition may be either continuous or discontinuous. In the infinitely thin plate limit, under the assumption that a limiting configuration exists, we show that the limit is a configuration that minimizes the bending content, among all configurations with zero stretching content (isometric immersions of the midsurface). For small but finite plate thickness, we show the formation of a boundary layer, whose size scales with the square root of the plate thickness and whose shape is determined by a balance between stretching and bending energies.

The complex variable reproducing kernel particle method for bending problems of thin plates on elastic foundations

NASA Astrophysics Data System (ADS)

Chen, L.; Cheng, Y. M.

2018-07-01

In this paper, the complex variable reproducing kernel particle method (CVRKPM) for solving the bending problems of isotropic thin plates on elastic foundations is presented. In CVRKPM, one-dimensional basis function is used to obtain the shape function of a two-dimensional problem. CVRKPM is used to form the approximation function of the deflection of the thin plates resting on elastic foundation, the Galerkin weak form of thin plates on elastic foundation is employed to obtain the discretized system equations, the penalty method is used to apply the essential boundary conditions, and Winkler and Pasternak foundation models are used to consider the interface pressure between the plate and the foundation. Then the corresponding formulae of CVRKPM for thin plates on elastic foundations are presented in detail. Several numerical examples are given to discuss the efficiency and accuracy of CVRKPM in this paper, and the corresponding advantages of the present method are shown.

Dynamic properties and damping predictions for laminated plates: High order theories - Timoshenko beam

NASA Astrophysics Data System (ADS)

Diveyev, Bohdan; Konyk, Solomija; Crocker, Malcolm J.

2018-01-01

The main aim of this study is to predict the elastic and damping properties of composite laminated plates. This problem has an exact elasticity solution for simple uniform bending and transverse loading conditions. This paper presents a new stress analysis method for the accurate determination of the detailed stress distributions in laminated plates subjected to cylindrical bending. Some approximate methods for the stress state predictions for laminated plates are presented here. The present method is adaptive and does not rely on strong assumptions about the model of the plate. The theoretical model described here incorporates deformations of each sheet of the lamina, which account for the effects of transverse shear deformation, transverse normal strain-stress and nonlinear variation of displacements with respect to the thickness coordinate. Predictions of the dynamic and damping values of laminated plates for various geometrical, mechanical and fastening properties are presented. Comparison with the Timoshenko beam theory is systematically made for analytical and approximation variants.

A novel vibration measurement and active control method for a hinged flexible two-connected piezoelectric plate

NASA Astrophysics Data System (ADS)

Qiu, Zhi-cheng; Wang, Xian-feng; Zhang, Xian-Min; Liu, Jin-guo

2018-07-01

A novel non-contact vibration measurement method using binocular vision sensors is proposed for piezoelectric flexible hinged plate. Decoupling methods of the bending and torsional low frequency vibration on measurement and driving control are investigated, using binocular vision sensors and piezoelectric actuators. A radial basis function neural network controller (RBFNNC) is designed to suppress both the larger and the smaller amplitude vibrations. To verify the non-contact measurement method and the designed controller, an experimental setup of the flexible hinged plate with binocular vision is constructed. Experiments on vibration measurement and control are conducted by using binocular vision sensors and the designed RBFNNC controllers, compared with the classical proportional and derivative (PD) control algorithm. The experimental measurement results demonstrate that the binocular vision sensors can detect the low-frequency bending and torsional vibration effectively. Furthermore, the designed RBF can suppress the bending vibration more quickly than the designed PD controller owing to the adjustment of the RBF control, especially for the small amplitude residual vibrations.

Investigation of Methods for Selectively Reinforcing Aluminum and Aluminum-Lithium Materials

NASA Technical Reports Server (NTRS)

Bird, R. Keith; Alexa, Joel A.; Messick, Peter L.; Domack, Marcia S.; Wagner, John A.

2013-01-01

Several studies have indicated that selective reinforcement offers the potential to significantly improve the performance of metallic structures for aerospace applications. Applying high-strength, high-stiffness fibers to the high-stress regions of aluminum-based structures can increase the structural load-carrying capability and inhibit fatigue crack initiation and growth. This paper discusses an investigation into potential methods for applying reinforcing fibers onto the surface of aluminum and aluminum-lithium plate. Commercially-available alumina-fiber reinforced aluminum alloy tapes were used as the reinforcing material. Vacuum hot pressing was used to bond the reinforcing tape to aluminum alloy 2219 and aluminum-lithium alloy 2195 base plates. Static and cyclic three-point bend testing and metallurgical analysis were used to evaluate the enhancement of mechanical performance and the integrity of the bond between the tape and the base plate. The tests demonstrated an increase in specific bending stiffness. In addition, no issues with debonding of the reinforcing tape from the base plate during bend testing were observed. The increase in specific stiffness indicates that selectively-reinforced structures could be designed with the same performance capabilities as a conventional unreinforced structure but with lower mass.

Active vibration control of thin-plate structures with partial SCLD treatment

NASA Astrophysics Data System (ADS)

Lu, Jun; Wang, Pan; Zhan, Zhenfei

2017-02-01

To effectively suppress the low-frequency vibration of a thin-plate, the strategy adopted is to develop a model-based approach to the investigation on the active vibration control of a clamped-clamped plate with partial SCLD treatment. Firstly, a finite element model is developed based on the constitutive equations of elastic, piezoelectric and viscoelastic materials. The characteristics of viscoelastic materials varying with temperature and frequency are described by GHM damping model. A low-dimensional real modal control model which can be used as the basis for active vibration control is then obtained from the combined reduction. The emphasis is placed on the feedback control system to attenuate the vibration of plates with SCLD treatments. A modal controller in conjunction with modal state estimator is designed to solve the problem of full state feedback, making it much more feasible to real-time control. Finally, the theoretical model is verified by modal test, and an active vibration control is validated by hardware-in-the-loop experiment under different external excitations. The numerical and experimental study demonstrate how the piezoelectric actuators actively control the lower modes (first bending and torsional modes) using modal controller, while the higher frequency vibration attenuated by viscoelastic passive damping layer.

Four-point Bend Testing of Irradiated Monolithic U-10Mo Fuel

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rabin, B. H.; Lloyd, W. R.; Schulthess, J. L.

2015-03-01

This paper presents results of recently completed studies aimed at characterizing the mechanical properties of irradiated U-10Mo fuel in support of monolithic base fuel qualification. Mechanical properties were evaluated in four-point bending. Specimens were taken from fuel plates irradiated in the RERTR-12 and AFIP-6 Mk. II irradiation campaigns, and tests were conducted in the Hot Fuel Examination Facility (HFEF) at Idaho National Laboratory (INL). The monolithic fuel plates consist of a U-10Mo fuel meat covered with a Zr diffusion barrier layer fabricated by co-rolling, clad in 6061 Al using a hot isostatic press (HIP) bonding process. Specimens exhibited nominal (fresh)more » fuel meat thickness ranging from 0.25 mm to 0.64 mm, and fuel plate average burnup ranged from approximately 0.4 x 1021 fissions/cm 3 to 6.0 x 1021 fissions/cm 3. After sectioning the fuel plates, the 6061 Al cladding was removed by dissolution in concentrated NaOH. Pre- and post-dissolution dimensional inspections were conducted on test specimens to facilitate accurate analysis of bend test results. Four-point bend testing was conducted on the HFEF Remote Load Frame at a crosshead speed of 0.1 mm/min using custom-designed test fixtures and calibrated load cells. All specimens exhibited substantially linear elastic behavior and failed in a brittle manner. The influence of burnup on the observed slope of the stress-strain curve and the calculated fracture strength is discussed.« less

Design of responsive materials using topologically interlocked elements

NASA Astrophysics Data System (ADS)

Molotnikov, A.; Gerbrand, R.; Qi, Y.; Simon, G. P.; Estrin, Y.

2015-02-01

In this work we present a novel approach to designing responsive structures by segmentation of monolithic plates into an assembly of topologically interlocked building blocks. The particular example considered is an assembly of interlocking osteomorphic blocks. The results of this study demonstrate that the constraining force, which is required to hold the blocks together, can be viewed as a design parameter that governs the bending stiffness and the load bearing capacity of the segmented structure. In the case where the constraining forces are provided laterally using an external frame, the maximum load the assembly can sustain and its stiffness increase linearly with the magnitude of the lateral load applied. Furthermore, we show that the segmented plate with integrated shape memory wires employed as tensioning cables can act as a smart structure that changes its flexural stiffness and load bearing capacity in response to external stimuli, such as heat generated by the switching on and off an electric current.

Etude comparative sur la propagation de l'endommagement apres impact des composites carbone/epoxy renforces par piquage au fil Kevlar et titane-nickel

NASA Astrophysics Data System (ADS)

Vachon, Pierre-Luc

Composite laminates have strong in-plane mechanical properties, but they are generally weaker through their thickness. This specificity makes the laminates prone to delamination, particularly under low-velocity impact loads. Consequently numerous research efforts have been dedicated to developing interlaminar reinforcing methods, such as transverse stitching. The present project proposes the use of the stitching technique combined with a special stitching thread made of superelastic TiNi alloy. This technology is intended to improve the delamination toughness in composite laminates loaded in bending. In the first part of this study a numerical model was developed for analyzing composite structures. The 3-D finite element model was built with the ANSYS commercial software using 20-node solid and 8-node shell elements. The progressive damage modeling technique was used, allowing the prediction of delamination propagation in a laminate submitted to various loading modes. The model was validated for a plate under quasi-static traction load, and it was then used to simulate three-point bending tests. Secondly, carbon/epoxy composite panels were fabricated, with each panel containing unstitched and stitched specimens. Two different materials were used for the stitching thread: superelastic TiNi wires and Kevlar threads as a reference. Some stitched specimens were cut in slices in order to make some observations of the internal stitch using an optical microscope. Standardized low-velocity impact tests and compression after impact tests were carried out on stitched and unstitched specimens (ASTM D7136 and D7137). The Kevlar reinforcements have shown great performance in reducing the delaminated zone after impact, as well as in improving the residual compression strength. The TiNi reinforcements provided encouraging results during the impact tests, though being less effective than the Kevlar threads. During the compression after impact tests, only a slight difference could be measured between the TiNi-stitched and the unstitched specimens. Then the bending performance of the specimens was quantified experimentally by calculating the energy required to create a unit volume of damaged material (Gv, J/mm3). This metric is similar to the Strain Energy Release Rate (SERR) commonly used in studies on delamination. According to the experimental results, the damage resistance in three-point bending was not improved by the Kevlar reinforcements, despite the reduced damaged zone after the impact test. Indeed, when the strain energy in bending is relativized to the induced damaged volume during propagation, it turns out that the TiNi reinforcements are more effective than the Kevlar's for improving the damage resistance. Finally, the numerical study on the behavior of both types of stitched reinforcements allowed identifying subtle differences between those. Indeed, both stitching threads (TiNi and Kevlar) promoted the interlaminar propagation of the delamination during simulation of the bending test, with this behavior being less pronounced for the TiNi-stitched plate. However the Kevlar threads seemed more effective for stopping this propagation in the zones between the stitches. Keywords: composite materials, stitching, numerical model, shape memory alloy, three-point bending, low-velocity impact, ultrasound imaging.

Measurement of Kirchhoff's stress intensity factors in bending plates

NASA Astrophysics Data System (ADS)

Bäcker, D.; Kuna, M.; Häusler, C.

2014-03-01

A measurement method of the stress intensity factors defined by KIRCHHOFF's theory for a crack in a bending plate is shown. For this purpose, a thin piezoelectric polyvinylidene fluoride film (PVDF) is attached to the surface of the cracked plate. The measured electrical voltages are coupled with the load type and the crack tip position relative to the sensor film. Stress intensity factors and the crack tip position can be determined by solving the non-linear inverse problem based on the measured signals. To guarantee solvability of the problem, more measuring electrodes on the film have to be taken in to account. To the developed sensor concept the KIRCHHOFF's plate theory has been applied. In order to connect the electrical signals and the stress intensity factors the stresses near the crack tip have to be written in eigenfunctions (see WILLIAMS [1]). The presented method was verified by means of the example of a straight crack of the length 2a in an infinite isotropic plate under all- side bending. It was found that the positioning of the electrodes is delimited by two radii. On one hand, the measurement points should not be too close to the crack tip. In this area, the Kirchhoff's plate theory cannot be used effectively. On the other hand, the measuring electrodes should be placed at a smaller distance to each other and not too far from the crack tip regarding the convergence radius of the WILLIAMS series expansion. Test calculations on a straight crack in an infinite isotropic plate showed the general applicability of the measurement method.

29 CFR 570.59 - Occupations involved in the operation of power-driven metal forming, punching, and shearing...

Code of Federal Regulations, 2011 CFR

2011-07-01

... beading, straightening, corrugating, flanging, or bending rolls; and hot or cold rolling mills. (ii) All... area between the dies; power presses; and plate punches. (iii) All bending machines, such as apron...

Global Dynamic Modeling of Space-Geodetic Data

NASA Technical Reports Server (NTRS)

Bird, Peter

1995-01-01

The proposal had outlined a year for program conversion, a year for testing and debugging, and two years for numerical experiments. We kept to that schedule. In first (partial) year, author designed a finite element for isostatic thin-shell deformation on a sphere, derived all of its algebraic and stiffness properties, and embedded it in a new finite element code which derives its basic solution strategy (and some critical subroutines) from earlier flat-Earth codes. Also designed and programmed a new fault element to represent faults along plate boundaries. Wrote a preliminary version of a spherical graphics program for the display of output. Tested this new code for accuracy on individual model plates. Made estimates of the computer-time/cost efficiency of the code for whole-earth grids, which were reasonable. Finally, converted an interactive graphical grid-designer program from Cartesian to spherical geometry to permit the beginning of serious modeling. For reasons of cost efficiency, models are isostatic, and do not consider the local effects of unsupported loads or bending stresses. The requirements are: (1) ability to represent rigid rotation on a sphere; (2) ability to represent a spatially uniform strain-rate tensor in the limit of small elements; and (3) continuity of velocity across all element boundaries. Author designed a 3-node triangle shell element which has two different sets of basis functions to represent (vector) velocity and all other (scalar) variables. Such elements can be shown to converge to the formulas for plane triangles in the limit of small size, but can also applied to cover any area smaller than a hemisphere. The difficult volume integrals involved in computing the stiffness of such elements are performed numerically using 7 Gauss integration points on the surface of the sphere, beneath each of which a vertical integral is performed using about 100 points.

Absolute plate motion of Africa around Hawaii-Emperor bend time

NASA Astrophysics Data System (ADS)

Maher, S. M.; Wessel, P.; Müller, R. D.; Williams, S. E.; Harada, Y.

2015-06-01

Numerous regional plate reorganizations and the coeval ages of the Hawaiian Emperor bend (HEB) and Louisville bend of 50-47 Ma have been interpreted as a possible global tectonic plate reorganization at ˜chron 21 (47.9 Ma). Yet for a truly global event we would expect a contemporaneous change in Africa absolute plate motion (APM) reflected by physical evidence distributed on the Africa Plate. This evidence has been postulated to take the form of the Réunion-Mascarene bend which exhibits many HEB-like features, such as a large angular change close to ˜chron 21. However, the Réunion hotspot trail has recently been interpreted as a sequence of continental fragments with incidental hotspot volcanism. Here we show that the alternative Réunion-Mascarene Plateau trail can also satisfy the age progressions and geometry of other hotspot trails on the Africa Plate. The implied motion, suggesting a pivoting of Africa from 67 to 50 Ma, could explain the apparent bifurcation of the Tristan hotspot chain, the age reversals seen along the Walvis Ridge, the sharp curve of the Canary trail, and the diffuse nature of the St. Helena chain. To test this hypothesis further we made a new Africa APM model that extends back to ˜80 Ma using a modified version of the Hybrid Polygonal Finite Rotation Method. This method uses seamount chains and their associated hotspots as geometric constraints for the model, and seamount age dates to determine APM through time. While this model successfully explains many of the volcanic features, it implies an unrealistically fast global lithospheric net rotation, as well as improbable APM trajectories for many other plates, including the Americas, Eurasia and Australia. We contrast this speculative model with a more conventional model in which the Mascarene Plateau is excluded in favour of the Chagos-Laccadive Ridge rotated into the Africa reference frame. This second model implies more realistic net lithospheric rotation and far-field APMs, but fails to explain key details of the Atlantic Ocean volcanic chains. Both models predict a Canary plume influence beneath the Madeiras. Neither model, when projected via the global plate circuit into the Pacific, predicts any significant change in plate motion around chron 21. Consequently, Africa APM models do not appear to provide independent support for a chron 21 global reorganization.

29 CFR 570.59 - Occupations involved in the operations of power-driven metal forming, punching, and shearing...

Code of Federal Regulations, 2010 CFR

2010-07-01

..., or bending rolls; and hot or cold rolling mills. (ii) All pressing or punching machines, such as... presses; and plate punches. (iii) All bending machines, such as apron brakes and press brakes. (iv) All...

Relationship between disc injury and manual lifting: a poroelastic finite element model study.

PubMed

Natarajan, R N; Williams, J R; Lavender, S A; An, H S; Anderson, G B

2008-02-01

Understanding how failure originates in a lumbar motion segment subjected to loading conditions that are representative of manual lifting is important because it will pave the way for a better formulation of the exposure-injury relationship. The aim of the current investigation was to use a poroelastic finite element model of a human lumbar disc to determine its biomechanical characteristics under loading conditions that corresponded to three different, commonly occurring lifting activities and to identify the most hazardous type of loading with regard to damage to the disc. The current study showed that asymmetric lifting may increase the risk of back injury and pain. Lifting that involved lateral bending (asymmetric lifting) of the trunk was found to produce stresses at a localized area in the annulus, annuluar fibres, end plates, and facet joints that were higher than their respective tissue failure strength. Thus asymmetric lifting, if performed over a large number of cycles, might help to propagate this localized failure of the disc tissue to a larger area, owing to fatigue. The analyses also showed that largest fluid exchange between the nucleus and the end plates occurred during asymmetric lifting. If the fluid exchange is restricted owing to end plate calcification or sclerosis of the subchondral bone, high intradiscal pressure might develop, leading to higher disc bulge causing back pain.

Buckling and Post-Buckling Behaviors of a Variable Stiffness Composite Laminated Wing Box Structure

NASA Astrophysics Data System (ADS)

Wang, Peiyan; Huang, Xinting; Wang, Zhongnan; Geng, Xiaoliang; Wang, Yuansheng

2018-04-01

The buckling and post-buckling behaviors of variable stiffness composite laminates (VSCL) with curvilinear fibers were investigated and compared with constant stiffness composite laminates (CSCL) with straight fibers. A VSCL box structure was evaluated under a pure bending moment. The results of the comparative test showed that the critical buckling load of the VSCL box was approximately 3% higher than that of the CSCL box. However, the post-buckling load-bearing capacity was similar due to the layup angle and the immature status of the material processing technology. The properties of the VSCL and CSCL boxes under a pure bending moment were simulated using the Hashin criterion and cohesive interface elements. The simulation results are consistent with the experimental results in stiffness, critical buckling load and failure modes but not in post-buckling load capacity. The results of the experiment, the simulation and laminated plate theory show that VSCL greatly improves the critical buckling load but has little influence on the post-buckling load-bearing capacity.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhang, Zhiqiang; Department of Materials Science and Engineering, University of Wisconsin-Madison, Madison, Wisconsin 53706; Geng, Dalong

A simple and effective decoupled finite element analysis method was developed for simulating both the piezoelectric and flexoelectric effects of zinc oxide (ZnO) and barium titanate (BTO) nanowires (NWs). The piezoelectric potential distribution on a ZnO NW was calculated under three deformation conditions (cantilever, three-point, and four-point bending) and compared to the conventional fully coupled method. The discrepancies of the electric potential maximums from these two methods were found very small, validating the accuracy and effectiveness of the decoupled method. Both ZnO and BTO NWs yielded very similar potential distributions. Comparing the potential distributions induced by the piezoelectric and flexoelectricmore » effects, we identified that the middle segment of a four-point bending NW beam is the ideal place for measuring the flexoelectric coefficient, because the uniform parallel plate capacitor-like potential distribution in this region is exclusively induced by the flexoelectric effect. This decoupled method could provide a valuable guideline for experimental measurements of the piezoelectric effects and flexoelectric effects in the nanometer scale.« less

A Novel Shape Memory Plate Osteosynthesis for Noninvasive Modulation of Fixation Stiffness in a Rabbit Tibia Osteotomy Model

PubMed Central

Müller, Christian W.; Pfeifer, Ronny; Meier, Karen; Decker, Sebastian; Reifenrath, Janin; Gösling, Thomas; Wesling, Volker; Krettek, Christian; Krämer, Manuel

2015-01-01

Nickel-titanium shape memory alloy (NiTi-SMA) implants might allow modulating fracture healing, changing their stiffness through alteration of both elastic modulus and cross-sectional shape by employing the shape memory effect (SME). Hypotheses: a novel NiTi-SMA plate stabilizes tibia osteotomies in rabbits. After noninvasive electromagnetic induction heating the alloy exhibits the SME and the plate changes towards higher stiffness (inverse dynamization) resulting in increased fixation stiffness and equal or better bony healing. In 14 rabbits, 1.0 mm tibia osteotomies were fixed with our experimental plate. Animals were randomised for control or induction heating at three weeks postoperatively. Repetitive X-ray imaging and in vivo measurements of bending stiffness were performed. After sacrifice at 8 weeks, macroscopic evaluation, µCT, and post mortem bending tests of the tibiae were carried out. One death and one early implant dislocation occurred. Following electromagnetic induction heating, radiographic and macroscopic changes of the implant proved successful SME activation. All osteotomies healed. In the treatment group, bending stiffness increased over time. Differences between groups were not significant. In conclusion, we demonstrated successful healing of rabbit tibia osteotomies using our novel NiTi-SMA plate. We demonstrated shape-changing SME in-vivo through transcutaneous electromagnetic induction heating. Thus, future orthopaedic implants could be modified without additional surgery. PMID:26167493

Internal and edge cracks in a plate of finite width under bending

NASA Technical Reports Server (NTRS)

Boduroglu, H.; Erdogan, F.

1983-01-01

In this paper the title problem is studied by using Reissner's transverse shear theory. The main purpose of the paper is to investigate the effect of stress-free boundaries on the stress intensity factors in plates under bending. Among the results found particularly interesting are those relating to the limiting cases of the crack geometries. The numerical results are given for a single internal crack, two collinear cracks, and two edge cracks. Also studied is the effect of Poisson's ratio on the stress intensity factors.

Controlled Bending of a Thin Mirror to Regain Figure after Warping due to Edge-Cutting

NASA Astrophysics Data System (ADS)

Humphries, C. M.

1990-03-01

A thin circular Cer-Vit mirror, diameter 1.3 m, that had been polished flat was cut along 10 edges to form a 12-sided pseudo-elliptical plate. As a result of the edge-cutting, the mirror distorted and an experiment that investigated the effect of reverse stressing to counteract the distortion is described and analysed. The configuration adopted for stressing the mirror when installed as a driven coudé flat in the UK Infrared Telescope is also described. The reverse stressing results can be understood in terms of thin plate theory for pure bending and, in general, if the distortion is toroidal (including the case of a sphere) an orthogonal pair of bending moments can be chosen that will remove the undesired curvatures.

Solving the Problem of Bending of Multiply Connected Plates with Elastic Inclusions

NASA Astrophysics Data System (ADS)

Kaloerov, S. A.; Koshkin, A. A.

2017-11-01

This paper describes a method for determining the strain state of a thin anisotropic plate with elastic arbitrarily arranged elliptical inclusions. Complex potentials are used to reduce the problem to determining functions of generalized complex variables, which, in turn, comes down to an overdetermined system of linear algebraic equations, solved by singular expansions. This paper presents the results of numerical calculations that helped establish the influence of rigidity of elastic inclusions, distances between inclusions, and their geometric characteristics on the bending moments occurring in the plate. It is found that the specific properties of distribution of moments near the apexes of linear elastic inclusions, characterized by moment intensity coefficients, occur only in the case of sufficiently rigid and elastic inclusions.

An exact solution for the history-dependent material and delamination behavior of laminated plates subjected to cylindrical bending

DOE Office of Scientific and Technical Information (OSTI.GOV)

Williams, Todd O

2009-01-01

The exact solution for the history-dependent behavior of laminated plates subjected to cylindrical bending is presented. The solution represents the extension of Pagano's solution to consider arbitrary types of constitutive behaviors for the individual lamina as well as arbitrary types of cohesive zones models for delamination behavior. Examples of the possible types of material behavior are plasticity, viscoelasticity, viscoplasticity, and damaging. Examples of possible CZMs that can be considered are linear, nonlinear hardening, as well as nonlinear with softening. The resulting solution is intended as a benchmark solution for considering the predictive capabilities of different plate theories. Initial results aremore » presented for several types of history-dependent material behaviors. It is shown that the plate response in the presence of history-dependent behaviors can differ dramatically from the elastic response. These results have strong implications for what constitutes an appropriate plate theory for modeling such behaviors.« less

Using Global, Quantitative Models of the Coupled Plates/Mantle System to Understand Late Neogene Dynamics of the Pacific Plate

NASA Astrophysics Data System (ADS)

Stotz, I.; Davies, R.; Iaffaldano, G.

2016-12-01

Knowledge of the evolution of continents, inferred from a variety of geological data, as well as observations of the ocean-floor magnetization pattern provide an increasingly-detailed picture of past and present-day plate motions. These are key to study the evolving balance of shallow- and deep-rooted forces acting upon plates and to unravel the dynamics of the coupled plates/mantle system. Here we focus on the clockwise rotation of the Pacific plate motion relative to the hotspots reference frame between 10 and 5 Ma, which is evidenced by a bend in the Hawaiian sea mount chain (Cox & Engebretson, 1985) as well as by marine magnetic and bathymetric data along the Pacific/Antarctica Ridge (Croon et al., 2008). It has been suggested that such a kinematic change owes to the arrival of the Ontong-Java plateau, the biggest oceanic plateau on the Pacific plate, at the Australia/Pacific subducting margin between 10 and 5 Ma, and to its collision with the Melanesian arc. This could have changed the local buoyancy forces and/or sparked a redistribution of the forces already acting within the Pacific realm, causing the Pacific plate to rotate clockwise. Such hypotheses have never been tested explicitly against the available kinematic reconstructions. We do so by using global numerical models of the coupled plates/mantle system. Our models build on the available codes Terra and Shells. Terra is a global, spherical finite-element code for mantle convection, developed by Baumgardner (1985) and Bunge et al. (1996), and further advanced by Yang (1997; 2000) and Davies et al. (2013), among others. Shells is a thin-sheet, finite-element code for lithosphere dynamics (e.g., Bird, 1998). By merging these two independent models we are able to simulate the rheological behavior of the brittle lithosphere and viscous mantle. We compare the plate velocities output by our models with the available kinematic reconstructions to test the above-mentioned hypotheses, and simulate the impact of the evolving mantle buoyancy-field and plate-boundary forces on the Pacific plate motion. Our approach allows distinguishing between the top-down and bottom-up controls on the recent dynamics of the Pacific plate.

Modeling and experimental analysis of the linear ultrasonic motor with in-plane bending and longitudinal mode.

PubMed

Wan, Zhijian; Hu, Hong

2014-03-01

A novel linear ultrasonic motor based on in-plane longitudinal and bending mode vibration is presented in this paper. The stator of the motor is composed of a metal plate and eight piezoelectric ceramic patches. There are four long holes in the plate, designed for consideration of the longitudinal and bending mode coupling. The corresponding model is developed to optimize the mechanical and electrical coupling of the stator, which causes an ellipse motion at the contact tip of the stator when the composite vibrations with longitudinal and bending are excited. Its harmonic and transient responses are simulated and inspected. A prototype based on the model is fabricated and used to conduct experiments. Results show that the amplitude of the stator's contact tips is significantly increased, which helps to amplify the driving force and speed of the motor. It is therefore feasible to implement effective linear movement using the developed prototype. Copyright © 2013 Elsevier B.V. All rights reserved.

Time dependent response of low velocity impact induced composite conical shells under multiple delamination

NASA Astrophysics Data System (ADS)

Dey, Sudip; Karmakar, Amit

2014-02-01

This paper presents the time dependent response of multiple delaminated angle-ply composite pretwisted conical shells subjected to low velocity normal impact. The finite element formulation is based on Mindlin's theory incorporating rotary inertia and effects of transverse shear deformation. An eight-noded isoparametric plate bending element is employed to satisfy the compatibility of deformation and equilibrium of resultant forces and moments at the delamination crack front. A multipoint constraint algorithm is incorporated which leads to asymmetric stiffness matrices. The modified Hertzian contact law which accounts for permanent indentation is utilized to compute the contact force, and the time dependent equations are solved by Newmark's time integration algorithm. Parametric studies are conducted with respect to triggering parameters like laminate configuration, location of delamination, angle of twist, velocity of impactor, and impactor's displacement for centrally impacted shells.

Derivation of the out-of-plane behaviour of an English bond masonry wall through homogenization strategies

NASA Astrophysics Data System (ADS)

Silva, Luís Carlos; Milani, Gabriele; Lourenço, Paulo B.

2017-11-01

Two finite element homogenized-based strategies are presented for the out-of-plane behaviour characterization of an English bond masonry wall. A finite element micro-modelling approach using Cauchy stresses and first order movements are assumed for both strategies. The material nonlinearity is lumped on joints interfaces and bricks are considered elastic. Nevertheless, the first model is based on a Plane-stress assumption, in which the out-of-plane quantities are derived through on-thickness wall integration considering a Kirchhoff-plate theory. The second model is a tridimensional one, in which the homogenized out-of-plane quantities can be directly derived after solving the boundary value problem. The comparison is conducted by assessing the obtained out-of-plane bending- and torsion-curvature diagrams. A good agreement is found for the present study case.

A square-plate ultrasonic linear motor operating in two orthogonal first bending modes.

PubMed

Chen, Zhijiang; Li, Xiaotian; Chen, Jianguo; Dong, Shuxiang

2013-01-01

A novel square-plate piezoelectric ultrasonic linear motor operated in two orthogonal first bending vibration modes (B₁) is proposed. The piezoelectric vibrator of the linear motor is simply made of a single PZT ceramic plate (sizes: 15 x 15 x 2 mm) and poled in its thickness direction. The top surface electrode of the square ceramic plate was divided into four active areas along its two diagonal lines for exciting two orthogonal B₁ modes. The achieved driving force and speed from the linear motor are 1.8 N and 230 mm/s, respectively, under one pair orthogonal voltage drive of 150 V(p-p) at the resonance frequency of 92 kHz. The proposed linear motor has advantages over conventional ultrasonic linear motors, such as relatively larger driving force, very simple working mode and structure, and low fabrication cost.

New technique for fixing rib fracture with bioabsorbable plate.

PubMed

Oyamatsu, Hironori; Ohata, Norihisa; Narita, Kunio

2016-09-01

Fixation of a bone fracture with a bioabsorbable plate made of poly-L-lactide and hydroxyapatite has received attention. We adopted this technique for a rib fracture by bending the plate into a U-shape and fixing it with suture through the holes in the mesh of the plate and holes that are drilled in the edge of the fractured rib. The suture is also wound around the plate. © The Author(s) 2016.

Biomechanical comparison of straight DCP and helical plates for fixation of transverse and oblique bone fractures.

PubMed

Aksakal, Bunyamin; Gurger, Murat; Say, Yakup; Yilmaz, Erhan

2014-01-01

Biomechanical comparison of straight DCP and helical plates for fixation of transversal and oblique tibial bone fractures were analyzed and compared to each other by axial compression, bending and torsion tests. An in vitro osteosynthesis of transverse (TF) and oblique bone fracture (OF) fixations have been analysed on fresh sheep tibias by using the DCP and helical compression plates (HP). Statistically significant differences were found for both DCP and helical plate fixations under axial compression, bending and torsional loads. The strength of fixation systems was in favor of DC plating with exception of the TF-HP fixation group under compression loads and torsional moments. The transvers fracture (TF) stability was found to be higher than that found in oblique fracture (OF) fixed by helical plates (HP). However, under torsional testing, compared to conventional plating, the helical plate fixations provided a higher torsional resistance and strength. The maximum stiffness at axial compression loading and maximum torsional strength was achieved in torsional testing for the TF-HP fixations. From in vitro biomechanical analysis, fracture type and plate fixation system groups showed different responses under different loadings. Consequently, current biomechanical analyses may encourage the usage of helical HP fixations in near future during clinical practice for transverse bone fractures.

Contemporary crustal deformations in the Izu peninsula, Honshu, Japan and acceleration of plate bending in the northernmost part of the Philippine Sea plate

NASA Astrophysics Data System (ADS)

Fujii, Yoichiro

1991-07-01

Since the beginning of the anomalous vertical crustal movement in the Izu peninsul, Honshu, Japan, many repeated precise levellings have been carried out by the Geographical Survey Institute. Trilaterations covering the entire Izu peninsula have also been carried out by the Geographical Survey Institute. A new technique is developed to adjust the results of levellings, because they had been carried out for different epochs along each levelling route and because of rapid vertical crustal movements. In conventional least-squares adjustment of levelling network, only corrections to the approximate height are assumed to be unknown, while in the present analysis a special model in which rates of vertical deformation at any bench marks are also assumed to be unknown, is adopted. In addition, tidal stations along the coast of the Izu peninsula yield the rate of vertical crustal movement from analysis of tidal data independent of levelling data. We select several special bench marks in which rates of vertical movement are determined by tidal analysis, thereafter special adjustment is applied according to the type of network. The results show that the peninsula is inclined to the south-west. Uplift in the northeastern part of the peninsula is accompanied by remarkable subsidence in the southwest. The rate of contemporary inclination is many times higher than the rate during the period from 1929 to 1972. The deformation is concentrated in the area where Nakamura (1979, 1980) pointed out the bending of the Philippine Sea plate. The mode and rate of the detected crustal deformation suggest the accelerated bending of the peninsula. There are some local “uplift” that deviate from the general pattern of deformation. The most remarkable land uplift was observed near Ito, a city within the peninsula, and the focus of this uplift migrated with time. The accelerated plate bending will produce an extension at the earth's surface and contraction in the deeper part of the subcrustal layer, additionally it triggered the intrusion of magma from the deeper part to the shallower. Moreover, the accelerated plate bending also triggered seismic swarms and destructive, earthquakes in and around the peninsula.

Displacement Theories for In-Flight Deformed Shape Predictions of Aerospace Structures

NASA Technical Reports Server (NTRS)

Ko, William L.; Richards, W. L.; Tran, Van t.

2007-01-01

Displacement theories are developed for a variety of structures with the goal of providing real-time shape predictions for aerospace vehicles during flight. These theories are initially developed for a cantilever beam to predict the deformed shapes of the Helios flying wing. The main structural configuration of the Helios wing is a cantilever wing tubular spar subjected to bending, torsion, and combined bending and torsion loading. The displacement equations that are formulated are expressed in terms of strains measured at multiple sensing stations equally spaced on the surface of the wing spar. Displacement theories for other structures, such as tapered cantilever beams, two-point supported beams, wing boxes, and plates also are developed. The accuracy of the displacement theories is successfully validated by finite-element analysis and classical beam theory using input-strains generated by finite-element analysis. The displacement equations and associated strain-sensing system (such as fiber optic sensors) create a powerful means for in-flight deformation monitoring of aerospace structures. This method serves multiple purposes for structural shape sensing, loads monitoring, and structural health monitoring. Ultimately, the calculated displacement data can be visually displayed to the ground-based pilot or used as input to the control system to actively control the shape of structures during flight.

Simulation Study of Stress and Deformation Behaviour of Debonded Laminated Structure

NASA Astrophysics Data System (ADS)

Hirwani, C. K.; Mittal, H.; Panda, S. K.; Mahapatra, S. S.; Mandal, S. K.; De, A. K.

2017-02-01

The bending strength and deformation characteristics of the debonded laminated plate under the uniformly distributed loading (UDL) have been investigated in this research article. For the simulation study, an internally damaged laminated plate structure model has been developed in ANSYS based on the first-order shear deformable kinematic theory via ANSYS parametric design language (APDL) code. The internal debonding within the laminated structure is incorporated using two sub-laminate approach. Further, the convergence (different mesh densities), as well as the validity (comparing the responses with published results) of the present simulation model, have been performed by solving the deflection responses under the influence of transversely loaded layered structure. Also, to show the coherence of the simulation analysis the results are compared with the experimental bending results of the homemade Glass/Epoxy composite with artificial delamination. For the experimental analysis, Glass/Epoxy laminated composite seeded with delamination at the central mid-plane of the laminate is fabricated using an open mould hand lay-up composites fabrication technique. For the computational purpose, the necessary material properties of fabricated composite plate evaluated experimentally via uniaxial tensile test (Universal Testing Machine INSTRON-1195). Further, the bending (three-point bend test) test is conducted with the help of Universal Testing Machine INSTRON-5967. Finally, the effect different geometrical and material parameters (thickness ratio, modular ratio, constraint conditions) and magnitude of the loading on the static deflection and stress behaviour of the delaminated composite plate are investigated thoroughly by solving different kinds of numerical illustrations and discussed in detail.

P-wave Velocity Structure Across the Mariana Trench and Implications for Hydration

NASA Astrophysics Data System (ADS)

Eimer, M. O.; Wiens, D.; Lizarralde, D.; Cai, C.

2017-12-01

Estimates of the water flux at subduction zones remain uncertain, particularly the amount of water brought into the trench by the subducting plate. Normal faulting related to the bending of the incoming plate has been proposed to provide pathways for water to hydrate the crust and upper mantle. A passive and active source seismic experiment spanning both the incoming plate and forearc was conducted in 2012 in central Mariana to examine the role of hydration at subduction zones. The active-source component of the survey used the R/V M.G. Langsethairgun array and 68 short period sensors, including suspended hydrophones, deployed on 4 transects. This study at the Mariana trench offers a comparison to related studies of incoming plate hydration in Middle America, where differing thermal structures related to plate age predict different stability fields for hydrous minerals. The forearc structure is also of interest, since Mariana is characterized by large serpentine seamounts and may have a serpentinized mantle wedge. The velocity structure will also be important for the relocation of earthquakes in the incoming plate, since the seismicity can offer a constraint for the depth extent of these bending faults. We examine the P-wave velocity structure along a 400-km long wide-angle refraction transect perpendicular to the trench and spanning both the forearc and incoming plate. Preliminary results indicate a velocity reduction in the crust and uppermost mantle at the bending region of the incoming plate, relative to the plate's structure away from the trench. This reduction suggests that outer-rise faults extend into the upper mantle and may have promoted serpentinization of that material. Mantle Pn refraction phases are not observed in the forearc, consistent with the ambient noise tomography results that show upper-mantle velocities similar to that of the lower crust. The lack of contrast between the upper mantle and crustal velocities from the ambient noise has been interpreted to indicate extensive serpentinization of the shallow mantle wedge.

In vitro corrosion of ZEK100 plates in Hank's Balanced Salt Solution

PubMed Central

2012-01-01

Background In recent years magnesium alloys have been intensively investigated as potential resorbable materials with appropriate mechanical and corrosion properties. Particularly in orthopedic research magnesium is interesting because of its mechanical properties close to those of natural bone, the prevention of both stress shielding and removal of the implant after surgery. Methods ZEK100 plates were examined in this in vitro study with Hank's Balanced Salt Solution under physiological conditions with a constant laminar flow rate. After 14, 28 and 42 days of immersion the ZEK100 plates were mechanically tested via four point bending test. The surfaces of the immersed specimens were characterized by SEM, EDX and XRD. Results The four point bending test displayed an increased bending strength after 6 weeks immersion compared to the 2 week group and 4 week group. The characterization of the surface revealed the presence of high amounts of O, P and Ca on the surface and small Mg content. This indicates the precipitation of calcium phosphates with low solubility on the surface of the ZEK100 plates. Conclusions The results of the present in vitro study indicate that ZEK100 is a potential candidate for degradable orthopedic implants. Further investigations are needed to examine the degradation behavior. PMID:22413949

Electrochemical sensor having suspended element counter electrode and deflection method for current sensing

DOEpatents

Thundat, Thomas G.; Brown, Gilbert M.

2010-05-18

An electrochemical suspended element-based sensor system includes a solution cell for holding an electrolyte comprising solution including at least one electrochemically reducible or oxidizable species. A working electrode (WE), reference electrode (RE) and a counter electrode (CE) are disposed in the solution. The CE includes an asymmetric suspended element, wherein one side of the suspended element includes a metal or a highly doped semiconductor surface. The suspended element bends when current associated with reduction or oxidation of the electrochemically reducible or oxidizable species at the WE passes through the suspended element. At least one measurement system measures the bending of the suspended element or a parameter which is a function of the bending.

Increasing dimension of structures by 4D printing shape memory polymers via fused deposition modeling

NASA Astrophysics Data System (ADS)

Hu, G. F.; Damanpack, A. R.; Bodaghi, M.; Liao, W. H.

2017-12-01

The main objective of this paper is to introduce a 4D printing method to program shape memory polymers (SMPs) during fabrication process. Fused deposition modeling (FDM) as a filament-based printing method is employed to program SMPs during depositing the material. This method is implemented to fabricate complicated polymeric structures by self-bending features without need of any post-programming. Experiments are conducted to demonstrate feasibility of one-dimensional (1D)-to 2D and 2D-to-3D self-bending. It is shown that 3D printed plate structures can transform into masonry-inspired 3D curved shell structures by simply heating. Good reliability of SMP programming during printing process is also demonstrated. A 3D macroscopic constitutive model is established to simulate thermo-mechanical features of the printed SMPs. Governing equations are also derived to simulate programming mechanism during printing process and shape change of self-bending structures. In this respect, a finite element formulation is developed considering von-Kármán geometric nonlinearity and solved by implementing iterative Newton-Raphson scheme. The accuracy of the computational approach is checked with experimental results. It is demonstrated that the theoretical model is able to replicate the main characteristics observed in the experiments. This research is likely to advance the state of the art FDM 4D printing, and provide pertinent results and computational tool that are instrumental in design of smart materials and structures with self-bending features.

