First-principles investigations on structural, elastic, electronic properties and Debye temperature of orthorhombic Ni3Ta under pressure

NASA Astrophysics Data System (ADS)

Li, Pan; Zhang, Jianxin; Ma, Shiyu; Jin, Huixin; Zhang, Youjian; Zhang, Wenyang

2018-06-01

The structural, elastic, electronic properties and Debye temperature of Ni3Ta under different pressures are investigated using the first-principles method based on density functional theory. Our calculated equilibrium lattice parameters at 0 GPa well agree with the experimental and previous theoretical results. The calculated negative formation enthalpies and elastic constants both indicate that Ni3Ta is stable under different pressures. The bulk modulus B, shear modulus G, Young's modulus E and Poisson's ratio ν are calculated by the Voigt-Reuss-Hill method. The bigger ratio of B/G indicates Ni3Ta is ductile and the pressure can improve the ductility of Ni3Ta. In addition, the results of density of states and the charge density difference show that the stability of Ni3Ta is improved by the increasing pressure. The Debye temperature ΘD calculated from elastic modulus increases along with the pressure.

Investigation of structural, electronic, elastic and optical properties of Cd1-x-yZnxHgyTe alloys

NASA Astrophysics Data System (ADS)

Tamer, M.

2016-06-01

Structural, optical and electronic properties and elastic constants of Cd1-x-yZnx HgyTe alloys have been studied by employing the commercial code Castep based on density functional theory. The generalized gradient approximation and local density approximation were utilized as exchange correlation. Using elastic constants for compounds, bulk modulus, band gap, Fermi energy and Kramers-Kronig relations, dielectric constants and the refractive index have been found through calculations. Apart from these, X-ray measurements revealed elastic constants and Vegard's law. It is seen that results obtained from theory and experiments are all in agreement.

Simulation of hydrocephalus condition in infant head

NASA Astrophysics Data System (ADS)

Wijayanti, Erna; Arif, Idam

2014-03-01

Hydrocephalus is a condition of an excessive of cerebrospinal fluid in brain. In this paper, we try to simulate the behavior of hydrocephalus conditions in infant head by using a hydro-elastic model which is combined with orthotropic elastic skull and with the addition of suture that divide the skull into two lobes. The model then gives predictions for the case of stenosis aqueduct by varying the cerebral aqueduct diameter, time constant and brain elastic modulus. The hydrocephalus condition which is shown by the significant value of ventricle displacement, as the result shows, is occurred when the aqueduct is as resistant as brain parenchyma for the flow of cerebrospinal fluid. The decrement of brain elastic modulus causes brain parenchyma displacement value approach ventricle displacement value. The smaller of time constant value causes the smaller value of ventricle displacement.

Effects of biaxial strains on electronic and elastic properties of hexagonal XSi2 (X = Cr, Mo, W) from first-principles

NASA Astrophysics Data System (ADS)

Zhu, Haiyan; Shi, Liwei; Li, Shuaiqi; Zhang, Shaobo; Xia, Wangsuo

2018-02-01

Structural, electronic properties and elastic anisotropy of hexagonal C40 XSi2 (X = Cr, Mo, W) under equibiaxial in-plane strains are systematically studied using first-principle calculations. The energy gaps show significant changes with biaxial strains, whereas they are always indirect band-gap materials for -6% <ɛxx < 6%. All elastic constants, bulk modulus, shear modulus, Young's modulus increase (decrease) almost linearly with increasing compressive (tensile) strains. The evolutions of BH /GH ratio and Poisson's ratio indicate that these compounds have a better (worse) ductile behaviour under compressive (tensile) strains. A set of 3D plots show a larger directional variability in the Young's modulus E and shear modulus G at different strains for the three compounds, which is consist with the values of anisotropy factors. Moreover, the evolution of Debye temperature and anisotropy of sound velocities with biaxial strains are discussed.

Equilibrium structures of carbon diamond-like clusters and their elastic properties

NASA Astrophysics Data System (ADS)

Lisovenko, D. S.; Baimova, Yu. A.; Rysaeva, L. Kh.; Gorodtsov, V. A.; Dmitriev, S. V.

2017-04-01

Three-dimensional carbon diamond-like phases consisting of sp 3-hybridized atoms, obtained by linking of carcasses of fullerene-like molecules, are studied by methods of molecular dynamics modeling. For eight cubic and one hexagonal diamond-like phases on the basis of four types of fullerene-like molecules, equilibrium configurations are found and the elastic constants are calculated. The results obtained by the method of molecular dynamics are used for analytical calculations of the elastic characteristics of the diamond- like phases with the cubic and hexagonal anisotropy. It is found that, for a certain choice of the dilatation axis, three of these phases have negative Poisson's ratio, i.e., are partial auxetics. The variability of the engineering elasticity coefficients (Young's modulus, Poisson's ratio, shear modulus, and bulk modulus) is analyzed.

The effective propagation constants of SH wave in composites reinforced by dispersive parallel nanofibers

NASA Astrophysics Data System (ADS)

Qiang, FangWei; Wei, PeiJun; Li, Li

2012-07-01

In the present paper, the effective propagation constants of elastic SH waves in composites with randomly distributed parallel cylindrical nanofibers are studied. The surface stress effects are considered based on the surface elasticity theory and non-classical interfacial conditions between the nanofiber and the host are derived. The scattering waves from individual nanofibers embedded in an infinite elastic host are obtained by the plane wave expansion method. The scattering waves from all fibers are summed up to obtain the multiple scattering waves. The interactions among random dispersive nanofibers are taken into account by the effective field approximation. The effective propagation constants are obtained by the configurational average of the multiple scattering waves. The effective speed and attenuation of the averaged wave and the associated dynamical effective shear modulus of composites are numerically calculated. Based on the numerical results, the size effects of the nanofibers on the effective propagation constants and the effective modulus are discussed.

Structural and elastic properties of AIBIIIC 2 VI semiconductors

NASA Astrophysics Data System (ADS)

Kumar, V.; Singh, Bhanu P.

2018-01-01

The plane wave pseudo-potential method within density functional theory has been used to calculate the structural and elastic properties of AIBIIIC 2 VI semiconductors. The electronic band structure, density of states, lattice constants (a and c), internal parameter (u), tetragonal distortion (η), energy gap (Eg), and bond lengths of the A-C (dAC) and B-C (dBC) bonds in AIBIIIC 2 VI semiconductors have been calculated. The values of elastic constants (Cij), bulk modulus (B), shear modulus (G), Young's modulus (Y), Poisson's ratio (υ), Zener anisotropy factor (A), Debye temperature (ϴD) and G/B ratio have also been calculated. The values of all 15 parameters of CuTlS2 and CuTlSe2 compounds, and 8 parameters of 20 compounds of AIBIIIC 2 VI family, except AgInS2 and AgInSe2, have been calculated for the first time. Reasonably good agreement has been obtained between the calculated, reported and available experimental values.

Elasticity of Pargasite Amphibole: A Hydrous Phase at Mid Lithospheric Discontinuity

NASA Astrophysics Data System (ADS)

Peng, Y.; Mookherjee, M.

2017-12-01

Mid Lithospheric Discontinuity (MLD) is characterized by a low shear wave velocity ( 3 to 10 %). In cratons, the depth of MLD varies between 80 and 100 km. The reduction of the shear wave velocity at MLD is similar to what is observed in the lithosphere-asthenosphere boundary (LAB). Such low velocity at MLD could be caused by partial melting, temperature induced grain boundary sliding, changes in the elastic anisotropy, and/or metasomatism which may lead to the formation of hydrous phases including mica and amphibole. Thus, it is clear that in order to assess the role of metasomatism at MLD, we need better constraints on the elasticity of hydrous phases. However, such elasticity data are scarce. In this study, we explore elasticity of pargasite amphibole [NaCa2(Mg4Al)(Si6Al2)O22(OH)2] using density functional theory (DFT) with local density approximation (LDA) and generalized gradient approximation (GGA). We find that the pressure-volume results can be adequately described by a finite strain equation with the bulk modulus, K0 being 102 and 85 GPa for LDA and GGA respectively. We also determined the full elastic constant tensor (Cij) using the finite difference method. The bulk modulus, K0 determined from the full elastic constant tensor is 104 GPa for LDA and 87 GPa for GGA. The shear modulus, G0 determined from the full elastic constant tensor is 64 GPa for LDA and 58 GPa for GGA. The bulk and shear moduli predicted with LDA are 5 and 1 % stiffer than the recent results [1]. In contrast, the bulk and shear moduli predicted with GGA are 12 and 10 % softer compared to the recent results [1]. The full elastic constant tensor for pargasite shows significant anisotropy. For instance, LDA predicts compressional (AVP) and shear (AVS) wave anisotropy of 22 and 20 % respectively. At higher pressure, elastic moduli stiffen. However, temperature is likely to have an opposite effect on the elasticity and this remains largely unknown for pargasite. Compared to the major mantle minerals, pargasite has softer elastic constants and significant anisotropy and may explain the reduction in shear wave velocity at MLD. Reference: [1] Brown, J. M., Abramson, E. H.,2016, Phys. Earth Planet. Int., 261, 161-171. Acknowledgement: This work is supported by US NSF award EAR 1639552.

Mechanical and Thermal Properties of Praseodymium Monopnictides: AN Ultrasonic Study

NASA Astrophysics Data System (ADS)

Bhalla, Vyoma; Kumar, Raj; Tripathy, Chinmayee; Singh, Devraj

2013-09-01

We have computed ultrasonic attenuation, acoustic coupling constants and ultrasonic velocities of praseodymium monopnictides PrX(X: N, P, As, Sb and Bi) along the <100>, <110>, <111> in the temperature range 100-500 K using higher order elastic constants. The higher order elastic constants are evaluated using Coulomb and Born-Mayer potential with two basic parameters viz. nearest-neighbor distance and hardness parameter in the temperature range of 0-500 K. Several other mechanical and thermal parameters like bulk modulus, shear modulus, Young's modulus, Poisson ratio, anisotropic ratio, tetragonal moduli, Breazeale's nonlinearity parameter and Debye temperature are also calculated. In the present study, the fracture/toughness (B/G) ratio is less than 1.75 which implies that PrX compounds are brittle in nature at room temperature. The chosen material fulfilled Born criterion of mechanical stability. We also found the deviation of Cauchy's relation at higher temperatures. PrN is most stable material as it has highest valued higher order elastic constants as well as the ultrasonic velocity. Further, the lattice thermal conductivity using modified approach of Slack and Berman is determined at room temperature. The ultrasonic attenuation due to phonon-phonon interaction and thermoelastic relaxation mechanisms have been computed using modified Mason's approach. The results with other well-known physical properties are useful for industrial applications.

Elastic and thermal properties of the layered thermoelectrics BiOCuSe and LaOCuSe

NASA Astrophysics Data System (ADS)

Saha, S. K.; Dutta, G.

2016-09-01

We determine the elastic properties of the layered thermoelectrics BiOCuSe and LaOCuSe using first-principles density functional theory calculations. To predict their stability, we calculate six distinct elastic constants, where all of them are positive, and suggest mechanically stable tetragonal crystals. As elastic properties relate to the nature and the strength of the chemical bond, the latter is analyzed by means of real-space descriptors, such as the electron localization function (ELF) and Bader charge. From elastic constants, a set of related properties, namely, bulk modulus, shear modulus, Young's modulus, sound velocity, Debye temperature, Grüneisen parameter, and thermal conductivity, are evaluated. Both materials are found to be ductile in nature and not brittle. We find BiOCuSe to have a smaller sound velocity and, hence, within the accuracy of the used Slack's model, a smaller thermal conductivity than LaOCuSe. Our calculations also reveal that the elastic properties and the related lattice thermal transport of both materials exhibit a much larger anisotropy than their electronic band properties that are known to be moderately anisotropic because of a moderate effective-electron-mass anisotropy. Finally, we determine the lattice dynamical properties, such as phonon dispersion, atomic displacement, and mode Grüneisen parameters, in order to correlate the elastic response, chemical bonding, and lattice dynamics.

Investigation of structural, electronic, elastic and optical properties of Cd{sub 1-x-y}Zn{sub x}Hg{sub y}Te alloys

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

Tamer, M., E-mail: mehmet.tamer@zirve.edu.tr

2016-06-15

Structural, optical and electronic properties and elastic constants of Cd1{sub -x-y}Zn{sub x} Hg{sub y}Te alloys have been studied by employing the commercial code Castep based on density functional theory. The generalized gradient approximation and local density approximation were utilized as exchange correlation. Using elastic constants for compounds, bulk modulus, band gap, Fermi energy and Kramers–Kronig relations, dielectric constants and the refractive index have been found through calculations. Apart from these, X-ray measurements revealed elastic constants and Vegard’s law. It is seen that results obtained from theory and experiments are all in agreement.

First-principles investigations on structural, elastic and mechanical properties of BNxAs1‑x ternary alloys

NASA Astrophysics Data System (ADS)

Zhang, Junqin; Ma, Huihui; Zhao, Bin; Wei, Qun; Yang, Yintang

2018-05-01

A systematic investigation of the structural optimization, elastic and mechanical properties of the BNxAs1‑x ternary alloys are reported in the present work using the density-functional theory with the generalized gradient approximation (GGA) of the exchange-correlation functional. Some of the constants which are used to analyze the properties including elastic constants and modulus, and some parameters describing the elastic anisotropy and Debye temperature are also calculated. Our calculations were performed to evaluate the equilibrium lattice constant and band structure compared with the available theoretical works. On the one hand, our results might be expected to provide a theoretical basis for future study of BNxAs1‑x alloys towards elastic or mechanical properties. On the other hand, we draw a conclusion that BNxAs1‑x alloys show direct bandgap when x equals 0.25, 0.5 or 0.75. We obtained the elastic modulus, Poisson’s ratio and universal anisotropic index which are used to demonstrate the elastic anisotropy of these alloys which is proved according to our calculations. Also, we calculated the Debye temperature to illustrate covalent interactions and obtained the lower limit of the thermal conductivity for further research.

Density and mechanical properties of calcium aluminate cement

NASA Astrophysics Data System (ADS)

Ahmed, Syed Taqi Uddin; Ahmmad, Shaik Kareem

2018-04-01

Calcium aluminate cements are a special type of cements which have their composition mainly dominated by the presence of Monocalcium Aluminates. In the present paper for the first time we have shown theoretical density and elastic constants for various calcium aluminate cements. The density of the present CAS decrease with aluminates presents in the cement. Using the density data, the elastic moduli namely Young's modulus, bulk and shear modulus show strong linear dependence as a function of compositional parameter.

First-principles calculations for elastic properties of OsB 2 under pressure

NASA Astrophysics Data System (ADS)

Yang, Jun-Wei; Chen, Xiang-Rong; Luo, Fen; Ji, Guang-Fu

2009-11-01

The structure, elastic properties and elastic anisotropy of orthorhombic OsB 2 are investigated by density functional theory method with the ultrasoft pseudopotential scheme in the frame of the generalized gradient approximation (GGA) as well as local density approximation (LDA). The obtained structural parameters, elastic constants, elastic anisotropy and Debye temperature for OsB 2 under pressure are consistent with the available experimental data and other theoretical results. It is found that the elastic constants, bulk modulus and Debye temperature of OsB 2 tend to increase with increasing pressure. It is predicted that OsB 2 is not a superhard material from our calculations.

Elastic-mathematical theory of cells and mitochondria in swelling process. II. Effect of temperature upon modulus of elasticity of membranous material of egg cells of sea urchin, Strongylocentrotus purpuratus, and of oyster, Crassostrea virginica.

PubMed

Mela, M J

1968-01-01

The elastic behavior of the cell wall as a function of the temperature has been studied with particular attention being given to the swelling of egg cells of Strongylocentrotus purpuratus and Crassostrea virginica in different sea water concentrations at different temperatures. It was found that the modulus of elasticity is a nonlinear function of temperature. At about 12-13 degrees C the modulus of elasticity (E) is constant, independent of the stress (sigma) and strain (epsilon(nu)) which exist at the cell wall; the membranous material follows Hooke's law, and E approximately 3 x 10(7) dyn/cm(2) for S. purpuratus and C. virginica. When the temperature is higher or lower than 12-13 degrees C, the modulus of elasticity increases, and the membranous material does not follow Hooke's law, but is almost directly proportional to the stresses existing at the cell wall. On increasing the stress, the function E(sigma) = E(sigma) approaches saturation. The corresponding stress-strain diagrams, sigma = sigma(epsilon(nu)), and the graphs, E(sigma) = E(sigma) and E(sigma) = E(t) are given. The cyto-elastic phenomena at the membrane are discussed.

Elastic properties and fracture strength of quasi-isotropic graphite/epoxy composites

NASA Technical Reports Server (NTRS)

Sullivan, T. L.

1977-01-01

A research program is described which was devised to determine experimentally the elastic properties in tension and bending of quasi-isotropic laminates made from high-modulus graphite fiber and epoxy. Four laminate configurations were investigated, and determinations were made of the tensile modulus, Poisson's ratio, bending stiffness, fracture strength, and fracture strain. The measured properties are compared with those predicted by laminate theory, reasons for scatter in the experimental data are discussed, and the effect of fiber misalignment on predicted elastic tensile properties is examined. The results strongly suggest that fiber misalignment in combination with variation in fiber volume content is responsible for the scatter in both elastic constants and fracture strength.

Ab Initio Study of Electronic Structure, Elastic and Transport Properties of Fluoroperovskite LiBeF3

NASA Astrophysics Data System (ADS)

Benmhidi, H.; Rached, H.; Rached, D.; Benkabou, M.

2017-04-01

The aim of this work is to investigate the electronic, mechanical, and transport properties of the fluoroperovskite compound LiBeF3 by first-principles calculations using the full-potential linear muffin-tin orbital method based on density functional theory within the local density approximation. The independent elastic constants and related mechanical properties including the bulk modulus ( B), shear modulus ( G), Young's modulus ( E), and Poisson's ratio ( ν) have been studied, yielding the elastic moduli, shear wave velocities, and Debye temperature. According to the electronic properties, this compound is an indirect-bandgap material, in good agreement with available theoretical data. The electron effective mass, hole effective mass, and energy bandgaps with their volume and pressure dependence are investigated for the first time.

Elastic response of binary hard-sphere fluids

NASA Astrophysics Data System (ADS)

Rickman, J. M.; Ou-Yang, H. Daniel

2011-07-01

We derive expressions for the high-frequency, wave-number-dependent elastic constants of a binary hard-sphere fluid and employ Monte Carlo computer simulation to evaluate these constants in order to highlight the impact of composition and relative sphere diameter on the elastic response of this system. It is found that the elastic constant c11(k) exhibits oscillatory behavior as a function of k whereas the high-frequency shear modulus, for example, does not. This behavior is shown to be dictated by the angular dependence (in k⃗ space) of derivatives of the interatomic force at contact. The results are related to recent measurements of the compressibility of colloidal fluids in laser trapping experiments.

Effective Elastic Modulus as a Function of Angular Leaf Span for Curved Leaves of Pyrolytic Boron Nitride

NASA Technical Reports Server (NTRS)

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

1999-01-01

A theoretical equation was derived to predict the spring constant (load/deflection) for a simply supported cylindrical section with a line force applied at the center. Curved leaves of PBN were mechanically deformed and the force versus deflection data was recorded and compared to the derived theoretical equation to yield an effective modulus for each leaf. The effective modulus was found to vary from the pure shear modulus for a flat plate to a mixed mode for a half cylinder as a function of the sine of one half the angular leaf span. The spring constants of individual PBN leaves were usually predicted to within 30%.

Elastic-Mathematical Theory of Cells and Mitochondria in Swelling Process

PubMed Central

Mela, M. J.

1968-01-01

The elastic behavior of the cell wall as a function of the temperature has been studied with particular attention being given to the swelling of egg cells of Strongylocentrotus purpuratus and Crassostrea virginica in different sea water concentrations at different temperatures. It was found that the modulus of elasticity is a nonlinear function of temperature. At about 12-13°C the modulus of elasticity (E) is constant, independent of the stress (σ) and strain (εν) which exist at the cell wall; the membranous material follows Hooke's law, and E ≈ 3 × 107 dyn/cm2 for S. purpuratus and C. virginica. When the temperature is higher or lower than 12-13°C, the modulus of elasticity increases, and the membranous material does not follow Hooke's law, but is almost directly proportional to the stresses existing at the cell wall. On increasing the stress, the function Eσ = E(σ) approaches saturation. The corresponding stress-strain diagrams, σ = σ(εν), and the graphs, Eσ = E(σ) and Eσ = E(t) are given. The cyto-elastic phenomena at the membrane are discussed. PMID:5689191

Structural stability, elastic and thermodynamic properties of Au-Cu alloys from first-principles calculations

NASA Astrophysics Data System (ADS)

Kong, Ge-Xing; Ma, Xiao-Juan; Liu, Qi-Jun; Li, Yong; Liu, Zheng-Tang

2018-03-01

Using first-principles calculations method based on density functional theory (DFT) with the Perdew-Burke-Ernzerhof (PBE) implementation of the generalized gradient approximation (GGA), we investigate the structural, elastic and thermodynamic properties of gold-copper intermetallic compounds (Au-Cu ICs). The calculated lattice parameters are in excellent agreement with experimental data. The elastic constants show that all the investigated Au-Cu alloys are mechanically stable. Elastic properties, including the shear modulus, Young's modulus, Poisson's ratio and Pugh's indicator, of the intermetallic compounds are evaluated and discussed, with special attention to the remarkable anisotropy displayed by Au-Cu ICs. Thermodynamic and transport properties including the Debye temperature, thermal conductivity and melting point are predicted from the averaged sound velocity and elastic moduli, using semi-empirical formulas.

Tensile elastic properties of 18:8 chromium-nickel steel as affected by plastic deformation

NASA Technical Reports Server (NTRS)

Mcadam, D J; Mebs, R W

1939-01-01

The relationship between stress and strain, and between stress and permanent set, for 18:8 alloy as affected by prior plastic deformation is discussed. Hysteresis and creep and their effects on the stress-strain and stress-set curves are also considered, as well as the influence of duration of the rest interval after cold work and the influence of plastic deformation on proof stresses, on the modulus of elasticity at zero stress, and on the curvature of the stress-strain line. A constant (c sub 1) is suggested to represent the variation of the modulus of elasticity with stress.

Elasticity study of textured barium strontium titanate thin films by X-ray diffraction and laser acoustic waves

NASA Astrophysics Data System (ADS)

Chaabani, Anouar; Njeh, Anouar; Donner, Wolfgang; Klein, Andreas; Hédi Ben Ghozlen, Mohamed

2017-05-01

Ba0.65Sr0.35TiO3 (BST) thin films of 300 nm were deposited on Pt(111)/TiO2/SiO2/Si(001) substrates by radio frequency magnetron sputtering. Two thin films with different (111) and (001) fiber textures were prepared. X-ray diffraction was applied to measure texture. The raw pole figure data were further processed using the MTEX quantitative texture analysis software for plotting pole figures and calculating elastic constants and Young’s modulus from the orientation distribution function (ODF) for each type of textured fiber. The calculated elastic constants were used in the theoretical studies of surface acoustics waves (SAW) propagating in two types of multilayered BST systems. Theoretical dispersion curves were plotted by the application of the ordinary differential equation (ODE) and the stiffness matrix methods (SMM). A laser acoustic waves (LAW) technique was applied to generate surface acoustic waves (SAW) propagating in the BST films, and from a recursive process, the effective Young’s modulus are determined for the two samples. These methods are used to extract and compare elastic properties of two types of BST films, and quantify the influence of texture on the direction-dependent Young’s modulus.

The Effect of Annealing on the Elastic Modulus of Orthodontic Wires

NASA Astrophysics Data System (ADS)

Higginbottom, Kyle

Introduction: Nickel Titanium orthodontic wires are currently used in orthodontic treatment due to their heat activated properties and their delivery of constant force. The objective of this study was to determine the effect of annealing on the elastic modulus of Nickel Titanium, Stainless Steel and Beta-titanium (TMA) wires. Different points along the wire were tested in order to determine how far from the annealed ends the elastic modulus of the wires was affected. Methods: Eighty (80) orthodontic wires consisting of 4 equal groups (SS/TMA/Classic NitinolRTM/Super Elastic NitinolRTM) were used as the specimens for this study. All wires were measured and marked at 5mm measurements, and cut into 33.00mm sections. The wires were heated with a butane torch until the first 13.00mm of the wires were red hot. Load deflection tests using an InstronRTM universal testing machine were run at 5mm distances from the end of the wire that had been annealed. The change in elastic modulus was then determined. Results: There was a significant difference (F = 533.001, p = 0.0005) in the change in elastic modulus for the four distances. There was also a significant difference (F = 57.571, p = 0.0005) in the change in elastic modulus for the four wire types. There was a significant interaction (F = 19.601, p = 0.005) between wire type and distance, however this interaction negated the differences between the wires. Conclusion: 1) There are significant differences in the changes in elastic modulus between the areas of the wires within the annealed section and those areas 5mm and 10mm away from the annealed section. The change in elastic modulus within the annealed section was significantly greater at 8 mm than it was at 13mm, and this was significantly greater than 18mm and 23mm (5mm and 10mm beyond the annealed section). However, there was no statistical difference in the change in elastic modulus between 5mm and 10mm away from the annealed section (18mm and 23mm respectively). 2) Regardless of the wire type, no clinically important effects were seen 5mm and 10mm beyond the annealed portion.

Adiabatic bulk modulus of elasticity for 2D liquid dusty plasmas

NASA Astrophysics Data System (ADS)

Feng, Yan; Huang, Dong; Li, Wei

2018-05-01

From the recently obtained equation of state (EOS) for two-dimensional (2D) liquid dusty plasmas, their various physical quantities have been derived analytically, such as the specific heat CV, the Grüneisen parameter, the bulk modulus of elasticity, and the isothermal compressibility. Here, the coefficient of volumetric thermal expansion αV and the relative pressure coefficient αP of 2D liquid dusty plasmas are derived from their EOS. Using the obtained CV, αV, and αP, the analytical expression of their heat capacity under constant-pressure conditions CP is obtained. Thus, the heat capacity ratio, expressed as CP/CV , is analytically achieved. Then the adiabatic bulk modulus of elasticity is derived, so that the adiabatic sound speeds are obtained. These obtained results are compared with previous findings using a different approach.

Structural, electronic, elastic, and thermodynamic properties of CaSi, Ca2Si, and CaSi2 phases from first-principles calculations

NASA Astrophysics Data System (ADS)

Li, X. D.; Li, K.; Wei, C. H.; Han, W. D.; Zhou, N. G.

2018-06-01

The structural, electronic, elastic, and thermodynamic properties of CaSi, Ca2Si, and CaSi2 are systematically investigated by using first-principles calculations method based on density functional theory (DFT). The calculated formation enthalpies and cohesive energies show that CaSi2 possesses the greatest structural stability and CaSi has the strongest alloying ability. The structural stability of the three phases is compared according to electronic structures. Further analysis on electronic structures indicates that the bonding of these phases exhibits the combinations of metallic, covalent, and ionic bonds. The elastic constants are calculated, and the bulk modulus, shear modulus, Young's modulus, Poisson's ratio, and anisotropy factor of polycrystalline materials are deduced. Additionally, the thermodynamic properties were theoretically predicted and discussed.

Measurement of leaky Lamb wave dispersion curves with application on coating characterization

NASA Astrophysics Data System (ADS)

Lee, Yung-Chun; Cheng, Sheng Wen

2001-04-01

This paper describes a new measurement system for measuring dispersion curves of leaky Lamb waves. The measurement system is based on a focusing PVDF transducer, the defocusing measurement, the V(f,z) waveform processing method, and an image displaying technique. The measurement system is applied for the determination of thin-film elastic properties, namely Young's modulus and shear modulus, by the inversion of dispersion curves measured from a thin-film/plate configuration. Elastic constants of electro-deposited nickel layers are determined with this method.

The Pressure Dependence of Structural, Electronic, Mechanical, Vibrational, and Thermodynamic Properties of Palladium-Based Heusler Alloys

NASA Astrophysics Data System (ADS)

Çoban, Cansu

2017-08-01

The pressure dependent behaviour of the structural, electronic, mechanical, vibrational, and thermodynamic properties of Pd2TiX (X=Ga, In) Heusler alloys was investigated by ab initio calculations. The lattice constant, the bulk modulus and its first pressure derivative, the electronic band structure and the density of states (DOS), mechanical properties such as elastic constants, anisotropy factor, Young's modulus, etc., the phonon dispersion curves and phonon DOS, entropy, heat capacity, and free energy were obtained under pressure. It was determined that the calculated lattice parameters are in good agreement with the literature, the elastic constants obey the stability criterion, and the phonon dispersion curves have no negative frequency which shows that the compounds are stable. The band structures at 0, 50, and 70 GPa showed valence instability at the L point which explains the superconductivity in Pd2TiX (X=Ga, In).

Three-body interactions and the elastic constants of hcp solid 4He

NASA Astrophysics Data System (ADS)

Barnes, Ashleigh L.; Hinde, Robert J.

2017-09-01

The effect of three-body interactions on the elastic properties of hexagonal close packed solid 4He is investigated using variational path integral (VPI) Monte Carlo simulations. The solid's nonzero elastic constants are calculated, at T = 0 K and for a range of molar volumes from 7.88 cm3/mol to 20.78 cm3/mol, from the bulk modulus and the three pure shear constants C0, C66, and C44. Three-body interactions are accounted for using our recently reported perturbative treatment based on the nonadditive three-body potential of Cencek et al. Previous studies have attempted to account for the effect of three-body interactions on the elastic properties of solid 4He; however, these calculations have treated zero point motions using either the Einstein or Debye approximations, which are insufficient in the molar volume range where solid 4He is characterized as a quantum solid. Our VPI calculations allow for a more accurate treatment of the zero point motions which include atomic correlation. From these calculations, we find that agreement with the experimental bulk modulus is significantly improved when three-body interactions are considered. In addition, three-body interactions result in non-negligible differences in the calculated pure shear constants and nonzero elastic constants, particularly at higher densities, where differences of up to 26.5% are observed when three-body interactions are included. We compare to the available experimental data and find that our results are generally in as good or better agreement with experiment as previous theoretical investigations.

Combining AFM and Acoustic Probes to Reveal Changes in the Elastic Stiffness Tensor of Living Cells

PubMed Central

Nijenhuis, Nadja; Zhao, Xuegen; Carisey, Alex; Ballestrem, Christoph; Derby, Brian

2014-01-01

Knowledge of how the elastic stiffness of a cell affects its communication with its environment is of fundamental importance for the understanding of tissue integrity in health and disease. For stiffness measurements, it has been customary to quote a single parameter quantity, e.g., Young’s modulus, rather than the minimum of two terms of the stiffness tensor required by elasticity theory. In this study, we use two independent methods (acoustic microscopy and atomic force microscopy nanoindentation) to characterize the elastic properties of a cell and thus determine two independent elastic constants. This allows us to explore in detail how the mechanical properties of cells change in response to signaling pathways that are known to regulate the cell’s cytoskeleton. In particular, we demonstrate that altering the tensioning of actin filaments in NIH3T3 cells has a strong influence on the cell's shear modulus but leaves its bulk modulus unchanged. In contrast, altering the polymerization state of actin filaments influences bulk and shear modulus in a similar manner. In addition, we can use the data to directly determine the Poisson ratio of a cell and show that in all cases studied, it is less than, but very close to, 0.5 in value. PMID:25296302

First Principles Investigation of Fluorine Based Strontium Series of Perovskites

NASA Astrophysics Data System (ADS)

Erum, Nazia; Azhar Iqbal, Muhammad

2016-11-01

Density functional theory is used to explore structural, elastic, and mechanical properties of SrLiF3, SrNaF3, SrKF3 and SrRbF3 fluoroperovskite compounds by means of an ab-initio Full Potential-Linearized Augmented Plane Wave (FP-LAPW) method. Several lattice parameters are employed to obtain accurate equilibrium volume (Vo). The resultant quantities include ground state energy, elastic constants, shear modulus, bulk modulus, young's modulus, cauchy's pressure, poisson's ratio, shear constant, ratio of elastic anisotropy factor, kleinman's parameter, melting temperature, and lame's coefficient. The calculated structural parameters via DFT as well as analytical methods are found to be consistent with experimental findings. Chemical bonding is used to investigate corresponding chemical trends which authenticate combination of covalent-ionic behavior. Furthermore electron density plots as well as elastic and mechanical properties are reported for the first time which reveals that fluorine based strontium series of perovskites are mechanically stable and posses weak resistance towards shear deformation as compared to resistance towards unidirectional compression while brittleness and ionic behavior is dominated in them which decreases from SrLiF3 to SrRbF3. Calculated cauchy's pressure, poisson's ratio and B/G ratio also proves ionic nature in these compounds. The present methodology represents an effective and influential approach to calculate the whole set of elastic and mechanical parameters which would support to understand various physical phenomena and empower device engineers for implementing these materials in numerous applications.

Macroscopic elastic properties of textured ZrN-AlN polycrystalline aggregates: From ab initio calculations to grain-scale interactions

NASA Astrophysics Data System (ADS)

Holec, D.; Tasnádi, F.; Wagner, P.; Friák, M.; Neugebauer, J.; Mayrhofer, P. H.; Keckes, J.

2014-11-01

Despite the fast development of computational material modeling, the theoretical description of macroscopic elastic properties of textured polycrystalline aggregates starting from basic principles remains a challenging task. In this study we use a supercell-based approach to obtain the elastic properties of a random solid solution cubic Zr1 -xAlxN system as a function of the metallic sublattice composition and texture descriptors. The employed special quasirandom structures are optimized not only with respect to short-range-order parameters, but also to make the three cubic directions [1 0 0 ] , [0 1 0 ] , and [0 0 1 ] as similar as possible. In this way, only a small spread of elastic constant tensor components is achieved and an optimum trade-off between modeling of chemical disorder and computational limits regarding the supercell size and calculational time is proposed. The single-crystal elastic constants are shown to vary smoothly with composition, yielding x ≈0.5 an alloy constitution with an almost isotropic response. Consequently, polycrystals with this composition are suggested to have Young's modulus independent of the actual microstructure. This is indeed confirmed by explicit calculations of polycrystal elastic properties, both within the isotropic aggregate limit and with fiber textures with various orientations and sharpness. It turns out that for low AlN mole fractions, the spread of the possible Young's modulus data caused by the texture variation can be larger than 100 GPa. Consequently, our discussion of Young's modulus data of cubic Zr1 -xAlxN contains also the evaluation of the texture typical for thin films.

Evaluation of copper, aluminum, and nickel interatomic potentials on predicting the elastic properties

NASA Astrophysics Data System (ADS)

Rassoulinejad-Mousavi, Seyed Moein; Mao, Yijin; Zhang, Yuwen

2016-06-01

Choice of appropriate force field is one of the main concerns of any atomistic simulation that needs to be seriously considered in order to yield reliable results. Since investigations on the mechanical behavior of materials at micro/nanoscale have been becoming much more widespread, it is necessary to determine an adequate potential which accurately models the interaction of the atoms for desired applications. In this framework, reliability of multiple embedded atom method based interatomic potentials for predicting the elastic properties was investigated. Assessments were carried out for different copper, aluminum, and nickel interatomic potentials at room temperature which is considered as the most applicable case. Examined force fields for the three species were taken from online repositories of National Institute of Standards and Technology, as well as the Sandia National Laboratories, the LAMMPS database. Using molecular dynamic simulations, the three independent elastic constants, C11, C12, and C44, were found for Cu, Al, and Ni cubic single crystals. Voigt-Reuss-Hill approximation was then implemented to convert elastic constants of the single crystals into isotropic polycrystalline elastic moduli including bulk modulus, shear modulus, and Young's modulus as well as Poisson's ratio. Simulation results from massive molecular dynamic were compared with available experimental data in the literature to justify the robustness of each potential for each species. Eventually, accurate interatomic potentials have been recommended for finding each of the elastic properties of the pure species. Exactitude of the elastic properties was found to be sensitive to the choice of the force fields. Those potentials that were fitted for a specific compound may not necessarily work accurately for all the existing pure species. Tabulated results in this paper might be used as a benchmark to increase assurance of using the interatomic potential that was designated for a problem.

Lattice Mechanical Properties of Noble and Transition Metals

NASA Astrophysics Data System (ADS)

Baria, J. K.

2004-04-01

A model pseudopotential depending on an effective core radius but otherwise parameter free is used to study the interatomic interactions, phonon dispersion curves (in q and r-space analysis), phonon density of states, mode Grüneisen parameters, dynamical elastic constants ( C 11, C 12 and C 44), bulk modulus ( B), shear modulus ( C'), deviation from Cauchy relation ( C 12 C 44), Poisson’s ratio ( σ), Young’s modulus ( Y), behavior of phonon frequencies in the elastic limit independent of the direction ( Y 1), limiting value in the [110] direction ( Y 2), degree of elastic anisotropy ( A), maximum frequency ω max, mean frequency < ω>, < ω 2>1/2=(< ω>/< ω -1>)1/2, fundamental frequency < ω 2>, and propagation velocities of the elastic constants in Cu, Ag, Au, Ni, Pd, and Pt. The contribution of s-like electrons is calculated in the second-order perturbation theory for the model potential while that of d-like electrons is taken into account by introducing repulsive short-range Born-Mayer like term. Very recently proposed screening function due to Sarkar et al. has been used to obtain the screened form factor. The theoretical results are compared with experimental findings wherever possible. A good agreement between theoretical investigations and experimental findings has proved the ability of our model potential for predicting a large number of physical properties of transition metals.

Modelling of single walled carbon nanotube cylindrical structures with finite element method simulations

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

Günay, E.

In this study, the modulus of elasticity and shear modulus values of single-walled carbon nanotubes SWCNTs were modelled by using both finite element method and the Matlab code. Initially, cylindrical armchair and zigzag single walled 3D space frames were demonstrated as carbon nanostructures. Thereafter, macro programs were written by the Matlab code producing the space truss for zigzag and armchair models. 3D space frames were introduced to the ANSYS software and then tension, compression and additionally torsion tests were performed on zigzag and armchair carbon nanotubes with BEAM4 element in obtaining the exact values of elastic and shear modulus values.more » In this study, two different boundary conditions were tested and especially used in torsion loading. The equivalent shear modulus data was found by averaging the corresponding values obtained from ten different nodal points on the nanotube path. Finally, in this study it was determined that the elastic constant values showed proportional changes by increasing the carbon nanotube diameters up to a certain level but beyond this level these values remained stable.« less

Study on Topology Optimization Design, Manufacturability, and Performance Evaluation of Ti-6Al-4V Porous Structures Fabricated by Selective Laser Melting (SLM)

PubMed Central

Xu, Yangli; Zhang, Dongyun; Zhou, Yan; Wang, Weidong; Cao, Xuanyang

2017-01-01

The combination of topology optimization (TOP) and selective laser melting (SLM) provides the possibility of fabricating the complex, lightweight and high performance geometries overcoming the traditional manufacturing “bottleneck”. This paper evaluates the biomechanical properties of porous structures with porosity from 40% to 80% and unit cell size from 2 to 8 mm, which are designed by TOP and manufactured by SLM. During manufacturability exploration, three typical structures including spiral structure, arched bridge structure and structures with thin walls and small holes are abstracted and investigated, analyzing their manufacturing limits and forming reason. The property tests show that dynamic elastic modulus and compressive strength of porous structures decreases with increases of porosity (constant unit cell size) or unit cell size (constant porosity). Based on the Gibson-Ashby model, three failure models are proposed to describe their compressive behavior, and the structural parameter λ is used to evaluate the stability of the porous structure. Finally, a numerical model for the correlation between porous structural parameters (unit cell size and porosity) and elastic modulus is established, which provides a theoretical reference for matching the elastic modulus of human bones from different age, gender and skeletal sites during innovative medical implant design and manufacturing. PMID:28880229

Study on Topology Optimization Design, Manufacturability, and Performance Evaluation of Ti-6Al-4V Porous Structures Fabricated by Selective Laser Melting (SLM).

PubMed

Xu, Yangli; Zhang, Dongyun; Zhou, Yan; Wang, Weidong; Cao, Xuanyang

2017-09-07

The combination of topology optimization (TOP) and selective laser melting (SLM) provides the possibility of fabricating the complex, lightweight and high performance geometries overcoming the traditional manufacturing "bottleneck". This paper evaluates the biomechanical properties of porous structures with porosity from 40% to 80% and unit cell size from 2 to 8 mm, which are designed by TOP and manufactured by SLM. During manufacturability exploration, three typical structures including spiral structure, arched bridge structure and structures with thin walls and small holes are abstracted and investigated, analyzing their manufacturing limits and forming reason. The property tests show that dynamic elastic modulus and compressive strength of porous structures decreases with increases of porosity (constant unit cell size) or unit cell size (constant porosity). Based on the Gibson-Ashby model, three failure models are proposed to describe their compressive behavior, and the structural parameter λ is used to evaluate the stability of the porous structure. Finally, a numerical model for the correlation between porous structural parameters (unit cell size and porosity) and elastic modulus is established, which provides a theoretical reference for matching the elastic modulus of human bones from different age, gender and skeletal sites during innovative medical implant design and manufacturing.

FP-LAPW based investigation of structural, electronic and mechanical properties of CePb{sub 3} intermetallic compound

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

Pagare, Gitanjali, E-mail: gita-pagare@yahoo.co.in; Jain, Ekta, E-mail: jainekta05@gmail.com; Abraham, Jisha Annie, E-mail: disisjisha@yahoo.com

A theoretical study of structural, electronic, elastic and mechanical properties of CePb{sub 3} intermetallic compound has been investigated systematically using first principles density functional theory. The calculations are carried out within the three different forms of generalized gradient approximation (GGA) and LSDA for the exchange correlation potential. The ground state properties such as lattice parameter (a{sub 0}), bulk modulus (B) and its pressure derivative (B′) are calculated and obtained lattice parameter of this compound shows well agreement with the experimental results. We have calculated three independent second order elastic constants (C{sub 11}, C{sub 12} and C{sub 44}), which has notmore » been calculated and measured yet. From energy dispersion curves, it is found that the studied compound is metallic in nature. Ductility of this compound is analyzed using Pugh’s criteria and Cauchy's pressure (C{sub 11}-C{sub 12}). The mechanical properties such as Young's modulus, shear modulus, anisotropic ratio, Poison's ratio have been calculated for the first time using the Voigt–Reuss–Hill (VRH) averaging scheme. The average sound velocities (v{sub m}), density (ρ) and Debye temperature (θ{sub D}) of this compound are also estimated from the elastic constants.« less

Structural, electronic, and elastic properties of CuFeS2: first-principles study

NASA Astrophysics Data System (ADS)

Zhou, Meng; Gao, Xiang; Cheng, Yan; Chen, Xiangrong; Cai, Lingcang

2015-03-01

The structural, electronic, and elastic properties of CuFeS2 have been investigated by using the generalized gradient approximation (GGA), GGA + U (on-site Coulomb repulsion energy), the local density approximation (LDA), and the LDA + U approach in the frame of density functional theory. It is shown that when the GGA + U formalism is selected with a U value of 3 eV for the 3d state of Fe, the calculated lattice constants agree well with the available experimental and other theoretical data. Our GGA + U calculations indicate that CuFeS2 is a semiconductor with a band gap of 0.552 eV and with a magnetic moment of 3.64 µB per Fe atom, which are well consistent with the experimental results. Combined with the density of states, the band structure characteristics of CuFeS2 have been analyzed and their origins have been specified, which reveals a hybridization existing between Fe-3d, Cu-3s, and S-3p, respectively. The charge and Mulliken population analyses indicate that CuFeS2 is a covalent crystal. Moreover, the calculated elastic constants prove that CuFeS2 is mechanically stable but anisotropic. The bulk modulus obtained from elastic constants is 87.1 GPa, which agrees well with the experimental value of 91 ± 15 GPa and better than the theoretical bulk modulus 74 GPa obtained from GGA method by Lazewski et al. The obtained shear modulus and Debye temperature are 21.0 GPa and 287 K, respectively, and the latter accords well with the available experimental value. It is expected that our work can provide useful information to further investigate CuFeS2 from both the experimental and theoretical sides.

Effect of single-particle magnetostriction on the shear modulus of compliant magnetoactive elastomers.

PubMed

Kalita, Viktor M; Snarskii, Andrei A; Shamonin, Mikhail; Zorinets, Denis

2017-03-01

The influence of an external magnetic field on the static shear strain and the effective shear modulus of a magnetoactive elastomer (MAE) is studied theoretically in the framework of a recently introduced approach to the single-particle magnetostriction mechanism [V. M. Kalita et al., Phys. Rev. E 93, 062503 (2016)10.1103/PhysRevE.93.062503]. The planar problem of magnetostriction in an MAE with magnetically soft inclusions in the form of a thin disk (platelet) having the magnetic anisotropy in the plane of this disk is solved analytically. An external magnetic field acts with torques on magnetic filler particles, creates mechanical stresses in the vicinity of inclusions, induces shear strain, and increases the effective shear modulus of these composite materials. It is shown that the largest effect of the magnetic field on the effective shear modulus should be expected in MAEs with soft elastomer matrices, where the shear modulus of the matrix is less than the magnetic anisotropy constant of inclusions. It is derived that the effective shear modulus is nonlinearly dependent on the external magnetic field and approaches the saturation value in magnetic fields exceeding the field of particle anisotropy. It is shown that model calculations of the effective shear modulus correspond to a phenomenological definition of effective elastic moduli and magnetoelastic coupling constants. The obtained theoretical results compare well with known experimental data. Determination of effective elastic coefficients in MAEs and their dependence on magnetic field is discussed. The concentration dependence of the effective shear modulus at higher filler concentrations has been estimated using the method of Padé approximants, which predicts that both the absolute and relative changes of the magnetic-field-dependent effective shear modulus will significantly increase with the growing concentration of filler particles.

Effect of single-particle magnetostriction on the shear modulus of compliant magnetoactive elastomers

NASA Astrophysics Data System (ADS)

Kalita, Viktor M.; Snarskii, Andrei A.; Shamonin, Mikhail; Zorinets, Denis

2017-03-01

The influence of an external magnetic field on the static shear strain and the effective shear modulus of a magnetoactive elastomer (MAE) is studied theoretically in the framework of a recently introduced approach to the single-particle magnetostriction mechanism [V. M. Kalita et al., Phys. Rev. E 93, 062503 (2016), 10.1103/PhysRevE.93.062503]. The planar problem of magnetostriction in an MAE with magnetically soft inclusions in the form of a thin disk (platelet) having the magnetic anisotropy in the plane of this disk is solved analytically. An external magnetic field acts with torques on magnetic filler particles, creates mechanical stresses in the vicinity of inclusions, induces shear strain, and increases the effective shear modulus of these composite materials. It is shown that the largest effect of the magnetic field on the effective shear modulus should be expected in MAEs with soft elastomer matrices, where the shear modulus of the matrix is less than the magnetic anisotropy constant of inclusions. It is derived that the effective shear modulus is nonlinearly dependent on the external magnetic field and approaches the saturation value in magnetic fields exceeding the field of particle anisotropy. It is shown that model calculations of the effective shear modulus correspond to a phenomenological definition of effective elastic moduli and magnetoelastic coupling constants. The obtained theoretical results compare well with known experimental data. Determination of effective elastic coefficients in MAEs and their dependence on magnetic field is discussed. The concentration dependence of the effective shear modulus at higher filler concentrations has been estimated using the method of Padé approximants, which predicts that both the absolute and relative changes of the magnetic-field-dependent effective shear modulus will significantly increase with the growing concentration of filler particles.

Measurement of high temperature elastic moduli of an 18Cr-9Ni-2.95 Cu-0.58 Nb-0.1C (Wt %) austenitic stainless steel

NASA Astrophysics Data System (ADS)

Tripathy, Haraprasanna; Hajra, Raj Narayan; Sudha, C.; Raju, S.; Saibaba, Saroja

2018-04-01

The Young's modulus (E) and Shear modulus (G) of an indigenously developed 18Cr-9Ni-0.1C-2.95 Cu-0.58Nb (wt %) austenitic stainless steel has been evaluated in the temperature range 298 K to 1273 K (25 °C to 1000 °C), using Impulse excitation technique (IET). The Bulk modulus (K) and the poison's ratio have been estimated from the measured values of E and G. It is observed that the elastic constants (E, G and K) are found to decrease in a nonlinear fashion with increase in temperature. The Cu precipitation is found to influence the elastic moduli of the steel in the cooling cycle. The observed elastic moduli are fitted to 3rd order polynomial equations in order to describe the temperature dependence of E, G, K moduli in the temperature range 298-1273 K (25 °C to 1000 °C). The room temperature values of E,G and K moduli is found to be 207, 82 and 145 GPa respectively for the present steel.

Pressure effect on the structural, phonon, elastic and thermodynamic properties of L12 phase RH3TA: First-principles calculations

NASA Astrophysics Data System (ADS)

Wang, Leini; Jian, Zhang; Ning, Wei

2018-06-01

The phonon, elastic and thermodynamic properties of L12 phase Rh3Ta have been investigated by the density functional theory (DFT) approach combined with the quasi-harmonic approximation model. The results of the phonon band structure show that L12 phase Rh3Ta possesses dynamical stability in the pressure range from 0-80 GPa due to the absence of imaginary frequencies. The pressure dependences with the elastic constants Cij, shear modulus G, bulk modulus B, Young’s modulus Y, Poisson’s ratio and B/G ratio have been analyzed. The results of the elastic properties studies show that L12 phase Rh3Ta compound is mechanically stable and possesses a higher hardness, improved ductility and plasticity under higher pressures. The pressure and temperature relationship of the thermodynamic properties, such as the Debye temperature ΘD, heat capacity Cp, thermal expansion coefficient α and the Grüneisen parameter γ are predicted by the quasi-harmonic Debye model in a wide pressure (0-80 GPa) and temperature (0-750 K) ranges.

Non-mineralized fibrocartilage shows the lowest elastic modulus in the rabbit supraspinatus tendon insertion: measurement with scanning acoustic microscopy.

PubMed

Sano, Hirotaka; Saijo, Yoshifumi; Kokubun, Shoichi

2006-01-01

The acoustic properties of rabbit supraspinatus tendon insertions were measured by scanning acoustic microscopy. After cutting parallel to the supraspinatus tendon fibers, specimens were fixed with 10% neutralized formalin, embedded in paraffin, and sectioned. Both the sound speed and the attenuation constant were measured at the insertion site. The 2-dimensional distribution of the sound speed and that of the attenuation constant were displayed with color-coded scales. The acoustic properties reflected both the histologic architecture and the collagen type. In the tendon proper and the non-mineralized fibrocartilage, the sound speed and attenuation constant gradually decreased as the predominant collagen type changed from I to II. In the mineralized fibrocartilage, they increased markedly with the mineralization of the fibrocartilaginous tissue. These results indicate that the non-mineralized fibrocartilage shows the lowest elastic modulus among 4 zones at the insertion site, which could be interpreted as an adaptation to various types of biomechanical stress.

Self-consistent elastic continuum theory of degenerate, equilibrium aperiodic solids.