Lateral Torsional Buckling of Anisotropic Laminated Composite Beams Subjected to Various Loading and Boundary Conditions

NASA Astrophysics Data System (ADS)

Ahmadi, Habiburrahman

Thin-walled structures are major components in many engineering applications. When a thin-walled slender beam is subjected to lateral loads, causing moments, the beam may buckle by a combined lateral bending and twisting of cross-section, which is called lateral-torsional buckling. A generalized analytical approach for lateral-torsional buckling of anisotropic laminated, thin-walled, rectangular cross-section composite beams under various loading conditions (namely, pure bending and concentrated load) and boundary conditions (namely, simply supported and cantilever) was developed using the classical laminated plate theory (CLPT), with all considered assumptions, as a basis for the constitutive equations. Buckling of such type of members has not been addressed in the literature. Closed form buckling expressions were derived in terms of the lateral, torsional and coupling stiffness coefficients of the overall composite. These coefficients were obtained through dimensional reduction by static condensation of the 6x6 constitutive matrix mapped into an effective 2x2 coupled weak axis bending-twisting relationship. The stability of the beam under different geometric and material parameters, like length/height ratio, ply thickness, and ply orientation, was investigated. The analytical formulas were verified against finite element buckling solutions using ABAQUS for different lamination orientations showing excellent accuracy.

Bending behaviors of fully covered biodegradable polydioxanone biliary stent for human body by finite element method.

PubMed

Liu, Yanhui; Zhu, Guoqing; Yang, Huazhe; Wang, Conger; Zhang, Peihua; Han, Guangting

2018-01-01

This paper presents a study of the bending flexibility of fully covered biodegradable polydioxanone biliary stents (FCBPBs) developed for human body. To investigate the relationship between the bending load and structure parameter (monofilament diameter and braid-pin number), biodegradable polydioxanone biliary stents derived from braiding method were covered with membrane prepared via electrospinning method, and nine FCBPBSs were then obtained for bending test to evaluate the bending flexibility. In addition, by the finite element method, nine numerical models based on actual biliary stent were established and the bending load was calculated through the finite element method. Results demonstrate that the simulation and experimental results are in good agreement with each other, indicating that the simulation results can be provided a useful reference to the investigation of biliary stents. Furthermore, the stress distribution on FCBPBSs was studied, and the plastic dissipation analysis and plastic strain of FCBPBSs were obtained via the bending simulation. Copyright © 2017 Elsevier Ltd. All rights reserved.

Automatic locking orthotic knee device

NASA Technical Reports Server (NTRS)

Weddendorf, Bruce C. (Inventor)

1993-01-01

An articulated tang in clevis joint for incorporation in newly manufactured conventional strap-on orthotic knee devices or for replacing such joints in conventional strap-on orthotic knee devices is discussed. The instant tang in clevis joint allows the user the freedom to extend and bend the knee normally when no load (weight) is applied to the knee and to automatically lock the knee when the user transfers weight to the knee, thus preventing a damaged knee from bending uncontrollably when weight is applied to the knee. The tang in clevis joint of the present invention includes first and second clevis plates, a tang assembly and a spacer plate secured between the clevis plates. Each clevis plate includes a bevelled serrated upper section. A bevelled shoe is secured to the tank in close proximity to the bevelled serrated upper section of the clevis plates. A coiled spring mounted within an oblong bore of the tang normally urges the shoes secured to the tang out of engagement with the serrated upper section of each clevic plate to allow rotation of the tang relative to the clevis plate. When weight is applied to the joint, the load compresses the coiled spring, the serrations on each clevis plate dig into the bevelled shoes secured to the tang to prevent relative movement between the tang and clevis plates. A shoulder is provided on the tang and the spacer plate to prevent overextension of the joint.

46 CFR 32.59-1 - Minimum section modulus and plating thickness requirements-TB/ALL.

Code of Federal Regulations, 2013 CFR

2013-10-01

... of that which is necessary to meet the bending moment developed under a full load condition in still water, using a permissible bending stress of 12.74 kN/cm2 (1.30 t/cm2, 8.25 Ltf/in2). (d) Within the 40...

46 CFR 32.59-1 - Minimum section modulus and plating thickness requirements-TB/ALL.

Code of Federal Regulations, 2012 CFR

2012-10-01

... of that which is necessary to meet the bending moment developed under a full load condition in still water, using a permissible bending stress of 12.74 kN/cm2 (1.30 t/cm2, 8.25 Ltf/in2). (d) Within the 40...

46 CFR 32.59-1 - Minimum section modulus and plating thickness requirements-TB/ALL.

Code of Federal Regulations, 2011 CFR

2011-10-01

... of that which is necessary to meet the bending moment developed under a full load condition in still water, using a permissible bending stress of 12.74 kN/cm2 (1.30 t/cm2, 8.25 Ltf/in2). (d) Within the 40...

46 CFR 32.59-1 - Minimum section modulus and plating thickness requirements-TB/ALL.

Code of Federal Regulations, 2010 CFR

2010-10-01

... of that which is necessary to meet the bending moment developed under a full load condition in still water, using a permissible bending stress of 12.74 kN/cm2 (1.30 t/cm2, 8.25 Ltf/in2). (d) Within the 40...

46 CFR 32.59-1 - Minimum section modulus and plating thickness requirements-TB/ALL.

Code of Federal Regulations, 2014 CFR

2014-10-01

... of that which is necessary to meet the bending moment developed under a full load condition in still water, using a permissible bending stress of 12.74 kN/cm2 (1.30 t/cm2, 8.25 Ltf/in2). (d) Within the 40...

Optimization of a Simple Ship Structural Model Using MAESTRO

DTIC Science & Technology

1999-03-01

Substructures MAESTRO Model Modules . . . MAESTRO Model Girders . . . . MAESTRO Model Tranverse Frames 9 10 11 12 13 Structural and Non-Structural...Weight Distribution 14 Longitudinal Load Distribution on the Model . 15 Tranverse Load Distribution on the Model . . . 16 Hogging Displacement of...Compression, Flange PYCP Panel Yield - Compression, Plate PSPBT Panel Serviceability- Plate Bending Tranverse PSPBL Panel Serviceability - Plate

Vortex Flows in the Liquid Layer and Droplets on a Vibrating Flexible Plate

NASA Astrophysics Data System (ADS)

Aleksandrov, Vladimir; Kopysov, Sergey; Tonkov, Leonid

2018-02-01

In certain conditions, in the layers and droplets of a liquid on a vibrating rectangular flexible plate, vortex flows are formed simultaneously with the excitation of capillary oscillations on the free surface of the liquid layers and droplets. Capillary oscillations in the form of two-dimensional standing waves form Faraday ripples on the free surface of the liquid layer. On the surface of the vibrating droplets, at the excitation of capillary oscillations a light spot reflected from a spotlight source moves along a trajectory in the form of a Lissajous figure observed with a microscope. When vortex flows visualized with graphite microparticles appear in the layer and droplets of a transparent liquid, the trajectory of the light spot on the layer and droplet surface is a two-dimensional trajectory in the form of an ellipse or a saddle. This indicates that the generation of the vortex flows in a liquid at vibrations is due to capillary oscillations in the orthogonally related directions. In the liquid layer and droplets on the surface of the flexible plate, the vibrations of which are generated by bending vibrations, the vortex flows appear due to the plate vibrations and the capillary oscillations of the surface of a layer or a droplet of the liquid. On the free surface of the liquid, the capillary waves, which are parametrically excited by the plate bending vibrations, are additionally modulated by the same bending vibrations in the transverse direction.

Failure prediction of thin beryllium sheets used in spacecraft structures

NASA Technical Reports Server (NTRS)

Roschke, Paul N.; Mascorro, Edward; Papados, Photios; Serna, Oscar R.

1991-01-01

The primary objective of this study is to develop a method for prediction of failure of thin beryllium sheets that undergo complex states of stress. Major components of the research include experimental evaluation of strength parameters for cross-rolled beryllium sheet, application of the Tsai-Wu failure criterion to plate bending problems, development of a high order failure criterion, application of the new criterion to a variety of structures, and incorporation of both failure criteria into a finite element code. A Tsai-Wu failure model for SR-200 sheet material is developed from available tensile data, experiments carried out by NASA on two circular plates, and compression and off-axis experiments performed in this study. The failure surface obtained from the resulting criterion forms an ellipsoid. By supplementing experimental data used in the the two-dimensional criterion and modifying previously suggested failure criteria, a multi-dimensional failure surface is proposed for thin beryllium structures. The new criterion for orthotropic material is represented by a failure surface in six-dimensional stress space. In order to determine coefficients of the governing equation, a number of uniaxial, biaxial, and triaxial experiments are required. Details of these experiments and a complementary ultrasonic investigation are described in detail. Finally, validity of the criterion and newly determined mechanical properties is established through experiments on structures composed of SR200 sheet material. These experiments include a plate-plug arrangement under a complex state of stress and a series of plates with an out-of-plane central point load. Both criteria have been incorporated into a general purpose finite element analysis code. Numerical simulation incrementally applied loads to a structural component that is being designed and checks each nodal point in the model for exceedance of a failure criterion. If stresses at all locations do not exceed the failure criterion, the load is increased and the process is repeated. Failure results for the plate-plug and clamped plate tests are accurate to within 2 percent.

Efficient swimming of a plunging elastic plate in a viscous fluid

NASA Astrophysics Data System (ADS)

Yeh, Peter; Alexeev, Alexander

2014-03-01

We use three dimensional computer simulations to examine the combined hydrodynamics and structural response of a plunging elastic plate submerged in a viscous fluid with Reynolds number of 250. The plate is actuated at the root with a prescribed vertical sinusoidal displacement and a zero slope (clamped) boundary condition. We explore the steady state swimming velocity and the associated input power as a function of driving frequency, added mass, and aspect ratio. We find a universal bending pattern independent of geometry and added mass that maximizes the distance traveled per unit applied work. This bending pattern is associated with minimizing center of mass oscillations normal to the direction of travel. Subsequently, the flow around the sides of the swimmer, which does not aid in propulsion, is minimized, thereby reducing viscous losses.

A high-accuracy optical linear algebra processor for finite element applications

NASA Technical Reports Server (NTRS)

Casasent, D.; Taylor, B. K.

1984-01-01

Optical linear processors are computationally efficient computers for solving matrix-matrix and matrix-vector oriented problems. Optical system errors limit their dynamic range to 30-40 dB, which limits their accuray to 9-12 bits. Large problems, such as the finite element problem in structural mechanics (with tens or hundreds of thousands of variables) which can exploit the speed of optical processors, require the 32 bit accuracy obtainable from digital machines. To obtain this required 32 bit accuracy with an optical processor, the data can be digitally encoded, thereby reducing the dynamic range requirements of the optical system (i.e., decreasing the effect of optical errors on the data) while providing increased accuracy. This report describes a new digitally encoded optical linear algebra processor architecture for solving finite element and banded matrix-vector problems. A linear static plate bending case study is described which quantities the processor requirements. Multiplication by digital convolution is explained, and the digitally encoded optical processor architecture is advanced.

Biomechanics of lateral lumbar interbody fusion constructs with lateral and posterior plate fixation: laboratory investigation.

PubMed

Fogel, Guy R; Parikh, Rachit D; Ryu, Stephen I; Turner, Alexander W L

2014-03-01

Lumbar interbody fusion is indicated in the treatment of degenerative conditions. Laterally inserted interbody cages significantly decrease range of motion (ROM) compared with other cages. Supplemental fixation options such as lateral plates or spinous process plates have been shown to provide stability and to reduce morbidity. The authors of the current study investigate the in vitro stability of the interbody cage with a combination of lateral and spinous process plate fixation and compare this method to the established bilateral pedicle screw fixation technique. Ten L1-5 specimens were evaluated using multidirectional nondestructive moments (± 7.5 N · m), with a custom 6 degrees-of-freedom spine simulator. Intervertebral motions (ROM) were measured optoelectronically. Each spine was evaluated under the following conditions at the L3-4 level: intact; interbody cage alone (stand-alone); cage supplemented with lateral plate; cage supplemented with ipsilateral pedicle screws; cage supplemented with bilateral pedicle screws; cage supplemented with spinous process plate; and cage supplemented with a combination of lateral plate and spinous process plate. Intervertebral rotations were calculated, and ROM data were normalized to the intact ROM data. The stand-alone laterally inserted interbody cage significantly reduced ROM with respect to the intact state in flexion-extension (31.6% intact ROM, p < 0.001), lateral bending (32.5%, p < 0.001), and axial rotation (69.4%, p = 0.002). Compared with the stand-alone condition, addition of a lateral plate to the interbody cage did not significantly alter the ROM in flexion-extension (p = 0.904); however, it was significantly decreased in lateral bending and axial rotation (p < 0.001). The cage supplemented with a lateral plate was not statistically different from bilateral pedicle screws in lateral bending (p = 0.579). Supplemental fixation using a spinous process plate was not significantly different from bilateral pedicle screws in flexion-extension (p = 0.476). The combination of lateral plate and spinous process plate was not statistically different from the cage supplemented with bilateral pedicle screws in all the loading modes (p ≥ 0.365). A combination of lateral and spinous process plate fixation to supplement a laterally inserted interbody cage helps achieve rigidity in all motion planes similar to that achieved with bilateral pedicle screws.

Four-plate piezoelectric actuator driving a large-diameter special optical fiber for nonlinear optical microendoscopy.

PubMed

Wang, Ying; Li, Zhi; Liang, Xiaobao; Fu, Ling

2016-08-22

In nonlinear optical microendoscope (NOME), a fiber with excellent optical characteristics and a miniature scanning mechanism at the distal end are two key components. Double-clad fibers (DCFs) and double-clad photonic crystal fibers (DCPCFs) have shown great optical characteristics but limited vibration amplitude due to large diameter. Besides reducing the damping of fiber cantilever, optimizing the structural of the actuator for lower energy dissipation also contributes to better driving capability. This paper presented an optimized actuator for driving a particular fiber cantilever in the view point of energy. Firstly, deformation energy of a bending fiber cantilever operating in resonant mode is investigated. Secondly, strain and stress analyses revealed that the four-plate actuator achieved lower energy dissipation. Then, finite-element simulations showed that the large-diameter fiber yielded an adequate vibration amplitude driven by a four-plate actuator, which was confirmed by experiments of our home-made four-plate actuator prototypes. Additionally, a NOME based on a DCPCF with a diameter of 350 μm driven by four-plate piezoelectric actuator has been developed. The NOME can excite and collect intrinsic second-harmonic and two-photon fluorescence signals with the excitation power of 10-30 mW and an adequate field of view of 200 μm, which suggest great potential applications in neuroscience and clinical diagnoses.

Mathematical model of the two-point bending test for strength measurement of optical fibers

NASA Astrophysics Data System (ADS)

Srubshchik, Leonid S.

1999-12-01

The mathematical and numerical analysis of two nonlinear problems of solid mechanics related to the breaking strength of coated optical glass fibers are presented. Both of these problems are concerned with the two-point bending technique which measures the strength of optical fibers by straining them in a bending mode between two parallel plates. The plates are squeezed together until the fiber fractures. The process gives a measurement of fiber strength. The present theory of this test is based on the elastica theory of an unshearable and inextensible rod. However, within the limits of the elastics theory the tensile and shear stresses cannot be determined. In this paper we study the behavior of optical glass fiber on the base of a geometrically exact nonlinear Cosserat theory in which a rod can suffer flexure, extension, and shear. We adopt the specific nonlinear stress-strain relations in silica and titania-doped silica glass fibers and show that it does not yield essential changes in the results as compared with the results for the linear stress-strain relations. We obtain the governing equations of the motion of the fiber in the two-point bending test taking into account the friction between the test fiber and the rigid plates. We develop the computational methods to solve the initial and equilibrium free-boundary nonlinear planar problems. We derive formulas for tensile and shear stresses which allow us to calculate tension in the fiber. The numerical results show that frictional forces play an important role. The interaction of optical fiber and rigid plates is treated by means of the classical contact theory.

The Panama North Andes Plate Bounday Zone from Interpreted Radar Images, Geologic Mapping and Geophysical Anomalies

NASA Astrophysics Data System (ADS)

Hernandez, O.; Alexander, G. C.; Garzon, F.

2013-05-01

Satellite geodetics shows the existence of the rigid Panama microplate converging on west to east with The North Andean block. Seismic studies indicate that this plate boundary zone has compressive east-west stresses. Interpretation from magnetic and gravity data suggest that the thickness of the sedimentary sequence of The Atrato basin, reaches 10.5 km and that the Mande magmatic arc is a tectonic pillar, bounded by faults. The interpretation of seismic lines shows the basement of the Urabá Basin is affected by normal faults that limit blocks sunk and raised, a sedimentary sequence that is wedged against the Mande magmatic arc and becomes thicker towards the east. It also shows a thrust fault that connects Neogene sediments of Sinu fold belt with the Urabá Basin. The collision of the Panama arc with the Western Cordillera leads to the existence of a low-angle subduction zone inclined to the east involving the partition of the oceanic plate, drawing up of a trench and subducting plate bending. Before the Panama arc collision with the Western Cordillera, granitic intrusion had occurred that gave rise to the Mande magmatic arc, causing bending and rise of the oceanic crust. This effort generated tensional bending at the top of the crust that led to the formation of raised and sunken blocks bounded by normal faults, within which lies the tectonic pillar which forms the Mande magmatic arc. Upon the occurrence of the collision, it was launched the end of the connection between the Pacific Ocean and Caribbean Sea and the formation of the Uraba forearc basins and the Atrato basin. Panama - North Andes Plate boundary Zone 2d Modeling of the Panama - North Andes Plate Bounday Zone

Biomechanics of a Fixed–Center of Rotation Cervical Intervertebral Disc Prosthesis

PubMed Central

Crawford, Neil R.; Baek, Seungwon; Sawa, Anna G.U.; Safavi-Abbasi, Sam; Sonntag, Volker K.H.; Duggal, Neil

2012-01-01

Background Past in vitro experiments studying artificial discs have focused on range of motion. It is also important to understand how artificial discs affect other biomechanical parameters, especially alterations to kinematics. The purpose of this in vitro investigation was to quantify how disc replacement with a ball-and-socket disc arthroplasty device (ProDisc-C; Synthes, West Chester, Pennsylvania) alters biomechanics of the spine relative to the normal condition (positive control) and simulated fusion (negative control). Methods Specimens were tested in multiple planes by use of pure moments under load control and again in displacement control during flexion-extension with a constant 70-N compressive follower load. Optical markers measured 3-dimensional vertebral motion, and a strain gauge array measured C4-5 facet loads. Results Range of motion and lax zone after disc replacement were not significantly different from normal values except during lateral bending, whereas plating significantly reduced motion in all loading modes (P < .002). Plating but not disc replacement shifted the location of the axis of rotation anteriorly relative to the intact condition (P < 0.01). Coupled axial rotation per degree of lateral bending was 25% ± 48% greater than normal after artificial disc replacement (P = .05) but 37% ± 38% less than normal after plating (P = .002). Coupled lateral bending per degree of axial rotation was 37% ± 21% less than normal after disc replacement (P < .001) and 41% ± 36% less than normal after plating (P = .001). Facet loads did not change significantly relative to normal after anterior plating or arthroplasty, except that facet loads were decreased during flexion in both conditions (P < .03). Conclusions In all parameters studied, deviations from normal biomechanics were less substantial after artificial disc placement than after anterior plating. PMID:25694869

A biomechanical comparison of conventional dynamic compression plates and string-of-pearls™ locking plates using cantilever bending in a canine Ilial fracture model.

PubMed

Kenzig, Allison R; Butler, James R; Priddy, Lauren B; Lacy, Kristen R; Elder, Steven H

2017-07-13

Fracture of the ilium is common orthopedic injury that often requires surgical stabilization in canine patients. Of the various methods of surgical stabilization available, application of a lateral bone plate to the ilium is the most common method of fixation. Many plating options are available, each having its own advantages and disadvantages. The purpose of this study was to evaluate the biomechanical properties of a 3.5 mm String-of-Pearls™ plate and a 3.5 mm dynamic compression plate in a cadaveric canine ilial fracture model. Hemipelves were tested in cantilever bending to failure and construct stiffness, yield load, displacement at yield, ultimate load, and mode of failure were compared. The mean stiffness of dynamic compression plate (116 ± 47 N/mm) and String-of-Pearls™ plate (107 ± 18 N/mm) constructs, mean yield load of dynamic compression plate (793 ± 333 N) and String-of-Pearls™ plate (860 ± 207 N) constructs, mean displacement at yield of dynamic compression plate (8.6 ± 3.0 mm) and String-of-Pearls™ plate (10.2 ± 2.8 mm) constructs, and ultimate load at failure of dynamic compression plate (936 ± 320 N) and String-of-Pearls™ plate (939 ± 191 N) constructs were not significantly different. No differences were found between constructs with respect to mode of failure. No significant biomechanical differences were found between String-of-Pearls™ plate and dynamic compression plate constructs in this simplified cadaveric canine ilial fracture model.

The structural behavior of a graphite-polymide honeycomb sandwich panel with quasi-isotropic face sheets and an orthotropic core

NASA Technical Reports Server (NTRS)

Hyer, M. W.; Hagaman, J. A.

1979-01-01

The results of a series of tests of graphite-polyimide honeycomb sandwich panels are presented. The panels were 1.22 m long, 0.508 m wide, and approximately 13.3 m thick. The face sheets were a T-300/PMR-15 fabric in a quasi-isotropic layup and were 0.279 mm thick. The core was Hexcel HRH 327-3/16 - 4.0 glass reinforced polyimide honeycomb, 12.7 mm thick. Three panels were used in the test: one was cut into smaller pieces for testing as beam, compression, and shear specimens; a second panel was used for plate bending tests; the third panel was used for in-plane stability tests. Presented are the experimental results of four point bending tests, short block compression tests, core transverse shear modulus, three point bending tests, vibration tests, plate bending tests, and panel stability tests. The results of the first three tests are used to predict the results of some of the other tests. The predictions and experimental results are compared, and the agreement is quite good.

Finite element analysis on the bending condition of truck frame before and after opening

NASA Astrophysics Data System (ADS)

Cai, Kaiwu; Cheng, Wei; Lu, Jifu

2018-05-01

Based on the design parameters of a truck frame, the structure design and model of the truck frame are built. Based on the finite element theory, the load, the type of fatigue and the material parameters of the frame are combined with the semi-trailer. Using finite element analysis software, after a truck frame hole in bending condition for the finite element analysis of comparison, through the analysis found that the truck frame hole under bending condition can meet the strength requirements are very helpful for improving the design of the truck frame.

Comparison of the Mechanical Characteristics of a Universal Small Biplane Plating Technique Without Compression Screw and Single Anatomic Plate With Compression Screw.

PubMed

Dayton, Paul; Ferguson, Joe; Hatch, Daniel; Santrock, Robert; Scanlan, Sean; Smith, Bret

2016-01-01

To better understand the mechanical characteristics of biplane locked plating in small bone fixation, the present study compared the stability under cyclic cantilever loading of a 2-plate locked biplane (BPP) construct without interfragmentary compression with that of a single-plate locked construct with an additional interfragmentary screw (SPS) using surrogate bone models simulating Lapidus arthrodesis. In static ultimate plantar bending, the BPP construct failed at significantly greater load than did the SPS construct (556.2 ± 37.1 N versus 241.6 ± 6.3 N, p = .007). For cyclic failure testing in plantar bending at a 180-N starting load, the BPP construct failed at a significantly greater number of cycles (158,322 ± 50,609 versus 13,718 ± 10,471 cycles) and failure load (242.5 ± 25.0 N versus 180.0 ± 0.0 N) than the SPS construct (p = .002). For cyclic failure testing in plantar bending at a 120-N starting load, the results were not significantly different between the BPP and SPS constructs for the number of cycles (207,646 ± 45,253 versus 159,334 ± 69,430) or failure load (205.0 ± 22.4 N versus 185.0 ± 33.5 N; p = .300). For cyclic testing with 90° offset loading (i.e., medial to lateral bending) at a 120-N starting load, all 5 BPP constructs (tension side) and 2 of the 5 SPS constructs reached 250,000 cycles without failure. Overall, the present study found the BPP construct to have superior or equivalent stability in multiplanar orientations of force application in both static and fatigue testing. Thus, the concept of biplane locked plating, using 2 low profile plates and unicortical screw insertion, shows promise in small bone fixation, because it provides consistent stability in multiplanar orientations, making it universally adaptable to many clinical situations. Copyright © 2016 American College of Foot and Ankle Surgeons. Published by Elsevier Inc. All rights reserved.

Control of Fan Blade Vibrations Using Piezoelectrics and Bi-Directional Telemetry

NASA Technical Reports Server (NTRS)

Provenza, Andrew J.; Morrison, Carlos R.

2011-01-01

A novel wireless device which transfers supply power through induction to rotating operational amplifiers and transmits low voltage AC signals to and from a rotating body by way of radio telemetry has been successfully demonstrated in the NASA Glenn Research Center (GRC) Dynamic Spin Test Facility. In the demonstration described herein, a rotating operational amplifier provides controllable AC power to a piezoelectric patch epoxied to the surface of a rotating Ti plate. The amplitude and phase of the sinusoidal voltage command signal, transmitted wirelessly to the amplifier, was tuned to completely suppress the 3rd bending resonant vibration of the plate. The plate's 3rd bending resonance was excited using rotating magnetic bearing excitation while it spun at slow speed in a vacuum chamber. A second patch on the opposite side of the plate was used as a sensor. This paper discusses the characteristics of this novel device, the details of a spin test, results from a preliminary demonstration, and future plans.

Controlling coupled bending-twisting vibrations of anisotropic composite wing

NASA Astrophysics Data System (ADS)

Ryabov, Victor; Yartsev, Boris

2018-05-01

The paper discusses the possibility to control coupled bending-twisting vibrations of anisotropic composite wing by means of the monoclinic structures in the reinforcement of the plating. Decomposing the potential straining energy and kinetic energy of natural vibration modes into interacting and non-interacting parts, it became possible to introduce the two coefficients that integrally consider the effect of geometry and reinforcement structure upon the dynamic response parameters of the wing. The first of these coefficients describes the elastic coupling of the natural vibration modes, the second coefficient describes the inertial one. The paper describes the numerical studies showing how the orientation of considerably anisotropic CRP layers in the plating affects natural frequencies, loss factors, coefficients of elastic and inertial coupling for several lower tones of natural bending-twisting vibrations of the wing. Besides, for each vibration mode, partial values of the above mentioned dynamic response parameters were determined by means of the relationships for orthotropic structures where instead of "free" shearing modulus in the reinforcement plant, "pure" shearing modulus is used. Joint analysis of the obtained results has shown that each pair of bending-twisting vibration modes has its orientation angle ranges of the reinforcing layers where the inertial coupling caused by asymmetry of the cross-section profile with respect to the main axes of inertia decreases, down to the complete extinction, due to the generation of the elastic coupling in the plating material. These ranges are characterized by the two main features: 1) the difference in the natural frequencies of the investigated pair of bending-twisting vibration modes is the minimum and 2) natural frequencies of bending-twisting vibrations belong to a stretch restricted by corresponding partial natural frequencies of the investigated pair of vibration modes. This result is of practical importance because it enables approximate analysis of real composite wings with complex geometry in the existing commercial software packages.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ice, G.E.; Barbee, T.; Bionta, R.

The increasing availability of synchrotron x-ray sources has stimulated the development of advanced hard x-ray (E{>=}5 keV) microprobes. New x-ray optics have been demonstrated which show promise for achieving intense submicron hard x-ray probes. These probes will be used for extraordinary elemental detection by x-ray fluorescence/absorption and for microdiffraction to identify phase and strain. The inherent elemental and crystallographic sensitivity of an x-ray microprobe and its inherently nondestructive and penetrating nature makes the development of an advanced hard x-ray microprobe an important national goal. In this workshop state-of-the-art hard x-ray microprobe optics were described and future directions were discussed. Genemore » Ice, Oak Ridge National Laboratory (ORNL), presented an overview of the current status of hard x-ray microprobe optics and described the use of crystal spectrometers to improve minimum detectable limits in fluorescent microprobe experiments. Al Thompson, Lawrence Berkeley Laboratory (LBL), described work at the Center for X-ray Optics to develop a hard x-ray microprobe based on Kirkpatrick-Baez (KB) optics. Al Thompson also showed the results of some experimental measurements with their KB optics. Malcolm Howells presented a method for bending elliptical mirrors and Troy Barbee commented on the use of graded d spacings to achieve highest efficiency in KB multilayer microfocusing. Richard Bionta, Lawrence Livermore National Laboratory (LLNL), described the development of the first hard x-ray zone plates and future promise of so called {open_quotes}jelly roll{close_quotes} or sputter slice zone plates. Wenbing Yun, Argonne National Laboratory (ANL), described characterization of jelly roll and lithographically produced zone plates and described the application of zone plates to focus extremely narrow bandwidths by nuclear resonance. This report summarizes the presentations of the workshop subgroup on hard x-ray microprobes.« less

Biomechanical comparison of anterior cervical plating and combined anterior/lateral mass plating.

PubMed

Adams, M S; Crawford, N R; Chamberlain, R H; Bse; Sonntag, V K; Dickman, C A

2001-01-01

Previous studies showed anterior plates of older design to be inadequate for stabilizing the cervical spine in all loading directions. No studies have investigated enhancement in stability obtained by combining anterior and posterior plates. To determine which modes of loading are stabilized by anterior plating after a cervical burst fracture and to determine whether adding posterior plating further significantly stabilizes the construct. A repeated-measures in vitro biomechanical flexibility experiment was performed to investigate how surgical destabilization and subsequent addition of hardware components alter spinal stability. Six human cadaveric specimens were studied. Angular range of motion (ROM) and neutral zone (NZ) were quantified during flexion, extension, lateral bending, and axial rotation. Nonconstraining, nondestructive torques were applied while recording three-dimensional motion optoelectronically. Specimens were tested intact, destabilized by simulated burst fracture with posterior distraction, plated anteriorly with a unicortical locking system, and plated with a combined anterior/posterior construct. The anterior plate significantly (p<.05) reduced the ROM relative to normal in all modes of loading and significantly reduced the NZ in flexion and extension. Addition of the posterior plates further significantly reduced the ROM in all modes of loading and reduced the NZ in lateral bending. Anterior plating systems are capable of substantially stabilizing the cervical spine in all modes of loading after a burst fracture. The combined approach adds significant stability over anterior plating alone in treating this injury but may be unnecessary clinically. Further study is needed to assess the added clinical benefits of the combined approach and associated risks.

Chondron curvature mapping in growth plate cartilage under compressive loading.

PubMed

Vendra, Bhavya B; Roan, Esra; Williams, John L

2018-05-18

The physis, or growth plate, is a layer of cartilage responsible for long bone growth. It is organized into reserve, proliferative and hypertrophic zones. Unlike the reserve zone where chondrocytes are randomly arranged, either singly or in pairs, the proliferative and hypertrophic chondrocytes are arranged within tubular structures called chondrons. In previous studies, the strain patterns within the compressed growth plate have been reported to be nonuniform and inhomogeneous, with an apparent random pattern in compressive strains and a localized appearance of tensile strains. In this study we measured structural deformations along the entire lengths of chondrons when the physis was subjected to physiological (20%) and hyper-physiological (30% and 40%) levels of compression. This provided a means to interpret the apparent random strain patterns seen in texture correlation maps in terms of bending deformations of chondron structures and provided a physical explanation for the inhomogeneous and nonuniform strain patterns reported in previous studies. We observed relatively large bending deformations (kinking) of the chondron structures at the interface of the reserve and proliferative zones during compression. Bending in this region may induce dividing cells to align longitudinally to maintain column formation and drive longitudinal growth. Copyright © 2018 Elsevier Ltd. All rights reserved.

Development of technology for modeling of a 1/8-scale dynamic model of the shuttle Solid Rocket Booster (SRB)

NASA Technical Reports Server (NTRS)

Levy, A.; Zalesak, J.; Bernstein, M.; Mason, P. W.

1974-01-01

A NASTRAN analysis of the solid rocket booster (SRB) substructure of the space shuttle 1/8-scale structural dynamics model. The NASTRAN finite element modeling capability was first used to formulate a model of a cylinder 10 in. radius by a 200 in. length to investigate the accuracy and adequacy of the proposed grid point spacing. Results were compared with a shell analysis and demonstrated relatively accurate results for NASTRAN for the lower modes, which were of primary interest. A finite element model of the full SRB was then formed using CQUAD2 plate elements containing membrane and bending stiffness and CBAR offset bar elements to represent the longerons and frames. Three layers of three-dimensional CHEXAI elements were used to model the propellant. This model, consisting of 4000 degrees of freedom (DOF) initially, was reduced to 176 DOF using Guyan reduction. The model was then submitted for complex Eigenvalue analysis. After experiencing considerable difficulty with attempts to run the complete model, it was split into two substructres. These were run separately and combined into a single 116 degree of freedom A set which was successfully run. Results are reported.

Nonlinear fracture of concrete and ceramics

NASA Technical Reports Server (NTRS)

Kobayashi, Albert S.; Du, Jia-Ji; Hawkins, Niel M.; Bradt, Richard C.

1989-01-01

The nonlinear fracture process zones in an impacted unnotched concrete bend specimen, a prenotched ceramic bend specimen, and an unnotched ceramic/ceramic composite bend specimen were estimated through hybrid experimental numerical analysis. Aggregate bridging in concrete, particulate bridging in ceramics, and fiber bridging in ceramic/ceramic composite are modeled by Barenblatt-type cohesive zones which are incorporated into the finite-element models of the bend specimens. Both generation and propagation analyses are used to estimate the distribution of crack closure stresses in the nonlinear fracture process zones. The finite-element models are then used to simulate fracture tests consisting of rapid crack propagation in an impacted concrete bend specimen, and stable crack growth and strain softening in a ceramic and ceramic/ceramic composite bend specimens.

Reinforced Masks for Ion Plating of Solar Cells

NASA Technical Reports Server (NTRS)

Conley, W. R.; Swick, E. G.; Volkers, J. C.

1987-01-01

Proposed mask for ion plating of surface electrodes on silicon solar cells reinforced to hold shape better during handling. Fabrication process for improved mask similar to conventional mask. Additional cuts and bends made in wide diametral strip to form bridges between pairs of mask fingers facing each other across this strip. Bridges high enough not to act as masks so entire strip area plated.

Nonlinear Analysis of Bonded Composite Single-LAP Joints

NASA Technical Reports Server (NTRS)

Oterkus, E.; Barut, A.; Madenci, E.; Smeltzer, S. S.; Ambur, D. R.

2004-01-01

This study presents a semi-analytical solution method to analyze the geometrically nonlinear response of bonded composite single-lap joints with tapered adherend edges under uniaxial tension. The solution method provides the transverse shear and normal stresses in the adhesive and in-plane stress resultants and bending moments in the adherends. The method utilizes the principle of virtual work in conjunction with von Karman s nonlinear plate theory to model the adherends and the shear lag model to represent the kinematics of the thin adhesive layer between the adherends. Furthermore, the method accounts for the bilinear elastic material behavior of the adhesive while maintaining a linear stress-strain relationship in the adherends. In order to account for the stiffness changes due to thickness variation of the adherends along the tapered edges, their in-plane and bending stiffness matrices are varied as a function of thickness along the tapered region. The combination of these complexities results in a system of nonlinear governing equilibrium equations. This approach represents a computationally efficient alternative to finite element method. Comparisons are made with corresponding results obtained from finite-element analysis. The results confirm the validity of the solution method. The numerical results present the effects of taper angle, adherend overlap length, and the bilinear adhesive material on the stress fields in the adherends, as well as the adhesive, of a single-lap joint

Basement and regional structure along strike of the Queen Charlotte Fault in the context of modern and historical earthquake ruptures

USGS Publications Warehouse

Walton, Maureen A. L.; Gulick, Sean P. S.; Haeussler, Peter J.; Roland, Emily C.; Tréhu, Anne M.

2015-01-01

The Queen Charlotte fault (QCF) is a dextral transform system located offshore of southeastern Alaska and western Canada, accommodating ∼4.4  cm/yr of relative motion between the Pacific and North American plates. Oblique convergence along the fault increases southward, and how this convergence is accommodated is still debated. Using seismic reflection data, we interpret offshore basement structure, faulting, and stratigraphy to provide a geological context for two recent earthquakes, an Mw 7.5 strike‐slip event near Craig, Alaska, and an Mw 7.8 thrust event near Haida Gwaii, Canada. We map downwarped Pacific oceanic crust near 54° N, between the two rupture zones. Observed downwarping decreases north and south of 54° N, parallel to the strike of the QCF. Bending of the Pacific plate here may have initiated with increased convergence rates due to a plate motion change at ∼6  Ma. Tectonic reconstruction implies convergence‐driven Pacific plate flexure, beginning at 6 Ma south of a 10° bend the QCF (which is currently at 53.2° N) and lasting until the plate translated past the bend by ∼2  Ma. Normal‐faulted approximately late Miocene sediment above the deep flexural depression at 54° N, topped by relatively undeformed Pleistocene and younger sediment, supports this model. Aftershocks of the Haida Gwaii event indicate a normal‐faulting stress regime, suggesting present‐day plate flexure and underthrusting, which is also consistent with reconstruction of past conditions. We thus favor a Pacific plate underthrusting model to initiate flexure and accommodation space for sediment loading. In addition, mapped structures indicate two possible fault segment boundaries along the QCF at 53.2° N and at 56° N.

Explicit formulation of an anisotropic Allman/DKT 3-node thin triangular flat shell elements

NASA Astrophysics Data System (ADS)

Ertas, A.; Krafcik, J. T.; Ekwaro-Osire, S.

A simple, explicit formulation of the stiffness matrix for an anisotropic, 3-node, thin triangular, flat shell element in global coordinates is presented. An Allman triangle is used for membrane stiffness. The membrane stiffness matrix is explicitly derived by applying an Allman transformation to a Felippa 6-node linear strain triangle (LST). Bending stiffness is incorporated by the use of a discrete Kirchhoff triangle (DKT) bending triangle. Stiffness terms resulting from anisotropic membrane-bending coupling are included by integrating, in area coordinates, membrane and bending strain-displacement matrices.

Fracture Mechanics of Thin, Cracked Plates Under Tension, Bending and Out-of-Plane Shear Loading

NASA Technical Reports Server (NTRS)

Zehnder, Alan T.; Hui, C. Y.; Potdar, Yogesh; Zucchini, Alberto

1999-01-01

Cracks in the skin of aircraft fuselages or other shell structures can be subjected to very complex stress states, resulting in mixed-mode fracture conditions. For example, a crack running along a stringer in a pressurized fuselage will be subject to the usual in-plane tension stresses (Mode-I) along with out-of-plane tearing stresses (Mode-III like). Crack growth and initiation in this case is correlated not only with the tensile or Mode-I stress intensity factor, K(sub I), but depends on a combination of parameters and on the history of crack growth. The stresses at the tip of a crack in a plate or shell are typically described in terms of either the small deflection Kirchhoff plate theory. However, real applications involve large deflections. We show, using the von-Karman theory, that the crack tip stress field derived on the basis of the small deflection theory is still valid for large deflections. We then give examples demonstrating the exact calculation of energy release rates and stress intensity factors for cracked plates loaded to large deflections. The crack tip fields calculated using the plate theories are an approximation to the actual three dimensional fields. Using three dimensional finite element analyses we have explored the relationship between the three dimensional elasticity theory and two dimensional plate theory results. The results show that for out-of-plane shear loading the three dimensional and Kirchhoff theory results coincide at distance greater than h/2 from the crack tip, where h/2 is the plate thickness. Inside this region, the distribution of stresses through the thickness can be very different from the plate theory predictions. We have also explored how the energy release rate varies as a function of crack length to plate thickness using the different theories. This is important in the implementation of fracture prediction methods using finite element analysis. Our experiments show that under certain conditions, during fatigue crack growth, the presence of out-of-plane shear loads induces a great deal of contact and friction on the crack surfaces, dramatically reducing crack growth rate. A series of experiments and a proposed computational approach for accounting for the friction is discussed.

Evaluation and optimization of footwear comfort parameters using finite element analysis and a discrete optimization algorithm

NASA Astrophysics Data System (ADS)

Papagiannis, P.; Azariadis, P.; Papanikos, P.

2017-10-01

Footwear is subject to bending and torsion deformations that affect comfort perception. Following review of Finite Element Analysis studies of sole rigidity and comfort, a three-dimensional, linear multi-material finite element sole model for quasi-static bending and torsion simulation, overcoming boundary and optimisation limitations, is described. Common footwear materials properties and boundary conditions from gait biomechanics are used. The use of normalised strain energy for product benchmarking is demonstrated along with comfort level determination through strain energy density stratification. Sensitivity of strain energy against material thickness is greater for bending than for torsion, with results of both deformations showing positive correlation. Optimization for a targeted performance level and given layer thickness is demonstrated with bending simulations sufficing for overall comfort assessment. An algorithm for comfort optimization w.r.t. bending is presented, based on a discrete approach with thickness values set in line with practical manufacturing accuracy. This work illustrates the potential of the developed finite element analysis applications to offer viable and proven aids to modern footwear sole design assessment and optimization.

Effect of Bending Stiffness of the Electroactive Polymer Element on the Performance of a Hybrid Actuator System (HYBAS)

NASA Technical Reports Server (NTRS)

Xu, Tian-Bing; Su, Ji; Jiang, Xiaoning; Rehrig, Paul W.; Zhang, Shujun; Shrout, Thomas R.; Zhang, Qiming

2006-01-01

An electroactive polymer (EAP)-ceramic hybrid actuation system (HYBAS) was developed recently at NASA Langley Research Center. This paper focuses on the effect of the bending stiffness of the EAP component on the performance of a HYBAS, in which the actuation of the EAP element can match the theoretical prediction at various length/thickness ratios for a constant elastic modulus of the EAP component. The effects on the bending stiffness of the elastic modulus and length/thickness ratio of the EAP component were studied. A critical bending stiffness to keep the actuation of the EAP element suitable for a rigid beam theory-based modeling was found for electron irradiated P(VDF-TrFE) copolymer. For example, the agreement of experimental data and theoretical modeling for a HYBAS with the length/thickness ratio of EAP element at 375 times is demonstrated. However, the beam based theoretical modeling becomes invalid (i.e., the profile of the HYBAS movement does not follow the prediction of theoretical modeling) when the bending stiffness is lower than a critical value.