PubMed

Bevzenko, Dmytro; Lubchenko, Vassiliy

2014-11-07

We show that the vibrational response of a glassy liquid at finite frequencies can be described by continuum mechanics despite the vast degeneracy of the vibrational ground state; standard continuum elasticity assumes a unique ground state. The effective elastic constants are determined by the bare elastic constants of individual free energy minima of the liquid, the magnitude of built-in stress, and temperature, analogously to how the dielectric response of a polar liquid is determined by the dipole moment of the constituent molecules and temperature. In contrast with the dielectric constant--which is enhanced by adding polar molecules to the system--the elastic constants are down-renormalized by the relaxation of the built-in stress. The renormalization flow of the elastic constants has three fixed points, two of which are trivial and correspond to the uniform liquid state and an infinitely compressible solid, respectively. There is also a nontrivial fixed point at the Poisson ratio equal to 1/5, which corresponds to an isospin-like degeneracy between shear and uniform deformation. The present description predicts a discontinuous jump in the (finite frequency) shear modulus at the crossover from collisional to activated transport, consistent with the random first order transition theory.

High pressure phase transformation in uranium carbide: A first principle study

NASA Astrophysics Data System (ADS)

Sahoo, B. D.; Joshi, K. D.; Gupta, Satish C.

2013-02-01

First principles calculations have been carried out to analyze structural, elastic and dynamic stability, of UC under hydrostatic compression. The comparison of enthalpies of rocksalt type (B1) and body centered orthorhombic (bco) structures as a function of pressure suggests the B1 →bco transition at ˜ 23 GPa, in good agreement with experimental value of 27 GPa. From the lattice dynamic calculations we have determined the phonon dispersion relations for B1 phase at various compressions. It is found that TA phonon branch along Γ-X direction becomes imaginary around the transition pressure. Further, the phonon instability so caused is of long wavelength nature as it occurs near the Brillouin zone centre. This long wavelength phonon instability at the transition point indicates that the B1 →bco transition is driven by elastic failure (the vanishing of C44 modulus). Various physical quantities such as equilibrium volume, bulk modulus, pressure derivative of bulk modulus and elastic constants have been determined at zero pressure and compared with data available in literature.

Pressure derivatives of elastic moduli of fused quartz to 10 kb

USGS Publications Warehouse

Peselnick, L.; Meister, R.; Wilson, W.H.

1967-01-01

Measurements of the longitudinal and shear moduli were made on fused quartz to 10 kb at 24??5??C. The anomalous behavior of the bulk modulus K at low pressure, ???K ???P 0, at higher pressures. The pressure derivative of the rigidity modulus ???G ???P remains constant and negative for the pressure range covered. A 15-kb hydrostatic pressure vessel is described for use with ultrasonic pulse instrumentation for precise measurements of elastic moduli and density changes with pressure. The placing of the transducer outside the pressure medium, and the use of C-ring pressure seals result in ease of operation and simplicity of design. ?? 1967.

Single-crystal elastic properties of aluminum oxynitride (AlON) from brillouin scattering

DOE PAGES

Satapathy, Sikhanda; Ahart, Muhtar; Dandekar, Dattatraya; ...

2016-01-19

The Brillouin light-scattering technique was used to determine experimentally the three independent elastic constants of cubic aluminum oxynitride at the ambient condition. They are C 11=334.8(±1.8) GPa, C 12=164.4(± 1.2) GPa, and C 44=178.6(± 1.1) GPa. Its bulk modulus is 221.2 GPa. The magnitude of Zener anisotropic ratio is 2.1 similar to other spinels. Here, the anisotropic nature of the material is shown by a large variation in the Young’s modulus and Poisson’s ratio with crystallographic directions. The material was found to be auxetic in certain orientations.

Probing the Effect of Hydrogen on Elastic Properties and Plastic Deformation in Nickel Using Nanoindentation and Ultrasonic Methods

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

Lawrence, Samantha K.; Somerday, Brian P.; Ingraham, Mathew Duffy

Hydrogen effects on small-volume plasticity and elastic stiffness constants are investigated with nanoindentation of Ni-201 and sonic velocity measurements of bulk Ni single crystals. Elastic modulus of Ni-201, calculated from indentation data, decreases ~22% after hydrogen charging. This substantial decrease is independently confirmed by sonic velocity measurements of Ni single crystals; c 44 decreases ~20% after hydrogen exposure. Furthermore, clear hydrogen-deformation interactions are observed. The maximum shear stress required to nucleate dislocations in hydrogen-charged Ni-201 is markedly lower than in as-annealed material, driven by hydrogen-reduced shear modulus. Additionally, a larger number of depth excursions are detected prior to general yieldingmore » in hydrogen-charged material, suggesting cross-slip restriction. Together, these data reveal direct correlation between hydrogen-affected elastic properties and plastic deformation in Ni alloys.« less

Probing the Effect of Hydrogen on Elastic Properties and Plastic Deformation in Nickel Using Nanoindentation and Ultrasonic Methods

DOE PAGES

Lawrence, Samantha K.; Somerday, Brian P.; Ingraham, Mathew Duffy; ...

2018-04-11

Hydrogen effects on small-volume plasticity and elastic stiffness constants are investigated with nanoindentation of Ni-201 and sonic velocity measurements of bulk Ni single crystals. Elastic modulus of Ni-201, calculated from indentation data, decreases ~22% after hydrogen charging. This substantial decrease is independently confirmed by sonic velocity measurements of Ni single crystals; c 44 decreases ~20% after hydrogen exposure. Furthermore, clear hydrogen-deformation interactions are observed. The maximum shear stress required to nucleate dislocations in hydrogen-charged Ni-201 is markedly lower than in as-annealed material, driven by hydrogen-reduced shear modulus. Additionally, a larger number of depth excursions are detected prior to general yieldingmore » in hydrogen-charged material, suggesting cross-slip restriction. Together, these data reveal direct correlation between hydrogen-affected elastic properties and plastic deformation in Ni alloys.« less

Probing the Effect of Hydrogen on Elastic Properties and Plastic Deformation in Nickel Using Nanoindentation and Ultrasonic Methods

NASA Astrophysics Data System (ADS)

Lawrence, S. K.; Somerday, B. P.; Ingraham, M. D.; Bahr, D. F.

2018-04-01

Hydrogen effects on small-volume plasticity and elastic stiffness constants are investigated with nanoindentation of Ni-201 and sonic velocity measurements of bulk Ni single crystals. Elastic modulus of Ni-201, calculated from indentation data, decreases 22% after hydrogen charging. This substantial decrease is independently confirmed by sonic velocity measurements of Ni single crystals; c 44 decreases 20% after hydrogen exposure. Furthermore, clear hydrogen-deformation interactions are observed. The maximum shear stress required to nucleate dislocations in hydrogen-charged Ni-201 is markedly lower than in as-annealed material, driven by hydrogen-reduced shear modulus. Additionally, a larger number of depth excursions are detected prior to general yielding in hydrogen-charged material, suggesting cross-slip restriction. Together, these data reveal a direct correlation between hydrogen-affected elastic properties and plastic deformation in Ni alloys.

AnisoVis: a MATLAB™ toolbox for the visualisation of elastic anisotropy

NASA Astrophysics Data System (ADS)

Healy, D.; Timms, N.; Pearce, M. A.

2016-12-01

The elastic properties of rocks and minerals vary with direction, and this has significant consequences for their physical response to acoustic waves and natural or imposed stresses. This anisotropy of elasticity is well described mathematically by 4th rank tensors of stiffness or compliance. These tensors are not easy to visualise in a single diagram or graphic, and visualising Poisson's ratio and shear modulus presents a further challenge in that their anisotropy depends on two principal directions. Students and researchers can easily underestimate the importance of elastic anisotropy. This presentation describes an open source toolbox of MATLAB scripts that aims to visualise elastic anisotropy in rocks and minerals. The code produces linked 2-D and 3-D representations of the standard elastic constants, such as Young's modulus, Poisson's ratio and shear modulus, all from a simple GUI. The 3-D plots can be manipulated by the user (rotated, panned, zoomed), to encourage investigation and a deeper understanding of directional variations in the fundamental properties. Examples are presented of common rock forming minerals, including those with negative Poisson's ratio (auxetic behaviour). We hope that an open source code base will encourage further enhancements from the rock physics and wider geoscience communities. Eventually, we hope to generate 3-D prints of these complex and beautiful natural surfaces to provide a tactile link to the underlying physics of elastic anisotropy.

Thermal equation of state of silicon carbide

NASA Astrophysics Data System (ADS)

Wang, Yuejian; Liu, Zhi T. Y.; Khare, Sanjay V.; Collins, Sean Andrew; Zhang, Jianzhong; Wang, Liping; Zhao, Yusheng

2016-02-01

A large volume press coupled with in-situ energy-dispersive synchrotron X-ray was used to probe the change of silicon carbide (SiC) under high pressure and temperature (P-T) up to 8.1 GPa and 1100 K. The obtained pressure-volume-temperature data were fitted to a modified high-T Birch-Murnaghan equation of state, yielding values of a series of thermo-elastic parameters, such as the ambient bulk modulus KTo = 237(2) GPa, temperature derivative of the bulk modulus at a constant pressure (∂K/∂T)P = -0.037(4) GPa K-1, volumetric thermal expansivity α(0, T) = a + bT with a = 5.77(1) × 10-6 K-1 and b = 1.36(2) × 10-8 K-2, and pressure derivative of the thermal expansion at a constant temperature (∂α/∂P)T = 6.53 ± 0.64 × 10-7 K-1 GPa-1. Furthermore, we found the temperature derivative of the bulk modulus at a constant volume, (∂KT/∂T)V, equal to -0.028(4) GPa K-1 by using a thermal pressure approach. In addition, the elastic properties of SiC were determined by density functional theory through the calculation of Helmholtz free energy. The computed results generally agree well with the experimentally determined values.

Thermal equation of state of silicon carbide

DOE PAGES

Wang, Yuejian; Liu, Zhi T. Y.; Khare, Sanjay V.; ...

2016-02-11

A large volume press coupled with in-situ energy-dispersive synchrotron X-ray was used to probe the change of silicon carbide (SiC) under high pressure and temperature (P-T) up to 8.1 GPa and 1100 K. The obtained pressure–volume–temperature (P-V-T) data were fitted to a modified high-T Birch-Murnaghan equation of state, yielding values of a series of thermo-elastic parameters, such as, the ambient bulk modulus K To = 237(2) GPa, temperature derivative of bulk modulus at constant pressure (∂K/∂T)P = -0.037(4) GPa K -1, volumetric thermal expansivity α(0, T)=a+bT with a = 5.77(1)×10 -6 K -1 and b = 1.36(2)×10 -8 K -2,more » and pressure derivative of thermal expansion at constant temperature (∂α/∂P) T =6.53±0.64×10 -7 K -1GPa -1. Furthermore, we found the temperature derivative of bulk modulus at constant volume, (∂K T/∂T) V, equal to -0.028(4) GPa K -1 by using a thermal pressure approach. In addition, the elastic properties of SiC were determined by density functional theory through the calculation of Helmholtz free energy. Lastly, the computed results generally agree well with the experimental values.« less

Elastic energy distribution in bi-material lithosphere: implications for shear zone formation

NASA Astrophysics Data System (ADS)

So, B.; Yuen, D. A.

2013-12-01

Shear instability in the lithosphere can cause mechanical rupturing such as slab detachment and deep focus earthquake. Recent studies reported that bi-material interface, which refers to sharp elastic modulus contrast, plays an important role in triggering the instability [So and Yuen et al., 2012, GJI]. In present study, we performed two-dimensional numerical simulations to investigate the distribution of thermal-mechanical energy within the bi-material lithosphere. Under the far-field constant compression exerted on the domain, a larger elastic energy is accumulated into the compliant part than stiff medium. For instance, the compliant part has two times greater elastic energy density than surrounding stiff part, when the elastic modulus contrast between two different parts is five. Although these elastic energies in both parts are conversed into thermal energies after plastic yielding, denser elastic energy in the compliant is released more efficiently. This leads to efficient strength weakening and the subsequent ductile shear zone in the compliant part. We propose that strong shear heating occurs in lithosphere with the bi-material interface due to locally non-uniform distribution of the energy around the interface.

Structural and elastoplastic properties of β -Ga2O3 films grown on hybrid SiC/Si substrates

NASA Astrophysics Data System (ADS)

Osipov, A. V.; Grashchenko, A. S.; Kukushkin, S. A.; Nikolaev, V. I.; Osipova, E. V.; Pechnikov, A. I.; Soshnikov, I. P.

2018-04-01

Structural and mechanical properties of gallium oxide films grown on (001), (011) and (111) silicon substrates with a buffer layer of silicon carbide are studied. The buffer layer was fabricated by the atom substitution method, i.e., one silicon atom per unit cell in the substrate was substituted by a carbon atom by chemical reaction with carbon monoxide. The surface and bulk structure properties of gallium oxide films have been studied by atomic-force microscopy and scanning electron microscopy. The nanoindentation method was used to investigate the elastoplastic characteristics of gallium oxide, and also to determine the elastic recovery parameter of the films under study. The ultimate tensile strength, hardness, elastic stiffness constants, elastic compliance constants, Young's modulus, linear compressibility, shear modulus, Poisson's ratio and other characteristics of gallium oxide have been calculated by quantum chemistry methods based on the PBESOL functional. It is shown that all these properties of gallium oxide are essentially anisotropic. The calculated values are compared with experimental data. We conclude that a change in the silicon orientation leads to a significant reorientation of gallium oxide.

Determination of elastic constants of a generally orthotropic plate by modal analysis

NASA Astrophysics Data System (ADS)

Lai, T. C.; Lau, T. C.

1993-01-01

This paper describes a method of finding the elastic constants of a generally orthotropic composite thin plate through modal analysis based on a Rayleigh-Ritz formulation. The natural frequencies and mode shapes for a plate with free-free boundary conditions are obtained with chirp excitation. Based on the eigenvalue equation and the constitutive equations of the plate, an iteration scheme is derived using the experimentally determined natural frequencies to arrive at a set of converged values for the elastic constants. Four sets of experimental data are required for the four independent constants: namely the two Young's moduli E1 and E2, the in-plane shear modulus G12, and one Poisson's ratio nu12. The other Poisson's ratio nu21 can then be determined from the relationship among the constants. Comparison with static test results indicate good agreement. Choosing the right combinations of natural modes together with a set of reasonable initial estimates for the constants to start the iteration has been found to be crucial in achieving convergence.

Does maltose influence on the elasticity of SOPC membrane?

NASA Astrophysics Data System (ADS)

Genova, J.; Zheliaskova, A.; Mitov, M. D.

2010-11-01

Thermally induced shape fluctuations of giant quasi-spherical lipid vesicles are used to study the influence of the disaccharide maltose, dissolved in the aqueous solution, on the curvature elasticity kc of a lipid membrane. The influence of the carbohydrate solute is investigated throughout a considerably wide interval of concentrations. The values of the bending elastic modulus for 200 mM and 400 mM of maltose in the water solution are obtained. The data for kc in presence of maltose is compared with previously obtained results for this constant for the most popular hydrocarbons: monosaccharides glucose and fructose and disaccharides sucrose and trehalose. It is shown that the presence of maltose, dissolved in the aqueous phase surrounding the membrane does not influence on the bending elasticity with the increase of its concentration in the aqueous solution. Up to our knowledge this is the first sugar that does not show decrease of the bending elastic modulus of the lipid membrane, when present in the water surrounding it in concentration up to 400mM.

Evaluation of copper, aluminum, and nickel interatomic potentials on predicting the elastic properties

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

Rassoulinejad-Mousavi, Seyed Moein; Mao, Yijin; Zhang, Yuwen, E-mail: zhangyu@missouri.edu

Choice of appropriate force field is one of the main concerns of any atomistic simulation that needs to be seriously considered in order to yield reliable results. Since investigations on the mechanical behavior of materials at micro/nanoscale have been becoming much more widespread, it is necessary to determine an adequate potential which accurately models the interaction of the atoms for desired applications. In this framework, reliability of multiple embedded atom method based interatomic potentials for predicting the elastic properties was investigated. Assessments were carried out for different copper, aluminum, and nickel interatomic potentials at room temperature which is considered asmore » the most applicable case. Examined force fields for the three species were taken from online repositories of National Institute of Standards and Technology, as well as the Sandia National Laboratories, the LAMMPS database. Using molecular dynamic simulations, the three independent elastic constants, C{sub 11}, C{sub 12}, and C{sub 44}, were found for Cu, Al, and Ni cubic single crystals. Voigt-Reuss-Hill approximation was then implemented to convert elastic constants of the single crystals into isotropic polycrystalline elastic moduli including bulk modulus, shear modulus, and Young's modulus as well as Poisson's ratio. Simulation results from massive molecular dynamic were compared with available experimental data in the literature to justify the robustness of each potential for each species. Eventually, accurate interatomic potentials have been recommended for finding each of the elastic properties of the pure species. Exactitude of the elastic properties was found to be sensitive to the choice of the force fields. Those potentials that were fitted for a specific compound may not necessarily work accurately for all the existing pure species. Tabulated results in this paper might be used as a benchmark to increase assurance of using the interatomic potential that was designated for a problem.« less

High Temperature Elastic Properties of Reduced Activation Ferritic-Martensitic (RAFM) Steel Using Impulse Excitation Technique

NASA Astrophysics Data System (ADS)

Tripathy, Haraprasanna; Raju, Subramanian; Hajra, Raj Narayan; Saibaba, Saroja

2018-03-01

The polycrystalline elastic constants of an indigenous variant of 9Cr-1W-based reduced activation ferritic-martensitic (RAFM) steel have been determined as a function of temperature from 298 K to 1323 K (25 °C to 1000 °C), using impulse excitation technique (IET). The three elastic constants namely, Young's modulus E, shear modulus G, and bulk modulus B, exhibited significant softening with increasing temperature, in a pronounced non-linear fashion. In addition, clearly marked discontinuities in their temperature variations are noticed in the region, where ferrite + carbides → austenite phase transformation occurred upon heating. Further, the incidence of austenite → martensite transformation upon cooling has also been marked by a step-like jump in both elastic E and shear moduli G. The martensite start M s and M f finish temperatures estimated from this study are, M s = 652 K (379 °C) and M f =580 K (307 °C). Similarly, the measured ferrite + carbide → austenite transformation onset ( Ac 1) and completion ( Ac 3) temperatures are found to be 1126 K and 1143 K (853 °C and 870 °C), respectively. The Poisson ratio μ exhibited distinct discontinuities at phase transformation temperatures; but however, is found to vary in the range 0.27 to 0.29. The room temperature estimates of E, G, and μ for normalized and tempered microstructure are found to be 219 GPa, 86.65 GPa, and 0.27, respectively. For the metastable austenite phase, the corresponding values are: 197 GPa, 76.5 GPa, and 0.29, respectively. The measured elastic properties as well as their temperature dependencies are found to be in good accord with reported estimates for other 9Cr-based ferritic-martensitic steel grades. Estimates of θ D el , the elastic Debye temperature and γ G, the thermal Grüneisen parameter obtained from measured bulk elastic properties are found to be θ D el = 465 K (192 °C) and γ G = 1.57.

Porous calcium polyphosphate bone substitutes: additive manufacturing versus conventional gravity sinter processing-effect on structure and mechanical properties.

PubMed

Hu, Youxin; Shanjani, Yaser; Toyserkani, Ehsan; Grynpas, Marc; Wang, Rizhi; Pilliar, Robert

2014-02-01

Porous calcium polyphosphate (CPP) structures proposed as bone-substitute implants and made by sintering CPP powders to form bending test samples of approximately 35 vol % porosity were machined from preformed blocks made either by additive manufacturing (AM) or conventional gravity sintering (CS) methods and the structure and mechanical characteristics of samples so made were compared. AM-made samples displayed higher bending strengths (≈1.2-1.4 times greater than CS-made samples), whereas elastic constant (i.e., effective elastic modulus of the porous structures) that is determined by material elastic modulus and structural geometry of the samples was ≈1.9-2.3 times greater for AM-made samples. X-ray diffraction analysis showed that samples made by either method displayed the same crystal structure forming β-CPP after sinter annealing. The material elastic modulus, E, determined using nanoindentation tests also showed the same value for both sample types (i.e., E ≈ 64 GPa). Examination of the porous structures indicated that significantly larger sinter necks resulted in the AM-made samples which presumably resulted in the higher mechanical properties. The development of mechanical properties was attributed to the different sinter anneal procedures required to make 35 vol % porous samples by the two methods. A primary objective of the present study, in addition to reporting on bending strength and sample stiffness (elastic constant) characteristics, was to determine why the two processes resulted in the observed mechanical property differences for samples of equivalent volume percentage of porosity. An understanding of the fundamental reason(s) for the observed effect is considered important for developing improved processes for preparation of porous CPP implants as bone substitutes for use in high load-bearing skeletal sites. Copyright © 2013 Wiley Periodicals, Inc.

Propagation of elastic wave in nanoporous material with distributed cylindrical nanoholes

NASA Astrophysics Data System (ADS)

Qiang, FangWei; Wei, PeiJun; Liu, XiQiang

2013-08-01

The effective propagation constants of plane longitudinal and shear waves in nanoporous material with random distributed parallel cylindrical nanoholes are studied. The surface elastic theory is used to consider the surface stress effects and to derive the nontraditional boundary condition on the surface of nanoholes. The plane wave expansion method is used to obtain the scattering waves from the single nanohole. The multiple scattering effects are taken into consideration by summing the scattered waves from all scatterers and performing the configuration averaging of random distributed scatterers. The effective propagation constants of coherent waves along with the associated dynamic effective elastic modulus are numerically evaluated. The influences of surface stress are discussed based on the numerical results.

Dose-dependent collagen cross-linking of rabbit scleral tissue by blue light and riboflavin treatment probed by dynamic shear rheology.

PubMed

Schuldt, Carsten; Karl, Anett; Körber, Nicole; Koch, Christian; Liu, Qing; Fritsch, Anatol W; Reichenbach, Andreas; Wiedemann, Peter; Käs, Josef A; Francke, Mike; Iseli, Hans Peter

2015-08-01

To determine the visco-elastic properties of isolated rabbit scleral tissue and dose-dependent biomechanical and morphological changes after collagen cross-linking by riboflavin/blue light treatment. Scleral patches from 87 adult albino rabbit eyes were examined by dynamic shear rheology. Scleral patches were treated by riboflavin and different intensities of blue light (450 nm), and the impact on the visco-elastic properties was determined by various rheological test regimes. The relative elastic modulus was calculated from non-treated and corresponding treated scleral patches, and treatments with different blue light intensities were compared. Shear rheology enables us to study the material properties of scleral tissue within physiological relevant parameters. Cross-linking treatment increased the viscous as well as the elastic modulus and changed the ratio of the elastic versus viscous proportion in scleral tissue. Constant riboflavin application combined with different blue light intensities from 12 mW/cm(2) up to 100 mW/cm(2) increased the relative elastic modulus of scleral tissue by factors up to 1.8. Further enhancement of the applied light intensity caused a decline of the relative elastic modulus. This might be due to destructive changes of the collagen bundle structure at larger light intensities, as observed by histological examination. Collagen cross-linking by riboflavin/blue light application increases the biomechanical stiffness of the sclera in a dose-dependent manner up to certain light intensities. Therefore, this treatment might be a suitable therapeutic approach to stabilize the biomechanical properties of scleral tissue in cases of pathological eye expansion. © 2014 Acta Ophthalmologica Scandinavica Foundation. Published by John Wiley & Sons Ltd.

Ab-initio study of C15-type Laves phase superconductor LaRu2

NASA Astrophysics Data System (ADS)

Kholil, Md. Ibrahim; Islam, Md. Shahinur; Rahman, Md. Atikur

2017-01-01

Structural, elastic, electronic, optical, thermodynamic, and superconducting properties of the Laves phase superconductor LaRu2 with Tc 1.63 K were investigated using the first-principles calculations for the first time. The corresponding evaluated structural parameters are in good agreement with the available theoretical values. The different elastic properties like as, elastic constants, bulk modulus B, shear modulus G, Young's modulus E, and Poisson ratio ν were calculated using the Voigt-Reuss-Hill approximation. The ductility nature appears in both values of Cauchy pressure and Pugh's ratio. The band structure and Cauchy pressure shows that the material behaves metallic nature. The calculated total density of state is 6.80 (electrons/eV) of LaRu2. The optical properties such as reflectivity, absorption spectrum, refractive index, dielectric function, conductivity, and energy loss spectrum are also calculated. The photoconductivity reveals the metallic nature of LaRu2 and absorption coefficient is good in the infrared region. The evaluated density and Debye temperature are 9.55 gm/cm3 and 110.51 K, respectively. In addition, the study of thermodynamic properties like as minimum thermal conductivity, melting temperature, and Dulong-Petit limit are 0.26 (Wm-1 K-1), 1,471.65 K, and 74.80 (J/mole K), respectively. Finally, the investigated electron-phonon coupling constant is 0.66 of LaRu2 superconductor.

Modelling Pre-eruptive Progressive Damage in Basaltic Volcanoes: Consequences for the Pre-eruptive Process

NASA Astrophysics Data System (ADS)

Got, J. L.; Amitrano, D.; Carrier, A.; Marsan, D.; Jouanne, F.; Vogfjord, K. S.

2017-12-01

At Grimsvötn volcano, high-quality earthquake and continuous GPS data were recorded by the Icelandic Meteorological Office during its 2004-2011 inter-eruptive period and exhibited remarkable patterns : acceleration of the cumulated earthquake number, and a 2-year exponential decrease in displacement rate followed by a 4-year constant inflation rate. We proposed a model with one magma reservoir in a non-linear elastic damaging edifice, with incompressible magma and a constant pressure at the base of the magma conduit. We first modelled seismicity rate and damage as a function of time, and show that Kachanov's elastic brittle damage law may be used to express the decrease of the effective shear modulus with time. We then derived simple analytical expressions for the magma reservoir overpressure and the surface displacement as a function of time. We got a very good fit of the seismicity and surface displacement data by adjusting only three phenomenological parameters and computed magma reservoir overpressure, magma flow and strain power as a function of time. Overpressure decrease is controlled by damage and shear modulus decrease. Displacement increases, although overpressure is decreasing, because shear modulus decreases more than overpressure. Normalized strain power reaches a maximum 0.25 value. This maximum is a physical limit, after which the elasticity laws are no longer valid, earthquakes cluster, cumulative number of earthquakes departs from the model. State variable extrema provide four reference times that may be used to assess the mechanical state and dynamics of the volcanic edifice. We also performed the spatial modelling of the progressive damage and strain localization around a pressurized magma reservoir. We used Kachanov's damage law and finite element modelling of an initially elastic volcanic edifice pressurized by a spherical magma reservoir, with a constant pressure in the reservoir and various external boundary conditions. At each node of the model, Young's modulus is decreased if deviatoric stress locally reaches the Mohr-Coulomb plastic threshold. For a compressive horizontal stress, the result shows a complex strain localization pattern, showing reverse and normal faulting very similar to what is obtained from analog modelling and observed at volcanic resurgent domes.

First-principles calculations of the electronic, vibrational, and elastic properties of the magnetic laminate Mn₂GaC

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

Thore, A., E-mail: andth@ifm.liu.se; Dahlqvist, M., E-mail: madah@ifm.liu.se, E-mail: bjoal@ifm.liu.se, E-mail: johro@ifm.liu.se; Alling, B., E-mail: madah@ifm.liu.se, E-mail: bjoal@ifm.liu.se, E-mail: johro@ifm.liu.se

2014-09-14

In this paper, we report the by first-principles predicted properties of the recently discovered magnetic MAX phase Mn₂GaC. The electronic band structure and vibrational dispersion relation, as well as the electronic and vibrational density of states, have been calculated. The band structure close to the Fermi level indicates anisotropy with respect to electrical conductivity, while the distribution of the electronic and vibrational states for both Mn and Ga depend on the chosen relative orientation of the Mn spins across the Ga sheets in the Mn–Ga–Mn trilayers. In addition, the elastic properties have been calculated, and from the five elastic constants,more » the Voigt bulk modulus is determined to be 157 GPa, the Voigt shear modulus 93 GPa, and the Young's modulus 233 GPa. Furthermore, Mn₂GaC is found relatively elastically isotropic, with a compression anisotropy factor of 0.97, and shear anisotropy factors of 0.9 and 1, respectively. The Poisson's ratio is 0.25. Evaluated elastic properties are compared to theoretical and experimental results for M₂AC phases where M = Ti, V, Cr, Zr, Nb, Ta, and A = Al, S, Ge, In, Sn.« less

Full potential study of the elastic, electronic, and optical properties of spinels MgIn{sub 2}S{sub 4} and CdIn{sub 2}S{sub 4} under pressure effect

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

Semari, F.; Khenata, R.; Depatment of Physics and Astronomy, King Saud University, PO Box 2455, Riyadh 11451

2010-12-15

The structural, elastic, electronic, and optical properties of cubic spinel MgIn{sub 2}S{sub 4} and CdIn{sub 2}S{sub 4} compounds have been calculated using a full relativistic version of the full-potential linearized-augmented plane wave with the mixed basis FP/APW+lo method. The exchange and correlation potential is treated by the generalized-gradient approximation (GGA). Moreover, the Engel-Vosko GGA formalism is also applied to optimize the corresponding potential for band structure calculations. The ground state properties, including the lattice constants, the internal parameter, the bulk modulus, and the pressure derivative of the bulk modulus are in reasonable agreement with the available data. Using the totalmore » energy-strain technique, we have determined the full set of first-order elastic constants C{sub ij} and their pressure dependence, which have not been calculated or measured yet. The shear modulus, Young's modulus, and Poisson's ratio are calculated for polycrystalline XIn{sub 2}S{sub 4} aggregates. The Debye temperature is estimated from the average sound velocity. Electronic band structures show a direct band gap ({Gamma}-{Gamma}) for MgIn{sub 2}S{sub 4} and an indirect band gap (K-{Gamma}) for CdIn{sub 2}S{sub 4}. The calculated band gaps with EVGGA show a significant improvement over the GGA. The optical constants, including the dielectric function {epsilon}({omega}), the refractive index n({omega}), the reflectivity R({omega}), and the energy loss function L({omega}) were calculated for radiation up to 30 eV. -- Graphical abstract: Calculated total and partial densities of states for MgIn{sub 2}S{sub 4} and CdIn{sub 2}S{sub 4}« less

A constrained modulus reconstruction technique for breast cancer assessment.

PubMed

Samani, A; Bishop, J; Plewes, D B

2001-09-01

A reconstruction technique for breast tissue elasticity modulus is described. This technique assumes that the geometry of normal and suspicious tissues is available from a contrast-enhanced magnetic resonance image. Furthermore, it is assumed that the modulus is constant throughout each tissue volume. The technique, which uses quasi-static strain data, is iterative where each iteration involves modulus updating followed by stress calculation. Breast mechanical stimulation is assumed to be done by two compressional rigid plates. As a result, stress is calculated using the finite element method based on the well-controlled boundary conditions of the compression plates. Using the calculated stress and the measured strain, modulus updating is done element-by-element based on Hooke's law. Breast tissue modulus reconstruction using simulated data and phantom modulus reconstruction using experimental data indicate that the technique is robust.

Determination of the Mechanical Properties of Plasma-Sprayed Hydroxyapatite Coatings Using the Knoop Indentation Technique

NASA Astrophysics Data System (ADS)

Hasan, Md. Fahad; Wang, James; Berndt, Christopher

2015-06-01

The microhardness and elastic modulus of plasma-sprayed hydroxyapatite coatings were evaluated using Knoop indentation on the cross section and on the top surface. The effects of indentation angle, testing direction, measurement location and applied load on the microhardness and elastic modulus were investigated. The variability and distribution of the microhardness and elastic modulus data were statistically analysed using the Weibull modulus distribution. The results indicate that the dependence of microhardness and elastic modulus on the indentation angle exhibits a parabolic shape. Dependence of the microhardness values on the indentation angle follows Pythagoras's theorem. The microhardness, Weibull modulus of microhardness and Weibull modulus of elastic modulus reach their maximum at the central position (175 µm) on the cross section of the coatings. The Weibull modulus of microhardness revealed similar values throughout the thickness, and the Weibull modulus of elastic modulus shows higher values on the top surface compared to the cross section.

Insight into the structural, electronic, elastic and optical properties of the alkali hydride compounds, XH (X = Rb and Cs)

NASA Astrophysics Data System (ADS)

Jaradat, Raed; Abu-Jafar, Mohammed; Abdelraziq, Issam; Mousa, Ahmad; Ouahrani, Tarik; Khenata, Rabah

2018-04-01

The equilibrium structural parameters, electronic and optical properties of the alkali hydrides RbH and CsH compounds in rock-salt (RS) and cesium chloride (CsCl) structures have been studied using the full-potential linearized augmented plane-wave (FP-LAPW) method. Wu and Cohen generalized gradient approximation (WC-GGA) was used for the exchange-correlation potential to compute the equilibrium structural parameters, such as the lattice constant (a0), the bulk modulus (B) and bulk modulus first order pressure derivative (B'). In addition to the WC-GGA, the modified Becke Johnson (mBJ) scheme has been also used to overcome the underestimation of the band gap energies. RbH and CsH compounds are found to be semiconductors (wide energy-band gap) using the WC-GGA method, while they are insulators using the mBJ-GGA method. Elastic constants, mechanical and thermodynamic properties were obtained by using the IRelast package. RbH and CsH compounds at ambient pressure are mechanically stable in RS and CsCl structures; they satisfy the Born mechanical stability criteria. Elastic constants (Cij), bulk modulus (B), shear modulus (S) and Debye temperatures (θD) of RbH and CsH compounds decrease as the alkali radius increases. The RS structure of these compounds at ambient conditions is mechanically stronger than CsCl structure. RbH and CsH in RS and CsCl structures are suitable as dielectric compounds. The wide direct energy band gap for these compounds make them promising compounds for optoelectronic UV device applications. Both RbH and CsH have a wide absorption region, on the other hand RbH absorption is very huge compared to the CsH absorption, RbH is an excellent absorbent material, maximum absorption regions are located in the middle ultraviolet (MUV) region and far ultraviolet (FUV) region. The absorption coefficient α (w), imaginary part of the dielectric constant ɛ2(w) and the extinction coefficient k(w) vary in the same way. The present calculated results are in good agreement with the experimental data, indicating the high accuracy of the performed calculations and reliability of the obtained results.

Deformation Studies and Elasticity Measurements of Hydrophobic Silica Aerogels using Double Exposure Holographic Interferometry

NASA Astrophysics Data System (ADS)

Chikode, Prashant; Sabale, Sandip; Chavan, Sugam

2017-01-01

Holographic interferometry is mainly used for the non-destructive testing of various materials and metals in industry, engineering and technological fields. This technique may used to study the elastic properties of materials. We have used the double exposure holographic interferometry (DEHI) to study the surface deformation and elastic constant such as Young's modulus of mechanically stressed aerogel samples. Efforts have been made in the past to use non-destructive techniques like sound velocity measurements through aerogels. Hydrophobic Silica aerogels were prepared by the sol-gel process followed by supercritical methanol drying. The molar ratio of tetramethoxysilane: methyltrimethoxysilane: H2O constant at 1.2:0.8:6 while the methanol / tetramethoxysilane molar ratio (M) was varied systematically from 14 to 20 to obtain hydrophobic silica aerogels. After applying the weights on the sample in grams, double exposure holograms of aerogel samples have been successfully recorded. Double exposure causes localization of interference fringes on the aerogel surface and these fringes are used to determine the surface deformation and elastic modulus of the aerogels and they are in good agreement with the experiments performed by using four point bending. University Grants Commission for Minor Research Project and Department of Science and Technology for FIST Program.

Mechanical response of the flux lines in ceramic YBa2Cu3O7-δ

NASA Astrophysics Data System (ADS)

Luzuriaga, J.; André, M.-O.; Benoit, W.

1992-06-01

We have studied the mechanical response of the flux-line lattice (FLL) in ceramic samples of YBa2Cu3O7 by means of a low-frequency forced pendulum. The internal friction and elastic modulus variation of the FLL have been measured as a function of temperature for different values of the applied stress. A somewhat different behavior was observed whether a zero-field-cooling or field-cooling procedure was followed. Measurements of the internal friction and elastic modulus as a function of the applied stress at constant temperature show amplitude-dependent dissipation, with a maximum dissipation at intermediate values of the stress. This dependence is well fitted by a rheological model of extended dry friction, if we restrict ourselves to the dissipation and modulus at fixed temperature. The agreement is not so good when attempting to extend the model to fit the temperature dependence.

Electronic Structure, Mechanical and Dynamical Stability of Hexagonal Subcarbides M2C (M = Tc, Ru, Rh, Pd, Re, Os, Ir, and Pt): Ab Initio Calculations

NASA Astrophysics Data System (ADS)

Suetin, D. V.; Shein, I. R.

2018-02-01

Ab initio calculations were used to study the properties of a series of hexagonal (Fe2N-like) subcarbides M2C, where M = Tc, Ru, Rh, Pd, Re, Os, Ir, and Pt, and to calculate their equilibrium structural parameters, electronic properties, phase stability, elastic constants, compression modulus, shear modulus, Young's modulus, compressibility, Pugh's indicator, Poisson ratio, elastic anisotropy indices, and also hardness, Debye temperature, sound velocity, and low-temperature heat capacity. It is found based on these results that all the subcarbides are mechanically stable; however, their formation energies E form are positive with respect to a mixture of d-metal and graphite. In addition, the calculation of the phonon spectra of these subcarbides shows the existence of negative modes, which indicates their dynamical instability. Thus, a successful synthesis of these subcarbides at normal conditions is highly improbable.

FP-LAPW study of structural, electronic, elastic, mechanical and thermal properties of AlFe intermetallic

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

Jain, Ekta, E-mail: jainekta05@gmail.com; Pagare, Gitanjali, E-mail: gita-pagare@yahoo.co.in; Sanyal, S. P., E-mail: sps.physicsbu@gmail.com

2016-05-06

The structural, electronic, elastic, mechanical and thermal properties of AlFe intermetallic compound in B{sub 2}-type (CsCl) structure have been investigated using first-principles calculations. The exchange-correlation term was treated within generalized gradient approximation. Ground state properties i.e. lattice constants (a{sub 0}), bulk modulus (B) and first-order pressure derivative of bulk modulus (B’) are presented. The density of states are derived which show the metallic character of present compound. Our results for C{sub 11}, C{sub 12} and C{sub 44} agree well with previous theoretical data. Using Pugh’s criteria (B/G{sub H} < 1.75), brittle character of AlFe is satisfied. In addition shear modulusmore » (G{sub H}), Young’s modulus (E), sound wave velocities and Debye temperature (θ{sub D}) have also been estimated.« less

First-principles predictions of structural, mechanical and electronic properties of βTiNb under high pressure

NASA Astrophysics Data System (ADS)

Wang, Z. P.; Fang, Q. H.; Li, J.; Liu, B.

2018-04-01

Structural, mechanical and electronic properties of βTiNb alloy under high pressure have been investigated based on the density functional theory (DFT). The dependences of dimensionless volume ratio, elastic constants, bulk modulus, Young's modulus, shear modulus, ductile/brittle, anisotropy and Poisson's ratio on applied pressure are all calculated successfully. The results reveal that βTiNb alloy is mechanically stable under pressure below 23.45 GPa, and the pressure-induced phase transformation could occur beyond this critical value. Meanwhile, the applied pressure can effectively promote the mechanical properties of βTiNb alloy, including the resistances to volume change, elastic deformation and shear deformation, as well as the material ductility and metallicity. Furthermore, the calculated electronic structures testify that βTiNb alloy performs the metallicity and the higher pressure reduces the structural stability of unit cell.

Material model measurements and predictions for a random pore poly(epsilon-caprolactone) scaffold.

PubMed

Quinn, T P; Oreskovic, T L; Landis, F A; Washburn, N R

2007-07-01

We investigated material models for a polymeric scaffold used for bone. The material was made by co-extruding poly(epsilon-caprolactone) (PCL), a biodegradable polyester, and poly(ethylene oxide) (PEO). The water soluble PEO was removed resulting in a porous scaffold. The stress-strain curve in compression was fit with a phenomenological model in hyperbolic form. This material model will be useful for designers for quasi-static analysis as it provides a simple form that can easily be used in finite element models. The ASTM D-1621 standard recommends using a secant modulus based on 10% strain. The resulting modulus has a smaller scatter in its value compared with the coefficients of the hyperbolic model, and it is therefore easier to compare differences in material processing and ensure quality of the scaffold. A prediction of the small-strain elastic modulus was constructed from images of the microstructure. Each pixel of the micrographs was represented with a brick finite element and assigned the Young's modulus of bulk PCL or a value of 0 for a pore. A compressive strain was imposed on the model and the resulting stresses were calculated. The elastic constants of the scaffold were then computed with Hooke's law for a linear-elastic isotropic material. The model was able to predict the small-strain elastic modulus measured in the experiments to within one standard deviation. Thus, by knowing the microstructure of the scaffold, its bulk properties can be predicted from the material properties of the constituents. Copyright 2006 Wiley Periodicals, Inc.

Ab initio calculations of mechanical properties of bcc W-Re-Os random alloys: effects of transmutation of W

NASA Astrophysics Data System (ADS)

Li, Xiaojie; Schönecker, Stephan; Li, Ruihuan; Li, Xiaoqing; Wang, Yuanyuan; Zhao, Jijun; Johansson, Börje; Vitos, Levente

2016-07-01

To examine the effect of neutron transmutation on tungsten as the first wall material of fusion reactors, the elastic properties of W1-x-y  Re x  Os y (0  ⩽  x, y  ⩽  6%) random alloys in body centered cubic (bcc) structure are investigated systematically using the all-electron exact muffin-tin orbitals (EMTO) method in combination with the coherent-potential approximation (CPA). The calculated lattice constant and elastic properties of pure W are consistent with available experiments. Both Os and Re additions reduce the lattice constant and increase the bulk modulus of W, with Os having the stronger effect. The polycrystalline shear modulus, Young’s modulus and the Debye temperature increase (decrease) with the addition of Re (Os). Except for C 11, the other elastic parameters including C 12, C 44, Cauchy pressure, Poisson ratio, B/G, increase as a function of Re and Os concentration. The variations of the latter three parameters and the trend in the ratio of cleavage energy to shear modulus for the most dominant slip system indicate that the ductility of the alloy enhances with increasing Re and Os content. The calculated elastic anisotropy of bcc W slightly increases with the concentration of both alloying elements. The estimated melting temperatures of the W-Re-Os alloy suggest that Re or Os addition will reduce the melting temperature of pure W solid. The classical Labusch-Nabarro model for solid-solution hardening predicts larger strengthening effects in W1-y  Os y than in W1-x  Re x . A strong correlation between C‧ and the fcc-bcc structural energy difference for W1-x-y  Re x  Os y is revealed demonstrating that canonical band structure dictates the alloying effect on C‧. The structural energy difference is exploited to estimate the alloying effect on the ideal tensile strength in the [0 0 1] direction.

Ab initio calculations of mechanical properties of bcc W-Re-Os random alloys: effects of transmutation of W.

PubMed

Li, Xiaojie; Schönecker, Stephan; Li, Ruihuan; Li, Xiaoqing; Wang, Yuanyuan; Zhao, Jijun; Johansson, Börje; Vitos, Levente

2016-06-03

To examine the effect of neutron transmutation on tungsten as the first wall material of fusion reactors, the elastic properties of W 1-x-y  Re x  Os y (0  ⩽  x, y  ⩽  6%) random alloys in body centered cubic (bcc) structure are investigated systematically using the all-electron exact muffin-tin orbitals (EMTO) method in combination with the coherent-potential approximation (CPA). The calculated lattice constant and elastic properties of pure W are consistent with available experiments. Both Os and Re additions reduce the lattice constant and increase the bulk modulus of W, with Os having the stronger effect. The polycrystalline shear modulus, Young's modulus and the Debye temperature increase (decrease) with the addition of Re (Os). Except for C 11 , the other elastic parameters including C 12 , C 44 , Cauchy pressure, Poisson ratio, B/G, increase as a function of Re and Os concentration. The variations of the latter three parameters and the trend in the ratio of cleavage energy to shear modulus for the most dominant slip system indicate that the ductility of the alloy enhances with increasing Re and Os content. The calculated elastic anisotropy of bcc W slightly increases with the concentration of both alloying elements. The estimated melting temperatures of the W-Re-Os alloy suggest that Re or Os addition will reduce the melting temperature of pure W solid. The classical Labusch-Nabarro model for solid-solution hardening predicts larger strengthening effects in W 1-y  Os y than in W 1-x  Re x . A strong correlation between C' and the fcc-bcc structural energy difference for W 1-x-y  Re x  Os y is revealed demonstrating that canonical band structure dictates the alloying effect on C'. The structural energy difference is exploited to estimate the alloying effect on the ideal tensile strength in the [0 0 1] direction.

The elastic constants of San Carlos olivine to 17 GPa

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

Abramson, E.H.; Brown, J.M.; Slutsky, L.J.

1997-06-01

All elastic constants, the average bulk and shear moduli, and the lattice parameters of San Carlos olivine (Fo{sub 90}) (initial density 3.355gm/cm{sup 3}) have been determined to a pressure of 12 GPa at room temperature. Measurements of c{sub 11}, c{sub 33}, c{sub 13}, and c{sub 55} have been extended to 17 GPa. The pressure dependence of the adiabatic, isotropic (Hashin-Shtrikman bounds) bulk modulus, and shear modulus may be expressed as K{sub HS}=129.4+4.29P and by G{sub HS}=78+1.71P{minus}0.027P{sup 2}, where both the pressure and the moduli are in gigapascals. The isothermal compression of olivine is described by a bulk modulus given asmore » K{sub T}=126.3+4.28P. Elastic constants other than c{sub 55} can be adequately represented by a linear relationship in pressure. In the order (c{sub 11},c{sub 12},c{sub 13},c{sub 22},c{sub 23},c{sub 33},c{sub 44},c{sub 55},c{sub 66}) the 1 bar intercepts (gigapascal units) are (320.5, 68.1, 71.6, 196.5, 76.8, 233.5, 64.0, 77.0, 78.7). The first derivatives are (6.54, 3.86, 3.57, 5.38, 3.37, 5.51, 1.67, 1.81, 1.93). The second derivative for c{sub 55} is {minus}0.070GPa{sup {minus}1}. Incompressibilities for the three axes may also be expressed as linear relationships with pressure. In the order of {bold a, b}, and {bold c} axes the intercepts in gigapascals are (547.8, 285.8, 381.8) and the first derivatives are (20.1, 12.3, 14.0).{copyright} 1997 American Geophysical Union« less

Prediction of Mechanical Properties of Polymers With Various Force Fields

NASA Technical Reports Server (NTRS)

Odegard, Gregory M.; Clancy, Thomas C.; Gates, Thomas S.

2005-01-01

The effect of force field type on the predicted elastic properties of a polyimide is examined using a multiscale modeling technique. Molecular Dynamics simulations are used to predict the atomic structure and elastic properties of the polymer by subjecting a representative volume element of the material to bulk and shear finite deformations. The elastic properties of the polyimide are determined using three force fields: AMBER, OPLS-AA, and MM3. The predicted values of Young s modulus and shear modulus of the polyimide are compared with experimental values. The results indicate that the mechanical properties of the polyimide predicted with the OPLS-AA force field most closely matched those from experiment. The results also indicate that while the complexity of the force field does not have a significant effect on the accuracy of predicted properties, small differences in the force constants and the functional form of individual terms in the force fields determine the accuracy of the force field in predicting the elastic properties of the polyimide.

Measurement of elastic and thermal properties of composite materials using digital speckle pattern interferometry

NASA Astrophysics Data System (ADS)

Kumar, Manoj; Khan, Gufran S.; Shakher, Chandra

2015-08-01

In the present work, application of digital speckle pattern interferometry (DSPI) was applied for the measurement of mechanical/elastic and thermal properties of fibre reinforced plastics (FRP). Digital speckle pattern interferometric technique was used to characterize the material constants (Poisson's ratio and Young's modulus) of the composite material. Poisson ratio based on plate bending and Young's modulus based on plate vibration of material are measured by using DSPI. In addition to this, the coefficient of thermal expansion of composite material is also measured. To study the thermal strain analysis, a single DSPI fringe pattern is used to extract the phase information by using Riesz transform and the monogenic signal. The phase extraction from a single DSPI fringe pattern by using Riesz transform does not require a phase-shifting system or spatial carrier. The elastic and thermal parameters obtained from DSPI are in close agreement with the theoretical predictions available in literature.

Structural and elastic properties of La{sub 2}Mg{sub 17} from first-principles calculations

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

Luo, Tao-Peng; Ma, Li; Pan, Rong-Kai

2013-10-15

Structural and elastic properties of La{sub 2}Mg{sub 17} with layer structure have been investigated within framework of the density functional theory. Different from the general layer-structured materials, the obtained c/a is less than unity. The calculated elastic constants C{sub 33} is larger than C{sub 11}, being novel in comparison with other alloys with layer structure. The calculated bulk, shear and Young’s modulus of La{sub 2}Mg{sub 17} are higher than other Mg–La alloys with higher La content, implying the stronger covalent bonding. Moreover, the elastic isotropies of La{sub 2}Mg{sub 17} are more excellent. The electronic structure within basal plane is highlymore » symmetric, and the electronic interaction within basal plane is slightly weaker than one between basal planes, which reveal the underlying mechanism for the structural and elastic properties of La{sub 2}Mg{sub 17}. - Graphical abstract: The crystal structure (a) and the atomic positions for (b) (0 0 0 2), (c) (0 0 0 4) and (d) (1 2{sup ¯} 1 0) plane of La{sub 2}Mg{sub 17}. Display Omitted - Highlights: • The c/a of La{sub 2}Mg{sub 17} is anomalously less than unity. • It is novel that for La{sub 2}Mg{sub 17} the elastic constants C{sub 33} is larger than C{sub 11}. • The elastic modulus of La{sub 2}Mg{sub 17} is higher than other Mg–La alloys. • The elastic isotropy of La{sub 2}Mg{sub 17} is excellent. • The electronic structure within basal plane is highly symmetric.« less

First-principles calculations of stability, electronic and elastic properties of the precipitates present in 7055 aluminum alloy

NASA Astrophysics Data System (ADS)

Huang, Cheng; Shao, Hongbang; Ma, Yunlong; Huang, Yuanchun; Xiao, Zhengbing

2018-04-01

The structural stability, electronic structures and elastic properties of the strengthening precipitates, namely Al3Zr, MgZn2, Al2CuMg and Al2Cu, present in 7055 aluminum alloy were investigated by the first-principles calculations based on density functional theory (DFT). The optimized structural parameters are in good agreement with literature values available. It is found that Al3Zr has the strongest alloying ability and structural stability, while for MgZn2, its structural stability is the worst. The calculated electronic results indicate that covalent bonding is the dominant cohesion of Al3Zr, whereas the fractional ionic interactions coexisting with metallic bonding are found in MgZn2, Al2CuMg and Al2Cu. The elastic constants Cij of these precipitates were calculated, and the bulk modulus, shear modulus, Young’s modulus, Poisson’s ratio and universal elastic anisotropy were derived. It is suggested that MgZn2 is ductile, whereas Al3Zr, Al2CuMg and Al2Cu are brittle, and the elastic anisotropies of them increase in the following sequence: Al3Zr

Measurement of elastic pp scattering at $$\\sqrt{\\hbox {s}} = \\hbox {8}$$ TeV in the Coulomb–nuclear interference region: Determination of the ρ-parameter and the total cross-section

DOE PAGES

Antchev, G.; Aspell, P.; Atanassov, I.; ...

2016-11-30

Here, the TOTEM experiment at the CERN LHC has measured elastic proton–proton scattering at the centre-of-mass energy s√=8TeV and four-momentum transfers squared, |t|, from 6 × 10 –4 to 0.2 GeV 2. Near the lower end of the t-interval the differential cross-section is sensitive to the interference between the hadronic and the electromagnetic scattering amplitudes. This article presents the elastic cross-section measurement and the constraints it imposes on the functional forms of the modulus and phase of the hadronic elastic amplitude. The data exclude the traditional Simplified West and Yennie interference formula that requires a constant phase and a purelymore » exponential modulus of the hadronic amplitude. For parametrisations of the hadronic modulus with second- or third-order polynomials in the exponent, the data are compatible with hadronic phase functions giving either central or peripheral behaviour in the impact parameter picture of elastic scattering. In both cases, the ρ-parameter is found to be 0.12±0.03. The results for the total hadronic cross-section are σ tot = (102.9±2.3) mb and (103.0±2.3) mb for central and peripheral phase formulations, respectively. Both are consistent with previous TOTEM measurements.« less

Mechanisms governing the visco-elastic responses of living cells assessed by foam and tensegrity models.

PubMed

Cañadas, P; Laurent, V M; Chabrand, P; Isabey, D; Wendling-Mansuy, S

2003-11-01

The visco-elastic properties of living cells, measured to date by various authors, vary considerably, depending on the experimental methods and/or on the theoretical models used. In the present study, two mechanisms thought to be involved in cellular visco-elastic responses were analysed, based on the idea that the cytoskeleton plays a fundamental role in cellular mechanical responses. For this purpose, the predictions of an open unit-cell model and a 30-element visco-elastic tensegrity model were tested, taking into consideration similar properties of the constitutive F-actin. The quantitative predictions of the time constant and viscosity modulus obtained by both models were compared with previously published experimental data obtained from living cells. The small viscosity modulus values (10(0)-10(3) Pa x s) predicted by the tensegrity model may reflect the combined contributions of the spatially rearranged constitutive filaments and the internal tension to the overall cytoskeleton response to external loading. In contrast, the high viscosity modulus values (10(3)-10(5) Pa x s) predicted by the unit-cell model may rather reflect the mechanical response of the cytoskeleton to the bending of the constitutive filaments and/or to the deformation of internal components. The present results suggest the existence of a close link between the overall visco-elastic response of micromanipulated cells and the underlying architecture.

Polycrystalline elastic moduli of a high-entropy alloy at cryogenic temperatures

DOE PAGES

Haglund, A.; Koehler, M.; Catoor, D.; ...

2014-12-05

A FCC high-entropy alloy (HEA) that exhibits strong temperature dependence of strength at low homologous temperatures in sharp contrast to pure FCC metals like Ni that show weak temperature dependence is CrMnCoFeNi. In order to understand this behavior, elastic constants were determined as a function of temperature. From 300 K down to 55 K, the shear modulus (G) of the HEA changes by only 8%, increasing from 80 to 86 GPa. Moreover, this temperature dependence is weaker than that of FCC Ni, whose G increases by 12% (81–91 GPa). Therefore, the uncharacteristic temperature-dependence of the strength of the HEA ismore » not due to the temperature dependence of its shear modulus.« less

Hooke's Law and the Stiffness of a Plastic Spoon

NASA Astrophysics Data System (ADS)

Pestka, Kenneth A.; Warren, Cori

2012-11-01

The study of elastic properties of solids is essential to both physics and engineering. Finding simple, easy-to-visualize examples to demonstrate these concepts is often difficult. In a previous article written by one of us (KAPII), a simple method for determining Youngs modulus using marshmallows was given. In this article we will illustrate another method to explore elastic properties of everyday materials. This experiment uses a common plastic spoon exposed to a transverse force in order to determine the stiffness constant, yield point, and rupture point of the plastic spoon. In addition, much like the "Youngs Modulus of a Marshmallow" activity, this experiment visually demonstrates Hooke's law, is fun and easy to perform, and leaves a lasting impression on the students.

Elastic, mechanical, and thermodynamic properties of Bi-Sb binaries: Effect of spin-orbit coupling

NASA Astrophysics Data System (ADS)

Singh, Sobhit; Valencia-Jaime, Irais; Pavlic, Olivia; Romero, Aldo H.

2018-02-01

Using first-principles calculations, we systematically study the elastic stiffness constants, mechanical properties, elastic wave velocities, Debye temperature, melting temperature, and specific heat of several thermodynamically stable crystal structures of BixSb1 -x (0

Effect of structural evolution on mechanical properties of ZrO2 coated Ti-6Al-7Nb-biomedical application

NASA Astrophysics Data System (ADS)

Zalnezhad, E.

2016-05-01

Zirconia (ZrO2) nanotube arrays were fabricated by anodizing pure zirconium (Zr) coated Ti-6Al-7Nb in fluoride/glycerol electrolyte at a constant potential of 60 V for different times. Zr was deposited atop Ti-6Al-7Nb via a physical vapor deposition magnetron sputtering (PVDMS) technique. Structural investigations of coating were performed utilizing X-ray diffraction (XRD) analysis. Field emission scanning electron microscopy (FESEM) and atomic force microscopy (AFM) were used to characterize the morphology and microstructure of coatings. Unannealed ZrO2 nanotube arrays were amorphous. Monoclinic and tetragonal ZrO2 appeared when the coated substrates were heat treated at 450 °C and 650 °C, while monoclinic ZrO2 was found at 850 °C and 900 °C. Mechanical properties, including nanohardness and modulus of elasticity, were evaluated at different annealing temperatures using a nanoindentation test. The nanoindentation results show that the nanohardness and modulus of elasticity for Ti-6AL-7Nb increased by annealing ZrO2 coated substrate at 450 °C. The nanohardness and modulus of elasticity for coated substrate decreased with annealing temperatures of 650, 850, and 900 °C. At an annealing temperature of 900 °C, cracks in the ZrO2 thin film coating occurred. The highest nanohardness and elastic modulus values of 6.34 and 218 GPa were achieved at an annealing temperature of 450 °C.

An overview of self-consistent methods for fiber-reinforced composites

NASA Technical Reports Server (NTRS)

Gramoll, Kurt C.; Freed, Alan D.; Walker, Kevin P.

1991-01-01

The Walker et al. (1989) self-consistent method to predict both the elastic and the inelastic effective material properties of composites is examined and compared with the results of other self-consistent and elastically based solutions. The elastic part of their method is shown to be identical to other self-consistent methods for non-dilute reinforced composite materials; they are the Hill (1965), Budiansky (1965), and Nemat-Nasser et al. (1982) derivations. A simplified form of the non-dilute self-consistent method is also derived. The predicted, elastic, effective material properties for fiber reinforced material using the Walker method was found to deviate from the elasticity solution for the v sub 31, K sub 12, and mu sub 31 material properties (fiber is in the 3 direction) especially at the larger volume fractions. Also, the prediction for the transverse shear modulus, mu sub 12, exceeds one of the accepted Hashin bounds. Only the longitudinal elastic modulus E sub 33 agrees with the elasticity solution. The differences between the Walker and the elasticity solutions are primarily due to the assumption used in the derivation of the self-consistent method, i.e., the strain fields in the inclusions and the matrix are assumed to remain constant, which is not a correct assumption for a high concentration of inclusions.

Elasticity of Calcium-Alkaline Amphiboles: Revised Properties for Crustal Seismic Models

NASA Astrophysics Data System (ADS)

Straughan, K. B.; Castle, N. R.; Brown, J.

2009-12-01

Amphiboles are dominant mineral constituents of both the oceanic and continental crust. Efforts to model crustal seismic structure and anisotropy have been limited by sparse and uncertain data for the elasticity of common rock-forming amphiboles. A single paper from 1961 reports properties of two “hornblendes” of unreported composition. We have undertaken a study of the calcium-alkaline amphiboles (minerals in this range include hornblende, tremolite, edenite, pargasite, tschermaktite and others) to explore elastic properties as a function of composition. Velocities as a function of propagation direction were measured using Impulsively Stimulated Light Scattering. All thirteen monoclinic elastic constants were determined for nine amphiboles spanning this common rock-forming compositional space. Amphiboles exhibit a wide range of elemental compositions and site occupancies. Measured trends of elastic constants with composition cannot be reduced to a single variable. Broad correlations are apparent in both (Mg+Fe) and Al concentrations. Among these samples, the isotropic average bulk modulus ranges from 85 to 98 GPa and the shear modulus ranges from 51 to 62. Poisson’s ratio varies from .23 to .27. The compressional velocity anisotropy (fast direction along the c axis and slow direction along the a-axis) varies with composition from 23% to 33%. Velocities along the c-axis are as fast as 9.0 km/s and along the a-axis are as slow as 5.8 km/s. These results exhibit far greater anisotropy and higher velocities than previously assumed based on the earlier data.

Electronic structure, elasticity, bonding features and mechanical behaviour of zinc intermetallics: A DFT study

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

Fatima, Bushra, E-mail: bushrafatima25@gmail.com; Acharya, Nikita; Sanyal, Sankar P.

2016-05-06

The structural stability, electronic structure, elastic and mechanical properties of TiZn and ZrZn intermetallics have been studied using ab-initio full potential linearized augmented plane wave (FP-LAPW) method within generalized gradient approximation for exchange and correlation potentials. The various structural parameters, such as lattice constant (a{sub 0}), bulk modulus (B), and its pressure derivative (B’) are analysed and compared. The investigation of elastic constants affirm that both TiZn and ZrZn are elastically stable in CsCl (B{sub 2} phase) structure. The electronic structures have been analysed quantitatively from the band structure which reveals the metallic nature of these compounds. To better illustratemore » the nature of bonding and charge transfer, we have also studied the Fermi surfaces. The three well known criterion of ductility namely Pugh’s rule, Cauchy’s pressure and Frantsevich rule elucidate the ductile nature of these compounds.« less

Sub-Micrometer Zeolite Films on Gold-Coated Silicon Wafers with Single-Crystal-Like Dielectric Constant and Elastic Modulus

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

Tiriolo, Raffaele; Rangnekar, Neel; Zhang, Han

A low-temperature synthesis coupled with mild activation produces zeolite films exhibiting low dielectric constant (low-k) matching the theoretically predicted and experimentally measured values for single crystals. This synthesis and activation method allows for the fabrication of a device consisting of a b-oriented film of the pure-silica zeolite MFI (silicalite-1) supported on a gold-coated silicon wafer. The zeolite seeds are assembled by a manual assembly process and subjected to optimized secondary growth conditions that do not cause corrosion of the gold underlayer, while strongly promoting in-plane growth. The traditional calcination process is replaced with a non-thermal photochemical activation to ensure preservationmore » of an intact gold layer. The dielectric constant (k), obtained through measurement of electrical capacitance in a metal-insulator-metal configuration, highlights the ultralow k approximate to 1.7 of the synthetized films, which is among the lowest values reported for an MFI film. There is large improvement in elastic modulus of the film (E approximate to 54 GPa) over previous reports, potentially allowing for integration into silicon wafer processing technology.« less

First-principles calculation on the thermodynamic and elastic properties of precipitations in Al-Cu alloys

NASA Astrophysics Data System (ADS)

Sun, Dongqiang; Wang, Yongxin; Zhang, Xinyi; Zhang, Minyu; Niu, Yanfei

2016-12-01

First-principles calculations based on density functional theory was used to investigate the structural, thermodynamic and elastic properties of precipitations, θ″, θ‧ and θ, in Al-Cu alloys. The values of lattice constants accord with experimental results well. The structural stability of θ is the best, followed by θ‧ and θ″. In addition, due to the highest bulk modulus, shear modulus and Young's modulus, θ possesses the best reinforcement effect in precipitation hardening process considered only from mechanical properties of perfect crystal. According to the values of B/G, Poisson's ratio and C11-C12, θ‧ has the worst ductility, while θ″ has the best ductility, the ductility of θ is in the middle. The ideal tensile strength of θ″, θ‧ and θ calculated along [100] and [001] directions are 20.87 GPa, 23.11 GPa and 24.70 GPa respectively. The analysis of electronic structure suggests that three precipitations all exhibit metallic character, and number of bonding electrons and bonding strength are the nature of different thermodynamic and elastic properties for θ″, θ‧ and θ.

The cancellous bone multiscale morphology-elasticity relationship.

PubMed

Agić, Ante; Nikolić, Vasilije; Mijović, Budimir

2006-06-01

The cancellous bone effective properties relations are analysed on multiscale across two aspects; properties of representative volume element on micro scale and statistical measure of trabecular trajectory orientation on mesoscale. Anisotropy of the microstructure is described across fabric tensor measure with trajectory orientation tensor as bridging scale connection. The scatter measured data (elastic modulus, trajectory orientation, apparent density) from compression test are fitted by stochastic interpolation procedure. The engineering constants of the elasticity tensor are estimated by last square fitt procedure in multidimensional space by Nelder-Mead simplex. The multiaxial failure surface in strain space is constructed and interpolated by modified super-ellipsoid.

Two Novel C3N4 Phases: Structural, Mechanical and Electronic Properties

PubMed Central

Fan, Qingyang; Chai, Changchun; Wei, Qun; Yang, Yintang

2016-01-01

We systematically studied the physical properties of a novel superhard (t-C3N4) and a novel hard (m-C3N4) C3N4 allotrope. Detailed theoretical studies of the structural properties, elastic properties, density of states, and mechanical properties of these two C3N4 phases were carried out using first-principles calculations. The calculated elastic constants and the hardness revealed that t-C3N4 is ultra-incompressible and superhard, with a high bulk modulus of 375 GPa and a high hardness of 80 GPa. m-C3N4 and t-C3N4 both exhibit large anisotropy with respect to Poisson’s ratio, shear modulus, and Young’s modulus. Moreover, m-C3N4 is a quasi-direct-bandgap semiconductor, with a band gap of 4.522 eV, and t-C3N4 is also a quasi-direct-band-gap semiconductor, with a band gap of 4.210 eV, with the HSE06 functional. PMID:28773550

Prediction of Material Properties of Nanostructured Polymer Composites Using Atomistic Simulations

NASA Technical Reports Server (NTRS)

Hinkley, J.A.; Clancy, T.C.; Frankland, S.J.V.

2009-01-01

Atomistic models of epoxy polymers were built in order to assess the effect of structure at the nanometer scale on the resulting bulk properties such as elastic modulus and thermal conductivity. Atomistic models of both bulk polymer and carbon nanotube polymer composites were built. For the bulk models, the effect of moisture content and temperature on the resulting elastic constants was calculated. A relatively consistent decrease in modulus was seen with increasing temperature. The dependence of modulus on moisture content was less consistent. This behavior was seen for two different epoxy systems, one containing a difunctional epoxy molecule and the other a tetrafunctional epoxy molecule. Both epoxy structures were crosslinked with diamine curing agents. Multifunctional properties were calculated with the nanocomposite models. Molecular dynamics simulation was used to estimate the interfacial thermal (Kapitza) resistance between the carbon nanotube and the surrounding epoxy matrix. These estimated values were used in a multiscale model in order to predict the thermal conductivity of a nanocomposite as a function of the nanometer scaled molecular structure.

A new analytical method for estimating lumped parameter constants of linear viscoelastic models from strain rate tests

NASA Astrophysics Data System (ADS)

Mattei, G.; Ahluwalia, A.

2018-04-01

We introduce a new function, the apparent elastic modulus strain-rate spectrum, E_{app} ( \\dot{ɛ} ), for the derivation of lumped parameter constants for Generalized Maxwell (GM) linear viscoelastic models from stress-strain data obtained at various compressive strain rates ( \\dot{ɛ}). The E_{app} ( \\dot{ɛ} ) function was derived using the tangent modulus function obtained from the GM model stress-strain response to a constant \\dot{ɛ} input. Material viscoelastic parameters can be rapidly derived by fitting experimental E_{app} data obtained at different strain rates to the E_{app} ( \\dot{ɛ} ) function. This single-curve fitting returns similar viscoelastic constants as the original epsilon dot method based on a multi-curve global fitting procedure with shared parameters. Its low computational cost permits quick and robust identification of viscoelastic constants even when a large number of strain rates or replicates per strain rate are considered. This method is particularly suited for the analysis of bulk compression and nano-indentation data of soft (bio)materials.

Elastic properties of graphene: A pseudo-beam model with modified internal bending moment and its application

NASA Astrophysics Data System (ADS)

Xia, Z. M.; Wang, C. G.; Tan, H. F.

2018-04-01

A pseudo-beam model with modified internal bending moment is presented to predict elastic properties of graphene, including the Young's modulus and Poisson's ratio. In order to overcome a drawback in existing molecular structural mechanics models, which only account for pure bending (constant bending moment), the presented model accounts for linear bending moments deduced from the balance equations. Based on this pseudo-beam model, an analytical prediction is accomplished to predict the Young's modulus and Poisson's ratio of graphene based on the equation of the strain energies by using Castigliano second theorem. Then, the elastic properties of graphene are calculated compared with results available in literature, which verifies the feasibility of the pseudo-beam model. Finally, the pseudo-beam model is utilized to study the twisting wrinkling characteristics of annular graphene. Due to modifications of the internal bending moment, the wrinkling behaviors of graphene sheet are predicted accurately. The obtained results show that the pseudo-beam model has a good ability to predict the elastic properties of graphene accurately, especially the out-of-plane deformation behavior.

Nonlinear Visco-Elastic Response of Composites via Micro-Mechanical Models

NASA Technical Reports Server (NTRS)

Gates, Thomas S.; Sridharan, Srinivasan

2005-01-01

Micro-mechanical models for a study of nonlinear visco-elastic response of composite laminae are developed and their performance compared. A single integral constitutive law proposed by Schapery and subsequently generalized to multi-axial states of stress is utilized in the study for the matrix material. This is used in conjunction with a computationally facile scheme in which hereditary strains are computed using a recursive relation suggested by Henriksen. Composite response is studied using two competing micro-models, viz. a simplified Square Cell Model (SSCM) and a Finite Element based self-consistent Cylindrical Model (FECM). The algorithm is developed assuming that the material response computations are carried out in a module attached to a general purpose finite element program used for composite structural analysis. It is shown that the SSCM as used in investigations of material nonlinearity can involve significant errors in the prediction of transverse Young's modulus and shear modulus. The errors in the elastic strains thus predicted are of the same order of magnitude as the creep strains accruing due to visco-elasticity. The FECM on the other hand does appear to perform better both in the prediction of elastic constants and the study of creep response.

Ab Initio Study of the Electronic Structure, Elastic Properties, Magnetic Feature and Thermodynamic Properties of the Ba2NiMoO6 Material

NASA Astrophysics Data System (ADS)

Deluque Toro, C. E.; Mosquera Polo, A. S.; Gil Rebaza, A. V.; Landínez Téllez, D. A.; Roa-Rojas, J.

2018-04-01

We report first-principles calculations of the elastic properties, electronic structure and magnetic behavior performed over the Ba2NiMoO6 double perovskite. Calculations are carried out through the full-potential linear augmented plane-wave method within the framework of the Density Functional Theory (DFT) with exchange and correlation effects in the Generalized Gradient and Local Density Approximations, including spin polarization. The elastic properties calculated are bulk modulus (B), the elastic constants (C 11, C 12 and C 44), the Zener anisotropy factor (A), the isotropic shear modulus (G), the Young modulus (Y) and the Poisson ratio (υ). Structural parameters, total energies and cohesive properties of the perovskite are studied by means of minimization of internal parameters with the Murnaghan equation, where the structural parameters are in good agreement with experimental data. Furthermore, we have explored different antiferromagnetic configurations in order to describe the magnetic ground state of this compound. The pressure and temperature dependence of specific heat, thermal expansion coefficient, Debye temperature and Grüneisen parameter were calculated by DFT from the state equation using the quasi-harmonic model of Debye. A specific heat behavior C V ≈ C P was found at temperatures below T = 400 K, with Dulong-Petit limit values, which is higher than those, reported for simple perovskites.

Modeling of Failure Mechanisms in Composites With Z-Pins-Damage Validation of Z-Pin Reinforced Co-Cured Composite Laminates

DTIC Science & Technology

2011-04-01

there it is a computer implementation of the method just introduced. It uses Scilab ® programming language, and the Young modulus is calculated as final...laminate without Z-pins, its thickness, lamina stacking sequence and lamina’s engineering elastic constants, the second Scilab ® code can be used to find...EL thickness, the second Scilab ® code is employed once again; this time, though, a new Young’s modulus estimate would be produced. On the other hand

Evaluation of mechanical and transport properties of Zr2CoSi Heusler alloy

NASA Astrophysics Data System (ADS)

Yousuf, Saleem; Khandy, S. A.; Bhat, T. M.; Gupta, D. C.

2017-05-01

Systematic investigation of mechanical and transport properties of Zr2CoSi within the density functional theory have been analysed. From the elastic constants, the shear modulus, Young's modulus, Poisson's ratio, we conclude the ductile nature of alloy. Thermoelectric properties show that Zr2CoSi as an n-type thermoelectric material with a higher increase in Seebeck coefficient with temperature. Further the power factor analysis confirms the heavily doping of the alloy fruitful for increase in thermoelectric performance and its use for the future thermoelectric spin generators.

Elastic modulus of phases in Ti–Mo alloys

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

Zhang, Wei-dong; Liu, Yong, E-mail: yonliu11@aliyun.com; Wu, Hong

2015-08-15

In this work, a series of binary Ti–Mo alloys with the Mo contents ranging from 3.2 to 12 at.% were prepared using non-consumable arc melting. The microstructures were investigated by X-ray diffraction and transmission electron microscope, and the elastic modulus was evaluated by nanoindentation testing technique. The evolution of the volume fractions of ω phase was investigated using X-ray photoelectron spectroscopy. The results indicated that the phase constitution and elastic modulus of the Ti–Mo alloys are sensitive to the Mo content. Ti–3.2Mo and Ti–8Mo alloys containing only α and β phases, respectively, have a low elastic modulus. In contrast, Ti–4.5Mo,more » Ti–6Mo, Ti–7Mo alloys, with different contents of ω phase, have a high elastic modulus. A simple micromechanical model was used to calculate the elastic modulus of ω phase (E{sub ω}), which was determined to be 174.354 GPa. - Highlights: • Ti–Mo alloys with the Mo contents ranging from 3.2 to 12 at.% were investigated. • XPS was used to investigate the volume fractions of ω phase. • The elastic modulus of Ti–Mo alloys is sensitive to the Mo content. • The elastic modulus of ω phase was determined to be 174.354 GPa.« less

Quantitative evaluation of the piezoelectric response of unpoled ferroelectric ceramics from elastic and dielectric measurements: Tetragonal BaTiO3

NASA Astrophysics Data System (ADS)

Cordero, F.

2018-03-01

A method is proposed for evaluating the potential piezoelectric response, that a ferroelectric material would exhibit after full poling, from elastic and dielectric measurements of the unpoled ceramic material. The method is based on the observation that the softening in a ferroelectric phase with respect to the paraelectric phase is of piezoelectric origin, and is tested on BaTiO3. The angular averages of the piezoelectric softening in unpoled ceramics are calculated for ferroelectric phases of different symmetries. The expression of the orientational average with the piezoelectric and dielectric constants of single crystal tetragonal BaTiO3 from the literature reproduces well the softening of the Young's modulus of unpoled ceramic BaTiO3, after a correction for the porosity. The agreement is good in the temperature region sufficiently far from the Curie temperature and from the transition to the orthorhombic phase, where the effect of fluctuations should be negligible, but deviations are found outside this region, and possible reasons for this are discussed. This validates the determination of the piezoelectric response by means of purely elastic measurements on unpoled samples. The method is indirect and, for quantitative assessments, requires the knowledge of the dielectric tensor. On the other hand, it does not require poling of the sample, and therefore is insensitive to inaccuracies from incomplete poling, and can even be used with materials that cannot be poled, for example, due to excessive electrical conductivity. While the proposed example of the Young's modulus of a ceramic provides an orientational average of all the single crystal piezoelectric constants, a Resonant Ultrasound Spectroscopy measurement of a single unpoled ceramic sample through the ferroelectric transition can in principle measure all the piezoelectric constants, together with the elastic ones.

Elastic Multi-scale Mechanisms: Computation and Biological Evolution.

PubMed

Diaz Ochoa, Juan G

2018-01-01

Explanations based on low-level interacting elements are valuable and powerful since they contribute to identify the key mechanisms of biological functions. However, many dynamic systems based on low-level interacting elements with unambiguous, finite, and complete information of initial states generate future states that cannot be predicted, implying an increase of complexity and open-ended evolution. Such systems are like Turing machines, that overlap with dynamical systems that cannot halt. We argue that organisms find halting conditions by distorting these mechanisms, creating conditions for a constant creativity that drives evolution. We introduce a modulus of elasticity to measure the changes in these mechanisms in response to changes in the computed environment. We test this concept in a population of predators and predated cells with chemotactic mechanisms and demonstrate how the selection of a given mechanism depends on the entire population. We finally explore this concept in different frameworks and postulate that the identification of predictive mechanisms is only successful with small elasticity modulus.

First principles study on the elastic and electronic properties of CdX (X = S, Se and Te)

NASA Astrophysics Data System (ADS)

Sharma, Sheetal; Verma, Ajay Singh; Sarkar, Bimal Kumar; Bhandari, Rajiv; Jindal, Vijay Kumar

2011-12-01

Wide band gap semiconductors are emerging as a potential candidate for optically active materials in blue green spectral region and operating at high power level and high temperature. CdX, X = S, Se and Te are wide band gap semiconductors having applications in optoelectronics devices. In this paper we investigated the elastic and electronic properties of Cadmium chalcogenide (cubic zinc-blende (ZB) structure) using standard Kohn-Sham self consistent density functional theory method (DFT) that uses non conserving pseudopotentials in fully nonlocal form within the generalized gradient approximation (GGA) for the exchange-correlation potential. The independent elastic constants, C11, C12 and C44, are calculated from direct computation of stresses generated by small strains. The shear modulus and Young's modulus are estimated for CdX. Using the GGA for the exchange correlation potential, the calculated direct fundamental band gap value is in very good agreement with the measured one.

Elasticity and Stability of Clathrate Hydrate: Role of Guest Molecule Motions.

PubMed

Jia, Jihui; Liang, Yunfeng; Tsuji, Takeshi; Murata, Sumihiko; Matsuoka, Toshifumi

2017-05-02

Molecular dynamic simulations were performed to determine the elastic constants of carbon dioxide (CO 2 ) and methane (CH 4 ) hydrates at one hundred pressure-temperature data points, respectively. The conditions represent marine sediments and permafrost zones where gas hydrates occur. The shear modulus and Young's modulus of the CO 2 hydrate increase anomalously with increasing temperature, whereas those of the CH 4 hydrate decrease regularly with increase in temperature. We ascribe this anomaly to the kinetic behavior of the linear CO 2 molecule, especially those in the small cages. The cavity space of the cage limits free rotational motion of the CO 2 molecule at low temperature. With increase in temperature, the CO 2 molecule can rotate easily, and enhance the stability and rigidity of the CO 2 hydrate. Our work provides a key database for the elastic properties of gas hydrates, and molecular insights into stability changes of CO 2 hydrate from high temperature of ~5 °C to low decomposition temperature of ~-150 °C.

The influence of anisotropy on the core structure of Shockley partial dislocations within FCC materials

NASA Astrophysics Data System (ADS)

Szajewski, B. A.; Hunter, A.; Luscher, D. J.; Beyerlein, I. J.

2018-01-01

Both theoretical and numerical models of dislocations often necessitate the assumption of elastic isotropy to retain analytical tractability in addition to reducing computational load. As dislocation based models evolve towards physically realistic material descriptions, the assumption of elastic isotropy becomes increasingly worthy of examination. We present an analytical dislocation model for calculating the full dissociated core structure of dislocations within anisotropic face centered cubic (FCC) crystals as a function of the degree of material elastic anisotropy, two misfit energy densities on the γ-surface ({γ }{{isf}}, {γ }{{usf}}) and the remaining elastic constants. Our solution is independent of any additional features of the γ-surface. Towards this pursuit, we first demonstrate that the dependence of the anisotropic elasticity tensor on the orientation of the dislocation line within the FCC crystalline lattice is small and may be reasonably neglected for typical materials. With this approximation, explicit analytic solutions for the anisotropic elasticity tensor {B} for both nominally edge and screw dislocations within an FCC crystalline lattice are devised, and employed towards defining a set of effective isotropic elastic constants which reproduce fully anisotropic results, however do not retain the bulk modulus. Conversely, Hill averaged elastic constants which both retain the bulk modulus and reasonably approximate the dislocation core structure are employed within subsequent numerical calculations. We examine a wide range of materials within this study, and the features of each partial dislocation core are sufficiently localized that application of discrete linear elasticity accurately describes the separation of each partial dislocation core. In addition, the local features (the partial dislocation core distribution) are well described by a Peierls-Nabarro dislocation model. We develop a model for the displacement profile which depends upon two disparate dislocation length scales which describe the core structure; (i) the equilibrium stacking fault width between two Shockley partial dislocations, R eq and (ii) the maximum slip gradient, χ, of each Shockley partial dislocation. We demonstrate excellent agreement between our own analytic predictions, numerical calculations, and R eq computed directly by both ab-initio and molecular statics methods found elsewhere within the literature. The results suggest that understanding of various plastic mechanisms, e.g., cross-slip and nucleation may be augmented with the inclusion of elastic anisotropy.

Vibrational and elastic properties of silicate spinels A2SiO4 (A = Mg, Fe, Ni, and Co)

NASA Astrophysics Data System (ADS)

Kushwaha, A. K.; Ma, C.-G.; Brik, M. G.; Akbudak, S.

2018-06-01

A six-parameter bond-bending force constant model is used to calculate the zone-center (Γ = 0) Raman and infrared phonon mode frequencies, elastic constants and related properties, the Debye temperatures, and sound velocities along high-symmetry directions for A2SiO4 (A = Mg, Fe, Ni, and Co) spinels. The main outcomes of the calculations are that the interactions between Si and O atoms (first-neighbor interaction) are stronger than those between A and Oatoms (A = Mg, Fe, Ni, and Co) (second-neighbor interaction). The elastic constants C11, C12, and C44 decrease in the order Mg > Fe > Ni > Co. The calculated bulk modulus, Poisson's ratio, and anisotropy decrease in the sequence Fe2SiO4 → Ni2SiO4 → Co2SiO4 → Mg2SiO4. On comparison, we find overall good agreement with the available experimental and previously calculated data.

A parametric analysis of waves propagating in a porous solid saturated by a three-phase fluid.

PubMed

Santos, Juan E; Savioli, Gabriela B

2015-11-01

This paper presents an analysis of a model for the propagation of waves in a poroelastic solid saturated by a three-phase viscous, compressible fluid. The constitutive relations and the equations of motion are stated first. Then a plane wave analysis determines the phase velocities and attenuation coefficients of the four compressional waves and one shear wave that propagate in this type of medium. A procedure to compute the elastic constants in the constitutive relations is defined next. Assuming the knowledge of the shear modulus of the dry matrix, the other elastic constants in the stress-strain relations are determined by employing ideal gedanken experiments generalizing those of Biot's theory for single-phase fluids. These experiments yield expressions for the elastic constants in terms of the properties of the individual solid and fluids phases. Finally the phase velocities and attenuation coefficients of all waves are computed for a sample of Berea sandstone saturated by oil, gas, and water.

A novel pressure variation study on electronic structure, mechanical stability and thermodynamic properties of potassium based fluoroperovskite

NASA Astrophysics Data System (ADS)

Erum, Nazia; Azhar Iqbal, Muhammad

2017-09-01

The effect of pressure variation on stability, structural parameters, elastic constants, mechanical, electronic and thermodynamic properties of cubic SrKF3 fluoroperovskite have been investigated by using the full-potential linearized augmented plane wave (FP-LAPW) method combined with Quasi-harmonic Debye model in which the phonon effects are considered. The calculated lattice parameters show a prominent decrease in lattice constant and bonds length with the increase in pressure. The application of pressure from 0 to 25 GPa reveals a predominant characteristic associated with widening of bandgap with GGA and GGA plus Tran-Blaha modified Becke-Johnson (TB-mBJ) potential. The influence of pressure on elastic constants and their related mechanical parameters have been discussed in detail. Apart of linear dependence of elastic coefficients, transition from brittle to ductile behavior is also observed at elevated pressure ranges. We have successfully computed variation of lattice constant, volume expansion, bulk modulus, Debye temperature and specific heat capacities at pressure and temperature in the range of 0-25 GPa and 0-600 K.

Apparent elastic modulus and hysteresis of skeletal muscle cells throughout differentiation

NASA Technical Reports Server (NTRS)

Collinsworth, Amy M.; Zhang, Sarah; Kraus, William E.; Truskey, George A.

2002-01-01

The effect of differentiation on the transverse mechanical properties of mammalian myocytes was determined by using atomic force microscopy. The apparent elastic modulus increased from 11.5 +/- 1.3 kPa for undifferentiated myoblasts to 45.3 +/- 4.0 kPa after 8 days of differentiation (P < 0.05). The relative contribution of viscosity, as determined from the normalized hysteresis area, ranged from 0.13 +/- 0.02 to 0.21 +/- 0.03 and did not change throughout differentiation. Myosin expression correlated with the apparent elastic modulus, but neither myosin nor beta-tubulin were associated with hysteresis. Microtubules did not affect mechanical properties because treatment with colchicine did not alter the apparent elastic modulus or hysteresis. Treatment with cytochalasin D or 2,3-butanedione 2-monoxime led to a significant reduction in the apparent elastic modulus but no change in hysteresis. In summary, skeletal muscle cells exhibited viscoelastic behavior that changed during differentiation, yielding an increase in the transverse elastic modulus. Major contributors to changes in the transverse elastic modulus during differentiation were actin and myosin.

Yielding in a strongly aggregated colloidal gel: 2D simulations and theory

NASA Astrophysics Data System (ADS)

Roy, Saikat; Tirumkudulu, Mahesh

2015-11-01

We investigated the micro-structural details and the mechanical response under uniaxial compression of the strongly aggregating gel starting from low to high packing fraction.The numerical simulations account for short-range inter-particle attractions, normal and tangential deformation at particle contacts,sliding and rolling friction, and preparation history. It is observed that in the absence of rolling resistance(RR),the average coordination number varies only slightly with compaction whereas it is significant in the presence of RR. The particle contact distribution is isotropic throughout the consolidation process. In both cases, the yield strain is constant with the volume fraction. The modulus values are very similar at different attraction, and with and without RR implying that the elastic modulus does not scale with attraction.The modulus was found to be a weak function of the preparation history. The increase in yield stress with volume fraction is a consequence of the increased elastic modulus of the network. However, the yield stress scales similarly both with and without RR. The power law exponent of 5.4 is in good agreement with previous simulation results. A micromechanical theory is also proposed to describe the stress versus strain relation for the gelled network.

Elastic Properties across the y→α Volume Collapse in Cerium versus Pressure and Temperature

DOE PAGES

Lipp, M. J.; Jenei, Zs.; Cynn, H.; ...

2017-10-31

Here, the longitudinal and transverse sound speeds, c L and c T, of polycrystalline cerium were measured isothermally vs pressure up to the critical temperature across the iso-structural γ-α volume collapse (VC) phase transition. We deduce values for the adiabatic bulk modulus BS, the shear modulus G = ρc T 2, the Poisson’s ratio ν and the Debye temperature, θ D(p). We find that the elastic constant C 12 is solely responsible for the decrease of B S with pressure towards the VC at RT. With increasing temperature, the lattice contribution ΔS vib(γ→α) to the total entropy change across themore » VC decreases more rapidly to zero than the total entropy itself suggesting that another mechanism, possibly disorder, assists in stabilizing the γ-phase entropically against the α-phase. Also, with increasing temperature, the Poisson’s ratio becomes negative near the VC transition, meaning that cerium metal takes on auxetic characteristics over a small pressure range. At the critical point the Poisson’s ratio ought to be -1, since the isothermal bulk modulus vanishes and the shear modulus remains nonzero.« less

Elastic Properties across the y→α Volume Collapse in Cerium versus Pressure and Temperature

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

Lipp, M. J.; Jenei, Zs.; Cynn, H.

Here, the longitudinal and transverse sound speeds, c L and c T, of polycrystalline cerium were measured isothermally vs pressure up to the critical temperature across the iso-structural γ-α volume collapse (VC) phase transition. We deduce values for the adiabatic bulk modulus BS, the shear modulus G = ρc T 2, the Poisson’s ratio ν and the Debye temperature, θ D(p). We find that the elastic constant C 12 is solely responsible for the decrease of B S with pressure towards the VC at RT. With increasing temperature, the lattice contribution ΔS vib(γ→α) to the total entropy change across themore » VC decreases more rapidly to zero than the total entropy itself suggesting that another mechanism, possibly disorder, assists in stabilizing the γ-phase entropically against the α-phase. Also, with increasing temperature, the Poisson’s ratio becomes negative near the VC transition, meaning that cerium metal takes on auxetic characteristics over a small pressure range. At the critical point the Poisson’s ratio ought to be -1, since the isothermal bulk modulus vanishes and the shear modulus remains nonzero.« less

First-principles study on the structural, elastic and electronic properties of Ti4N3 and Ti6N5 under high pressure

NASA Astrophysics Data System (ADS)

Yang, Ruike; Chai, Bao; Zhu, Chuanshuai; Wei, Qun; Du, Zheng

2017-12-01

The structural, elastic and electronic properties of Ti4N3 and Ti6N5 have been systematically studied by first-principles calculations based on density functional theory (DFT) with generalized gradient approximation (GGA) and local density approximation (LDA). Basic physical properties for Ti4N3 and Ti6N5, such as the lattice constants, the bulk modulus, shear modulus, and elastic constants are calculated. The results show that Ti4N3 and Ti6N5 are mechanically stable under ambient pressure. The phonon dispersion spectra are researched throughout the Brillouin zone via the linear response approach as implemented in the CASTEP code, which indicate the optimized structures are stable dynamically. The Young’s modulus E and Poisson’s ratios ν are also determined within the framework of the Voigt-Reuss-Hill approximation. The analyses show that Ti4N3 is more ductile than Ti6N5 at the same pressure and ductility increases as the pressure increases. Moreover, the anisotropies of the Ti4N3 and Ti6N5 are discussed by the Young’s modulus at different directions, and the results indicate that the anisotropy of the two Ti-N compounds is obvious. The total density of states (TDOS) and partial density of states (PDOS) show that the TDOS of TiN, Ti4N3 and Ti6N5 originate mainly from Ti “d” and N “p” states. The results show that Ti4N3 and Ti6N5 present semimetal character. Pressure makes the level range of DOS significantly extended, for TiN, Ti4N3 and Ti6N5. The TDOS decreases with the pressure rise, at Fermi level.

Effects of ablation depth and repair time on the corneal elastic modulus after laser in situ keratomileusis.

PubMed

Wang, Xiaojun; Li, Xiaona; Chen, Weiyi; He, Rui; Gao, Zhipeng; Feng, Pengfei

2017-01-17

The biomechanical properties of the cornea should be taken into account in the refractive procedure in order to perform refractive surgery more accurately. The effects of the ablation depth and repair time on the elastic modulus of the rabbit cornea after laser in situ keratomileusis (LASIK) are still unclear. In this study, LASIK was performed on New Zealand rabbits with different ablation depth (only typical LASIK flaps were created; residual stroma bed was 50 or 30% of the whole cornea thickness respectively). The animals without any treatment were served as normal controls. The corneal thickness was measured by ultrasonic pachymetry before animals were humanly killed after 7 or 28 days post-operatively. The corneal elastic modulus was measured by uniaxial tensile testing. A mathematical procedure considering the actual geometrics of the cornea was created to analyze the corneal elastic modulus. There were no obvious differences among all groups in the elastic modulus on after 7 days post-operatively. However, after 28th days post-operatively, there was a significant increase in the elastic modulus with 50 and 30% residual stroma bed; only the elastic modulus of the cornea with 30% residual stroma bed was significantly higher than that of 7 days. Changes in elastic modulus after LASIK suggest that this biomechanical effect may correlate with the ablation depth and repair time.

Structural, electronic and elastic properties of heavy fermion YbRh2 Laves phase compound

NASA Astrophysics Data System (ADS)

Pawar, Harsha; Shugani, Mani; Aynyas, Mahendra; Sanyal, Sankar P.

2018-05-01

The structural, electronic and elastic properties of YbRh2 Laves phase intermetallic compound which crystallize in cubic (MgCu2-type) structure have been investigated using ab-initio full potential linearized augmented plane wave (FP- LAPW) method with LDA and LDA+U approximation. The calculated ground state properties such as lattice parameter (a0), bulk modulus (B) and its pressure derivative (B') are in good agreement with available experimental and theoretical data. The electronic properties are analyzed from band structures and density of states. Elastic constants are predicted first time for this compound which obeys the stability criteria for cubic system.

Hydrostatic pressure effects on the structural, elastic and thermodynamic properties of the complex transition metal hydrides A2OsH6 (A = Mg, Ca, Sr and Ba)

NASA Astrophysics Data System (ADS)

Souadia, Z.; Bouhemadou, A.; Boudrifa, O.; Bin-Omran, S.; Khenata, R.; Al-Douri, Y.

2017-10-01

We report a systematic first-principles density functional theory study on the pressure dependence of the structural parameters, elastic constants and related properties and thermodynamic properties of the complex transition metal hydrides Mg2OsH6, Ca2OsH6, Sr2OsH6 and Ba2OsH6. The calculated structural parameters are in excellent agreement with the existing data in the scientific literature. The single-crystal elastic constants and related properties were predicted using the stress-strain method. The elastic moduli of the polycrystalline aggregates were evaluated via the Voigt-Reuss-Hill approach. The dependences of the lattice parameter, bulk modulus, volume thermal expansion coefficient, isobaric and isochoric heat capacity and Debye temperature on the pressure and temperature, ranging from 0 to 15 GPa and from 0 to 1000 K, respectively, were investigated using the quasi-harmonic Debye model in combination with first-principles calculations.

First-principles study of the structural, elastic, vibrational, thermodynamic and electronic properties of the Mo2B intermetallic under pressure

NASA Astrophysics Data System (ADS)

Escamilla, R.; Carvajal, E.; Cruz-Irisson, M.; Romero, M.; Gómez, R.; Marquina, V.; Galván, D. H.; Durán, A.

2016-12-01

The structural, elastic, vibrational, thermodynamic and electronic properties of the Mo2B intermetallic under pressure are assessed using first-principles calculations based on the generalized gradient approximation (GGA) proposed by Perdew-Wang (PW91). Our results show that the calculated structural parameters at a pressure of zero GPa are in good agreement with the available experimental data. The effect of high pressures on the lattice constants shows that the compression along the c-axis and along the a-axis are similar. The elastic constants were calculated using the static finite strain technique, and the bulk shear moduli are derived from the ideal polycrystalline aggregate. We find that the elastic constants, elastic modulus and hardness monotonically increase as a function of pressure; consequently, the structure is dynamically stable and tends from brittle to ductile behavior under pressure. The Debye temperature θD increases and the so-called Gru¨ neisen constant γ decreases due to stiffening of the crystal structure. The phonon dispersion curves were obtained using the direct method. Additionally, the internal energy (ΔE), the Helmholtz free energy (ΔF), the entropy (S) and the lattice contribution to the heat capacity Cv were calculated and analyzed with the help of the phonon dispersion curves. The N(EF) and the electron transfer between the B and Mo atoms increase as a function of pressure.

Structural, electronic, elastic, and thermal properties of CaNiH3 perovskite obtained from first-principles calculations

NASA Astrophysics Data System (ADS)

Benlamari, S.; Bendjeddou, H.; Boulechfar, R.; Amara Korba, S.; Meradji, H.; Ahmed, R.; Ghemid, S.; Khenata, R.; Omran, S. Bin

2018-03-01

A theoretical study of the structural, elastic, electronic, mechanical, and thermal properties of the perovskite-type hydride CaNiH3 is presented. This study is carried out via first-principles full potential (FP) linearized augmented plane wave plus local orbital (LAPW+lo) method designed within the density functional theory (DFT). To treat the exchange–correlation energy/potential for the total energy calculations, the local density approximation (LDA) of Perdew–Wang (PW) and the generalized gradient approximation (GGA) of Perdew–Burke–Ernzerhof (PBE) are used. The three independent elastic constants (C 11, C 12, and C 44) are calculated from the direct computation of the stresses generated by small strains. Besides, we report the variation of the elastic constants as a function of pressure as well. From the calculated elastic constants, the mechanical character of CaNiH3 is predicted. Pertaining to the thermal properties, the Debye temperature is estimated from the average sound velocity. To further comprehend this compound, the quasi-harmonic Debye model is used to analyze the thermal properties. From the calculations, we find that the obtained results of the lattice constant (a 0), bulk modulus (B 0), and its pressure derivative ({B}0^{\\prime }) are in good agreement with the available theoretical as well as experimental results. Similarly, the obtained electronic band structure demonstrates the metallic character of this perovskite-type hydride.

Change and anisotropy of elastic modulus in sheet metals due to plastic deformation

NASA Astrophysics Data System (ADS)

Ishitsuka, Yuki; Arikawa, Shuichi; Yoneyama, Satoru

2015-03-01

In this study, the effect of the plastic deformation on the microscopic structure and the anisotropy of the elastic modulus in the cold-rolled steel sheet (SPCC) is investigated. Various uniaxial plastic strains (0%, 2.5%, 5%, 7.5%, and 10%) are applied to the annealed SPCC plates, then, the specimens for the tensile tests are cut out from them. The elastic moduli in the longitudinal direction and the transverse direction to the direction that are pre-strained are measured by the tensile tests. Cyclic tests are performed to investigate the effects of the internal friction caused by the movable dislocations in the elastic deformation. Also, the movable dislocations are quantified by the boundary tracking for TEM micrographs. In addition, the behaviors of the change of the elastic modulus in the solutionized and thermal aged aluminum alloy (A5052) are measured to investigate the effect on the movable dislocations with the amount of the depositions. As a result in SPCC, the elastic moduli of the 0° and 90° directions decrease more than 10% as 10% prestrain applied. On the other hand, the elastic modulus shows the recovery behavior after the strain aging and the annealing. The movable dislocation and the internal friction show a tendency to increase as the plastic strain increases. The marked anisotropy is not observed in the elastic modulus and the internal friction. The elastic modulus in A5052 with many and few depositions decreases similarly by the plastic deformation. From the above, the movable dislocations affect the elastic modulus strongly without depending on the deposition amount. Moreover, the elastic modulus recovers after the plastic deformation by reducing the effects of them with the strain aging and the heat treatment.

Multiphoton photochemical crosslinking-based fabrication of protein micropatterns with controllable mechanical properties for single cell traction force measurements

NASA Astrophysics Data System (ADS)

Tong, Ming Hui; Huang, Nan; Zhang, Wei; Zhou, Zhuo Long; Ngan, Alfonso Hing Wan; Du, Yanan; Chan, Barbara Pui

2016-01-01

Engineering 3D microstructures with predetermined properties is critical for stem cell niche studies. We have developed a multiphoton femtosecond laser-based 3D printing platform, which generates complex protein microstructures in minutes. Here, we used the platform to test a series of fabrication and reagent parameters in precisely controlling the mechanical properties of protein micropillars. Atomic force microscopy was utilized to measure the reduced elastic modulus of the micropillars, and transmission electron microscopy was used to visualize the porosity of the structures. The reduced elastic modulus of the micropillars associated positively and linearly with the scanning power. On the other hand, the porosity and pore size of the micropillars associated inversely and linearly with the scanning power and reagent concentrations. While keeping the elastic modulus constant, the stiffness of the micropillars was controlled by varying their height. Subsequently, the single cell traction forces of rabbit chondrocytes, human dermal fibroblasts, human mesenchymal stem cells, and bovine nucleus pulposus cells (bNPCs) were successfully measured by culturing the cells on micropillar arrays of different stiffness. Our results showed that the traction forces of all groups showed positive relationship with stiffness, and that the chondrocytes and bNPCs generated the highest and lowest traction forces, respectively.

AFM nanoscale indentation in air of polymeric and hybrid materials with highly different stiffness

NASA Astrophysics Data System (ADS)

Suriano, Raffaella; Credi, Caterina; Levi, Marinella; Turri, Stefano

2014-08-01

In this study, nanomechanical properties of a variety of polymeric materials was investigated by means of AFM. In particular, selecting different AFM probes, poly(methyl methacrylate) (PMMA), polydimethylsiloxane (PDMS) bulk samples, sol-gel hybrid thin films and hydrated hyaluronic acid hydrogels were indented in air to determine the elastic modulus. The force-distance curves and the indentation data were found to be greatly affected by the cantilever stiffness and by tip geometry. AFM indentation tests show that the choice of the cantilever spring constant and of tip shape is crucially influenced by elastic properties of samples. When adhesion-dominated interactions occur between the tip and the surface of samples, force-displacement curves reveal that a suitable functionalization of AFM probes allows the control of such interactions and the extraction of Young' modulus from AFM curves that would be otherwise unfeasible. By applying different mathematical models depending on AFM probes and materials under investigation, the values of Young's modulus were obtained and compared to those measured by rheological and dynamic mechanical analysis or to literature data. Our results show that a wide range of elastic moduli (10 kPa-10 GPa) can be determined by AFM in good agreement with those measured by conventional macroscopic measurements.

Determination of elastic modulus of ceramics using ultrasonic testing

NASA Astrophysics Data System (ADS)

Sasmita, Firmansyah; Wibisono, Gatot; Judawisastra, Hermawan; Priambodo, Toni Agung

2018-04-01

Elastic modulus is important material property on structural ceramics application. However, bending test as a common method for determining this property require particular specimen preparation. Furthermore, elastic modulus of ceramics could vary because it depends on porosity content. For structural ceramics industry, such as ceramic tiles, this property is very important. This drives the development of new method to improve effectivity or verification method as well. In this research, ultrasonic testing was conducted to determine elastic modulus of soda lime glass and ceramic tiles. The experiment parameter was frequency of probe (1, 2, 4 MHz). Characterization of density and porosity were also done for analysis. Results from ultrasonic testing were compared with elastic modulus resulted from bending test. Elastic modulus of soda-lime glass based on ultrasonic testing showed excellent result with error 2.69% for 2 MHz probe relative to bending test result. Testing on red and white ceramic tiles were still contained error up to 41% and 158%, respectively. The results for red ceramic tile showed trend that 1 MHz probe gave better accuracy in determining elastic modulus. However, testing on white ceramic tile showed different trend. It was due to the presence of porosity and near field effect.

Developing the elastic modulus measurement of asphalt concrete using the compressive strength test

NASA Astrophysics Data System (ADS)

Setiawan, Arief; Suparma, Latif Budi; Mulyono, Agus Taufik

2017-11-01

Elastic modulus is a fundamental property of an asphalt mixture. An analytical method of the elastic modulus is needed to determine the thickness of flexible pavement. It has a role as one of the input values on a stress-strain analysis in the finite element method. The aim of this study was to develop the measurement of the elastic modulus by using compressive strength testing. This research used a set of specimen mold tool and Delta Dimensi software to record strain changes occurring in the proving ring of compression machine and the specimens. The elastic modulus of the five types of aggregate gradation and 2 types of asphalt were measured at optimum asphalt content. Asphalt Cement 60/70 and Elastomer Modified Asphalt (EMA) were used as a binder. Manufacturing success indicators of the specimens used void-in-the-mix (VIM) 3-5 % criteria. The success rate of the specimen manufacturing was more than 76%. Thus, the procedure and the compressive strength test equipment could be used for the measurement of the elastic modulus. The aggregate gradation and asphalt types significantly affected the elastic modulus of the asphalt concrete.