Small bending and stretching of sandwich-type shells

NASA Technical Reports Server (NTRS)

Reissner, Eric

1950-01-01

A theory has been developed for small bending and stretching of sandwich-type shells. This theory is an extension of the known theory of homogeneous thin elastic shells. It was found that two effects are important in the present problem, which are not normally of importance in the theory of curved shells: (1) the effect of transverse shear deformation and (2) the effect of transverse normal stress deformation. The first of these two effects has been known to be of importance in the theory of plates and beams. The second effect was found to occur in a manner which is typical for shells and has no counterpart in flat-plate theory. The general results of this report have been applied to the solution of problems concerning flat plates, circular rings, circular cylindrical shells, and spherical shells. In each case numerical examples have been given, illustrating the magnitude of the effects of transverse shear and normal stress deformation.

The Tasmanides: Phanerozoic Tectonic Evolution of Eastern Australia

NASA Astrophysics Data System (ADS)

Rosenbaum, Gideon

2018-05-01

The Tasmanides occupy the eastern third of Australia and provide an extensive record of the evolution of the eastern Gondwanan convergent plate boundary from the Cambrian to the Triassic. This article presents a summary of the primary building blocks (igneous provinces and sedimentary basins) within the Tasmanides, followed by a discussion of the timing and extent of deformation events. Relatively short episodes of contractional deformation alternated with longer periods of crustal extension accompanied by voluminous magmatism. This behavior was likely controlled by plate boundary migration (trench retreat and advance) that was also responsible for bending and segmentation of the convergent plate margin. As a result, the Tasmanides were subjected to at least three major phases of oroclinal bending, in the Silurian, Devonian, and Permian. The most significant segmentation likely occurred at ˜420–400 Ma along a lithospheric-scale boundary that separated the northern and southern parts of the Tasmanides.

Plane elasto-plastic analysis of v-notched plate under bending by boundary integral equation method. Ph.D. Thesis

NASA Technical Reports Server (NTRS)

Rzasnicki, W.

1973-01-01

A method of solution is presented, which, when applied to the elasto-plastic analysis of plates having a v-notch on one edge and subjected to pure bending, will produce stress and strain fields in much greater detail than presently available. Application of the boundary integral equation method results in two coupled Fredholm-type integral equations, subject to prescribed boundary conditions. These equations are replaced by a system of simultaneous algebraic equations and solved by a successive approximation method employing Prandtl-Reuss incremental plasticity relations. The method is first applied to number of elasto-static problems and the results compared with available solutions. Good agreement is obtained in all cases. The elasto-plastic analysis provides detailed stress and strain distributions for several cases of plates with various notch angles and notch depths. A strain hardening material is assumed and both plane strain and plane stress conditions are considered.

Finite element residual stress analysis of induction heating bended ferritic steel piping

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kima, Jong Sung; Kim, Kyoung-Soo; Oh, Young-Jin

2014-10-06

Recently, there is a trend to apply the piping bended by induction heating process to nuclear power plants. Residual stress can be generated due to thermo-mechanical mechanism during the induction heating bending process. It is well-known that the residual stress has important effect on crack initiation and growth. The previous studies have focused on the thickness variation. In part, some studies were performed for residual stress evaluation of the austenitic stainless steel piping bended by induction heating. It is difficult to find the residual stresses of the ferritic steel piping bended by the induction heating. The study assessed the residualmore » stresses of induction heating bended ferriticsteel piping via finite element analysis. As a result, it was identified that high residual stresses are generated on local outersurface region of the induction heating bended ferritic piping.« less

Virtual plate pre-bending for the long bone fracture based on axis pre-alignment.

PubMed

Liu, Bin; Luo, Xinjian; Huang, Rui; Wan, Chao; Zhang, Bingbing; Hu, Weihua; Yue, Zongge

2014-06-01

In this paper, a modeling and visualizing system for assisting surgeons in correctly registering for the closed fracture reduction surgery is presented. By using this system, the geometric parameters of the target fixation plate before the long bone fracture operation can be obtained. The main processing scheme consists of following steps: firstly (image data process), utilize the Curvelet transform to denoise the CT images of fracture part and then reconstruct the 3D models of the broken bones. Secondly (pre-alignment), extract the axial lines of the broken bones and spatially align them. Then drive the broken bone models to be pre-aligned. Thirdly (mesh segmentation), a method based on vertex normal feature is utilized to obtain the broken bone cross-sections mesh models. Fourthly (fine registration), the ICP (Iterative Closest Point) algorithm is used to register the cross-sections and the broken bone models are driven to achieve the fine registration posture. Lastly (plate fitting), an accurate NURBS surface fitting method is used to construct the virtual plate. The experiment proved that the obtained models of the pre-bended plates were closely bonded to the surface of the registered long bone models. Finally, the lengths, angles and other interested geometric parameters can be measured on the plate models. Copyright © 2014 Elsevier Ltd. All rights reserved.

Development of a bending stiffness model for wet process fiberboard

Treesearch

Chris Turk; John F. Hunt

2007-01-01

In traditional mechanics of materials, the stiffness of a beam or plate in bending is described by its cross-sectional shape as well as its material properties, primarily the modulus of elasticity. Previous work at the USDA Forest Products Laboratory, Madison, Wisconsin, has shown that modulus of elasticity has a strong correlation to the density of the fiberboard....

ELISA - an electrostatic storage ring for low-energy ions

NASA Astrophysics Data System (ADS)

Pape Moeller, Soeren

1997-05-01

The design of a new type of storage ring for low-energy ions using electrostatic deflection and focusing devices is described. Electrostatic bends and quadrupoles are used since they are more efficient than magnetic ones for low-velocity heavy ions. Furthermore, electrostatic devices are more compact and easier to construct than magnetic devices. In comparison to an electromagnetic trap, one important advantage of the elecrostatic ring is the easy access to the circulating beam and its decay products. These and other features, e.g. no magnetic fields, makes such storage devices attractive for many atomic-physics experiments. Also neigboring fields as chemistry and biology might benefit from such an relatively inexpensive device. One important difference between an electrostatic and a magnetic ring is, that the longitudinal energy is not conserved for the electrostatic ring. The actual ring will have a race-track shape as defined by two straight sections each with two quadrupole doublets connected by 180-degrees bends. The bends will consist of 160-degrees spherical deflection plates surrounded by two parallel plate 10-degrees bends. The storage ring ELISA, currently being built, will have a circumference of 6 meters. The first beam tests will take place during summer 1996.

Experimental Attempts for Deep Insertion in Ultrasonically Forced Insertion Process

NASA Astrophysics Data System (ADS)

Ono, Satoshi; Aoyagi, Manabu; Tamura, Hideki; Takano, Takehiro

2011-07-01

In this paper, we describe two attempts of obtaining deep insertion in an ultrasonically forced insertion (USFI) process. One was to correct the inclination of an inserted rod by passively generated bending vibrations. The inclination causes a partial plastic deformation, which decreases the holding power of processing materials. Two types of horn with grooves for excitation of bending vibrations were examined. The other was to make differences in vibration velocity and the phase of a rod and a metal plate by damping the vibration of a metal plate by using a rubber sheet. As results, the attempts proposed in this study were confirmed to be effective to obtain a deep insertion.

Extensional Failure of "Pre-Stressed" Lithosphere Above a Subduction Zone May Have Contributed to the Size of the Tohoku-Oki Earthquake and Tsunami

NASA Astrophysics Data System (ADS)

Buck, W. R.; Lavier, L. L.; Petersen, K. D.

2015-12-01

The Tohoku-oki earthquake was not only the costliest natural disaster in history it was the best monitored. The unprecedented data set showed that anomalously large lateral motion of the seafloor near the trench contributed to the size of the tsunami. Also, for the first time it was shown that a large subduction earthquake was followed by extensional aftershocks in a broad region of the upper plate (up to 250 km from the Japan Trench). Several observations suggest that the near-trench seafloor motion and the extensional aftershocks are linked. For example, a seismically imaged fault, just landward of the region of large seafloor motion, slipped in a normal sense during the earthquake. Also, inspired by the Tohoku data, researchers have searched for and found upper plate extensional aftershocks associated with several other subduction earthquakes that produced large tsunami. Extension of the upper plate can be driven by a reduction in the dip of a subducting slab. Such a dip change is suggested by the post-Miocene westward migration of the volcanic arc in Honshu. Numerical models show that a long-term reduction in slab dip can generate enough extensional stress to cause normal faulting over a broad region of the upper plate. The time step of the numerical model is then reduced to treat the inter-seismic time scale of 100-1000 years, when the subduction interface is locked. The interface dip continues to be reduced during the inter-seismic period, but extensional fault slip is suppressed by the relative compression of the upper plate caused by continued convergence. The relief of compressional stresses during dynamic weakening of the megathrust triggers a release of bending-related extensional strain energy. This extensional yielding can add significantly to the co-seismic radiated seismic energy and seafloor deformation. This mechanism is analogous to the breaking of a pre-stressed concrete beam supporting a bending moment when the compressional pre-stress is removed. It is plausible that similar bending is occurring at a number of subduction zones. A testable prediction of this bending model is that inter-seismic stresses can be compressional near the surface of the upper plate, but should become extensional at depths accessible to drilling.

Biomechanics of bone-fracture fixation by stiffness-graded plates in comparison with stainless-steel plates

PubMed Central

Ganesh, VK; Ramakrishna, K; Ghista, Dhanjoo N

2005-01-01

Background In the internal fixation of fractured bone by means of bone-plates fastened to the bone on its tensile surface, an on-going concern has been the excessive stress-shielding of the bone by the excessively-stiff stainless-steel plate. The compressive stress-shielding at the fracture-interface immediately after fracture-fixation delays callus formation and bone healing. Likewise, the tensile stress-shielding of the layer of the bone underneath the plate can cause osteoporosis and decrease in tensile strength of this layer. Method In order to address this problem, we propose to use stiffness-graded plates. Accordingly, we have computed (by finite-element analysis) the stress distribution in the fractured bone fixed by composite plates, whose stiffness is graded both longitudinally and transversely. Results It can be seen that the stiffness-graded composite-plates cause less stress-shielding (as an example: at 50% of the healing stage, stress at the fracture interface is compressive in nature i.e. 0.002 GPa for stainless steel plate whereas stiffness graded plates provides tensile stress of 0.002 GPa. This means that stiffness graded plate is allowing the 50% healed bone to participate in loadings). Stiffness-graded plates are more flexible, and hence permit more bending of the fractured bone. This results in higher compressive stresses induced at the fractured faces accelerate bone-healing. On the other hand, away from the fracture interface the reduced stiffness and elastic modulus of the plate causes the neutral axis of the composite structure to be lowered into the bone resulting in the higher tensile stress in the bone-layer underneath the plate, wherein is conducive to the bone preserving its tensile strength. Conclusion Stiffness graded plates (with in-built variable stiffness) are deemed to offer less stress-shielding to the bone, providing higher compressive stress at the fractured interface (to induce accelerated healing) as well as higher tensile stress in the intact portion of the bone (to prevent bone remodeling and osteoporosis). PMID:16045807

Stiffness and strength of fiber reinforced polymer composite bridge deck systems

NASA Astrophysics Data System (ADS)

Zhou, Aixi

This research investigates two principal characteristics that are of primary importance in Fiber Reinforced Polymer (FRP) bridge deck applications: STIFFNESS and STRENGTH. The research was undertaken by investigating the stiffness and strength characteristics of the multi-cellular FRP bridge deck systems consisting of pultruded FRP shapes. A systematic analysis procedure was developed for the stiffness analysis of multi-cellular FRP deck systems. This procedure uses the Method of Elastic Equivalence to model the cellular deck as an equivalent orthotropic plate. The procedure provides a practical method to predict the equivalent orthotropic plate properties of cellular FRP decks. Analytical solutions for the bending analysis of single span decks were developed using classical laminated plate theory. The analysis procedures can be extended to analyze continuous FRP decks. It can also be further developed using higher order plate theories. Several failure modes of the cellular FRP deck systems were recorded and analyzed through laboratory and field tests and Finite Element Analysis (FEA). Two schemes of loading patches were used in the laboratory test: a steel patch made according to the ASSHTO's bridge testing specifications; and a tire patch made from a real truck tire reinforced with silicon rubber. The tire patch was specially designed to simulate service loading conditions by modifying real contact loading from a tire. Our research shows that the effects of the stiffness and contact conditions of loading patches are significant in the stiffness and strength testing of FRP decks. Due to the localization of load, a simulated tire patch yields larger deflection than the steel patch under the same loading level. The tire patch produces significantly different failure compared to the steel patch: a local bending mode with less damage for the tire patch; and a local punching-shear mode for the steel patch. A deck failure function method is proposed for predicting the failure of FRP decks. Using developed laminated composite theories and FEA techniques, a strength analysis procedure containing ply-level information was proposed and detailed for FRP deck systems. The behavior of the deck's unsupported (free) edges was also investigated using ply-level FEA.

Shielded transient self-interaction of a bunch entering a circle from a straight path

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, R.; Bohn, C.L.; Bisognano, J.J.

1997-08-01

Recent developments in electron-gun and injector technologies enable production of short (mm-length), high-charge (nC-regime) bunches. In this parameter regime, the curvature effect on the bunch self-interaction, by way of coherent synchrotron radiation (CSR) and space-charge forces as the beam traverses magnet bends, may cause serious emittance degradation. In this paper, the authors study an electron bunch orbiting between two infinite, parallel conducting plates. The bunch moves on a trajectory from a straight path to a circular orbit and begins radiating. Transient effects, arising from CSR and space-charge forces generated from source particles both on the bend and on the straightmore » path prior to the bend, are analyzed using Lienard-Wiechert fields, and their overall net effect is obtained. The influence of the plates on the transients is contrasted to their shielding of the steady-state radiated power. Results for emittance degradation induced by this self-interaction are also presented.« less

Large deflection analysis of a pre-stressed annular plate with a rigid boss under axisymmetric loading

NASA Astrophysics Data System (ADS)

Su, Y. H.; Chen, K. S.; Roberts, D. C.; Spearing, S. M.

2001-11-01

The large deflection analysis of a pre-stressed annular plate with a central rigid boss subjected to axisymmetric loading is presented. The factors affecting the transition from plate behaviour to membrane behaviour (e.g. thickness, in-plane tension and material properties) are studied. The effect of boss size and pre-tension on the effective stiffness of the plate are investigated. The extent of the bending boundary layers at the edges of the plate are quantified. All results are presented in non-dimensional form. The design implications for microelectromechanical system components are assessed.

Quasi-one-dimensional modes in strip plates: Theory and experiment

DOE Office of Scientific and Technical Information (OSTI.GOV)

Arreola, A.; Báez, G.; Méndez-Sánchez, R. A.

2014-01-14

Using acoustic resonance spectroscopy we measure the elastic resonances of a strip rectangular plate with all its ends free. The experimental setup consist of a vector network analyzer, a high-fidelity audio amplifier, and electromagnetic-acoustic transducers. The one-dimensional modes are identified from the measured spectra by comparing them with theoretical predictions of compressional and bending modes of the plate modeled as a beam. The agreement between theory and experiment is excellent.

A MEMS Multi-Cantilever Variable Capacitor On Metamaterial

DTIC Science & Technology

2009-03-26

tuning range [38]. 21 Bakri- Kassem and Mansour [39] have developed a parallel-plate variable capac- itor with carrier beams between the plates to...downwards, however, the carrier beams slightly bend down with the movable plate, still prevent- ing it from pulling-in. Bakri- Kassem and Mansour’s... Kassem and R. R. Mansour, “A high-tuning-range mems variable ca- pacitor using carrier beams,” Canadian Journal of Electrical and Computer En- gineering

DYCAST: A finite element program for the crash analysis of structures

NASA Technical Reports Server (NTRS)

Pifko, A. B.; Winter, R.; Ogilvie, P.

1987-01-01

DYCAST is a nonlinear structural dynamic finite element computer code developed for crash simulation. The element library contains stringers, beams, membrane skin triangles, plate bending triangles and spring elements. Changing stiffnesses in the structure are accounted for by plasticity and very large deflections. Material nonlinearities are accommodated by one of three options: elastic-perfectly plastic, elastic-linear hardening plastic, or elastic-nonlinear hardening plastic of the Ramberg-Osgood type. Geometric nonlinearities are handled in an updated Lagrangian formulation by reforming the structure into its deformed shape after small time increments while accumulating deformations, strains, and forces. The nonlinearities due to combined loadings are maintained, and stiffness variation due to structural failures are computed. Numerical time integrators available are fixed-step central difference, modified Adams, Newmark-beta, and Wilson-theta. The last three have a variable time step capability, which is controlled internally by a solution convergence error measure. Other features include: multiple time-load history tables to subject the structure to time dependent loading; gravity loading; initial pitch, roll, yaw, and translation of the structural model with respect to the global system; a bandwidth optimizer as a pre-processor; and deformed plots and graphics as post-processors.

A comparative biomechanical analysis of implants for the stabilization of proximal humerus fractures.

PubMed

Füchtmeier, B; May, R; Fierlbeck, J; Hammer, J; Nerlich, M

2006-01-01

A new humerus nail (Sirus) has become available for the treatment of fractures of the proximal humerus. The aim of the study was the biomechanical comparison of this implant with established systems. 12 matched pairs of human humeri were employed for testing. Three randomized groups were formed (n = 4 pairs). A bending moment of 7.5 Nm and a torsional moment of 8.3 Nm were applied in a test of five loading cycles to all intact bones. Loading was consistently initiated at the distal epiphysis. The consequent deformation at the distal epiphysis was continuously recorded. Then an osteotomy with a defect of 5 mm was created to simulate an unstable subcapital humerus fracture. For paired comparison, one of each pair was stabilized with the Sirus proximal humerus nail. The other side was fixed with a reference implant. The following groups were created.: Group I: Sirus versus Proximal humerus nail (PHN) with spiral blade. Group II: Sirus versus PHILOS plate. Group III: Sirus versus 4.5 mm AO T-plate. The proximal humerus nail (Sirus) demonstrated significantly higher stiffness values than the reference implants for both bending and torsional load. The following values were recorded at a bending moment of 7.5 Nm: Sirus 14.2 mm, PHN 20.7 mm, PHILOS plate 28.1 mm, 4.5 AO T-plate 29.3 mm p < 0.0012). The values at 8.3 Nm torsional moment were: Sirus 8.5 degrees , PHN 12.3 degrees , PHILOS plate 16.4 degrees , 4.5 AO T-Platte 15.6 degrees (p < 0.002). The intramedullary load carriers were biomechanically superior when compared to the plating systems in the fracture model presented here. Supplementary, the Sirus Nail showed higher stiffness values than the PHN. However, the latter are gaining in importance due to the possibility of minimal invasive implantation. Whether this will be associated with functional advantages requires further clinical investigation.

Tectonic controls on earthquake size distribution and seismicity rate: slab buoyancy and slab bending

NASA Astrophysics Data System (ADS)

Nishikawa, T.; Ide, S.

2014-12-01

There are clear variations in maximum earthquake magnitude among Earth's subduction zones. These variations have been studied extensively and attributed to differences in tectonic properties in subduction zones, such as relative plate velocity and subducting plate age [Ruff and Kanamori, 1980]. In addition to maximum earthquake magnitude, the seismicity of medium to large earthquakes also differs among subduction zones, such as the b-value (i.e., the slope of the earthquake size distribution) and the frequency of seismic events. However, the casual relationship between the seismicity of medium to large earthquakes and subduction zone tectonics has been unclear. Here we divide Earth's subduction zones into over 100 study regions following Ide [2013] and estimate b-values and the background seismicity rate—the frequency of seismic events excluding aftershocks—for subduction zones worldwide using the maximum likelihood method [Utsu, 1965; Aki, 1965] and the epidemic type aftershock sequence (ETAS) model [Ogata, 1988]. We demonstrate that the b-value varies as a function of subducting plate age and trench depth, and that the background seismicity rate is related to the degree of slab bending at the trench. Large earthquakes tend to occur relatively frequently (lower b-values) in shallower subduction zones with younger slabs, and more earthquakes occur in subduction zones with deeper trench and steeper dip angle. These results suggest that slab buoyancy, which depends on subducting plate age, controls the earthquake size distribution, and that intra-slab faults due to slab bending, which increase with the steepness of the slab dip angle, have influence on the frequency of seismic events, because they produce heterogeneity in plate coupling and efficiently inject fluid to elevate pore fluid pressure on the plate interface. This study reveals tectonic factors that control earthquake size distribution and seismicity rate, and these relationships between seismicity and tectonic properties may be useful for seismic risk assessment.

Chairside CAD/CAM materials. Part 2: Flexural strength testing.

PubMed

Wendler, Michael; Belli, Renan; Petschelt, Anselm; Mevec, Daniel; Harrer, Walter; Lube, Tanja; Danzer, Robert; Lohbauer, Ulrich

2017-01-01

Strength is one of the preferred parameters used in dentistry for determining clinical indication of dental restoratives. However, small dimensions of CAD/CAM blocks limit reliable measurements with standardized uniaxial bending tests. The objective of this study was to introduce the ball-on-three-ball (B3B) biaxial strength test for dental for small CAD/CAM block in the context of the size effect on strength predicted by the Weibull theory. Eight representative chairside CAD/CAM materials ranging from polycrystalline zirconia (e.max ZirCAD, Ivoclar-Vivadent), reinforced glasses (Vitablocs Mark II, VITA; Empress CAD, Ivoclar-Vivadent) and glass-ceramics (e.max CAD, Ivoclar-Vivadent; Suprinity, VITA; Celtra Duo, Dentsply) to hybrid materials (Enamic, VITA; Lava Ultimate, 3M ESPE) have been selected. Specimens were prepared with highly polished surfaces in rectangular plate (12×12×1.2mm 3 ) or round disc (Ø=12mm, thickness=1.2mm) geometries. Specimens were tested using the B3B assembly and the biaxial strength was determined using calculations derived from finite element analyses of the respective stress fields. Size effects on strength were determined based on results from 4-point-bending specimens. A good agreement was found between the biaxial strength results for the different geometries (plates vs. discs) using the B3B test. Strength values ranged from 110.9MPa (Vitablocs Mark II) to 1303.21MPa (e.max ZirCAD). The strength dependency on specimen size was demonstrated through the calculated effective volume/surface. The B3B test has shown to be a reliable and simple method for determining the biaxial strength restorative materials supplied as small CAD/CAM blocks. A flexible solution was made available for the B3B test in the rectangular plate geometry. Copyright © 2016 The Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

Prediction of impact force and duration during low velocity impact on circular composite laminates

NASA Technical Reports Server (NTRS)

Shivakumar, K. N.; Elber, W.; Illg, W.

1983-01-01

Two simple and improved models--energy-balance and spring-mass--were developed to calculate impact force and duration during low velocity impact of circular composite plates. Both models include the contact deformation of the plate and the impactor as well as bending, transverse shear, and membrane deformations of the plate. The plate was transversely isotropic graphite/epoxy composite laminate and the impactor was a steel sphere. Calculated impact forces from the two analyses agreed with each other. The analyses were verified by comparing the results with reported test data.

Biomechanical evaluation of fracture fixation constructs using a variable-angle locked periprosthetic femur plate system.

PubMed

Hoffmann, Martin F; Burgers, Travis A; Mason, James J; Williams, Bart O; Sietsema, Debra L; Jones, Clifford B

2014-07-01

In the United States there are more than 230,000 total hip replacements annually, and periprosthetic femoral fractures occur in 0.1-4.5% of those patients. The majority of these fractures occur at the tip of the stem (Vancouver type B1). The purpose of this study was to compare the biomechanically stability and strength of three fixation constructs and identify the most desirable construct. Fifteen medium adult synthetic femurs were implanted with a hip prosthesis and were osteotomized in an oblique plane at the level of the implant tip to simulate a Vancouver type B1 periprosthetic fracture. Fractures were fixed with a non-contact bridging periprosthetic proximal femur plate (Zimmer Inc., Warsaw, IN). Three proximal fixation methods were used: Group 1, bicortical screws; Group 2, unicortical screws and one cerclage cable; and Group 3, three cerclage cables. Distally, all groups had bicortical screws. Biomechanical testing was performed using an axial-torsional testing machine in three different loading modalities (axial compression, lateral bending, and torsional/sagittal bending), next in axial cyclic loading to 10,000 cycles, again in the three loading modalities, and finally to failure in torsional/sagittal bending. Group 1 had significantly greater load to failure and was significantly stiffer in torsional/sagittal bending than Groups 2 and 3. After cyclic loading, Group 2 had significantly greater axial stiffness than Groups 1 and 3. There was no difference between the three groups in lateral bending stiffness. The average energy absorbed during cyclic loading was significantly lower in Group 2 than in Groups 1 and 3. Bicortical screw placement achieved the highest load to failure and the highest torsional/sagittal bending stiffness. Additional unicortical screws improved axial stiffness when using cable fixation. Lateral bending was not influenced by differences in proximal fixation. To treat periprosthetic fractures, bicortical screw placement should be attempted to maximize load to failure and torsional/sagittal bending stiffness. Copyright © 2014 Elsevier Ltd. All rights reserved.

Crustal Density Variation Along the San Andreas Fault Controls Its Secondary Faults Distribution and Dip Direction

NASA Astrophysics Data System (ADS)

Yang, H.; Moresi, L. N.

2017-12-01

The San Andreas fault forms a dominant component of the transform boundary between the Pacific and the North American plate. The density and strength of the complex accretionary margin is very heterogeneous. Based on the density structure of the lithosphere in the SW United States, we utilize the 3D finite element thermomechanical, viscoplastic model (Underworld2) to simulate deformation in the San Andreas Fault system. The purpose of the model is to examine the role of a big bend in the existing geometry. In particular, the big bend of the fault is an initial condition of in our model. We first test the strength of the fault by comparing the surface principle stresses from our numerical model with the in situ tectonic stress. The best fit model indicates the model with extremely weak fault (friction coefficient < 0.1) is requisite. To the first order, there is significant density difference between the Great Valley and the adjacent Mojave block. The Great Valley block is much colder and of larger density (>200 kg/m3) than surrounding blocks. In contrast, the Mojave block is detected to find that it has lost its mafic lower crust by other geophysical surveys. Our model indicates strong strain localization at the jointer boundary between two blocks, which is an analogue for the Garlock fault. High density lower crust material of the Great Valley tends to under-thrust beneath the Transverse Range near the big bend. This motion is likely to rotate the fault plane from the initial vertical direction to dip to the southwest. For the straight section, north to the big bend, the fault is nearly vertical. The geometry of the fault plane is consistent with field observations.

[Development of denture base resin. 2. Manufacturing of visible-light cured prepreg and physical properties of FRP].

PubMed

Kimura, H; Yu, P Y; Teraoka, F; Sugita, M

1989-09-01

To develop the visible light-cured FRP denture base, we investigated the physical properties and the warp of FRP plate by using various combinations of matrix resin and reinforcement. From the results of the bending test, hardness test and manipulation processing, the matrix resin of Bis-GMA/UDMA/3 G at 48/48/4 wt% was determined. The sateen weave's glasscloth as the reinforcement of the prepreg was used. The maximum plies included FRP of 0.5 mm, 0.8 and 1.0 mm thickness have the same maximum bending strengths of 45 kgf/mm2, which is about 5 times larger than that of conventional acrylic resin. The warp of these FRP plates were not found.

Reinforcement of Wood Pallets with Metal Connector Plates

Treesearch

John W. Clarke; Thomas E. McLain; Marshall S. White; Philip A. Araman

1993-01-01

Reinforcement of the damage-prone areas of wood pallet stringers with metal connector plates (MCPs) may increase useful pallet life or permit use of less desirable wood species. This will improve the utilization of our timber resources and landfill space. Whole pallets and individual stringers, reinforced at the inner notches, were tested in static bending. Stringer...

Progress in the Modeling of the Shock Response and Mitigation of Thick Composite Shells

DTIC Science & Technology

1993-07-22

reoporoe, IndWing the time tfo reviewing instructions, eavechexi o•tig datl ecucee. tiaherka e meirtdai"g the date ri -ded, "nd competing and...the plate can be approximated using a one dimensional model. Once bending and tranverse shear waves reach the center portion of the plate, this

Forearc collapse, plate flexure, and seismicity within the downgoing plate along the Sunda Arc west of Sumatra

NASA Astrophysics Data System (ADS)

Craig, Timothy J.; Copley, Alex

2018-02-01

Deformation within the downgoing oceanic lithosphere seawards of subduction zones is typically characterised by regimes of shallow extension and deeper compression, due to the bending of the oceanic plate as it dips into the subduction zone. However, offshore Sumatra there are shallow compressional earthquakes within the downgoing oceanic plate outboard of the region of high slip in the 2004 Aceh-Andaman earthquake, occurring at the same depth as extensional faulting further seaward from the trench. A clear separation is seen in the location of intraplate earthquakes, with extensional earthquakes occurring further seawards than compressional earthquakes at the same depth within the plate. The adjacent section of the forearc prism west of Aceh is also anomalous in its morphology, characterised by a wide prism with a steep bathymetric front and broad, gradually-sloping top. This shape is in contrast to the narrower and more smoothly-sloping prism to the south, and along other subduction zones. The anomalous near-trench intraplate earthquakes and prism morphology are likely to be the result of the geologically-rapid gravitational collapse of the forearc, which leads to induced bending within the subducting plate, and the distinctive plateau-like morphology of the forearc. Such collapse of the forearc could be caused by changes through time of the material properties of the forearc rocks, or of the thickness of the sediments entering the subduction zone.

High-speed pressure clamp.

PubMed

Besch, Stephen R; Suchyna, Thomas; Sachs, Frederick

2002-10-01

We built a high-speed, pneumatic pressure clamp to stimulate patch-clamped membranes mechanically. The key control element is a newly designed differential valve that uses a single, nickel-plated piezoelectric bending element to control both pressure and vacuum. To minimize response time, the valve body was designed with minimum dead volume. The result is improved response time and stability with a threefold decrease in actuation latency. Tight valve clearances minimize the steady-state air flow, permitting us to use small resonant-piston pumps to supply pressure and vacuum. To protect the valve from water contamination in the event of a broken pipette, an optical sensor detects water entering the valve and increases pressure rapidly to clear the system. The open-loop time constant for pressure is 2.5 ms for a 100-mmHg step, and the closed-loop settling time is 500-600 micros. Valve actuation latency is 120 micros. The system performance is illustrated for mechanically induced changes in patch capacitance.

Three-dimensional analysis of anisotropic spatially reinforced structures

NASA Technical Reports Server (NTRS)

Bogdanovich, Alexander E.

1993-01-01

The material-adaptive three-dimensional analysis of inhomogeneous structures based on the meso-volume concept and application of deficient spline functions for displacement approximations is proposed. The general methodology is demonstrated on the example of a brick-type mosaic parallelepiped arbitrarily composed of anisotropic meso-volumes. A partition of each meso-volume into sub-elements, application of deficient spline functions for a local approximation of displacements and, finally, the use of the variational principle allows one to obtain displacements, strains, and stresses at anypoint within the structural part. All of the necessary external and internal boundary conditions (including the conditions of continuity of transverse stresses at interfaces between adjacent meso-volumes) can be satisfied with requisite accuracy by increasing the density of the sub-element mesh. The application of the methodology to textile composite materials is described. Several numerical examples for woven and braided rectangular composite plates and stiffened panels under transverse bending are considered. Some typical effects of stress concentrations due to the material inhomogeneities are demonstrated.

An experiment for determining the Euler load by direct computation

NASA Technical Reports Server (NTRS)

Thurston, Gaylen A.; Stein, Peter A.

1986-01-01

A direct algorithm is presented for computing the Euler load of a column from experimental data. The method is based on exact inextensional theory for imperfect columns, which predicts two distinct deflected shapes at loads near the Euler load. The bending stiffness of the column appears in the expression for the Euler load along with the column length, therefore the experimental data allows a direct computation of bending stiffness. Experiments on graphite-epoxy columns of rectangular cross-section are reported in the paper. The bending stiffness of each composite column computed from experiment is compared with predictions from laminated plate theory.

Biomechanical comparison of three different plate configurations for comminuted clavicle midshaft fracture fixation.

PubMed

Uzer, Gokcer; Yildiz, Fatih; Batar, Suat; Bozdag, Ergun; Kuduz, Hacer; Bilsel, Kerem

2017-12-01

The aim of this study was to compare the fixation rigidity of anterior, anterosuperior, and superior plates in the treatment of comminuted midshaft clavicle fractures. Six-hole titanium alloy plates were produced according to anatomic features of fourth-generation artificial clavicle models for anterior (group I; n = 14), anterosuperior (group II; n = 14), and superior (group III; n = 14) fixation. After plate fixation, 5-mm segments were resected from the middle third of each clavicle to create comminuted fracture models. Half the models from each group were tested under rotational forces; the other half were tested under 3-point bending forces. Failure modes, stiffness values, and failure loads were recorded. All models fractured at the level of the distalmost screw during the failure torque, whereas several failure modes were observed in 3-point bending tests. The mean stiffness values of groups I to III were 636 ± 78, 767 ± 72, and 745 ± 214 N ∙ mm/deg (P = .171), respectively, for the torsional tests and 38 ± 5, 20 ± 3, and 13 ± 2 N/mm, respectively, for the bending tests (P < .001 for group I vs. groups II and III; P = .015 for group II vs. group III). The mean failure torque values of groups I to III were 8248 ± 2325, 12,638 ± 1749, and 10,643 ± 1838 N ∙ mm (P = .02 for group I vs. II), respectively, and the mean failure loads were 409 ± 81, 360 ± 122, and 271 ± 87 N, respectively (P = .108). In the surgical treatment of comminuted midshaft clavicle fractures, the fixation strength of anterosuperior plating was greater than that of anterior plating under rotational forces and similar to that of superior plating. Copyright © 2017 Journal of Shoulder and Elbow Surgery Board of Trustees. Published by Elsevier Inc. All rights reserved.

Bending and splitting of spoof surface acoustic waves through structured rigid surface

NASA Astrophysics Data System (ADS)

Xie, Sujun; Ouyang, Shiliang; He, Zhaojian; Wang, Xiaoyun; Deng, Ke; Zhao, Heping

2018-03-01

In this paper, we demonstrated that a 90°-bended imaging of spoof surface acoustic waves with subwavelength resolution of 0.316λ can be realized by a 45° prism-shaped surface phononic crystal (SPC), which is composed of borehole arrays with square lattice in a rigid plate. Furthermore, by combining two identical prism-shaped phononic crystal to form an interface (to form a line-defect), the excited spoof surface acoustic waves can be split into bended and transmitted parts. The power ratio between the bended and transmitted surface waves can be tuned arbitrarily by adjusting the defect size. This acoustic system is believed to have potential applications in various multifunctional acoustic solutions integrated by different acoustical devices.

The dynamics of plate tectonics and mantle flow: from local to global scales.

PubMed

Stadler, Georg; Gurnis, Michael; Burstedde, Carsten; Wilcox, Lucas C; Alisic, Laura; Ghattas, Omar

2010-08-27

Plate tectonics is regulated by driving and resisting forces concentrated at plate boundaries, but observationally constrained high-resolution models of global mantle flow remain a computational challenge. We capitalized on advances in adaptive mesh refinement algorithms on parallel computers to simulate global mantle flow by incorporating plate motions, with individual plate margins resolved down to a scale of 1 kilometer. Back-arc extension and slab rollback are emergent consequences of slab descent in the upper mantle. Cold thermal anomalies within the lower mantle couple into oceanic plates through narrow high-viscosity slabs, altering the velocity of oceanic plates. Viscous dissipation within the bending lithosphere at trenches amounts to approximately 5 to 20% of the total dissipation through the entire lithosphere and mantle.

Laser-Excited Electronic and Thermal Elastic Vibrations in a Semiconductor Rectangular Plate

NASA Astrophysics Data System (ADS)

Todorović, D. M.; Cretin, B.; Vairac, P.; Song, Y. Q.; Rabasović, M. D.; Markushev, D. D.

2013-09-01

Photoacoustic and photothermal effects can be important as driven mechanisms for micro-(opto)-electro-mechanical structures (MOEMS). A new approach for a producing a compact, lightweight, highly sensitive detector is provided by MOEMS technology, which is based on the elastic bending of microstructure generated by absorption of modulated optical power. The electronic and thermal elastic vibrations (the electronic deformation and thermoelastic mechanisms of elastic wave generation) in a semiconductor rectangular simply supported plate (3D geometry), photogenerated by a focused and intensity-modulated laser beam, were studied. The theoretical model for the elastic displacements space and frequency distribution by using the Green function method was given. The amplitude of the elastic bending in the rectangular plate was calculated and analyzed, including the thermalization and surface and volume recombination heat sources. The theoretical results were compared with the experimental data. These investigations are important for many practical experimental situations (atomic force microscopy, thermal microscopy, thermoelastic microscopy, etc.) and sensors and actuators.

Analysis of Ninety Degree Flexure Tests for Characterization of Composite Transverse Tensile Strength

NASA Technical Reports Server (NTRS)

OBrien, T. Kevin; Krueger, Ronald

2001-01-01

Finite element (FE) analysis was performed on 3-point and 4-point bending test configurations of ninety degree oriented glass-epoxy and graphite-epoxy composite beams to identify deviations from beam theory predictions. Both linear and geometric non-linear analyses were performed using the ABAQUS finite element code. The 3-point and 4-point bending specimens were first modeled with two-dimensional elements. Three-dimensional finite element models were then performed for selected 4-point bending configurations to study the stress distribution across the width of the specimens and compare the results to the stresses computed from two-dimensional plane strain and plane stress analyses and the stresses from beam theory. Stresses for all configurations were analyzed at load levels corresponding to the measured transverse tensile strength of the material.

An analysis of thermal stress and gas bending effects on vibrations of compressor rotor stages. [blade torsional rigidity

NASA Technical Reports Server (NTRS)

Chen, L.-T.; Dugundji, J.

1979-01-01

A preliminary study conducted by Kerrebrock et al. (1976) has shown that the torsional rigidity of untwisted thin blades of a transonic compressor can be reduced significantly by transient thermal stresses. The aerodynamic loads have various effects on blade vibration. One effect is that gas bending loads may result in a bending-torsion coupling which may change the characteristics of the torsion and bending vibration of the blade. For a general study of transient-temperature distribution within a rotor stage, a finite-element heat-conduction analysis was developed. The blade and shroud are divided into annular elements. With a temperature distribution obtained from the heat-conduction analysis and a prescribed gas bending load distribution along the blade span, the static deformation and moment distributions of the blade can be solved iteratively using the finite-element method. The reduction of the torsional rigidity of pretwisted blades caused by the thermal stress effect is then computed. The dynamic behavior of the blade is studied by a modified Galerkin's method.

Analytical and Numerical Results for an Adhesively Bonded Joint Subjected to Pure Bending

NASA Technical Reports Server (NTRS)

Smeltzer, Stanley S., III; Lundgren, Eric

2006-01-01

A one-dimensional, semi-analytical methodology that was previously developed for evaluating adhesively bonded joints composed of anisotropic adherends and adhesives that exhibit inelastic material behavior is further verified in the present paper. A summary of the first-order differential equations and applied joint loading used to determine the adhesive response from the methodology are also presented. The method was previously verified against a variety of single-lap joint configurations from the literature that subjected the joints to cases of axial tension and pure bending. Using the same joint configuration and applied bending load presented in a study by Yang, the finite element analysis software ABAQUS was used to further verify the semi-analytical method. Linear static ABAQUS results are presented for two models, one with a coarse and one with a fine element meshing, that were used to verify convergence of the finite element analyses. Close agreement between the finite element results and the semi-analytical methodology were determined for both the shear and normal stress responses of the adhesive bondline. Thus, the semi-analytical methodology was successfully verified using the ABAQUS finite element software and a single-lap joint configuration subjected to pure bending.

Theoretical study of corrugated plates: Shearing of a trapezoidally corrugated plate with trough lines permitted to curve

NASA Technical Reports Server (NTRS)

Lin, C.; Libove, C.

1971-01-01

A theoretical analysis is presented of the elastic shearing of a trapezoidally corrugated plate with discrete attachments at the ends of the corrugations. Numerical results on effective shear stiffness, stresses, and displacements are presented for selected geometries and end-attachment conditions. It is shown that the frame-like deformation of the cross-sections, which results from the absence of continuous end attachments, can lead to large transverse bending stresses and large reductions in shearing stiffness.

Strength evaluation test of pressureless-sintered silicon nitride at room temperature

NASA Technical Reports Server (NTRS)

Matsusue, K.; Takahara, K.; Hashimoto, R.

1984-01-01

In order to study strength characteristics at room temperature and the strength evaluating method of ceramic materials, the following tests were conducted on pressureless sintered silicon nitride specimens: bending tests, the three tensile tests of rectangular plates, holed plates, and notched plates, and spin tests of centrally holed disks. The relationship between the mean strength of specimens and the effective volume of specimens are examined using Weibull's theory. The effect of surface grinding on the strength of specimens is discussed.

Plate and butt-weld stresses beyond elastic limit, material and structural modeling

NASA Technical Reports Server (NTRS)

Verderaime, V.