Shear modulus of porcine coronary artery in reference to a new strain measure.

PubMed

Zhang, Wei; Lu, Xiao; Kassab, Ghassan S

2007-11-01

To simplify the stress-strain relationship of blood vessels, we define a logarithmic-exponential (log-exp) strain measure to absorb the nonlinearity. As a result, the constitutive relation between the second Piola-Kirchhoff stress and the log-exp strain can be written as a generalized Hooke's law. In this work, the shear modulus of porcine coronary arteries is determined from the experimental data in inflation-stretch-torsion tests. It is found that the shear modulus with respect to the log-exp strain can be viewed as a material constant in the full range of elasticity, and the incremental shear modulus for Cauchy shear stress and small shear strain at various loading levels can be predicted by the proposed Hooke's law. This result further validates the linear constitutive relation for blood vessels when shear deformation is involved.

Direct Shear Failure in Reinforced Concrete Beams under Impulsive Loading

DTIC Science & Technology

1983-09-01

115 References ............... ............................. 119 Tables . ............................. 124 Figures ............ 1..............30...8217. : = differentiable functions of time 1 = elastic modulus enhancement function 4) 41’ = constants for a given mode W’, = frequency w tfirst thickness-shear...are defined by linear partial differential equations. The analytic results are compared to data gathered on one-way slabs loaded with impulsive blast

Elastic properties of porous low-k dielectric nano-films

NASA Astrophysics Data System (ADS)

Zhou, W.; Bailey, S.; Sooryakumar, R.; King, S.; Xu, G.; Mays, E.; Ege, C.; Bielefeld, J.

2011-08-01

Low-k dielectrics have predominantly replaced silicon dioxide as the interlayer dielectric for interconnects in state of the art integrated circuits. In order to further reduce interconnect RC delays, additional reductions in k for these low-k materials are being pursued via the introduction of controlled levels of porosity. The main challenge for such dielectrics is the substantial reduction in elastic properties that accompanies the increased pore volume. We report on Brillouin light scattering measurements used to determine the elastic properties of these films at thicknesses well below 200 nm, which are pertinent to their introduction into present ultralarge scale integrated technology. The observation of longitudinal and transverse standing wave acoustic resonances and their transformation into traveling waves with finite in-plane wave vectors provides for a direct non-destructive measure of the principal elastic constants that characterize the elastic properties of these porous nano-scale films. The mode dispersion further confirms that for porosity levels of up to 25%, the reduction in the dielectric constant does not result in severe degradation in the Young's modulus and Poisson's ratio of the films.

Mechanical Properties of a High Lead Glass Used in the Mars Organic Molecule Analyzer

NASA Technical Reports Server (NTRS)

Salem, Jonathan A.; Smith, Nathan A.; Ersahin, Akif

2015-01-01

The elastic constants, strength, fracture toughness, slow crack growth parameters, and mirror constant of a high lead glass supplied as tubes and funnels were measured using ASTM International (formerly ASTM, American Society for Testing and Materials) methods and modifications thereof. The material exhibits lower Young's modulus and slow crack growth exponent as compared to soda-lime silica glass. Highly modified glasses exhibit lower fracture toughness and slow crack growth exponent than high purity glasses such as fused silica.

Indentation-derived elastic modulus of multilayer thin films: Effect of unloading induced plasticity

DOE PAGES

Jamison, Ryan Dale; Shen, Yu -Lin

2015-08-13

Nanoindentation is useful for evaluating the mechanical properties, such as elastic modulus, of multilayer thin film materials. A fundamental assumption in the derivation of the elastic modulus from nanoindentation is that the unloading process is purely elastic. In this work, the validity of elastic assumption as it applies to multilayer thin films is studied using the finite element method. The elastic modulus and hardness from the model system are compared to experimental results to show validity of the model. Plastic strain is shown to increase in the multilayer system during the unloading process. Additionally, the indentation-derived modulus of a monolayermore » material shows no dependence on unloading plasticity while the modulus of the multilayer system is dependent on unloading-induced plasticity. Lastly, the cyclic behavior of the multilayer thin film is studied in relation to the influence of unloading-induced plasticity. Furthermore, it is found that several cycles are required to minimize unloading-induced plasticity.« less

Mechanical, lattice dynamical and electronic properties of CeO2 at high pressure: First-principles studies

NASA Astrophysics Data System (ADS)

Li, Mei; Jia, Huiling; Li, Xueyan; Liu, Xuejie

2016-01-01

The elastic constants (Cij), bulk modulus (B), shear modulus (G) and elastic modulus (E) of cubic fluorite CeO2 under high pressure have been studied using the plane-wave pseudopotential method based on density functional theory. The calculated results show that the mechanical properties (Cij, B, G and E) of CeO2 increase with increasing pressure, and the phase transition of CeO2 occurs beyond the pressure of 130 GPa. From the calculated phonon spectrum using Parlinsk-Li-Kawasoe method, we found that CeO2 appears imaginary frequency at 140 GPa, which indicates phase transition. The energy band, density of states and charge density of CeO2 under high pressure are calculated using GGA+U method. It is found that the high pressure makes the electron delocalization and Ce-O covalent bonding enhanced. As pressure increases, the band gap between O2p and Ce4f states near the Fermi level increases, and CeO2 nonmetallic nature promotes. The present research results in a better understanding of how CeO2 responds to compression.

Theoretical study on elastic properties of Si2N2O by ab initio calculation

NASA Astrophysics Data System (ADS)

Tsuboi, Seiya; Adachi, Kanta; Nagakubo, Akira; Ogi, Hirotsugu

2018-07-01

The elastic constants of crystalline Si2N2O remain unknown since it was discovered in the 1960s. We determine the nine independent elastic constants of orthorhombic Si2N2O by ab initio calculations. We applied various deformation modes with strains up to ±0.01 to a unit cell, calculated the energy-strain relationships, and deduced all the elastic constants by fitting the harmonic-oscillation function. Our results are as follows: C 11 = 311.1, C 22 = 238.5, C 33 = 317.9, C 44 = 136.1, C 55 = 57.6, C 66 = 73.9, C 12 = 79.6, C 13 = 52.2, and C 23 = 33.6 GPa. Despite the different crystal structures and symmetries, the direction-over-averaged Young’s modulus of Si2N2O is well explained by the nitrogen content and Young’s moduli of α-SiO2 and β-Si3N4. The anisotropy of sound-wave velocity was investigated, and its origin was examined on the basis of the crystallographic structure. The quasi-isotropic plane for the longitudinal-wave propagation was identified.

Oscillatory shear response of moisture barrier coatings containing clay of different shape factor.

PubMed

Kugge, C; Vanderhoek, N; Bousfield, D W

2011-06-01

Oscillatory shear rheology of barrier coatings based on dispersed styrene-butadiene latex and clay of various shape factors or aspect ratio has been explored. Barrier performance of these coatings when applied to paperboard has been assessed in terms of water vapour transmission rates and the results related to shape factor, dewatering and critical strain. It has been shown that a system based on clay with high shape factor gives a lower critical strain, dewatering and water vapour transmission rate compared with clays of lower shape factor. The dissipated energy, as calculated from an amplitude sweep, indicated no attractive interaction between clay and latex implying a critical strain that appears to be solely dependent on the shape factor at a constant volume fraction. Particle size distribution was shown to have no effect on the critical strain while coatings of high elasticity exhibited high yield strains as expected. The loss modulus demonstrated strain hardening before the elastic to viscous transition. The loss modulus peak was identified by a maximum strain which was significantly lower for a coating based on clay with a high shape factor. The characteristic elastic time was found to vary between 0.6 and 1.3s. The zero shear viscosity of barrier dispersion coatings were estimated from the characteristic elastic time and the characteristic modulus to be of the order of 25-100 Pa s. Copyright © 2011 Elsevier Inc. All rights reserved.

Silica-Coated Core-Shell Structured Polystyrene Nanospheres and Their Size-Dependent Mechanical Properties.

PubMed

Cao, Xu; Pan, Guoshun; Huang, Peng; Guo, Dan; Xie, Guoxin

2017-08-22

The core-shell structured PS/SiO 2 composite nanospheres were synthesized on the basis of a modified Stöber method. The mechanical properties of monodisperse nanospheres were characterized with nanoindentation on the basis of the atomic force microscopy (AFM). The surface morphologies of PS/SiO 2 composite nanospheres was scanned with the tapping mode of AFM, and the force-distance curves were measured with the contact mode of AFM. Different contact models were compared for the analyses of experimental data. The elastic moduli of PS/SiO 2 composite nanosphere (4-40 GPa) and PS nanosphere (∼3.4 GPa) were obtained with the Hertz and Johnson-Kendall-Roberts (JKR) models, respectively, and the JKR model was proven to be more appropriate for calculating the elastic modulus of PS/SiO 2 nanospheres. The elastic modulus of SiO 2 shell gradually approached a constant value (∼46 GPa) with the increase of SiO 2 shell thickness. A core-shell model was proposed for describing the relationship between PS/SiO 2 composite nanosphere's elastic modulus and shell thickness. The mechanical properties of the composite nanospheres were reasonably explained on the basis of the growth mechanism of PS/SiO 2 composite nanospheres, in particular the SiO 2 shell's formation process. Available research data of PS/SiO 2 composite nanospheres in this work can provide valuable guidance for their effective application in surface engineering, micro/nanomanufacturing, lubrication, and so on.

Indentation size effect of cortical bones submitted to different soft tissue removals.

PubMed

Bandini, A; Chicot, D; Berry, P; Decoopman, X; Pertuz, A; Ojeda, D

2013-04-01

Properties of elasticity, hardness and viscosity are determined for the study of the visco-elastoplastic behavior of bones. The mechanical properties are compared in two upright sections of the bone due to their anisotropy. Besides, influence of hydration treatments leading to structural modifications of collagen and ground substance contents of bones on the mechanical properties is studied on a femoral cortical bovine bone. The treatments applied to the bone are used by forensic anthropologists to remove the soft tissue and modifying the hydration degree coupled to the collagen content. From instrumented indentation experiments, the hardness is characterized by the macrohardness and a hardness length-scale factor stating the hardness-load dependence. The elastic modulus results from the application of the methodology of Oliver and Pharr (1992). The coefficient of viscosity is deduced from a rheological model representing the indenter time-displacement observed under the application of a constant load. As a result, all the mechanical properties are found to be lower in the transverse section in an extent depending on the hydration treatment, i.e. the different values are located between 5% and 25% for the hardness around 0.5GPa, between 25% and 40% for the elastic modulus around 20GPa and between 2% and 35% for the coefficient of viscosity around 60GPa.s. Unexpectedly, the elastic modulus to coefficient of viscosity ratio is found to be independent on the hydration treatment. Copyright © 2013 Elsevier Ltd. All rights reserved.

Structural relaxation driven increase in elastic modulus for a bulk metallic glass

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

Arora, Harpreet Singh; Aditya, Ayyagari V.; Mukherjee, Sundeep, E-mail: sundeep.mukherjee@unt.edu

2015-01-07

The change in elastic modulus as a function of temperature was investigated for a zirconium-based bulk metallic glass. High temperature nano-indentation was done over a wide temperature range from room temperature to the glass-transition. At higher temperature, there was a transition from inhomogeneous to homogeneous deformation, with a decrease in serrated flow and an increase in creep displacement. Hardness was found to decrease, whereas elastic modulus was found to increase with temperature. The increase in elastic modulus for metallic glass at higher temperature was explained by diffusive rearrangement of atoms resulting in free volume annihilation. This is in contrast tomore » elastic modulus increase with temperature for silicate glasses due to compaction of its open three dimensional coordinated structure without any atomic diffusion.« less

Variable stiffness torsion springs

NASA Astrophysics Data System (ADS)

Alhorn, Dean C.; Polites, Michael E.

1994-05-01

In a torsion spring the spring action is a result of the relationships between the torque applied in twisting the spring, the angle through which the torsion spring twists, and the modulus of elasticity of the spring material in shear. Torsion springs employed industrially have been strips, rods, or bars, generally termed shafts, capabable of being flexed by twisting their axes. They rely on the variations in shearing forces to furnish an internal restoring torque. In the torsion springs herein the restoring torque is external and therefore independent of the shearing modulus of elasticity of the torsion spring shaft. Also provided herein is a variable stiffness torsion spring. This torsion spring can be so adjusted as to have a given spring constant. Such variable stiffness torsion springs are extremely useful in gimballed payloads such as sensors, telescopes, and electronic devices on such platforms as a space shuttle or a space station.

Variable stiffness torsion springs

NASA Technical Reports Server (NTRS)

Alhorn, Dean C. (Inventor); Polites, Michael E. (Inventor)

1995-01-01

In a torsion spring the spring action is a result of the relationships between the torque applied in twisting the spring, the angle through which the torsion spring twists, and the modulus of elasticity of the spring material in shear. Torsion springs employed industrially have been strips, rods, or bars, generally termed shafts, capabable of being flexed by twisting their axes. They rely on the variations in shearing forces to furnish an internal restoring torque. In the torsion springs herein the restoring torque is external and therefore independent of the shearing modulus of elasticity of the torsion spring shaft. Also provided herein is a variable stiffness torsion spring. This torsion spring can be so adjusted as to have a given spring constant. Such variable stiffness torsion springs are extremely useful in gimballed payloads such as sensors, telescopes, and electronic devices on such platforms as a space shuttle or a space station.

Variable stiffness torsion springs

NASA Astrophysics Data System (ADS)

Alhorn, Dean C.; Polites, Michael E.

1995-08-01

In a torsion spring the spring action is a result of the relationships between the torque applied in twisting the spring, the angle through which the torsion spring twists, and the modulus of elasticity of the spring material in shear. Torsion springs employed industrially have been strips, rods, or bars, generally termed shafts, capabable of being flexed by twisting their axes. They rely on the variations in shearing forces to furnish an internal restoring torque. In the torsion springs herein the restoring torque is external and therefore independent of the shearing modulus of elasticity of the torsion spring shaft. Also provided herein is a variable stiffness torsion spring. This torsion spring can be so adjusted as to have a given spring constant. Such variable stiffness torsion springs are extremely useful in gimballed payloads such as sensors, telescopes, and electronic devices on such platforms as a space shuttle or a space station.

Variable stiffness torsion springs

NASA Technical Reports Server (NTRS)

Alhorn, Dean C. (Inventor); Polites, Michael E. (Inventor)

1994-01-01

In a torsion spring the spring action is a result of the relationships between the torque applied in twisting the spring, the angle through which the torsion spring twists, and the modulus of elasticity of the spring material in shear. Torsion springs employed industrially have been strips, rods, or bars, generally termed shafts, capabable of being flexed by twisting their axes. They rely on the variations in shearing forces to furnish an internal restoring torque. In the torsion springs herein the restoring torque is external and therefore independent of the shearing modulus of elasticity of the torsion spring shaft. Also provided herein is a variable stiffness torsion spring. This torsion spring can be so adjusted as to have a given spring constant. Such variable stiffness torsion springs are extremely useful in gimballed payloads such as sensors, telescopes, and electronic devices on such platforms as a space shuttle or a space station.

Dynamic rheology of food protein networks

USDA-ARS?s Scientific Manuscript database

Small amplitude oscillatory shear analyses of samples containing protein are useful for determining the nature of the protein matrix without damaging it. Elastic modulus, viscous modulus, and loss tangent (the ratio of viscous modulus to elastic modulus) give information on the strength of the netw...

High pressure and temperature induced structural and elastic properties of lutetium chalcogenides

NASA Astrophysics Data System (ADS)

Shriya, S.; Kinge, R.; Khenata, R.; Varshney, Dinesh

2018-04-01

The high-pressure structural phase transition and pressure as well temperature induced elastic properties of rock salt to CsCl structures in semiconducting LuX (X = S, Se, and Te) chalcogenides compound have been performed using effective interionic interaction potential with emphasis on charge transfer interactions and covalent contribution. Estimated values of phase transition pressure and the volume discontinuity in pressure-volume phase diagram indicate the structural phase transition from ZnS to NaCl structure. From the investigations of elastic constants the pressure (temperature) dependent volume collapse/expansion, melting temperature TM, Hardness (HV), and young modulus (E) the LuX lattice infers mechanical stiffening, and thermal softening.

Structural, Electronic and Elastic Properties of Heavy Fermion YbTM2 (TM= Ir and Pt) Laves Phase Compounds

NASA Astrophysics Data System (ADS)

Pawar, H.; Shugani, M.; Aynyas, M.; Sanyal, S. P.

2018-02-01

The structural, electronic and elastic properties of YbTM2 (TM = Ir and Pt) Laves phase intermetallic compounds which crystallize in cubic (MgCu2-type) structure, have been investigated using ab-initio full potential linearized augmented plane wave (FP-LAPW) method with LDA and LDA+U approximation. The calculated ground state properties such as lattice parameter (a0), bulk modulus (B) and its pressure derivative (B‧) are in good agreement with available experimental and theoretical data. The electronic properties are analyzed from band structures and density of states. Elastic constants are predicted first time for these compounds which obey the stability criteria for cubic system.

Analysis of the compressive behaviour of the three-dimensional printed porous titanium for dental implants using a modified cellular solid model.

PubMed

Gagg, Graham; Ghassemieh, Elaheh; Wiria, Florencia E

2013-09-01

A set of cylindrical porous titanium test samples were produced using the three-dimensional printing and sintering method with samples sintered at 900 °C, 1000 °C, 1100 °C, 1200 °C or 1300 °C. Following compression testing, it was apparent that the stress-strain curves were similar in shape to the curves that represent cellular solids. This is despite a relative density twice as high as what is considered the threshold for defining a cellular solid. As final sintering temperature increased, the compressive behaviour developed from being elastic-brittle to elastic-plastic and while Young's modulus remained fairly constant in the region of 1.5 GPa, there was a corresponding increase in 0.2% proof stress of approximately 40-80 MPa. The cellular solid model consists of two equations that predict Young's modulus and yield or proof stress. By fitting to experimental data and consideration of porous morphology, appropriate changes to the geometry constants allow modification of the current models to predict with better accuracy the behaviour of porous materials with higher relative densities (lower porosity).

Muscle shear elastic modulus is linearly related to muscle torque over the entire range of isometric contraction intensity.

PubMed

Ateş, Filiz; Hug, François; Bouillard, Killian; Jubeau, Marc; Frappart, Thomas; Couade, Mathieu; Bercoff, Jeremy; Nordez, Antoine

2015-08-01

Muscle shear elastic modulus is linearly related to muscle torque during low-level contractions (<60% of Maximal Voluntary Contraction, MVC). This measurement can therefore be used to estimate changes in individual muscle force. However, it is not known if this relationship remains valid for higher intensities. The aim of this study was to determine: (i) the relationship between muscle shear elastic modulus and muscle torque over the entire range of isometric contraction and (ii) the influence of the size of the region of interest (ROI) used to average the shear modulus value. Ten healthy males performed two incremental isometric little finger abductions. The joint torque produced by Abductor Digiti Minimi was considered as an index of muscle torque and elastic modulus. A high coefficient of determination (R(2)) (range: 0.86-0.98) indicated that the relationship between elastic modulus and torque can be accurately modeled by a linear regression over the entire range (0% to 100% of MVC). The changes in shear elastic modulus as a function of torque were highly repeatable. Lower R(2) values (0.89±0.13 for 1/16 of ROI) and significantly increased absolute errors were observed when the shear elastic modulus was averaged over smaller ROI, half, 1/4 and 1/16 of the full ROI) than the full ROI (mean size: 1.18±0.24cm(2)). It suggests that the ROI should be as large as possible for accurate measurement of muscle shear modulus. Copyright © 2015 Elsevier Ltd. All rights reserved.

First-principles investigation of mechanical and electronic properties of tetragonal NbAl3 under tension

NASA Astrophysics Data System (ADS)

Jiao, Zhen; Liu, Qi-Jun; Liu, Fu-Sheng; Tang, Bin

2018-06-01

Using the density functional theory calculations, the mechanical and electronic properties of NbAl3 under different tensile loads were investigated. The calculated lattice parameters, elastic constants and mechanical properties (bulk modulus, shear modulus, Young's modulus, Poisson's ratio, Pugh's criterion and Cauchy's pressure) indicated that our results were in agreement with the published experimental and theoretical data at zero tension. With respect to NbAl3 under tension in this paper, the crystal structure was changed from tetragonal to orthorhombic under tension along the [100] and [101] directions. The NbAl3 crystal has been classified as brittle material under tension from 0 to 20 GPa. The obtained Young's modulus and Debye temperature monotonically decreased with increasing tension stress. Combining with mechanical and electronic properties in detail, the decreased mechanical properties were mainly due to the weakening of covalency.

Properties of medium-density fiberboard produced in an oil-heated laboratory press

Treesearch

O. Suchsland; G.E. Woodson

1976-01-01

Medium-density fiberboards from pressurized double-disk refined fibers have a close correlation between layer density and layer dynamic modulus of elasticity. Density distribution over the thickness was readily controlled by manipulating platen temperature and applied pressure. Thus, overall modulus of elasticity could be adjusted. In contrast to modulus of elasticity...

Influence of Selected Factors on the Relationship between the Dynamic Elastic Modulus and Compressive Strength of Concrete

PubMed Central

Jurowski, Krystian; Grzeszczyk, Stefania

2018-01-01

In this paper, the relationship between the static and dynamic elastic modulus of concrete and the relationship between the static elastic modulus and compressive strength of concrete have been formulated. These relationships are based on investigations of different types of concrete and take into account the type and amount of aggregate and binder used. The dynamic elastic modulus of concrete was tested using impulse excitation of vibration and the modal analysis method. This method could be used as a non-destructive way of estimating the compressive strength of concrete. PMID:29565830

Influence of Selected Factors on the Relationship between the Dynamic Elastic Modulus and Compressive Strength of Concrete.

PubMed

Jurowski, Krystian; Grzeszczyk, Stefania

2018-03-22

In this paper, the relationship between the static and dynamic elastic modulus of concrete and the relationship between the static elastic modulus and compressive strength of concrete have been formulated. These relationships are based on investigations of different types of concrete and take into account the type and amount of aggregate and binder used. The dynamic elastic modulus of concrete was tested using impulse excitation of vibration and the modal analysis method. This method could be used as a non-destructive way of estimating the compressive strength of concrete.

First principles predictions of electronic and elastic properties of BaPb2As2 in the ThCr2Si2-type structure

NASA Astrophysics Data System (ADS)

Bourourou, Y.; Amari, S.; Yahiaoui, I. E.; Bouhafs, B.

2018-01-01

A first-principles approach is used to predicts the electronic and elastic properties of BaPb2As2 superconductor compound, using full-potential linearized augmented plane wave plus local orbitals (FP-L/APW+lo) scheme within the local density approximation LDA. The calculated equilibrium structural parameter a agree well with the experiment while the c/a ratio is far away from the experimental result. The band structure, density of states, together with the charge density and chemical bonding are discussed. The calculated elastic constants for our compound indicate that it is mechanically stable at ambient pressure. Polycrystalline elastic moduli (Young's, Bulk, shear Modulus and the Poisson's ratio) were calculated according to the Voigte-Reusse-Hill (VRH) average.

Effect of observed micropolar motions on wave propagation in deep Earth minerals

NASA Astrophysics Data System (ADS)

Abreu, Rafael; Thomas, Christine; Durand, Stephanie

2018-03-01

We provide a method to compute the Cosserat couple modulus for a bridgmanite (MgSiO3 silicate perovskite) solid from frequency gaps observed in Raman experiments. To this aim, we apply micropolar theory which is a generalization of the classical linear elastic theory, where each particle has an intrinsic rotational degree of freedom, called micro-rotation and/or spin, and which depends on the so-called Cosserat couple modulus μc that characterizes the micropolar medium. We investigate both wave propagation and dispersion. The wave propagation simulations in both potassium nitrate (KNO3) and bridgmanite crystal leads to a faster elastic wave propagation as well as to an independent rotational field of motion, called optic mode, which is smaller in amplitude compared to the conventional rotational field. The dispersion analysis predicts that the optic mode only appears above a cutoff frequency, ωr , which has been observed in Raman experiments done at high pressures and temperatures on bridgmanite crystal. The comparison of the cutoff frequency observed in experiments and the micropolar theory enables us to compute for the first time the temperature and pressure dependency of the Cosserat couple modulus μc of bridgmanite. This study thus shows that the micropolar theory can explain particle motions observed in laboratory experiments that were before neglected and that can now be used to constrain the micropolar elastic constants of Earth's mantle like material. This pioneer work aims at encouraging the use of micropolar theory in future works on deep Earth's mantle material by providing Cosserat couple modulus that were not available before.

On the role of API in determining porosity, pore structure and bulk modulus of the skeletal material in pharmaceutical tablets formed with MCC as sole excipient.

PubMed

Ridgway, Cathy; Bawuah, Prince; Markl, Daniel; Zeitler, J Axel; Ketolainen, Jarkko; Peiponen, Kai-Erik; Gane, Patrick

2017-06-30

The physical properties and mechanical integrity of pharmaceutical tablets are of major importance when loading with active pharmaceutical ingredient(s) (API) in order to ensure ease of processing, control of dosage and stability during transportation and handling prior to patient consumption. The interaction between API and excipient, acting as functional extender and binder, however, is little understood in this context. The API indomethacin is combined in this study with microcrystalline cellulose (MCC) at increasing loading levels. Tablets from the defined API/MCC ratios are made under conditions of controlled porosity and tablet thickness, resulting from different compression conditions, and thus compaction levels. Mercury intrusion porosimetry is used to establish the accessible pore volume, pore size distribution and, adopting the observed region of elastic intrusion-extrusion at high pressure, an elastic bulk modulus of the skeletal material is recorded. Porosity values are compared to previously published values derived from terahertz (THz) refractive index data obtained from exactly the same tablet sample sets. It is shown that the elastic bulk modulus is dependent on API wt% loading under constant tablet preparation conditions delivering equal dimensions and porosity. The findings are considered of novel value in respect to establishing consistency of tablet production and optimisation of physical properties. Copyright © 2017 Elsevier B.V. All rights reserved.

Determining Tension-Compression Nonlinear Mechanical Properties of Articular Cartilage from Indentation Testing.

PubMed

Chen, Xingyu; Zhou, Yilu; Wang, Liyun; Santare, Michael H; Wan, Leo Q; Lu, X Lucas

2016-04-01

The indentation test is widely used to determine the in situ biomechanical properties of articular cartilage. The mechanical parameters estimated from the test depend on the constitutive model adopted to analyze the data. Similar to most connective tissues, the solid matrix of cartilage displays different mechanical properties under tension and compression, termed tension-compression nonlinearity (TCN). In this study, cartilage was modeled as a porous elastic material with either a conewise linear elastic matrix with cubic symmetry or a solid matrix reinforced by a continuous fiber distribution. Both models are commonly used to describe the TCN of cartilage. The roles of each mechanical property in determining the indentation response of cartilage were identified by finite element simulation. Under constant loading, the equilibrium deformation of cartilage is mainly dependent on the compressive modulus, while the initial transient creep behavior is largely regulated by the tensile stiffness. More importantly, altering the permeability does not change the shape of the indentation creep curves, but introduces a parallel shift along the horizontal direction on a logarithmic time scale. Based on these findings, a highly efficient curve-fitting algorithm was designed, which can uniquely determine the three major mechanical properties of cartilage (compressive modulus, tensile modulus, and permeability) from a single indentation test. The new technique was tested on adult bovine knee cartilage and compared with results from the classic biphasic linear elastic curve-fitting program.

On the eigenfrequencies of elastic shear waves propagating in an inhomogeneous layer

NASA Astrophysics Data System (ADS)

Khachatryan, V. M.

2018-04-01

In this work, we consider the problem of eigenfrequencies of elastic shear waves propagating in a layer whose Young’s modulus and density are functions of the longitudinal coordinate. Taking into account the material inhomogeneity makes the problem of the eigenfrequencies of the waves propagating in the layer more complicated. In this paper, the problem of pure shear is considered. To solve the problem, we use an integral formula which allows us to represent the general solution of the original equation with variable coefficients in terms of the general solution of the accompanying equation with constant coefficients.

Elastic modulus of single cellulose microfibrils from tunicate measured by atomic force microscopy.

PubMed

Iwamoto, Shinichiro; Kai, Weihua; Isogai, Akira; Iwata, Tadahisa

2009-09-14

The elastic modulus of single microfibrils from tunicate ( Halocynthia papillosa ) cellulose was measured by atomic force microscopy (AFM). Microfibrils with cross-sectional dimensions 8 x 20 nm and several micrometers in length were obtained by oxidation of cellulose with 2,2,6,6-tetramethylpiperidine-1-oxyl radical (TEMPO) as a catalyst and subsequent mechanical disintegration in water and by sulfuric acid hydrolysis. The nanocellulosic materials were deposited on a specially designed silicon wafer with grooves 227 nm in width, and a three-point bending test was applied to determine the elastic modulus using an AFM cantilever. The elastic moduli of single microfibrils prepared by TEMPO-oxidation and acid hydrolysis were 145.2 +/- 31.3 and 150.7 +/- 28.8 GPa, respectively. The result showed that the experimentally determined modulus of the highly crystalline tunicate microfibrils was in agreement with the elastic modulus of native cellulose crystals.

Micromechanical analysis on anisotropy of structured magneto-rheological elastomer

NASA Astrophysics Data System (ADS)

Li, R.; Zhang, Z.; Chen, S. W.; Wang, X. J.

2015-07-01

This paper investigates the equivalent elastic modulus of structured magneto-rheological elastomer (MRE) in the absence of magnetic field. We assume that both matrix and ferromagnetic particles are linear elastic materials, and ferromagnetic particles are embedded in matrix with layer-like structure. The structured composite could be divided into matrix layer and reinforced layer, in which the reinforced layer is composed of matrix and the homogenously distributed ferromagnetic particles in matrix. The equivalent elastic modulus of reinforced layer is analysed by the Mori-Tanaka method. Finite Element Method (FEM) is also carried out to illustrate the relationship between the elastic modulus and the volume fraction of ferromagnetic particles. The results show that the anisotropy of elastic modulus becomes noticeable, as the volume fraction of particles increases.

Coupling Field Theory with Mesoscopic Dynamical Simulations of Multicomponent Lipid Bilayers

PubMed Central

McWhirter, J. Liam; Ayton, Gary; Voth, Gregory A.

2004-01-01

A method for simulating a two-component lipid bilayer membrane in the mesoscopic regime is presented. The membrane is modeled as an elastic network of bonded points; the spring constants of these bonds are parameterized by the microscopic bulk modulus estimated from earlier atomistic nonequilibrium molecular dynamics simulations for several bilayer mixtures of DMPC and cholesterol. The modulus depends on the composition of a point in the elastic membrane model. The dynamics of the composition field is governed by the Cahn-Hilliard equation where a free energy functional models the coupling between the composition and curvature fields. The strength of the bonds in the elastic network are then modulated noting local changes in the composition and using a fit to the nonequilibrium molecular dynamics simulation data. Estimates for the magnitude and sign of the coupling parameter in the free energy model are made treating the bending modulus as a function of composition. A procedure for assigning the remaining parameters in the free energy model is also outlined. It is found that the square of the mean curvature averaged over the entire simulation box is enhanced if the strength of the bonds in the elastic network are modulated in response to local changes in the composition field. We suggest that this simulation method could also be used to determine if phase coexistence affects the stress response of the membrane to uniform dilations in area. This response, measured in the mesoscopic regime, is already known to be conditioned or renormalized by thermal undulations. PMID:15347594

Surface density mapping of natural tissue by a scanning haptic microscope (SHM).

PubMed

Moriwaki, Takeshi; Oie, Tomonori; Takamizawa, Keiichi; Murayama, Yoshinobu; Fukuda, Toru; Omata, Sadao; Nakayama, Yasuhide

2013-02-01

To expand the performance capacity of the scanning haptic microscope (SHM) beyond surface mapping microscopy of elastic modulus or topography, surface density mapping of a natural tissue was performed by applying a measurement theory of SHM, in which a frequency change occurs upon contact of the sample surface with the SHM sensor - a microtactile sensor (MTS) that vibrates at a pre-determined constant oscillation frequency. This change was mainly stiffness-dependent at a low oscillation frequency and density-dependent at a high oscillation frequency. Two paragon examples with extremely different densities but similar macroscopic elastic moduli in the range of natural soft tissues were selected: one was agar hydrogels and the other silicon organogels with extremely low (less than 25 mg/cm(3)) and high densities (ca. 1300 mg/cm(3)), respectively. Measurements were performed in saline solution near the second-order resonance frequency, which led to the elastic modulus, and near the third-order resonance frequency. There was little difference in the frequency changes between the two resonance frequencies in agar gels. In contrast, in silicone gels, a large frequency change by MTS contact was observed near the third-order resonance frequency, indicating that the frequency change near the third-order resonance frequency reflected changes in both density and elastic modulus. Therefore, a density image of the canine aortic wall was subsequently obtained by subtracting the image observed near the second-order resonance frequency from that near the third-order resonance frequency. The elastin-rich region had a higher density than the collagen-rich region.

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

Heffernan, Karina M.; Ross, Nancy L., E-mail: nross@vt.edu; Spencer, Elinor C.

Accurate elastic constants for gadolinium phosphate (GdPO{sub 4}) have been measured by single-crystal high-pressure diffraction methods. The bulk modulus of GdPO{sub 4} determined under hydrostatic conditions, 128.1(8) GPa (K′=5.8(2)), is markedly different from that obtained with GdPO{sub 4} under non-hydrostatic conditions (160(2) GPa), which indicates the importance of shear stresses on the elastic response of this phosphate. High pressure Raman and diffraction analysis indicate that the PO{sub 4} tetrahedra behave as rigid units in response to pressure and that contraction of the GdPO{sub 4} structure is facilitated by bending/twisting of the Gd–O–P links that result in increased distortion in themore » GdO{sub 9} polyhedra. - Graphical abstract: A high-pressure single crystal diffraction study of GdPO{sub 4} with the monazite structure is presented. The elastic behaviour of rare-earth phosphates are believed to be sensitive to shear forces. The bulk modulus of GdPO{sub 4} measured under hydrostatic conditions is 128.1(8) GPa. Compression of the structure is facilitated by bending/twisting of the Gd−O−P links that result in increased distortion in the GdO{sub 9} polyhedra. Display Omitted - Highlights: • The elastic responses of rare-earth phosphates are sensitive to shear forces. • The bulk modulus of GdPO{sub 4} measured under hydrostatic conditions is 128.1(8) GPa. • Twisting of the inter-polyhedral links allows compression of the GdPO{sub 4} structure. • Changes to the GdO{sub 9} polyhedra occur in response to pressure (<7.0 GPa).« less

Lipid Neuroprotectants and Traumatic Glaucomatous Neurodegeneration

DTIC Science & Technology

2016-05-01

alter elastic TM, modulus and binding and functional assays with potential protein targets. Endogenous lipids, Aqueous humor, Trabecular meshwork...Intraocular pressure, sphingolipids, primary cell culture, elastic modulus, protein targets. Major goal 1. Test the hypothesis that selected lipids...glaucomatous TM with and without these lipids and atomic force microscope (AFM). Further elastic modulus using high flow and low flow areas of glaucomatous

Influence of Waste Tyre Crumb Rubber on Compressive Strength, Static Modulus of Elasticity and Flexural Strength of Concrete

NASA Astrophysics Data System (ADS)

Haridharan, M. K.; Bharathi Murugan, R.; Natarajan, C.; Muthukannan, M.

2017-07-01

In this paper, the experimental investigations was carried out to find the compressive strength, static modulus of elasticity and flexural strength of concrete mixtures, in which natural sand was partially replaced with Waste Tyre Crumb Rubber (WTCR). River sand was replaced with five different percentages (5%, 10%, 15%, 20% and 25%) of WTCR by volume. The main objective of the experimental investigation is to find the relationship between static modulus of elasticity and flexural strength with compressive strength of concrete with WTCR. The experimentally obtainedstatic modulus of elasticity and flexural strength results comparing with the theoretical values (various country codes recommendations).

Static and vibrational properties of equiatomic Na-based binary alloys

NASA Astrophysics Data System (ADS)

Vora, Aditya M.

2007-09-01

The computations of the static and vibrational properties of four equiatomic Na-based binary alloys viz. Na0.5Li0.5, Na0.5K0.5, Na0.5Rb0.5 and Na0.5Cs0.5, to second order in local model potential is discussed in terms of real-space sum of Born von Karman central force constants. The local field correlation functions due to Hartree (H), Ichimaru Utsumi (IU) and Sarkar et al. (S) are used to investigate the influence of the screening effects on the aforesaid properties. Results for the lattice constants C11, C12, C44, C12 C44, C12/C44 and bulk modulus B obtained using the H-local field correction function have higher values in comparison with the results obtained for the same properties using IU- and S-local field correction functions. The results for the Shear modulus (C‧), deviation from Cauchy's relation, Poisson's ratio σ, Young modulus Y, propagation velocity of elastic waves, phonon dispersion curves and degree of anisotropy A are highly appreciable for the four equiatomic Na-based binary alloys.

Shear elastic modulus estimation from indentation and SDUV on gelatin phantoms

PubMed Central

Amador, Carolina; Urban, Matthew W.; Chen, Shigao; Chen, Qingshan; An, Kai-Nan; Greenleaf, James F.

2011-01-01

Tissue mechanical properties such as elasticity are linked to tissue pathology state. Several groups have proposed shear wave propagation speed to quantify tissue mechanical properties. It is well known that biological tissues are viscoelastic materials; therefore velocity dispersion resulting from material viscoelasticity is expected. A method called Shearwave Dispersion Ultrasound Vibrometry (SDUV) can be used to quantify tissue viscoelasticity by measuring dispersion of shear wave propagation speed. However, there is not a gold standard method for validation. In this study we present an independent validation method of shear elastic modulus estimation by SDUV in 3 gelatin phantoms of differing stiffness. In addition, the indentation measurements are compared to estimates of elasticity derived from shear wave group velocities. The shear elastic moduli from indentation were 1.16, 3.40 and 5.6 kPa for a 7, 10 and 15% gelatin phantom respectively. SDUV measurements were 1.61, 3.57 and 5.37 kPa for the gelatin phantoms respectively. Shear elastic moduli derived from shear wave group velocities were 1.78, 5.2 and 7.18 kPa for the gelatin phantoms respectively. The shear elastic modulus estimated from the SDUV, matched the elastic modulus measured by indentation. On the other hand, shear elastic modulus estimated by group velocity did not agree with indentation test estimations. These results suggest that shear elastic modulus estimation by group velocity will be bias when the medium being investigated is dispersive. Therefore a rheological model should be used in order to estimate mechanical properties of viscoelastic materials. PMID:21317078

Temperature-dependent elasticity of Pb [(Mg0.33Nb0.67 ) 1 -xT ix ] O3

NASA Astrophysics Data System (ADS)

Tennakoon, Sumudu; Gladden, Joseph; Mookherjee, Mainak; Besara, Tiglet; Siegrist, Theo

2017-10-01

Relaxor ferroelectric materials, such as Pb [(Mg0.33Nb0.67 ) 1 -xT ix ] O3 (PMN-PT) with generic stoichiometry, undergo a ferroelectric-to-paraelectric phase transition as a function of temperature. The exact transition characterized by Curie temperature (Tc) varies as a function of chemistry (x ), i.e., the concentration of Ti. In this study, we investigated the structural phase transition by exploring the temperature dependence of the single-crystal elastic properties of Pb [(Mg0.33Nb0.67 ) 0.7T i0.3 ] O3 , i.e., x ≈0.3 . We used resonant ultrasound spectroscopy to determine the elasticity at elevated temperatures, from which Tc=398 ±5 K for PMN-PT (x ≈0.3 ) was determined. We report the full elastic constant tensor (Ci j={ C11,C12,C44 }), acoustic attenuation (Q-1), longitudinal (VP) and shear (VS) sound velocities, and elastic anisotropy of PMN-PT as a function of temperature for 400 Tc the material first stiffens and reaches maxima in the vicinity of the Burns temperature (Tb˜673 K ), followed by a more typical gradual softening of the elastic constants. Similar temperature-dependent anomalies are also observed with anisotropy and Q-1, with minima in the vicinity of Tb. We used the temperature dependence of Ci j, Q-1, VP,VS , and anisotropy to infer the evolution of polar nanoregions as the material evolved from T >Tc .

The threshold strength of laminar ceramics utilizing molar volume changes and porosity

NASA Astrophysics Data System (ADS)

Pontin, Michael Gene

It has been shown that uniformly spaced thin compressive layers within a ceramic body can arrest the propagation of an otherwise catastrophic crack, producing a threshold strength: a strength below which the probability of failure is zero. Previous work has shown that the threshold strength increases with both the magnitude of the compressive stress and the fracture toughness of the thin layer material, and finite element analysis predicts that the threshold strength can be further increased when the elastic modulus of the compressive layer is much smaller than the thicker layer. The current work describes several new approaches to increase the threshold strength of a laminar ceramic system. The initial method utilized a molar volume expansion within the thin layers, produced by the tetragonal-to-monoclinic phase transformation of unstabilized zirconia during cooling, in order to produce large compressive stresses within the thin layers. High threshold strengths were measured for this system, but they remained relatively constant as the zirconia content was increased. It was determined that microcracking produced during the transformation reduced the magnitude of the compressive stresses, but may also have served to reduce the modulus of the thin compressive layer, providing an additional strengthening mechanism. The second approach studied the addition of porosity to reduce the elastic modulus of the thin compressive layers. A new processing method was created and analyzed, in which thick layers of the laminate were fabricated by tape-casting, and then dip-coated into a slurry, containing rice starch, to create thin porous compressive layers upon densification. The effects of porosity on the residual compressive stress, elastic modulus, and fracture toughness of the thin layers were measured and calculated, and it was found that the elastic modulus mismatch between the thin and thick layers produced a large strengthening effect for volume fractions of porosity below a critical level. Specimens with greater volume fractions of porosity exhibited complete crack arrest, typically followed by non-catastrophic failure, as cracks initiating in adjacent thick layers coalesced by cracking or delamination along the thin porous layers.

The capillary adhesion technique: a versatile method for determining the liquid adhesion force and sample stiffness

PubMed Central

Gandyra, Daniel; Gorb, Stanislav; Barthlott, Wilhelm

2015-01-01

Summary We report a novel, practical technique for the concerted, simultaneous determination of both the adhesion force of a small structure or structural unit (e.g., an individual filament, hair, micromechanical component or microsensor) to a liquid and its elastic properties. The method involves the creation and development of a liquid meniscus upon touching a liquid surface with the structure, and the subsequent disruption of this liquid meniscus upon removal. The evaluation of the meniscus shape immediately before snap-off of the meniscus allows the quantitative determination of the liquid adhesion force. Concurrently, by measuring and evaluating the deformation of the structure under investigation, its elastic properties can be determined. The sensitivity of the method is remarkably high, practically limited by the resolution of the camera capturing the process. Adhesion forces down to 10 µN and spring constants up to 2 N/m were measured. Three exemplary applications of this method are demonstrated: (1) determination of the water adhesion force and the elasticity of individual hairs (trichomes) of the floating fern Salvinia molesta. (2) The investigation of human head hairs both with and without functional surface coatings (a topic of high relevance in the field of hair cosmetics) was performed. The method also resulted in the measurement of an elastic modulus (Young’s modulus) for individual hairs of 3.0 × 105 N/cm2, which is within the typical range known for human hair. (3) Finally, the accuracy and validity of the capillary adhesion technique was proven by examining calibrated atomic force microscopy cantilevers, reproducing the spring constants calibrated using other methods. PMID:25671147

Effects of strain rate, mixing ratio, and stress-strain definition on the mechanical behavior of the polydimethylsiloxane (PDMS) material as related to its biological applications.

PubMed

Khanafer, Khalil; Duprey, Ambroise; Schlicht, Marty; Berguer, Ramon

2009-04-01

Tensile tests on Polydimethylsiloxane (PDMS) materials were conducted to illustrate the effects of mixing ratio, definition of the stress-strain curve, and the strain rate on the elastic modulus and stress-strain curve. PDMS specimens were prepared according to the ASTM standards for elastic materials. Our results indicate that the physiological elastic modulus depends strongly on the definition of the stress-strain curve, mixing ratio, and the strain rate. For various mixing ratios and strain rates, true stress-strain definition results in higher stress and elastic modulus compared with engineering stress-strain and true stress-engineering strain definitions. The elastic modulus increases as the mixing ratio increases up-to 9:1 ratio after which the elastic modulus begins to decrease even as the mixing ratio continues to increase. The results presented in this study will be helpful to assist the design of in vitro experiments to mimic blood flow in arteries and to understand the complex interaction between blood flow and the walls of arteries using PDMS elastomer.

Modulus of Elasticity and Thermal Expansion Coefficient of ITO Film

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

Carter, Austin D.; Elhadj, S.

2016-06-24

The purpose of this experiment was to determine the modulus of elasticity (E) and thermal expansion coefficient (α) of RF sputtered Indium Tin Oxide (ITO) as a function of temperature (T), and to collect ITO film stress data. In order to accomplish that goal, the Toho FLX-2320-S thin film stress measurement machine was used to collect both single stress and stress-temperature data for ITO coated fused silica and sapphire substrates. The stress measurement function of the FLX-2320-S cannot be used to calculate the elastic modulus of the film because the Stoney formula incorporates the elastic modulus of the substrate, rathermore » than of the film itself.« less

ELASTICITY, DOUBLE REFRACTION AND SWELLING OF ISOELECTRIC GELATIN

PubMed Central

Kunitz, M.

1930-01-01

Quincke's researches (1904) have demonstrated that when a 20 per cent gelatin gel is allowed to swell in water it gives rise to positive double refraction, as if the gel were under tensile stresses. If, on the other hand, the gel shrinks on being placed in alcohol it becomes negatively double refractive, as if it were compressed. But the double refraction as found by Quincke lasts only during the process of swelling or shrinking, and disappears as soon as the gel reaches a state of equilibrium. This phenomenon was investigated here and it was found that the reason for the disappearance of the double refraction is due to the fact that at equilibrium the percentage change in the size of a gel is equal in all three dimensions and the strain is therefore uniform. Double refraction persists as long as there is a difference in the elastic strain in the three dimensions of the strained material. It was found that when gels are cast on glass slides or in glass frames, so as to prevent swelling in certain directions, the double refraction produced by swelling at 6°C. persists permanently in the gel as long as it is swollen, and is proportional to the percentage change in the linear dimensions of the gel. Gels made up of various concentrations of isoelectric gelatin of less than 10 per cent when placed in dilute buffer of the same pH as that of the isoelectric point of the gelatin shrink and give rise to negative double refraction, while gels of concentrations of more than 10 per cent swell and give rise to positive double refraction. The double refraction produced in either case when divided by the percentage change in the dimensions of the gel and by its changed concentration gives a constant value both for swelling and shrinking. This constant which stands for the double refraction produced in a gel of unit concentration per unit strain is termed here the optical modulus of elasticity since it is proportional to the internal elastic stress in the swollen gelatin. It was found that the optical modulus of elasticity is the same both for gels cast on slides and in frames, although the mode of swelling is different in the two forms of gels. Gels removed from their glass supports after apparent swelling equilibrium, when placed in dilute buffer, begin to swell gradually in all three dimensions and the double refraction decreases slowly, though it persists for a long time. But the double refraction per unit change in dimension and per unit concentration still remains the same as before, thus proving that the internal elastic stress as indicated by the double refraction is brought about by the resistance of the gel itself to deformation. A study was also made on the effect of salts, acid and base on the double refraction of a 10 per cent gel during swelling. The experiments show that below M/8 salts affect very slightly the optical modulus of elasticity of the gel. At higher concentrations of salts the elasticity of the gel is reduced by some salts and increased by others, while such salts as sodium acetate and sodium and ammonium sulfates do not change the elasticity of the gels at all during swelling. The investigated salts may thus be arranged in this respect in the following approximate series: CaCl2, NaI, NaSCN, NaBr, AlCl3, NaCl, Na acetate, Na2SO4, (NH4)2SO4, Al2SO4 and MgSO4. The first five in the series decrease the elasticity while the last two in the series increase the elasticity of the gels during swelling. Acids and bases in higher concentrations exert a powerful influence on the reduction of the elasticity of the gel but in the range of pH between 2.0 and 10.0 the elasticity remains unaffected. The general conclusions to be drawn from these studies are as follows: 1. Swelling or shrinking produces elastic stresses in gels of gelatin, tensile in the first case and compressive in the second case, both being proportional to the percentage change in the dimensions of the gel. 2. Unsupported gels when immersed in aqueous solutions swell or shrink in such a manner that at equilibrium the percentage change in size is equal in all three dimensions, and the stresses become equalized throughout the gel. 3. Gels cast on glass slides or in frames when immersed in aqueous solutions swell or shrink mostly in one direction, and give rise to unidirectional stresses that can be determined accurately by measuring the double refraction produced. 4. The modulus of elasticity of swelling gelatin gels, as calculated from the double refraction measurements, is the same both for compression and for tension and is proportional to the concentration of gelatin in the gel. 5. The modulus of elasticity of gels during swelling is affected only slightly or not at all by salts at concentrations of less than M/8 and is independent of the pH in the range approximately between 2.0 and 10.0. 6. Higher concentrations of salts affect the modulus of elasticity of gelatin gels and the salts in their effectiveness may be arranged in a series similar to the known Hoffmeister series. 7. Acid and alkali have a strong reducing influence on the elastic modulus of swelling gels. 8. The swelling produced in isoelectric gelatin by salts is due primarily to a change brought about by the salts in the osmotic forces in the gel, but in high concentrations of some salts the swelling is increased by the influence of the salt on the elasticity of the gel. This agrees completely with the theory of swelling of isoelectric gelatin as developed by Northrop and the writer in former publications. 9. The studies of Loeb and the writer on the effect of salts on swelling of gelatin in acid and alkali have been in the range of concentrations of salts where the modulus of elasticity of the gelatin is practically constant, and the specific effect of the various salts has been negligible as compared with the effect of the valency of the ions. In concentrations of salts below M/4 or M/8 the Hoffmeister series plays no rôle. PMID:19872548

Cell wall elasticity: I. A critique of the bulk elastic modulus approach and an analysis using polymer elastic principles

NASA Technical Reports Server (NTRS)

Wu, H. I.; Spence, R. D.; Sharpe, P. J.; Goeschl, J. D.

1985-01-01

The traditional bulk elastic modulus approach to plant cell pressure-volume relations is inconsistent with its definition. The relationship between the bulk modulus and Young's modulus that forms the basis of their usual application to cell pressure-volume properties is demonstrated to be physically meaningless. The bulk modulus describes stress/strain relations of solid, homogeneous bodies undergoing small deformations, whereas the plant cell is best described as a thin-shelled, fluid-filled structure with a polymer base. Because cell walls possess a polymer structure, an alternative method of mechanical analysis is presented using polymer elasticity principles. This initial study presents the groundwork of polymer mechanics as would be applied to cell walls and discusses how the matrix and microfibrillar network induce nonlinear stress/strain relationships in the cell wall in response to turgor pressure. In subsequent studies, these concepts will be expanded to include anisotropic expansion as regulated by the microfibrillar network.