1991-01-01

Ultimate safety factors of high performance structures depend on stress behavior beyond the elastic limit, a region not too well understood. An analytical modeling approach was developed to gain fundamental insights into inelastic responses of simple structural elements. Nonlinear material properties were expressed in engineering stresses and strains variables and combined with strength of material stress and strain equations similar to numerical piece-wise linear method. Integrations are continuous which allows for more detailed solutions. Included with interesting results are the classical combined axial tension and bending load model and the strain gauge conversion to stress beyond the elastic limit. Material discontinuity stress factors in butt-welds were derived. This is a working-type document with analytical methods and results applicable to all industries of high reliability structures.

Experimental method for determination of bending and torsional rigidities of advanced composite laminates

DOE Office of Scientific and Technical Information (OSTI.GOV)

Maeda, Takenori

1995-11-01

This paper presents an experimental method for the determination of the bending and torsional rigidities of advanced fiber composite laminates with the aid of laser holographic interferometry. The proposed method consists of a four-point bending test and a resonance test. The bending rigidity ratio (D{sub 12}/D{sub 22}) can be determined from the fringe patterns of the four-point bending test. The bending rigidities (D{sub 11} and D{sub 22}) and the torsional rigidity (D{sub 66}) are calculated from the natural frequencies of cantilever plates of the resonance test. The test specimens are carbon/epoxy cross-ply laminates. The adequacy of the experimental method ismore » confirmed by comparing the measured rigidities with the theoretical values obtained from classical lamination theory (CLT) by using the measured tensile properties. The results show that the present method can be used to evaluate the rigidities of orthotropic laminates with reasonably good accuracy.« less

A nonlinear theory for elastic plates with application to characterizing paper properties

Treesearch

M. W. Johnson; Thomas J. Urbanik

1984-03-01

A theory of thin plates which is physically as well as kinematically nonlinear is, developed and used to characterize elastic material behavior for arbitrary stretching and bending deformations. It is developed from a few clearly defined assumptions and uses a unique treatment of strain energy. An effective strain concept is introduced to simplify the theory to a...

Development of U-frame bending system for studying the vibration integrity of spent nuclear fuel

NASA Astrophysics Data System (ADS)

Wang, Hong; Wang, Jy-An John; Tan, Ting; Jiang, Hao; Cox, Thomas S.; Howard, Rob L.; Bevard, Bruce B.; Flanagan, Michelle

2013-09-01

A bending fatigue system developed to evaluate the response of spent nuclear fuel rods to vibration loads is presented. A U-frame testing setup is used for imposing bending loads on the fuel rod specimen. The U-frame setup consists of two rigid arms, side connecting plates to the rigid arms, and linkages to a universal testing machine. The test specimen's curvature is obtained through a three-point deflection measurement method. The tests using surrogate specimens with stainless steel cladding revealed increased flexural rigidity under unidirectional cyclic bending, significant effect of cladding-pellets bonding on the response of surrogate rods, and substantial cyclic softening in reverse bending mode. These phenomena may cast light on the expected response of a spent nuclear fuel rod. The developed U-frame system is thus verified and demonstrated to be ready for further pursuit in hot-cell tests.

The Effect of Basis Selection on Static and Random Acoustic Response Prediction Using a Nonlinear Modal Simulation

NASA Technical Reports Server (NTRS)

Rizzi, Stephen A.; Przekop, Adam

2005-01-01

An investigation of the effect of basis selection on geometric nonlinear response prediction using a reduced-order nonlinear modal simulation is presented. The accuracy is dictated by the selection of the basis used to determine the nonlinear modal stiffness. This study considers a suite of available bases including bending modes only, bending and membrane modes, coupled bending and companion modes, and uncoupled bending and companion modes. The nonlinear modal simulation presented is broadly applicable and is demonstrated for nonlinear quasi-static and random acoustic response of flat beam and plate structures with isotropic material properties. Reduced-order analysis predictions are compared with those made using a numerical simulation in physical degrees-of-freedom to quantify the error associated with the selected modal bases. Bending and membrane responses are separately presented to help differentiate the bases.

Proximal humerus fractures: a comparative biomechanical analysis of intra and extramedullary implants.

PubMed

Füchtmeier, B; May, R; Hente, R; Maghsudi, M; Völk, M; Hammer, J; Nerlich, M; Prantl, L

2007-08-01

The biomechanical stability of a newly developed humerus nail (Sirustrade mark) for the treatment of fractures of the proximal humerus was analyzed in comparison to established systems. In total, three randomized groups were formed (n = 4 pairs) from 12 matched pairs of human cadaver humeri. All intact bones were mechanically characterized by five subsequent load cycles under bending and torsional loading. The bending moment at the osteotomy was 7.5 N m the torsional moment was 8.3 N m over the hole specimen length. Loading was consistently initiated at the distal epiphysis and the deformation at the distal epiphysis was continuously recorded. Prior to implant reinforcement, a defect of 5 mm was created to simulate an unstable subcapital humerus fracture. For paired comparison, one humerus of each pair was stabilized with the Sirus proximal humerus nail while the counterpart was stabilized by a reference implant. In detail, the following groups were created: Sirus versus Proximal humerus nail (PHN) with spiral blade (group I); Sirus versus PHILOS plate (group II); Sirus versus 4.5 mm AO T-plate (group III). The Sirus nail demonstrated significantly higher stiffness values compared to the reference implants for both bending and torsional loading. The following distal epiphyseal displacements were recorded for a bending moment of 7.5 N m at the osteotomy: Sirus I: 8.8 mm, II: 8.4 mm, III: 7.7 mm (range 6.9-10.9), PHN 21.1 mm (range 15.7-25.2) (P = 0.005), PHILOS plate 27.5 mm (range 21.6-35.8) (P < 0.001), 4.5 AO T-plate 26.3 mm (range 24.3-33.9) (P = 0.01). The rotations corresponding to 8.3 N m torsional moment were: Sirus I: 9.1 degrees , II: 9.3 degrees , III: 10.6 degrees (range 7.5-12.2), PHN 13.5 degrees (range 10.3-15.6) (P = 0.158), PHILOS plate 15.6 degrees (range 13.7-20.8) (P = 0.007), 4.5 AO T-Platte 14.1 degrees (range 11.5-19.7) (P = 0.158). The intramedullary load carriers were biomechanically superior when compared to the plating systems in the fracture model presented here. Supplementary, the Sirus Nail showed higher stiffness values than the PHN. However, the latter are gaining in importance due to the possibility of minimal invasive implantation. Whether this will be associated with functional advantages requires further clinical investigation.

High-speed measurements of steel-plate deformations during laser surface processing.

PubMed

Jezersek, Matija; Gruden, Valter; Mozina, Janez

2004-10-04

In this paper we present a novel approach to monitoring the deformations of a steel plate's surface during various types of laser processing, e.g., engraving, marking, cutting, bending, and welding. The measuring system is based on a laser triangulation principle, where the laser projector generates multiple lines simultaneously. This enables us to measure the shape of the surface with a high sampling rate (80 Hz with our camera) and high accuracy (+/-7 microm). The measurements of steel-plate deformations for plates of different thickness and with different illumination patterns are presented graphically and in an animation.

Crack problems for a rectangular plate and an infinite strip

NASA Technical Reports Server (NTRS)

Civelek, M. B.; Erdogan, F.

1980-01-01

The general plane problem for an infinite strip containing multiple cracks perpendicular to its boundaries is considered. The problem is reduced to a system of singular integral equations. Two specific problems of practical interest are then studied in detail. The first problem explores the interaction effect of multiple edge cracks in a plate or beam under tension or bending. The second problem is that of a rectangular plate containing an arbitrarily oriented crack in the plane of symmetry. Particular emphasis is placed on the problem of a plate containing an edge crack and subjected to concentrated forces.

An elastic-perfectly plastic analysis of the bending of the lithosphere at a trench

NASA Technical Reports Server (NTRS)

Turcotte, D. L.; Mcadoo, D. C.; Caldwell, J. G.

1978-01-01

A number of authors have modeled the flexure of the lithosphere at an oceanic trench using a thin elastic plate with a hydrostatic restoring force. In some cases good agreement with observed topography is obtained but in other cases the slope of the lithosphere within the trench is greater than that predicted by the elastic theory. In this paper the bending of a thin plate is considered using an elastic-perfectly plastic rheology. It is found that the lithosphere behaves elastically seaward of the trench, but that plasticity decreases the radius of curvature within the trench. The results are compared with a number of observed trench profiles. The elastic-perfectly plastic profiles are in excellent agreement with those profiles that deviate from elastic behavior.

Bending of Rectangular Plates with Large Deflections

NASA Technical Reports Server (NTRS)

Levy, Samuel

1942-01-01

The solution of von Karman's fundamental equations for large deflections of plates is presented for the case of a simply supported rectangular plate under combined edge compression and lateral loading. Numerical solutions are given for square plates and for rectangular plates with a width-span ratio of 3:1. The effective widths under edge compression are compared with effective widths according to von Karman, Bengston, Marguerre, and Cox and with experimental results by Ramberg, McPherson, and Levy. The deflections for a square plate under lateral pressure are compared with experimental and theoretical results by Kaiser. It is found that the effective widths agree closely with Marguerre's formula and with the experimentally observed values and that the deflections agree with the experimental results and with Kaiser's work.

Fabrication of mandible fracture plate by indirect additive manufacturing

NASA Astrophysics Data System (ADS)

Aizat, M.; Khan, S. F.

2017-10-01

Bone fracture is a serious skeletal injury due to accidents and fragility of the bones at a certain age. In order to accelerate fracture healing process, fracture bone plate is use to hold the fracture segment for more stability. The purpose of this study is to fabricate mandibular fracture plate by using indirect additive manufacturing methods in order to reduce time taken during bending and shaping the fracture fixation plate that conform to the anatomy of the fractured bone site. The design and analysis of the plates are performed using CATIA and ANSYS software. The 3D-CAD data were sent to an additive manufacturing machine (fused filament fabricated) to generate master pattern using PLA and the mould were fabricated using Plaster of Paris. A melt ZAMAK 3 was poured directly into the moulds, and left it until completely harden. 3point bending test was performed on the prototype plate using universal testing machine. Stress-strain curve shows the graph exhibited a linear relationship of stress-strain up to a strain value of 0.001. Specimens give a maximum yielding stress and then break before the conventional deflection. Since the maximum flexural stress and the breaking stress are far apart with a plateau stating at strain value of 0.003mm/mm in most specimens, the specimen’s failure types are considered plastic failure mode. The average thickness and width are 1.65mm and 2.18mm respectively. The flexural modulus and flexural strength are 189.5GPa and 518.1MPa, respectively.

Assessment of the apparent bending stiffness and damping of multilayer plates; modelling and experiment

NASA Astrophysics Data System (ADS)

Ege, Kerem; Roozen, N. B.; Leclère, Quentin; Rinaldi, Renaud G.

2018-07-01

In the context of aeronautics, automotive and construction applications, the design of light multilayer plates with optimized vibroacoustical damping and isolation performances remains a major industrial challenge and a hot topic of research. This paper focuses on the vibrational behavior of three-layered sandwich composite plates in a broad-band frequency range. Several aspects are studied through measurement techniques and analytical modelling of a steel/polymer/steel plate sandwich system. A contactless measurement of the velocity field of plates using a scanning laser vibrometer is performed, from which the equivalent single layer complex rigidity (apparent bending stiffness and apparent damping) in the mid/high frequency ranges is estimated. The results are combined with low/mid frequency estimations obtained with a high-resolution modal analysis method so that the frequency dependent equivalent Young's modulus and equivalent loss factor of the composite plate are identified for the whole [40 Hz-20 kHz] frequency band. The results are in very good agreement with an equivalent single layer analytical modelling based on wave propagation analysis (model of Guyader). The comparison with this model allows identifying the frequency dependent complex modulus of the polymer core layer through inverse resolution. Dynamical mechanical analysis measurements are also performed on the polymer layer alone and compared with the values obtained through the inverse method. Again, a good agreement between these two estimations over the broad-band frequency range demonstrates the validity of the approach.

Biomechanical Comparison Study of Three Fixation Methods for Proximal Chevron Osteotomy of the First Metatarsal in Hallux Valgus.

PubMed

Kim, Jin Su; Cho, Hun Ki; Young, Ki Won; Kim, Ji Soo; Lee, Kyung Tai

2017-12-01

Fixation of proximal chevron metatarsal osteotomy has been accomplished using K-wires traditionally and with a locking plate recently. However, both methods have many disadvantages. Hence, we developed an intramedullary fixation technique using headless cannulated screws and conducted a biomechanical study to evaluate the superiority of the technique to K-wire and locking plate fixations. Proximal chevron metatarsal osteotomy was performed on 30 synthetic metatarsal models using three fixation techniques. Specimens in group I were fixated with K-wires (1.6 mm × 2) and in group II with headless cannulated screws (3.0 mm × 2) distally through the intramedullary canal. Specimens in group III were fixated with a locking X-shaped plate (1.3-mm thick) and screws (2.5 mm × 4). Eight metatarsal specimens were selected from each group for walking fatigue test. Bending stiffness and dorsal angulation were measured by 1,000 repetitions of a cantilever bending protocol in a plantar to dorsal direction. The remaining two samples from each group were subjected to 5 mm per minute axial loading to assess the maximal loading tolerance. All samples in group I failed walking fatigue test while group II and group III tolerated the walking fatigue test. Group II showed greater resistance to bending force and smaller dorsal angulation than group III ( p = 0.001). On the axial loading test, group I and group II demonstrated superior maximum tolerance to group III (54.8 N vs. 47.2 N vs. 28.3 N). Authors have demonstrated proximal chevron metatarsal osteotomy with intramedullary screw fixation provides superior biomechanical stability to locking plate and K-wire fixations. The new technique using intramedullary screw fixation can offer robust fixation and may lead to better outcomes in surgical treatment of hallux valgus.

Biomechanical Assessment of Locked Plating for the Fixation of Patella Fractures.

PubMed

Wurm, Simone; Augat, Peter; Bühren, Volker

2015-09-01

To analyze the mechanical stability of locked plating in comparison with tension-band wiring for the fixation of fractures of the patella. Biomechanical tests were performed on artificial foam patella specimens comparing an angular stable plate and monocortical screws with tension-band wiring. Tests were performed under combined tension and bending until failure simulating physiological loading of the tibia during walking. Tension-band wiring failed at 66% of the failure load of plating (1052 N, P = 0.002) and had 5 times larger fracture gap displacements (P = 0.002). Based on the biomechanical advantages, locked plating of the patella may constitute a reasonable alternative in the treatment of patella fractures.

Finite element beam flexural properties of cement composites of fiber reinforced PVA

NASA Astrophysics Data System (ADS)

Yang, Chengzhi; Pei, Changchun

2018-05-01

In this paper, the initial cracking state and the mid span bending moment and deflection of ECC beam under different PVA fiber and fly ash mixing rate are studied by finite element simulation analysis. The results show that the bending moment of the ECC beam increases with the increase of the PVA fiber content, and the deflection decreases. When the ratio of PVA fiber is 1.5%, the middle bending moment is the largest and the deflection is the least. With the increase of fly ash content, the mid span bending moment of ECC beam increases first and then decreases. When the fly ash ratio is 60%, the middle bending moment is the largest and the deflection is the least. Through the study, the formula for calculating the flexural capacity of the cross section suitable for ECC beams is derived.

The mechanical and morphological properties of bone beneath internal fixation plates of differing rigidity.

PubMed

Claes, L

1989-01-01

The internal fixation of diaphyseal fractures by bone plates is a well recognized treatment. The normal physiological stress of bone is reduced by plates that cause a negative balance of bone-remodeling processes. Many investigators have shown that the degree of stress protection is dependent on the rigidity of the plates. It was the aim of this study to quantify mechanical and morphological changes at different locations in a plated diaphyseal bone as a function of differing plate rigidity. Two types of plates with the same size but different materials were used. The stainless steel plates had a modulus of elasticity and bending stiffness 3.2 times higher than the carbon fiber reinforced carbon plates. Both types of plates were applied to the intact right and left femora of six foxhounds for 6 months. The stiffer stainless steel plates led to a significantly higher bone loss and correspondingly greater loss of mechanical properties. These effects were greatest directly beneath the plate and less with increasing distance from the plate.

Ductile-Phase-Toughened Tungsten for Plasma-Facing Materials

NASA Astrophysics Data System (ADS)

Cunningham, Kevin Hawkins

A variety of processing approaches were employed to fabricate ductile-phase-toughened (DPT) tungsten (W) composites. Mechanical testing and analytical modeling were used to guide composite development. This work provides a basis for further development of W composites to be used in structural divertor components of future fusion reactors. W wire was tested in tension, showing significant ductility and strength. Coatings of copper (Cu) or tungsten carbide (WC) were applied to the W wire via electrodeposition and carburization, respectively. Composites were fabricated using spark plasma sintering (SPS) to consolidate W powders together with each type of coated W wire. DPT behavior, e.g. crack arrest and crack bridging, was not observed in three-point bend testing of the sintered composites. A laminate was fabricated by hot pressing W and Cu foils together with W wires, and subsequently tested in tension. This laminate was bonded via hot pressing to thick W plate as a reinforcing layer, and the composite was tested in three-point bending. Crack arrest was observed along with some fiber pullout, but significant transverse cracking in the W plate confounded further fracture toughness analysis. The fracture toughness of thin W plate was measured in three-point bending. W plates were brazed with Cu foils to form a laminate. Crack arrest and crack bridging were observed in three-point bend tests of the laminate, and fracture resistance curves were successfully calculated for this DPT composite. An analytical model of crack bridging was developed using the basis described by Chao in previous work by the group. The model uses the specimen geometry, matrix properties, and the stress-displacement function of a ductile reinforcement ("bridging law") to calculate the fracture resistance curve (R-curve) and load-displacement curve (P-D curve) for any test specimen geometry. The code was also implemented to estimate the bridging law of an arbitrary composite using R-curve data. Finally, a parametric study was performed to quantitatively determine the necessary mechanical properties of useful toughening reinforcements for a DPT W composite. The analytical model has a broad applicability for any DPT material.

Characterization of Thick Glass Reinforced Composites

DTIC Science & Technology

1992-07-01

24 ounces per square yard. The matrices were different polyester resin systems from American Cyanamid and Owens Corning . Specimen thicknesses ranged...fab- ricated similar size plates using the American Cyanamid resin. The Owens Corning plates con- tained 53% volume fraction fiber while the American...thicknesses for the Owens Corning and four for the American Cyanamid. Specimens were loaded in three point bending at a displacement rate that was changed

NUCLEAR REACTOR FUEL ELEMENT

DOEpatents

Wheelock, C.W.; Baumeister, E.B.

1961-09-01

A reactor fuel element utilizing fissionable fuel materials in plate form is described. This fuel element consists of bundles of fuel-bearing plates. The bundles are stacked inside of a tube which forms the shell of the fuel element. The plates each have longitudinal fins running parallel to the direction of coolant flow, and interspersed among and parallel to the fins are ribs which position the plates relative to each other and to the fuel element shell. The plate bundles are held together by thin bands or wires. The ex tended surface increases the heat transfer capabilities of a fuel element by a factor of 3 or more over those of a simple flat plate.

Biomechanical Evaluation of the CD HORIZON Spire Z Spinal System With Pedicle and Facet Fixation.

PubMed

Godzik, Jakub; Kalb, Samuel; Martinez-Del-Campo, Eduardo; Newcomb, Anna G U S; Singh, Vaneet; Walker, Corey T; Chang, Steve W; Kelly, Brian P; Crawford, Neil R

2016-08-01

Human cadaveric biomechanical study. The aim of this study was to evaluate the biomechanics of lumbar motion segments instrumented with the CD HORIZON Spire Z plate system (Spire Z), a posterior supplemental fixation spinous process plate, alone and with additional fixation systems. Plates and pedicle screw/rod and facet screw implants are adjuncts to fusion. The plate limits motion, improving segmental stability and the fusion microenvironment. However, the degree to which the plate contributes to overall stability when used alone or in conjunction with additional instrumentation has not been described. Standard nondestructive flexibility tests were performed in 7 L2-L5 human cadaveric spines. Spinal stability was determined as mean range of motion (ROM) in flexion/extension, lateral bending, and axial rotation. Paired comparisons were made between five conditions: (1) intact/control; (2) Spire Z; (3) Spire Z with unilateral pedicle screw/rod system (Spire Z+UPS); (4) Spire Z with unilateral facet screw system (Spire Z+UFS); and (5) Spire Z with bilateral facet screw system (Spire Z+BFS). Stiffness and ROM data were compared using one-way analysis of variance, followed by repeated-measures Holm-Šidák tests. Spire Z was most effective in limiting flexion (20% of normal) and extension (24% of normal), but less effective in reducing lateral bending and axial rotation. In lateral bending, Spire Z+BFS and Spire Z+UPS constructs were not significantly different and demonstrated greater ROM reduction compared with Spire Z+UFS and Spire Z (P < 0.001). Spire Z+BFS demonstrated greatest stiffness in axial rotation compared with Spire Z+UPS (P = 0.025), Spire Z+UFS (P = 0.001), and Spire Z (P < 0.001). Spire Z+UPS was not significantly different from Spire Z+UFS (P = 0.21), and superior to Spire Z (P = 0.013). The Spire Z spinous process plate provides excellent immediate fixation, particularly for flexion and extension. While the hybrid Spire Z+BFS screw construct afforded the greatest stability, Spire Z+UPS demonstrated considerable promise. N/A.

Hotspot motion caused the Hawaiian-Emperor Bend and LLSVPs are not fixed

NASA Astrophysics Data System (ADS)

Tarduno, J. A.; Bono, R. K.

2017-12-01

Paleomagnetic study of volcanic rocks remains the gold standard on which to assess hotspot motion, true polar wander and plate motion recorded by oceanic plates. There is remarkable consistency between paleomagnetic results from basaltic lavas recovered by ocean drilling of the Emperor seamounts, and independent predictions of plate circuits. Both reveal greater than 40 mm/yr of southward hotspot motion; thus the dominant reason for the distinct bend morphology the Hawaiian-Emperor track is hotspot motion rather than plate motion. These findings provide the motivation for moving beyond hotspot fixity to understand mantle processes responsible for the observed motions. Global analyses as well as comparisons between the Hawaiian-Emperor and Louisville tracks indicate only a minor (if any) role for true polar wander. Two viable, non-mutually exclusive processes to explain the observed Hawaiian plume motion are: i. plume-ridge and ii plume-LLSVP interaction. Here we further explore these issues by paleomagnetic analyses of basalts from the Cenozoic Hawaiian chain and Late Cretaceous basalts of the southernmost Pacific Plate. The latter yield paleolatitudes consistent with those from the northern Pacific, indicating that long-standing non-dipole fields cannot have been large enough to affect conclusions on hotspot drift. Data from the former suggest some relative motions between the LLSVPs on tens-of-millions of year time scales, which probably record the continual reshaping of these provinces by plume motion in the lower mantle.

Shear-lag analysis about an internally-dropped ply

DOE Office of Scientific and Technical Information (OSTI.GOV)

Vizzini, A.J.

1995-12-31

The region around a terminated ply is modeled as several elastic layers separated by shear regions. A shear-lag analysis is then performed allowing for the thickness of the elastic and shear layers to vary. Boundary conditions, away for the ply drop, are based on the deflections determined by a finite element model. The interlaminar stresses are compared against those generated by the finite element model for tapered laminates under pure extension, pure bending, and extension-bending coupling. The shear-lag analysis predicts the interlaminar shear at and near the ply drop for pure extension and in cases involving bending if the deflectionsmore » due to bending are removed. The interlaminar shear stress and force equilibrium are used to determine the interlaminar normal stress. The trends in the interlaminar normal stress shown by the finite element model are partially captured by the shear-lag analysis. This simple analysis indicates that the mechanism for load transfer about a ply drop is primarily due to shear transfer through the resin rich areas.« less

Rapid exhumation of Cretaceous arc-rocks along the Blue Mountains restraining bend of the Enriquillo-Plantain Garden fault, Jamaica, using thermochronometry from multiple closure systems

NASA Astrophysics Data System (ADS)

Cochran, William J.; Spotila, James A.; Prince, Philip S.; McAleer, Ryan J.

2017-11-01

The effect of rapid erosion on kinematic partitioning along transpressional plate margins is not well understood, particularly in highly erosive climates. The Blue Mountains restraining bend (BMRB) of eastern Jamaica, bound to the south by the left-lateral Enriquillo-Plantain Garden fault (EPGF), offers an opportunity to test the effects of highly erosive climatic conditions on a 30-km-wide restraining bend system. No previous thermochronometric data exists in Jamaica to describe the spatial or temporal pattern of rock uplift and how oblique (> 20°) plate motion is partitioned into vertical strain. To define the exhumation history, we measured apatite (n = 10) and zircon (n = 6) (U-Th)/He ages, 40Ar/39Ar (n = 2; amphibole and K-spar) ages, and U/Pb zircon (n = 2) crystallization ages. Late Cretaceous U/Pb and 40Ar/39Ar ages (74-68 Ma) indicate rapid cooling following shallow emplacement of plutons during north-south subduction along the Great Caribbean Arc. Early to middle Miocene zircon helium ages (19-14 Ma) along a vertical transect suggest exhumation and island emergence at 0.2 mm/yr. Older zircon ages 10-15 km to the north (44-35 Ma) imply less rock uplift. Apatite helium ages are young (6-1 Ma) across the entire orogen, suggesting rapid exhumation of the BMRB since the late Miocene. These constraints are consistent with previous reports of restraining bend formation and early emergence of eastern Jamaica. An age-elevation relationship from a vertical transect implies an exhumation rate of 0.8 mm/yr, while calculated closure depths and thermal modeling suggests exhumation as rapid as 2 mm/yr. The rapid rock uplift rates in Jamaica are comparable to the most intense transpressive zones worldwide, despite the relatively slow (5-7 mm/yr) strike-slip rate. We hypothesize highly erosive conditions in Jamaica enable a higher fraction of plate motion to be accommodated by vertical deformation. Thus, strike-slip restraining bends may evolve differently depending on erosivity and local climate.

Rapid exhumation of Cretaceous arc-rocks along the Blue Mountains restraining bend of the Enriquillo-Plantain Garden fault, Jamaica, using thermochronometry from multiple closure systems

USGS Publications Warehouse

Cochran, William J.; Spotila, James A.; Prince, Philip S.; McAleer, Ryan J.

2017-01-01

The effect of rapid erosion on kinematic partitioning along transpressional plate margins is not well understood, particularly in highly erosive climates. The Blue Mountains restraining bend (BMRB) of eastern Jamaica, bound to the south by the left-lateral Enriquillo-Plantain Garden fault (EPGF), offers an opportunity to test the effects of highly erosive climatic conditions on a 30-km-wide restraining bend system. No previous thermochronometric data exists in Jamaica to describe the spatial or temporal pattern of rock uplift and how oblique (> 20°) plate motion is partitioned into vertical strain. To define the exhumation history, we measured apatite (n = 10) and zircon (n = 6) (U-Th)/He ages, 40Ar/39Ar (n = 2; amphibole and K-spar) ages, and U/Pb zircon (n = 2) crystallization ages. Late Cretaceous U/Pb and 40Ar/39Ar ages (74–68 Ma) indicate rapid cooling following shallow emplacement of plutons during north-south subduction along the Great Caribbean Arc. Early to middle Miocene zircon helium ages (19–14 Ma) along a vertical transect suggest exhumation and island emergence at ~ 0.2 mm/yr. Older zircon ages 10–15 km to the north (44–35 Ma) imply less rock uplift. Apatite helium ages are young (6–1 Ma) across the entire orogen, suggesting rapid exhumation of the BMRB since the late Miocene. These constraints are consistent with previous reports of restraining bend formation and early emergence of eastern Jamaica. An age-elevation relationship from a vertical transect implies an exhumation rate of 0.8 mm/yr, while calculated closure depths and thermal modeling suggests exhumation as rapid as 2 mm/yr. The rapid rock uplift rates in Jamaica are comparable to the most intense transpressive zones worldwide, despite the relatively slow (5–7 mm/yr) strike-slip rate. We hypothesize highly erosive conditions in Jamaica enable a higher fraction of plate motion to be accommodated by vertical deformation. Thus, strike-slip restraining bends may evolve differently depending on erosivity and local climate.

Strongly coupled stress waves in heterogeneous plates.

NASA Technical Reports Server (NTRS)

Wang, A. S. D.; Chou, P. C.; Rose, J. L.

1972-01-01

Consideration of coupled stress waves generated by an impulsive load applied at one end of a semiinfinite plate. For the field equations governing the one-dimensional coupled waves a hyperbolic system of equations is obtained in which a strong coupling in the second derivatives exists. The method of characteristics described by Chou and Mortimer (1967) is extended to cover the case of strong coupling, and a study is made of the transient stress waves in a semiinfinite plate subjected to an initial step input. Coupled discontinuity fronts are found to propagate at different velocities. The normal plate stress and the bending moment at different time regimes are illustrated by graphs.

Analogies between Kirchhoff plates and functionally graded Saint-Venant beams under torsion

NASA Astrophysics Data System (ADS)

Barretta, Raffaele; Luciano, Raimondo

2015-05-01

Exact solutions of elastic Kirchhoff plates are available only for special geometries, loadings and kinematic boundary constraints. An effective solution procedure, based on an analogy between functionally graded orthotropic Saint-Venant beams under torsion and inhomogeneous isotropic Kirchhoff plates, with no kinematic boundary constraints, is proposed. The result extends the one contributed in Barretta (Acta Mech 224(12):2955-2964, 2013) for the special case of homogeneous Saint-Venant beams under torsion. Closed-form solutions for displacement, bending-twisting moment and curvature fields of an elliptic plate, corresponding to a functionally graded orthotropic beam, are evaluated. A new benchmark for computational mechanics is thus provided.

Numerical and experimental investigation on static electric charge model at stable cone-jet region

NASA Astrophysics Data System (ADS)

Hashemi, Ali Reza; Pishevar, Ahmad Reza; Valipouri, Afsaneh; Pǎrǎu, Emilian I.

2018-03-01

In a typical electro-spinning process, the steady stretching process of the jet beyond the Taylor cone has a significant effect on the dimensions of resulting nanofibers. Also, it sets up the conditions for the onset of the bending instability. The focus of this work is the modeling and simulation of the initial stable jet phase seen during the electro-spinning process. The perturbation method was applied to solve hydrodynamic equations, and the electrostatic equation was solved by a boundary integral method. These equations were coupled with the stress boundary conditions derived appropriate at the fluid-fluid interface. Perturbation equations were discretized by the second-order finite difference method, and the Newton method was implemented to solve the discretized nonlinear system. Also, the boundary element method was utilized to solve the electrostatic equation. In the theoretical study, the fluid is described as a leaky dielectric with charges only on the jet surface in dielectric air. In this study, electric charges were modeled as static. Comparison of numerical and experimental results shows that at low flow rates and high electric field, good agreement was achieved because of the superior importance of the charge transport by conduction rather than convection and charge concentration. In addition, the effect of unevenness of the electric field around the nozzle tip was experimentally studied through plate-plate geometry as well as point-plate geometry.

An improved plate theory of order (1,2) for thick composite laminates

NASA Technical Reports Server (NTRS)

Tessler, A.

1992-01-01

A new (1,2)-order theory is proposed for the linear elasto-static analysis of laminated composite plates. The basic assumptions are those concerning the distribution through the laminate thickness of the displacements, transverse shear strains and the transverse normal stress, with these quantities regarded as some weighted averages of their exact elasticity theory representations. The displacement expansions are linear for the inplane components and quadratic for the transverse component, whereas the transverse shear strains and transverse normal stress are respectively quadratic and cubic through the thickness. The main distinguishing feature of the theory is that all strain and stress components are expressed in terms of the assumed displacements prior to the application of a variational principle. This is accomplished by an a priori least-square compatibility requirement for the transverse strains and by requiring exact stress boundary conditions at the top and bottom plate surfaces. Equations of equilibrium and associated Poisson boundary conditions are derived from the virtual work principle. It is shown that the theory is particularly suited for finite element discretization as it requires simple C(sup 0)- and C(sup -1)-continuous displacement interpolation fields. Analytic solutions for the problem of cylindrical bending are derived and compared with the exact elasticity solutions and those of our earlier (1,2)-order theory based on the assumed displacements and transverse strains.

Vortex shedding experiment with flat and curved bluff plates in water

NASA Technical Reports Server (NTRS)

Reed, D.; Nesman, T.; Howard, P.

1988-01-01

Vortex shedding experiments were conducted in a water flow facility in order to simulate the strong discrete 4000-Hz vibration detected in the Space Shuttle Main Engine (SSME) which is thought to be associated with the SSME LOX inlet tee splitter vanes on the Main Injector. For the case of a flat vane with a blunt trailing edge excited by flow induced vortex shedding, lock-in with the first bending mode of the plate was observed. A curved vane displayed similar behavior, with the lock-in being a more discrete higher amplitude response. Aluminum vanes were employed to decouple the first vane bending mode from the vortex shedding mode. The application of an asymmetric 30-deg trailing edge bevel to both the flat and curved vanes was found to greatly reduce the strength of the shed vortices.

Material nonlinear analysis via mixed-iterative finite element method

NASA Technical Reports Server (NTRS)

Sutjahjo, Edhi; Chamis, Christos C.

1992-01-01

The performance of elastic-plastic mixed-iterative analysis is examined through a set of convergence studies. Membrane and bending behaviors are tested using 4-node quadrilateral finite elements. The membrane result is excellent, which indicates the implementation of elastic-plastic mixed-iterative analysis is appropriate. On the other hand, further research to improve bending performance of the method seems to be warranted.

Bending and Force Recovery in Polymer Films and Microgel Formation

NASA Astrophysics Data System (ADS)

Elder, Theresa Marie

To determine correlation between geometry and material three different model films: polymethylsiloxane (PDMS), polystyrene (PS), and polycarbonate (PC), were singly bent and doubly bent (forming D-cones). Bends were chosen as they are fundamental in larger complex geometries such as origami and crumples. Bending was carried out between two plates taking force and displacement measurements. Processing of data using moment equations yielded values for bending moduli for studied films that were close to accepted values. Force recovery showed logarithmic trends for PDMS and stretched exponential trends for PS and PC. In a separate experiment a triblock copolymer of polystyrene-polyacrylic acid-polystyrene was subjected to different good and bad solvent mixing with any resulting particle morphology examined. Particles formed more uniformly with high water concentration, particles formed with high toluene concentration and agitation yielded three separate morphologies.

Elastic Moduli of Pyrolytic Boron Nitride Measured Using 3-Point Bending and Ultrasonic Testing

NASA Technical Reports Server (NTRS)

Kaforey, M. L.; Deeb, C. W.; Matthiesen, D. H.; Roth, D. J.

1999-01-01

Three-point bending and ultrasonic testing were performed on a flat plate of PBN. In the bending experiment, the deformation mechanism was believed to be shear between the pyrolytic layers, which yielded a shear modulus, c (sub 44), of 2.60 plus or minus .31 GPa. Calculations based on the longitudinal and shear wave velocity measurements yielded values of 0.341 plus or minus 0.006 for Poisson's ratio, 10.34 plus or minus .30 GPa for the elastic modulus (c (sub 33)), and 3.85 plus or minus 0.02 GPa for the shear modulus (c (sub 44)). Since free basal dislocations have been reported to affect the value of c (sub 44) found using ultrasonic methods, the value from the bending experiment was assumed to be the more accurate value.

Analysis of an x-ray mirror made from piezoelectric bimorph

NASA Astrophysics Data System (ADS)

Zhang, Yao; Li, Ming; Tang, Shanzhi; Gao, Junxiang; Zhang, Weiwei; Zhu, Peiping

2017-07-01

Theoretical analysis of the mechanical behavior of an x-ray mirror made from piezoelectric bimorph is presented. A complete two-dimensional relationship between the radius of curvature of the mirror and the applied voltage is derived. The accuracy of this relationship is studied by comparing the figures calculated by the relationship and Finite Element Analysis. The influences of several critical parameters in the relationship on the radius of curvature are analyzed. It is found that piezoelectric coefficient d31 is the main material property parameter that dominates the radius of curvature, and that the optimal thickness of PZT plate corresponding to largest bending range is 2.5 times of that of faceplate. It is demonstrated that the relationship is helpful for us to complete the primary design of the x-ray mirror made from piezoelectric bimorph.

Repeated unit cell (RUC) approach for pure bending analysis of coronary stents.

PubMed

Ju, Feng; Xia, Zihui; Zhou, Chuwei

2008-08-01

Flexibility is one of the key properties of coronary stents. The objective of this paper is to characterize the bending behaviour of stents through finite element analysis with repeated unit cell (RUC) models. General periodic boundary conditions for the RUC under the pure bending condition are formulated. It is found that the proposed RUC approach can provide accurate numerical results of bending behaviour of stents with much less computational costs. Bending stiffness, post-yield bending behaviour and the relationship between moment and bending curvature are investigated for Palmaz-Schatz stents and stents with the V- and S-shaped links. It is found that the effect of link geometry on the bending behaviour of stent is significant. The behaviour of stents subjected to cyclic bending is also investigated.

Nonlinear Structural Analysis of an Icosahedron and its Application to Lighter than Air Vehicles under a Vacuum

DTIC Science & Technology

2014-03-27

bending [45, 402], assuming the vertical deflection takes the form: w = wo ( 1 + r2c a2c )2 (2.28) 9A.C. Ugural has a plate solution for equilateral...science/article/pii/S0096300308000982. [49] Ugural , A.C. Stresses in Plates and Shells. McGraw-Hill, 1981. ISBN 0-07-065730-0. [50] US Centennial of Flight

Contact Modelling of Large Radius Air Bending with Geometrically Exact Contact Algorithm

NASA Astrophysics Data System (ADS)

Vorkov, V.; Konyukhov, A.; Vandepitte, D.; Duflou, J. R.

2016-08-01

Usage of high-strength steels in conventional air bending is restricted due to limited bendability of these metals. Large-radius punches provide a typical approach for decreasing deformations during the bending process. However, as deflection progresses the loading scheme changes gradually. Therefore, modelling of the contact interaction is essential for an accurate description of the loading scheme. In the current contribution, the authors implemented a plane frictional contact element based on the penalty method. The geometrically exact contact algorithm is used for the penetration determination. The implementation is done using the OOFEM - open source finite element solver. In order to verify the simulation results, experiments have been conducted on a bending press brake for 4 mm Weldox 1300 with a punch radius of 30 mm and a die opening of 80 mm. The maximum error for the springback calculation is 0.87° for the bending angle of 144°. The contact interaction is a crucial part of large radius bending simulation and the implementation leads to a reliable solution for the springback angle.

Additive manufacturing for microvascular reconstruction of the mandible in 20 patients.

PubMed

Lethaus, Bernd; Poort, Lucas; Böckmann, Roland; Smeets, Ralf; Tolba, Rene; Kessler, Peter

2012-01-01

The aim of this study was to evaluate the use of model mandibles made preoperatively by additive manufacturing, which were used to prebend reconstruction plates prior to mandibular resection and reconstruction with microvascular bony flaps. Computer Tomography (CT) or Cone Beam Tomography (CBT) scans acquired preoperatively were used to obtain DICOM data sets to produce a model of the mandible using rapid prototyping. This model was used as a template to prebend and then sterilize a 2.3 or 2.7 reconstruction plate, which was used to reconstruct the mandible with a microvascular bony flap. This technique was used in 20 consecutive patients who required mandibular resection and reconstruction because of a tumour or osteoradionecrosis. The prebent plate was used in all patients intraoperatively without the need for any further bending. The average time to bend a plate on a nonsterile model was 0.42 h (range 0.25-0.68 h). This is felt to represent the minimum amount of time saved during the operation. Additive manufacture of the mandible prior to resection and reconstruction with a microvascular flap is a useful technique which reduces the operating time. Copyright © 2011 European Association for Cranio-Maxillo-Facial Surgery. Published by Elsevier Ltd. All rights reserved.

Effect of controlled spanwise bending on the stability of the leading-edge vortex

NASA Astrophysics Data System (ADS)

Bhattacharya, Samik; Scofield, Tyler

2017-11-01

When an airfoil is accelerated from rest at a high angle of attack, a leading-edge vortex (LEV) forms, which soon gets destabilized and convects downstream. In this work, we control the spanwise bending of a flat plate wing to actively influence the vorticity transfer from the LEV. Our aim is to investigate the effect of spanwise curvature variation on the geometry, growth, and stability of the LEV during the acceleration phase. A 3D printed flat-plate with a chord of 5 cm and span of 15 cm is towed in a small fish tank at different angles of attack greater than 15°. The plate starts from rest and reaches a Reynolds number of 5000 after travelling different multiples and submultiples of chord-length. We carry out dye-flow visualization and measure the circulation build up and the convection velocity of the LEV with the help of particle image velocimetry (PIV). The unsteady loads coming on to the wing is measured with a force sensor. An analytical scheme for computing the load from the measured displacement of the plate is presented and compared with the force sensor data. Preliminary results indicate that controlled curvature variation can influence the formation and stability of an LEV.

Vibration and bending analyses of magneto-electro-thermo-elastic sandwich microplates resting on viscoelastic foundation

NASA Astrophysics Data System (ADS)

Arefi, Mohammad; Zenkour, Ashraf M.

2017-08-01

Magneto-electro-thermo-mechanical bending and free vibration analysis of a sandwich microplate using strain gradient theory is expressed in this paper. The sandwich plate is made of a core and two integrated piezo-magnetic face sheets. The structure is subjected to electric and magnetic potentials, thermal loadings, and resting on Pasternak's foundation. Electro-magnetic equations are developed by considering the variation form of Hamilton's principle. The effects of important parameters of this problem such as applied electric and magnetic potentials, direct and shear parameter of foundation, three microlength-scale parameters, and two parameters of temperature rising are investigated on the vibration and bending results of problem.

Plate Versus Intramedullary Nail Fixation of Anterior Tibial Stress Fractures: A Biomechanical Study.

PubMed

Markolf, Keith L; Cheung, Edward; Joshi, Nirav B; Boguszewski, Daniel V; Petrigliano, Frank A; McAllister, David R

2016-06-01

Anterior midtibial stress fractures are an important clinical problem for patients engaged in high-intensity military activities or athletic training activities. When nonoperative treatment has failed, intramedullary (IM) nail and plate fixation are 2 surgical options used to arrest the progression of a fatigue fracture and allow bone healing. A plate will be more effective than an IM nail in preventing the opening of a simulated anterior midtibial stress fracture from tibial bending. Controlled laboratory study. Fresh-frozen human tibias were loaded by applying a pure bending moment in the sagittal plane. Thin transverse saw cuts, 50% and 75% of the depth of the anterior tibial cortex, were created at the midtibia to simulate a fatigue fracture. An extensometer spanning the defect was used to measure the fracture opening displacement (FOD) before and after the application of IM nail and plate fixation constructs. IM nails were tested without locking screws, with a proximal screw only, and with proximal and distal screws. Plates were tested with unlocked bicortical screws (standard compression plate) and locked bicortical screws; both plate constructs were tested with the plate edge placed 1 mm from the anterior tibial crest (anterior location) and 5 mm posterior to the crest. For the 75% saw cut depth, the mean FOD values for all IM nail constructs were 13% to 17% less than those for the saw cut alone; the use of locking screws had no significant effect on the FOD. The mean FOD values for all plate constructs were significantly less than those for all IM nail constructs. The mean FOD values for all plates were 28% to 46% less than those for the saw cut alone. Anterior plate placement significantly decreased mean FOD values for both compression and locked plate constructs, but the mean percentage reductions for locked and unlocked plates were not significantly different from each other for either plate placement. The percentage FOD reductions for all plate constructs and the unlocked IM nail were significantly less with a 50% saw cut depth. Plate fixation was superior to IM nail fixation in limiting the opening of a simulated midtibial stress fracture, and anterior-posterior placement of the plate was an important variable for this construct. Results from these tests can help guide the selection of fixation hardware for patients requiring surgical treatment for a midtibial stress fracture. © 2016 The Author(s).

Modelling motions within the organ of Corti

NASA Astrophysics Data System (ADS)

Ni, Guangjian; Baumgart, Johannes; Elliott, Stephen

2015-12-01

Most cochlear models used to describe the basilar membrane vibration along the cochlea are concerned with macromechanics, and often assume that the organ of Corti moves as a single unit, ignoring the individual motion of different components. New experimental technologies provide the opportunity to measure the dynamic behaviour of different components within the organ of Corti, but only for certain types of excitation. It is thus still difficult to directly measure every aspect of cochlear dynamics, particularly for acoustic excitation of the fully active cochlea. The present work studies the dynamic response of a model of the cross-section of the cochlea, at the microscopic level, using the finite element method. The elastic components are modelled with plate elements and the perilymph and endolymph are modelled with inviscid fluid elements. The individual motion of each component within the organ of Corti is calculated with dynamic pressure loading on the basilar membrane and the motions of the experimentally accessible parts are compared with measurements. The reticular lamina moves as a stiff plate, without much bending, and is pivoting around a point close to the region of the inner hair cells, as observed experimentally. The basilar membrane shows a slightly asymmetric mode shape, with maximum displacement occurring between the second-row and the third-row of the outer hair cells. The dynamics responses is also calculated, and compared with experiments, when driven by the outer hair cells. The receptance of the basilar membrane motion and of the deflection of the hair bundles of the outer hair cells is thus obtained, when driven either acoustically or electrically. In this way, the fully active linear response of the basilar membrane to acoustic excitation can be predicted by using a linear superposition of the calculated receptances and a defined gain function for the outer hair cell feedback.

Bending-Tolerant Anodes for Lithium-Metal Batteries.

PubMed

Wang, Aoxuan; Tang, Shan; Kong, Debin; Liu, Shan; Chiou, Kevin; Zhi, Linjie; Huang, Jiaxing; Xia, Yong-Yao; Luo, Jiayan

2018-01-01

Bendable energy-storage systems with high energy density are demanded for conformal electronics. Lithium-metal batteries including lithium-sulfur and lithium-oxygen cells have much higher theoretical energy density than lithium-ion batteries. Reckoned as the ideal anode, however, Li has many challenges when directly used, especially its tendency to form dendrite. Under bending conditions, the Li-dendrite growth can be further aggravated due to bending-induced local plastic deformation and Li-filaments pulverization. Here, the Li-metal anodes are made bending tolerant by integrating Li into bendable scaffolds such as reduced graphene oxide (r-GO) films. In the composites, the bending stress is largely dissipated by the scaffolds. The scaffolds have increased available surface for homogeneous Li plating and minimize volume fluctuation of Li electrodes during cycling. Significantly improved cycling performance under bending conditions is achieved. With the bending-tolerant r-GO/Li-metal anode, bendable lithium-sulfur and lithium-oxygen batteries with long cycling stability are realized. A bendable integrated solar cell-battery system charged by light with stable output and a series connected bendable battery pack with higher voltage is also demonstrated. It is anticipated that this bending-tolerant anode can be combined with further electrolytes and cathodes to develop new bendable energy systems. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Sudden bending of a cracked laminate

NASA Technical Reports Server (NTRS)

Sih, G. C.; Chen, E. P.

1981-01-01

The intensification of stresses near a through crack in the laminate that suddenly undergoes bending is investigated. A dynamic plate theory is developed which includes the effects of material inhomogeneity in the thickness direction and realistic crack edge stress singularity and distribution. Numerical examples indicate that (1) the crack moment intensity tends to decrease as the crack length to laminate thickness is increased, and (2) the average load intensity transmitted to a through crack can be reduced by making the inner layers to be stiffer than the outer layers.

The Effect of Basis Selection on Thermal-Acoustic Random Response Prediction Using Nonlinear Modal Simulation

NASA Technical Reports Server (NTRS)

Rizzi, Stephen A.; Przekop, Adam

2004-01-01

The goal of this investigation is to further develop nonlinear modal numerical simulation methods for prediction of geometrically nonlinear response due to combined thermal-acoustic loadings. As with any such method, the accuracy of the solution is dictated by the selection of the modal basis, through which the nonlinear modal stiffness is determined. In this study, a suite of available bases are considered including (i) bending modes only; (ii) coupled bending and companion modes; (iii) uncoupled bending and companion modes; and (iv) bending and membrane modes. Comparison of these solutions with numerical simulation in physical degrees-of-freedom indicates that inclusion of any membrane mode variants (ii - iv) in the basis affects the bending displacement and stress response predictions. The most significant effect is on the membrane displacement, where it is shown that only the type (iv) basis accurately predicts its behavior. Results are presented for beam and plate structures in the thermally pre-buckled regime.

Motion analysis study on sensitivity of finite element model of the cervical spine to geometry.

PubMed

Zafarparandeh, Iman; Erbulut, Deniz U; Ozer, Ali F

2016-07-01

Numerous finite element models of the cervical spine have been proposed, with exact geometry or with symmetric approximation in the geometry. However, few researches have investigated the sensitivity of predicted motion responses to the geometry of the cervical spine. The goal of this study was to evaluate the effect of symmetric assumption on the predicted motion by finite element model of the cervical spine. We developed two finite element models of the cervical spine C2-C7. One model was based on the exact geometry of the cervical spine (asymmetric model), whereas the other was symmetric (symmetric model) about the mid-sagittal plane. The predicted range of motion of both models-main and coupled motions-was compared with published experimental data for all motion planes under a full range of loads. The maximum differences between the asymmetric model and symmetric model predictions for the principal motion were 31%, 78%, and 126% for flexion-extension, right-left lateral bending, and right-left axial rotation, respectively. For flexion-extension and lateral bending, the minimum difference was 0%, whereas it was 2% for axial rotation. The maximum coupled motions predicted by the symmetric model were 1.5° axial rotation and 3.6° lateral bending, under applied lateral bending and axial rotation, respectively. Those coupled motions predicted by the asymmetric model were 1.6° axial rotation and 4° lateral bending, under applied lateral bending and axial rotation, respectively. In general, the predicted motion response of the cervical spine by the symmetric model was in the acceptable range and nonlinearity of the moment-rotation curve for the cervical spine was properly predicted. © IMechE 2016.

An elastic-plastic fracture mechanics analysis of weld-toe surface cracks in fillet welded T-butt joint

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fu, B.

1994-12-31

This paper describes an elastic-plastic fracture mechanics (EPFM) study of shallow weld-toe cracks. Two limiting crack configurations, plane strain edge crack and semi-circular surface crack in fillet welded T-butt plate joint, were analyzed using the finite element method. Crack depth ranging from 2 to 40% of plate thickness were considered. The elastic-plastic analysis, assuming power-law hardening relationship and Mises yield criterion, was based on incremental plasticity theory. Tension and bending loads applied were monotonically increased to a level causing relatively large scale yielding at the crack tip. Effects of weld-notch geometry and ductile material modeling on prediction of fracture mechanicsmore » characterizing parameter were assessed. It was found that the weld-notch effect reduces and the effect of material modeling increases as crack depth increases. Material modeling is less important than geometric modeling in analysis of very shallow cracks but is more important for relatively deeper cracks, e.g. crack depth more than 20% of thickness. The effect of material modeling can be assessed using a simplified structural model. Weld magnification factors derived assuming linear elastic conditions can be applied to EPFM characterization.« less

Flexural bending of southern Tibet in a retro foreland setting

PubMed Central

Wang, Erchie; Kamp, Peter J. J.; Xu, Ganqing; Hodges, Kip V.; Meng, Kai; Chen, Lin; Wang, Gang; Luo, Hui

2015-01-01

The highest elevation of the Tibetan Plateau, lying 5,700 m above sea level, occurs within the part of the Lhasa block immediately north of the India-Tibet suture zone (Yarlung Zangbo suture zone, YZSZ), being 700 m higher than the maximum elevation of more northern parts of the plateau. Various mechanisms have been proposed to explain this differentially higher topography and the rock uplift that led to it, invoking crustal compression or extension. Here we present the results of structural investigations along the length of the high elevation belt and suture zone, which rather indicate flexural bending of the southern margin of the Lhasa block (Gangdese magmatic belt) and occurrence of an adjacent foreland basin (Kailas Basin), both elements resulting from supra-crustal loading of the Lhasa block by the Zangbo Complex (Indian plate rocks) via the Great Counter Thrust. Hence we interpret the differential elevation of the southern margin of the plateau as due originally to uplift of a forebulge in a retro foreland setting modified by subsequent processes. Identification of this flexural deformation has implications for early evolution of the India-Tibet continental collision zone, implying an initial (Late Oligocene) symmetrical architecture that subsequently transitioned into the present asymmetrical wedge architecture. PMID:26174578

Monitoring the bending and twist of morphing structures

NASA Astrophysics Data System (ADS)

Smoker, J.; Baz, A.

2008-03-01

This paper presents the development of the theoretical basis for the design of sensor networks for determining the 2-dimensioal shape of morphing structures by monitoring simultaneously the bending and twist deflections. The proposed development is based on the non-linear theory of finite elements to extract the transverse linear and angular deflections of a plate-like structure. The sensors outputs are wirelessly transmitted to the command unit to simultaneously compute maps of the linear and angular deflections and maps of the strain distribution of the entire structure. The deflection and shape information are required to ascertain that the structure is properly deployed and that its surfaces are operating wrinkle-free. The strain map ensures that the structure is not loaded excessively to adversely affect its service life. The developed theoretical model is validated experimentally using a prototype of a variable cambered span morphing structure provided with a network of distributed sensors. The structure/sensor network system is tested under various static conditions to determine the response characteristics of the proposed sensor network as compared to other conventional sensor systems. The presented theoretical and experimental techniques can have a great impact on the safe deployment and effective operation of a wide variety of morphing and inflatable structures such as morphing aircraft, solar sails, inflatable wings, and large antennas.

Direct formulation of a 4-node hybrid shell element with rotational degrees of freedom

NASA Technical Reports Server (NTRS)

Aminpour, Mohammad A.

1990-01-01

A simple 4-node assumed-stress hybrid quadrilateral shell element with rotational or drilling degrees of freedom is formulated. The element formulation is based directly on a 4-node element. This direct formulation requires fewer computations than a similar element that is derived from an internal 8-node isoparametric element in which the midside degrees of freedom are eliminated in favor of rotational degree of freedom at the corner nodes. The formulation is based on the principle of minimum complementary energy. The membrane part of the element has 12 degrees of freedom including rotational degrees of freedom. The bending part of the element also has 12 degrees of freedom. The bending part of the quadratic variations for both in-plane and out-of-plane displacement fields and linear variations for both in-plane and out-of-plane rotation fields are assumed along the edges of the element. The element Cartesian-coordinate system is chosen such as to make the stress field invariant with respect to node numbering. The membrane part of the stress field is based on a 9-parameter equilibrating stress field, while the bending part is based on a 13-parameter equilibrating stress field. The element passes the patch test, is nearly insensitive to mesh distortion, does not lock, possesses the desirable invariance properties, has no spurious modes, and produces accurate and reliable results.

The biomechanical stability of a novel spacer with integrated plate in contiguous two-level and three-level ACDF models: an in vitro cadaveric study.

PubMed

Clavenna, Andrew L; Beutler, William J; Gudipally, Manasa; Moldavsky, Mark; Khalil, Saif

2012-02-01

Anterior cervical plating increases stability and hence improves fusion rates to treat cervical spine pathologies, which are often symptomatic at multiple levels. However, plating is not without complications, such as dysphagia, injury to neural elements, and plate breakage. The biomechanics of a spacer with integrated plate system combined with posterior instrumentation (PI), in two-level and three-level surgical models, has not yet been investigated. The purpose of the study was to biomechanically evaluate the multidirectional rigidity of spacer with integrated plate (SIP) at multiple levels as comparable to traditional spacers and plating. An in vitro cervical cadaveric model. Eight fresh human cervical (C2-C7) cadaver spines were tested under pure moments of ±1.5 Nm on spine simulator test frame. Each spine was tested in intact condition, with only anterior fixation and with both anterior and PI. Range of motion (ROM) was measured using Optotrak Certus (NDI, Inc., Waterloo, Ontario, Canada) motion analysis system in flexion-extension (FE), lateral bending (LB), and axial rotation (AR) at the instrumented levels (C3-C6). Repeated-measures analysis of variance was used for statistical analysis. All the surgical constructs showed significant reduction in motion compared with intact condition. In two-level fusion, SIP (C4-C6) construct significantly reduced ROM by 66.5%, 65.4%, and 60.3% when compared with intact in FE, LB, and AR, respectively. In three-level fusion, SIP (C3-C6) construct significantly reduced ROM by 65.8%, 66%, and 49.6% when compared with intact in FE, LB, and AR, respectively. Posterior instrumentation showed significant stability only in three-level fusion when compared with their respective anterior constructs. In both two-level and three-level fusion, SIP showed comparable stability to traditional spacer and plate constructs in all loading modes. The anatomically profiled spacer with integrated plate allows treatment of cervical disorders with fewer steps and less impact to cervical structures. In this biomechanical study, spacer with integrated plate construct showed comparable stability to traditional spacer and plate for two-level and three-level fusion. Posterior instrumentation showed significant effect only in three-level fusion. Clinical data are required for further validation of using spacer with integrated plate at multiple levels. Copyright © 2012 Elsevier Inc. All rights reserved.

Towards modelling of water inflow into the mantle

NASA Astrophysics Data System (ADS)

Thielmann, M.; Eichheimer, P.; Golabek, G.

2017-12-01

The transport and storage of water in the mantle significantly affects various material properties of mantle rocks and thus water plays a key role in a variety of geodynamical processes (tectonics, magmatism etc.) Geological and seismological observations suggest different inflow mechanisms of water via the subducting slab like slab bending, thermal cracking and serpentinization (Faccenda et al., 2009; Korenaga, 2017). Most of the previous numerical models do not take different dip angles of the subduction slab and subduction velocities into account, while nature provides two different types of subduction regimes i.e. shallow and deep subduction (Li et al., 2011). To which extent both parameters influence the inflow and outflow of water in the mantle still remains unclear. For the investigation of the inflow and outflow of fluids e.g. water in the mantle, we use high resolution 2D finite element simulations, which allow us to resolve subducted sediments and crustal layers. For this purpose the finite element code MVEP2 (Kaus, 2010), is tested against benchmark results (van Keken et al., 2008). In a first step we reproduced the analytical cornerflow model (Batchelor, 1967) used in the benchmark of van Keken et al.(2008) as well as the steady state temperature field. Further steps consist of successively increasing model complexity, such as the incorporation of hydrogen diffusion, water transport and dehydration reactions. ReferencesBatchelor, G. K. An Introduction to Fluid Dynamics. Cambridge University Press, Cambridge, UK (1967) van Keken, P. E., et al. A community benchmark for subduction zone modeling. Phys. Earth Planet. Int. 171, 187-197 (2008). Faccenda, M., T.V. Gerya, and L. Burlini. Deep slab hydration induced by bending-related variations in tectonic pressure. Nat. Geosci. 2, 790-793 (2009). Korenaga, J. On the extent of mantle hydration caused by plate bending. Earth Planet. Sci. Lett. 457, 1-9 (2017). Li, Z. H., Xu, Z. Q., and T.V. Gerya. Flat versus steep subduction: Contrasting modes for the formation and exhumation of high- to ultrahigh-pressure rocks in continental collision zones. Earth Planet. Sci. Lett. 301, 65-77 (2011). Kaus, B. J. P. Factors that control the angle of shear bands in geodynamic numerical models of brittle deformation. Tectonophys. 484, 36-47 (2010). The transport and storage of water in the mantle significantly affects various material properties of mantle rocks and thus water plays a key role in a variety of geodynamical processes (tectonics, magmatism etc.) Geological and seismological observations suggest different inflow mechanisms of water via the subducting slab like slab bending, thermal cracking and serpentinization (Faccenda et al., 2009; Korenaga, 2017). Most of the previous numerical models do not take different dip angles of the subduction slab and subduction velocities into account, while nature provides two different types of subduction regimes i.e. shallow and deep subduction (Li et al., 2011). To which extent both parameters influence the inflow and outflow of water in the mantle still remains unclear. For the investigation of the inflow and outflow of fluids e.g. water in the mantle, we use high resolution 2D finite element simulations, which allow us to resolve subducted sediments and crustal layers. For this purpose the finite element code MVEP2 (Kaus, 2010), is tested against benchmark results (van Keken et al., 2008). In a first step we reproduced the analytical cornerflow model (Batchelor, 1967) used in the benchmark of van Keken et al.(2008) as well as the steady state temperature field.Further steps consist of successively increasing model complexity, such as the incorporation of hydrogen diffusion, water transport and dehydration reactions. Systematic simulations are performed to assess the influence of different model parameters on various target parameters such as dehydration depth, volcanic line position etc., the ultimate goal being the derivation of scaling laws for water transport in the mantleReferencesBatchelor, G. K. An Introduction to Fluid Dynamics. Cambridge University Press, Cambridge, UK (1967)van Keken, P. E., et al. A community benchmark for subduction zone modeling. Phys. Earth Planet. Int. 171, 187-197 (2008). Faccenda, M., T.V. Gerya, and L. Burlini. Deep slab hydration induced by bending-related variations in tectonic pressure. Nat. Geosci. 2, 790-793 (2009). Korenaga, J. On the extent of mantle hydration caused by plate bending. Earth Planet. Sci. Lett. 457, 1-9 (2017). Li, Z. H., Xu, Z. Q., and T.V. Gerya. Flat versus steep subduction: Contrasting modes for the formation and exhumation of high- to ultrahigh-pressure rocks in continental collision zones. Earth Planet. Sci. Lett. 301, 65-77 (2011). Kaus, B. J. P. Factors that control the angle of shear bands in geodynamic numerical models of brittle deformation. Tectonophys. 484, 36-47 (2010).

Biomechanical Comparison of Locking Compression Plate versus Positive Profile Pins and Polymethylmethacrylate for Stabilization of the Canine Lumbar Vertebrae.

PubMed

Sturges, Beverly K; Kapatkin, Amy S; Garcia, Tanya C; Anwer, Cona; Fukuda, Shimpei; Hitchens, Peta L; Wisner, Tristan; Hayashi, Kei; Stover, Susan M

2016-04-01

To compare the stiffness, angular deformation, and mode of failure of lumbar vertebral column constructs stabilized with bilateral pins and polymethylmethacrylate (Pin-PMMA) or with a unilateral (left) locking compression plate (LCP) with monocortical screws. Ex vivo biomechanical, non-randomized. Cadaveric canine thoracolumbar specimens (n=16). Thoracolumbar (T13-L3) vertebral specimens had the L1-L2 vertebral motion unit stabilized with either Pin-PMMA or LCP. Stiffness in flexion, extension, and right and left lateral bending after nondestructive testing were compared between intact (pretreated) specimens and Pin-PMMA, and LCP constructs. The Pin-PMMA and LCP constructs were then tested to failure in flexion and left lateral bending. Both the Pin-PMMA and LCP constructs had reduced range of motion at the stabilized L1-L2 vertebral motion unit compared to intact specimens. The Pin-PMMA constructs had less range of motion for the flexion elastic zone than LCP constructs. The Pin-PMMA constructs were stiffer than intact specimens in flexion, extension, and lateral bending, and stiffer than LCP constructs in flexion and left lateral bending. The Pin-PMMA constructs had less angular deformation at construct yield and lower residual deformation at L1-L2 than LCP constructs after destructive testing to failure in flexion. The Pin-PMMA constructs were stiffer, stronger, and had less deformation at yield than LCP constructs after destructive testing to failure in lateral bending. Most constructs failed distant to the implant and fixation site. Pin-PMMA constructs had greater lumbar vertebral stiffness and reduced ROM than LCP constructs; however, both Pin-PMMA and LCP constructs were stronger than intact specimens. © Copyright 2016 by The American College of Veterinary Surgeons.

An enhanced computational method for age-at-death estimation based on the pubic symphysis using 3D laser scans and thin plate splines.

PubMed

Stoyanova, Detelina; Algee-Hewitt, Bridget F B; Slice, Dennis E

2015-11-01

The pubic symphysis is frequently used to estimate age-at-death from the adult skeleton. Assessment methods require the visual comparison of the bone morphology against age-informative characteristics that represent a series of phases. Age-at-death is then estimated from the age-range previously associated with the chosen phase. While easily executed, the "morphoscopic" process of feature-scoring and bone-to-phase-matching is known to be subjective. Studies of method and practitioner error demonstrate a need for alternative tools to quantify age-progressive change in the pubic symphysis. This article proposes a more objective, quantitative method that analyzes three-dimensional (3D) surface scans of the pubic symphysis using a thin plate spline algorithm (TPS). This algorithm models the bending of a flat plane to approximately match the surface of the bone and minimizes the bending energy required for this transformation. Known age-at-death and bending energy were used to construct a linear model to predict age from observed bending energy. This approach is tested with scans from 44 documented white male skeletons and 12 casts. The results of the surface analysis show a significant association (regression p-value = 0.0002 and coefficient of determination = 0.2270) between the minimum bending energy and age-at-death, with a root mean square error of ≈19 years. This TPS method yields estimates comparable to established methods but offers a fully integrated, objective and quantitative framework of analysis and has potential for use in archaeological and forensic casework. © 2015 Wiley Periodicals, Inc.

Paleomagnetic modeling of seamounts near the Hawaiian Emperor bend

NASA Astrophysics Data System (ADS)

Sager, William W.; Lamarche, Amy J.; Kopp, Christian

2005-08-01

The Hawaiian-Emperor Seamount chain records the motion of the Pacific Plate relative to the Hawaiian mantle hotspot for ˜80 m.y. A notable feature of the chain is the pronounced bend at its middle. This bend had been widely credited to a change in plate motion, but recent research suggests a change in hotspot motion as an alternative. Existing paleomagnetic data from the Emperor Chain suggest that the hotspot moved south during the Late Cretaceous and Early Tertiary, but reached its current latitude by the age of the bend. Thus, data from area of the bend are important for understanding changes in plume latitude. In this study, we analyze the magnetic anomalies of five seamounts (Annei, Daikakuji-W, Daikakuji- E, Abbott, and Colahan) in the region of the bend. These particular seamounts were chosen because they have been recently surveyed to collect multibeam bathymetry and magnetic data positioned with GPS navigation. Inversions of the magnetic and bathymetric data were performed to determine the mean magnetization of each seamount and from these results, paleomagnetic poles and paleolatitudes were calculated. Three of the five seamounts have reversed magnetic polarities (two are normal) and four contain a small volume of magnetic polarity opposite to the main body, consistent with formation during the Early Cenozoic, a time of geomagnetic field reversals. Although magnetization inhomogene ties can degrade the accuracy of paleomagnetic poles calculated from such models, the seamounts give results consistent with one another and with other Pacific paleomagnetic data of approximately the same age. Seamount paleolatitudes range from 13.7 to 23.7, with an average of 19.4 ± 7.4 (2σ). These values are indistinguishable from the present-day paleolatitude of the Hawaiian hotspot. Together with other paleomagnetic and geologic evidence, these data imply that the Hawaiian hotspot has moved little in latitude during the past ˜45 m.y.

Dynamics of folding: Impact of fault bend folds on earthquake cycles

NASA Astrophysics Data System (ADS)

Sathiakumar, S.; Barbot, S.; Hubbard, J.

2017-12-01

Earthquakes in subduction zones and subaerial convergent margins are some of the largest in the world. So far, forecasts of future earthquakes have primarily relied on assessing past earthquakes to look for seismic gaps and slip deficits. However, the roles of fault geometry and off-fault plasticity are typically overlooked. We use structural geology (fault-bend folding theory) to inform fault modeling in order to better understand how deformation is accommodated on the geological time scale and through the earthquake cycle. Fault bends in megathrusts, like those proposed for the Nepal Himalaya, will induce folding of the upper plate. This introduces changes in the slip rate on different fault segments, and therefore on the loading rate at the plate interface, profoundly affecting the pattern of earthquake cycles. We develop numerical simulations of slip evolution under rate-and-state friction and show that this effect introduces segmentation of the earthquake cycle. In crustal dynamics, it is challenging to describe the dynamics of fault-bend folds, because the deformation is accommodated by small amounts of slip parallel to bedding planes ("flexural slip"), localized on axial surface, i.e. folding axes pinned to fault bends. We use dislocation theory to describe the dynamics of folding along these axial surfaces, using analytic solutions that provide displacement and stress kernels to simulate the temporal evolution of folding and assess the effects of folding on earthquake cycles. Studies of the 2015 Gorkha earthquake, Nepal, have shown that fault geometry can affect earthquake segmentation. Here, we show that in addition to the fault geometry, the actual geology of the rocks in the hanging wall of the fault also affect critical parameters, including the loading rate on parts of the fault, based on fault-bend folding theory. Because loading velocity controls the recurrence time of earthquakes, these two effects together are likely to have a strong impact on the earthquake cycle.

Turbomachine combustor nozzle including a monolithic nozzle component and method of forming the same

DOE Office of Scientific and Technical Information (OSTI.GOV)

Stoia, Lucas John; Melton, Patrick Benedict; Johnson, Thomas Edward

A turbomachine combustor nozzle includes a monolithic nozzle component having a plate element and a plurality of nozzle elements. Each of the plurality of nozzle elements includes a first end extending from the plate element to a second end. The plate element and plurality of nozzle elements are formed as a unitary component. A plate member is joined with the nozzle component. The plate member includes an outer edge that defines first and second surfaces and a plurality of openings extending between the first and second surfaces. The plurality of openings are configured and disposed to register with and receivemore » the second end of corresponding ones of the plurality of nozzle elements.« less

Strength measurement of optical fibers by bending

NASA Astrophysics Data System (ADS)

Srubshchik, Leonid S.

1999-01-01

A two-point bending technique has been used not only to measure the breaking stress of optical fiber but also to predict its static and dynamic fatigue. The present theory of this test is based on elastica theory of rod. However, within the limits of elastica theory the tensile and shear stresses cannot be determined. In this paper we study dynamic and static problems for optical fiber in the two- point bending test on the base of geometrically exact theory in which rod can suffer flexure, extension, and shear. We obtain the governing partial differential equations taking into account the fact that the lateral motion of the fiber is restrained by the presence of flat parallel plates. We develop the computational methods for solving the initial and equilibrium free-boundary nonlinear planar problems. We derive the formulas for predicting of the tensile strength from strength in the bending and calculate one example.

Nonlinear analysis of 0-3 polarized PLZT microplate based on the new modified couple stress theory

NASA Astrophysics Data System (ADS)

Wang, Liming; Zheng, Shijie

2018-02-01

In this study, based on the new modified couple stress theory, the size- dependent model for nonlinear bending analysis of a pure 0-3 polarized PLZT plate is developed for the first time. The equilibrium equations are derived from a variational formulation based on the potential energy principle and the new modified couple stress theory. The Galerkin method is adopted to derive the nonlinear algebraic equations from governing differential equations. And then the nonlinear algebraic equations are solved by using Newton-Raphson method. After simplification, the new model includes only a material length scale parameter. In addition, numerical examples are carried out to study the effect of material length scale parameter on the nonlinear bending of a simply supported pure 0-3 polarized PLZT plate subjected to light illumination and uniform distributed load. The results indicate the new model is able to capture the size effect and geometric nonlinearity.

Bending-related faulting and mantle serpentinization at the Middle America trench.

PubMed

Ranero, C R; Morgan, J Phipps; McIntosh, K; Reichert, C

2003-09-25

The dehydration of subducting oceanic crust and upper mantle has been inferred both to promote the partial melting leading to arc magmatism and to induce intraslab intermediate-depth earthquakes, at depths of 50-300 km. Yet there is still no consensus about how slab hydration occurs or where and how much chemically bound water is stored within the crust and mantle of the incoming plate. Here we document that bending-related faulting of the incoming plate at the Middle America trench creates a pervasive tectonic fabric that cuts across the crust, penetrating deep into the mantle. Faulting is active across the entire ocean trench slope, promoting hydration of the cold crust and upper mantle surrounding these deep active faults. The along-strike length and depth of penetration of these faults are also similar to the dimensions of the rupture area of intermediate-depth earthquakes.

Elastic stability of laminated, flat and curved, long rectangular plates subjected to combined inplane loads

NASA Technical Reports Server (NTRS)

Viswanathan, A. V.; Tamekuni, M.; Baker, L. L.

1974-01-01

A method is presented to predict theoretical buckling loads of long, rectangular flat and curved laminated plates with arbitrary orientation of orthotropic axes each lamina. The plate is subjected to combined inplane normal and shear loads. Arbitrary boundary conditions may be stipulated along the longitudinal sides of the plate. In the absence of inplane shear loads and extensional-shear coupling, the analysis is also applicable to finite length plates. Numerical results are presented for curved laminated composite plates with boundary conditions and subjected to various loadings. These results indicate some of the complexities involved in the numerical solution of the analysis for general laminates. The results also show that the reduced bending stiffness approximation when applied to buckling problems could lead to considerable error in some cases and therefore must be used with caution.

Impact damage of composite plates

NASA Technical Reports Server (NTRS)

Lal, K. M.; Goglia, G. L.

1983-01-01

A simple model to study low velocity transverse impact of thin plates made of fiber-reinforced composite material, in particular T300/5208 graphite-epoxy was discussed. This model predicts the coefficient of restitution, which is a measure of the energy absorbed by the target during an impact event. The model is constructed on the assumption that the plate is inextensible in the fiber direction and that the material is incompressible in the z-direction. Such a plate essentially deforms by shear, hence this model neglects bending deformations of the plate. The coefficient of restitution is predicted to increase with large interlaminar shear strength and low transverse shear modulus of the laminate. Predictions are compared with the test results of impacted circular and rectangular clamped plates. Experimentally measured values of the coefficient of restitution are found to agree with the predicted values within a reasonable error.

Full-vectorial finite element method in a cylindrical coordinate system for loss analysis of photonic wire bends

NASA Astrophysics Data System (ADS)

Kakihara, Kuniaki; Kono, Naoya; Saitoh, Kunimasa; Koshiba, Masanori

2006-11-01

This paper presents a new full-vectorial finite-element method in a local cylindrical coordinate system, to effectively analyze bending losses in photonic wires. The discretization is performed in the cross section of a three-dimensional curved waveguide, using hybrid edge/nodal elements. The solution region is truncated by anisotropic, perfectly matched layers in the cylindrical coordinate system, to deal properly with leaky modes of the waveguide. This approach is used to evaluate bending losses in silicon wire waveguides. The numerical results of the present approach are compared with results calculated with an equivalent straight waveguide approach and with reported experimental data. These comparisons together demonstrate the validity of the present approach based on the cylindrical coordinate system and also clarifies the limited validity of the equivalent straight waveguide approximation.

On the relevance of modeling viscoelastic bending behavior in finite element forming simulation of continuously fiber reinforced thermoplastics

NASA Astrophysics Data System (ADS)

Dörr, Dominik; Schirmaier, Fabian J.; Henning, Frank; Kärger, Luise

2017-10-01

Finite Element (FE) forming simulation offers the possibility of a detailed analysis of the deformation behavior of multilayered thermoplastic blanks during forming, considering material behavior and process conditions. Rate-dependent bending behavior is a material characteristic, which is so far not considered in FE forming simulation of pre-impregnated, continuously fiber reinforced polymers (CFRPs). Therefore, an approach for modeling viscoelastic bending behavior in FE composite forming simulation is presented in this work. The presented approach accounts for the distinct rate-dependent bending behavior of e.g. thermoplastic CFRPs at process conditions. The approach is based on a Voigt-Kelvin (VK) and a generalized Maxwell (GM) approach, implemented within a FE forming simulation framework implemented in several user-subroutines of the commercially available FE solver Abaqus. The VK, GM, as well as purely elastic bending modeling approaches are parameterized according to dynamic bending characterization results for a PA6-CF UD-tape. It is found that only the GM approach is capable to represent the bending deformation characteristic for all of the considered bending deformation rates. The parameterized bending modeling approaches are applied to a hemisphere test and to a generic geometry. A comparison of the forming simulation results of the generic geometry to experimental tests show a good agreement between simulation and experiments. Furthermore, the simulation results reveal that especially a correct modeling of the initial bending stiffness is relevant for the prediction of wrinkling behavior, as a similar onset of wrinkles is observed for the GM, the VK and an elastic approach, fitted to the stiffness observed in the dynamic rheometer test for low curvatures. Hence, characterization and modeling of rate-dependent bending behavior is crucial for FE forming simulation of thermoplastic CFRPs.

Drilling the near cortex with elongated figure-of-8 holes to reduce the stiffness of a locking compression plate construct.

PubMed

Chen, Jerry Yongqiang; Zhou, Zhihong; Ang, Benjamin Fu Hong; Yew, Andy Khye Soon; Chou, Siaw Meng; Chia, Shi-Lu; Koh, Joyce Suang Bee; Howe, Tet Sen

2015-12-01

To compare the stiffness of locking compression plate (LCP) constructs with or without drilling the near cortex with elongated figure-of-8 holes. 24 synthetic bones were sawn to create a 10-mm gap and were fixed with a 9-hole 4.5-mm narrow LCP. In 12 bones, the near cortex of the adjacent holes to the LCP holes was drilled to create elongated figure-of-8 holes before screw insertion. The stiffness of LCP constructs under axial loading or 4-point bending was assessed by (1) dynamic quasi-physiological testing for fatigue strength, (2) quasi-static testing for stiffness, and (3) testing for absolute strength to failure. None of the 24 constructs had subcatastrophic or catastrophic failure after 10 000 cycles of fatigue loading (p=1.000). The axial stiffness reduced by 16% from 613±62 to 517±44 N/mm (p=0.012) in the case group, whereas the bending stiffness was 16±1 Nm2 in both groups (p=1.000). The maximum axial load to catastrophic failure was 1596±84 N for the control group and 1627±48 N for the case group (p=0.486), whereas the maximum bending moment to catastrophic failure was 79±12 and 80±10 Nm, respectively (p=0.919). Drilling the near cortex with elongated figure-of-8 holes reduces the axial stiffness of the LCP construct, without compromising its bending stiffness or strength.

Effect of bend faulting on the hydration state of oceanic crust: Electromagnetic constraints from the Middle America Trench

NASA Astrophysics Data System (ADS)

Naif, S.; Key, K.; Constable, S.; Evans, R. L.

2017-12-01

In Northern Central America, the portion of the incoming Cocos oceanic plate formed at the East Pacific Rise has a seafloor spreading fabric that is oriented nearly parallel to the trench axis, whereby flexural bending at the outer rise reactivates a dense network of dormant abyssal hill faults. If bending-induced normal faults behave as fluid pathways they may promote extensive mantle hydration and significantly raise the flux of fluids into the subduction system. Multi-channel seismic reflection data imaged bend faults that extend several kilometers beneath the Moho offshore Nicaragua, coincident with seismic refraction data showing significant P-wave velocity reductions in both the crust and uppermost mantle. Ignoring the effect of fracture porosity, the observed mantle velocity reduction is equivalent to an upper bound of 15-20% serpentinization (or 2.0-2.5 wt% H2O). Yet the impact of bend faulting on porosity structure and crustal hydration are not well known. Here, we present results on the electrical resistivity structure of the incoming Cocos plate offshore Nicaragua, the first controlled-source electromagnetic (CSEM) experiment at a subduction zone. The CSEM data imaged several sub-vertical conductive channels extending beneath fault scarps to 5.5 km below seafloor, providing independent evidence for fluid infiltration into the oceanic crust via bending faults. We applied Archie's Law to estimate porosity from the resistivity observations: the dike and gabbro layers increase from 2.7% and 0.7% porosity at 100 km to 4.8% and 1.7% within 20 km of the trench, respectively. In contrast the resistivity, and hence porosity, remain relatively unchanged at sub-Moho depths. Therefore, either the faults do not provide an additional flux of free water to the mantle or, in light of the reduced seismic velocities, the volumetric expansion resulting from mantle serpentinization rapidly consumes any fault-generated porosity. Since our crustal porosity estimates seaward of the outer rise are in very good agreement with drilling observations, we conclude that bending faults effectively double the subducted free water budget of the intrusive oceanic crust.

Vibration and damping of laminated, composite-material plates including thickness-shear effects

NASA Technical Reports Server (NTRS)

Bert, C. W.; Siu, C. C.

1972-01-01

An analytical investigation of sinusoidally forced vibration of laminated, anisotropic plates including bending-stretching coupling, thickness-shear flexibility, all three types of inertia effects, and material damping is presented. In the analysis the effects of thickness-shear deformation are considered by the use of a shear correction factor K, analogous to that used by Mindlin for homogeneous plates. Two entirely different approaches for calculating the thickness-shear factor for a laminate are presented. Numerical examples indicate that the value of K depends on the layer properties and the stacking sequence of the laminate.

Dynamic topography in subduction zones: insights from laboratory models

NASA Astrophysics Data System (ADS)

Bajolet, Flora; Faccenna, Claudio; Funiciello, Francesca

2014-05-01

The topography in subduction zones can exhibit very complex patterns due to the variety of forces operating this setting. If we can deduce the theoretical isostatic value from density structure of the lithosphere, the effect of flexural bending and the dynamic component of topography are difficult to quantify. In this work, we attempt to measure and analyze the topography of the overriding plate during subduction compared to a pure shortening setting. We use analog models where the lithospheres are modeled by thin-sheet layers of silicone putty lying on low-viscosity syrup (asthenosphere). The model is shorten by a piston pushing an oceanic plate while a continental plate including a weak zone to localize the deformation is fixed. In one type of experiments, the oceanic plate bends and subducts underneath the continental one; in a second type the two plates are in contact without any trench, and thus simply shorten. The topography evolution is monitored with a laser-scanner. In the shortening model, the elevation increases progressively, especially in the weak zone, and is consistent with expected isostatic values. In the subduction model, the topography is characterized, from the piston to the back-wall, by a low elevation of the dense oceanic plate, a flexural bulge, the trench forming a deep depression, the highly elevated weak zone, and the continental upper plate of intermediate elevation. The topography of the upper plate is consistent with isostatic values for very early stages, but exhibits lower elevations than expected for later stages. For a same amount of shortening of the continental plate, the thickening is the same and the plate should have the same elevation in both types of models. However, comparing the topography at 20, 29 and 39% of shortening, we found that the weak zone is 0.4 to 0.6 mm lower when there is an active subduction. Theses values correspond to 2.6 to 4 km in nature. Although theses values are high, there are of the same order as dynamic topography and could represent the dynamic effect of the slab sinking into the asthenosphere and lowering the elevation of the upper plate.

Propellant Feed System for Swirl-Coaxial Injection

NASA Technical Reports Server (NTRS)

Reynolds, David Christopher (Inventor)

2015-01-01

A propellant feed system for swirl-coaxial injection of a liquid propellant includes a reservoir having a bottom plate and at least one tube originating in the bottom plate and extending therefrom. The tube has rectangular slits defined in and distributed tangentially and evenly about a portion of the tube that is disposed in the bottom plate. Drain holes are provided in the bottom plate and tunnels are defined in the bottom plate. Each tunnel fluidly couples one of the drain holes to a corresponding one of the rectangular slits. Each tunnel includes (i) a bend of at least 90.degree., and (ii) a straight portion leading to its corresponding rectangular slit wherein the straight portion is at least five times as long as a hydraulic diameter of the corresponding rectangular slit.

Analysis and experiments for composite laminates with holes and subjected to 4-point bending

NASA Technical Reports Server (NTRS)

Shuart, M. J.; Prasad, C. B.

1990-01-01

Analytical and experimental results are presented for composite laminates with a hole and subjected to four-point bending. A finite-plate analysis is used to predict moment and strain distributions for six-layer quasi-isotropic laminates and transverse-ply laminates. Experimental data are compared with the analytical results. Experimental and analytical strain results show good agreement for the quasi-isotropic laminates. Failure of the two types of composite laminates is described, and failure strain results are presented as a function of normalized hole diameter. The failure results suggest that the initial failure mechanism for laminates subjected to four-point bending are similar to the initial failure mechanisms for corresponding laminates subjected to uniaxial inplane loadings.

Creep relaxation of fuel pin bending and ovalling stresses. [BEND code, OVAL code, MARC-CDC code

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chan, D.P.; Jackson, R.J.