Elastic Properties and Internal Friction of Two Magnesium Alloys at Elevated Temperatures

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

Freels, M.; Liaw, P. K.; Garlea, E.

2011-06-01

The elastic properties and internal friction of two magnesium alloys were studied from 25 C to 450 C using Resonant Ultrasound Spectroscopy (RUS). The Young's moduli decrease with increasing temperature. At 200 C, a change in the temperature dependence of the elastic constants is observed. The internal friction increases significantly with increasing temperature above 200 C. The observed changes in the temperature dependence of the elastic constants and the internal friction are the result of anelastic relaxation by grain boundary sliding at elevated temperatures. Elastic properties govern the behavior of a materials subjected to stress over a region of strainmore » where the material behaves elastically. The elastic properties, including the Young's modulus (E), shear modulus (G), bulk modulus (B), and Poisson's ratio (?), are of significant interest to many design and engineering applications. The choice of the most appropriate material for a particular application at elevated temperatures therefore requires knowledge of its elastic properties as a function of temperature. In addition, mechanical vibration can cause significant damage in the automotive, aerospace, and architectural industries and thus, the ability of a material to dissipate elastic strain energy in materials, known as damping or internal friction, is also important property. Internal friction can be the result of a wide range of physical mechanisms, and depends on the material, temperature, and frequency of the loading. When utilized effectively in engineering applications, the damping capacity of a material can remove undesirable noise and vibration as heat to the surroundings. The elastic properties of materials can be determined by static or dynamic methods. Resonant Ultrasound Spectroscopy (RUS), used in this study, is a unique and sophisticated non-destructive dynamic technique for determining the complete elastic tensor of a solid by measuring the resonant spectrum of mechanical resonance for a sample of known geometry, dimensions, and mass. In addition, RUS allows determination of internal friction, or damping, at different frequencies and temperatures. Polycrystalline pure magnesium (Mg) exhibits excellent high damping properties. However, the poor mechanical properties limit the applications of pure Mg. Although alloying can improve the mechanical properties of Mg, the damping properties are reduced with additions of alloying elements. Therefore, it becomes necessary to study and develop Mg-alloys with simultaneous high damping capacity and improved mechanical properties. Moreover, studies involving the high temperature dynamic elastic properties of Mg alloys are limited. In this study, the elastic properties and internal friction of two magnesium alloys were studied at elevated temperatures using RUS. The effect of alloy composition and grain size was investigated. The wrought magnesium alloys AZ31 and ZK60 were employed. Table 1 gives the nominal chemical compositions of these two alloys. The ZK60 alloy is a commercial extruded plate with a T5 temper, i.e. solution-treated at 535 C for two hours, quenched in hot water, and aged at 185 C for 24 hours. The AZ31 alloy is a commercial rolled plate with a H24 temper, i.e. strain hardened and partially annealed.« less

Inverse finite element methods for extracting elastic-poroviscoelastic properties of cartilage and other soft tissues from indentation

NASA Astrophysics Data System (ADS)

Namani, Ravi

Mechanical properties are essential for understanding diseases that afflict various soft tissues, such as osteoarthritic cartilage and hypertension which alters cardiovascular arteries. Although the linear elastic modulus is routinely measured for hard materials, standard methods are not available for extracting the nonlinear elastic, linear elastic and time-dependent properties of soft tissues. Consequently, the focus of this work is to develop indentation methods for soft biological tissues; since analytical solutions are not available for the general context, finite element simulations are used. First, parametric studies of finite indentation of hyperelastic layers are performed to examine if indentation has the potential to identify nonlinear elastic behavior. To answer this, spherical, flat-ended conical and cylindrical tips are examined and the influence of thickness is exploited. Also the influence of the specimen/substrate boundary condition (slip or non-slip) is clarified. Second, a new inverse method---the hyperelastic extraction algorithm (HPE)---was developed to extract two nonlinear elastic parameters from the indentation force-depth data, which is the basic measurement in an indentation test. The accuracy of the extracted parameters and the influence of noise in measurements on this accuracy were obtained. This showed that the standard Berkovitch tip could only extract one parameter with sufficient accuracy, since the indentation force-depth curve has limited sensitivity to both nonlinear elastic parameters. Third, indentation methods for testing tissues from small animals were explored. New methods for flat-ended conical tips are derived. These account for practical test issues like the difficulty in locating the surface or soft specimens. Also, finite element simulations are explored to elucidate the influence of specimen curvature on the indentation force-depth curve. Fourth, the influence of inhomogeneity and material anisotropy on the extracted "average" linear elastic modulus was studied. The focus here is on murine tibial cartilage, since recent experiments have shown that the modulus measured by a 15 mum tip is considerably larger than that obtained from a 90 mum tip. It is shown that a depth-dependent modulus could give rise to such a size effect. Lastly, parametric studies were performed within the small strain setting to understand the influence of permeability and viscoelastic properties on the indentation stress-relaxation response. The focus here is on cartilage, and specific test protocols (single-step vs. multi-step stress relaxation) are explored. An inverse algorithm was developed to extract the poroviscoelastic parameters. A sensitivity study using this algorithm shows that the instantaneous elastic modulus (which is a measure of the viscous relaxation) can be extracted with very good accuracy, but the permeability and long-time relaxation constant cannot be extracted with good accuracy. The thesis concludes with implications of these studies. The potential and limitations of indentation tests for studying cartilage and other soft tissues is discussed.

Abnormal elastic modulus behavior in a crystalline-amorphous core-shell nanowire system.

PubMed

Lee, Jeong Hwan; Choi, Su Ji; Kwon, Ji Hwan; Van Lam, Do; Lee, Seung Mo; Kim, An Soon; Baik, Hion Suck; Ahn, Sang Jung; Hong, Seong Gu; Yun, Yong Ju; Kim, Young Heon

2018-06-13

We investigated the elastic modulus behavior of crystalline InAs/amorphous Al2O3 core-shell heterostructured nanowires with shell thicknesses varying between 10 and 90 nm by conducting in situ tensile tests inside a transmission electron microscope (TEM). Counterintuitively, the elastic modulus behaviors of InAs/Al2O3 core-shell nanowires differ greatly from those of bulk-scale composite materials, free from size effects. According to our results, the elastic modulus of InAs/Al2O3 core-shell nanowires increases, peaking at a shell thickness of 40 nm, and then decreases in the range of 50-90 nm. This abnormal behavior is attributed to the continuous decrease in the elastic modulus of the Al2O3 shell as the thickness increases, which is caused by changes in the atomic/electronic structure during the atomic layer deposition process and the relaxation of residual stress/strain in the shell transferred from the interfacial mismatch between the core and shell materials. A novel method for estimating the elastic modulus of the shell in a heterostructured core-shell system was suggested by considering these two effects, and the predictions from the suggested method coincided well with the experimental results. We also found that the former and latter effects account for 89% and 11% of the change in the elastic modulus of the shell. This study provides new insight by showing that the size dependency, which is caused by the inhomogeneity of the atomic/electronic structure and the residual stress/strain, must be considered to evaluate the mechanical properties of heterostructured nanowires.

Nanostructure and elastic modulus of single trabecula in bovine cancellous bone.

PubMed

Yamada, Satoshi; Tadano, Shigeru; Fukuda, Sakurako

2014-11-07

We aimed to investigate the elastic modulus of trabeculae using tensile tests and assess the effects of nanostructure at the hydroxyapatite (HAp) crystal scale on the elastic modulus. In the experiments, 18 trabeculae that were at least 3mm in length in the proximal epiphysis of three adult bovine femurs were used. Tensile tests were conducted using a small tensile testing device coupled with microscopy under air-dried condition. The c-axis orientation of HAp crystals and the degree of orientation were measured by X-ray diffraction. To observe the deformation behavior of HAp crystals under tensile loading, the same tensile tests were conducted in X-ray diffraction measurements. The mineral content of specimens was evaluated using energy dispersive X-ray spectrometry. The elastic modulus of a single trabecula varied from 4.5 to 23.6 GPa, and the average was 11.5 ± 5.0 GPa. The c-axis of HAp crystals was aligned with the trabecular axis and the crystals were lineally deformed under tensile loading. The ratio of the HAp crystal strain to the tissue strain (strain ratio) had a significant correlation with the elastic modulus (r=0.79; P<0.001). However, the mineral content and the degree of orientation did not vary widely and did not correlate with the elastic modulus in this study. It suggests that the strain ratio may represent the nanostructure of a single trabecula and would determine the elastic modulus as well as mineral content and orientation. Copyright © 2014 Elsevier Ltd. All rights reserved.

Structural, electronic, mechanical, and thermoelectric properties of a novel half Heusler compound HfPtPb

NASA Astrophysics Data System (ADS)

Kaur, Kulwinder; Rai, D. P.; Thapa, R. K.; Srivastava, Sunita

2017-07-01

We explore the structural, electronic, mechanical, and thermoelectric properties of a new half Heusler compound HfPtPb, an all metallic heavy element, recently proposed to be stable [Gautier et al., Nat. Chem. 7, 308 (2015)]. In this work, we employ density functional theory and semi-classical Boltzmann transport equations with constant relaxation time approximation. The mechanical properties, such as shear modulus, Young's modulus, elastic constants, Poisson's ratio, and shear anisotropy factor, have been investigated. The elastic and phonon properties reveal that this compound is mechanically and dynamically stable. Pugh's ratio and Frantsevich's ratio demonstrate its ductile behavior, and the shear anisotropic factor reveals the anisotropic nature of HfPtPb. The band structure predicts this compound to be a semiconductor with a band gap of 0.86 eV. The thermoelectric transport parameters, such as Seebeck coefficient, electrical conductivity, electronic thermal conductivity, and lattice thermal conductivity, have been calculated as a function of temperature. The highest value of Seebeck coefficient is obtained for n-type doping at an optimal carrier concentration of 1.0 × 1020 e/cm3. We predict the maximum value of figure of merit (0.25) at 1000 K. Our investigation suggests that this material is an n-type semiconductor.

Internally Consistent Single-Crystal Elasticity of (Mg0.89Fe0.11)2SiO4 Wadsleyite at High Pressures and High Temperatures

NASA Astrophysics Data System (ADS)

Buchen, J.; Marquardt, H.; Kurnosov, A.; Boffa Ballaran, T.; Speziale, S.; Kawazoe, T.

2016-12-01

The transition zone in Earth's upper mantle attains a pivotal role in deep Earth dynamics. Various scenarios for the fate of subducted lithospheric slabs have been identified from seismic tomographic images while petrological observations point to potential reservoirs of volatile elements in the transition zone. Among the mineral phases expected to assemble a mantle rock at depths between 410 km and 520 km, wadsleyite stands out with a remarkable hydrogen storage capacity of several weight percent H2O, a volume fraction of about 60 % for a pyrolitic mantle composition, and the potential to cause seismic anisotropy. Interpretations of seismological observations in terms of the thermal and mineralogical state of the upper transition zone rely on the elastic properties of wadsleyite at the prevailing conditions of pressure and temperature including its elastic anisotropy. We have determined internally consistent single-crystal elastic constants for wadsleyite with a relevant composition ((Mg0.89Fe0.11)1.98H0.04SiO4, 0.25(3) wt-% H2O) up to a pressure of 16 GPa at room temperature and conducted first measurements at combined high pressures and high temperatures. Single-crystal segments were cut from oriented thin sections with a focused ion beam and complementary orientations loaded together into the same pressure chamber of resistively heated diamond anvil cells. Using this two-sample approach and a combination of Brillouin spectroscopy and single-crystal X-ray diffraction, all nine independent elastic constants can be obtained under consistent conditions of pressure and temperature. Comparison of our room temperature results with those reported for wadsleyites with different iron contents suggests a very small effect of Fe-Mg substitution on the bulk modulus while the shear modulus decreases with increasing iron content. This differential effect of iron on the elastic moduli bears the potential to be seismically distinguishable from the signatures of temperature or other chemical substituents like volatile elements. The two-sample approach is currently being extended to four crystal segments to directly quantify the effect of hydrogen incorporation on the elastic behavior of iron-bearing wadsleyite.

Random field assessment of nanoscopic inhomogeneity of bone

PubMed Central

Dong, X. Neil; Luo, Qing; Sparkman, Daniel M.; Millwater, Harry R.; Wang, Xiaodu

2010-01-01

Bone quality is significantly correlated with the inhomogeneous distribution of material and ultrastructural properties (e.g., modulus and mineralization) of the tissue. Current techniques for quantifying inhomogeneity consist of descriptive statistics such as mean, standard deviation and coefficient of variation. However, these parameters do not describe the spatial variations of bone properties. The objective of this study was to develop a novel statistical method to characterize and quantitatively describe the spatial variation of bone properties at ultrastructural levels. To do so, a random field defined by an exponential covariance function was used to present the spatial uncertainty of elastic modulus by delineating the correlation of the modulus at different locations in bone lamellae. The correlation length, a characteristic parameter of the covariance function, was employed to estimate the fluctuation of the elastic modulus in the random field. Using this approach, two distribution maps of the elastic modulus within bone lamellae were generated using simulation and compared with those obtained experimentally by a combination of atomic force microscopy and nanoindentation techniques. The simulation-generated maps of elastic modulus were in close agreement with the experimental ones, thus validating the random field approach in defining the inhomogeneity of elastic modulus in lamellae of bone. Indeed, generation of such random fields will facilitate multi-scale modeling of bone in more pragmatic details. PMID:20817128

An analytical model for transient deformation of viscoelastically coated beams: Applications to static-mode microcantilever chemical sensors

NASA Astrophysics Data System (ADS)

Heinrich, S. M.; Wenzel, M. J.; Josse, F.; Dufour, I.

2009-06-01

The problem governing the transient deformation of an elastic cantilever beam with viscoelastic coating, subjected to a time-dependent coating eigenstrain, is mathematically formulated. An analytical solution for an exponential eigenstrain history, exact within the context of beam theory, is obtained in terms of the coating and base layer thicknesses, the elastic modulus of the base material, the initial coating modulus, the coating relaxation percentage (0%-100%), and the time constants of the coating's relaxation process and its eigenstrain history. Approximate formulas, valid for thin coatings, are derived as special cases to provide insight into system behavior. Main results include (1) the time histories of the beam curvature and the coating stresses, (2) a criterion governing the response type (monotonic or "overshoot" response), and (3) simple expressions for the overshoot ratio, defined as the peak response scaled by the steady-state response, and the time at which the peak response occurs. Applications to polymer-coated microcantilever-based chemical sensors operating in the static mode are discussed.

The elastic stability, bifurcation and ideal strength of gold under hydrostatic stress: an ab initio calculation.

PubMed

Wang, Hao; Li, Mo

2009-11-11

In this paper, we employ an ab initio density functional theory calculation to investigate the elastic stability of face-centered cubic Au under hydrostatic deformation. We identify the elastic stiffness constant B(ijkl) as the coefficient in the stress-strain relation for an arbitrary deformed state, and use it to test the stability condition. We show that this criterion bears the same physics as that proposed earlier by Frenkel and Orowan and agrees with the Born-Hill criterion. The results from those two approaches agree well with each other. We show that the stability limit, or instability, of the perfect Au crystal under hydrostatic expansion is not associated with the bulk stiffness modulus as predicted in the previous work; rather it is caused by a shear instability associated with the vanishing rhombohedral shear stiffness modulus. The deviation of the deformation mode from the primary hydrostatic loading path signals a bifurcation or symmetry breaking in the ideal crystal. The corresponding ideal hydrostatic strength for Au is 19.2 GPa at the Lagrangian expansion strain of ∼0.06. In the case of compression, Au remains stable over the entire pressure range in our calculation.

Variability of Young’s modulus and Poisson’s ratio of hexagonal crystals

NASA Astrophysics Data System (ADS)

Komarova, M. A.; Gorodtsov, V. A.; Lisovenko, D. S.

2018-04-01

In this paper, the variability of elastic characteristics (Young’s modulus and Poisson’s ratio) of hexagonal crystals has been studied. Analytic expressions for Young’s modulus and Poisson’s ratio are obtained. Stationary values for these elastic characteristics are found. Young’s modulus has three stationary values, and Poisson’s ratio has eight stationary values. Numerical analysis of these elastic characteristics for hexagonal crystals is given based on the experimental data from the Landolt-Börnstein handbook. Global extrema of Young’s modulus and Poisson’s ratio for hexagonal crystals are found. Crystals are found in which the maximum values exceeds the upper limit for isotropic materials.

Insufficiency of the Young’s modulus for illustrating the mechanical behavior of GaN nanowires

NASA Astrophysics Data System (ADS)

Zamani Kouhpanji, Mohammad Reza; Behzadirad, Mahmoud; Feezell, Daniel; Busani, Tito

2018-05-01

We use a non-classical modified couple stress theory including the acceleration gradients (MCST-AG), to precisely demonstrate the size dependency of the mechanical properties of gallium nitride (GaN) nanowires (NWs). The fundamental elastic constants, Young’s modulus and length scales of the GaN NWs were estimated both experimentally, using a novel experimental technique applied to atomic force microscopy, and theoretically, using atomic simulations. The Young’s modulus, static and the dynamic length scales, calculated with the MCST-AG, were found to be 323 GPa, 13 and 14.5 nm, respectively, for GaN NWs from a few nanometers radii to bulk radii. Analyzing the experimental data using the classical continuum theory shows an improvement in the experimental results by introducing smaller error. Using the length scales determined in MCST-AG, we explain the inconsistency of the Young’s moduli reported in recent literature, and we prove the insufficiency of the Young’s modulus for predicting the mechanical behavior of GaN NWs.

Insufficiency of the Young's modulus for illustrating the mechanical behavior of GaN nanowires.

PubMed

Kouhpanji, Mohammad Reza Zamani; Behzadirad, Mahmoud; Feezell, Daniel; Busani, Tito

2018-05-18

We use a non-classical modified couple stress theory including the acceleration gradients (MCST-AG), to precisely demonstrate the size dependency of the mechanical properties of gallium nitride (GaN) nanowires (NWs). The fundamental elastic constants, Young's modulus and length scales of the GaN NWs were estimated both experimentally, using a novel experimental technique applied to atomic force microscopy, and theoretically, using atomic simulations. The Young's modulus, static and the dynamic length scales, calculated with the MCST-AG, were found to be 323 GPa, 13 and 14.5 nm, respectively, for GaN NWs from a few nanometers radii to bulk radii. Analyzing the experimental data using the classical continuum theory shows an improvement in the experimental results by introducing smaller error. Using the length scales determined in MCST-AG, we explain the inconsistency of the Young's moduli reported in recent literature, and we prove the insufficiency of the Young's modulus for predicting the mechanical behavior of GaN NWs.

Measurement of Shear Elastic Moduli in Quasi-Incompressible Soft Solids

NASA Astrophysics Data System (ADS)

Rénier, Mathieu; Gennisson, Jean-Luc; Barrière, Christophe; Catheline, Stefan; Tanter, Mickaël; Royer, Daniel; Fink, Mathias

2008-06-01

Recently a nonlinear equation describing the plane shear wave propagation in isotropic quasi-incompressible media has been developed using a new expression of the strain energy density, as a function of the second, third and fourth order shear elastic constants (respectively μ, A, D) [1]. In such a case, the shear nonlinearity parameter βs depends only from these last coefficients. To date, no measurement of the parameter D have been carried out in soft solids. Using a set of two experiments, acoustoelasticity and finite amplitude shear waves, the shear elastic moduli up to the fourth order of soft solids are measured. Firstly, this theoretical background is applied to the acoustoelasticity theory, giving the variations of the shear wave speed as a function of the stress applied to the medium. From such variations, both linear (μ) and third order shear modulus (A) are deduced in agar-gelatin phantoms. Experimentally the radiation force induced by a focused ultrasound beam is used to generate quasi-plane linear shear waves within the medium. Then the shear wave propagation is imaged with an ultrafast ultrasound scanner. Secondly, in order to give rise to finite amplitude plane shear waves, the radiation force generation technique is replaced by a vibrating plate applied at the surface of the phantoms. The propagation is also imaged using the same ultrafast scanner. From the assessment of the third harmonic amplitude, the nonlinearity parameter βS is deduced. Finally, combining these results with the acoustoelasticity experiment, the fourth order modulus (D) is deduced. This set of experiments provides the characterization, up to the fourth order, of the nonlinear shear elastic moduli in quasi-incompressible soft media. Measurements of the A moduli reveal that while the behaviors of both soft solids are close from a linear point of view, the corresponding nonlinear moduli A are quite different. In a 5% agar-gelatin phantom, the fourth order elastic constant D is found to be 30±10 kPa.

Study on property and stability mechanism of LAB-AEO-4 system

NASA Astrophysics Data System (ADS)

Song, Kaifei; Ge, Jijiang; Wang, Yang; Zhang, Guicai; Jiang, Ping

2017-04-01

The behaviors of binary blending systems of fatty alcohol polyoxyethylene ether (AEO-4) blended with the laurel amide betaine (LAB) was investigated at 80°C,the results indicated that the optimal ratio of the mixed system of LAB-AEO-4 was 5:2. The stability mechanism of LAB-AEO-4 system was analyzed from three aspects of dynamic surface tension,gas permeation rate and surface rheology.The results showed that the tension of mixed system was easier to achieve balance,the constant of gas permeation rate of the mixed system decreased by about 7% and the elastic modulus and dilational modulus increased by about 2 times compared with the single LAB system.

Electronic and mechanical properties of ZnX (X = S, Se and Te)—An ab initio study

NASA Astrophysics Data System (ADS)

Verma, Ajay Singh; Sharma, Sheetal; Sarkar, Bimal Kumar; Jindal, Vijay Kumar

2011-12-01

Zinc chalcogenides (ZnX, X = S, Se and Te) have been increasing attention as wide and direct band gap semiconductor for blue and ultraviolet optical devices. This paper analyzes electronic and mechanical properties of these materials by ab initio pseudo-potential method that uses non conserving pseudopotentials in fully nonlocal form, as implemented in SIESTA code. In this approach the local density approximation (LDA) is used for the exchange-correlation (XC) potential. The calculations are given for band gap, elastic constants (C11, C12 and C44), shear modulus, and Young's modulus. The results are in very good agreement with previous theoretical calculations and available experimental data.

Elastic modulus of nanomaterials: resonant contact-AFM measurement and reduced-size effects (Invited Paper)

NASA Astrophysics Data System (ADS)

Nysten, Bernard; Fretigny, Christian; Cuenot, Stephane

2005-05-01

Resonant contact atomic force microscopy (resonant C-AFM) is used to quantitatively measure the elastic modulus of polymer nanotubes and metallic nanowires. To achieve this, an oscillating electric field is applied between the sample holder and the microscope head to excite the oscillation of the cantilever in contact with the nanostructures suspended over the pores of a membrane. The resonance frequency of the cantilever with the tip in contact with a nanostructure is shifted to higher values with respect to the resonance frequency of the free cantilever. It is demonstrated that the system can simply be modeled by a cantilever with the tip in contact with two springs. The measurement of the frequency shift enables the direct determination of the spring stiffness, i.e. the nanowires or nanotube stiffness. The method also enables the determination of the boundary conditions of the nanobeam on the membrane. The tensile elastic modulus is then simply determined using the classical theory of beam deflection. The obtained results for the larger nanostructures fairly agree to the values reported in the literature for the macroscopic elastic modulus of the corresponding materials. The measured modulus of the nanomaterials with smaller diameters is significantly higher than that of the larger ones. The increase of the apparent elastic modulus for the smaller diameters is attributed to the surface tension effects. It is thus demonstrated that resonant C-AFM enables the measurement of the elastic modulus and of the surface tension of nanomaterials.

Structural, Electronic, and Thermodynamic Properties of Tetragonal t-SixGe3−xN4

PubMed Central

Han, Chenxi; Chai, Changchun; Fan, Qingyang; Yang, Jionghao; Yang, Yintang

2018-01-01

The structural, mechanical, anisotropic, electronic, and thermal properties of t-Si3N4, t-Si2GeN4, t-SiGe2N4, and t-Ge3N4 in the tetragonal phase are systematically investigated in the present work. The mechanical stability is proved by the elastic constants of t-Si3N4, t-Si2GeN4, t-SiGe2N4, and t-Ge3N4. Moreover, they all demonstrate brittleness, because B/G < 1.75, and v < 0.26. The elastic anisotropy of t-Si3N4, t-Si2GeN4, t-SiGe2N4, and t-Ge3N4 is characterized by Poisson’s ratio, Young’s modulus, the percentage of elastic anisotropy for bulk modulus AB, the percentage of elastic anisotropy for shear modulus AG, and the universal anisotropic index AU. The electronic structures of t-Si3N4, t-Si2GeN4, t-SiGe2N4, and t-Ge3N4 are all wide band gap semiconductor materials, with band gaps of 4.26 eV, 3.94 eV, 3.83 eV, and 3.25 eV, respectively, when using the Heyd-Scuseria-Ernzerhof (HSE06) hybrid functional. Moreover, t-Ge3N4 is a quasi-direct gap semiconductor material. The thermodynamic properties of t-Si3N4, t-Si2GeN4, t-SiGe2N4, and t-Ge3N4 are investigated utilizing the quasi-harmonic Debye model. The effects of temperature and pressure on the thermal expansion coefficient, heat capacity, Debye temperature, and Grüneisen parameters are discussed in detail. PMID:29518943

Mechanical modeling and characteristic study for the adhesive contact of elastic layered media

NASA Astrophysics Data System (ADS)

Zhang, Yuyan; Wang, Xiaoli; Tu, Qiaoan; Sun, Jianjun; Ma, Chenbo

2017-11-01

This paper investigates the adhesive contact between a smooth rigid sphere and a smooth elastic layered medium with different layer thicknesses, layer-to-substrate elastic modulus ratios and adhesion energy ratios. A numerical model is established by combining elastic responses of the contact system and an equation of equivalent adhesive contact pressure which is derived based on the Hamaker summation method and the Lennard-Jones intermolecular potential law. Simulation results for hard layer cases demonstrate that variation trends of the pull-off force with the layer thickness and elastic modulus ratio are complex. On one hand, when the elastic modulus ratio increases, the pull-off force decreases at smaller layer thicknesses, decreases at first and then increases at middle layer thicknesses, while increases monotonously at larger layer thicknesses. On the other hand, the pull-off force decreases at first and then increases with the increase in the layer thickness. Furthermore, a critical layer thickness above which the introduction of hard layer cannot reduce adhesion and an optimum layer thickness under which the pull-off force reaches a minimum are found. Both the critical and optimum layer thicknesses become larger with an increase in the Tabor parameter, while they tend to decrease with the increase in the elastic modulus ratio. In addition, the pull-off force increases sublinearly with the adhesion energy ratio if the layer thickness and elastic modulus ratio are fixed.

Quantitative estimation of muscle shear elastic modulus of the upper trapezius with supersonic shear imaging during arm positioning.

PubMed

Leong, Hio-Teng; Ng, Gabriel Yin-Fat; Leung, Vivian Yee-Fong; Fu, Siu Ngor

2013-01-01

Pain and tenderness of the upper trapezius are the major complaints among people with chronic neck and shoulder disorders. Hyper-activation and increased muscle tension of the upper trapezius during arm elevation will cause imbalance of the scapular muscle force and contribute to neck and shoulder disorders. Assessing the elasticity of the upper trapezius in different arm positions is therefore important for identifying people at risk so as to give preventive programmes or for monitoring the effectiveness of the intervention programmes for these disorders. This study aimed to establish the reliability of supersonic shear imaging (SSI) in quantifying upper trapezius elasticity/shear elastic modulus and its ability to measure the modulation of muscle elasticity during arm elevation. Twenty-eight healthy adults (15 males, 13 females; mean age = 29.6 years) were recruited to participate in the study. In each participant, the shear elastic modulus of the upper trapezius while the arm was at rest and at 30° abduction was measured by two operators and twice by operator 1 with a time interval between the measurements. The results showed excellent within- and between-session intra-operator (ICC = 0.87-0.97) and inter-observer (ICC = 0.78-0.83) reliability for the upper trapezius elasticity with the arm at rest and at 30° abduction. An increase of 55.23% of shear elastic modulus from resting to 30° abduction was observed. Our findings demonstrate the possibilities for using SSI to quantify muscle elasticity and its potential role in delineating the modulation of upper trapezius elasticity, which is essential for future studies to compare the differences in shear elastic modulus between normal elasticity and that of individuals with neck and shoulder disorders.

Quantitative Estimation of Muscle Shear Elastic Modulus of the Upper Trapezius with Supersonic Shear Imaging during Arm Positioning

PubMed Central

Leong, Hio-Teng; Ng, Gabriel Yin-fat; Leung, Vivian Yee-fong; Fu, Siu Ngor

2013-01-01

Pain and tenderness of the upper trapezius are the major complaints among people with chronic neck and shoulder disorders. Hyper-activation and increased muscle tension of the upper trapezius during arm elevation will cause imbalance of the scapular muscle force and contribute to neck and shoulder disorders. Assessing the elasticity of the upper trapezius in different arm positions is therefore important for identifying people at risk so as to give preventive programmes or for monitoring the effectiveness of the intervention programmes for these disorders. This study aimed to establish the reliability of supersonic shear imaging (SSI) in quantifying upper trapezius elasticity/shear elastic modulus and its ability to measure the modulation of muscle elasticity during arm elevation. Twenty-eight healthy adults (15 males, 13 females; mean age = 29.6 years) were recruited to participate in the study. In each participant, the shear elastic modulus of the upper trapezius while the arm was at rest and at 30° abduction was measured by two operators and twice by operator 1 with a time interval between the measurements. The results showed excellent within- and between-session intra-operator (ICC = 0.87–0.97) and inter-observer (ICC = 0.78–0.83) reliability for the upper trapezius elasticity with the arm at rest and at 30° abduction. An increase of 55.23% of shear elastic modulus from resting to 30° abduction was observed. Our findings demonstrate the possibilities for using SSI to quantify muscle elasticity and its potential role in delineating the modulation of upper trapezius elasticity, which is essential for future studies to compare the differences in shear elastic modulus between normal elasticity and that of individuals with neck and shoulder disorders. PMID:23825641

First-principles investigation of structural, elastic, lattice dynamical and thermodynamic properties of lithium sulfur under pressure

NASA Astrophysics Data System (ADS)

Saib, S.; Bouarissa, N.

2017-10-01

In this study we report on the influence of hydrostatic pressure on structural, elastic, lattice dynamical and thermal properties of Li2S in the anti-fluorite structure using ab initio pseudopotential approach based on the density functional perturbation theory. Our results are found to be in good agreement with those existing in the literature. The present phonon dispersion spectra, dielectric constants and Born effective charges may be seen as the first investigation for the material under load. The pressure dependence of all features of interest has been examined and discussed. Besides, the temperature dependence of the lattice parameter and bulk modulus is predicted. The generalized elastic stability criteria showed that the material of interest is mechanically unstable for pressures beyond 55 GPa.

The synthesis and characterization of xerogel silica films for interlayer dielectric applications

NASA Astrophysics Data System (ADS)

Chow, Loren Anton

1999-11-01

Lowering the dielectric constant, k, of the interlayer dielectric in microprocessors leads to a decrease in power consumption, crosstalk between interconnects and RC time delay. Because of its low density, porous silica, as derived from the sol-gel process, has been widely praised as having the lowest dielectric constant of all viable "low-k" materials. Presented in this work are the results of an investigation featuring the synthesis and characterization of xerogel silica films. Synthesized were xerogel films derived from a tetrafanctional precursor. Such a material was found to be brittle and given to cracking and delamination during curing. it was found, however, that organic modification of the xerogel film led to a compliant material that remained crack-free throughout the curing process. This "hybrid" material filled 0.35 mum trenches without voids, cracks or delamination. The dielectric constant was found to be extremely sensitive to moisture. Although the moisture content was lower than that detectable by Fourier-transform infrared spectroscopy, the dielectric constant in ambient conditions was 80% higher than a dry film. The voltage breakdown was 3.4 MV/cm and the leakage current during bias temperature stressing (at 200 V and 200°C) was negligibly low. There was a critical film thickness at which the film cracked. This critical film thickness was dependent on the elastic constants of the substrate and the film. Because the strain energy released by the cracking film is commensurate with the compliance of the substrate, cracks formed preferentially in the <100> directions; that is, the directions of lowest substrate modulus. The critical thickness for the <100> direction for the hybrid film cured at 500°C was found to be 1.10 mum. Furthermore, it was found that cracks from the xerogel penetrated into the Si substrate to a depth of 0.8 mum. Using substrates of different elastic constants, the biaxial modulus and the coefficient of thermal expansion were found to be respectively 56 GPa and 2.11 x 10-6/°C. With knowledge of the biaxial modulus, the depth of cracking into the Si substrate and an assumption on Poisson's ratio, the critical crack energy release rate of the film was found to be 1.8 J/m2.

Random field assessment of nanoscopic inhomogeneity of bone.

PubMed

Dong, X Neil; Luo, Qing; Sparkman, Daniel M; Millwater, Harry R; Wang, Xiaodu

2010-12-01

Bone quality is significantly correlated with the inhomogeneous distribution of material and ultrastructural properties (e.g., modulus and mineralization) of the tissue. Current techniques for quantifying inhomogeneity consist of descriptive statistics such as mean, standard deviation and coefficient of variation. However, these parameters do not describe the spatial variations of bone properties. The objective of this study was to develop a novel statistical method to characterize and quantitatively describe the spatial variation of bone properties at ultrastructural levels. To do so, a random field defined by an exponential covariance function was used to represent the spatial uncertainty of elastic modulus by delineating the correlation of the modulus at different locations in bone lamellae. The correlation length, a characteristic parameter of the covariance function, was employed to estimate the fluctuation of the elastic modulus in the random field. Using this approach, two distribution maps of the elastic modulus within bone lamellae were generated using simulation and compared with those obtained experimentally by a combination of atomic force microscopy and nanoindentation techniques. The simulation-generated maps of elastic modulus were in close agreement with the experimental ones, thus validating the random field approach in defining the inhomogeneity of elastic modulus in lamellae of bone. Indeed, generation of such random fields will facilitate multi-scale modeling of bone in more pragmatic details. Copyright © 2010 Elsevier Inc. All rights reserved.

Anisotropy of the Mechanical Properties of TbF3 Crystals

NASA Astrophysics Data System (ADS)

Karimov, D. N.; Lisovenko, D. S.; Sizova, N. L.; Sobolev, B. P.

2018-01-01

TbF3 (sp. gr. Pnma) crystals up to 40 mm in diameter have been grown from melt by a Bridgman technique. The anisotropy of their mechanical properties is studied for the first time. the technical elasticity constants are calculated, and room-temperature values of Vickers microhardness for the (010) and (100) planes are measured. The shape of indentation impressions is found to correlate with Young's modulus anisotropy for TbF3 crystals.

Electronic, elastic and optical properties of divalent (R+2X) and trivalent (R+3X) rare earth monochalcogenides

NASA Astrophysics Data System (ADS)

Kumar, V.; Chandra, S.; Singh, J. K.

2017-08-01

Based on plasma oscillations theory of solids, simple relations have been proposed for the calculation of bond length, specific gravity, homopolar energy gap, heteropolar energy gap, average energy gap, crystal ionicity, bulk modulus, electronic polarizability and dielectric constant of rare earth divalent R+2X and trivalent R+3X monochalcogenides. The specific gravity of nine R+2X, twenty R+3X, and bulk modulus of twenty R+3X monochalcogenides have been calculated for the first time. The calculated values of all parameters are compared with the available experimental and the reported values. A fairly good agreement has been obtained between them. The average percentage deviation of two parameters: bulk modulus and electronic polarizability for which experimental data are known, have also been calculated and found to be better than the earlier correlations.

Correlation between macro- and nano-scopic measurements of carbon nanostructured paper elastic modulus

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

Omar, Yamila M.; Al Ghaferi, Amal, E-mail: aalghaferi@masdar.ac.ae, E-mail: mchiesa@masdar.ac.ae; Chiesa, Matteo, E-mail: aalghaferi@masdar.ac.ae, E-mail: mchiesa@masdar.ac.ae

2015-07-20

Extensive work has been done in order to determine the bulk elastic modulus of isotropic samples from force curves acquired with atomic force microscopy. However, new challenges are encountered given the development of new materials constructed of one-dimensional anisotropic building blocks, such as carbon nanostructured paper. In the present work, we establish a reliable framework to correlate the elastic modulus values obtained by amplitude modulation atomic force microscope force curves, a nanoscopic technique, with that determined by traditional macroscopic tensile testing. In order to do so, several techniques involving image processing, statistical analysis, and simulations are used to find themore » appropriate path to understand how macroscopic properties arise from anisotropic nanoscale components, and ultimately, being able to calculate the value of bulk elastic modulus.« less

A Finite Element Model to Predict the Effect of Porosity on Elastic Modulus in Low-Porosity Materials

NASA Astrophysics Data System (ADS)

Morrissey, Liam S.; Nakhla, Sam

2018-07-01

The effect of porosity on elastic modulus in low-porosity materials is investigated. First, several models used to predict the reduction in elastic modulus due to porosity are compared with a compilation of experimental data to determine their ranges of validity and accuracy. The overlapping solid spheres model is found to be most accurate with the experimental data and valid between 3 and 10 pct porosity. Next, a FEM is developed with the objective of demonstrating that a macroscale plate with a center hole can be used to model the effect of microscale porosity on elastic modulus. The FEM agrees best with the overlapping solid spheres model and shows higher accuracy with experimental data than the overlapping solid spheres model.

Measurement of the temperature dependence of Young's modulus of cartilage by phase-sensitive optical coherence elastography

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

Liu, C H; Li, J; Singh, M

2014-08-31

The development of an effective system to monitor the changes in the elastic properties of cartilage tissue with increasing temperature in laser reconstruction is an urgent practical task. In this paper, the use of phase-sensitive optical coherence elastography for detection of elastic waves in the sample has allowed Young's modulus of cartilage tissue to be measured directly during heating. Young's modulus was calculated from the group velocity of propagation of elastic waves excited by means of a system supplying focused air pulses. The measurement results are in agreement with the results of measurements of the modulus of elasticity under mechanicalmore » compression. The technique developed allows for noninvasive measurements; its development is promising for the use in vivo. (laser biophotonics)« less

Highly porous layers of silica nanospheres sintered by drying: scaling up of the elastic properties of the beads to the macroscopic mechanical properties.

PubMed

Lesaine, Arnaud; Bonamy, Daniel; Gauthier, Georges; Rountree, Cindy L; Lazarus, Véronique

2018-05-16

Layers obtained by drying a colloidal dispersion of silica spheres are found to be a good benchmark to test the elastic behaviour of porous media, in the challenging case of high porosities and nano-sized microstructures. Classically used for these systems, Kendall's approach explicitly considers the effect of surface adhesive forces onto the contact area between the particles. This approach provides the Young's modulus using a single adjustable parameter (the adhesion energy) but provides no further information on the tensorial nature and possible anisotropy of elasticity. On the other hand, homogenization approaches (e.g. rule of mixtures, and Eshelby, Mori-Tanaka and self-consistent schemes), based on continuum mechanics and asymptotic analysis, provide the stiffness tensor from the knowledge of the porosity and the elastic constants of the beads. Herein, the self-consistent scheme accurately predicts both bulk and shear moduli, with no adjustable parameter, provided the porosity is less than 35%, for layers composed of particles as small as 15 nm in diameter. Conversely, Kendall's approach is found to predict the Young's modulus over the full porosity range. Moreover, the adhesion energy in Kendall's model has to be adjusted to a value of the order of the fracture energy of the particle material. This suggests that sintering during drying leads to the formation of covalent siloxane bonds between the particles.

Surface-induced polymerization of actin.

PubMed Central

Renault, A; Lenne, P F; Zakri, C; Aradian, A; Vénien-Bryan, C; Amblard, F

1999-01-01

Living cells contain a very large amount of membrane surface area, which potentially influences the direction, the kinetics, and the localization of biochemical reactions. This paper quantitatively evaluates the possibility that a lipid monolayer can adsorb actin from a nonpolymerizing solution, induce its polymerization, and form a 2D network of individual actin filaments, in conditions that forbid bulk polymerization. G- and F-actin solutions were studied beneath saturated Langmuir monolayers containing phosphatidylcholine (PC, neutral) and stearylamine (SA, a positively charged surfactant) at PC:SA = 3:1 molar ratio. Ellipsometry, tensiometry, shear elastic measurements, electron microscopy, and dark-field light microscopy were used to characterize the adsorption kinetics and the interfacial polymerization of actin. In all cases studied, actin follows a monoexponential reaction-limited adsorption with similar time constants (approximately 10(3) s). At a longer time scale the shear elasticity of the monomeric actin adsorbate increases only in the presence of lipids, to a 2D shear elastic modulus of mu approximately 30 mN/m, indicating the formation of a structure coupled to the monolayer. Electron microscopy shows the formation of a 2D network of actin filaments at the PC:SA surface, and several arguments strongly suggest that this network is indeed causing the observed elasticity. Adsorption of F-actin to PC:SA leads more quickly to a slightly more rigid interface with a modulus of mu approximately 50 mN/m. PMID:10049338

Structural and electronic properties of high pressure phases of lead chalcogenides

NASA Astrophysics Data System (ADS)

Petersen, John; Scolfaro, Luisa; Myers, Thomas

2012-10-01

Lead chalcogenides, most notably PbTe and PbSe, have become an active area of research due to their thermoelectric properties. The high figure of merit (ZT) of these materials has brought much attention to them, due to their ability to convert waste heat into electricity. Variation in synthesis conditions gives rise to a need for analysis of structural and thermoelectric properties of these materials at different pressures. In addition to the NaCl structure at ambient conditions, lead chalcogenides have a dynamic orthorhombic (Pnma) intermediate phase and a higher pressure yet stable CsCl phase. By altering the lattice constant, we simulate the application of external pressure; this has notable effects on ground state total energy, band gap, and structural phase. Using the General Gradient Approximation (GGA) in Density Functional Theory (DFT), we calculate the phase transition pressures by finding the differences in enthalpy from total energy calculations. For each phase, elastic constants, bulk modulus, shear modulus, Young's modulus, and hardness are calculated, using two different approaches. In addition to structural properties, we analyze the band structure and density of states at varying pressures, paying special note to thermoelectric implications.

Influence of nanomechanical crystal properties on the comminution process of particulate solids in spiral jet mills.

PubMed

Zügner, Sascha; Marquardt, Karin; Zimmermann, Ingfried

2006-02-01

Elastic-plastic properties of single crystals are supposed to influence the size reduction process of bulk materials during jet milling. According to Pahl [M.H. Pahl, Zerkleinerungstechnik 2. Auflage. Fachbuchverlag, Leipzig (1993)] and H. Rumpf: [Prinzipien der Prallzerkleinerung und ihre Anwendung bei der Strahlmahlung. Chem. Ing. Tech., 3(1960) 129-135.] fracture toughness, maximum strain or work of fracture for example are strongly dependent on mechanical parameters like hardness (H) and young's modulus of elasticity (E). In addition the dwell time of particles in a spiral jet mill proved to correlate with the hardness of the feed material [F. Rief: Ph. D. Thesis, University of Würzburg (2001)]. Therefore 'near-surface' properties have a direct influence on the effectiveness of the comminution process. The mean particle diameter as well as the size distribution of the ground product may vary significantly with the nanomechanical response of the material. Thus accurate measurement of crystals' hardness and modulus is essential to determine the ideal operational micronisation conditions of the spiral jet mill. The recently developed nanoindentation technique is applied to examine subsurface properties of pharmaceutical bulk materials, namely calcite, sodium ascorbate, lactose and sodium chloride. Pressing a small sized tip into the material while continuously recording load and displacement, characteristic diagrams are derived. The mathematical evaluation of the force-displacement-data allows for calculation of the hardness and the elastic modulus of the investigated material at penetration depths between 50-300 nm. Grinding experiments performed with a modified spiral jet mill (Type Fryma JMRS 80) indicate the strong impact of the elastic-plastic properties of a given substance on its breaking behaviour. The fineness of milled products produced at constant grinding conditions but with different crystalline powders varies significantly as it is dependent on the nanohardness and the elasticity of the feed material. The analysis of this correlation gives new insights into the size reduction process.

Acoustic evaluation of loblolly pine tree- and lumber-length logs allows for segregation of lumber modulus of elasticity, not for modulus of rupture

Treesearch

Mark Alexander Butler; Joseph Dahlen; Thomas L. Eberhardt; Cristian Montes; Finto Antony; Richard F. Daniels

2017-01-01

Key message Loblolly pine (Pinus taeda) logs can be evaluated using acoustic velocity whereby threshold acoustic velocity values can be set to ensure lumber meets specified mechanical property design values for modulus of elasticity. Context...

Earlywood and latewood elastic properties in loblolly pine

Treesearch

Steven Cramer; David Kretschmann; Roderic Lakes; Troy Schmidt

2005-01-01

The elastic properties of earlywood and latewood and their variability were measured in 388 specimens from six loblolly pine trees in a commercial plantation. Properties measured included longitudinal modulus of elasticity, shear modulus, specific gravity, microfibril angle and presence of compression wood. Novel testing procedures were developed to measure properties...

First-principles calculation of the structural and elastic properties of ternary metal nitrides TaxMo1-xN and TaxW1-xN

NASA Astrophysics Data System (ADS)

Bouamama, Kh.; Djemia, P.; Benhamida, M.

2015-09-01

First-principles pseudo-potentials calculations of the mixing enthalpy, of the lattice constants a0 and of the single-crystal elastic constants cij for ternary metal nitrides TaxMe1-xN (Me=Mo or W) alloys considering the cubic B1-rocksalt structure is carried out. For disordered ternary alloys, we employ the virtual crystal approximation VCA in which the alloy pseudopotentials are constructed within a first-principles VCA scheme. The supercell method SC is also used for ordered structures in order to evaluate clustering effects. We find that the mixing enthalpy still remains negative for TaxMe1-xN alloys in the whole composition range which implies these cubic TaxMo1-xN and TaxW1-xN ordered solid solutions are stable. We investigate the effect of Mo and W alloying on the trend of the mechanical properties of TaN. The effective shear elastic constant c44, the Cauchy pressure (c12-c44), and the shear to bulk modulus G/B ratio are used to discuss, respectively, the mechanical stability of the ternary structure and the brittle/ductile behavior in reference to TaN, MeN alloys. We determine the onset transition from the unstable structure to the stable one B1-rocksalt from the elastic stability criteria when alloying MeN with Ta. In a second stage, in the frame of anisotropic elasticity, we estimate by one homogenization method the averaged constants of the polycrystalline TaxMe1-xN alloys considering the special case of an isotropic medium with no crystallographic texture.

Measurement of the elastic modulus of a multi-wall boron nitride nanotube

NASA Astrophysics Data System (ADS)

Chopra, Nasreen G.; Zettl, A.

1998-02-01

We have experimentally determined the elastic properties of an individual multi-wall boron nitride (BN) nanotube. From the thermal vibration amplitude of a cantilevered BN nanotube observed in a transmission electron microscope, we find the axial Young's modulus to be 1.22 ± 0.24 TPa, a value consistent with theoretical estimates. The observed Young's modulus exceeds that of all other known insulating fibers. Our elasticity results confirm that BN nanotubes are highly crystalline with very few defects.

Elasticity dominates strength and failure in metallic glasses

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

Liu, Z. Q.; Qu, R. T.; Zhang, Z. F., E-mail: zhfzhang@imr.ac.cn

2015-01-07

Two distinct deformation mechanisms of shearing and volume dilatation are quantitatively analyzed in metallic glasses (MGs) from the fundamental thermodynamics. Their competition is deduced to intrinsically dominate the strength and failure behaviors of MGs. Both the intrinsic shear and normal strengths give rise to the critical mechanical energies to activate destabilization of amorphous structures, under pure shearing and volume dilatation, respectively, and can be determined in terms of elastic constants. By adopting an ellipse failure criterion, the strength and failure behaviors of MGs can be precisely described just according to their shear modulus and Poisson's ratio without mechanical testing. Quantitativemore » relations are established systematically and verified by experimental results. Accordingly, the real-sense non-destructive failure prediction can be achieved in various MGs. By highlighting the broad key significance of elasticity, a “composition-elasticity-property” scheme is further outlined for better understanding and controlling the mechanical properties of MGs and other glassy materials from the elastic perspectives.« less

Mechanical and Thermophysical Properties of Cubic Rock-Salt AlN Under High Pressure

NASA Astrophysics Data System (ADS)

Lebga, Noudjoud; Daoud, Salah; Sun, Xiao-Wei; Bioud, Nadhira; Latreche, Abdelhakim

2018-03-01

Density functional theory, density functional perturbation theory, and the Debye model have been used to investigate the structural, elastic, sound velocity, and thermodynamic properties of AlN with cubic rock-salt structure under high pressure, yielding the equilibrium structural parameters, equation of state, and elastic constants of this interesting material. The isotropic shear modulus, Pugh ratio, and Poisson's ratio were also investigated carefully. In addition, the longitudinal, transverse, and average elastic wave velocities, phonon contribution to the thermal conductivity, and interesting thermodynamic properties were predicted and analyzed in detail. The results demonstrate that the behavior of the elastic wave velocities under increasing hydrostatic pressure explains the hardening of the corresponding phonons. Based on the elastic stability criteria under pressure, it is found that AlN with cubic rock-salt structure is mechanically stable, even at pressures up to 100 GPa. Analysis of the Pugh ratio and Poisson's ratio revealed that AlN with cubic rock-salt structure behaves in brittle manner.

Constitutive models for a poly(e-caprolactone) scaffold.

PubMed

Quinn, T P; Oreskovic, T L; McCowan, C N; Washburn, N R

2004-01-01

We investigate material models for a porous, polymeric scaffold used for bone. The material was made by co-extruding poly(e-caprolactone) (PCL), a biodegradable polyester, and poly(ethylene oxide) (PEO). The water soluble PEO was removed resulting in a porous scaffold. The stress-strain curve in compression was fit with a phenomenological model in hyperbolic form. This material model will be useful for designers for quasi-static analysis as it provides a simple form that can easily be used in finite element models. The ASTM D-1621 standard recommends using a secant modulus based on 10% strain. The resulting modulus has a smaller scatter in its value compared to the coefficients of the hyperbolic model, and it is therefore easier to compare material processing differences and ensure quality of the scaffold. A third material model was constructed from images of the microstructure. Each pixel of the micrographs was represented with a brick finite element and assigned the Young's modulus of bulk PCL or a value of 0 for a pore. A compressive strain was imposed on the model and the resulting stresses were calculated. The elastic constants of the scaffold were then computed using Hooke's law for a linear-elastic isotropic material. The model was able to predict the small strain Young's modulus measured in the experiments to within one standard deviation. Thus, by knowing the microstructure of the scaffold, its bulk properties can be predicted from the material properties of the constituents.

Variations in local elastic modulus along the length of the aorta as observed by use of a scanning haptic microscope (SHM).

PubMed

Moriwaki, Takeshi; Oie, Tomonori; Takamizawa, Keiichi; Murayama, Yoshinobu; Fukuda, Toru; Omata, Sadao; Kanda, Keiichi; Nakayama, Yasuhide

2011-12-01

Variations in microscopic elastic structures along the entire length of canine aorta were evaluated by use of a scanning haptic microscope (SHM). The total aorta from the aortic arch to the abdominal aorta was divided into 6 approximately equal segments. After embedding the aorta in agar, it was cut into horizontal circumferential segments to obtain disk-like agar portions containing ring-like samples of aorta with flat surfaces (thickness, approximately 1 mm). The elastic modulus and topography of the samples under no-load conditions were simultaneously measured along the entire thickness of the wall by SHM by using a probe with a diameter of 5 μm and a spatial resolution of 2 μm at a rate of 0.3 s/point. The elastic modulus of the wall was the highest on the side of the luminal surface and decreased gradually toward the adventitial side. This tendency was similar to that of the change in the elastin fiber content. During the evaluation of the mid-portion of each tunica media segment, the highest elastic modulus (40.8 ± 3.5 kPa) was identified at the thoracic section of the aorta that had the highest density of elastic fibers. Under no-load conditions, portions of the aorta with high elastin density have a high elastic modulus.

Damage of the Interface Between an Orthodontic Bracket and Enamel - the Effect of Some Elastic Properties of the Adhesive Material

NASA Astrophysics Data System (ADS)

Durgesh, B. H.; Alkheraif, A. A.; Al Sharawy, M.; Varrela, J.; Vallittu, P. K.

2016-01-01

The aim of this study was to investigate the magnitude of debonding stress of an orthodontic bracket bonded to the enamel with resin systems having different elastic properties. For the same purpose, sixty human premolars were randomly divided into four groups according to the adhesive system used for bonding brackets: G Fix flowable resin (GFI) with Everstick NET (ESN), GFI, G Aenial Universal Flow (GAU) with ESN, and GAU. The brackets were stressed in the occlusogingival direction on a universal testing machine. The values of debonding load and displacement were determined at the point of debonding. The elastic modulus of the tested materials was determined using nanoindentation. An analysis of variance showed a significant difference in the loads required to debond the bracket among the groups tested. The GAU group had the highest elastic modulus, followed by the GFI and ESN groups. ARI (Adhesive Remnant Index) scores demonstrated more remnants of the adhesive material on the bracket surface with adhesives having a higher elastic modulus. Taking into consideration results of the present in-vitro study, it can be concluded that the incorporation of a glass-fiber-reinforced composite resin (FRC) with a low elastic modulus between the orthodontic bracket and enamel increases the debonding force and strain more than with adhesive systems having a higher elastic modulus.

The influence of low temperatures on dynamic mechanical properties of animal bone

NASA Astrophysics Data System (ADS)

Mardas, Marcin; Kubisz, Leszek; Mielcarek, Slawomir; Biskupski, Piotr

2009-01-01

Different preservation methods are currently used in bone banks, even though their effects on allograft quality are not fully understood. Freezing is one of the most popular methods of preservation in tissue banking. Yet, there is not a lot of data on dynamic mechanical properties of frozen bone. Material used in this study was femoral bones from adult bovine that were machine cut and frozen to the temperature 140°C. Both elastic modulus and loss modulus were measured at 1, 3, 5, 10, and 20 Hz in the temperature range of 30-200°C. Differences between frozen and control samples were observed. The frequency increase always led to the increase in elastic modulus values and decrease in loss modulus values. Freezing reduced the elastic modulus values of about 25% and the loss modulus values of about 45% when measured at 20°C.

Elastic modulus affects the growth and differentiation of neural stem cells

PubMed Central

Jiang, Xian-feng; Yang, Kai; Yang, Xiao-qing; Liu, Ying-fu; Cheng, Yuan-chi; Chen, Xu-yi; Tu, Yue

2015-01-01

It remains poorly understood if carrier hardness, elastic modulus, and contact area affect neural stem cell growth and differentiation. Tensile tests show that the elastic moduli of Tiansu and SMI silicone membranes are lower than that of an ordinary dish, while the elastic modulus of SMI silicone membrane is lower than that of Tiansu silicone membrane. Neural stem cells from the cerebral cortex of embryonic day 16 Sprague-Dawley rats were seeded onto ordinary dishes as well as Tiansu silicone membrane and SMI silicone membrane. Light microscopy showed that neural stem cells on all three carriers show improved adherence. After 7 days of differentiation, neuron specific enolase, glial fibrillary acidic protein, and myelin basic protein expression was detected by immunofluorescence. Moreover, flow cytometry revealed a higher rate of neural stem cell differentiation into astrocytes on Tiansu and SMI silicone membranes than on the ordinary dish, which was also higher on the SMI than the Tiansu silicone membrane. These findings confirm that all three cell carrier types have good biocompatibility, while SMI and Tiansu silicone membranes exhibit good mechanical homogenization. Thus, elastic modulus affects neural stem cell differentiation into various nerve cells. Within a certain range, a smaller elastic modulus results in a more obvious trend of cell differentiation into astrocytes. PMID:26604916

Theoretical investigations on structural, elastic and electronic properties of thallium halides

NASA Astrophysics Data System (ADS)

Singh, Rishi Pal; Singh, Rajendra Kumar; Rajagopalan, Mathrubutham

2011-04-01

Theoretical investigations on structural, elastic and electronic properties, viz. ground state lattice parameter, elastic moduli and density of states, of thallium halides (viz. TlCl and TlBr) have been made using the full potential linearized augmented plane wave method within the generalized gradient approximation (GGA). The ground state lattice parameter and bulk modulus and its pressure derivative have been obtained using optimization method. Young's modulus, shear modulus, Poisson ratio, sound velocities for longitudinal and shear waves, Debye average velocity, Debye temperature and Grüneisen parameter have also been calculated for these compounds. Calculated structural, elastic and other parameters are in good agreement with the available data.

In situ elasticity modulation with dynamic substrates to direct cell phenotype

PubMed Central

Kloxin, April M.; Benton, Julie A.; Anseth, Kristi S.

2009-01-01

Microenvironment elasticity influences critical cell functions such as differentiation, cytoskeletal organization, and process extension. Unfortunately, few materials allow elasticity modulation in real-time to probe its direct effect on these dynamic cellular processes. Here, a new approach is presented for the photochemical modulation of elasticity within the cell's microenvironment at any point in time. A photodegradable hydrogel was irradiated and degraded under cytocompatible conditions to generate a wide range of elastic moduli similar to soft tissues and characterized using rheometry and atomic force microscopy (AFM). The effect of the elastic modulus on valvular interstitial cell (VIC) activation into myofibroblasts was explored. In these studies, gradient samples were used to identify moduli that either promote or suppress VIC myofibroblastic activation. With this knowledge, VICs were cultured on a high modulus, activating hydrogel substrate, and uniquely, results show that decreasing the substrate modulus with irradiation reverses this activation, demonstrating that myofibroblasts can be de-activated solely by changing the modulus of the underlying substrate. This finding is important for the rational design of biomaterials for tissue regeneration and offers insight into fibrotic disease progression. These photodegradable hydrogels demonstrate the capability to both probe and direct cell function through dynamic changes in substrate elasticity. PMID:19788947

Mechanical properties investigation on single-wall ZrO2 nanotubes: A finite element method with equivalent Poisson's ratio for chemical bonds

NASA Astrophysics Data System (ADS)

Yang, Xiao; Li, Huijian; Hu, Minzheng; Liu, Zeliang; Wärnå, John; Cao, Yuying; Ahuja, Rajeev; Luo, Wei

2018-04-01

A method to obtain the equivalent Poisson's ratio in chemical bonds as classical beams with finite element method was proposed from experimental data. The UFF (Universal Force Field) method was employed to calculate the elastic force constants of Zrsbnd O bonds. By applying the equivalent Poisson's ratio, the mechanical properties of single-wall ZrNTs (ZrO2 nanotubes) were investigated by finite element analysis. The nanotubes' Young's modulus (Y), Poisson's ratio (ν) of ZrNTs as function of diameters, length and chirality have been discussed, respectively. We found that the Young's modulus of single-wall ZrNTs is calculated to be between 350 and 420 GPa.

Flows in forward deformable roll coating gaps: Comparison between spring and plane-strain models of roll cover

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

Carvalho, M.S.; Scriven, L.E.

1997-12-01

In this report the flow between rigid and a deformable rotating rolls fully submerged in a liquid pool is studied. The deformation of compliant roll cover is described by two different models (1) independent, radially oriented springs that deform in response to the traction force applied at the extremity of each or one-dimensional model, and (2) a plane-strain deformation of an incompressible Mooney-Rivlin material or non-linear elastic model. Based on the flow rate predictions of both models, an empirical relation between the spring constant of the one dimensional model and the roll cover thickness and elastic modulus is proposed.

Regional variation in wood modulus of elasticity (stiffness) and modulus of rupture (strength) of planted loblolly pine in the United States

Treesearch

Antony Finto; Lewis Jordan; Laurence R. Schimleck; Alexander Clark; Ray A. Souter; Richard F. Daniels

2011-01-01

Modulus of elasticity (MOE), modulus of rupture (MOR), and specific gravity (SG) are important properties for determining the end-use and value of a piece of lumber. This study addressed the variation in MOE, MOR, and SG with physiographic region, tree height, and wood type. Properties were measured from two static bending samples (dimensions 25.4 mm × 25.4 mm × 406.4...

Nanoscale elastic modulus variation in loaded polymeric micelle reactors.

PubMed

Solmaz, Alim; Aytun, Taner; Deuschle, Julia K; Ow-Yang, Cleva W

2012-07-17

Tapping mode atomic force microscopy (TM-AFM) enables mapping of chemical composition at the nanoscale by taking advantage of the variation in phase angle shift arising from an embedded second phase. We demonstrate that phase contrast can be attributed to the variation in elastic modulus during the imaging of zinc acetate (ZnAc)-loaded reverse polystyrene-block-poly(2-vinylpyridine) (PS-b-P2VP) diblock co-polymer micelles less than 100 nm in diameter. Three sample configurations were characterized: (i) a 31.6 μm thick polystyrene (PS) support film for eliminating the substrate contribution, (ii) an unfilled PS-b-P2VP micelle supported by the same PS film, and (iii) a ZnAc-loaded PS-b-P2VP micelle supported by the same PS film. Force-indentation (F-I) curves were measured over unloaded micelles on the PS film and over loaded micelles on the PS film, using standard tapping mode probes of three different spring constants, the same cantilevers used for imaging of the samples before and after loading. For calibration of the tip geometry, nanoindentation was performed on the bare PS film. The resulting elastic modulus values extracted by applying the Hertz model were 8.26 ± 3.43 GPa over the loaded micelles and 4.17 ± 1.65 GPa over the unloaded micelles, confirming that phase contrast images of a monolayer of loaded micelles represent maps of the nanoscale chemical and mechanical variation. By calibrating the tip geometry indirectly using a known soft material, we are able to use the same standard tapping mode cantilevers for both imaging and indentation.

Preparation and mechanical characterization of a PNIPA hydrogel composite.

PubMed

Liu, Kaifeng; Ovaert, Timothy C; Mason, James J

2008-04-01

A poly (N-isopropylacrylamide) (PNIPA) hydrogel was synthesized by free radical polymerization and reinforced with a polyurethane foam to make a hydrogel composite. The temperature dependence of the elastic modulus of the PNIPA hydrogel and the composite due to volume phase transition was found using a uniaxial compression test, and the swelling property was investigated using an equilibrium swelling ratio experiment. The gel composite preserves the ability to undergo the volume phase transition and its elastic modulus has strong temperature dependence. The temperature dependence of the elastic modulus and swelling ratio of the gel composite were compared to the PNIPA hydrogel. Not surprisingly, the modulus and swelling ratio of the composite were less dramatic than in the gel.

Effects of Temperature on the Tensile Strength and Elastic Modulus of Composite Material.

DTIC Science & Technology

1985-03-01

9.)- IU1.6 1.4 Figure 4.7. Peak Stress vs Tab Angle temperature. The constant temperature distribution zone of the Marshell furnace extends 4 inches...actually used.) d) The clear hole diameter of the Marshell funace is 3.0 inches. The dimensions of the specimen for this investigation was determined...Applied Test System, Inc., Butter, Pennsyl- vania) , were used to pull a specimen at elevated temperatures. A Marshell model 2232 three-zone

Nanoindentation mapping of a wood-adhesive bond

NASA Astrophysics Data System (ADS)

Konnerth, J.; Valla, A.; Gindl, W.

2007-08-01

A mapping experiment of a wood phenol-resorcinol-formaldehyde adhesive bond was performed by means of grid nanoindentation. The variability of the modulus of elasticity and the hardness was evaluated for an area of 17 μm by 90 μm. Overall, the modulus of elasticity of the adhesive was clearly lower than the modulus of wood cell walls, whereas the hardness of the adhesive was slightly higher compared to cell walls. A very slight trend of decreasing modulus of elasticity was found with increasing distance from the immediate bond line. However, the trend was superimposed by a high variability of the modulus of elasticity in dependence on the position in the wood cell wall. The unexpectedly high variation of the modulus between 12 and 24 GPa may be explained by the interaction between the helical orientation of the cellulose microfibrils in the S2 layer of the wood cell wall and the geometry of the three-sided Berkovich type indenter pyramid used. Corresponding to the very slight decrease in modulus with increasing distance from the bond line, a similar but clearer trend was found for hardness. Both trends of changing mechanical properties of wood cell walls with varying distance from the bond line are attributed to effects of adhesive penetration into the wood cell wall.

Compositional and microstructural design of highly bioactive P2O5-Na2O-CaO-SiO2 glass-ceramics.

PubMed

Peitl, Oscar; Zanotto, Edgar D; Serbena, Francisco C; Hench, Larry L

2012-01-01

Bioactive glasses having chemical compositions between 1Na(2)O-2CaO-3SiO(2) (1N2C3S) and 1.5Na(2)O-1.5CaO-3SiO(2) (1N1C2S) containing 0, 4 and 6 wt.% P(2)O(5) were crystallized through two stage thermal treatments. By carefully controlling these treatments we separately studied the effects on the mechanical properties of two important microstructural features not studied before, crystallized volume fraction and crystal size. Fracture strength, elastic modulus and indentation fracture toughness were measured as a function of crystallized volume fraction for a constant crystal size. Glass-ceramics with a crystalline volume fraction between 34% and 60% exhibited a three-fold improvement in fracture strength and an increase of 40% in indentation fracture toughness compared with the parent glass. For the optimal crystalline concentration (34% and 60%) these mechanical properties were then measured for different grain sizes, from 5 to 21 μm. The glass-ceramic with the highest fracture strength and indentation fracture toughness was that with 34% crystallized volume fracture and 13 μm crystals. Compared with the parent glass, the average fracture strength of this glass-ceramic was increased from 80 to 210 MPa, and the fracture toughness from 0.60 to 0.95 MPa.m(1/2). The increase in indentation fracture toughness was analyzed using different theoretical models, which demonstrated that it is due to crack deflection. Fortunately, the elastic modulus E increased only slightly; from 60 to 70 GPa (the elastic modulus of biomaterials should be as close as possible to that of cortical bone). In summary, the flexural strength of our best material (215 MPa) is significantly greater than that of cortical bone and comparable with that of apatite-wollastonite (A/W) bioglass ceramics, with the advantage that it shows a much lower elastic modulus. These results thus provide a relevant guide for the design of bioactive glass-ceramics with improved microstructure. Copyright © 2011 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Linear analysis using secants for materials with temperature dependent nonlinear elastic modulus and thermal expansion properties

NASA Astrophysics Data System (ADS)

Pepi, John W.

2017-08-01

Thermally induced stress is readily calculated for linear elastic material properties using Hooke's law in which, for situations where expansion is constrained, stress is proportional to the product of the material elastic modulus and its thermal strain. When material behavior is nonlinear, one needs to make use of nonlinear theory. However, we can avoid that complexity in some situations. For situations in which both elastic modulus and coefficient of thermal expansion vary with temperature, solutions can be formulated using secant properties. A theoretical approach is thus presented to calculate stresses for nonlinear, neo-Hookean, materials. This is important for high acuity optical systems undergoing large temperature extremes.

Deformation partitioning provides insight into elastic, plastic, and viscous contributions to bone material behavior.

PubMed

Ferguson, V L

2009-08-01

The relative contributions of elastic, plastic, and viscous material behavior are poorly described by the separate extraction and analysis of the plane strain modulus, E('), the contact hardness, H(c) (a hybrid parameter encompassing both elastic and plastic behavior), and various viscoelastic material constants. A multiple element mechanical model enables the partitioning of a single indentation response into its fundamental elastic, plastic, and viscous deformation components. The objective of this study was to apply deformation partitioning to explore the role of hydration, tissue type, and degree of mineralization in bone and calcified cartilage. Wet, ethanol-dehydrated, and PMMA-embedded equine cortical bone samples and PMMA-embedded human femoral head tissues were analyzed for contributions of elastic, plastic and viscous deformation to the overall nanoindentation response at each site. While the alteration of hydration state had little effect on any measure of deformation, unembedded tissues demonstrated significantly greater measures of resistance to plastic deformation than PMMA-embedded tissues. The PMMA appeared to mechanically stabilize the tissues and prevent extensive permanent deformation within the bone material. Increasing mineral volume fraction correlated with positive changes in E('), H(c), and resistance to plastic deformation, H; however, the partitioned deformation components were generally unaffected by mineralization. The contribution of viscous deformation was minimal and may only play a significant role in poorly mineralized tissues. Deformation partitioning enables a detailed interpretation of the elastic, plastic, and viscous contributions to the nanomechanical behavior of mineralized tissues that is not possible when examining modulus and contact hardness alone. Varying experimental or biological factors, such as hydration or mineralization level, enables the understanding of potential mechanisms for specific mechanical behavior patterns that would otherwise be hidden within a more complex set of material property parameters.

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.

A rate insensitive linear viscoelastic model for soft tissues

PubMed Central

Zhang, Wei; Chen, Henry Y.; Kassab, Ghassan S.

2012-01-01

It is well known that many biological soft tissues behave as viscoelastic materials with hysteresis curves being nearly independent of strain rate when loading frequency is varied over a large range. In this work, the rate insensitive feature of biological materials is taken into account by a generalized Maxwell model. To minimize the number of model parameters, it is assumed that the characteristic frequencies of Maxwell elements form a geometric series. As a result, the model is characterized by five material constants: μ0, τ, m, ρ and β, where μ0 is the relaxed elastic modulus, τ the characteristic relaxation time, m the number of Maxwell elements, ρ the gap between characteristic frequencies, and β = μ1/μ0 with μ1 being the elastic modulus of the Maxwell body that has relaxation time τ. The physical basis of the model is motivated by the microstructural architecture of typical soft tissues. The novel model shows excellent fit of relaxation data on the canine aorta and captures the salient features of vascular viscoelasticity with significantly fewer model parameters. PMID:17512585

Theoretical Investigation of Half-Metallic Oxides XFeO3 (X = Sr, Ba) via Modified Becke-Johnson Potential Scheme

NASA Astrophysics Data System (ADS)

Maqsood, Saba; Rashid, Muhammad; Din, Fasih Ud; Saddique, M. Bilal; Laref, A.

2018-03-01

The cubic XFeO3 (X = Sr, Ba) perovskite oxides are studied for their thermodynamic stability in the ferromagnetic phase by using density functional theory calculations. We also explore the elastic properties of these compounds in terms of elastic constants C ij, bulk modulus B, shear modulus G, anisotropy factor A, Poisson's ratio ν and the B/ G ratio. The electronic properties are examined to elucidate the magnetic order, and the thermoelectric properties of XFeO3 (X = Sr, Ba) materials are also presented. The modified Becke-Johnson local density approximation scheme has been used to compute the electronic band structure and density of states, which show that these materials are half-metallic ferromagnetic. We study the magnetic properties by computing the crystal field energy (ΔCF), John-Teller energy (ΔJT) and the exchange splitting energies Δx( d) and Δx( pd). Our results indicate that strong hybridization causes a decrease in the magnetic moment of Fe, which then produces permanent magnetic moments in the nonmagnetic sites.

High elastic modulus nanopowder reinforced resin composites for dental applications

NASA Astrophysics Data System (ADS)

Wang, Yijun

2007-12-01

Dental restorations account for more than $3 billion dollars a year on the market. Among them, all-ceramic dental crowns draw more and more attention and their popularity has risen because of their superior aesthetics and biocompatibility. However, their relatively high failure rate and labor-intensive fabrication procedure still limit their application. In this thesis, a new family of high elastic modulus nanopowder reinforced resin composites and their mechanical properties are studied. Materials with higher elastic modulus, such as alumina and diamond, are used to replace the routine filler material, silica, in dental resin composites to achieve the desired properties. This class of composites is developed to serve (1) as a high stiffness support to all-ceramic crowns and (2) as a means of joining independently fabricated crown core and veneer layers. Most of the work focuses on nano-sized Al2O3 (average particle size 47 nm) reinforcement in a polymeric matrix with 50:50 Bisphenol A glycidyl methacrylate (Bis-GMA): triethylene glycol dimethacrylate (TEGDMA) monomers. Surfactants, silanizing agents and primers are examined to obtain higher filler levels and enhance the bonding between filler and matrix. Silane agents work best. The elastic modulus of a 57.5 vol% alumina/resin composite is 31.5 GPa compared to current commercial resin composites with elastic modulus <15 GPa. Chemical additives can also effectively raise the hardness to as much as 1.34 GPa. Besides>alumina, diamond/resin composites are studied. An elastic modulus of about 45 GPa is obtained for a 57 vol% diamond/resin composite. Our results indicate that with a generally monodispersed nano-sized high modulus filler, relatively high elastic modulus resin-based composite cements are possible. Time-dependent behavior of our resin composites is also investigated. This is valuable for understanding the behavior of our material and possible fatigue testing in the future. Our results indicate that with effective coupling agents and higher filler loading, viscous flow can be greatly decreased due to the attenuation of mobility of polymer chains. Complementary studies indicate that our resin composites are promising for the proposed applications as a stiff support to all-ceramic crowns.

Confinement Effect on Material Properties of RC Beams Under Flexure

NASA Astrophysics Data System (ADS)

Kulkarni, Sumant; Shiyekar, Mukund Ramchandra; Shiyekar, Sandip Mukund

2017-12-01

In structural analysis, especially in indeterminate structures, it becomes essential to know the material and geometrical properties of members. The codal provisions recommend elastic properties of concrete and steel and these are fairly accurate enough. The stress-strain curve for concrete cylinder or a cube specimen is plotted. The slope of this curve is modulus of elasticity of plain concrete. Another method of determining modulus of elasticity of concrete is by flexural test of a beam specimen. The modulus of elasticity most commonly used for concrete is secant modulus. The modulus of elasticity of steel is obtained by performing a tension test of steel bar. While performing analysis by any software for high rise building, cross area of plain concrete is taken into consideration whereas effects of reinforcement bars and concrete confined by stirrups are neglected. Present aim of study is to determine elastic properties of reinforced cement concrete beam. Two important stiffness properties such as AE and EI play important role in analysis of high rise RCC building idealized as plane frame. The experimental program consists of testing of beams (model size 150 × 150 × 700 mm) with percentage of reinforcement varying from 0.54 to 1.63% which commensurate with existing Codal provisions of IS:456-2000 for flexural member. The effect of confinement is considered in this study. The experimental results are verified by using 3D finite element techniques.

First-principles study of the structural and elastic properties of AuxV1-x and AuxNb1-x alloys

NASA Astrophysics Data System (ADS)

Al-Zoubi, N.

2018-04-01

Ab initio total energy calculations, based on the Exact Muffin-Tin Orbitals (EMTO) method in combination with the coherent potential approximation (CPA), are used to calculate the total energy of AuxV1-x and AuxNb1-x random alloys along the Bain path that connects the body-centred cubic (bcc) and face-centred cubic (fcc) structures as a function of composition x (0 ≤ x ≤ 1). The equilibrium Wigner-Seitz radius and the elastic properties of both systems are determined as a function of composition. Our theoretical prediction in case of pure elements (x = 0 or x = 1) are in good agreement with the available experimental data. For the Au-V system, the equilibrium Wigner-Seitz radius increase as x increases, while for the Au-Nb system, the equilibrium Wigner-Seitz radius is almost constant. The bulk modulus B and C44 for both alloys exhibit nearly parabolic trend. On the other hand, the tetragonal shear elastic constant C‧ decreases as x increases and correlates reasonably well with the structural energy difference between fcc and bcc structures. Our results offer a consistent starting point for further theoretical and experimental studies of the elastic and micromechanical properties of Au-V and Au-Nb systems.

Study on axial strength of a channel-shaped pultruded GFRP member

NASA Astrophysics Data System (ADS)

Matsumoto, Yukihiro; Satake, Chito; Nisida, Kenji

2017-10-01

Fiber reinforced polymers (FRP) are widely used in vehicle and aerospace applications because of their lightweight and high-strength characteristics. Additionally, FRPs are increasingly applied to building structures. However, the elastic modulus of glass fiber reinforced polymers (GFRPs) is lower than that of steel. Hence, the evaluating the buckling strength of GFRP members for design purpose is necessary. The buckling strength is determined by Euler buckling mode as well as local buckling. In this study investigated the compressive strength of GFRP members subjected to axial compression through experiments and theoretical calculations. The adopted GFRP member was a channel-shaped GFRP, which was molded via pultrusion, at various lengths. Although, the mechanical properties as longitudinal elastic modulus and fiber volume fraction and strength of GFRP members subjected, to axial can be easily evaluated, evaluating transverse elastic modulus and shear modulus in typical material tests is difficult in standard section. Therefore the composite law was used in this study. As a result, we confirmed that the axial strength of a GFRP member could be calculated by a theoretical evaluation method utilizing longitudinal elastic modulus and fiber volume fraction.

Tuning the Elastic Modulus of Hydrated Collagen Fibrils

PubMed Central

Grant, Colin A.; Brockwell, David J.; Radford, Sheena E.; Thomson, Neil H.

2009-01-01

Abstract Systematic variation of solution conditions reveals that the elastic modulus (E) of individual collagen fibrils can be varied over a range of 2–200 MPa. Nanoindentation of reconstituted bovine Achilles tendon fibrils by atomic force microscopy (AFM) under different aqueous and ethanol environments was carried out. Titration of monovalent salts up to a concentration of 1 M at pH 7 causes E to increase from 2 to 5 MPa. This stiffening effect is more pronounced at lower pH where, at pH 5, e.g., there is an ∼7-fold increase in modulus on addition of 1 M KCl. An even larger increase in modulus, up to ∼200 MPa, can be achieved by using increasing concentrations of ethanol. Taken together, these results indicate that there are a number of intermolecular forces between tropocollagen monomers that govern the elastic response. These include hydration forces and hydrogen bonding, ion pairs, and possibly the hydrophobic effect. Tuning of the relative strengths of these forces allows rational tuning of the elastic modulus of the fibrils. PMID:19948128

Film thickness for different regimes of fluid-film lubrication

NASA Technical Reports Server (NTRS)

Hamrock, B. J.

1980-01-01

Film thickness equations are provided for four fluid-film lubrication regimes found in elliptical contacts. These regimes are isoviscous-rigid; viscous-rigid; elastohydrodynamic lubrication of low-elastic-modulus materials (soft EHL), or isoviscous-elastic; and elastohydrodynamic lubrication of high-elastic-modulus materials (hard EHL), or viscous-elastic. The influence or lack of influence of elastic and viscous effects is the factor that distinguishes these regimes. The results are presented as a map of the lubrication regimes, with film thickness contours on a log-log grid of the viscosity and elasticity for three values of the ellipticity parameter.

Biophysically defined and cytocompatible covalently adaptable networks as viscoelastic 3D cell culture systems.

PubMed

McKinnon, Daniel D; Domaille, Dylan W; Cha, Jennifer N; Anseth, Kristi S

2014-02-12

Presented here is a cytocompatible covalently adaptable hydrogel uniquely capable of mimicking the complex biophysical properties of native tissue and enabling natural cell functions without matrix degradation. Demonstrated is both the ability to control elastic modulus and stress relaxation time constants by more than an order of magnitude while predicting these values based on fundamental theoretical understanding and the simulation of muscle tissue and the encapsulation of myoblasts. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Elastic Modulus Measurement of ORNL ATF FeCrAl Alloys

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

Thompson, Zachary T.; Terrani, Kurt A.; Yamamoto, Yukinori

2015-10-01

Elastic modulus and Poisson’s ratio for a number of wrought FeCrAl alloys, intended for accident tolerant fuel cladding application, are determined via resonant ultrasonic spectroscopy. The results are reported as a function of temperature from room temperature to 850°C. The wrought alloys were in the fully annealed and unirradiated state. The elastic modulus for the wrought FeCrAl alloys is at least twice that of Zr-based alloys over the temperature range of this study. The Poisson’s ratio of the alloys was 0.28 on average and increased very slightly with increasing temperature.

Radiation-damage-induced transitions in zircon: Percolation theory applied to hardness and elastic moduli as a function of density

NASA Astrophysics Data System (ADS)

Beirau, Tobias; Nix, William D.; Ewing, Rodney C.; Pöllmann, Herbert; Salje, Ekhard K. H.

2018-05-01

Two in literature predicted percolation transitions in radiation-damaged zircon (ZrSiO4) were observed experimentally by measurement of the indentation hardness as a function of density and their correlation with the elastic moduli. Percolations occur near 30% and 70% amorphous fractions, where hardness deviates from its linear correlation with the elastic modulus (E), the shear modulus (G) and the bulk modulus (K). The first percolation point pc1 generates a cusp in the hardness versus density evolution, while the second percolation point is seen as a change of slope.

Nanoscale characterization of the biomechanical properties of collagen fibrils in the sclera

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

Papi, M.; Paoletti, P.; Geraghty, B.

We apply the PeakForce Quantitative Nanomechanical Property Mapping (PFQNM) atomic force microscopy mode for the investigation of regional variations in the nanomechanical properties of porcine sclera. We examine variations in the collagen fibril diameter, adhesion, elastic modulus and dissipation in the posterior, equatorial and anterior regions of the sclera. The mean fibril diameter, elastic modulus and dissipation increased from the posterior to the anterior region. Collagen fibril diameter correlated linearly with elastic modulus. Our data matches the known macroscopic mechanical behavior of the sclera. We propose that PFQNM has significant potential in ocular biomechanics and biophysics research.

Relationship between tendon stiffness and failure: a metaanalysis

PubMed Central

LaCroix, Andrew S.; Duenwald-Kuehl, Sarah E.; Lakes, Roderic S.

2013-01-01

Tendon is a highly specialized, hierarchical tissue designed to transfer forces from muscle to bone; complex viscoelastic and anisotropic behaviors have been extensively characterized for specific subsets of tendons. Reported mechanical data consistently show a pseudoelastic, stress-vs.-strain behavior with a linear slope after an initial toe region. Many studies report a linear, elastic modulus, or Young's modulus (hereafter called elastic modulus) and ultimate stress for their tendon specimens. Individually, these studies are unable to provide a broader, interstudy understanding of tendon mechanical behavior. Herein we present a metaanalysis of pooled mechanical data from a representative sample of tendons from different species. These data include healthy tendons and those altered by injury and healing, genetic modification, allograft preparation, mechanical environment, and age. Fifty studies were selected and analyzed. Despite a wide range of mechanical properties between and within species, elastic modulus and ultimate stress are highly correlated (R2 = 0.785), suggesting that tendon failure is highly strain-dependent. Furthermore, this relationship was observed to be predictable over controlled ranges of elastic moduli, as would be typical of any individual species. With the knowledge gained through this metaanalysis, noninvasive tools could measure elastic modulus in vivo and reasonably predict ultimate stress (or structural compromise) for diseased or injured tendon. PMID:23599401

The value of quantitative shear wave elastography in differentiating the cervical lymph nodes in patients with thyroid nodules.

PubMed

You, Jun; Chen, Juan; Xiang, Feixiang; Song, Yue; Khamis, Simai; Lu, Chengfa; Lv, Qing; Zhang, Yanrong; Xie, Mingxing

2018-04-01

This study aimed at evaluating the diagnostic performance of quantitative shear wave elastography (SWE) in differentiating metastatic cervical lymph nodes from benign nodes in patients with thyroid nodules. One hundred and forty-one cervical lymph nodes from 39 patients with thyroid nodules that were diagnosed as papillary thyroid cancer had been imaged with SWE. The shear elasticity modulus, which indicates the stiffness of the lymph nodes, was measured in terms of maximum shear elasticity modulus (maxSM), minimum shear elasticity modulus (minSM), mean shear elasticity modulus (meanSM), and standard deviation (SD) of the shear elasticity modulus. All the patients underwent thyroid surgery, 50 of the suspicious lymph nodes were resected, and 91 lymph nodes were followed up for 6 months. The maxSM value, minSM value, meanSM value, and SD value of the metastatic lymph nodes were significantly higher than those of the benign nodes. The area under the curve of the maxSM value, minSM value, meanSM value, and SD value were 0.918, 0.606, 0.865, and 0.915, respectively. SWE can differentiate metastasis from benign cervical lymph nodes in patients with thyroid nodules, and the maxSM, meanSM, and SD may be valuable quantitative indicators for characterizing cervical lymph nodes.

Use of an ultrasonic device for the determination of elastic modulus of dentin.

PubMed

Miyazaki, Masashi; Inage, Hirohiko; Onose, Hideo

2002-03-01

The mechanical properties of dentin substrate are one of the important factors in determining bond strength of dentin bonding systems. The purpose of this study was to determine the elastic modulus of dentin substrate with the use of an ultrasonic device. The dentin disks of about 1 mm thickness were obtaining from freshly extracted human third molars, and the dentin disk was shaped in a rectangular form with a line diamond point. The size and weight of each specimen was measured to calculate the density of the specimen. The ultrasonic equipment employed in this study was composed of a Pulser-Receiver (Model 5900PR, Panametrics), transducers (V155, V156, Panametrics) and an oscilloscope. The measured two-way transit time through the dentin disk was divided by two to account for the down-and-back travel path, and then multiplied by the velocity of sound in the test material. Measuring the longitudinal and share wave sound velocity determine elastic modulus. The mean elastic modulus of horizontally sectioned specimens was 21.8 GPa and 18.5 GPa for the vertically sectioned specimens, and a significant difference was found between the two groups. The ultrasonic method used in this study shows considerable promise for determination of the elastic modulus of the tooth substrate.

Influence of Ce addition on biomedical porous Ti-51 atomic percentage (at. %) Ni shape memory alloy fabricated by microwave sintering

NASA Astrophysics Data System (ADS)

Ibrahim, Mustafa K.; Hamzah, E.; Saud, Safaa N.; Nazim, E. M.; Bahador, A.

2017-12-01

Ti-Ni and Ti-Ni-Ce shape memory alloys (SMAs) were successfully fabricated by microwave sintering. The improvement of the mechanical properties especially the elastic modulus is the most important criterion in this research. The high elastic modulus problems are the most critical issues frequently encountered in hard tissue replacement applications. The effect of Ce addition with four atomic percentages (0 %, 0.19 %, 0.385 % and, 1.165 %) on the microstructure, phase composition, transformation temperatures and mechanical properties was investigated by scanning electron microscopy (SEM), X-ray diffraction (XRD), Differential Scanning Calorimeter (DSC), and compression test. The microstructure shows plates-like with needles-like inside the titanium-rich region. The compression strain was improved, but reduces the compression strength. The addition of cerium improved the properties by reducing the elastic modulus to be very close to the natural human bone, also the microwave sintering gives TiNi SMAs with low elastic modulus comparing with other methods. Based on the results, the 0.385 at. % Ce exhibited a remarkable highest compressive strain and lower elastic modulus compared with the other percentages. In conclusion, the present results indicate that Ti-Ni-Ce SMAs could be a potential alternative to improve Ti-51 at %Ni SMAs for certain biomedical applications.

High Pressure Elastic Constants of High-Pressure Iron Analog Osmium

NASA Astrophysics Data System (ADS)

Godwal, B. K.; Geballe, Z.; Jeanloz, R.

2011-12-01

Understanding the elasticity of hcp iron is important both for ascertaining the stable phase and for explaining the observed seismic anomalies of Earth's inner core. A systematic experimental study of analog materials is warranted because experiments at inner-core conditions remain exceptionally challenging and theory has yielded conflicting results for iron. The deformation of hexagonal close-packed (hcp) Os, an analog for the high-pressure hcp form of Fe, has been characterized under non-hydrostatic stresses using synchrotron-based angular-dispersive radial x-ray diffraction to pressures of 60 GPa at room temperature. Starting with published ultrasonic values of elastic constants and previous measurements of linear and volume compressibilities, we estimate the single-crystal elasticity tensor of osmium to 60 GPa and find that the crystal orientation with the largest shear modulus, (002), accommodates the largest shear stress (10 GPa) and a differential strain surpassing the Voigt iso-strain limit. We find the conventional elastic model, bounded by Reuss (iso-stress) and Voigt limits, inadequate for explaining our measurements. Instead, we infer that plastic deformation limits the amount of shear stress supported by the crystal planes near the a-axis, causing the more elastically strong c-axis to support the majority of the differential strain. This conclusion is consistent with the elasto-plastic self-consistent approach used to model the effect of plasticity on the high-pressure deformation of hcp-Co (Merkel et al, PRB 79, 064110 (2009)). Importantly, we document a strength anisotropy so large that the Voigt (elastic) limit is clearly surpassed.

Endothelial, cardiac muscle and skeletal muscle exhibit different viscous and elastic properties as determined by atomic force microscopy

NASA Technical Reports Server (NTRS)

Mathur, A. B.; Collinsworth, A. M.; Reichert, W. M.; Kraus, W. E.; Truskey, G. A.

2001-01-01

This study evaluated the hypothesis that, due to functional and structural differences, the apparent elastic modulus and viscous behavior of cardiac and skeletal muscle and vascular endothelium would differ. To accurately determine the elastic modulus, the contribution of probe velocity, indentation depth, and the assumed shape of the probe were examined. Hysteresis was observed at high indentation velocities arising from viscous effects. Irreversible deformation was not observed for endothelial cells and hysteresis was negligible below 1 microm/s. For skeletal muscle and cardiac muscle cells, hysteresis was negligible below 0.25 microm/s. Viscous dissipation for endothelial and cardiac muscle cells was higher than for skeletal muscle cells. The calculated elastic modulus was most sensitive to the assumed probe geometry for the first 60 nm of indentation for the three cell types. Modeling the probe as a blunt cone-spherical cap resulted in variation in elastic modulus with indentation depth that was less than that calculated by treating the probe as a conical tip. Substrate contributions were negligible since the elastic modulus reached a steady value for indentations above 60 nm and the probe never indented more than 10% of the cell thickness. Cardiac cells were the stiffest (100.3+/-10.7 kPa), the skeletal muscle cells were intermediate (24.7+/-3.5 kPa), and the endothelial cells were the softest with a range of elastic moduli (1.4+/-0.1 to 6.8+/-0.4 kPa) depending on the location of the cell surface tested. Cardiac and skeletal muscle exhibited nonlinear elastic behavior. These passive mechanical properties are generally consistent with the function of these different cell types.

Finite element investigation of temperature dependence of elastic properties of carbon nanotube reinforced polypropylene

NASA Astrophysics Data System (ADS)

Ahmadi, Masoud; Ansari, Reza; Rouhi, Saeed

2017-11-01

This paper aims to investigate the elastic modulus of the polypropylene matrix reinforced by carbon nanotubes at different temperatures. To this end, the finite element approach is employed. The nanotubes with different volume fractions and aspect ratios (the ratio of length to diameter) are embedded in the polymer matrix. Besides, random and regular algorithms are utilized to disperse carbon nanotubes in the matrix. It is seen that as the pure polypropylene, the elastic modulus of carbon nanotube reinforced polypropylene decreases by increasing the temperature. It is also observed that when the carbon nanotubes are dispersed parallelly and the load is applied along the nanotube directions, the largest improvement in the elastic modulus of the nanotube/polypropylene nanocomposites is obtained.

Extensor indicis proprius tendon transfer using shear wave elastography.

PubMed

Lamouille, J; Müller, C; Aubry, S; Bensamoun, S; Raffoul, W; Durand, S

2017-06-01

The means for judging optimal tension during tendon transfers are approximate and not very quantifiable. The purpose of this study was to demonstrate the feasibility of quantitatively assessing muscular mechanical properties intraoperatively using ultrasound elastography (shear wave elastography [SWE]) during extensor indicis proprius (EIP) transfer. We report two cases of EIP transfer for post-traumatic rupture of the extensor pollicis longus muscle. Ultrasound acquisitions measured the elasticity modulus of the EIP muscle at different stages: rest, active extension, active extension against resistance, EIP section, distal passive traction of the tendon, after tendon transfer at rest and then during active extension. A preliminary analysis was conducted of the distribution of values for this modulus at the various transfer steps. Different shear wave velocity and elasticity modulus values were observed at the various transfer steps. The tension applied during the transfer seemed close to the resting tension if a traditional protocol were followed. The elasticity modulus varied by a factor of 37 between the active extension against resistance step (565.1 kPa) and after the tendon section (15.3 kPa). The elasticity modulus values were distributed in the same way for each patient. The therapeutic benefit of SWE elastography was studied for the first time in tendon transfers. Quantitative data on the elasticity modulus during this test may make it an effective means of improving intraoperative adjustments. Copyright © 2017 SFCM. Published by Elsevier Masson SAS. All rights reserved.

Physics of soft hyaluronic acid-collagen type II double network gels

NASA Astrophysics Data System (ADS)

Morozova, Svetlana; Muthukumar, Murugappan

2015-03-01

Many biological hydrogels are made up of multiple interpenetrating, charged components. We study the swelling, elastic diffusion, mechanical, and optical behaviors of 100 mol% ionizable hyaluronic acid (HA) and collagen type II fiber networks. Dilute, 0.05-0.5 wt% hyaluronic acid networks are extremely sensitive to solution salt concentration, but are stable at pH above 2. When swelled in 0.1M NaCl, single-network hyaluronic acid gels follow scaling laws relevant to high salt semidilute solutions; the elastic shear modulus G' and diffusion constant D scale with the volume fraction ϕ as G' ~ϕ 9 / 4 and D ~ϕ 3 / 4 , respectively. With the addition of a collagen fiber network, we find that the hyaluronic acid network swells to suspend the rigid collagen fibers, providing extra strength to the hydrogel. Results on swelling equilibria, elasticity, and collective diffusion on these double network hydrogels will be presented.

Thermal expansion and elastic anisotropy in single crystal Al2O3 and SiC reinforcements

NASA Technical Reports Server (NTRS)

Salem, Jonathan A.; Li, Zhuang; Bradt, Richard C.

1994-01-01

In single crystal form, SiC and Al2O3 are attractive reinforcing components for high temperature composites. In this study, the axial coefficients of thermal expansion and single crystal elastic constants of SiC and Al2O3 were used to determine their coefficients of thermal expansion and Young's moduli as a function of crystallographic orientation and temperature. SiC and Al2O3 exhibit a strong variation of Young's modulus with orientation; however, their moduli and anisotropies are weak functions of temperature below 1000 C. The coefficients of thermal expansion exhibit significant temperature dependence, and that of the non-cubic Al2O3 is also a function of crystallographic orientation.

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

Heffernan, Karina M.; Ross, Nancy L.; Spencer, Elinor C.

In this study, accurate elastic constants for gadolinium phosphate (GdPO 4) have been measured by single-crystal high-pressure diffraction methods. The bulk modulus of GdPO 4 determined under hydrostatic conditions, 128.1(8) GPa (K'=5.8(2)), is markedly different from that obtained with GdPO 4 under non-hydrostatic conditions (160(2) GPa), which indicates the importance of shear stresses on the elastic response of this phosphate. Finally, high pressure Raman and diffraction analysis indicate that the PO 4 tetrahedra behave as rigid units in response to pressure and that contraction of the GdPO 4 structure is facilitated by bending/twisting of the Gd–O–P links that result inmore » increased distortion in the GdO 9 polyhedra.« less

Attenuation and Dispersion Analysis in Laboratory Measured Elastic Properties in the Middle East Carbonate Reservoir Rocks

NASA Astrophysics Data System (ADS)

Sharma, R.

2016-12-01

Carbonate rocks are sensitive to circulation of fluid types that leads to diagenetic alterations and therefore to heterogeneity in distribution of porosity and permeability. These heterogeneities in turn, lead to heterogeneity in saturations varying from partial to patchy to uniform. Depending on the interaction between fluids and rock matrix, a weakening or strengthening in shear modulus of carbonate rocks can also develop (Eberli et al., 2003; Adam et al., 2006; Sharma et al., 2009; Sharma et al., 2013). Thus the elastic response over the production life of the carbonate reservoirs can change considerably. Efforts to couple fluid flow with varying seismic properties of these reservoirs are limited in success due to the differences between static elastic properties derived from reservoir simulation and dynamic elastic properties derived from inverted seismic. An additional limitation arises from the assumption that shear modulus does not change with fluid type and saturations. To overcome these limitations, we need to understand the relationships between the static and the dynamic elastic properties using laboratory measurements made at varying pressures, frequencies and with varying saturants. I will present the following results: 1) errors associated with using dynamic (2 - 2000 Hz and 1 MHz) elastic properties data for static ( 0 Hz) reservoir properties, 2) shear modulus variation in carbonates upon saturation with varying saturants The results will enable us to estimate, 1) distribution of stress-strain relations in reservoir rocks and 2) modulus dispersion to correct seismic-derived moduli as inputs for reservoir simulators. The results are critical to estimate, 1) modulus dispersion correction and 2) occurrence and amount of shear modulus variation with fluid change vital for rock stability analysis

Bulk modulus of two-dimensional liquid dusty plasmas and its application

NASA Astrophysics Data System (ADS)

Li, Wei; Lin, Wei; Feng, Yan

2017-04-01

From the recently obtained equation of state [Feng et al., J. Phys. D: Appl. Phys. 49, 235203 (2016) and Feng et al., Phys. Plasmas 23, 093705 (2016); Erratum 23, 119904 (2016)], the bulk modulus of elasticity K of 2D liquid dusty plasmas is analytically derived as the expression of the temperature and the screening parameter. Exact values of the obtained bulk modulus of elasticity K are reported and also plotted in the 2D plane of the temperature and the screening parameter. As the temperature and the screening parameter change, the variation trend of K is reported and the corresponding interpretation is suggested. It has been demonstrated that the obtained bulk modulus of elasticity K can be used to predict the longitudinal sound speed, which agrees well with previous studies.

Effects of Cu and Ag as ternary and quaternary additions on some physical properties of SnSb7 bearing alloy

NASA Astrophysics Data System (ADS)

El-Bediwi, A. B.

2004-02-01

The structure, electrical resistivity, and elastic modulus of SnSb7 and SnSb7X (X = Cu , Ag, or Cu and Ag) rapidly solidified alloys have been investigated using X-ray diffractometer, double bridge, and dynamic resonance techniques. Copper and silver additions to SnSb result in the formation of a eutectic matrix containing embedded crystals (intermetallic phases) of SnCu, SnAg, and SnSb. The hard crystals SnCu, SnAg, and SnSb increase the overall hardness and wear resistance of SnSb bearing alloys. Addition of copper and silver improves internal friction, electrical conductivity, and elastic modulus values of SnSb rapidly solidified bearing alloys. The internal friction, elastic modulus, and electrical resistivity values are relatively sensitive to the composition of the intermediate phases in the matrix. The SbSb(7)Cu(2)g(2) has better properties (lowest internal friction, cost, adequate elastic modulus, and electrical resistivity) for bearing alloys as compared to cast iron and bronzes.

Elastic modulus of tree frog adhesive toe pads.

PubMed

Barnes, W Jon P; Goodwyn, Pablo J Perez; Nokhbatolfoghahai, Mohsen; Gorb, Stanislav N

2011-10-01

Previous work using an atomic force microscope in nanoindenter mode indicated that the outer, 10- to 15-μm thick, keratinised layer of tree frog toe pads has a modulus of elasticity equivalent to silicone rubber (5-15 MPa) (Scholz et al. 2009), but gave no information on the physical properties of deeper structures. In this study, micro-indentation is used to measure the stiffness of whole toe pads of the tree frog, Litoria caerulea. We show here that tree frog toe pads are amongst the softest of biological structures (effective elastic modulus 4-25 kPa), and that they exhibit a gradient of stiffness, being stiffest on the outside. This stiffness gradient results from the presence of a dense network of capillaries lying beneath the pad epidermis, which probably has a shock absorbing function. Additionally, we compare the physical properties (elastic modulus, work of adhesion, pull-off force) of the toe pads of immature and adult frogs.

Optimization of custom cementless stem using finite element analysis and elastic modulus distribution for reducing stress-shielding effect.

PubMed

Saravana Kumar, Gurunathan; George, Subin Philip

2017-02-01

This work proposes a methodology involving stiffness optimization for subject-specific cementless hip implant design based on finite element analysis for reducing stress-shielding effect. To assess the change in the stress-strain state of the femur and the resulting stress-shielding effect due to insertion of the implant, a finite element analysis of the resected femur with implant assembly is carried out for a clinically relevant loading condition. Selecting the von Mises stress as the criterion for discriminating regions for elastic modulus difference, a stiffness minimization method was employed by varying the elastic modulus distribution in custom implant stem. The stiffness minimization problem is formulated as material distribution problem without explicitly penalizing partial volume elements. This formulation enables designs that could be fabricated using additive manufacturing to make porous implant with varying levels of porosity. Stress-shielding effect, measured as difference between the von Mises stress in the intact and implanted femur, decreased as the elastic modulus distribution is optimized.

Mechanical evaluation of quad-helix appliance made of low-nickel stainless steel wire.

PubMed

dos Santos, Rogério Lacerda; Pithon, Matheus Melo

2013-01-01

The objective of this study was to test the hypothesis that there is no difference between stainless steel and low-nickel stainless steel wires as regards mechanical behavior. Force, resilience, and elastic modulus produced by Quad-helix appliances made of 0.032-inch and 0.036-inch wires were evaluated. Sixty Quad-helix appliances were made, thirty for each type of alloy, being fifteen for each wire thickness, 0.032-in and 0.036-in. All the archwires were submitted to mechanical compression test using an EMIC DL-10000 machine simulating activations of 4, 6, 9, and 12 mm. Analysis of variance (ANOVA) with multiple comparisons and Tukey's test were used (p < 0.05) to assess force, resilience, and elastic modulus. Statistically significant difference in the forces generated, resilience and elastic modulus were found between the 0.032-in and 0.036-in thicknesses (p < 0.05). Appliances made of low-nickel stainless steel alloy had force, resilience, and elastic modulus similar to those made of stainless steel alloy.

Compressive Strength and Modulus of Elasticity of Concrete with Cubed Waste Tire Rubbers as Coarse Aggregates

NASA Astrophysics Data System (ADS)

Haryanto, Y.; Hermanto, N. I. S.; Pamudji, G.; Wardana, K. P.

2017-11-01

One feasible solution to overcome the issue of tire disposal waste is the use of waste tire rubber to replace aggregate in concrete. We have conducted an experimental investigation on the effect of rubber tire waste aggregate in cuboid form on the compressive strength and modulus of elasticity of concrete. The test was performed on 72 cylindrical specimens with the height of 300 mm and diameter of 150 mm. We found that the workability of concrete with waste tire rubber aggregate has increased. The concrete density with waste tire rubber aggregate was decreased, and so was the compressive strength. The decrease of compressive strength is up to 64.34%. If the content of waste tire rubber aggregate is more than 40%, then the resulting concrete cannot be categorized as structural concrete. The modulus of elasticity decreased to 59.77%. The theoretical equation developed to determine the modulus of elasticity of concrete with rubber tire waste aggregate has an accuracy of 84.27%.