1981-10-01

Analytical methods for calculating fuel pin cladding bending and ovalling stresses due to pin bundle-duct mechanical interaction taking into account nonlinear creep are presented. Calculated results are in agreement with finite element results by MARC-CDC program. The methods are used to investigate the effect of creep on the FTR fuel cladding bending and ovalling stresses. It is concluded that the cladding of 316 SS 20 percent CW and reference design has high creep rates in the FTR core region to keep the bending and ovalling stresses to acceptable levels. 6 refs.

Aeroservoelastic DAP missile fin development. [directionally attached piezoelectric actuator

NASA Technical Reports Server (NTRS)

Barrett, Ron

1993-01-01

The development of an active aeroservoelastic missile fin using directionally attached piezoelectric (DAP) actuator elements is detailed. Several different types of actuator elements are examined, including piezoelectric polymers, piezoelectric fiber composites, and conventionally attached piezoelectric (CAP) and DAP elements. These actuator elements are bonded to the substrate of a torque plate. The root of the torque plate is attached to a fuselage hard point or folding pivot. The tip of the plate is bonded to an aerodynamic shell which undergoes a pitch change as the plate twists. The design procedures used on the plate are discussed. A comparison of the various actuator element shows that DAP elements provide the highest deflections with the highest torsional stiffness. A torque plate was constructed from 0.2032 mm thick DAP elements bonded to a 0.127 mm thick AISI 1010 steel substrate. The torque plate produced static twist deflections in excess of +/- 3 deg. An aerodynamic shell with a modified NACA 0012 profile was added to the torque plate. This fin was tested in a wind tunnel at speeds up to 50 ms/sec. The static deflection of the fin was predicted to within 6 percent of the experimental data.

Buckling analysis for axially compressed flat plates, structural sections, and stiffened plates reinforced with laminated composites

NASA Technical Reports Server (NTRS)

Viswanathan, A. V.; Soong, T.; Miller, R. E., Jr.

1971-01-01

A classical buckling analysis is developed for stiffened, flat plates composed of a series of linked plate and beam elements. Plates are idealized as multilayered orthotropic elements. Structural beads and lips are idealized as beams. The loaded edges of the stiffened plate are simply-supported and the conditions at the unloaded edges can be prescribed arbitrarily. The plate and beam elements are matched along their common junctions for displacement continuity and force equilibrium in an exact manner. Offsets between elements are considered in the analysis. Buckling under uniaxial compressive load for plates, sections, and stiffened plates is investigated. Buckling loads are the lowest of all possible general and local failure modes, and the mode shape is used to determine whether buckling is a local or general instability. Numerical correlations with existing analysis and test data for plates, sections, and stiffened plates including boron-reinforced structures are discussed. In general correlations are reasonably good.

Deploying weigh-in-motion installations on asphalt concrete pavements.

DOT National Transportation Integrated Search

2010-02-01

The strategic plan for establishing a vehicle weight monitoring net across Texas calls for deploying two : technology types piezoelectric and bending plate systems, and seeks to install weigh-in-motion (WIM) : systems in roadways that are under n...

Spaceflight-Induced Bone Loss Alters Failure Mode and Reduces Bending Strength in Murine Spinal Segments

PubMed Central

Berg-Johansen, Britta; Liebenberg, Ellen C.; Li, Alfred; Macias, Brandon R.; Hargens, Alan R.; Lotz, Jeffrey C.

2017-01-01

Intervertebral disc herniation rates are quadrupled in astronauts following spaceflight. While bending motions are main contributors to herniation, the effects of microgravity on the bending properties of spinal discs are unknown. Consequently, the goal of this study was to quantify the bending properties of tail discs from mice with or without microgravity exposure. Caudal motion segments from six mice returned from a 30-day Bion M1 mission and eight vivarium controls were loaded to failure in four-point bending. After testing, specimens were processed using histology to determine the location of failure, and adjacent motion segments were scanned with micro-computed tomography (μCT) to quantify bone properties. We observed that spaceflight significantly shortened the nonlinear toe region of the force-displacement curve by 32% and reduced the bending strength by 17%. Flight mouse spinal segments tended to fail within the growth plate and epiphyseal bone, while controls tended to fail at the disc-vertebra junction. Spaceflight significantly reduced vertebral bone volume fraction, bone mineral density, and trabecular thickness, which may explain the tendency of flight specimens to fail within the epiphyseal bone. Together, these results indicate that vertebral bone loss during spaceflight may degrade spine bending properties and contribute to increased disc herniation risk in astronauts. PMID:26285046

A multidisciplinary approach to constrain incoming plate hydration in the Central American Margin

NASA Astrophysics Data System (ADS)

Hu, Y.; Guild, M. R.; Naif, S.; Eimer, M. O.; Evans, O.; Fornash, K.; Plank, T. A.; Shillington, D. J.; Vervelidou, F.; Warren, J. M.; Wiens, D.

2017-12-01

The oceanic crust and mantle of the incoming plate are potentially the greatest source of water to the subduction zone, but their extent of hydration is poorly constrained. Hydrothermal alteration of the oceanic crust is an important source of mineral-bound water that ultimately dehydrates during subduction. Bend faults at the trench-outer rise provide another viable mechanism to further hydrate the down-going plate. Here, we take a multidisciplinary approach to constrain the fluid budget of the subducting plate at the Northern Central American margin; this site was chosen since it has an unusually wet subducting slab at the Nicaragua segment. Abundant geophysical and geochemical datasets are available for this region and this work is an analysis of these data. Controlled-source electromagnetic (CSEM) and wide-angle seismic (WAS) observations show significant resistivity and velocity reductions in the incoming oceanic crust associated with bend faults, which suggests seawater infiltration and hydrous alteration. We used the CSEM porosity constraints to predict P-wave velocity and find that the WAS data require an additional reduction of up to 0.3 km/s in the lower crust at the trench, equivalent to 2 wt% H2O. We implemented the porosity structure together with constraints on fluid flow and reaction kinetics into two-phase flow numerical models to quantify the degree of serpentinization possible relative to WAS estimates. Thermodynamic modeling of basalt and peridotite bulk compositions were used to predict the alteration assemblages and associated water contents in the bend faulting region as well as the dehydration fluxes during subduction. In Nicaragua, the major fluid pulse at sub-arc depths results from chlorite and antigorite breakdown in the upper 10 km of the slab mantle, whereas in Costa Rica, the slab mantle is not predicted to dehydrate at sub-arc depths. In addition, comparisons between observed and predicted magnetic anomalies and geochemical variations along strike and across arc provide insights into the relative contribution of fluids from the subducted crust and mantle. Our findings suggest that, in addition to mantle serpentinization, the incoming oceanic crust also experiences a high degree of bending-induced hydration and transports a substantial flux of H2O to the mantle wedge.

The constraint method: A new finite element technique. [applied to static and dynamic loads on plates

NASA Technical Reports Server (NTRS)

Tsai, C.; Szabo, B. A.

1973-01-01

An approch to the finite element method which utilizes families of conforming finite elements based on complete polynomials is presented. Finite element approximations based on this method converge with respect to progressively reduced element sizes as well as with respect to progressively increasing orders of approximation. Numerical results of static and dynamic applications of plates are presented to demonstrate the efficiency of the method. Comparisons are made with plate elements in NASTRAN and the high-precision plate element developed by Cowper and his co-workers. Some considerations are given to implementation of the constraint method into general purpose computer programs such as NASTRAN.

A Quadruped Micro-Robot Based on Piezoelectric Driving

PubMed Central

Su, Qi; Quan, Qiquan; Deng, Jie; Yu, Hongpeng

2018-01-01

Inspired by a way of rowing, a new piezoelectric driving quadruped micro-robot operating in bending-bending hybrid vibration modes was proposed and tested in this work. The robot consisted of a steel base, four steel connecting pins and four similar driving legs, and all legs were bonded by four piezoelectric ceramic plates. The driving principle is discussed, which is based on the hybrid of first order vertical bending and first order horizontal bending vibrations. The bending-bending hybrid vibration modes motivated the driving foot to form an elliptical trajectory in space. The vibrations of four legs were used to provide the driving forces for robot motion. The proposed robot was fabricated and tested according to driving principle. The vibration characteristics and elliptical movements of the driving feet were simulated by FEM method. Experimental tests of vibration characteristics and mechanical output abilities were carried out. The tested resonance frequencies and vibration amplitudes agreed well with the FEM calculated results. The size of robot is 36 mm × 98 mm × 14 mm, its weight is only 49.8 g, but its maximum load capacity achieves 200 g. Furthermore, the robot can achieve a maximum speed of 33.45 mm/s. PMID:29518964

A Quadruped Micro-Robot Based on Piezoelectric Driving.

PubMed

Su, Qi; Quan, Qiquan; Deng, Jie; Yu, Hongpeng

2018-03-07

Inspired by a way of rowing, a new piezoelectric driving quadruped micro-robot operating in bending-bending hybrid vibration modes was proposed and tested in this work. The robot consisted of a steel base, four steel connecting pins and four similar driving legs, and all legs were bonded by four piezoelectric ceramic plates. The driving principle is discussed, which is based on the hybrid of first order vertical bending and first order horizontal bending vibrations. The bending-bending hybrid vibration modes motivated the driving foot to form an elliptical trajectory in space. The vibrations of four legs were used to provide the driving forces for robot motion. The proposed robot was fabricated and tested according to driving principle. The vibration characteristics and elliptical movements of the driving feet were simulated by FEM method. Experimental tests of vibration characteristics and mechanical output abilities were carried out. The tested resonance frequencies and vibration amplitudes agreed well with the FEM calculated results. The size of robot is 36 mm × 98 mm × 14 mm, its weight is only 49.8 g, but its maximum load capacity achieves 200 g. Furthermore, the robot can achieve a maximum speed of 33.45 mm/s.

Study on bending behaviour of nickel–titanium rotary endodontic instruments by analytical and numerical analyses

PubMed Central

Tsao, C C; Liou, J U; Wen, P H; Peng, C C; Liu, T S

2013-01-01

Aim To develop analytical models and analyse the stress distribution and flexibility of nickel–titanium (NiTi) instruments subject to bending forces. Methodology The analytical method was used to analyse the behaviours of NiTi instruments under bending forces. Two NiTi instruments (RaCe and Mani NRT) with different cross-sections and geometries were considered. Analytical results were derived using Euler–Bernoulli nonlinear differential equations that took into account the screw pitch variation of these NiTi instruments. In addition, the nonlinear deformation analysis based on the analytical model and the finite element nonlinear analysis was carried out. Numerical results are obtained by carrying out a finite element method. Results According to analytical results, the maximum curvature of the instrument occurs near the instrument tip. Results of the finite element analysis revealed that the position of maximum von Mises stress was near the instrument tip. Therefore, the proposed analytical model can be used to predict the position of maximum curvature in the instrument where fracture may occur. Finally, results of analytical and numerical models were compatible. Conclusion The proposed analytical model was validated by numerical results in analysing bending deformation of NiTi instruments. The analytical model is useful in the design and analysis of instruments. The proposed theoretical model is effective in studying the flexibility of NiTi instruments. Compared with the finite element method, the analytical model can deal conveniently and effectively with the subject of bending behaviour of rotary NiTi endodontic instruments. PMID:23173762

Biomechanical Comparison Study of Three Fixation Methods for Proximal Chevron Osteotomy of the First Metatarsal in Hallux Valgus

PubMed Central

Kim, Jin Su; Young, Ki Won; Kim, Ji Soo; Lee, Kyung Tai

2017-01-01

Background Fixation of proximal chevron metatarsal osteotomy has been accomplished using K-wires traditionally and with a locking plate recently. However, both methods have many disadvantages. Hence, we developed an intramedullary fixation technique using headless cannulated screws and conducted a biomechanical study to evaluate the superiority of the technique to K-wire and locking plate fixations. Methods Proximal chevron metatarsal osteotomy was performed on 30 synthetic metatarsal models using three fixation techniques. Specimens in group I were fixated with K-wires (1.6 mm × 2) and in group II with headless cannulated screws (3.0 mm × 2) distally through the intramedullary canal. Specimens in group III were fixated with a locking X-shaped plate (1.3-mm thick) and screws (2.5 mm × 4). Eight metatarsal specimens were selected from each group for walking fatigue test. Bending stiffness and dorsal angulation were measured by 1,000 repetitions of a cantilever bending protocol in a plantar to dorsal direction. The remaining two samples from each group were subjected to 5 mm per minute axial loading to assess the maximal loading tolerance. Results All samples in group I failed walking fatigue test while group II and group III tolerated the walking fatigue test. Group II showed greater resistance to bending force and smaller dorsal angulation than group III (p = 0.001). On the axial loading test, group I and group II demonstrated superior maximum tolerance to group III (54.8 N vs. 47.2 N vs. 28.3 N). Conclusions Authors have demonstrated proximal chevron metatarsal osteotomy with intramedullary screw fixation provides superior biomechanical stability to locking plate and K-wire fixations. The new technique using intramedullary screw fixation can offer robust fixation and may lead to better outcomes in surgical treatment of hallux valgus. PMID:29201305

The Relation Between Rotation Deformity and Nerve Root Stress in Lumbar Scoliosis

NASA Astrophysics Data System (ADS)

Kim, Ho-Joong; Lee, Hwan-Mo; Moon, Seong-Hwan; Chun, Heoung-Jae; Kang, Kyoung-Tak

Even though several finite element models of lumbar spine were introduced, there has been no model including the neural structure. Therefore, the authors made the novel lumbar spine finite element model including neural structure. Using this model, we investigated the relation between the deformity pattern and nerve root stress. Two lumbar models with different types of curve pattern (lateral bending and lateral bending with rotation curve) were made. In the model of lateral bending curves without rotation, the principal compressive nerve root stress on the concave side was greater than the principal tensile stress on the convex side at the apex vertebra. Contrarily, in the lateral bending curve with rotational deformity, the nerve stress on the convex side was higher than that on the concave side. Therefore, this study elicit that deformity pattern could have significantly influence on the nerve root stress in the lumbar spine.

The Shock and Vibration Digest. Volume 12, Number 8,

DTIC Science & Technology

1980-08-01

half tme coefficient of 0.315 in the above lamina. Sequential delamination began when a strip equation because two surfaces are formed). of width D in...a striker plate. Each specimen study of the two-dimensional ( plane -strain) response was subjected to two separate impact loadings: an of an elastic...laminated plate; they used a finite ele- in- plane impact and a so-called shear-bending impact. ment/normal mode technique. The physical behavior The

Comparison of technique errors of intraoral radiographs taken on film v photostimulable phosphor (PSP) plates.

PubMed

Zhang, Wenjian; Huynh, Carolyn P; Abramovitch, Kenneth; Leon, Inga-Lill K; Arvizu, Liliana

2012-06-01

The objective of this study was to compare the technical errors of intraoral radiographs exposed on film v photostimulable phosphor (PSP) plates. The intraoral radiographic images exposed on phantoms from preclinical practical exams of dental and dental hygiene students were used. Each exam consisted of 10 designated periapical and bitewing views. A total of 107 film sets and 122 PSP sets were evaluated for technique errors, including placement, elongation, foreshortening, overlapping, cone cut, receptor bending, density, mounting, dot in apical area, and others. Some errors were further subcategorized as minor, major, or remake depending on the severity. The percentages of radiographs with various errors were compared between film and PSP by the Fisher's Exact Test. Compared with film, there was significantly less PSP foreshortening, elongation, and bending errors, but significantly more placement and overlapping errors. Using a wrong sized receptor due to the similarity of the color of the package sleeves is a unique PSP error. Optimum image quality is attainable with PSP plates as well as film. When switching from film to a PSP digital environment, more emphasis is necessary for placing the PSP plates, especially those with excessive packet edge, and then correcting the corresponding angulation for the beam alignment. Better design for improving intraoral visibility and easy identification of different sized PSP will improve the clinician's technical performance with this receptor.

Probing elastically or plastically induced structural heterogeneities in bulk metallic glasses by nanoindentation pop-in tests

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liu, Tingkun; Gao, Yanfei; Bei, Hongbin

Shear banding dynamics in bulk metallic glasses (BMGs) is manifested by the spatiotemporal evolution of strain fields which in turn depend on structural heterogeneities. The spacing of these heterogeneities, as a characteristic length scale, was determined from the analysis of nanoindentation pop-in tests using a stochastic model. Furthermore, the pre-stress by elastic bending and residual stress by plastic bending of BMG plates were found to dramatically decrease such spacings, thus increasing heterogeneity density and mechanically rejuvenating the glass structure.

Probing elastically or plastically induced structural heterogeneities in bulk metallic glasses by nanoindentation pop-in tests

DOE PAGES

Liu, Tingkun; Gao, Yanfei; Bei, Hongbin

2017-07-21

Shear banding dynamics in bulk metallic glasses (BMGs) is manifested by the spatiotemporal evolution of strain fields which in turn depend on structural heterogeneities. The spacing of these heterogeneities, as a characteristic length scale, was determined from the analysis of nanoindentation pop-in tests using a stochastic model. Furthermore, the pre-stress by elastic bending and residual stress by plastic bending of BMG plates were found to dramatically decrease such spacings, thus increasing heterogeneity density and mechanically rejuvenating the glass structure.

Dynamic magnification factors for tree blow-down by powder snow avalanche air blasts

NASA Astrophysics Data System (ADS)

Bartelt, Perry; Bebi, Peter; Feistl, Thomas; Buser, Othmar; Caviezel, Andrin

2018-03-01

We study how short duration powder avalanche blasts can break and overturn tall trees. Tree blow-down is often used to back-calculate avalanche pressure and therefore constrain avalanche flow velocity and motion. We find that tall trees are susceptible to avalanche air blasts because the duration of the air blast is near to the period of vibration of tall trees, both in bending and root-plate overturning. Dynamic magnification factors for bending and overturning failures should therefore be considered when back-calculating avalanche impact pressures.

Effectiveness of Rotation-free Triangular and Quadrilateral Shell Elements in Sheet-metal Forming Simulations

DOE Office of Scientific and Technical Information (OSTI.GOV)

Brunet, M.; Sabourin, F.

2005-08-05

This paper is concerned with the effectiveness of triangular 3-node shell element without rotational d.o.f. and the extension to a new 4-node quadrilateral shell element called S4 with only 3 translational degrees of freedom per node and one-point integration. The curvatures are computed resorting to the surrounding elements. Extension from rotation-free triangular element to a quadrilateral element requires internal curvatures in order to avoid singular bending stiffness. Two numerical examples with regular and irregular meshes are performed to show the convergence and accuracy. Deep-drawing of a box, spring-back analysis of a U-shape strip sheet and the crash simulation of amore » beam-box complete the demonstration of the bending capabilities of the proposed rotation-free triangular and quadrilateral elements.« less

Biomechanical analysis of plate systems for proximal humerus fractures: a systematic literature review.

PubMed

Jabran, Ali; Peach, Chris; Ren, Lei

2018-04-27

Proximal humerus fractures are the third most common in the human body but their management remains controversial. Open reduction and internal fixation with plates is one of the leading modes of operative treatment for these fractures. The development of technologies and techniques for these plates, during the recent decades, promise a bright future for their clinical use. A comprehensive review of in vitro biomechanical studies is needed for the comparison of plates' mechanical performance and the testing methodologies. This will not only guide clinicians with plate selection but also with the design of future in vitro biomechanical studies. This review was aimed to systematically categorise and review the in vitro biomechanical studies of these plates based on their protocols and discuss their results. The technologies and techniques investigated in these studies were categorised and compared to reach a census where possible. Web of Science and Scopus database search yielded 62 studies. Out of these, 51 performed axial loading, torsion, bending and/or combined bending and axial loading while 11 simulated complex glenohumeral movements by using tendons. Loading conditions and set-up, failure criteria and performance parameters, as well as results for each study, were reviewed. Only two studies tested four-part fracture model while the rest investigated two- and three-part fractures. In ten studies, synthetic humeri were tested instead of cadaveric ones. In addition to load-displacement data, three-dimensional motion analysis systems, digital image correlation and acoustic emission testing have been used for measurement. Overall, PHILOS was the most tested plate and locking plates demonstrated better mechanical performance than non-locking ones. Conflicting results have been published for their comparison with non-locking blade plates and polyaxial locking screws. Augmentation with cement [calcium phosphate or poly(methyl methacrylate)] or allografts (fibular and femoral head) was found to improve bone-plate constructs' mechanical performance. Controversy still lies over the use of rigid and semi-rigid implants and the insertion of inferomedial screws for calcar region support. This review will guide the design of in vitro and in silico biomechanical tests and also supplement the study of clinical literature.

Buckling and postbuckling behavior of square compression-loaded graphite-epoxy plates with circular cutouts

NASA Technical Reports Server (NTRS)

Nemeth, Michael P.

1990-01-01

An experimental study of the postbuckling behavior of square compression-loaded graphite-epoxy plates and isotropic plates with a central circular cutout is presented. Results are presented for unidirectional (0 sub 10)s and (90 sub 10)s plates, (0/90 sub 5)s plates, and for aluminum plates. Results are also presented for (+ or - O sub 6)s angle-ply plates for values of O = 30, 46, and 60 degrees. The experimental results indicate that the change in axial stiffness of a plate at buckling is strongly dependent upon cutout size and plate orthotropy. The presence of a cutout gives rise to an internal load distribution that changes, sometimes dramtically, as a function of cutout size coupled with the plate orthotropy. In the buckled state, the role of orthotropy becomes more significant since bending in addition to membrane orthotropy is present. Most of the plates with cutouts exhibited less postbuckling stiffness than the corresponding plate without a cutout, and the postbuckling stiffness decreased with increasing cutout size. However, some of the highly orthotropic plates with cutouts exhibited more postbuckling stiffness than the corresponding plate without a cutout.

Thermal vibration of rectangular single-layered black phosphorus predicted by orthotropic plate model

NASA Astrophysics Data System (ADS)

Zhang, Yiqing; Wang, Lifeng; Jiang, Jingnong

2018-03-01

Vibrational behavior is very important for nanostructure-based resonators. In this work, an orthotropic plate model together with a molecular dynamics (MD) simulation is used to investigate the thermal vibration of rectangular single-layered black phosphorus (SLBP). Two bending stiffness, two Poisson's ratios, and one shear modulus of SLBP are calculated using the MD simulation. The natural frequency of the SLBP predicted by the orthotropic plate model agrees with the one obtained from the MD simulation very well. The root of mean squared (RMS) amplitude of the SLBP is obtained by MD simulation and the orthotropic plate model considering the law of energy equipartition. The RMS amplitude of the thermal vibration of the SLBP is predicted well by the orthotropic plate model compared to the MD results. Furthermore, the thermal vibration of the SLBP with an initial stress is also well-described by the orthotropic plate model.

Stress analyses of flat plates with attached nozzles. Vol. 3. Experimental stress analyses of a flat plate with two closely spaced nozzles of equal diameter attached

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bryson, J.W.; Swinson, W.F.

1975-12-01

The complete test results for a flat plate with two closely spaced nozzles attached are presented. Test loadings were 1:1, 1:2, and 2:1 biaxial planar tension loadings on the plate, axial thrust loadings applied separately to the nozzles, and bending moment loadings applied to the nozzles both within and normal to the plane of symmetry containing the nozzle axes. The test plate was 36 x 36 x 0.375 in., and the attached nozzles had outer diameters of 2.625 in. and wall thicknesses of 0.250 in. The nozzles were located in the center of the plate with their centers 3.0 in.more » apart and were considered to be free of weld distortions and irregularities in the junction region. 6 references. (auth)« less

Application of the variational-asymptotical method to composite plates

NASA Technical Reports Server (NTRS)

Hodges, Dewey H.; Lee, Bok W.; Atilgan, Ali R.

1992-01-01

A method is developed for the 3D analysis of laminated plate deformation which is an extension of a variational-asymptotical method by Atilgan and Hodges (1991). Both methods are based on the treatment of plate deformation by splitting the 3D analysis into linear through-the-thickness analysis and 2D plate analysis. Whereas the first technique tackles transverse shear deformation in the second asymptotical approximation, the present method simplifies its treatment and restricts it to the first approximation. Both analytical techniques are applied to the linear cylindrical bending problem, and the strain and stress distributions are derived and compared with those of the exact solution. The present theory provides more accurate results than those of the classical laminated-plate theory for the transverse displacement of 2-, 3-, and 4-layer cross-ply laminated plates. The method can give reliable estimates of the in-plane strain and displacement distributions.

Buckling analysis for structural sections and stiffened plates reinforced with laminated composites.

NASA Technical Reports Server (NTRS)

Viswanathan, A. V.; Soong, T.-C.; Miller, R. E., Jr.

1972-01-01

A classical buckling analysis is developed for stiffened, flat plates composed of a series of linked flat plate and beam elements. Plates are idealized as multilayered orthotropic elements; structural beads and lips are idealized as beams. The loaded edges of the stiffened plate are simply supported and the conditions at the unloaded edges can be prescribed arbitrarily. The plate and beam elements are matched along their common junctions for displacement continuity and force equilibrium in an exact manner. Offsets between elements are considered in the analysis. Buckling under uniaxial compressive load for plates, sections and stiffened plates is investigated. Buckling loads are found as the lowest of all possible general and local failure modes and the mode shape is used to determine whether buckling is a local or general instability. Numerical correlations with existing analysis and test data for plates, sections and stiffened plates including boron-reinforced structures are discussed. In general, correlations are reasonably good.

Deducing material quality in cast and hot-forged steels by new bending test

NASA Astrophysics Data System (ADS)

Valberg, Henry; Langøy, Morten; Nedreberg, Mette; Helvig, Torgeir

2017-10-01

A special bend test has been developed and applied for the purpose of characterization and comparison of the material ductility in crankpin steel discs manufactured by casting, or casting subsequently followed by hot open-die forging (ODF) or closed-die forging (CDF). The bending test specimen consists of a small rectangular plate of material with a round hole cut out in the middle. The "eye-shape" specimens were cut out from various positions either near to the surface of, or from the interior of the discs. The test method revealed differences in ductility for the investigated materials, and for different depth positions inside the discs. The roughening of the specimen surface on the top-side of the specimen bend also varied dependent on the processing method for the material. Current results show that this test method is useful for evaluation of material quality in differently processed material. Experimental bend test results are presented for differently processed variants of the same material, i.e., crankpin discs either made by solely casting or casting subsequently followed by hot working either by ODF or CDF.

Bending analysis of a general cross-ply laminate using 3D elasticity solution and layerwise theory

NASA Astrophysics Data System (ADS)

Yazdani Sarvestani, H.; Naghashpour, A.; Heidari-Rarani, M.

2015-12-01

In this study, the analytical solution of interlaminar stresses near the free edges of a general (symmetric and unsymmetric layups) cross-ply composite laminate subjected to pure bending loading is presented based on Reddy's layerwise theory (LWT) for the first time. First, the reduced form of displacement field is obtained for a general cross-ply composite laminate subjected to a bending moment by elasticity theory. Then, first-order shear deformation theory of plates and LWT is utilized to determine the global and local deformation parameters appearing in the displacement fields, respectively. One of the main advantages of the developed solution based on the LWT is exact prediction of interlaminar stresses at the boundary layer regions. To show the accuracy of this solution, three-dimensional elasticity bending problem of a laminated composite is solved for special set of boundary conditions as well. Finally, LWT results are presented for edge-effect problems of several symmetric and unsymmetric cross-ply laminates under the bending moment. The obtained results indicate high stress gradients of interlaminar stresses near the edges of laminates.

77 FR 16868 - Quality Verification for Plate-Type Uranium-Aluminum Fuel Elements for Use in Research and Test...

Federal Register 2010, 2011, 2012, 2013, 2014

2012-03-22

... Fuel Elements for Use in Research and Test Reactors AGENCY: Nuclear Regulatory Commission. ACTION... Plate-Type Uranium-Aluminum Fuel Elements for Use in Research and Test Reactors.'' This guide describes... plate-type uranium-aluminum fuel elements used in research and test reactors (RTRs). DATES: Submit...

Effect of Bottoming on Material Property during Sheet Forming Process through Finite Element Method

NASA Astrophysics Data System (ADS)

Akinlabi, Stephen A.; Fatoba, Olawale S.; Mashinini, Peter M.; Akinlabi, Esther T.

2018-03-01

Metal forming is one of the conventional manufacturing processes of immense relevance till date even though modern manufacturing processes have evolved over the years. It is a known fact that material tends to return or spring back to its original form during forming or bending. The phenomena have been well managed through its application in various manufacturing processes by compensating for the spring back through overbending and bottoming. Overbending is bending the material beyond the desired shape to allow the material to spring back to the expected shape. Bottoming, on the other hand, is a process of undergoing plastic deformation at the point of bending. This study reports on the finite element analysis of the effect of bottoming on the material property during the sheet forming process with the aim of optimising the process. The result of the analysis revealed that the generated plastic strains are in the order between 1.750e00-1 at the peak of the bending and 3.604e00-2, which was at the early stage of the bending.

Hydrodynamics of a three-dimensional self-propelled flexible plate

NASA Astrophysics Data System (ADS)

Ryu, Jaeha; Sung, Hyung Jin

2017-11-01

A three-dimensional self-propelled flexible plate in a quiescent flow was simulated using the immersed boundary method. The clamped leading edge of the flexible plate was forced into a vertical oscillation, while free to move horizontally. To reveal the hydrodynamics of the plate, the averaged cruising speed (UC) , the input power (P) , and the swimming efficiency (η) were analyzed as a function of the bending rigidity (γ) and the flapping frequency (f) . The velocity field around the plate and the exerted force on the plate were demonstrated to find out the dynamic interaction between the plate and the surrounding fluid. The kinematics of the plate, the maximum angle of attack (ϕmax) , and the mean effective length (Leff) were examined accounting for the hydrodynamics of the self-propelled flexible plate. The vortical structures around the plate were visualized, and the influence of the tip vortex on the swimming efficiency was explored qualitatively and quantitatively. This work was supported by the Creative Research Initiatives (No. 2017-013369) program of the National Research Foundation of Korea (MSIP).

Application of ply level analysis to flexural wave propagation

NASA Astrophysics Data System (ADS)

Valisetty, R. R.; Rehfield, L. W.

1988-10-01

A brief survey is presented of the shear deformation theories of laminated plates. It indicates that there are certain non-classical influences that affect bending-related behavior in the same way as do the transverse shear stresses. They include bending- and stretching-related section warping and the concomitant non-classical surface parallel stress contributions and the transverse normal stress. A bending theory gives significantly improved performance if these non-classical affects are incorporated. The heterogeneous shear deformations that are characteristic of laminates with highly dissimilar materials, however, require that attention be paid to the modeling of local rotations. In this paper, it is shown that a ply level analysis can be used to model such disparate shear deformations. Here, equilibrium of each layer is analyzed separately. Earlier applications of this analysis include free-edge laminate stresses. It is now extended to the study of flexural wave propagation in laminates. A recently developed homogeneous plate theory is used as a ply level model. Due consideration is given to the non-classical influences and no shear correction factors are introduced extraneously in this theory. The results for the lowest flexural mode of travelling planar harmonic waves indicate that this approach is competitive and yields better results for certain laminates.

SPIRE spinous process stabilization plate: biomechanical evaluation of a novel technology. Invited submission from the Joint Section Meeting on Disorders of the Spine and Peripheral Nerves, March 2005.

PubMed

Wang, Jeremy C; Spenciner, David; Robinson, James C

2006-02-01

The authors studied the biomechanical properties of a novel spinous process stabilization plate (CD HORIZON SPIRE Spinal System) and present the results in comparison with those of other posterior fixation methods. Ten functional cadaveric lumbar segments were subjected to nondestructive quasistatic loading forces in 10 different conditions: intact, destabilized (discectomy), fitted with spinous process plate (SPP) alone, with anterior-column support (ACS) alone, ACS with SPP, ACS with posterior translaminar facet screw (PTFS) fixation, ACS with unilateral pedicle screw and rod (UPSR) fixation, ACS with bilateral pedicle screw and rod (BPSR) fixation, UPSR alone, or BPSR alone. Stiffness and range of motion (ROM) data were compared using a repeated-measures, one-way analysis of variance. The construct with greatest mean limitation of flexion-extension ROM was ACS/SPP at 4.14 degrees whereas it was 5.75 degrees for ACS/UPSR fixation, 5.03 degrees for ACS/BPSR fixation, and 10.13 degrees for the intact spine. The SPIRE plate alone also provided greater flexion and extension stiffness, with less ROM than other posterior stabilization options. Fixation with BPSR with or without ACS resulted in the stiffest construct in lateral bending and axial rotation. The SPP and UPSR fixation groups were equivalent in resisting lateral bending and axial rotation forces with or without ACS. The SPIRE plate effectively stabilized the spine, and the test results compare favorably with other fixation techniques that are more time consuming to perform and have greater inherent risks.

Cellular basis of neuroepithelial bending during mouse spinal neural tube closure

PubMed Central

McShane, Suzanne G.; Molè, Matteo A.; Savery, Dawn; Greene, Nicholas D. E; Tam, Patrick P.L.; Copp, Andrew J.

2015-01-01

Summary Bending of the neural plate at paired dorsolateral hinge points (DLHPs) is required for neural tube closure in the spinal region of the mouse embryo. As a step towards understanding the morphogenetic mechanism of DLHP development, we examined variations in neural plate cellular architecture and proliferation during closure. Neuroepithelial cells within the median hinge point (MHP) contain nuclei that are mainly basally located and undergo relatively slow proliferation, with a 7 h cell cycle length. In contrast, cells in the dorsolateral neuroepithelium, including the DLHP, exhibit nuclei distributed throughout the apico-basal axis and undergo rapid proliferation, with a 4 h cell cycle length. As the neural folds elevate, cell numbers increase to a greater extent in the dorsolateral neural plate that contacts the surface ectoderm, compared with the more ventromedial neural plate where cells contact paraxial mesoderm and notochord. This marked increase in dorsolateral cell number cannot be accounted for solely on the basis of enhanced cell proliferation in this region. We hypothesised that neuroepithelial cells may translocate in a ventral-to-dorsal direction as DLHP formation occurs, and this was confirmed by vital cell labelling in cultured embryos. The translocation of cells into the neural fold, together with its more rapid cell proliferation, leads to an increase in cell density dorsolaterally compared with the more ventromedial neural plate. These findings suggest a model in which DLHP formation may proceed through ‘buckling’ of the neuroepithelium at a dorso-ventral boundary marked by a change in cell-packing density. PMID:26079577

Full-Field Indentation Damage Measurement Using Digital Image Correlation

PubMed Central

López-Alba, Elías; Díaz-Garrido, Francisco A.

2017-01-01

A novel approach based on full-field indentation measurements to characterize and quantify the effect of contact in thin plates is presented. The proposed method has been employed to evaluate the indentation damage generated in the presence of bending deformation, resulting from the contact between a thin plate and a rigid sphere. For this purpose, the 3D Digital Image Correlation (3D-DIC) technique has been adopted to quantify the out of plane displacements at the back face of the plate. Tests were conducted using aluminum thin plates and a rigid bearing sphere to evaluate the influence of the thickness and the material behavior during contact. Information provided by the 3D-DIC technique has been employed to perform an indirect measurement of the contact area during the loading and unloading path of the test. A symmetrical distribution in the contact damage region due to the symmetry of the indenter was always observed. In the case of aluminum plates, the presence of a high level of plasticity caused shearing deformation as the load increased. Results show the full-field contact damage area for different plates’ thicknesses at different loads. The contact damage region was bigger when the thickness of the specimen increased, and therefore, bending deformation was reduced. With the proposed approach, the elastic recovery at the contact location was quantified during the unloading, as well as the remaining permanent indentation damage after releasing the load. Results show the information obtained by full-field measurements at the contact location during the test, which implies a substantial improvement compared with pointwise techniques. PMID:28773137

Parameterized Finite Element Modeling and Buckling Analysis of Six Typical Composite Grid Cylindrical Shells

NASA Astrophysics Data System (ADS)

Lai, Changliang; Wang, Junbiao; Liu, Chuang

2014-10-01

Six typical composite grid cylindrical shells are constructed by superimposing three basic types of ribs. Then buckling behavior and structural efficiency of these shells are analyzed under axial compression, pure bending, torsion and transverse bending by finite element (FE) models. The FE models are created by a parametrical FE modeling approach that defines FE models with original natural twisted geometry and orients cross-sections of beam elements exactly. And the approach is parameterized and coded by Patran Command Language (PCL). The demonstrations of FE modeling indicate the program enables efficient generation of FE models and facilitates parametric studies and design of grid shells. Using the program, the effects of helical angles on the buckling behavior of six typical grid cylindrical shells are determined. The results of these studies indicate that the triangle grid and rotated triangle grid cylindrical shell are more efficient than others under axial compression and pure bending, whereas under torsion and transverse bending, the hexagon grid cylindrical shell is most efficient. Additionally, buckling mode shapes are compared and provide an understanding of composite grid cylindrical shells that is useful in preliminary design of such structures.

Effect of Shear Deformation and Continuity on Delamination Modelling with Plate Elements

NASA Technical Reports Server (NTRS)

Glaessgen, E. H.; Riddell, W. T.; Raju, I. S.

1998-01-01

The effects of several critical assumptions and parameters on the computation of strain energy release rates for delamination and debond configurations modeled with plate elements have been quantified. The method of calculation is based on the virtual crack closure technique (VCCT), and models that model the upper and lower surface of the delamination or debond with two-dimensional (2D) plate elements rather than three-dimensional (3D) solid elements. The major advantages of the plate element modeling technique are a smaller model size and simpler geometric modeling. Specific issues that are discussed include: constraint of translational degrees of freedom, rotational degrees of freedom or both in the neighborhood of the crack tip; element order and assumed shear deformation; and continuity of material properties and section stiffness in the vicinity of the debond front, Where appropriate, the plate element analyses are compared with corresponding two-dimensional plane strain analyses.

Minimum depth of soil cover above long-span soil-steel railway bridges

NASA Astrophysics Data System (ADS)

Esmaeili, Morteza; Zakeri, Jabbar Ali; Abdulrazagh, Parisa Haji

2013-12-01

Recently, soil-steel bridges have become more commonly used as railway-highway crossings because of their economical advantages and short construction period compared with traditional bridges. The currently developed formula for determining the minimum depth of covers by existing codes is typically based on vehicle loads and non-stiffened panels and takes into consideration the geometrical shape of the metal structure to avoid the failure of soil cover above a soil-steel bridge. The effects of spans larger than 8 m or more stiffened panels due to railway loads that maintain a safe railway track have not been accounted for in the minimum cover formulas and are the subject of this paper. For this study, two-dimensional finite element (FE) analyses of four low-profile arches and four box culverts with spans larger than 8 m were performed to develop new patterns for the minimum depth of soil cover by considering the serviceability criterion of the railway track. Using the least-squares method, new formulas were then developed for low-profile arches and box culverts and were compared with Canadian Highway Bridge Design Code formulas. Finally, a series of three-dimensional (3D) finite element FE analyses were carried out to control the out-of-plane buckling in the steel plates due to the 3D pattern of train loads. The results show that the out-of-plane bending does not control the buckling behavior of the steel plates, so the proposed equations for minimum depth of cover can be appropriately used for practical purposes.

Analysis of symmetric cross-ply laminated elastic plates using a higher-order theory. I - Stress and displacement

NASA Technical Reports Server (NTRS)

Librescu, L.; Khdeir, A. A.

1988-01-01

A simple theory for bending of composite anisotropic plates that are laminated symmetrically about their mid-plane is presented. This theory incorporates transverse shear deformation and transverse normal stress as well as the higher-order effects and fulfills the static conditions on the external boundary planes. Further on, by using Levy-type solutions considered in conjunction with the state space concept, the state of stress and displacement of rectangular plates for a variety of edge conditions is determined and the results are compared to their first-order shear deformation and classical counterparts, obtained by using the same state-space technique.

Waveguiding and bending modes in a plasma photonic crystal bandgap device

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, B., E-mail: bwang17@stanford.edu; Cappelli, M. A.

2016-06-15

Waveguiding and bending modes are investigated in a fully tunable plasma photonic crystal. The plasma device actively controls the propagation of free space electromagnetic waves in the S to X band of the microwave spectrum. An array of discharge plasma tubes form a square crystal lattice exhibiting a well-defined bandgap, with individual active switching of the plasma elements to allow for waveguiding and bending modes to be generated dynamically. We show, through simulations and experiments, the existence of transverse electric (TE) mode waveguiding and bending modes.

Beta Factors for Collinear Asymmetrical Cracks Emanating from an Offset Circular Hole in a Rectangular Plate

DTIC Science & Technology

2016-05-01

Lorimer Street Fishermans Bend, Victoria 3207, Australia Telephone: 1300 333 362 © Commonwealth of Australia 2016 AR-016-732 May 2016...multiple through cracks in plates with and without holes (Final Report for 25 August 1997 – 31 July 2002). AFRL-VA-WP-TR-2004-3112, October 2004. 11. J...remote tension stress. UNCLASSIFIED DST-Group-RR-0437 25 UNCLASSIFIED Figure 15: Beta factors FcR for the right-hand crack of two collinear

The compressive failure of graphite/epoxy plates with circular holes

NASA Technical Reports Server (NTRS)

Knauss, J. F.; Starnes, J. H., Jr.; Henneke, E. G., II

1978-01-01

The behavior of fiber reinforced composite plates containing a circular cutout was characterized in terms of geometry (thickness, width, hole diameter), and material properties (bending/extensional stiffness). Results were incorporated in a data base for use by designers in determining the ultimate strength of such a structure. Two thicknesses, 24 plies and 48 plies were chosen to differentiate between buckling and strength failures due to the presence of a cutout. Consistent post-buckling strength was exhibited by both laminate configurations.

A Regime Diagram for Subduction

NASA Astrophysics Data System (ADS)

Stegman, D. R.; Farrington, R.; Capitanio, F. A.; Schellart, W. P.

2009-12-01

Regime diagrams and associated scaling relations have profoundly influenced our understanding of planetary dynamics. Previous regime diagrams characterized the regimes of stagnant-lid, small viscosity contrast, transitional, and no-convection for temperature-dependent (Moresi and Solomatov, 1995), and non-linear power law rheologies (Solomatov and Moresi, 1997) as well as stagnant-lid, sluggish-lid, and mobile-lid regimes once the finite strength of rock was considered (Moresi and Solomatov, 1998). Scalings derived from such models have been the cornerstone for parameterized models of thermal evolution of rocky planets and icy moons for the past decade. While such a theory can predict the tectonic state of a planetary body, it is still rather incomplete in regards to predicting tectonics. For example, the mobile-lid regime is unspecific as to how continuous lithospheric recycling should occur on a terrestrial planet. Towards this goal, Gerya et al., (2008) advanced a new regime diagram aiming to characterize when subduction would manifest itself as a one-sided or two-sided downwelling and either symmetric or asymmetric. Here, we present a regime diagram for the case of a single-sided, asymmetric type of subduction (most Earth-like type). Using a 3-D numerical model of a free subduction, we describe a total of 5 different styles of subduction that can possibly occur. Each style is distinguished by its upper mantle slab morphology resulting from the sinking kinematics. We provide movies to illustrate the different styles and their progressive time-evolution. In each regime, subduction is accommodated by a combination of plate advance and slab rollback, with associated motions of forward plate velocity and trench retreat, respectively. We demonstrate that the preferred subduction mode depends upon two essential controlling factors: 1) buoyancy of the downgoing plate and 2) strength of plate in resisting bending at the hinge. We propose that a variety of subduction regimes are generated primarily as a product of two mechanisms. The first mechanism is that of the competition between the weight of the slab and the strength of the plate, which can be understood in terms of the applied bending moment, and this competition results in a particular radius of curvature (for which we provide a simple scaling theory). The second mechanism is the interaction between the slab and the more viscous lower mantle, which produces each regime's distinct slab morphology. Thus, the emergence of five distinct styles of subduction is a direct consequence of the presence of the modest barrier to flow into the lower mantle. Although only 2 of these styles presently operate on Earth, the possibility exists that other modes may have been the predominant mode in the past. Based on these models, we propose that the lithosphere is the primary factor in describing key elements of the plate tectonics system over time, rather than the convecting mantle. We discuss the various factors that may have influenced secular changes in Earth's tectonic behavior, some of which may have interesting consequences for the geochemical evolution of the Earth.

Stability and natural vibration analysis of laminated plates by using a mixed element based on a refined plate theory

NASA Technical Reports Server (NTRS)

Putcha, N. S.; Reddy, J. N.

1986-01-01

A mixed shear flexible finite element, with relaxed continuity, is developed for the geometrically linear and nonlinear analysis of layered anisotropic plates. The element formulation is based on a refined higher order theory which satisfies the zero transverse shear stress boundary conditions on the top and bottom faces of the plate and requires no shear correction coefficients. The mixed finite element developed herein consists of eleven degrees of freedom per node which include three displacements, two rotations and six moment resultants. The element is evaluated for its accuracy in the analysis of the stability and vibration of anisotropic rectangular plates with different lamination schemes and boundary conditions. The mixed finite element described here for the higher order theory gives very accurate results for buckling loads and natural frequencies.

Femoral fracture repair using a locking plate technique in an adult captive polar bear (Ursus maritimus).

PubMed

Zimmerman, Dawn M; Dew, Terry; Douglass, Michael; Perez, Edward

2010-02-01

To report successful femoral fracture repair in a polar bear. Case report. Female polar bear (Ursus maritimus) 5 years and approximately 250 kg. A closed, complete, comminuted fracture of the distal midshaft femur was successfully reduced and stabilized using a compression plating technique with 2 specialized human femur plates offering axial, rotational, and bending support, and allowing the bone to share loads with the implant. Postoperative radiographs were obtained at 11.5 weeks, 11 months, and 24 months. Bone healing characterized by marked periosteal reaction was evident at 11 months with extensive remodeling evident at 24 months. No complications were noted. Distal mid shaft femoral fracture was reduced, stabilized, and healed in an adult polar bear with a locking plate technique using 2 plates. Previously, femoral fractures in polar bears were considered irreparable. Use of 2 plates applied with a locking plate technique can result in successful fracture repair despite large body weight and inability to restrict postoperative activity.

Finite element prediction on the chassis design of UniART4 racing car

NASA Astrophysics Data System (ADS)

Zaman, Z. I.; Basaruddin, K. S.; Basha, M. H.; Rahman, M. T. Abd; Daud, R.

2017-09-01

This paper presents the analysis and evaluation of the chassis design for University Automotive Racing Team No. 4 (UniART4) car based on finite element analysis. The existing UniART4 car chassis was measured and modelled geometrically using Solidwork before analysed in FEA software (ANSYS). Four types of static structural analysis were used to predict the chassis design capability under four different loading conditions; vertical bending, lateral bending, lateral torsion and horizontal lozenging. The results showed the chassis subjected to the highest stress and strain under horizontal lozenging, whereas the minimum stress and strain response was obtained under lateral bending. The present analysis result could provide valuable information in predicting the sustainability of the current UniART car chassis design.

The application of continuum damage mechanics to solve problems in geodynamics

NASA Astrophysics Data System (ADS)

Manaker, David Martin

Deformation within the Earth's lithosphere is largely controlled by the rheology of the rock. Ductile behavior in rocks is often associated with plasticity due to dislocation motion or diffusion under high pressures and temperatures. However, ductile behavior can also occur in brittle materials. An example would be cataclastic flow associated with folding at shallow crustal levels, steep subduction zones, and large-scale deformation at plate boundaries. Engineers utilize damage mechanics to model the continuum deformation of brittle materials. We utilize a modified form of damage mechanics where damage represents a reduction in frictional strength and includes a yield stress. We use this empirical approach to simulate the bending of the lithosphere. We use numerical simulations to obtain elastostatic solutions for plate bending and where the stress exceeds a yield stress, we apply damage to reduce the elastic moduli. Damage is calculated at each time step by a power-law relationship of the ratio of the yield stress to stress and the yield strain to the strain. To test our method, we apply our damage rheology to a plate deforming under applied shear, a constant bending moment, and a constant load. We simulate a wide range of behaviors from slow relaxation to instantaneous failure, over timescales that span six orders of magnitude. Stress relaxation produces elastic-perfectly plastic behavior in cases where failure does not occur. For cases of failure, we observe a rapid increase in damage leading to failure. The changes in the rate of damage accumulation in failure cases are similar to the changes in b-values of acoustic emissions observed in triaxial compression tests of fractured rock and b-value changes prior to some large earthquakes. Thus continuum damage mechanics can simulate ductile behavior due to brittle mechanisms as well as observations of laboratory experiments and seismicity.

Flexural bending-induced plumelets and their seamounts in accretionary (Japanese-style) and collisional (Tethyan-style) orogenic belts

NASA Astrophysics Data System (ADS)

Hirano, N.; Dilek, Y.

2015-12-01

Seamounts and seamount chains are common in both the upper and lower plates of active subduction zones. Their OIB-type volcanic products are distinctly different from suprasubduction zone (arc, forearc and backarc) generated volcanic rocks in terms of their compositions and mantle sources. Tectonic accretion of such seamounts into the Japanese archipelago in the NW Pacific and into subduction-accretion complexes and active margins of continents/microcontinents within the Tethyan realm during the Cretaceous played a significant role in continental growth. Seamount assemblages comprise alkaline volcanic rocks intercalated with radiolarian and hemipelagic chert, and limestone, and may also include hypabyssal dolerite and gabbro intrusions. In the Tethyan orogenic belts these seamount rocks commonly occur as km-scale blocks in mélange units beneath the late Jurassic - Cretaceous ophiolites nappes, whereas on the Japanese islands they form discrete, narrow tectonic belts within the late Jurassic - Cretaceous accretionary prism complexes. We interpret some of these OIB occurrences in the Japanese and Tethyan mountain belts as asperities in downgoing oceanic plates that formed in <10 million years before their accretion. Their magmas were generated by decompressional melting of upwelling asthenosphere, without any significant mantle plume component, and were brought to the seafloor along deep-seated brittle fractures that developed in the flexed, downgoing lithosphere as it started bending near a trench. The modern occurrences of these "petit-spot volcanoes" are well established in the northwestern Pacific plate, off the coast of Japan. The proposed mechanism of the formation of these small seamounts better explains the lack of hotspot trails associated with their occurrence in the geological record. Magmatic outputs of such flexural bending-induced plumelets should be ubiquitious in the accretionary (Japanese-style) and collisional (Tethyan-style) orogenic belts.

Bending transition in the penetration of a flexible intruder in a two-dimensional dense granular medium.

PubMed

Algarra, Nicolas; Karagiannopoulos, Panagiotis G; Lazarus, Arnaud; Vandembroucq, Damien; Kolb, Evelyne

2018-02-01

We study the quasistatic penetration of a flexible beam into a two-dimensional dense granular medium lying on a horizontal plate. Rather than a buckling-like behavior we observe a transition between a regime of crack-like penetration in which the fiber only shows small fluctuations around a stable straight geometry and a bending regime in which the fiber fully bends and advances through series of loading and unloading steps. We show that the shape reconfiguration of the fiber is controlled by a single nondimensional parameter L/L_{c}, which is the ratio of the length of the flexible beam L to L_{c}, a bending elastogranular length scale that depends on the rigidity of the fiber and on the departure from the jamming packing fraction of the granular medium. We show, moreover, that the dynamics of the bending transition in the course of the penetration experiment is gradual and is accompanied by a symmetry breaking of the granular packing fraction in the vicinity of the fiber. Together with the progressive bending of the fiber, a cavity grows downstream of the fiber and the accumulation of grains upstream of the fiber leads to the development of a jammed cluster of grains. We discuss our experimental results in the framework of a simple model of bending-induced compaction and we show that the rate of the bending transition only depends on the control parameter L/L_{c}.

Bending transition in the penetration of a flexible intruder in a two-dimensional dense granular medium

NASA Astrophysics Data System (ADS)

Algarra, Nicolas; Karagiannopoulos, Panagiotis G.; Lazarus, Arnaud; Vandembroucq, Damien; Kolb, Evelyne

2018-02-01

We study the quasistatic penetration of a flexible beam into a two-dimensional dense granular medium lying on a horizontal plate. Rather than a buckling-like behavior we observe a transition between a regime of crack-like penetration in which the fiber only shows small fluctuations around a stable straight geometry and a bending regime in which the fiber fully bends and advances through series of loading and unloading steps. We show that the shape reconfiguration of the fiber is controlled by a single nondimensional parameter L /Lc , which is the ratio of the length of the flexible beam L to Lc, a bending elastogranular length scale that depends on the rigidity of the fiber and on the departure from the jamming packing fraction of the granular medium. We show, moreover, that the dynamics of the bending transition in the course of the penetration experiment is gradual and is accompanied by a symmetry breaking of the granular packing fraction in the vicinity of the fiber. Together with the progressive bending of the fiber, a cavity grows downstream of the fiber and the accumulation of grains upstream of the fiber leads to the development of a jammed cluster of grains. We discuss our experimental results in the framework of a simple model of bending-induced compaction and we show that the rate of the bending transition only depends on the control parameter L /Lc .

A computational study of crimping and expansion of bioresorbable polymeric stents

NASA Astrophysics Data System (ADS)

Qiu, T. Y.; Song, M.; Zhao, L. G.

2018-05-01

This paper studied the mechanical performance of four bioresorbable PLLA stents, i.e., Absorb, Elixir, Igaki-Tamai and RevaMedical, during crimping and expansion using the finite element method. Abaqus CAE was used to create the geometrical models for the four stents. A tri-folded balloon was created using NX software. For the stents, elastic-plastic behaviour was used, with hardening implemented by considering the increase of yield stress with the plastic strain. The tri-folded balloon was treated as linear elastic. To simulate the crimping of stents, a set of 12 rigid plates were generated around the stents with a radially enforced displacement. During crimping, the stents were compressed from a diameter of 3 mm to 1.2 mm, with the maximum stress developed at both inner and outer sides of the U-bends. During expansion, the stent inner diameter increased to 3 mm at the peak pressure and then recoiled to different final diameters after balloon deflation due to different stent designs. The maximum stress was found again at the U-bends of stents. Diameter change, recoiling effect and radial strength/stiffness were also compared for the four stents to assess the effect of design variation on stent performance. The effect of loading rate on stent deformation was also simulated by considering the time-dependent plastic behaviour of polymeric material.

A computational study of crimping and expansion of bioresorbable polymeric stents

NASA Astrophysics Data System (ADS)

Qiu, T. Y.; Song, M.; Zhao, L. G.

2017-10-01

This paper studied the mechanical performance of four bioresorbable PLLA stents, i.e., Absorb, Elixir, Igaki-Tamai and RevaMedical, during crimping and expansion using the finite element method. Abaqus CAE was used to create the geometrical models for the four stents. A tri-folded balloon was created using NX software. For the stents, elastic-plastic behaviour was used, with hardening implemented by considering the increase of yield stress with the plastic strain. The tri-folded balloon was treated as linear elastic. To simulate the crimping of stents, a set of 12 rigid plates were generated around the stents with a radially enforced displacement. During crimping, the stents were compressed from a diameter of 3 mm to 1.2 mm, with the maximum stress developed at both inner and outer sides of the U-bends. During expansion, the stent inner diameter increased to 3 mm at the peak pressure and then recoiled to different final diameters after balloon deflation due to different stent designs. The maximum stress was found again at the U-bends of stents. Diameter change, recoiling effect and radial strength/stiffness were also compared for the four stents to assess the effect of design variation on stent performance. The effect of loading rate on stent deformation was also simulated by considering the time-dependent plastic behaviour of polymeric material.

Variations of a global constraint factor in cracked bodies under tension and bending loads

NASA Technical Reports Server (NTRS)

Newman, J. C., Jr.; Crews, J. H., Jr.; Bigelow, C. A.; Dawicke, D. S.

1994-01-01

Elastic-plastic finite-element analyses were used to calculate stresses and displacements around a crack in finite-thickness plates for an elastic-perfectly plastic material. Middle- and edge-crack specimens were analyzed under tension and bending loads. Specimens were 1.25 to 20 mm thick with various widths and crack lengths. A global constraint factor alpha(sub g), an averaged normal-stress to flow-stress ratio over the plastic region, was defined to simulate three-dimensional (3D) effects in two-dimensional (2D) models. For crack lengths and uncracked ligament lengths greater than four times the thickness, the global constraint factor was found to be nearly a unique function of a normalized stress-intensity factor (related to plastic-zone size to thickness ratio) from small- to large-scale yielding conditions for various specimen types and thickness. For crack length-to-thickness ratios less than four, the global constraint factor was specimen type, crack length and thickness dependent. Using a 2D strip-yield model and the global constraint factors, plastic-zone sizes and crack-tip displacements agreed reasonably well with the 3D analyses. For a thin sheet aluminum alloy, the critical crack-tip-opening angle during stable tearing was found to be independent of specimen type and crack length for crack length-to-thickness ratios greater than 4.

An advanced selective liquid-metal plating technique for stretchable biosensor applications.

PubMed

Li, Guangyong; Lee, Dong-Weon

2017-10-11

This paper presents a novel stretchable pulse sensor fabricated by a selective liquid-metal plating process (SLMP), which can conveniently attach to the human skin and monitor the patient's heartbeat. The liquid metal-based stretchable pulse sensor consists of polydimethylsiloxane (PDMS) thin films and liquid metal functional circuits with electronic elements that are embedded into the PDMS substrate. In order to verify the utility of the fabrication process, various complex liquid-metal patterns are achieved by using the selective wetting behavior of the reduced liquid metal on the Cu patterns of the PDMS substrate. The smallest liquid-metal pattern is approximately 2 μm in width with a uniform surface. After verification, a transparent flowing LED light with programmed circuits is realized and exhibits stable mechanical and electrical properties under various deformations (bending, twisting and stretching). Finally, based on SLMP, a wireless pulse measurement system is developed which is composed of the liquid metal-based stretchable pulse sensor, a Bluetooth module, an Arduino development board, a laptop computer and a self-programmed visualized software program. The experimental results reveal that the portable non-invasive pulse sensor has the potential to reduce costs, simplify biomedical diagnostic procedures and help patients to improve their life in the future.

Design of a Dual Waveguide Normal Incidence Tube (DWNIT) Utilizing Energy and Modal Methods

NASA Technical Reports Server (NTRS)

Betts, Juan F.; Jones, Michael G. (Technical Monitor)

2002-01-01

This report investigates the partition design of the proposed Dual Waveguide Normal Incidence Tube (DWNIT). Some advantages provided by the DWNIT are (1) Assessment of coupling relationships between resonators in close proximity, (2) Evaluation of "smart liners", (3) Experimental validation for parallel element models, and (4) Investigation of effects of simulated angles of incidence of acoustic waves. Energy models of the two chambers were developed to determine the Sound Pressure Level (SPL) drop across the two chambers, through the use of an intensity transmission function for the chamber's partition. The models allowed the chamber's lengthwise end samples to vary. The initial partition design (2" high, 16" long, 0.25" thick) was predicted to provide at least 160 dB SPL drop across the partition with a compressive model, and at least 240 dB SPL drop with a bending model using a damping loss factor of 0.01. The end chamber sample transmissions coefficients were set to 0.1. Since these results predicted more SPL drop than required, a plate thickness optimization algorithm was developed. The results of the algorithm routine indicated that a plate with the same height and length, but with a thickness of 0.1" and 0.05 structural damping loss, would provide an adequate SPL isolation between the chambers.

Epeirogeny and plate tectonics

NASA Technical Reports Server (NTRS)

Menard, H. W.

1975-01-01

Vertical motions of the earth crust and their causes are considered in relation to epeirogenic phenomena. Factors discussed include: external loading and unloading; bending at subduction zones; internal density changes; and dynamic effects of mantle motion. The relationship between epeirogeny and drift is briefly reviewed along with oceanic epeirogeny.

A kinematic model for the evolution of the Eastern California Shear Zone and Garlock Fault, Mojave Desert, California

NASA Astrophysics Data System (ADS)

Dixon, Timothy H.; Xie, Surui

2018-07-01

The Eastern California shear zone in the Mojave Desert, California, accommodates nearly a quarter of Pacific-North America plate motion. In south-central Mojave, the shear zone consists of six active faults, with the central Calico fault having the fastest slip rate. However, faults to the east of the Calico fault have larger total offsets. We explain this pattern of slip rate and total offset with a model involving a crustal block (the Mojave Block) that migrates eastward relative to a shear zone at depth whose position and orientation is fixed by the Coachella segment of the San Andreas fault (SAF), southwest of the transpressive "big bend" in the SAF. Both the shear zone and the Garlock fault are assumed to be a direct result of this restraining bend, and consequent strain redistribution. The model explains several aspects of local and regional tectonics, may apply to other transpressive continental plate boundary zones, and may improve seismic hazard estimates in these zones.

Accuracy of specimen-specific nonlinear finite element analysis for evaluation of radial diaphysis strength in cadaver material.

PubMed

Matsuura, Yusuke; Kuniyoshi, Kazuki; Suzuki, Takane; Ogawa, Yasufumi; Sukegawa, Koji; Rokkaku, Tomoyuki; Thoreson, Andrew Ryan; An, Kai-Nan; Takahashi, Kazuhisa

2015-01-01

The feasibility of a user-specific finite element model for predicting the in situ strength of the radius after implantation of bone plates for open fracture reduction was established. The effect of metal artifact in CT imaging was characterized. The results were verified against biomechanical test data. Fourteen cadaveric radii were divided into two groups: (1) intact radii for evaluating the accuracy of radial diaphysis strength predictions with finite element analysis and (2) radii with a locking plate affixed for evaluating metal artifact. All bones were imaged with CT. In the plated group, radii were first imaged with the plates affixed (for simulating digital plate removal). They were then subsequently imaged with the locking plates and screws removed (actual plate removal). Fracture strength of the radius diaphysis under axial compression was predicted with a three-dimensional, specimen-specific, nonlinear finite element analysis for both the intact and plated bones (bones with and without the plate captured in the scan). Specimens were then loaded to failure using a universal testing machine to verify the actual fracture load. In the intact group, the physical and predicted fracture loads were strongly correlated. For radii with plates affixed, the physical and predicted (simulated plate removal and actual plate removal) fracture loads were strongly correlated. This study demonstrates that our specimen-specific finite element analysis can accurately predict the strength of the radial diaphysis. The metal artifact from CT imaging was shown to produce an overestimate of strength.

[Analysis of a three-dimensional finite element model of atlas and axis complex fracture].

PubMed

Tang, X M; Liu, C; Huang, K; Zhu, G T; Sun, H L; Dai, J; Tian, J W

2018-05-22

Objective: To explored the clinical application of the three-dimensional finite element model of atlantoaxial complex fracture. Methods: A three-dimensional finite element model of cervical spine (FEM/intact) was established by software of Abaqus6.12.On the basis of this model, a three-dimensional finite element model of four types of atlantoaxial complex fracture was established: C(1) fracture (Jefferson)+ C(2) fracture (type Ⅱfracture), Jefferson+ C(2) fracture(type Ⅲfracture), Jefferson+ C(2) fracture(Hangman), Jefferson+ stable C(2) fracture (FEM/fracture). The range of motion under flexion, extension, lateral bending and axial rotation were measured and compared with the model of cervical spine. Results: The three-dimensional finite element model of four types of atlantoaxial complex fracture had the same similarity and profile.The range of motion (ROM) of different segments had different changes.Compared with those in the normal model, the ROM of C(0/1) and C(1/2) in C(1) combined Ⅱ odontoid fracture model in flexion/extension, lateral bending and rotation increased by 57.45%, 29.34%, 48.09% and 95.49%, 88.52%, 36.71%, respectively.The ROM of C(0/1) and C(1/2) in C(1) combined Ⅲodontoid fracture model in flexion/extension, lateral bending and rotation increased by 47.01%, 27.30%, 45.31% and 90.38%, 27.30%, 30.0%.The ROM of C(0/1) and C(1/2) in C(1) combined Hangman fracture model in flexion/extension, lateral bending and rotation increased by 32.68%, 79.34%, 77.62% and 60.53%, 81.20%, 21.48%, respectively.The ROM of C(0/1) and C(1/2) in C(1) combined axis fracture model in flexion/extension, lateral bending and rotation increased by 15.00%, 29.30%, 8.47% and 37.87%, 75.57%, 8.30%, respectively. Conclusions: The three-dimensional finite element model can be used to simulate the biomechanics of atlantoaxial complex fracture.The ROM of atlantoaxial complex fracture is larger than nomal model, which indicates that surgical treatment should be performed.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Oleinikov, A. I., E-mail: a.i.oleinikov@mail.ru; Bormotin, K. S., E-mail: cvmi@knastu.ru

It is shown that inverse problems of steady-state creep bending of plates in both the geometrically linear and nonlinear formulations can be represented in a variational formulation. Steady-state values of the obtained functionals corresponding to the solutions of the problems of inelastic deformation and springback are determined by applying a finite element procedure to the functionals. Optimal laws of creep deformation are formulated using the criterion of minimizing damage in the functionals of the inverse problems. The formulated problems are reduced to the problems solved by the finite element method using MSC.Marc software. Currently, forming of light metals poses tremendousmore » challenges due to their low ductility at room temperature and their unusual deformation characteristics at hot-cold work: strong asymmetry between tensile and compressive behavior, and a very pronounced anisotropy. We used the constitutive models of steady-state creep of initially transverse isotropy structural materials the kind of the stress state has influence. The paper gives basics of the developed computer-aided system of design, modeling, and electronic simulation targeting the processes of manufacture of wing integral panels. The modeling results can be used to calculate the die tooling, determine the panel processibility, and control panel rejection in the course of forming.« less

The inverse problems of wing panel manufacture processes

NASA Astrophysics Data System (ADS)

Oleinikov, A. I.; Bormotin, K. S.

2013-12-01

It is shown that inverse problems of steady-state creep bending of plates in both the geometrically linear and nonlinear formulations can be represented in a variational formulation. Steady-state values of the obtained functionals corresponding to the solutions of the problems of inelastic deformation and springback are determined by applying a finite element procedure to the functionals. Optimal laws of creep deformation are formulated using the criterion of minimizing damage in the functionals of the inverse problems. The formulated problems are reduced to the problems solved by the finite element method using MSC.Marc software. Currently, forming of light metals poses tremendous challenges due to their low ductility at room temperature and their unusual deformation characteristics at hot-cold work: strong asymmetry between tensile and compressive behavior, and a very pronounced anisotropy. We used the constitutive models of steady-state creep of initially transverse isotropy structural materials the kind of the stress state has influence. The paper gives basics of the developed computer-aided system of design, modeling, and electronic simulation targeting the processes of manufacture of wing integral panels. The modeling results can be used to calculate the die tooling, determine the panel processibility, and control panel rejection in the course of forming.

Lithospheric bending at subduction zones based on depth soundings and satellite gravity

NASA Technical Reports Server (NTRS)

Levitt, Daniel A.; Sandwell, David T.

1995-01-01

A global study of trench flexure was performed by simultaneously modeling 117 bathymetric profiles (original depth soundings) and satellite-derived gravity profiles. A thin, elastic plate flexure model was fit to each bathymetry/gravity profile by minimization of the L(sub 1) norm. The six model parameters were regional depth, regional gravity, trench axis location, flexural wavelength, flexural amplitude, and lithospheric density. A regional tilt parameter was not required after correcting for age-related trend using a new high-resolution age map. Estimates of the density parameter confirm that most outer rises are uncompensated. We find that flexural wavelength is not an accurate estimate of plate thickness because of the high curvatures observed at a majority of trenches. As in previous studies, we find that the gravity data favor a longer-wavelength flexure than the bathymetry data. A joint topography-gravity modeling scheme and fit criteria are used to limit acceptable parameter values to models for which topography and gravity yield consistent results. Even after the elastic thicknesses are converted to mechanical thicknesses using the yield strength envelope model, residual scatter obscures the systematic increase of mechanical thickness with age; perhaps this reflects the combination of uncertainties inherent in estimating flexural wavelength, such as extreme inelastic bending and accumulated thermoelastic stress. The bending moment needed to support the trench and outer rise topography increases by a factor of 10 as lithospheric age increases from 20 to 150 Ma; this reflects the increase in saturation bending moment that the lithosphere can maintain. Using a stiff, dry-olivine rheology, we find that the lithosphere of the GDH1 thermal model (Stein and Stein, 1992) is too hot and thin to maintain the observed bending moments. Moreover, the regional depth seaward of the oldest trenches (approximately 150 Ma) exceeds the GDH1 model depths by about 400 m.

Flexible organic transistors and circuits with extreme bending stability

NASA Astrophysics Data System (ADS)

Sekitani, Tsuyoshi; Zschieschang, Ute; Klauk, Hagen; Someya, Takao

2010-12-01

Flexible electronic circuits are an essential prerequisite for the development of rollable displays, conformable sensors, biodegradable electronics and other applications with unconventional form factors. The smallest radius into which a circuit can be bent is typically several millimetres, limited by strain-induced damage to the active circuit elements. Bending-induced damage can be avoided by placing the circuit elements on rigid islands connected by stretchable wires, but the presence of rigid areas within the substrate plane limits the bending radius. Here we demonstrate organic transistors and complementary circuits that continue to operate without degradation while being folded into a radius of 100μm. This enormous flexibility and bending stability is enabled by a very thin plastic substrate (12.5μm), an atomically smooth planarization coating and a hybrid encapsulation stack that places the transistors in the neutral strain position. We demonstrate a potential application as a catheter with a sheet of transistors and sensors wrapped around it that enables the spatially resolved measurement of physical or chemical properties inside long, narrow tubes.

[Augmentation technique on the proximal humerus].

PubMed

Scola, A; Gebhard, F; Röderer, G

2015-09-01

The treatment of osteoporotic fractures is still a challenge. The advantages of augmentation with respect to primary in vitro stability and the clinical use for the proximal humerus are presented in this article. In this study six paired human humeri were randomized into an augmented and a non-augmented group. Osteosynthesis was performed with a PHILOS plate (Synthes®). In the augmented group the two screws finding purchase in the weakest cancellous bone were augmented. The specimens were tested in a 3-part fracture model in a varus bending test. The augmented PHILOS plates withstood significantly more load cycles until failure. The correlation to bone mineral density (BMD) showed that augmentation could partially compensate for low BMD. The augmentation of the screws in locked plating in a proximal humerus fracture model is effective in improving the primary stability in a cyclic varus bending test. The targeted augmentation of two particular screws in a region of low bone quality within the humeral head was almost as effective as four screws with twice the amount of bone cement. Screw augmentation combined with a knowledge of the local bone quality could be more effective in enhancing the primary stability of a proximal humerus locking plate because the effect of augmentation can be exploited more effectively limiting it to the degree required. The technique of augmentation is simple and can be applied in open and minimally invasive procedures. When the correct procedure is used, complications (cement leakage into the joint) can be avoided.

TESTING AND ACCEPTANCE OF FUEL PLATES FOR RERTR FUEL DEVELOPMENT EXPERIMENTS

DOE Office of Scientific and Technical Information (OSTI.GOV)

J.M. Wight; G.A. Moore; S.C. Taylor

2008-10-01

This paper discusses how candidate fuel plates for RERTR Fuel Development experiments are examined and tested for acceptance prior to reactor insertion. These tests include destructive and nondestructive examinations (DE and NDE). The DE includes blister annealing for dispersion fuel plates, bend testing of adjacent cladding, and microscopic examination of archive fuel plates. The NDE includes Ultrasonic (UT) scanning and radiography. UT tests include an ultrasonic scan for areas of “debonds” and a high frequency ultrasonic scan to determine the "minimum cladding" over the fuel. Radiography inspections include identifying fuel outside of the maximum fuel zone and measurements and calculationsmore » for fuel density. Details of each test are provided and acceptance criteria are defined. These tests help to provide a high level of confidence the fuel plate will perform in the reactor without a breach in the cladding.« less

Ultralight shape-recovering plate mechanical metamaterials

NASA Astrophysics Data System (ADS)

Davami, Keivan; Zhao, Lin; Lu, Eric; Cortes, John; Lin, Chen; Lilley, Drew E.; Purohit, Prashant K.; Bargatin, Igor

2015-12-01

Unusual mechanical properties of mechanical metamaterials are determined by their carefully designed and tightly controlled geometry at the macro- or nanoscale. We introduce a class of nanoscale mechanical metamaterials created by forming continuous corrugated plates out of ultrathin films. Using a periodic three-dimensional architecture characteristic of mechanical metamaterials, we fabricate free-standing plates up to 2 cm in size out of aluminium oxide films as thin as 25 nm. The plates are formed by atomic layer deposition of ultrathin alumina films on a lithographically patterned silicon wafer, followed by complete removal of the silicon substrate. Unlike unpatterned ultrathin films, which tend to warp or even roll up because of residual stress gradients, our plate metamaterials can be engineered to be extremely flat. They weigh as little as 0.1 g cm-2 and have the ability to `pop-back' to their original shape without damage even after undergoing multiple sharp bends of more than 90°.

Application of laser ranging and VLBI data to a study of plate tectonic driving forces. [finite element method

NASA Technical Reports Server (NTRS)

Solomon, S. C.

1980-01-01

The measurability of changes in plate driving or resistive forces associated with plate boundary earthquakes by laser rangefinding or VLBI is considered with emphasis on those aspects of plate forces that can be characterized by such measurements. Topics covered include: (1) analytic solutions for two dimensional stress diffusion in a plate following earthquake faulting on a finite fault; (2) two dimensional finite-element solutions for the global state of stress at the Earth's surface for possible plate driving forces; and (3) finite-element solutions for three dimensional stress diffusion in a viscoelastic Earth following earthquake faulting.

Wavelet Spectral Finite Elements for Wave Propagation in Composite Plates with Damages - Years 3-4

DTIC Science & Technology

2014-05-23

study of Lamb wave interactions with holes and through thickness defects in thin metal plates . Distribution Code A: Approved for public release...Propagation in Composite Plates with Damages - Years 3-4 5a. CONTRACT NUMBER 5b. GRANT NUMBER FA23861214005 5c. PROGRAM ELEMENT NUMBER 6...14. ABSTRACT The objective of the proposed efforts: -Formulated Wavelet Spectral element for a healthy composite plates and used the formulated

A comparison of deformation and failure behaviors of AZ31 and E-form Mg alloys under V-bending test

NASA Astrophysics Data System (ADS)

Choi, Shi-Hoon; Singh, Jaiveer; Kim, Min-Seong; Yoon, Jeong-Whan

2016-08-01

Deformation and failure behaviors of magnesium (Mg) alloys (AZ31 and E-form) were investigated using V-bending test. Formability of these Mg alloys was discussed in terms of minimum bending radius. Microtexture evolution in the deformed Mg alloys was examined via electron back-scattered diffraction (EBSD) technique. Two level simulation technique which combined continuum finite element method (FEM) and crystal plasticity FEM successfully simulated the microtexture evolution in Mg alloys during V-bending test. The effect of deformation twinning on the failure in Mg alloys was also examined.

An experimental-theoretical study of free vibrations of plates on elastic point supports

NASA Technical Reports Server (NTRS)

Leuner, T. R.

1972-01-01

A theoretical and experimental study is made to investigate the effect on plate vibrations of varying the stiffness of corner elastic point supports. A theoretical model is developed using a Rayleigh-Ritz analysis which approximates the plate mode shapes as products of free-free beam modes. The elastic point supports are modelled both as massless translational springs, and springs with tip masses. The tip masses are included to better represent the experimental supports. An experiment is constructed using the bending stiffness of horizontal beams to support a square plate at its four corners. The stiffness of these supports can be varied over such a range that the plate fundamental frequency is lowered to 40% of the rigid support frequency. The variation with support stiffness of the frequencies of the first eight plate modes is measured, and compared with the theoretical results. The plate mode shapes for rigid supports are analyzed using holographic interferometry. There is excellent agreement between the theoretical and experimental results, except for high plate modes where the theoretical model is demonstrated to be inadequate.

Variations in lithospheric thickness on Venus

NASA Technical Reports Server (NTRS)

Johnson, C. L.; Sandwell, David T.

1992-01-01

Recent analyses of Magellan data have indicated many regions exhibiting topograhic flexure. On Venus, flexure is associated predominantly with coronae and the chasmata with Aphrodite Terra. Modeling of these flexural signatures allows the elastic and mechanical thickness of the lithosphere to be estimated. In areas where the lithosphere is flexed beyond its elastic limit the saturation moment provides information on the strength of the lithosphere. Modeling of 12 flexural features on Venus has indicated lithospheric thicknesses comparable with terrestrial values. This has important implications for the venusian heat budget. Flexure of a thin elastic plate due simultaneously to a line load on a continuous plate and a bending moment applied to the end of a broken plate is considered. The mean radius and regional topographic gradient are also included in the model. Features with a large radius of curvature were selected so that a two-dimensional approximation could be used. Comparisons with an axisymmetric model were made for some features to check the validity of the two-dimensional assumption. The best-fit elastic thickness was found for each profile crossing a given flexural feature. In addition, the surface stress and bending moment at the first zero crossing of each profile were also calculated. Flexural amplitudes and elastic thicknesses obtained for 12 features vary significantly. Three examples of the model fitting procedures are discussed.

New Variational Formulations of Hybrid Stress Elements

NASA Technical Reports Server (NTRS)

Pian, T. H. H.; Sumihara, K.; Kang, D.

1984-01-01

In the variational formulations of finite elements by the Hu-Washizu and Hellinger-Reissner principles the stress equilibrium condition is maintained by the inclusion of internal displacements which function as the Lagrange multipliers for the constraints. These versions permit the use of natural coordinates and the relaxation of the equilibrium conditions and render considerable improvements in the assumed stress hybrid elements. These include the derivation of invariant hybrid elements which possess the ideal qualities such as minimum sensitivity to geometric distortions, minimum number of independent stress parameters, rank sufficient, and ability to represent constant strain states and bending moments. Another application is the formulation of semiLoof thin shell elements which can yield excellent results for many severe test cases because the rigid body nodes, the momentless membrane strains, and the inextensional bending modes are all represented.

Flexure and the role of inplane force around coronae on Venus

NASA Technical Reports Server (NTRS)

Brown, C. David; Grimm, Robert E.

1993-01-01

Large coronae on Venus, such as Artemis and Latona, are rimmed by conspicuous trenches and associated outer rises. Sandwell and Schubert have observed that these systems resemble terrestrial subduction zones in planform and have succeeded in fitting an elastic plate bending equation to the inferred flexural topography. However, the first zero crossing bending moments required are -2.5 x 10(exp 17) N for Artemis and -5.0 x 10(exp 16) N for Latona. Since these moments are similar in magnitude to those of subducting slabs on Earth, a rollback subduction mechanism was proposed to explain the flexure around the largest coronae, although a differential thermal subsidence model is sufficient to account for the topography around some coronae. The purpose is to investigate the effect of inplane force as a possible alternative to large applied moments in producing flexure at Artemis and Latona. The close correlation of gravity to topography on Venus implies the absence of a low viscosity zone and the strong coupling of the lithosphere to mantle convection. If coronae are the surface manifestations of mantle plumes, they may be the sites of active convective stress coupling. As the upwelling reaches the lithosphere, it spreads radially outward, inducing shear tractions on the base of the plate. In addition, the hot, expanding corona may load the surrounding plate horizonally. Both the basal shear stresses and radial loading can be treated as an equivalent compressive inplane force in the mechanical lithosphere, which contributes to the bending of the outlying plate. Using a model that relates inplane force to the measured gravity anomalies, a rough value of the inplane force at Artemis was calculated. Recent Pioneer Venus spherical harmonic gravity models indicate a geoid anomaly of about 75 m over Artemis, which corresponds to an estimated inplane force on the order of -1x10(exp 13) N/m. The gravity model is unable to resolve Latona, but an inplane force of similar dimensions is assumed. The maximum possible inplane force based on the expected rheology can be constrained by using the approximate 5 K/km thermal gradient inferred from the best fit 30 km elastic plate at Artemis and Latona. For a dry olivine flow law in the upper mantle, the compressional load limit of the 60 km thick mechanical lithosphere is -4 x 10(exp 13) N/m. This value is equivalent to a load of -8 x 10(exp 13) N/m on a 30 km thick elastic plate.

Experimental and Numerical Investigation on Micro-Bending of AISI 304 Sheet Metal Using a Low Power Nanosecond Laser

NASA Astrophysics Data System (ADS)

Paramasivan, K.; Das, Sandip; Marimuthu, Sundar; Misra, Dipten

2018-06-01

The aim of this experimental study is to identify and characterize the response related to the effects of process parameters in terms of bending angle for micro-bending of AISI 304 sheet using a low power Nd:YVO4 laser source. Numerical simulation is also carried out through a coupled thermo-mechanical formulation with finite element method using COMSOL MULTIPHYSICS. The developed numerical simulation indicates that bending is caused by temperature gradient mechanism in the present investigation involving laser micro-bending. The results of experiment indicate that bending angle increases with laser power, number of irradiations, and decreases with increase in scanning speed. Moreover, average bending angle increases with number of laser passes and edge effect, defined in terms of relative variation of bending angle (RBAV), decreases monotonically with the number of laser scans. The substrate is damaged over a width of about 80 μm due to the high temperatures experienced during laser forming at a low scanning speed.

Effect of inherited structures on strike-slip plate boundaries: insight from analogue modelling of the central Levant Fracture System, Lebanon

NASA Astrophysics Data System (ADS)

Ghalayini, Ramadan; Daniel, Jean-Marc; Homberg, Catherine; Nader, Fadi

2015-04-01

Analogue sandbox modeling is a tool to simulate deformation style and structural evolution of sedimentary basins. The initial goal is to test what is the effect of inherited and crustal structures on the propagation, evolution, and final geometry of major strike-slip faults at the boundary between two tectonic plates. For this purpose, we have undertaken a series of analogue models to validate and reproduce the structures of the Levant Fracture System, a major NNE-SSW sinistral strike-slip fault forming the boundary between the Arabian and African plates. Onshore observations and recent high quality 3D seismic data in the Levant Basin offshore Lebanon demonstrated that Mesozoic ENE striking normal faults were reactivated into dextral strike-slip faults during the Late Miocene till present day activity of the plate boundary which shows a major restraining bend in Lebanon with a ~ 30°clockwise rotation in its trend. Experimental parameters consisted of a silicone layer at the base simulating the ductile crust, overlain by intercalated quartz sand and glass sand layers. Pre-existing structures were simulated by creating a graben in the silicone below the sand at an oblique (>60°) angle to the main throughgoing strike-slip fault. The latter contains a small stepover at depth to create transpression during sinistral strike-slip movement and consequently result in mountain building similarly to modern day Lebanon. Strike-slip movement and compression were regulated by steady-speed computer-controlled engines and the model was scanned using a CT-scanner continuously while deforming to have a final 4D model of the system. Results showed that existing normal faults were reactivated into dextral strike-slip faults as the sinistral movement between the two plates accumulated. Notably, the resulting restraining bend is asymmetric and segmented into two different compartments with differing geometries. One compartment shows a box fold anticline, while the second shows an asymmetric anticline. Thus, analogue modeling has validated observation in seismic data and onshore geology whereby Mount Lebanon and adjacent folds exhibit similar compartmentalization and geometric dissimilarities along the Levant Fracture System. We suggest that the presence of inherited structures will affect to a certain extent the geometry of restraining bends and control the evolution of large strike-slip faults passing through.

Mid-Tertiary magmatism in western Big Bend National Park, Texas, U.S.A.: Evolution of basaltic source regions and generation of peralkaline rhyolite

NASA Astrophysics Data System (ADS)

Parker, Don F.; Ren, Minghua; Adams, David T.; Tsai, Heng; Long, Leon E.