The Effect of Microstructure and Pre-strain on the Change in Apparent Young's Modulus of a Dual-Phase Steel

NASA Astrophysics Data System (ADS)

Kupke, A.; Hodgson, P. D.; Weiss, M.

2017-07-01

The elastic recovery in dual-phase (DP) steels is not a linear process and changes with plastic deformation. The level of change in the apparent Young's modulus has been reported to depend on material composition and microstructure, but most previous experimental studies were limited to industrial DP steels and led to contradicting results. This work represents a first fundamental study that investigates the separate and combined effect of phase volume fraction and hardness on the change in apparent Young's modulus in DP steel. A common automotive DP steel (DP780) is heat treated to obtain seven different combinations of martensite and ferrite volume fraction and hardness while keeping the chemical composition as well as the shape of the martensite and ferrite phases unchanged. Loading-unloading tests were performed to analyze the chord modulus at various levels of pre-strain. The results suggest that the point of saturation of the chord modulus with pre-strain depends on the morphology of the microstructure, occurring earlier for microstructures consisting of ferrite grains surrounded by martensite laths. It is further revealed that the reduction of the apparent Young's modulus, which is the difference between the material's initial Young's modulus and the chord modulus, increases with martensite hardness if the martensite volume fraction is kept constant. A higher martensite volume fraction initially elevates the reduction of the apparent Young's modulus. After a critical volume fraction of martensite phase of 35%, a decrease in apparent Young's modulus reduction was observed. A comparison of the plastic unloading strain suggests that the mechanisms leading to a reduction in apparent Young's modulus are strongest for the microstructure consisting of 35% martensite volume fraction.

A novel method to determine the elastic modulus of extremely soft materials.

PubMed

Stirling, Tamás; Zrínyi, Miklós

2015-06-07

Determination of the elastic moduli of extremely soft materials that may deform under their own weight is a rather difficult experimental task. A new method has been elaborated by means of which the elastic modulus of such materials can be determined. This method is generally applicable to all soft materials with purely neo-Hookean elastic deformation behaviour with elastic moduli lower than 1 kPa. Our novel method utilises the self-deformation of pendent gel cylinders under gravity. When suspended, the material at the very top bears the weight of the entire gel cylinder, but that at the bottom carries no load at all. Due to the non-uniform stress distribution along the gel sample both the stress and the resulting strain show position dependence. The cross-sectional area of the material is lowest at the top of the sample and gradually increases towards its bottom. The equilibrium geometry of the pendant gel is used to evaluate the elastic modulus. Experimental data obtained by the proposed new method were compared to the results obtained from underwater measurements. The parameters affecting the measurement uncertainty were studied by a Pareto analysis of a series of adaptive Monte Carlo simulations. It has been shown that our method provides an easily achievable method to provide an accurate determination of the elastic modulus of extremely soft matter typically applicable for moduli below 1 kPa.

Measuring the elastic properties of fine wire.

PubMed

Fallen, C T; Costello, J; Crawford, G; Schmidt, J A

2001-01-01

The elastic moduli of fine wires made from MP35N and 304SS used in implantable biomedical devices are assumed to be the same as those published in the literature. However, the cold working required to manufacture the wire significantly alters the elastic moduli of the material. We describe three experiments performed on fine wire made from MP35N and 304SS. The experimentally determined Young's and shear modulus of both wire types were significantly less than the moduli reported in the literature. Young's modulus differed by as much as 26%, and the shear modulus differed by as much as 14% from reported values.

3D Modeling Effect of Spherical Inclusions on the Magnetostriction of Bulk Superconductors

NASA Astrophysics Data System (ADS)

Zhao, Yufeng; Pan, Baocai

2018-02-01

In this paper, the dependence of the effective magnetostriction of bulk superconductors on the elastic parameters including the volume fraction and elastic modulus ratio is studied by a three-dimensional model consisting of a spherical inclusion-superconducting matrix system. The effect of the elastic modulus and volume fraction on the magnetostriction is also obtained through the magnetostriction loop. The results indicate that the elastic modulus and volume fraction have obvious effects on the effective magnetostriction of the superconducting composite, which gives an explanation about the differences between the experimental and the theoretical results. Furthermore, it is worth pointing out that the linear field dependence of magnetostriction is unique to the Bean model by comparing the curve shapes of the magnetostriction loop with and without inclusion.

Exploring phase stability, electronic and mechanical properties of Ce–Pb intermetallic compounds using first-principles calculations

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

Tao, Xiaoma; Computational Alloy Design Group, IMDEA Materials Institute, Getafe, Madrid 28906; Wang, Ziru

2016-05-15

The phase stability, electronic and mechanical properties of Ce–Pb intermetallics have been investigated by using first-principles calculations. Five stable and four metastable phases of Ce–Pb intermetallics were verified. Among them, CePb{sub 2} has been confirmed as HfGa{sub 2}-type structure. For Ce{sub 5}Pb{sub 3}, the high pressure phase transformation from D8{sub m} to D8{sub 8} with trivalent Ce has been predicted to occur at P=1.2 GPa and a high temperature phase transformation has been predicted from D8{sub m} to D8{sub 8} with tetravalent Ce at 531.5 K. The calculated lattice constants of the five stable phases are in good agreement withmore » experimental values. The electronic density of states, charge density and electron localization function of Ce{sub 3}Pb have been calculated, which indicated that the Ce and Pb show ionic behavior. The polycrystalline bulk modulus, shear modulus, Young's modulus, and Poisson's ratio are also estimated from the calculated single crystalline elastic constants. All of the calculated elastic constants satisfy mechanical stability criteria. The microhardness and mechanical anisotropy are predicted. The anisotropic nature of the Ce–Pb intermetallic compounds are demonstrated by the three-dimensional orientation dependent surfaces of Young's moduli and linear compressibility are also demonstrated. The longitudinal, transverse and average sound velocities and the Debye temperatures are also obtained in this work. The Ce{sub 3}Pb has the largest Debye temperature of 192.6 K, which means the Ce{sub 3}Pb has a highest melting point and high thermal conductivity than other compounds. - Graphical abstract: The convex hull plots of the enthalpies of formation for Ce–Pb binary systems calculated at 0 K. - Highlights: • The five stable and four metastable phases in the Ce–Pb binary system were predicted. • The crystal structure of CePb{sub 2} has been confirmed as HfGa{sub 2}-type.« less

Development of Polydimethylsiloxane Substrates with Tunable Elastic Modulus to Study Cell Mechanobiology in Muscle and Nerve

PubMed Central

Palchesko, Rachelle N.; Zhang, Ling; Sun, Yan; Feinberg, Adam W.

2012-01-01

Mechanics is an important component in the regulation of cell shape, proliferation, migration and differentiation during normal homeostasis and disease states. Biomaterials that match the elastic modulus of soft tissues have been effective for studying this cell mechanobiology, but improvements are needed in order to investigate a wider range of physicochemical properties in a controlled manner. We hypothesized that polydimethylsiloxane (PDMS) blends could be used as the basis of a tunable system where the elastic modulus could be adjusted to match most types of soft tissue. To test this we formulated blends of two commercially available PDMS types, Sylgard 527 and Sylgard 184, which enabled us to fabricate substrates with an elastic modulus anywhere from 5 kPa up to 1.72 MPa. This is a three order-of-magnitude range of tunability, exceeding what is possible with other hydrogel and PDMS systems. Uniquely, the elastic modulus can be controlled independently of other materials properties including surface roughness, surface energy and the ability to functionalize the surface by protein adsorption and microcontact printing. For biological validation, PC12 (neuronal inducible-pheochromocytoma cell line) and C2C12 (muscle cell line) were used to demonstrate that these PDMS formulations support cell attachment and growth and that these substrates can be used to probe the mechanosensitivity of various cellular processes including neurite extension and muscle differentiation. PMID:23240031

A two-layered mechanical model of the rat esophagus. Experiment and theory

PubMed Central

Fan, Yanhua; Gregersen, Hans; Kassab, Ghassan S

2004-01-01

Background The function of esophagus is to move food by peristaltic motion which is the result of the interaction of the tissue forces in the esophageal wall and the hydrodynamic forces in the food bolus. The structure of the esophagus is layered. In this paper, the esophagus is treated as a two-layered structure consisting of an inner collagen-rich submucosa layer and an outer muscle layer. We developed a model and experimental setup for determination of elastic moduli in the two layers in circumferential direction and related the measured elastic modulus of the intact esophagus to the elastic modulus computed from the elastic moduli of the two layers. Methods Inflation experiments were done at in vivo length and pressure-diameters relations were recorded for the rat esophagus. Furthermore, the zero-stress state was taken into consideration. Results The radius and the strain increased as function of pressure in the intact as well as in the individual layers of the esophagus. At pressures higher than 1.5 cmH2O the muscle layer had a larger radius and strain than the mucosa-submucosa layer. The strain for the intact esophagus and for the muscle layer was negative at low pressures indicating the presence of residual strains in the tissue. The stress-strain curve for the submucosa-mucosa layer was shifted to the left of the curves for the muscle layer and for the intact esophagus at strains higher than 0.3. The tangent modulus was highest in the submucosa-mucosa layer, indicating that the submucosa-mucosa has the highest stiffness. A good agreement was found between the measured elastic modulus of the intact esophagus and the elastic modulus computed from the elastic moduli of the two separated layers. PMID:15518591

Quantitative photoacoustic elastography of Young's modulus in humans

NASA Astrophysics Data System (ADS)

Hai, Pengfei; Zhou, Yong; Gong, Lei; Wang, Lihong V.

2017-03-01

Elastography can noninvasively map the elasticity distribution of biological tissue, which is often altered in pathological states. In this work, we report quantitative photoacoustic elastography (QPAE), capable of measuring Young's modulus of human tissue in vivo. By combining photoacoustic elastography with a stress sensor having known stress-strain behavior, QPAE can simultaneously measure strain and stress, from which Young's modulus is calculated. We first applied QPAE to quantify the Young's modulus of tissue-mimicking agar phantoms with different concentrations. The measured values fitted well with both the empirical expectations based on the agar concentrations and those measured in independent standard compression tests. We then demonstrated the feasibility of QPAE by measuring the Young's modulus of human skeletal muscle in vivo. The data showed a linear relationship between muscle stiffness and loading. The results proved that QPAE can noninvasively quantify the absolute elasticity of biological tissue, thus enabling longitudinal imaging of tissue elasticity. QPAE can be exploited for both preclinical biomechanics studies and clinical applications.

CAD-FEA modeling and analysis of different full crown monolithic restorations.

PubMed

Dal Piva, Amanda Maria de Oliveira; Tribst, João Paulo Mendes; Borges, Alexandre Luiz Souto; Souza, Rodrigo Othávio de Assunção E; Bottino, Marco Antonio

2018-06-19

To investigate the influence of different materials for monolithic full posterior crowns using 3D-Finite Element Analysis (FEA). Twelve (12) 3D models of adhesively-restored teeth with different crowns according to the material and its elastic modulus were analysed: Acrylic resin, Polyetheretherketone, Composite resin, Hybrid ceramic, pressable and machinable Zirconia reinforced lithium silicate, Feldspathic, Lithium disilicate, Gold alloy, Cobalt-Chromium alloy (Co-Cr), Zirconia tetragonal partially stabilized with yttria, and Alumina. All materials were assumed to behave elastically throughout the entire deformation. Results in restoration and cementing line were obtained using maximum principal stress. In addition, maximum shear stress criteria was used for the cementing line. Restorative materials with higher elastic modulus present higher stress concentration inside the crown, mainly tensile stress on an intaglio surface. On the other hand, materials with lower elastic modulus allow stress passage for cement, increasing shear stress on this layer. Stiffer materials promote higher stress peak values. Materials with higher elastic modulus such as Co-Cr, zirconia and alumina enable higher tensile stress concentration on the crown intaglio surface and higher shear stress on the cement layer, facilitating crown debonding. Copyright © 2018 The Academy of Dental Materials. Published by Elsevier Inc. All rights reserved.

Effect of pH on the rheological properties of borate crosslinked hydroxypropyl guar gum hydrogel and hydroxypropyl guar gum.

PubMed

Wang, Shibin; Tang, Hongbiao; Guo, Jianchun; Wang, Kunjie

2016-08-20

pH is an important factor affecting the performance of polymer fluid. The rheological properties of hydroxypropyl guar gum (HPG) base fluid and the structural strength, rheological properties, viscoelastic properties and thixotropy properties of HPG gel depend largely on the pH values. For the base fluid, an apparent viscosity-increasing effect was observed over the pH range from 7 to 11, and the apparent viscosity gradually decreased at pH 11.5-14, exhibiting electrostatic repulsion behavior and steric effects. For the HPG gel, at pH 7-12.5, the gel possessed higher apparent viscosity, higher elastic modulus (G'), lower tanδ (the ratio of the viscous modulus to the elastic modulus) and an "8"-shaped hysteresis loop, indicating stronger gel structure strength and the elastic dominant property. At pH 13-13.5, the gel samples exhibited the transition from a pseudoplastic fluid to a Newtonian fluid, and their viscosity, elastic modulus decreased but tanδ increased with the increase in pH values, exhibiting gradually weakened elastic properties. When the pH was 14, the gel mainly exhibited viscous characteristics. Copyright © 2016 Elsevier Ltd. All rights reserved.

Southern pine veneer laminates at various moduli of elasticity

Treesearch

George E. Woodson

1972-01-01

Modulus of rigidity (GLT) of veneer laminates was shown to be unrelated to dynamic modulus of elasticity (Ed) of single veneers and also, within the range of samples tested, unrelated to specific gravity. Values determined by flexure test (GLR) were consistent with those from standard plate shear...

Elasticity and inelasticity of silicon nitride/boron nitride fibrous monoliths.

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

Smirnov, B. I.; Burenkov, Yu. A.; Kardashev, B. K.

A study is reported on the effect of temperature and elastic vibration amplitude on Young's modulus E and internal friction in Si{sub 3}N{sub 4} and BN ceramic samples and Si{sub 3}N{sub 4}/BN monoliths obtained by hot pressing of BN-coated Si{sub 3}N{sub 4} fibers. The fibers were arranged along, across, or both along and across the specimen axis. The E measurements were carried out under thermal cycling within the 20-600 C range. It was found that high-modulus silicon-nitride specimens possess a high thermal stability; the E(T) dependences obtained under heating and cooling coincide well with one another. The low-modulus BN ceramicmore » exhibits a considerable hysteresis, thus indicating evolution of the defect structure under the action of thermoelastic (internal) stresses. Monoliths demonstrate a qualitatively similar behavior (with hysteresis). This behavior of the elastic modulus is possible under microplastic deformation initiated by internal stresses. The presence of microplastic shear in all the materials studied is supported by the character of the amplitude dependences of internal friction and the Young's modulus. The experimental data obtained are discussed in terms of a model in which the temperature dependences of the elastic modulus and their features are accounted for by both microplastic deformation and nonlinear lattice-atom vibrations, which depend on internal stresses.« less

Elastic moduli of δ-Pu 239 reveal aging in real time

DOE PAGES

Maiorov, Boris; Betts, Jonathan B.; Söderlind, Per; ...

2017-03-28

We study the time evolution (aging) of the elastic moduli of an eight-year-old polycrystalline δ- Pu 2.0 at % Ga alloy (δ-Pu:Ga ) from 295K to nearly 500K in real time using Resonant Ultrasound Spectroscopy (RUS). After 8 years of aging at 295K, the bulk and shear moduli increase at a normalized rate of 0.2%/year and 0.6%/year respectively. As the temperature is raised, two time dependences are observed, an exponential one of about a week, followed by a linear one (constant rate). The linear rate is thermally activated with an activation energy of 0.33+0.06 eV. Above 420K a qualitative changemore » in the time evolution is observed; the bulk modulus decreases with time while the shear modulus continues to stiffen. No change is observed as the α-β transition temperature is crossed as would be expected if a decomposition of δ-Pu:Ga to α-Pu and Pu 3Ga occurred over the temperature range studied. Our results indicate that the main mechanism of aging is creation of defects that are partially annealed starting at T = 420 K.« less

DFT investigation on electronic, magnetic, mechanical and thermodynamic properties under pressure of some EuMO3 (M  =  Ga, In) perovskites

NASA Astrophysics Data System (ADS)

Dar, Sajad Ahmad; Srivastava, Vipul; Sakalle, Umesh Kumar; Parey, Vanshree; Pagare, Gitanjali

2017-10-01

The structural, electronic, magnetic and elastic properties of cubic EuMO3 (M  =  Ga, In) perovskites has been successfully predicted within well accepted density functional theory using full potential linearized augmented plane wave (FP-LAPW). The structural study reveals ferromagnetic stability for both the compounds. The Hubbard correlation (GGA+U) calculated spin polarized electronic band and density of states presents half-metallic nature for both the compounds. The magnetic moments calculated with different approximations were found to be approximately 6 µ B for EuGaO3 and approximately 7 µ B for EuInO3. The three independent elastic constants (C 11, C 12, C 44) have been used for the prediction of mechanical properties like Young modulus (Y), Shear modulus (G), Poisson ratio (ν), Anisotropic factor (A) under pressure. The B/G ratio presents the ductile nature for both compounds. The thermodynamic parameters like specific heat capacity, thermal expansion, Grüneisen parameter and Debye temperature etc have also been analyzed in the temperature range 0-900 K and pressure range from 0 to 30 GPa.

Elastic moduli of δ-Pu 239 reveal aging in real time

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

Maiorov, Boris; Betts, Jonathan B.; Söderlind, Per

We study the time evolution (aging) of the elastic moduli of an eight-year-old polycrystalline δ- Pu 2.0 at % Ga alloy (δ-Pu:Ga ) from 295K to nearly 500K in real time using Resonant Ultrasound Spectroscopy (RUS). After 8 years of aging at 295K, the bulk and shear moduli increase at a normalized rate of 0.2%/year and 0.6%/year respectively. As the temperature is raised, two time dependences are observed, an exponential one of about a week, followed by a linear one (constant rate). The linear rate is thermally activated with an activation energy of 0.33+0.06 eV. Above 420K a qualitative changemore » in the time evolution is observed; the bulk modulus decreases with time while the shear modulus continues to stiffen. No change is observed as the α-β transition temperature is crossed as would be expected if a decomposition of δ-Pu:Ga to α-Pu and Pu 3Ga occurred over the temperature range studied. Our results indicate that the main mechanism of aging is creation of defects that are partially annealed starting at T = 420 K.« less

Deduced elasticity of sp3-bonded amorphous diamond

NASA Astrophysics Data System (ADS)

Ballato, J.; Ballato, A.

2017-11-01

Amorphous diamond was recently synthesized using high temperature and pressure techniques [Z. Zeng, L. Yang, Q. Zeng, H. Lou, H. Sheng, J. Wen, D. J. Miller, Y. Meng, W. Yang, W. L. Mao, and H. K. Mao, Nat. Commun. 8, 322 (2017)]. Here, selected physical properties of this new phase of carbon are deduced using an extension of the Voigt-Reuss-Hill (VRHx) methodology whereby single crystal values are averaged over all orientations to yield values for the amorphous analog. Specifically, the elastic constants were deduced to be c11 = 1156.5 GPa, c12 = 87.6 GPa, and c44 = 534.5 GPa, whereas the Young's modulus, bulk modulus, and Poisson's ratio were also estimated to be 1144.2 GPa, 443.9 GPa, and 0.0704, respectively. These numbers are compared with experimental and theoretical literature values for other allotropic forms, specifically, Lonsdaleite, and two forms each of graphite and amorphous carbon. It is unknown at this time how the high temperature and pressure synthesis approach employed influences the structure, hence properties, of amorphous diamond at room temperature. However, the values provided herein constitute a baseline against which future structure/property/processing analyses can be compared.

Studies on crosslinked hydroxyapatite-polyethylene composite as a bone-analogue material

NASA Astrophysics Data System (ADS)

Smolko, E.; Romero, G.

2007-08-01

The paper examines the use of different types of polymeric matrix composites in hard-tissue replacement applications. The composite samples were prepared with hydroxyapatite (HA) powder and polyethylenes of different densities. The raw material was first compounded in the extruder and the resulting composite pre-forms were compression molded into desired plates and irradiated with different doses. Modulus of elasticity in tension, tensile strength, tensile fracture strain, elongation at break and gel content were obtained for all composites. Ceramic filler distribution was investigated under scanning electron microscopy (SEM). With HA incorporated in the samples an increase in the values of Young's Modulus, (stiffness) was observed, while elongation at break decreased with the amount of filler, showing increase of brittleness. Tensile strengths at yield and at break decreased with the filler content for LD and MDPE and stayed constant for HDPE.

Mechanical behavior, electronic and phonon properties of ZrB12 under pressure

NASA Astrophysics Data System (ADS)

Li, Xiao-Hong; Yong, Yong-Liang; Cui, Hong-Ling; Zhang, Rui-Zhou

2018-06-01

The mechanical, phonon and electronic properties of ZrB12 under pressure are investigated by first-principles calculations. The research shows that ZrB12 is mechanically and dynamically stable up to 100 GPa. The elastic constants, bulk modulus B, shear modulus G, hardness Hv, B/G ratio, Debye temperature under different pressures are systematically investigated. The calculation of electronic properties shows that ZrB12 has metallic character. The Zr-d states dominate the DOS at the Fermi level, and the total DOS and PDOS change slightly with the increasing pressure. DOS (Ef) first decreases, then increases with the increasing pressure. At 50 GPa, ZrB12 has less electron carriers. The analysis of electron localization function shows that the strong B-B and Zr-B covalent bonds may be responsible for the high hardness and stability.

The effect of porosity on the mechanical properties of porous titanium scaffolds: comparative study on experimental and analytical values

NASA Astrophysics Data System (ADS)

Khodaei, Mohammad; Fathi, Mohammadhossein; Meratian, Mahmood; Savabi, Omid

2018-05-01

Reducing the elastic modulus and also improving biological fixation to the bone is possible by using porous scaffolds. In the present study, porous titanium scaffolds containing different porosities were fabricated using the space holder method. Pore distribution, formed phases and mechanical properties of titanium scaffolds were studied by Scanning Electron Microscope (SEM), x-ray diffraction (XRD) and cold compression test. Then the results of compression test were compared to the Gibson-Ashby model. Both experimentally measured and analytically calculated elastic modulus of porous titanium scaffolds decreased by porosity increment. The compliance between experimentally measured and analytically calculated elastic modulus of titanium scaffolds are also increased by porosity increment.

Emergent SO(3) Symmetry of the Frictionless Shear Jamming Transition

NASA Astrophysics Data System (ADS)

Baity-Jesi, Marco; Goodrich, Carl P.; Liu, Andrea J.; Nagel, Sidney R.; Sethna, James P.

2017-05-01

We study the shear jamming of athermal frictionless soft spheres, and find that in the thermodynamic limit, a shear-jammed state exists with different elastic properties from the isotropically-jammed state. For example, shear-jammed states can have a non-zero residual shear stress in the thermodynamic limit that arises from long-range stress-stress correlations. As a result, the ratio of the shear and bulk moduli, which in isotropically-jammed systems vanishes as the jamming transition is approached from above, instead approaches a constant. Despite these striking differences, we argue that in a deeper sense, the shear jamming and isotropic jamming transitions actually have the same symmetry, and that the differences can be fully understood by rotating the six-dimensional basis of the elastic modulus tensor.

The structural response of gadolinium phosphate to pressure

DOE PAGES

Heffernan, Karina M.; Ross, Nancy L.; Spencer, Elinor C.; ...

2016-06-16

In this study, accurate elastic constants for gadolinium phosphate (GdPO 4) have been measured by single-crystal high-pressure diffraction methods. The bulk modulus of GdPO 4 determined under hydrostatic conditions, 128.1(8) GPa (K'=5.8(2)), is markedly different from that obtained with GdPO 4 under non-hydrostatic conditions (160(2) GPa), which indicates the importance of shear stresses on the elastic response of this phosphate. Finally, high pressure Raman and diffraction analysis indicate that the PO 4 tetrahedra behave as rigid units in response to pressure and that contraction of the GdPO 4 structure is facilitated by bending/twisting of the Gd–O–P links that result inmore » increased distortion in the GdO 9 polyhedra.« less

Improving the estimate of the effective elastic modulus derived from three-point bending tests of long bones.

PubMed

Kourtis, Lampros C; Carter, Dennis R; Beaupre, Gary S

2014-08-01

Three-point bending tests are often used to determine the apparent or effective elastic modulus of long bones. The use of beam theory equations to interpret such tests can result in a substantial underestimation of the true effective modulus. In this study three-dimensional, nonlinear finite element analysis is used to quantify the errors inherent in beam theory and to create plots that can be used to correct the elastic modulus calculated from beam theory. Correction plots are generated for long bones representative of a variety of species commonly used in research studies. For a long bone with dimensions comparable to the mouse femur, the majority of the error in the effective elastic modulus results from deformations to the bone cross section that are not accounted for in the equations from beam theory. In some cases, the effective modulus calculated from beam theory can be less than one-third of the true effective modulus. Errors are larger: (1) for bones having short spans relative to bone length; (2) for bones with thin vs. thick cortices relative to periosteal diameter; and (3) when using a small radius or "knife-edge" geometry for the center loading ram and the outer supports in the three-point testing system. The use of these correction plots will enable researchers to compare results for long bones from different animal strains and to compare results obtained using testing systems that differ with regard to length between the outer supports and the radius used for the loading ram and outer supports.

Crystalline cellulose elastic modulus predicted by atomistic models of uniform deformation and nanoscale indentation

Treesearch

Xiawa Wu; Robert J. Moon; Ashlie Martini

2013-01-01

The elastic modulus of cellulose Iß in the axial and transverse directions was obtained from atomistic simulations using both the standard uniform deformation approach and a complementary approach based on nanoscale indentation. This allowed comparisons between the methods and closer connectivity to experimental measurement techniques. A reactive...

Studies on Electrical and Magnetic Properties of Mg-Substituted Nickel Ferrites

NASA Astrophysics Data System (ADS)

Chavan, Pradeep; Naik, L. R.; Belavi, P. B.; Chavan, Geeta; Ramesha, C. K.; Kotnala, R. K.

2017-01-01

The semiconducting polycrystalline ferrite materials with the general formula Ni1- x Mg x Fe2O4 were synthesized by using the solid state reaction method. X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectrographs, and atomic force microscopy techniques were utilized to study the structural parameters. XRD confirms the formation of single phase cubic spinel structure of the ferrites. The crystallite sizes of ferrites determined using the Debye-Scherer formula ranges from 0.963 μm to 1.069 μm. The cation distribution of ferrite shows that Mg2+ ions occupy a tetrahedral site ( A-site) and the Ni2+ ion occupy an octahedral site ( B-site) whereas Fe3+ ions occupies an octahedral as well as a tetrahedral site. The study of elastic parameters such as the longitudinal modulus, rigidity modulus, Young's modulus, bulk modulus, and Debye temperature were estimated using the FTIR technique. The decrease of direct current (DC) resistivity with increase in temperature indicates the semiconducting nature of ferrites. The dielectric constant as well as loss tangent decreases with increase in frequency, and at still higher frequencies, they are almost constant. This shows usual dielectric dispersion behavior attributed to the Maxwell-Wagner type of interfacial polarization and is in accordance with Koop's phenomenological theory. The linear increase of alternating current conductivity with increase of frequency shows the small polaron hopping type of conduction mechanism in all the ferrites. The magnetic properties such as saturation magnetization ( M s ), magnetic moment, coercivity, remnant magnetization ( M r ), and the ratio of M r /M s was estimated using the M-H loop.

Design of Strain-Limiting Substrate Materials for Stretchable and Flexible Electronics

PubMed Central

Ma, Yinji; Jang, Kyung-In; Wang, Liang; Jung, Han Na; Kwak, Jean Won; Xue, Yeguang; Chen, Hang; Yang, Yiyuan; Shi, Dawei; Feng, Xue

2017-01-01

Recently developed classes of electronics for biomedical applications exploit substrates that offer low elastic modulus and high stretchability, to allow intimate, mechanically biocompatible integration with soft biological tissues. A challenge is that such substrates do not generally offer protection of the electronics from high peak strains that can occur upon large-scale deformation, thereby creating a potential for device failure. The results presented here establish a simple route to compliant substrates with strain-limiting mechanics based on approaches that complement those of recently described alternatives. Here, a thin film or mesh of a high modulus material transferred onto a prestrained compliant substrate transforms into wrinkled geometry upon release of the prestrain. The structure formed by this process offers a low elastic modulus at small strain due to the small effective stiffness of the wrinkled film or mesh; it has a high tangent modulus (e.g., >1000 times the elastic modulus) at large strain, as the wrinkles disappear and the film/mesh returns to a flat geometry. This bilinear stress–strain behavior has an extremely sharp transition point, defined by the magnitude of the prestrain. A theoretical model yields analytical expressions for the elastic and tangent moduli and the transition strain of the bilinear stress–strain relation, with quantitative correspondence to finite element analysis and experiments. PMID:29033714

Design of Strain-Limiting Substrate Materials for Stretchable and Flexible Electronics.

PubMed

Ma, Yinji; Jang, Kyung-In; Wang, Liang; Jung, Han Na; Kwak, Jean Won; Xue, Yeguang; Chen, Hang; Yang, Yiyuan; Shi, Dawei; Feng, Xue; Rogers, John A; Huang, Yonggang

2016-08-02

Recently developed classes of electronics for biomedical applications exploit substrates that offer low elastic modulus and high stretchability, to allow intimate, mechanically biocompatible integration with soft biological tissues. A challenge is that such substrates do not generally offer protection of the electronics from high peak strains that can occur upon large-scale deformation, thereby creating a potential for device failure. The results presented here establish a simple route to compliant substrates with strain-limiting mechanics based on approaches that complement those of recently described alternatives. Here, a thin film or mesh of a high modulus material transferred onto a prestrained compliant substrate transforms into wrinkled geometry upon release of the prestrain. The structure formed by this process offers a low elastic modulus at small strain due to the small effective stiffness of the wrinkled film or mesh; it has a high tangent modulus (e.g., >1000 times the elastic modulus) at large strain, as the wrinkles disappear and the film/mesh returns to a flat geometry. This bilinear stress-strain behavior has an extremely sharp transition point, defined by the magnitude of the prestrain. A theoretical model yields analytical expressions for the elastic and tangent moduli and the transition strain of the bilinear stress-strain relation, with quantitative correspondence to finite element analysis and experiments.

Elasticity of microscale volumes of viscoelastic soft matter by cavitation rheometry

NASA Astrophysics Data System (ADS)

Pavlovsky, Leonid; Ganesan, Mahesh; Younger, John G.; Solomon, Michael J.

2014-09-01

Measurement of the elastic modulus of soft, viscoelastic liquids with cavitation rheometry is demonstrated for specimens as small as 1 μl by application of elasticity theory and experiments on semi-dilute polymer solutions. Cavitation rheometry is the extraction of the elastic modulus of a material, E, by measuring the pressure necessary to create a cavity within it [J. A. Zimberlin, N. Sanabria-DeLong, G. N. Tew, and A. J. Crosby, Soft Matter 3, 763-767 (2007)]. This paper extends cavitation rheometry in three ways. First, we show that viscoelastic samples can be approximated with the neo-Hookean model provided that the time scale of the cavity formation is measured. Second, we extend the cavitation rheometry method to accommodate cases in which the sample size is no longer large relative to the cavity dimension. Finally, we implement cavitation rheometry to show that the theory accurately measures the elastic modulus of viscoelastic samples with volumes ranging from 4 ml to as low as 1 μl.

High-dielectric-constant polymers as high-energy-density (HED) field effect actuator and capacitor materials

NASA Astrophysics Data System (ADS)

Huang, Cheng; Zhang, Qiming

2004-07-01

The development of high dielectric constant polymers as active materials in high-performance devices is one of the challenges in polymeric electronics and opto-electronics such as flexible thin-film capacitors, memory devices and microactuators for deformable micromirror technology. A group of poly(vinylidene fluoridetrifluoroethylene) P(VDF-TrFE) based high-dielectric-constant fluoroterpolymers have been developed, which have high room-temperature dielectric constant (K>60) and very high strain level and high energy density. The longitudinal and transverse strain of these materials can reach about -7% and 4.5%, respectively, and the elastic energy density is around 1.1 J/cm^3 under a high electric field of 150 MV/m. The influence on the electromechanical properties of copolymerizing poly(vinylidene fluoride-trifluoroethylene) (PVDF-TrFE) with a third monomer, chlorofluoroethylene (CFE), was investigated. It was found that increasing the CFE content from 0 to 8.5% slowly converts the ferroelectric structure of the copolymer to a relaxor ferroelectric system. This allows for a greatly decreased polarization and dielectric hysteresis and a much higher strain. Above 8.5%, increased CFE content substantially degrades the bulk crystallinity and the Young's modulus. These terpolymers have the potential to achieve above 10 J/cm^3 whole capacity energy density, which makes them good candidates for applications in pulse power capacitors. An all-polymer percolative composite by the combination of conductive polyaniline particles (K>10^5) within a fluoroterpolymer matrix, is introduced which exhibits very high dielectric constant (>7,000). The experimental results show that the dielectric behavior of this new class of percolative composites follows the prediction of the percolation theory and the analysis of the conductive percolation phenomena. The very high dielectric constant of the all-polymer composites which are also very flexible and possess elastic modulus not very much different from that of the insulation polymer matrix makes it possible to induce a high electromechanical response under a much reduced electric field (a strain of 2.65% with an elastic energy density of 0.18 J/cm^3 can be achieved under a low field of 16 MV/m). Data analysis also suggests that in these composites, the non-uniform local field distribution as well as interface effects can significantly enhance the strain responses. Furthermore, the experimental data as well as the data analysis indicate that the conduction loss in these composites will not affect the strain hysteresis. Flexible high dielectric constant electroactive polymers provide potential applications in high-energy-density (HED) energy storage and conversion systems such as lightweight field effect actuators and capacitors.

Alteration of Dentin-Enamel Mechanical Properties Due to Dental Whitening Treatments

PubMed Central

Zimmerman, B.; Datko, L.; Cupelli, M.; Alapati, S.; Dean, D.; Kennedy, M.

2010-01-01

The mechanical properties of dentin and enamel affect the reliability and wear properties of a tooth. This study investigated the influence of clinical dental treatments and procedures, such as whitening treatments or etching prior to restorative procedures. Both autoclaved and non-autoclaved teeth were studied in order to allow for both comparison with published values and improved clinical relevance. Nanoindentation analysis with the Oliver-Pharr model provided elastic modulus and hardness across the dentin-enamel junction (DEJ). Large increases were observed in the elastic modulus of enamel in teeth that had been autoclaved (52.0GPa versus 113.4GPa), while smaller increases were observed in the dentin (17.9GPa versus 27.9GPa). Likewise, there was an increase in the hardness of enamel (2.0GPa versus 4.3GPa) and dentin (0.5GPa versus 0.7GPa) with autoclaving. These changes suggested that the range of elastic modulus and hardness values previously reported in literature may be partially due to the sterilization procedures. Treatment of the exterior of non-autoclaved teeth with Crest Whitestrips™, Opalescence™ or UltraEtch™ caused changes in the mechanical properties of both the enamel and dentin. Those treated with Crest Whitestrips™ showed a reduction in the elastic modulus of enamel (55.3GPa to 32.7GPa) and increase in the elastic modulus of dentin (17.2GPa to 24.3GPa). Opalescence™ treatments did not significantly affect the enamel properties, but did result in a decrease in modulus of dentin (18.5GPa to 15.1GPa). Additionally, as expected, UltraEtch™ treatment decreased the modulus and hardness of enamel (48.7GPa to 38.0GPa and 1.9GPa to 1.5GPa, respectively) and dentin (21.4GPa to 15.0GPa and 1.9GPa to 1.5GPa, respectively). Changes in the mechanical properties were linked to altered protein concentration within the tooth, as evidenced by fluorescence microscopy and Fourier transform infrared spectroscopy. PMID:20346902

Effects of hydrostatic pressure and biaxial strains on the elastic and electronic properties of t-C8B2N2

NASA Astrophysics Data System (ADS)

Zhu, Haiyan; Shi, Liwei; Li, Shuaiqi; Duan, Yifeng; Zhang, Shaobo; Xia, Wangsuo

2018-04-01

The effects of hydrostatic pressure and biaxial strains on the elastic and electronic properties of a superhard material t-C8B2N2 have been studied using first-principles calculations. The structure is proven to be mechanically and dynamically stable under the applied external forces. All the elastic constants (except C66) and elastic modulus increase (decrease) with increasing pressure and compressive (tensile) biaxial strain ɛxx. A microscopic model is used to calculate the Vicker's hardness of every single bond as well as the crystal. The hardness of t-C8B2N2 (64.7 GPa) exceeds that of c-BN (62 GPa) and increases obviously by employing pressure and compressive ɛxx. Furthermore, the Debye temperature and anisotropy of sound velocities for t-C8B2N2 have been discussed. t-C8B2N2 undergoes an indirect to direct bandgap transition when ɛxx > 2%; however, the indirect bandgap character of the material remains under pressure.

Effect of pore occupancy on the acoustic properties of zeolitic imidazolate framework (ZIF)-8: A Brillouin spectroscopic study at ambient and low temperatures

NASA Astrophysics Data System (ADS)

Radhakrishnan, Dhanya; Narayana, Chandrabhas

2015-12-01

Brillouin spectroscopy is used to study the effect of pore occupancy on the elastic constants by incorporating various guest molecules into zeolitic imidazolate framework (ZIF)-8. A systematic study on the effect of mass and polarizability of the guest has been carried out by incorporating alcohols of varying chain lengths at room temperature. The interaction between the guest and host affects the elastic properties, lifetimes and guest dynamics inside the pores. The elastic anisotropy was seen to reduce upon incorporation of the guests. We have also studied the temperature dependence of the acoustic modes on gas adsorption to understand the framework flexibility. The Brillouin shift of the acoustic modes increases upon temperature dependent gas adsorption with transverse acoustic modes exhibiting a larger shift. This suggests a hardening of otherwise low shear modulus of ZIF-8. Our findings give insight into the role of guest molecules and temperature in tuning the elastic properties of ZIF-8 which is important for practical applications.

Bending elasticity of lipid membranes in presence of beta 2 glycoprotein I in the surrounding solution

NASA Astrophysics Data System (ADS)

Pavlič, J. I.; Genova, J.; Zheliaskova, A.; Iglič, A.; Mitov, M. D.

2010-11-01

Thermally induced shape fluctuations of giant quasi-spherical lipid vesicles are used to study the bending elasticity modulus kc of a phospholipid (PHLP) membranes in presence of beta 2 glycoprotein I (β2-GPI) in the aqueous solution which surrounds the vesicle's membrane. The bending elastic modulus kc of PHLP - protein membrane was obtained for different mass concentrations of β2-GPI for pure neutral SOPC membranes and for mixed SOPC: Cardiolipin negatively charged membranes. The experimental results for the bending elastic modulus kc of the PHLP membranes does not show dependence on the concentration of β2-GPI in the range from 5.5 to 55 μg/ml, when β2-GPI is present in the aqueous solution surrounding the vesicle's membrane. Obtained results are in good agreement with predictions, based on different experiments, explaining the mechanism of binding of β2-GPI to neutral membranes.

Ultrasound Shear Wave Simulation of Breast Tumor Using Nonlinear Tissue Elasticity

PubMed Central

Park, Dae Woo

2016-01-01

Shear wave elasticity imaging (SWEI) can assess the elasticity of tissues, but the shear modulus estimated in SWEI is often less sensitive to a subtle change of the stiffness that produces only small mechanical contrast to the background tissues. Because most soft tissues exhibit mechanical nonlinearity that differs in tissue types, mechanical contrast can be enhanced if the tissues are compressed. In this study, a finite element- (FE-) based simulation was performed for a breast tissue model, which consists of a circular (D: 10 mm, hard) tumor and surrounding tissue (soft). The SWEI was performed with 0% to 30% compression of the breast tissue model. The shear modulus of the tumor exhibited noticeably high nonlinearity compared to soft background tissue above 10% overall applied compression. As a result, the elastic modulus contrast of the tumor to the surrounding tissue was increased from 0.46 at 0% compression to 1.45 at 30% compression. PMID:27293476

Relationship between mechanical properties of one-step self-etch adhesives and water sorption.

PubMed

Hosaka, Keiichi; Nakajima, Masatoshi; Takahashi, Masahiro; Itoh, Shima; Ikeda, Masaomi; Tagami, Junji; Pashley, David H

2010-04-01

The purpose of this study was to evaluate the relationship between changes in the modulus of elasticity and ultimate tensile strength of one-step self-etch adhesives, and their degree of water sorption. Five one-step self-etch adhesives, Xeno IV (Dentsply Caulk), G Bond (GC Corp.), Clearfil S3 Bond (Kuraray Medical Inc.), Bond Force (Tokuyama Dental Corp.), and One-Up Bond F Plus (Tokuyama Dental Corp.) were used. Ten dumbelled-shaped polymers of each adhesive were used to obtain the modulus of elasticity by the three-point flexural bending test and the ultimate tensile strength by microtensile testing. The modulus of elasticity and the ultimate tensile strength were measured in both dry and wet conditions before/after immersion in water for 24h. Water sorption was measured, using a modification of the ISO-4049 standard. Each result of the modulus of elasticity and ultimate tensile strength was statistically analyzed using a two-way ANOVA and the result of water sorption was statistically analyzed using a one-way ANOVA. Regression analyses were used to determine the correlations between the modulus of elasticity and the ultimate tensile strength in dry or wet states, and also the percent decrease in these properties before/after immersion of water vs. water sorption. In the dry state, the moduli of elasticity of the five adhesive polymers varied from 948 to 1530 MPa, while the ultimate tensile strengths varied from 24.4 to 61.5 MPa. The wet specimens gave much lower moduli of elasticity (from 584 to 1073 MPa) and ultimate tensile strengths (from 16.5 to 35.0 MPa). Water sorption varied from 32.1 to 105.8 g mm(-3). The moduli of elasticity and ultimate tensile strengths of the adhesives fell significantly after water-storage. Water sorption depended on the constituents of the adhesive systems. The percent decreases in the ultimate tensile strengths of the adhesives were related to water sorption, while the percent reductions in the moduli of elasticity of the adhesives were not related to water sorption. Copyright (c) 2009 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

Comparative study of elastic constantd of α-, β- and Cubic- silicon nitride

NASA Astrophysics Data System (ADS)

Yao, Hongzhi; Ouyang, Lizhi; Ching, Wai-Yim

2003-03-01

Silicon nitride is an important structural ceramic and dielectric insulator. Recently, the new high pressure cubic phase of silicon nitride in spinel structure has attracted a lot of attention.^[1] We have carried out a detailed ab-initio calculation of all independent elastic constants for all three phases of Si_3N4 by using the Vienna Ab-initio Simulation Package (VASP) in both LDA and GGA approxmations. The results for β-Si_3N4 are in reasonable agreement with a experimental measurement on single crystal samples.^[2] For cubic-Si_3N4 , The three independent elastic constants are predicted to be C_11 = 504.16 GPa, C_12 = 176.66 GPa, C_44 = 326.65 GPa and a bulk modulus B = 286 GPa. This value is very close to the experimental value of 300 GPa.^[1] All these results will be compared with those obtained by using the OLCAO method based on localized orbital approach.^[3] [1]. Wai-Yim Ching, Yong-Nian Xu, Jukian D. Gale, and Manfred Ruhle, J. Am. Ceram. Soc. 81, 3189 (1998) [2]. R. Vogelgesang, M. Grimsditch, and J. S. Wallace, Appl. Phys. Lett. 76, 8 (2000) [3]. W.Y.Ching, Lizhi Ouyang, and Julian D. Gale, Phys. Rev. B61, 13, (2000)

Investigations on structural, elastic, thermodynamic and electronic properties of TiN, Ti2N and Ti3N2 under high pressure by first-principles

NASA Astrophysics Data System (ADS)

Yang, Ruike; Zhu, Chuanshuai; Wei, Qun; Du, Zheng

2016-11-01

The lattice parameters, cell volume, elastic constants, bulk modulus, shear modulus, Young's modulus and Poisson's ratio are calculated at zero pressure, and their values are in excellent agreement with the available data, for TiN, Ti2N and Ti3N2. By using the elastic stability criteria, it is shown that the three structures are all stable. The brittle/ductile behaviors are assessed in the pressures from 0 GPa to 50 GPa. Our calculations present that the performances for TiN, Ti2N and Ti3N2 become from brittle to ductile with pressure rise. The Debye temperature rises as pressure increase. With increasing N content, the enhancement of covalent interactions and decline of metallicity lead to the increase of the micro-hardness. Their constant volume heat capacities increase rapidly in the lower temperature, at a given pressure. At higher temperature, the heat capacities are close to the Dulong-Petit limit, and the heat capacities of TiN and Ti2N are larger than that of c-BN. The thermal expansion coefficients of titanium nitrides are slightly larger than that of c-BN. The band structure and the total Density of States (DOS) are calculated at 0 GPa and 50 GPa. The results show that TiN and Ti2N present metallic character. Ti3N2 present semiconducting character. The band structures have some discrepancies between 0 GPa and 50 GPa. The extent of energy dispersion increases slightly at 50 GPa, which means that the itinerant character of electrons becomes stronger at 50 GPa. The main bonding peaks of TiN, Ti2N and Ti3N2 locate in the range from -10 to 10 eV, which originate from the contribution of valance electron numbers of Ti s, Ti p, Ti d, N s and N p orbits. We can also find that the pressure makes that the total DOS decrease at the Fermi level for Ti2N. The bonding behavior of N-Ti compounds is a combination of covalent and ionic nature. As N content increases, valence band broadens, valence electron concentration increases, and covalent interactions become stronger. This is reflected in shortening of Ti-N bonds.

Standardizing lightweight deflectometer modulus measurements for compaction quality assurance : research summary.

DOT National Transportation Integrated Search

2017-09-01

The mechanistic-empirical pavement design method requires the elastic resilient modulus as the key input for characterization of geomaterials. Current density-based QA procedures do not measure resilient modulus. Additionally, the density-based metho...

Synthesis and Mechanical Characterization of Binary and Ternary Intermetallic Alloys Based on Fe-Ti-Al by Resonant Ultrasound Vibrational Methods.

PubMed

Chanbi, Daoud; Ogam, Erick; Amara, Sif Eddine; Fellah, Z E A

2018-05-07

Precise but simple experimental and inverse methods allowing the recovery of mechanical material parameters are necessary for the exploration of materials with novel crystallographic structures and elastic properties, particularly for new materials and those existing only in theory. The alloys studied herein are of new atomic compositions. This paper reports an experimental study involving the synthesis and development of methods for the determination of the elastic properties of binary (Fe-Al, Fe-Ti and Ti-Al) and ternary (Fe-Ti-Al) intermetallic alloys with different concentrations of their individual constituents. The alloys studied were synthesized from high purity metals using an arc furnace with argon flow to ensure their uniformity and homogeneity. Precise but simple methods for the recovery of the elastic constants of the isotropic metals from resonant ultrasound vibration data were developed. These methods allowed the fine analysis of the relationships between the atomic concentration of a given constituent and the Young’s modulus or alloy density.

Synthesis and Mechanical Characterization of Binary and Ternary Intermetallic Alloys Based on Fe-Ti-Al by Resonant Ultrasound Vibrational Methods

PubMed Central

Chanbi, Daoud; Amara, Sif Eddine; Fellah, Z. E. A.

2018-01-01

Precise but simple experimental and inverse methods allowing the recovery of mechanical material parameters are necessary for the exploration of materials with novel crystallographic structures and elastic properties, particularly for new materials and those existing only in theory. The alloys studied herein are of new atomic compositions. This paper reports an experimental study involving the synthesis and development of methods for the determination of the elastic properties of binary (Fe-Al, Fe-Ti and Ti-Al) and ternary (Fe-Ti-Al) intermetallic alloys with different concentrations of their individual constituents. The alloys studied were synthesized from high purity metals using an arc furnace with argon flow to ensure their uniformity and homogeneity. Precise but simple methods for the recovery of the elastic constants of the isotropic metals from resonant ultrasound vibration data were developed. These methods allowed the fine analysis of the relationships between the atomic concentration of a given constituent and the Young’s modulus or alloy density. PMID:29735946

Towards an acoustic model-based poroelastic imaging method: I. Theoretical foundation.

PubMed

Berry, Gearóid P; Bamber, Jeffrey C; Armstrong, Cecil G; Miller, Naomi R; Barbone, Paul E

2006-04-01

The ultrasonic measurement and imaging of tissue elasticity is currently under wide investigation and development as a clinical tool for the assessment of a broad range of diseases, but little account in this field has yet been taken of the fact that soft tissue is porous and contains mobile fluid. The ability to squeeze fluid out of tissue may have implications for conventional elasticity imaging, and may present opportunities for new investigative tools. When a homogeneous, isotropic, fluid-saturated poroelastic material with a linearly elastic solid phase and incompressible solid and fluid constituents is subjected to stress, the behaviour of the induced internal strain field is influenced by three material constants: the Young's modulus (E(s)) and Poisson's ratio (nu(s)) of the solid matrix and the permeability (k) of the solid matrix to the pore fluid. New analytical expressions were derived and used to model the time-dependent behaviour of the strain field inside simulated homogeneous cylindrical samples of such a poroelastic material undergoing sustained unconfined compression. A model-based reconstruction technique was developed to produce images of parameters related to the poroelastic material constants (E(s), nu(s), k) from a comparison of the measured and predicted time-dependent spatially varying radial strain. Tests of the method using simulated noisy strain data showed that it is capable of producing three unique parametric images: an image of the Poisson's ratio of the solid matrix, an image of the axial strain (which was not time-dependent subsequent to the application of the compression) and an image representing the product of the aggregate modulus E(s)(1-nu(s))/(1+nu(s))(1-2nu(s)) of the solid matrix and the permeability of the solid matrix to the pore fluid. The analytical expressions were further used to numerically validate a finite element model and to clarify previous work on poroelastography.

Elastic and thermal expansion asymmetry in dense molecular materials.

PubMed

Burg, Joseph A; Dauskardt, Reinhold H

2016-09-01

The elastic modulus and coefficient of thermal expansion are fundamental properties of elastically stiff molecular materials and are assumed to be the same (symmetric) under both tension and compression loading. We show that molecular materials can have a marked asymmetric elastic modulus and coefficient of thermal expansion that are inherently related to terminal chemical groups that limit molecular network connectivity. In compression, terminal groups sterically interact to stiffen the network, whereas in tension they interact less and disconnect the network. The existence of asymmetric elastic and thermal expansion behaviour has fundamental implications for computational approaches to molecular materials modelling and practical implications on the thermomechanical strains and associated elastic stresses. We develop a design space to control the degree of elastic asymmetry in molecular materials, a vital step towards understanding their integration into device technologies.

Composite-Based High Performance Electroactive Polymers For Remotely Controlled Mechanical Manipulations in NASA Applications

NASA Technical Reports Server (NTRS)

Zhang, Q. M.