2012-07-01

Tertiary magmatism in the Big Bend region of southwestern Texas spanned 47 to 17 Ma and included representatives of all three phases (Early, Main and Late) of the Trans-Pecos magmatic province. Early phase magmatism was manifested in the Alamo Creek Basalt, an alkalic lava series ranging from basalt to benmoreite, and silicic alkalic intrusions of the Christmas Mountains. Main phase magmatism in the late Eocene/early Oligocene produced Bee Mountain Basalt, a lava series ranging from hawaiite and potassic trachybasalt to latite, widespread trachytic lavas of Tule Mountain Trachyte and silicic rocks associated with the Pine Mountain Caldera in the Chisos Mountains. Late main phase magmatism produced trachyte lava and numerous dome complexes of peralkaline Burro Mesa Rhyolite (~ 29 Ma) in western Big Bend National Park. Late stage basaltic magmatism is sparsely represented by a few lavas in the Big Bend Park area, the adjacent Black Gap area and, most notably, in the nearby Bofecillos Mountains, where alkalic basaltic rocks were emplaced as lava and dikes concurrent with active normal faulting. Trace element modeling, Nd isotope ratios and calculated depths of segregation for estimated ancestral basaltic magmas suggest that Alamo Creek basalts (ɛNdt ~ 6.15 to 2.33) were derived from depths (~ 120 to 90 km) near the lithosphere/asthenosphere boundary at temperatures of ~ 1600 to1560 °C, whereas primitive Bee Mountain basalts (ɛNdt ~ 0.285 to - 1.20) may have been segregated at shallower depths (~ 80 to 50 km) and lower temperatures (~ 1520 to 1430 °C) within the continental lithosphere. Nb/La versus Ba/La plots suggest that all were derived from OIB-modified continental lithosphere. Late stage basaltic rocks from the Bofecillos Mountains may indicate a return to source depths and temperatures similar to those calculated for Alamo Creek Basalt primitive magmas. We suggest that a zone of melting ascended into the continental lithosphere during main-phase activity and then descended as magmatism died out. Variation within Burro Mesa Rhyolite is best explained by fractional crystallization of a mix of alkali feldspar, fayalite and Fe-Ti oxide. Comendite of the Burro Mesa Rhyolite evolved from trachyte as batches in relatively small independent magma systems, as suggested by widespread occurrence of trachytic magma enclaves within Burro Mesa lava and results of fractionation modeling. Trachyte may have been derived by fractional crystallization of intermediate magma similar to that erupted as part of Bee Mountain Basalt. ɛNdt values of trachyte lava (0.745) and two samples of Burro Mesa Rhyolite (- 0.52 and 1.52) are consistent with the above models. In all, ~ 5 wt.% comendite may be produced from 100 parts of parental trachybasalt. Negative Nb anomalies in some Bee Mountain, Tule Mountain Trachyte and Burro Mesa incompatible element plots may have been inherited from lithospheric mantle rather than from a descending plate associated with subduction. Late phase basalts lack such a Nb anomaly, as do all of our Alamo Creek analyses but one. Even if some slab fluids partially metasomatized lithospheric mantle, these igneous rocks are much more typical of continental rifts than continental arcs. We relate Big Bend magmatism to asthenospheric mantle upwelling accompanying foundering of the subducted Farallon slab as the convergence rate between the North American and the Farallon plates decreased beginning about 50 Ma. Upwelling asthenosphere heated the base of the continental lithosphere, producing the Alamo Creek series; magmatism climaxed with main phase magmatism generated within middle continental lithosphere, and then, accompanying regional extension, gradually died out by 18 Ma.

Computational models for the nonlinear analysis of reinforced concrete plates

NASA Technical Reports Server (NTRS)

Hinton, E.; Rahman, H. H. A.; Huq, M. M.

1980-01-01

A finite element computational model for the nonlinear analysis of reinforced concrete solid, stiffened and cellular plates is briefly outlined. Typically, Mindlin elements are used to model the plates whereas eccentric Timoshenko elements are adopted to represent the beams. The layering technique, common in the analysis of reinforced concrete flexural systems, is incorporated in the model. The proposed model provides an inexpensive and reasonably accurate approach which can be extended for use with voided plates.

Tensile behaviors of three-dimensionally free-formable titanium mesh plates for bone graft applications

NASA Astrophysics Data System (ADS)

He, Jianmei

2017-11-01

Present metal artificial bones for bone grafts have the problems like too heavy and excessive elastic modulus compared with natural bones. In this study, three-dimensionally (3D) free-formable titanium mesh plates for bone graft applications was introduced to improve these problems. Fundamental mesh shapes and patterns were designed under different base shapes and design parameters through three dimensional CAD tools from higher flexibility and strength points of view. Based on the designed mesh shape and patterns, sample specimens of titanium mesh plates with different base shapes and design variables were manufactured through laser processing. Tensile properties of the sample titanium mesh plates like volume density, tensile elastic modulus were experimentally and analytically evaluated. Experimental results showed that such titanium mesh plates had much higher flexibility and their mechanical properties could be controlled to close to the natural bones. More details on the mechanical properties of titanium mesh plates including compression, bending, torsion and durability will be carried out in future study.

Free vibration of rectangular plates with a small initial curvature

NASA Technical Reports Server (NTRS)

Adeniji-Fashola, A. A.; Oyediran, A. A.

1988-01-01

The method of matched asymptotic expansions is used to solve the transverse free vibration of a slightly curved, thin rectangular plate. Analytical results for natural frequencies and mode shapes are presented in the limit when the dimensionless bending rigidity, epsilon, is small compared with in-plane forces. Results for different boundary conditions are obtained when the initial deflection is: (1) a polynomial in both directions, and (2) the product of a polynomial and a trigonometric function, and arbitrary. For the arbitrary initial deflection case, the Fourier series technique is used to define the initial deflection. The results obtained show that the natural frequencies of vibration of slightly curved plates are coincident with those of perfectly flat, prestressed rectangular plates. However, the eigenmodes are very different from those of initially flat prestressed rectangular plates. The total deflection is found to be the sum of the initial deflection, the deflection resulting from the solution of the flat plate problem, and the deflection resulting from the static problem.

Comparative analysis of torsional and bending behavior through finite-element models of 5 Ni-Ti endodontic instruments.

PubMed

Arbab-Chirani, Reza; Chevalier, Valérie; Arbab-Chirani, Shabnam; Calloch, Sylvain

2011-01-01

The objectives of this study were to compare numerically the bending and torsional mechanical behavior of 5 endodontic rotary Ni-Ti instruments with equivalent size and various designs for tapers, pitch, and cutting blades.First, the geometries of Hero (20/0.06), HeroShaper (20/0.06), ProFile (20/0.06), Mtwo (20/0.06), and ProTaper F1 were generated by finite element code. Then, the 2 most representative clinical loadings, i.e., bending and torsion, were studied with an ad hoc model for the superelasticity of Ni-Ti. Bending was generated by tip deflection and torsion by a constant twist-angle of the tip. Mechanical behavior of these 5 endodontic rotary Ni-Ti instruments could be evaluated and compared. Protaper F1 presented the greatest level of bending stress and torque. Hero and HeroShaper were more rigid than ProFile and Mtwo. This numerical comparison evaluated the effects of the geometrical parameters on the instrumental mechanical behavior. The 5 endodontic instruments, investigated in the present study, do not have the same bending and torsional mechanical behavior. Each clinician must be aware of these behavior differences so as to use the adequate file according to the clinical situation and to the manufacturer's recommendations. Copyright © 2011 Mosby, Inc. All rights reserved.

Buckling and weight optimization for non-coupled antisymmetric laminates

NASA Astrophysics Data System (ADS)

Bhatnagar, Aditi

This research work describes the application of genetic algorithms to weight minimization and buckling load maximization of the non-coupled antisymmetric composite laminated plates. Previous studies of composite tailoring were limited to symmetric and balanced laminates. With the availability of many methodologies for composite tailoring, genetic algorithm is preferably used because of its ability to handle discrete design variable and attain multiple near optimum design solutions. A comparative study is made between optimum symmetric-balanced laminate designs and optimum non-coupled antisymmetric laminate designs, both of which are subjected to biaxial in-plane compressive loads. With the implementation of various genetic algorithm operators such as selection, crossover and mutation, critical buckling load factors are obtained for the optimum stacking sequence for both types of laminates. The mechanical properties for non-coupled antisymmetric laminates is independent of all types of coupling effects such as bending-twisting coupling, bending-extension coupling, and shear-extension coupling, thus giving the laminate a non-coupling behavior. This is in contrast to that of symmetric-balanced laminates where finite bending-twisting coupling terms are present. Optimized laminate layups satisfying the constraints of balance, buckling and adjoining were obtained for two types of graphite epoxy rectangular composite laminated plates. The current research augments the laminate thickness minimization designs with both odd and even number of layers, and the optimum buckling load maximization designs by the introduction of non-coupled antisymmetric laminates.

A new perspective on the geometry of the San Andreas Fault in southern California and its relationship to lithospheric structure

USGS Publications Warehouse

Fuis, Gary S.; Scheirer, Daniel S.; Langenheim, Victoria; Kohler, Monica D.

2012-01-01

The widely held perception that the San Andreas fault (SAF) is vertical or steeply dipping in most places in southern California may not be correct. From studies of potential‐field data, active‐source imaging, and seismicity, the dip of the SAF is significantly nonvertical in many locations. The direction of dip appears to change in a systematic way through the Transverse Ranges: moderately southwest (55°–75°) in the western bend of the SAF in the Transverse Ranges (Big Bend); vertical to steep in the Mojave Desert; and moderately northeast (37°–65°) in a region extending from San Bernardino to the Salton Sea, spanning the eastern bend of the SAF in the Transverse Ranges. The shape of the modeled SAF is crudely that of a propeller. If confirmed by further studies, the geometry of the modeled SAF would have important implications for tectonics and strong ground motions from SAF earthquakes. The SAF can be traced or projected through the crust to the north side of a well documented high‐velocity body (HVB) in the upper mantle beneath the Transverse Ranges. The north side of this HVB may be an extension of the plate boundary into the mantle, and the HVB would appear to be part of the Pacific plate.

Piezoelectric film load cell robot collision detector

DOEpatents

Lembke, J.R.

1988-03-15

A piezoelectric load cell which can be utilized for detecting collisions and obstruction of a robot arm end effector includes a force sensing element of metallized polyvinylidene fluoride (PVDF) film. The piezoelectric film sensing element and a resilient support pad are clamped in compression between upper and lower plates. The lower plate has a central recess in its upper face for supporting the support pad and sensing element, while the upper plate has a corresponding central projection formed on its lower face for bearing on the sensing element and support pad. The upper and lower plates are dowelled together for concentric alignment and screwed together. The upper and lower plates are also adapted for mounting between the robot arm wrist and end effector. 3 figs.

Piezoelectric film load cell robot collision detector

DOEpatents

Lembke, John R.

1989-04-18

A piezoelectric load cell which can be utilized for detecting collisions and obstruction of a robot arm end effector includes a force sensing element of metallized polyvinylidene fluoride (PVDF) film. The piezoelectric film sensing element and a resilient support pad are clamped in compression between upper and lower plates. The lower plate has a central recess in its upper face for supporting the support pad and sensing element, while the upper plate has a corresponding central projection formed on its lower face for bearing on the sensing element and support pad. The upper and lower plates are dowelled together for concentric alignment and screwed together. The upper and lower plates are also adapted for mounting between the robot arm wrist and end effector.

Piezoelectric film load cell robot collision detector

DOEpatents

Lembke, J.R.

1989-04-18

A piezoelectric load cell which can be utilized for detecting collisions and obstruction of a robot arm end effector includes a force sensing element of metallized polyvinylidene fluoride (PVDF) film. The piezoelectric film sensing element and a resilient support pad are clamped in compression between upper and lower plates. The lower plate has a central recess in its upper face for supporting the support pad and sensing element, while the upper plate has a corresponding central projection formed on its lower face for bearing on the sensing element and support pad. The upper and lower plates are doweled together for concentric alignment and screwed together. The upper and lower plates are also adapted for mounting between the robot arm wrist and end effector. 3 figs.

P protein in the phloem of Cucurbita. II. The P protein of mature sieve elements.

PubMed

Cronshaw, J; Esau, K

1968-08-01

During maturation of sieve elements in Cucurbita maxima Duchesne, the P-protein bodies (slime bodies) usually disperse in the tonoplast-free cell. In some sieve elements the P-protein bodies fail to disperse. The occurrence of dispersal or nondispersal of P-protein bodies can be related to the position of the sieve elements in the stem or petiole. In the sieve elements within the vascular bundle the bodies normally disperse; in the extrafascicular sieve elements the bodies often fail to disperse. Extrafascicular sieve elements showing partial dispersal also occur. The appearance of the sieve plate in fixed material is related to the degree of dispersal or nondispersal of the P-protein bodies. In sieve elements in which complete dispersal occurs the sieve plate usually has a substantial deposit of callose, and the sieve-plate pores are filled with P protein. In sieve elements containing nondispersing P-protein bodies the sieve plate bears little or no callose, and its pores usually are essentially "open." The dispersed P-protein components may aggregate into loosely organized "strands," which sometimes extend vertically through the cell and continue through the sieve-plate pores; but they may be oriented otherwise in the cell, even transversely.

Three-flat test with plates in horizontal posture

DOE Office of Scientific and Technical Information (OSTI.GOV)

Vannoni, Maurizio; Molesini, Giuseppe

2008-04-20

Measuring flats in the horizontal posture with interferometers is analyzed in detail, taking into account the sag produced by gravity. A mathematical expression of the bending is provided for a plate supported at three unevenly spaced locations along the edge. It is shown that the azimuthal terms of the deformation can be recovered from a three-flat measuring procedure, while the pure radial terms can only be estimated. The effectiveness of the iterative algorithm for data processing is also demonstrated. Experimental comparison on a set of three flats in horizontal and upright posture is provided.

Numerical Analysis of the Bending Properties of Cathay Poplar Glulam

PubMed Central

Gao, Ying; Wu, Yuxuan; Zhu, Xudong; Zhu, Lei; Yu, Zhiming; Wu, Yong

2015-01-01

This paper presents the formulae and finite element analysis models for predicting the Modulus of Elastic (MOE) and Modulus of Rupture (MOR) of Cathay poplar finger-jointed glulam. The formula of the MOE predicts the MOE of Cathay poplar glulam glued with one-component polyurethane precisely. Three formulae are used to predict the MOR, and Equation (12) predicts the MOR of Cathay poplar glulam precisely. The finite element analysis simulation results of both the MOE and MOR are similar to the experimental results. The predicted results of the finite element analysis are shown to be more accurate than those of the formulae, because the finite element analysis considers the glue layers, but the formulae do not. Three types of typical failure modes due to bending were summarized. The bending properties of Cathay poplar glulam were compared to those of Douglas fir glulam. The results show that Cathay poplar glulam has a lower stiffness, but a marginally higher strength. One-component polyurethane adhesive is shown to be more effective than resorcinol formaldehyde resin adhesive for Cathay poplar glulam. This study shows that Cathay poplar has the potential to be a glulam material in China. PMID:28793619

Capacitively readout multi-element sensor array with common-mode cancellation

DOEpatents

Britton, Jr., Charles L.; Warmack, Robert J.; Bryan, William L.; Jones, Robert L.; Oden, Patrick Ian; Thundat, Thomas

2001-01-01

An improved multi-element apparatus for detecting the presence of at least one chemical, biological or physical component in a monitored area comprising an array or single set of the following elements: a capacitive transducer having at least one cantilever spring element secured thereto, the cantilever element having an area thereof coated with a chemical having an affinity for the component to be detected; a pick-up plate positioned adjacent to the cantilever element at a distance such that a capacitance between the cantilever element and the pick-up plate changes as the distance between the cantilever element and the pick-up plate varies, the change in capacitance being a measurable variation; a detection means for measuring the measurable variation in the capacitance between the cantilever element and the pick-up plate that forms a measurement channel signal; and at least one feedback cantilever spring element positioned apart from the coated cantilever element, the cantilever element substantially unaffected by the component being monitored and providing a reference channel signal to the detection means that achieves a common mode cancellation between the measurement channel signal and reference channel signal.

Seismicity and Structure of the Incoming Pacific Plate Subducting into the Japan Trench off Miyagi

NASA Astrophysics Data System (ADS)

Obana, K.; Fujie, G.; Kodaira, S.; Takahashi, T.; Yamamoto, Y.; Sato, T.; Yamashita, M.; Nakamura, Y.; Miura, S.

2015-12-01

Stresses within the oceanic plate in trench axis and outer-rise region have been characterized by shallow extension and deep compression due to the bending of the plate subducting into the trench. The stress state within the incoming/subducting oceanic plate is an important factor not only for the occurrence of shallow intraplate normal-faulting earthquakes in the trench-outer rise region but also the hydration of the oceanic plate through the shallow normal faults cutting the oceanic lithosphere. We investigate seismic velocity structure and stress state within the incoming/subducting Pacific Plate in the Japan Trench based on the OBS aftershock observations for the December 2012 intraplate doublet, which consists of a deep reverse faulting (Mw 7.2) and a shallow normal faulting (Mw 7.2) earthquake, in the Japan Trench off Miyagi. Hypocenter locations and seismic velocity structures were estimated from the arrival time data of about 3000 earthquakes by using double-difference tomography method (Zhang and Thurber, 2003). Also, focal mechanisms were estimated from first motion polarities by using the program HASH by Hardebeck and Shearer (2002). The results show that the earthquakes occurred mainly within the oceanic crust and the uppermost mantle. The deepest event was located at a depth of about 60 km. Focal mechanisms of the earthquakes shallower than a depth of 40 km indicate normal-faulting with T-axis normal to the trench. On the other hand, first motion polarities of the events at depths between 50 and 60 km can be explained a reverse faulting. The results suggest that the neutral plane of the stress between shallow extension and deep compression locates at 40 to 50 km deep. Seismic velocity structures indicate velocity decrease in the oceanic mantle toward the trench. Although the velocity decrease varies with locations, the results suggest the bending-related structure change could extend to at least about 15 km below the oceanic Moho in some locations.

Elasto-plastic deformation and plate weakening due to normal faulting in the subducting plate along the Mariana Trench

NASA Astrophysics Data System (ADS)

Zhou, Zhiyuan; Lin, Jian

2018-06-01

We investigated variations in the elasto-plastic deformation of the subducting plate along the Mariana Trench through an analysis of flexural bending and normal fault characteristics together with geodynamic modeling. Most normal faults were initiated at the outer-rise region and grew toward the trench axis with strikes mostly subparallel to the local trench axis. The average trench relief and maximum fault throws were measured to be significantly greater in the southern region (5 km and 320 m, respectively) than the northern and central regions (2 km and 200 m). The subducting plate was modeled as an elasto-plastic slab subjected to tectonic loading at the trench axis. The calculated strain rates and velocities revealed an array of normal fault-like shear zones in the upper plate, resulting in significant faulting-induced reduction in the deviatoric stresses. We then inverted for solutions that best fit the observed flexural bending and normal faulting characteristics, revealing normal fault penetration to depths of 21, 20, and 32 km beneath the seafloor for the northern, central, and southern regions, respectively, which is consistent with the observed depths of the relocated normal faulting earthquakes in the central Mariana Trench. The calculated deeper normal faults of the southern region might lead to about twice as much water being carried into the mantle per unit trench length than the northern and central regions. We further calculated that normal faulting has reduced the effective elastic plate thickness Te by up to 52% locally in the southern region and 33% in both the northern and central regions. The best-fitting solutions revealed a greater apparent angle of the pulling force in the southern region (51-64°) than in the northern (22-35°) and central (20-34°) regions, which correlates with a general southward increase in the seismically-determined dip angle of the subducting slab along the Mariana Trench.

Apparatus and method for rapid cooling of large area substrates in vacuum

DOEpatents

Barth, Kurt L.; Enzenroth, Robert A.; Sampath, Walajabad S.

2012-11-06

The present invention is directed to an apparatus and method for rapid cooling of a large substrate in a vacuum environment. A first cooled plate is brought into close proximity with one surface of a flat substrate. The spatial volume between the first cooling plate and the substrate is sealed and brought to a higher pressure than the surrounding vacuum level to increase the cooling efficiency. A second cooled plate is brought into close proximity with the opposite surface of the flat substrate. A second spatial volume between the second cooling plate and the substrate is sealed and the gas pressure is equalized to the gas pressure in the first spatial volume. The equalization of the gas pressure on both sides of the flat substrate eliminates deflection of the substrate and bending stress in the substrate.

Highly deformable bones: unusual deformation mechanisms of seahorse armor.

PubMed

Porter, Michael M; Novitskaya, Ekaterina; Castro-Ceseña, Ana Bertha; Meyers, Marc A; McKittrick, Joanna

2013-06-01

Multifunctional materials and devices found in nature serve as inspiration for advanced synthetic materials, structures and robotics. Here, we elucidate the architecture and unusual deformation mechanisms of seahorse tails that provide prehension as well as protection against predators. The seahorse tail is composed of subdermal bony plates arranged in articulating ring-like segments that overlap for controlled ventral bending and twisting. The bony plates are highly deformable materials designed to slide past one another and buckle when compressed. This complex plate and segment motion, along with the unique hardness distribution and structural hierarchy of each plate, provide seahorses with joint flexibility while shielding them against impact and crushing. Mimicking seahorse armor may lead to novel bio-inspired technologies, such as flexible armor, fracture-resistant structures or prehensile robotics. Copyright © 2013 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

The Role of Geometrically Necessary Dislocations in Cantilever Beam Bending Experiments of Single Crystals

PubMed Central

Husser, Edgar; Bargmann, Swantje

2017-01-01

The mechanical behavior of single crystalline, micro-sized copper is investigated in the context of cantilever beam bending experiments. Particular focus is on the role of geometrically necessary dislocations (GNDs) during bending-dominated load conditions and their impact on the characteristic bending size effect. Three different sample sizes are considered in this work with main variation in thickness. A gradient extended crystal plasticity model is presented and applied in a three-dimensional finite-element (FE) framework considering slip system-based edge and screw components of the dislocation density vector. The underlying mathematical model contains non-standard evolution equations for GNDs, crystal-specific interaction relations, and higher-order boundary conditions. Moreover, two element formulations are examined and compared with respect to size-independent as well as size-dependent bending behavior. The first formulation is based on a linear interpolation of the displacement and the GND density field together with a full integration scheme whereas the second is based on a mixed interpolation scheme. While the GND density fields are treated equivalently, the displacement field is interpolated quadratically in combination with a reduced integration scheme. Computational results indicate that GND storage in small cantilever beams strongly influences the evolution of statistically stored dislocations (SSDs) and, hence, the distribution of the total dislocation density. As a particular example, the mechanical bending behavior in the case of a physically motivated limitation of GND storage is studied. The resulting impact on the mechanical bending response as well as on the predicted size effect is analyzed. Obtained results are discussed and related to experimental findings from the literature. PMID:28772657

Gaussian step-pressure loading of rigid viscoplastic plates. Ph.D. Thesis

NASA Technical Reports Server (NTRS)

Hayduk, R. J.; Durling, B. J.

1978-01-01

The response of a thin, rigid viscoplastic plate subjected to a spatially axisymmetric Gaussian step pressure impulse loading was studied analytically. A Gaussian pressure distribution in excess of the collapse load was applied to the plate, held constant for a length of time, and then suddenly removed. The plate deforms with monotonically increasing deflections until the dynamic energy is completely dissipated in plastic work. The simply supported plate of uniform thickness obeys the von Mises yield criterion and a generalized constitutive equation for rigid viscoplastic materials. For the small deflection bending response of the plate, the governing system of equations is essentially nonlinear. Transverse shear stress is neglected in the yield condition and rotary inertia in the equations of dynamic equilibrium. A proportional loading technique, known to give excellent approximations of the exact solution for the uniform load case, was used to linearize the problem and to obtain the analytical solutions in the form of eigenvalue expansions. The effects of load concentration, of an order of magnitude change in the viscosity of the plate material, and of load duration were examined while holding the total impulse constant.

Method and apparatus for making an optical element having a dielectric film

NASA Technical Reports Server (NTRS)

Augason, Gordon C. (Inventor)

1987-01-01

A film-application device (FAD) comprising a pair of exterior, tapered, O-ring bearing plate members and a central plate member for simplifying the process of thermally bonding a thin dielectric film to a substrate comprising an optical element are discussed. In use, the film is sandwiched between the O rings and stretched across the optical element by squeezing the exterior plates together before bonding to the element. The film may be used for protecting the optical element or to reduce surface reflection of radiation. The FAD may also be used without the center plate to stretch a dielectric film prior to its attachment to or insertion in a holder to make pellicles or beam-splitters.

A finite element analysis of viscoelastically damped sandwich plates

NASA Astrophysics Data System (ADS)

Ma, B.-A.; He, J.-F.

1992-01-01

A finite element analysis associated with an asymptotic solution method for the harmonic flexural vibration of viscoelastically damped unsymmetrical sandwich plates is given. The element formulation is based on generalization of the discrete Kirchhoff theory (DKT) element formulation. The results obtained with the first order approximation of the asymptotic solution presented here are the same as those obtained by means of the modal strain energy (MSE) method. By taking more terms of the asymptotic solution, with successive calculations and use of the Padé approximants method, accuracy can be improved. The finite element computation has been verified by comparison with an analytical exact solution for rectangular plates with simply supported edges. Results for the same plates with clamped edges are also presented.

Effect of Lumbar Lordosis on the Adjacent Segment in Transforaminal Lumbar Interbody Fusion: A Finite Element Analysis.

PubMed

Zhao, Xin; Du, Lin; Xie, Youzhuan; Zhao, Jie

2018-06-01

We used a finite element (FE) analysis to investigate the biomechanical changes caused by transforaminal lumbar interbody fusion (TLIF) at the L4-L5 level by lumbar lordosis (LL) degree. A lumbar FE model (L1-S5) was constructed based on computed tomography scans of a 30-year-old healthy male volunteer (pelvic incidence,= 50°; LL, 52°). We investigated the influence of LL on the biomechanical behavior of the lumbar spine after TLIF in L4-L5 fusion models with 57°, 52°, 47°, and 40° LL. The LL was defined as the angle between the superior end plate of L1 and the superior end plate of S1. A 150-N vertical axial preload was imposed on the superior surface of L3. A 10-N/m moment was simultaneously applied on the L3 superior surface along the radial direction to simulate the 4 basic physiologic motions of flexion, extension, lateral bending, and torsion in the numeric simulations. The range of motion (ROM) and intradiscal pressure (IDP) of L3-L4 were evaluated and compared in the simulated cases. In all motion patterns, the ROM and IDP were both increased after TLIF. In addition, the decrease in lordosis generally increased the ROM and IDP in all motion patterns. This FE analysis indicated that decreased spinal lordosis may evoke overstress of the adjacent segment and increase the risk of the pathologic development of adjacent segment degeneration; thus, adjacent segment degeneration should be considered when planning a spinal fusion procedure. Copyright © 2018. Published by Elsevier Inc.

Magnetic field of longitudinal gradient bend

NASA Astrophysics Data System (ADS)

Aiba, Masamitsu; Böge, Michael; Ehrlichman, Michael; Streun, Andreas

2018-06-01

The longitudinal gradient bend is an effective method for reducing the natural emittance in light sources. It is, however, not a common element. We have analyzed its magnetic field and derived a set of formulae. Based on the derivation, we discuss how to model the longitudinal gradient bend in accelerator codes that are used for designing electron storage rings. Strengths of multipole components can also be evaluated from the formulae, and we investigate the impact of higher order multipole components in a very low emittance lattice.

Nonlinear vibrations of thin arbitrarily laminated composite plates subjected to harmonic excitations using DKT elements

NASA Astrophysics Data System (ADS)

Chiang, C. K.; Xue, David Y.; Mei, Chuh

1993-04-01

A finite element formulation is presented for determining the large-amplitude free and steady-state forced vibration response of arbitrarily laminated anisotropic composite thin plates using the Discrete Kirchhoff Theory (DKT) triangular elements. The nonlinear stiffness and harmonic force matrices of an arbitrarily laminated composite triangular plate element are developed for nonlinear free and forced vibration analyses. The linearized updated-mode method with nonlinear time function approximation is employed for the solution of the system nonlinear eigenvalue equations. The amplitude-frequency relations for convergence with gridwork refinement, triangular plates, different boundary conditions, lamination angles, number of plies, and uniform versus concentrated loads are presented.

Nonlinear vibrations of thin arbitrarily laminated composite plates subjected to harmonic excitations using DKT elements

NASA Technical Reports Server (NTRS)

Chiang, C. K.; Xue, David Y.; Mei, Chuh

1993-01-01

A finite element formulation is presented for determining the large-amplitude free and steady-state forced vibration response of arbitrarily laminated anisotropic composite thin plates using the Discrete Kirchhoff Theory (DKT) triangular elements. The nonlinear stiffness and harmonic force matrices of an arbitrarily laminated composite triangular plate element are developed for nonlinear free and forced vibration analyses. The linearized updated-mode method with nonlinear time function approximation is employed for the solution of the system nonlinear eigenvalue equations. The amplitude-frequency relations for convergence with gridwork refinement, triangular plates, different boundary conditions, lamination angles, number of plies, and uniform versus concentrated loads are presented.

P PROTEIN IN THE PHLOEM OF CUCURBITA

PubMed Central

Cronshaw, James; Esau, Katherine

1968-01-01

During maturation of sieve elements in Cucurbita maxima Duchesne, the P-protein bodies (slime bodies) usually disperse in the tonoplast-free cell. In some sieve elements the P-protein bodies fail to disperse. The occurrence of dispersal or nondispersal of P-protein bodies can be related to the position of the sieve elements in the stem or petiole. In the sieve elements within the vascular bundle the bodies normally disperse; in the extrafascicular sieve elements the bodies often fail to disperse. Extrafascicular sieve elements showing partial dispersal also occur. The appearance of the sieve plate in fixed material is related to the degree of dispersal or nondispersal of the P-protein bodies. In sieve elements in which complete dispersal occurs the sieve plate usually has a substantial deposit of callose, and the sieve-plate pores are filled with P protein. In sieve elements containing nondispersing P-protein bodies the sieve plate bears little or no callose, and its pores usually are essentially "open." The dispersed P-protein components may aggregate into loosely organized "strands," which sometimes extend vertically through the cell and continue through the sieve-plate pores; but they may be oriented otherwise in the cell, even transversely. PMID:5664205

Experimental investigation on the dynamic response of clamped corrugated sandwich plates subjected to underwater impulsive loadings

NASA Astrophysics Data System (ADS)

Huang, Wei; Zhang, Wei; Li, Dacheng; Hypervelocity Impact Research Center Team

2015-06-01

Corrugated sandwich plates are widely used in marine industry because such plates have high strength-to-weight ratios and blast resistance. The laboratory-scaled fluid-structure interaction experiments are performed to demonstrate the shock resistance of solid monolithic plates and corrugated sandwich plates by quantifying the permanent transverse deflection at mid-span of the plates as a function of impulsive loadings per areal mass. Sandwich structures with 6mm-thick and 10mm-thick 3003 aluminum corrugated core and 5A06 face sheets are compared with the 5A06 solid monolithic plates in this paper. The dynamic deformation of plates are captured with the the 3D digital speckle correlation method (DIC). The results affirm that sandwich structures show a 30% reduction in the maximum plate deflection compare with a monolithic plate of identical mass per unit area, and the peak value of deflection effectively reduced by increasing the thickness core. The failure modes of sandwich plates consists of core crushing, imprinting, stretch tearing of face sheets, bending and permanent deformation of entire structure with the increasing impulsive loads, and the failure mechanisms are analyzed with the postmortem panels and dynamic deflection history captured by cameras. National Natural Science Foundation of China (NO.: 11372088).

Subduction controls the distribution and fragmentation of Earth’s tectonic plates.

PubMed

Mallard, Claire; Coltice, Nicolas; Seton, Maria; Müller, R Dietmar; Tackley, Paul J

2016-07-07

The theory of plate tectonics describes how the surface of Earth is split into an organized jigsaw of seven large plates of similar sizes and a population of smaller plates whose areas follow a fractal distribution. The reconstruction of global tectonics during the past 200 million years suggests that this layout is probably a long-term feature of Earth, but the forces governing it are unknown. Previous studies, primarily based on the statistical properties of plate distributions, were unable to resolve how the size of the plates is determined by the properties of the lithosphere and the underlying mantle convection. Here we demonstrate that the plate layout of Earth is produced by a dynamic feedback between mantle convection and the strength of the lithosphere. Using three-dimensional spherical models of mantle convection that self-consistently produce the plate size–frequency distribution observed for Earth, we show that subduction geometry drives the tectonic fragmentation that generates plates. The spacing between the slabs controls the layout of large plates, and the stresses caused by the bending of trenches break plates into smaller fragments. Our results explain why the fast evolution in small back-arc plates reflects the marked changes in plate motions during times of major reorganizations. Our study opens the way to using convection simulations with plate-like behaviour to unravel how global tectonics and mantle convection are dynamically connected.

Note: Design of transverse electron gun for electron beam based reactive evaporation system.

PubMed

Maiti, Namita; Barve, U D; Bhatia, M S; Das, A K

2011-05-01

In this paper design of a 10 kV, 10 kW transverse electron gun, suitable for reactive evaporation, supported by simulation and modeling, is presented. Simulation of the electron beam trajectory helps in locating the emergence aperture after 90° bend and also in designing the crucible on which the beam is finally incident after 270° bend. The dimension of emergence aperture plays a vital role in designing the differential pumping system between the gun chamber and the substrate chamber. Experimental validation is done for beam trajectory by piercing a stainless steel plate at 90° position which is kept above the crucible.

Bend-Twist Coupled Carbon-Fiber Laminate Beams: Fundamental Behavior and Applications

NASA Astrophysics Data System (ADS)

Babuska, Pavel

Material-induced bend-twist coupling in laminated composite beams has seen applications in engineered structures for decades, ranging from airplane wings to turbine blades. Symmetric, unbalanced, carbon fiber laminates which exhibit bend-twist coupling can be difficult to characterize and exhibit unintuitive deformation states which may pose challenges to the engineer. In this thesis, bend-twist coupled beams are investigated comprehensively, by experimentation, numerical modeling, and analytical methods. Beams of varying fiber angle and amount of coupling were manufactured and physically tested in both linear and nonlinear static and dynamic settings. Analytical mass and stiffness matrices were derived for the development of a beam element to use in the stiffness matrix analysis method. Additionally, an ABAQUS finite element model was used in conjunction with the analytical methods to predict and further characterize the behavior of the beams. The three regimes, experimental, analytical, and numerical, represent a full-field characterization of bend-twist coupling in composite beams. A notable application of bend-twist coupled composites is for passively adaptive turbine blades whereby the deformation coupling can be built into the blade structure to simultaneously bend and twist, thus pitching the blade into or away from the fluid flow, changing the blade angle of attack. Passive pitch adaptation has been implemented successfully in wind turbine blades, however, for marine turbine blades, the technology is still in the development phase. Bend-twist coupling has been shown numerically to be beneficial to the tidal turbine performance, however little validation has been conducted in the experimental regime. In this thesis, passively adaptive experiment scale tidal turbine blades were designed, analyzed, manufactured, and physically tested, validating the foundational numerical work. It was shown that blade forces and root moments as well as turbine thrust and power coefficients can be manipulated by inclusion of passive pitch adaption by bend-twist coupling.

Design and analysis for a bend-resistant and large-mode-area photonic crystal fiber with hybrid cladding.

PubMed

Qin, Yan; Yang, Huajun; Jiang, Ping; Gui, Fengji; Caiyang, Weinan; Cao, Biao

2018-05-10

In this paper, an asymmetric large-mode-area photonic crystal fiber (LMA-PCF) with low bending loss at a smaller bending radius is designed. The finite-element method with a perfectly matched layer boundary is used to analyze the performance of the PCF. To achieve LMA-PCF with low bending loss, the air holes with double lattice constants and different sizes at the core are designed. Numerical results show that this structure can achieve low bending loss and LMA with a smaller bending radius at the wavelength of 1.55 μm. The effective mode area of the fundamental mode is larger than 1000  μm 2 when the bending radius is ≥10  cm. The bending loss of the fundamental mode is just 0.0113 dB/m, and the difference between the fundamental and high-order modes of the bending loss is larger than 10 3 when the bending radius is 10 cm. Simulation results show this novel PCF can achieve LMA and have effective single-mode operation when the bending orientation angle ranges in ±110°. This novel photonic crystal has potential application in high-power fiber lasers.

Transonic shock-induced dynamics of a flexible wing with a thick circular-arc airfoil

NASA Technical Reports Server (NTRS)

Bennett, Robert M.; Dansberry, Bryan E.; Farmer, Moses G.; Eckstrom, Clinton V.; Seidel, David A.; Rivera, Jose A., Jr.

1991-01-01

Transonic shock boundary layer oscillations occur on rigid models over a small range of Mach numbers on thick circular-arc airfoils. Extensive tests and analyses of this phenomena have been made in the past but essentially all of them were for rigid models. A simple flexible wing model with an 18 pct. circular arc airfoil was constructed and tested in the Langley Transonic Dynamics Tunnel to study the dynamic characteristics that a wing might have under these circumstances. In the region of shock boundary layer oscillations, buffeting of the first bending mode was obtained. This mode was well separated in frequency from the shock boundary layer oscillations. A limit cycle oscillation was also measured in a third bending like mode, involving wind vertical bending and splitter plate motion, which was in the frequency range of the shock boundary layer oscillations. Several model configurations were tested, and a few potential fixes were investigated.

Failure of the lumbar pedicles under bending loading - biomed 2010.

PubMed

Arregui-Dalmases, Carlos; Ash, Joseph H; Del Pozo, Eduardo; Kerrigan, Jason R; Crandall, Jeff

2010-01-01

The purpose of this study was to investigate the magnitude of bending moment that results in fracture of the pedicles when lumbar vertebrae are loaded in four-point bending. Nine human second lumbar vertebrae (L2) were harvested from donors aged 59-75 years. The specimens were potted and then subjected to quasi-static sagittal-plane four-point bending, which allowed for a constant bending moment applied over a 3.8 cm span centered on the vertebral pedicles until fracture. The failure bending moment calculated for the pedicles varied widely (30.7 +/- 12.3 Nm) and was poorly correlated with subject age (y = -0.91x + 91.5, R(2) = -0.27). With increasing displacement, the bending moment applied to the pedicles increased, first linearly, followed by a non-linear portion, prior to specimen fracture. In general, the specimens failed at the interface of the pedicles and vertebral bodies, but failures were observed elsewhere as well. These data provide sufficient response and boundary condition information for finite element modeling and model validation.

Theoretical solution for light transmission of a bended hollow light guide

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kocifaj, Miroslav; Darula, Stanislav; Kittler, Richard

2010-08-15

Hollow light guides with very high reflective inner surfaces are novel daylight systems that collect sunlight and skylight available on the roof of buildings transporting it into deep or windowless interiors in building cores. Thus the better utilization of daylight can result in energy savings and wellbeing in these enclosed indoor spaces. An analytical complex solution of a straight tube system was solved in the HOLIGILM method with a user-friendly tool available on the http://www.holigilm.info. An even more difficult light flow transport is to be determined in bended tubes usually placed on sloped roofs where a bend is necessary tomore » adjust the vertical pass through the ceilings. This paper presents the theoretical derivation of the model with its graphical representation and coordinate system respecting backward ray-tracing bend distortions. To imagine the resulting illuminance on the horizontal plane element in the interior, the virtual ray (i.e. luminance in an elementary solid angle) has to pass the ceiling diffuser interface, the inner mirror like tube with a bend, through a roof cupola attachment to the element of the sky and sun light source. Due to this complexity and the lengthy derivation and explanations more practical applications will be published later in a separate contribution. (author)« less

Mechanical decoupling along a subduction boundary fault: the case of the Tindari-Alfeo Fault System, Calabrian Arc (central Mediterranean Sea)

NASA Astrophysics Data System (ADS)

Maesano, F. E.; Tiberti, M. M.; Basili, R.

2017-12-01

In recent years an increasing number of studies have been focused in understanding the lateral terminations of subduction zones. In the Mediterranean region, this topic is of particular interest for the presence of a "land-locked" system of subduction zones interrupted by continental collision and back-arc opening. We present a 3D reconstruction of the area surrounding the Tindari-Alfeo Fault System (TAFS) based on a dense set of deep seismic reflection profiles. This fault system represents a major NNW-SSE trending subduction-transform edge propagator (STEP) that controls the deformation zone bounding the Calabrian subduction zone (central Mediterranean Sea) to the southwest. This 3D model allowed us to characterize the mechanical and kinematic evolution of the TAFS during the Plio-Quaternary. Our study highlights the presence of a mechanical decoupling between the deformation observed in the lower plate, constituted by the Ionian oceanic crust entering the subduction zone, and the upper plate, where a thick accretionary wedge has formed. The lower plate hosts the master faults of the TAFS, whereas the upper plate is affected by secondary deformation (bending-moment faulting, localized subsidence, stepovers, and restraining/releasing bends). The analysis of the syn-tectonic sedimentary basins related to the activity of the TAFS at depth allow us to constrain the propagation rate of the deformation and of the vertical component of the slip-rate. Our findings provide a comprehensive framework of the structural setting that can be expected along a STEP boundary where contractional and transtensional features coexist at close distance from one another.

Star-Shaped Crack Pattern of Broken Windows

NASA Astrophysics Data System (ADS)

Vandenberghe, Nicolas; Vermorel, Romain; Villermaux, Emmanuel

2013-04-01

Broken thin brittle plates like windows and windshields are ubiquitous in our environment. When impacted locally, they typically present a pattern of cracks extending radially outward from the impact point. We study the variation of the pattern of cracks by performing controlled transverse impacts on brittle plates over a broad range of impact speed, plate thickness, and material properties, and we establish from experiments a global scaling law for the number of radial cracks incorporating all these parameters. A model based on Griffith’s theory of fracture combining bending elastic energy and fracture energy accounts for our observations. These findings indicate how the postmortem shape of broken samples are related to material properties and impact parameters, a procedure relevant to forensic science, archaeology, or astrophysics.