2003-01-01

This program supported investigation of an all-polymer percolative composite which exhibits very high dielectric constant (less than 7,000). The experimental results show that the dielectric behavior of this new class of percolative composites follows the prediction of the percolation theory and the analysis of the conductive percolation phenomena. The very high dielectric constant of the all-polymer composites which are also very flexible and possess elastic modulus not very much different from that of the insulation polymer matrix makes it possible to induce a high electromechanical response under a much reduced electric field (a strain of 2.65% with an elastic energy density of 0.18 J/cu cm can be achieved under a field of 16 MV/m). Data analysis also suggests that in these composites, the non-uniform local field distribution as well as interface effects can significantly enhance the strain responses. Furthermore, the experimental data as well as the data analysis indicate that the conduction loss in these composites will not affect the strain hysteresis.

Carotid artery stiffness evaluated early by wave intensity in normal left ventricular function in post-radiotherapy patients with nasopharyngeal carcinoma.

PubMed

Zhang, Zhuo; Luo, Runlan; Tan, Bijun; Qian, Jing; Duan, Yanfang; Wang, Nan; Li, Guangsen

2018-04-01

This study aims to assess carotid elasticity early in normal left ventricular function in post-radiotherapy patients with nasopharyngeal carcinoma (NPC) by wave intensity. Sixty-seven post-radiotherapy patients all with normal left ventricular function were classified into group NPC1 and group NPC2 based on their carotid intima-media thickness. Thirty age- and sex-matched NPC patients without any history of irradiation and chemotherapy were included as a control group. Carotid parameters, including stiffness constant (β), pressure-strain elastic modulus (Ep), arterial compliance (AC), stiffness constant pulse wave velocity (PWVβ), and wave intensity pulse wave velocity (PWVWI) were measured. There were no significant differences in conventional echocardiographic variables among the three groups. In comparison with the control group, β, Ep, PWVβ, and PWVWI were significantly increased, while AC was significantly decreased in the NPC1 and NPC2 groups, and there were differences between the NPC1 group and NPC2 group (all P < 0.05). This study suggested that carotid artery stiffness increased with reduced carotid compliance in post-RT with NPC.

Investigating the thermally induced acoustoelastic effect in isotropic media with Lamb waves

PubMed Central

Dodson, Jacob C.; Inman, Daniel J.

2014-01-01

Elastic wave velocities in metallic structures are affected by variations in environmental conditions such as changing temperature. This paper extends the theory of acoustoelasticity by allowing thermally induced strains in unconstrained isotropic media, and it experimentally examines the velocity variation of Lamb waves in aluminum plates (AL-6061) due to isothermal temperature deviations. This paper presents both thermally induced acoustoelastic constants and thermally varying effective Young's modulus and Poisson's ratio which include the third order elastic material constants. The experimental thermal sensitivity of the phase velocity (∂vP/∂θ) for both the symmetric and antisymmetric modes are bounded by two theories, the acoustoelastic Lamb wave theory with thermo-acoustoelastic tensors and the thermoelastic Lamb wave theory using an effective thermo-acoustoelastic moduli. This paper shows the theoretical thermally induced acoustoelastic Lamb wave thermal sensitivity (∂vP/∂θ) is an upper bound approximation of the experimental thermal changes, but the acoustoelastic Lamb wave theory is not valid for predicting the antisymmetric (A0) phase velocity at low frequency-thickness values, <1.55 MHz mm for various temperatures. PMID:25373955

Experimental and first-principles studies on the elastic properties of α-hafnium metal under pressure

DOE PAGES

Qi, Xintong; Wang, Xuebing; Chen, Ting; ...

2016-03-30

Compressional and shear wave velocities of the α phase of hafnium have been measured up to 10.4 GPa at room temperature using ultrasonic interferometry in a multi-anvil apparatus. A finite strain equation of state analysis yielded K s0 = 110.4 (5) GPa, G 0 = 54.7(5) GPa,K s0' = 3.7 and G 0' = 0.6 for the elastic bulk and shear moduli and their pressure derivatives at ambient conditions. Complementary to the experimental data, the single crystal elastic constants, elastic anisotropy and the unit cell axial ratio c/a of α-hafnium at high pressures were investigated by Density Functional Theory (DFT)more » based first principles calculations. A c/a value of 1.605 is predicted for α-Hf at 40 GPa, which is in excellent agreement with previous experimental results. The low-pressure derivative of the shear modulus observed in our experimental data up to 10 GPa was found to originate from the elastic constant C44 which exhibits negligible pressure dependence within the current experimental pressure range. At higher pressures (>10 GPa), C 44 was predicted to soften and the shear wave velocity ν S trended to decrease with pressure, which can be interpreted as a precursor to the α-ω transition similar to that observed in other group IV elements (titanium and zirconium). Here, the acoustic velocities, bulk and shear moduli, and the acoustic Debye temperature (θ D = 240.1 K) determined from the current experiments were all compared well with those predicted by our theoretical DFT calculations.« less

Decreasing diameter fluctuation of polymer optical fiber with optimized drawing conditions

NASA Astrophysics Data System (ADS)

Çetinkaya, Onur; Wojcik, Grzegorz; Mergo, Pawel

2018-05-01

The diameter fluctuations of poly(methyl methacrylate) based polymer optical fibers, during drawing processes, have been comprehensively studied. In this study, several drawing parameters were selected for investigation; such as drawing tensions, preform diameters, preform feeding speeds, and argon flows. Varied drawing tensions were used to draw fibers, while other parameters were maintained at constant. At a later stage in the process, micro-structured polymer optical fibers were drawn under optimized drawing conditions. Fiber diameter deviations were reduced to 2.2%, when a 0.2 N drawing tension was employed during the drawing process. Higher drawing tensions led to higher diameter fluctuations. The Young’s modulus of fibers drawn with different tensions was also measured. Our results showed that fiber elasticity increased as drawing tensions decreased. The inhomogeneity of fibers was also determined by comparing the deviation of Young’s modulus.

Hydrostatic compression of Fe(1-x)O wuestite

NASA Technical Reports Server (NTRS)

Jeanloz, R.; Sato-Sorensen, Y.

1986-01-01

Hydrostatic compression measurements on Fe(0.95)O wuestite up to 12 GPa yield a room temperature value for the isothermal bulk modulus of K(ot) = 157 (+ or - 10) GPa at zero pressure. This result is in accord with previous hydrostatic and nonhydrostatic measurements of K(ot) for wuestites of composition: 0.89 = Fe/O 0.95. Dynamic measurements of the bulk modulus by ultrasonic, shock-wave and neutron-scattering experiments tend to yield a larger value: K(ot) approximately 180 GPa. The discrepancy between static and dynamic values cannot be explained by the variation of K(ot) with composition, as has been proposed. This conclusion is based on high-precision compression data and on theoretical models of the effects of defects on elastic constants. Barring serious errors in the published measurements, the available data suggest that wuestite exhibits a volume relaxation under pressure.

Cálculo del esfuerzo ideal de metales nobles mediante primeros principios en la dirección <100>

NASA Astrophysics Data System (ADS)

Bautista-Hernández, A.; López-Fuentes, M.; Pacheco-Espejel, V.; Rivas-Silva, J. F.

2005-04-01

We present calculations of the ideal strength on the < 100 > direction for noble metals (Cu, Ag and Au), by means of first principles calculations. First, we obtain the structural parameters (cell parameters, bulk modulus) for each studied metal. We deform on the < 100 > direction calculating the total energy and the stress tensor through the Hellman-Feynman theorem, by the relaxation of the unit cell in the perpendicular directions to the deformation one. The calculated cell constants differ 1.3 % from experimental data. The maximum ideal strength are 29.6, 17 and 19 GPa for Cu, Ag and Au respectively. Meanwhile, the calculated elastic modulus are 106 (Cu), 71 (Ag), and 45 GPa (Au) and are in agreement with the experimental values for polycrystalline samples. The values of maximum strength are explained by the optimum volume values due to the atomic radius size for each element.

Mechanical properties of dental tissues in dolphins (Cetacea: Delphinoidea and Inioidea).

PubMed

Loch, Carolina; Swain, Michael V; van Vuuren, Ludwig Jansen; Kieser, Jules A; Fordyce, R Ewan

2013-07-01

(1) Mammalian teeth play a major role in food acquisition and processing. While most mammals are heterodont and masticate their food, dolphins are homodont with simplified tooth morphology and negligible mastication. Understanding mechanical properties of dental tissues in dolphins is fundamental to elucidate the functional morphology and biomechanics of their feeding apparatus. This paper aims to study the hardness and elastic modulus of enamel and dentine in dolphins. (2) Teeth of 10 extant species (Inioidea and Delphinoidea) were longitudinally sectioned, polished and mounted in a UMIS nanoindenter. Indentations were performed from dentine to outer enamel. Hardness and elastic modulus were calculated using the Oliver-Pharr method. (3) Mean values of hardness and elastic modulus were similar on buccal and lingual surfaces. While dentine hardness was statistically similar among species, enamel hardness varied from 3.86GPa (±0.4) in Steno bredanensis (rough-toothed dolphin) to 2.36GPa (±0.38) in Pontoporia blainvillei (franciscana). For most species, there was a gradational increase in hardness values from inner to outer enamel. Enamel and dentine elastic modulus values clearly differed among species. In enamel, it ranged from 69.32GPa (±4.08) in the rough-toothed dolphin to 13.51GPa (±2.80) in Stenella coeruleoalba (striped dolphin). For most species, elastic modulus values were highest at inner and outer enamel. (4) Differences in mechanical properties between species, and within the enamel of each species, suggest functional implications and influence of ultrastructural arrangement and chemical composition. Copyright © 2012 Elsevier Ltd. All rights reserved.

Light-Curing Volumetric Shrinkage in Dimethacrylate-Based Dental Composites by Nanoindentation and PAL Study.

PubMed

Shpotyuk, Olha; Adamiak, Stanislaw; Bezvushko, Elvira; Cebulski, Jozef; Iskiv, Maryana; Shpotyuk, Oleh; Balitska, Valentina

2017-12-01

Light-curing volumetric shrinkage in dimethacrylate-based dental resin composites Dipol® is examined through comprehensive kinetics research employing nanoindentation measurements and nanoscale atomic-deficient study with lifetime spectroscopy of annihilating positrons. Photopolymerization kinetics determined through nanoindentation testing is shown to be described via single-exponential relaxation function with character time constants reaching respectively 15.0 and 18.7 s for nanohardness and elastic modulus. Atomic-deficient characteristics of composites are extracted from positron lifetime spectra parameterized employing unconstrained x3-term fitting. The tested photopolymerization kinetics can be adequately reflected in time-dependent changes observed in average positron lifetime (with 17.9 s time constant) and fractional free volume of positronium traps (with 18.6 s time constant). This correlation proves that fragmentation of free-volume positronium-trapping sites accompanied by partial positronium-to-positron traps conversion determines the light-curing volumetric shrinkage in the studied composites.

Diameter effect on stress-wave evaluation of modulus of elasticity of logs

Treesearch

Xiping Wang; Robert J. Ross; Brian K. Brashaw; John Punches; John R. Erickson; John W. Forsman; Roy E. Pellerin

2004-01-01

Recent studies on nondestructive evaluation (NDE) of logs have shown that a longitudinal stress-wave method can be used to nondestructively evaluate the modulus of elasticity (MOE) of logs. A strong relationship has been found between stress-wave MOE and static MOE of logs, but a significant deviation was observed between stress-wave and static values. The objective of...

Prediction of the elastic modulus of wood flour/kenaf fibre/polypropylene hybrid composites

Treesearch

Jamal Mirbagheri; Mehdi Tajvidi; Ismaeil Ghasemi; John C. Hermanson

2007-01-01

The prediction of the elastic modulus of short natural fibre hybrid composites has been investigated by using the properties of the pure composites through the rule of hybrid mixtures (RoHM) equation. In this equation, a hybrid natural fibre composite assumed as a system consisting of two separate single systems, namely particle/polymer and short-fibre/polymer systems...

Diameter effect on stress-wave evaluation of modulus of elasticity of logs

Treesearch

Xiping Wang; Robert J. Ross; Brian K. Brashaw; John R. Erickson; John W. Forsman; Roy Pellerin

2003-01-01

Recent studies on nondestructive evaluation (NDE) of logs have shown that a longitudinal stress-wave method can be used to nondestructively evaluate the modulus of elasticity (MOE) of logs. A strong relationship has been found between stress-wave MOE and static MOE of logs, but a significant deviation was observed between stress-wave and static values. The objective of...

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....

[Assessment of plantar fasciitis using shear wave elastography].

PubMed

Zhang, Lining; Wan, Wenbo; Zhang, Lihai; Xiao, Hongyu; Luo, Yukun; Fei, Xiang; Zheng, Zhixin; Tang, Peifu

2014-02-01

To assess the stiffness and thickness of the plantar fascia using shear wave elastography (SWE) in healthy volunteers of different ages and in patients with plantar fasciitis. The bilateral feet of 30 healthy volunteers and 23 patients with plantar fasciitis were examined with SWE. The plantar fascia thickness and elasticity modulus value were measured at the insertion of the calcaneus and at 1 cm from the insertion. The elderly volunteers had a significantly greater plantar fascia thickness measured using conventional ultrasound (P=0.005) and a significantly lower elasticity modulus value than the young volunteers (P=0.000). The patients with fasciitis had a significantly greater plantar fascia thickness (P=0.001) and a lower elasticity modulus value than the elderly volunteers (P=0.000). The elasticity modulus value was significantly lower at the calcaneus insertion than at 1 cm from the insertion in patients with fasciitis (P=0.000) but showed no significantly difference between the two points in the elderly or young volunteers (P=0.172, P=0.126). SWE allows quantitative assessment of the stiffness of the plantar fascia, which decreases with aging and in patients with plantar fasciitis.

Elastohydrodynamics of elliptical contacts for materials of low elastic modulus

NASA Technical Reports Server (NTRS)

Hamrock, B. J.; Dowson, D.

1983-01-01

The influence of the ellipticity parameter k and the dimensionless speed U, load W, and materials G parameters on minimum film thickness for materials of low elastic modulus was investigated. The ellipticity parameter was varied from 1 (a ball-on-plane configuration) to 12 (a configuration approaching a line contact); U and W were each varied by one order of magnitude. Seventeen cases were used to generate the minimum- and central-film-thickness relations. The influence of lubricant starvation on minimum film thickness in starved elliptical, elastohydrodynamic configurations was also investigated for materials of low elastic modulus. Lubricant starvation was studied simply by moving the inlet boundary closer to the center of the conjunction in the numerical solutions. Contour plots of pressure and film thickness in and around the contact were presented for both fully flooded and starved lubrication conditions. It is evident from these figures that the inlet pressure contours become less circular and closer to the edge of the Hertzian contact zone and that the film thickness decreases substantially as the serverity of starvation increases. The results presented reveal the essential features of both fully flooded and starved, elliptical, elastohydrodynamic conjunctions for materials of low elastic modulus.

Freeze-Thaw Durability of Air-Entrained Concrete

PubMed Central

Shang, Huai-Shuai; Yi, Ting-Hua

2013-01-01

One of the most damaging actions affecting concrete is the abrupt temperature change (freeze-thaw cycles). The types of deterioration of concrete structures by cyclic freeze-thaw can be largely classified into surface scaling (characterized by the weight loss) and internal crack growth (characterized by the loss of dynamic modulus of elasticity). The present study explored the durability of concrete made with air-entraining agent subjected to 0, 100, 200, 300, and 400 cycles of freeze-thaw. The experimental study of C20, C25, C30, C40, and C50 air-entrained concrete specimens was completed according to “the test method of long-term and durability on ordinary concrete” GB/T 50082-2009. The dynamic modulus of elasticity and weight loss of specimens were measured after different cycles of freeze-thaw. The influence of freeze-thaw cycles on the relative dynamic modulus of elasticity and weight loss was analyzed. The findings showed that the dynamic modulus of elasticity and weight decreased as the freeze-thaw cycles were repeated. They revealed that the C30, C40, and C50 air-entrained concrete was still durable after 300 cycles of freeze-thaw according to the experimental results. PMID:23576906

Freeze-thaw durability of air-entrained concrete.

PubMed

Shang, Huai-Shuai; Yi, Ting-Hua

2013-01-01

One of the most damaging actions affecting concrete is the abrupt temperature change (freeze-thaw cycles). The types of deterioration of concrete structures by cyclic freeze-thaw can be largely classified into surface scaling (characterized by the weight loss) and internal crack growth (characterized by the loss of dynamic modulus of elasticity). The present study explored the durability of concrete made with air-entraining agent subjected to 0, 100, 200, 300, and 400 cycles of freeze-thaw. The experimental study of C20, C25, C30, C40, and C50 air-entrained concrete specimens was completed according to "the test method of long-term and durability on ordinary concrete" GB/T 50082-2009. The dynamic modulus of elasticity and weight loss of specimens were measured after different cycles of freeze-thaw. The influence of freeze-thaw cycles on the relative dynamic modulus of elasticity and weight loss was analyzed. The findings showed that the dynamic modulus of elasticity and weight decreased as the freeze-thaw cycles were repeated. They revealed that the C30, C40, and C50 air-entrained concrete was still durable after 300 cycles of freeze-thaw according to the experimental results.

Elastic and transport properties of topological semimetal ZrTe

NASA Astrophysics Data System (ADS)

Guo, San-Dong; Wang, Yue-Hua; Lu, Wan-Li

2017-11-01

Topological semimetals may have substantial applications in electronics, spintronics, and quantum computation. Recently, ZrTe was predicted as a new type of topological semimetal due to the coexistence of Weyl fermions and massless triply degenerate nodal points. In this work, the elastic and transport properties of ZrTe are investigated by combining the first-principles calculations and semiclassical Boltzmann transport theory. Calculated elastic constants prove the mechanical stability of ZrTe, and the bulk modulus, shear modulus, Young’s modulus, and Poisson’s ratio also are calculated. It is found that spin-orbit coupling (SOC) has slightly enhanced effects on the Seebeck coefficient, which along the a(b) and c directions for pristine ZrTe at 300 K is 46.26 μVK-1 and 80.20 μVK-1, respectively. By comparing the experimental electrical conductivity of ZrTe (300 K) with the calculated value, the scattering time is determined as 1.59 × 10-14 s. The predicted room-temperature electronic thermal conductivity along the a(b) and c directions is 2.37 {{Wm}}-1{{{K}}}-1 and 2.90 {{Wm}}-1{{{K}}}-1, respectively. The room-temperature lattice thermal conductivity is predicted as 17.56 {{Wm}}-1{{{K}}}-1 and 43.08 {{Wm}}-1{{{K}}}-1 along the a(b) and c directions, showing very strong anisotropy. Calculated results show that isotope scattering produces an observable effect on lattice thermal conductivity. To observably reduce lattice thermal conductivity by nanostructures, the characteristic length should be smaller than 70 nm, based on cumulative lattice thermal conductivity with respect to the phonon mean free path (MFP) at 300 K. It is noted that the average room-temperature lattice thermal conductivity of ZrTe is slightly higher than that of isostructural MoP, which is due to larger phonon lifetimes and smaller Grüneisen parameters. Finally, the total thermal conductivity as a function of temperature is predicted for pristine ZrTe. Our works provide valuable information for ZrTe-based nano-electronics devices, and motivate further experimental works to study elastic and transport properties of ZrTe.

Optimization of flexible substrate by gradient elastic modulus design for performance improvement of flexible electronic devices

NASA Astrophysics Data System (ADS)

Xia, Minggang; Liang, Chunping; Hu, Ruixue; Cheng, Zhaofang; Liu, Shiru; Zhang, Shengli

2018-05-01

It is imperative and highly desirable to buffer the stress in flexible electronic devices. In this study, we designed and fabricated lamellate poly(dimethylsiloxane) (PDMS) samples with gradient elastic moduli, motivated by the protection of the pomelo pulp by its skin, followed by the measurements of their elastic moduli. We demonstrated that the electrical and fatigue performances of a Ag-nanowire thin film device on the PDMS substrate with a gradient elastic modulus are significantly better than those of a device on a substrate with a monolayer PDMS. This study provides a robust scheme to effectively protect flexible electronic devices.

Tensile properties of the human glenoid labrum

PubMed Central

Smith, C D; Masouros, S D; Hill, A M; Wallace, A L; Amis, A A; Bull, A M J

2008-01-01

Human fresh-frozen cadaveric glenoid labrae from 16 donors were harvested and ten of these had no gross degeneration. These ten were divided into eight equal circumferential sections. Each section was cut to produce test-samples from the core layer with a cross-section of 1 × 1 mm. Tensile testing was performed within a controlled environment unit at 37 ± 1 °C and 100% relative humidity. Each test-sample was precycled to a quasi-static state to alleviate the effects of deep-freezing, prior to final testing. The tangent modulus was calculated for each test-sample before and after a 5-min period of stress relaxation and at yield. The mean elastic modulus and yield stress of the glenoid labrum were 22.8 ± 11.4 and 2.5 ± 2.1 MPa, respectively. The anterosuperior portion had a lower elastic modulus and lower yield stress than the inferior portion (both P < 0.02). The pre-stress relaxation tangent modulus was significantly lower than the post-stress relaxation tangent modulus for all portions of the labrum. The glenoid labrum has similar tensile material properties to articular cartilage. Its elastic modulus varies around its circumference. This suggests that the labrum may encounter different forces at different positions. PMID:18031481

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

Zhuang, Jinda; Ju, Y. Sungtaek, E-mail: just@seas.ucla.edu

One major challenge in incorporating flexible electronics or optoelectronics on curved surfaces is the requirement of significant stretchability. We report a tunable platform for incorporating flexible and yet non-stretching device layers on a hemisphere. In this configuration, an array of planar petals contractively maps onto the surface of an inflatable hemisphere through elastocapillary interactions mediated by an interface liquid. A mechanical model is developed to elucidate the dependence of the conformality of the petal structures on their elastic modulus and thickness and the liquid surface tension. The modeling results are validated against experimental results obtained using petal structures of differentmore » thicknesses, restoring elastic spring elements of different spring constants, and liquids with different surface tension coefficients. Our platform will enable facile integration of non-stretching electronic and optoelectronic components prepared using established planar fabrication techniques on tunable hemispherical surfaces.« less

A new model linking elastic properties and ionic conductivity of mixed network former glasses.

PubMed

Wang, Weimin; Christensen, Randilynn; Curtis, Brittany; Martin, Steve W; Kieffer, John

2018-01-17

Glasses are promising candidate materials for all-solid-state electrolytes for rechargeable batteries due to their outstanding mechanical stability, wide electrochemical stability range, and open structure for potentially high conductivity. Mechanical stiffness and ionic conductivity are two key parameters for solid-state electrolytes. In this study, we investigate two mixed-network former glass systems, sodium borosilicate 0.2Na 2 O + 0.8[xBO 1.5 + (1 - x)SiO 2 ] and sodium borogermanate 0.2Na 2 O + 0.8[xBO 1.5 + (1 - x)GeO 2 ] glasses. With mixed-network formers, the structure of the network changes while the network modifier mole fraction is kept constant, i.e., x = 0.2, which allows us to analyze the effect of the network structure on various properties, including ionic conductivity and elastic properties. Besides the non-linear, non-additive mixed glass former effect, we find that the longitudinal, shear and Young's moduli depend on the combined number density of tetrahedrally and octahedrally coordinated network former elements. These units provide connectivity in three dimensions, which is required for the networks to exhibit restoring forces in response to isotropic and shear deformations. Moreover, the activation energy for modifier cation, Na + , migration is strongly correlated with the bulk modulus, suggesting that the elastic strain energy associated with the passageway dilation for the sodium ions is governed by the bulk modulus of the glass. The detailed analysis provided here gives an estimate for the number of atoms in the vicinity of the migrating cation that are affected by elastic deformation during the activated process. The larger this number and the more compliant the glass network, the lower is the activation energy for the cation jump.

Elastic, Optoelectronic and Thermoelectric Properties of the Lead-Free Halide Semiconductors Cs2AgBi X 6 ( X = Cl, Br): Ab Initio Investigation

NASA Astrophysics Data System (ADS)

Guechi, N.; Bouhemadou, A.; Bin-Omran, S.; Bourzami, A.; Louail, L.

2018-02-01

We report a detailed investigation of the elastic moduli, electronic band structure, density of states, chemical bonding, electron and hole effective masses, optical response functions and thermoelectric properties of the lead-free halide double perovskites Cs2AgBiCl6 and Cs2AgBiBr6 using the full potential linearized augmented plane wave (FP-LAPW) method with the generalized gradient approximation (GGA-PBEsol) and the Tran-Blaha modified Becke-Johnson (TB-mBJ) potential. Because of the presence of heavy elements in the studied compounds, we include the spin-orbit coupling (SOC) effect. Our calculated structural parameters agree very well with the available experimental and theoretical findings. Single-crystal and polycrystalline elastic constants are predicted using the total-energy versus strain approach. Three-dimensional representations of the crystallographic direction dependence on the shear modulus, Young's modulus and Poisson's ratio demonstrate a noticeable elastic anisotropy. The TB-mBJ potential with SOC yields an indirect band gap of 2.44 (1.93) eV for Cs2AgBiCl6 (Cs2AgBiBr6), in good agreement with the existing experimental data. The chemical bonding features are probed via density of states and valence electron density distribution calculations. Optical response functions were predicted from the calculated band structure. Both of the investigated compounds have a significant absorption coefficient (˜ 25 × 104 {cm}^{ - 1} ) in the visible range of sunlight. The thermoelectric properties of the title compounds were investigated using the FP-LAPW approach in combination with the semi-classical Boltzmann transport theory. The Cs2AgBiCl6 and Cs2AgBiBr6 compounds have a large thermopower S, which makes them potential candidates for thermoelectric applications.

A simple model for constant storage modulus of poly (lactic acid)/poly (ethylene oxide)/carbon nanotubes nanocomposites at low frequencies assuming the properties of interphase regions and networks.

PubMed

Zare, Yasser; Rhim, Sungsoo; Garmabi, Hamid; Rhee, Kyong Yop

2018-04-01

The networks of nanoparticles in nanocomposites cause solid-like behavior demonstrating a constant storage modulus at low frequencies. This study examines the storage modulus of poly (lactic acid)/poly (ethylene oxide)/carbon nanotubes (CNT) nanocomposites. The experimental data of the storage modulus in the plateau regions are obtained by a frequency sweep test. In addition, a simple model is developed to predict the constant storage modulus assuming the properties of the interphase regions and the CNT networks. The model calculations are compared with the experimental results, and the parametric analyses are applied to validate the predictability of the developed model. The calculations properly agree with the experimental data at all polymer and CNT concentrations. Moreover, all parameters acceptably modulate the constant storage modulus. The percentage of the networked CNT, the modulus of networks, and the thickness and modulus of the interphase regions directly govern the storage modulus of nanocomposites. The outputs reveal the important roles of the interphase properties in the storage modulus. Copyright © 2018 Elsevier Ltd. All rights reserved.

A theoretical approach of the relationships between collagen content, collagen cross-links and meat tenderness.

PubMed

Lepetit, J

2007-05-01

This work concerns the relationship between meat tenderness and the rubber-like properties, i.e. pressure and elastic modulus, that endomysium and perimysium connective tissues develop when meat has been heated to a temperature above which collagen contracts. For rest length meats with similar intramuscular connective tissue morphology, and which are at the same ageing state and pH, the elastic modulus of the collagenous fraction of connective tissues is approximately proportional to the total number of collagen cross-links present per volume of meat. Calculations from various published experiments concerned with the effect on tenderness of muscle type, animal age, type, and sex from different species show that this modulus follows most of the variations of meat toughness. Moreover, the proportionality between the increase in this elastic modulus and the increase in meat toughness approaches unity in situations where toughness mainly depends on connective tissues. This work demonstrates the decisive role of rubber-like properties of connective tissues in meat tenderness variations.

Design and Control of a Micro/Nano Load Stage for In-Situ AFM Observation and Nanoscale Structural and Mechanical Characterization of MWCNT-Epoxy Composites

NASA Astrophysics Data System (ADS)

Leininger, Wyatt Christopher

Nanomaterial composites hold improvement potential for many materials. Improvements arise through known material behaviors and unique nanoscale effects to improve performance in areas including elastic modulus and damping as well as various processes, and products. Review of research spurred development of a load-stage. The load stage could be used independently, or in conjunction with an AFM to investigate bulk and nanoscale material mechanics. The effect of MWCNT content on structural damping, elastic modulus, toughness, loss modulus, and glass transition temperature was investigated using the load stage, AMF, and DMA. Initial investigation showed elastic modulus increased 23% with 1wt.% MWCNT versus pure epoxy and in-situ imaging observed micro/nanoscale deformation. Dynamic capabilities of the load stage were investigated as a method to achieve higher stress than available through DMA. The system showed energy dissipation across all reinforce levels, with 480% peak for the 1wt.% MWCNT material vs. the neat epoxy at 1Hz.

Comparative study on the mechanical property of silk thread from cocoons of Bombyx mori L.

PubMed

Iizuka, E; Hachimori, A; Abe, K; Sunohara, M; Hiraide, Y; Ueyama, A; Kamo, K; Fujiwara, T; Nakamura, F; Uno, T

1983-01-01

Specimens of bave (undegummed silk thread) were collected from cocoons of various origins of parent silkworm races, such as Japanese, Chinese, European, Korean and tropical origins, and from as many races as possible. An apparatus was set up to measure the dynamic elastic modulus of these specimens. In all the categories of the races tested, the elastic modulus was linearly related to the size of bave, regardless of the portion of cocoon layer from which the specimens were taken. This correlation was concluded to be universal to the silk thread of Bombyx mori L. species; however, values of the regression coefficient and of the elastic modulus were susceptible to the origin of silkworm races, depending on whether they were native or improved.

Ab initio study of the structural, electronic, elastic and thermal conductivity properties of SrClF with pressure effects

NASA Astrophysics Data System (ADS)

Lv, Zhen-Long; Cui, Hong-Ling; Wang, Hui; Li, Xiao-Hong; Ji, Guang-Fu

2017-04-01

SrClF is an important optical crystal and can be used as pressure gauge in diamond anvil cell at high pressure. In this work, we performed a systematic study on the structural, electronic and elastic properties of SrClF under pressure, as well as its thermal conductivity, by first-principles calculation. Different exchange-correlation functionals were tested and PBESOL was finally chosen to study these properties of SrClF. Studies reveal that SrClF has a bulk modulus of about 56.2 GPa (by fitting equation of states) or 54.3 GPa (derived from elastic constants), which agree well with the experimental result. SrClF is mechanically and dynamically stable up to 50 GPa. Its elastic constants increase with the applied pressure, but its mechanical anisotropy deteriorates as the pressure increases. Investigation of its electronic properties reveals that SrClF is a direct band-gap insulator with a gap value of 5.73 eV at 0 GPa, which decreases with the increasing pressure and the reason is found by analysing the partial density of states. Based on the calculated phonon dispersion curves, thermal conductivity of SrClF is predicated. At ambient conditions, the predicted thermal conductivity is about 3.74 Wm-1 K-1, while that obtained using the simplified Slack model give a slightly larger value of 4.62 Wm-1 K-1.

Loss tangent and complex modulus estimated by acoustic radiation force creep and shear wave dispersion

PubMed Central

Amador, Carolina; Urban, Matthew W; Chen, Shigao; Greenleaf, James F

2012-01-01

Elasticity imaging methods have been used to study tissue mechanical properties and have demonstrated that tissue elasticity changes with disease state. In current shear wave elasticity imaging methods typically only shear wave speed is measured and rheological models, e.g., Kelvin-Voigt, Maxwell and Standard Linear Solid, are used to solve for tissue mechanical properties such as the shear viscoelastic complex modulus. This paper presents a method to quantify viscoelastic material properties in a model-independent way by estimating the complex shear elastic modulus over a wide frequency range using time-dependent creep response induced by acoustic radiation force. This radiation force induced creep (RFIC) method uses a conversion formula that is the analytic solution of a constitutive equation. The proposed method in combination with Shearwave Dispersion Ultrasound Vibrometry (SDUV) is used to measure the complex modulus so that knowledge of the applied radiation force magnitude is not necessary. The conversion formula is shown to be sensitive to sampling frequency and the first reliable measure in time according to numerical simulations using the Kelvin-Voigt model creep strain and compliance. Representative model-free shear complex moduli from homogeneous tissue mimicking phantoms and one excised swine kidney were obtained. This work proposes a novel model-free ultrasound-based elasticity method that does not require a rheological model with associated fitting requirements. PMID:22345425

Loss tangent and complex modulus estimated by acoustic radiation force creep and shear wave dispersion.

PubMed

Amador, Carolina; Urban, Matthew W; Chen, Shigao; Greenleaf, James F

2012-03-07

Elasticity imaging methods have been used to study tissue mechanical properties and have demonstrated that tissue elasticity changes with disease state. In current shear wave elasticity imaging methods typically only shear wave speed is measured and rheological models, e.g. Kelvin-Voigt, Maxwell and Standard Linear Solid, are used to solve for tissue mechanical properties such as the shear viscoelastic complex modulus. This paper presents a method to quantify viscoelastic material properties in a model-independent way by estimating the complex shear elastic modulus over a wide frequency range using time-dependent creep response induced by acoustic radiation force. This radiation force induced creep method uses a conversion formula that is the analytic solution of a constitutive equation. The proposed method in combination with shearwave dispersion ultrasound vibrometry is used to measure the complex modulus so that knowledge of the applied radiation force magnitude is not necessary. The conversion formula is shown to be sensitive to sampling frequency and the first reliable measure in time according to numerical simulations using the Kelvin-Voigt model creep strain and compliance. Representative model-free shear complex moduli from homogeneous tissue mimicking phantoms and one excised swine kidney were obtained. This work proposes a novel model-free ultrasound-based elasticity method that does not require a rheological model with associated fitting requirements.

Determination of Material Properties Near the Glass Transition Temperature for an Isogrid Boom

NASA Technical Reports Server (NTRS)

Blandino, Joseph R.; Woods-Vedeler, Jessica A. (Technical Monitor)

2002-01-01

Experiments were performed and results obtained to determine the temperature dependence of the modulus of elasticity for a thermoplastic isogrid tube. The isogrid tube was subjected to axial tensile loads of 0-100 lbf and strain was measured at room and elevated temperatures of 100, 120, 140, 160, 180, 190, and 200 F. These were based on tube manufacturer specifying an incorrect glass transition temperature of 210 F. Two protocols were used. For the first protocol the tube was brought to temperature and a tensile test performed. The tube was allowed to cool between tests. For the second protocol the tube was ramped to the desired test temperature and held. A tensile test was performed and the tube temperature ramped to the next test temperature. The second protocol spanned the entire test range. The strain rate was constant at 0.008 in/min. Room temperature tests resulted in the determination of an average modulus of 2.34 x 106 Psi. The modulus decreased above 100 F. At 140 F the modulus had decreased by 7.26%. The two test protocols showed good agreement below 160 F. At this point the glass transition temperature had been exceeded. The two protocols were not repeated because the tube failed.

Surface coating influence on elastic properties of spruce wood by means of holographic vibration mode visualization

NASA Astrophysics Data System (ADS)

Bongova, M.; Urgela, Stanislav

1999-07-01

Physicoacoustical properties of wood influenced by surface coating are studied by modal analysis. Resonant spruce plates were coated by stain, nitrocellulose varnish, special violin paint and shellac. The modal testing was performed by electronic speckle pattern interferometry. For this purpose, equipment called VIBROVIZER was used. The collected values of physicoacoustical characteristics (density, Young's modulus, acoustic constant) were compared using the graphic plots of data. The 3D plots help to evaluate wooden plates from a viewpoint of the quality control. This fact offers new opportunity for musical instrument manufacturers.

Frequency characteristics of vibration generated by dual acoustic radiation force for estimating viscoelastic properties of biological tissues

NASA Astrophysics Data System (ADS)

Watanabe, Ryoichi; Arakawa, Mototaka; Kanai, Hiroshi

2018-07-01

We proposed a new method for estimating the viscoelastic property of the local region of a sample. The viscoelastic parameters of the phantoms simulating the biological tissues were quantitatively estimated by analyzing the frequency characteristics of displacement generated by acoustic excitation. The samples were locally strained by irradiating them with the ultrasound simultaneously generated from two point-focusing transducers by applying the sum of two signals with slightly different frequencies of approximately 1 MHz. The surface of a phantom was excited in the frequency range of 20–2,000 Hz, and its displacement was measured. The frequency dependence of the acceleration provided by the acoustic radiation force was also measured. From these results, we determined the frequency characteristics of the transfer function from the stress to the strain and estimated the ratio of the elastic modulus to the viscosity modulus (K/η) by fitting the data to the Maxwell model. Moreover, the elastic modulus K was separately estimated from the measured sound velocity and density of the phantom, and the viscosity modulus η was evaluated by substituting the estimated elastic modulus into the obtained K/η ratio.

A highly aromatic and sulfonated ionomer for high elastic modulus ionic polymer membrane micro-actuators

NASA Astrophysics Data System (ADS)

Hatipoglu, Gokhan; Liu, Yang; Zhao, Ran; Yoonessi, Mitra; Tigelaar, Dean M.; Tadigadapa, Srinivas; Zhang, Q. M.

2012-05-01

A high modulus, sulfonated ionomer synthesized from 4,6-bis(4-hydroxyphenyl)-N,N-diphenyl-1,3,5-triazin-2-amine and 4,4‧-biphenol with bis(4-fluorophenyl)sulfone (DPA-PS:BP) is investigated for ionic polymer actuators. The uniqueness of DPA-PS:BP is that it can have a high ionic liquid (IL) uptake and consequently generates a high intrinsic strain response, which is >1.1% under 1.6 V while maintaining a high elastic modulus (i.e. 600 MPa for 65 vol% IL uptake). Moreover, such a high modulus of the active ionomer, originating from the highly aromatic backbone and side-chain-free structure, allows for the fabrication of free-standing thin film micro-actuators (down to 5 µm thickness) via the solution cast method and focused-ion-beam milling, which exhibits a much higher bending actuation, i.e. 43 µm tip displacement and 180 kPa blocking stress for a 200 µm long and 5 µm thick cantilever actuator, compared with the ionic actuators based on traditional ionomers such as Nafion, which has a much lower elastic modulus (50 MPa) and actuation strain.

A summary of modulus of elasticity and knot size surveys for laminating grades of lumber

Treesearch

R. W. Wolfe; R. C. Moody

1981-01-01

A summary of modulus of elasticity (MOE) and knot data is presented for grades of lumber commonly used to manufacture glued-laminated (glulam) timber by the laminating Industry. Tabulated values represent 30 different studies covering a time span of over 16 years. Statistical estimates of average and near-maximum knot sizes as well as mean and coefficient of variation...

Genetic variation in basic density and modulus of elasticity of coastal Douglas-fir.

Treesearch

G.R. Johnson; B.L. Gartner

2006-01-01

Douglas-fir trees from 39 open-pollinated families at four test locations were assessed to estimate heritability of modulus of elasticity (MOE) and basic density. Heritability estimates of MOE (across-site h = 0.55) were larger than those for total height (0.15) and diameter at breast height (DBH; 0.29), and similar to those for density (0.59)....

Modulus of elasticity loss as a rapid indicator of rot-fungal attack on untreated and preservative-treated wood in laboratory tests

Treesearch

Xingxia Ma; Grant T. Kirker; Carol A. Clausen; Mingliang Jiang; Haibin Zhou

2017-01-01

The modulus of elasticity (MOE) of wood is a sensitive indicator of rotfungal attack. To develop an alternative method of rapid assessment of fungal decay in the laboratory, changes in static MOE of untreated and preservative-treated wood were measured during exposure to the brownrot fungus, Gloeophyllum trabeum, and the white-rot fungus, Trametes...

The Effect of Water Molecules on Mechanical Properties of Cell Walls

NASA Astrophysics Data System (ADS)

Rahbar, Nima; Youssefian, Sina

The unique properties of bamboo fibers come from their natural composite structures that comprise mainly cellulose nanofibrils in a matrix of intertwined hemicellulose and lignin called lignin-carbohydrate complex (LCC). Here, we have utilized atomistic simulations to investigate the mechanical properties and mechanisms of interactions between these materials, in the presence of water molecules. The role of hemicellulose found to be enhancing the mechanical properties and lignin found to be providing the strength of bamboo fibers. The abundance of Hbonds in hemicellulose chains is responsible for improving the mechanical behavior of LCC. The strong van der Waals forces between lignin molecules and cellulose nanofibrils are responsible for higher adhesion energy between LCC/cellulose nanofibrils. We also found out that the amorphous regions of cellulose nanofibrils is the weakest interface in bamboo Microfibrils. In presence of water, the elastic modulus of lignin increases at low water content and decreases in higher water content, whereas the hemicellulose elastic modulus constantly decreases. The variations of Radial Distribution Function and Free Fractional Volume of these materials with water suggest that water molecules enhance the mechanical properties of lignin by filling voids in the system and creating Hbond bridges between polymer chains. For hemicellulose, however, the effect is always regressive due to the destructive effect of water molecules on the Hbond of its dense structure.

Coupling of a structural analysis and flow simulation for short-fiber-reinforced polymers: property prediction and transfer of results

NASA Astrophysics Data System (ADS)

Kröner, C.; Altenbach, H.; Naumenko, K.

2009-05-01

The aim of this paper is to discuss the basic theories of interfaces able to transfer the results of an injection molding analyis of fiber-reinforced polymers, performed by using the commercial computer code Moldflow, to the structural analysis program ABAQUS. The elastic constants of the materials, such as Young's modulus, shear modulus, and Poisson's ratio, which depend on both the fiber content and the degree of fiber orientation, were calculated not by the usual method of "orientation averaging," but with the help of linear functions fitted to experimental data. The calculation and transfer of all needed data, such as material properties, geometry, directions of anisotropy, and so on, is performed by an interface developed. The interface is suit able for midplane elements in Moldflow. It calculates and transfers to ABAQUS all data necessary for the use of shell elements. In addition, a method is described how a nonlinear orthotropic behavior can be modeled starting from the generalized Hooke's law. It is also shown how such a model can be implemented in ABAQUS by means of a material subroutine. The results obtained according to this subroutine are compared with those based on an orthotropic, linear, elastic simulation.

Visualising elastic anisotropy: theoretical background and computational implementation

NASA Astrophysics Data System (ADS)

Nordmann, J.; Aßmus, M.; Altenbach, H.

2018-02-01

In this article, we present the technical realisation for visualisations of characteristic parameters of the fourth-order elasticity tensor, which is classified by three-dimensional symmetry groups. Hereby, expressions for spatial representations of uc(Young)'s modulus and bulk modulus as well as plane representations of shear modulus and uc(Poisson)'s ratio are derived and transferred into a comprehensible form to computer algebra systems. Additionally, we present approaches for spatial representations of both latter parameters. These three- and two-dimensional representations are implemented into the software MATrix LABoratory. Exemplary representations of characteristic materials complete the present treatise.

Measurement of the Elastic Modulus of a Single Boron Nitride Nanotube

NASA Astrophysics Data System (ADS)

Chopra, Nasreen G.; Cohen, Marvin L.; Louie, Steven G.; Zettl, A.

1997-03-01

In situ transmission electron microscope (TEM) measurements of thermally-excited vibrational characteristics of boron nitride (BN) nanotubes are used to extract the elastic modulus. We find BN nanotubes to have a higher axial Young's modulus, 1.2 TPa, than any other insulating fiber. This value is consistent with theoretical predictions and confirms previous TEM observations of the high degree of crystallinity of these structures. This work was supported by the U. S. Department of Energy under contract No. DE-AC03-76-SF00098 and the Office of Naval Research, Order No. N00014-95-F-0099

Study of phonon modes and elastic properties of Sc36Al24Co20Y20 and Gd36Al24Co20Y20 rare-earth bulk metallic glasses

NASA Astrophysics Data System (ADS)

Suthar, P. H.; Gajjar, P. N.; Thakore, B. Y.; Jani, A. R.

2013-04-01

A phonon modes and elastic properties of two different rare-earth based bulk metallic glasses Sc36Al24Co20Y20 and Gd36Al24Co20Y20 are computed using Hubbard-Beeby approach and our well established model potential. The local field correlation functions due to Hartree (H), Taylor (T), Ichimaru and Utsumi (IU), Farid et al (F) and Sarkar Sen et al (S) are employed to investigate the influence of the screening effects on the vibrational dynamics of Sc36Al24Co20Y20 and Gd36Al24Co20Y20 bulk metallic glasses. The results for bulk modulus BT, modulus of rigidity G, Poisson's ratio ξ, Young's modulus Y, Debye temperature ΘD, propagation velocity of elastic waves and dispersion curves are reported. The computed elastic properties are found to be in good agreement with experimental and other available data.

Correlating off-axis tension tests to shear modulus of wood-based panels

Treesearch

Edmond P. Saliklis; Robert H. Falk

2000-01-01

The weakness of existing relationships correlating off-axis modulus of elasticity E q to shear modulus G 12 for wood composite panels is demonstrated through presentation of extensive experimental data. A new relationship is proposed that performs better than existing equations found in the literature. This relationship can be manipulated to calculate the shear modulus...

Physical property measurements of doped cesium iodide crystals

NASA Technical Reports Server (NTRS)

Synder, R. S.; Clotfelter, W. N.

1974-01-01

Mechanical and thermal property values are reported for crystalline cesium iodide doped with sodium and thallium. Young's modulus, bulk modulus, shear modulus, and Poisson's ratio were obtained from ultrasonic measurements. Young's modulus and the samples' elastic and plastic behavior were also measured under tension and compression. Thermal expansion and thermal conductivity were the temperature dependent measurements that were made.

Alteration of dentin-enamel mechanical properties due to dental whitening treatments.

PubMed

Zimmerman, B; Datko, L; Cupelli, M; Alapati, S; Dean, D; Kennedy, M

2010-05-01

The mechanical properties of dentin and enamel affect the reliability and wear properties of a tooth. This study investigated the influence of clinical dental treatments and procedures, such as whitening treatments or etching prior to restorative procedures. Both autoclaved and non-autoclaved teeth were studied in order to allow for both comparison with published values and improved clinical relevance. Nanoindentation analysis with the Oliver-Pharr model provided elastic modulus and hardness across the dentin-enamel junction (DEJ). Large increases were observed in the elastic modulus of enamel in teeth that had been autoclaved (52.0 GPa versus 113.4 GPa), while smaller increases were observed in the dentin (17.9 GPa versus 27.9 GPa). Likewise, there was an increase in the hardness of enamel (2.0 GPa versus 4.3 GPa) and dentin (0.5 GPa versus 0.7 GPa) with autoclaving. These changes suggested that the range of elastic modulus and hardness values previously reported in the literature may be partially due to the sterilization procedures. Treatment of the exterior of non-autoclaved teeth with Crest Whitestrips, Opalescence or UltraEtch caused changes in the mechanical properties of both the enamel and dentin. Those treated with Crest Whitestrips showed a reduction in the elastic modulus of enamel (55.3 GPa to 32.7 GPa) and increase in the elastic modulus of dentin (17.2 GPa to 24.3 GPa). Opalescence treatments did not significantly affect the enamel properties, but did result in a decrease in the modulus of dentin (18.5 GPa to 15.1 GPa). Additionally, as expected, UltraEtch treatment decreased the modulus and hardness of enamel (48.7 GPa to 38.0 GPa and 1.9 GPa to 1.5 GPa, respectively) and dentin (21.4 GPa to 15.0 GPa and 1.9 GPa to 1.5 GPa, respectively). Changes in the mechanical properties were linked to altered protein concentration within the tooth, as evidenced by fluorescence microscopy and Fourier transform infrared spectroscopy. Published by Elsevier Ltd.

A Comparative Study of Structural Stability and Mechanical and Optical Properties of Fluorapatite (Ca5(PO4)3F) and Lithium Disilicate (Li2Si2O5) Components Forming Dental Glass-Ceramics: First Principles Study

NASA Astrophysics Data System (ADS)

Biskri, Z. E.; Rached, H.; Bouchear, M.; Rached, D.; Aida, M. S.

2016-10-01

The aim of this paper is a comparative study of structural stability and mechanical and optical properties of fluorapatite (FA) (Ca5(PO4)3F) and lithium disilicate (LD) (Li2Si2O5), using the first principles pseudopotential method based on density functional theory (DFT) within the generalized gradient approximation (GGA). The stability of fluorapatite and lithium disilicate compounds has been evaluated on the basis of their formation enthalpies. The results show that fluorapatite is more energetically stable than lithium disilicate. The independent elastic constants and related mechanical properties, including bulk modulus ( B), shear modulus ( G), Young's modulus ( E) and Poisson's ratio ( ν) as well as the Vickers hardness ( H v), have been calculated for fluorapatite compound and compared with other theoretical and experimental results. The obtained values of the shear modulus, Young's modulus and Vickers hardness are smaller in comparison with those of lithium disilicate compound, implying that lithium disilicate is more rigid than fluorapatite. The brittle and ductile properties were also discussed using B/ G ratio and Poisson's ratio. Optical properties such as refractive index n( ω), extinction coefficient k( ω), absorption coefficient α( ω) and optical reflectivity R( ω) have been determined from the calculations of the complex dielectric function ɛ( ω), and interpreted on the basis of the electronic structures of both compounds. The calculated values of static dielectric constant ɛ 1(0) and static refractive index n(0) show that the Li2Si2O5 compound has larger values compared to those of the Ca5(PO4)3F compound. The results of the extinction coefficient show that Li2Si2O5 compound exhibits a much stronger ultraviolet absorption. According to the absorption and reflectivity spectra, we inferred that both compounds are theoretically the best visible and infrared transparent materials.

Acute effect and time course of extension and internal rotation stretching of the shoulder on infraspinatus muscle hardness.

PubMed

Kusano, Ken; Nishishita, Satoru; Nakamura, Masatoshi; Tanaka, Hiroki; Umehara, Jun; Ichihashi, Noriaki

2017-10-01

A decrease in flexibility of the infraspinatus muscle causes limitations in the range of shoulder motion. Static stretching (SS) is a useful method to improve muscle flexibility and joint mobility. Previous researchers investigated effective stretching methods for the infraspinatus. However, few researchers investigated the acute effect of SS on the infraspinatus muscle's flexibility. In addition, the minimum SS time required to increase the infraspinatus muscle's flexibility remains unclear. The aims of this study included investigating the acute effect of SS on the infraspinatus muscle's hardness (an index of muscle flexibility) by measuring shear elastic modulus and determining minimum SS time to decrease the infraspinatus muscle's hardness. This included measuring the effect of SS with extension and internal rotation of the shoulder on the infraspinatus muscle's hardness in 20 healthy men. Hence, shear elastic modulus of the infraspinatus was measured by ultrasonic shear wave elastography before and after every 10 seconds up to 120 seconds of SS. Two-way analysis of variance indicated a significant main effect of SS duration on shear elastic modulus. The post hoc test indicated no significant difference between shear elastic modulus after 10 seconds of SS and that before SS. However, shear elastic modulus immediately after a period ranging from 20 seconds to 120 seconds of SS was significantly lower than that before SS. The results suggested that shoulder extension and internal rotation SS effectively decreased the infraspinatus muscle's hardness. In addition, the results indicated that a period exceeding 20 seconds of SS decreased the infraspinatus muscle's hardness. Copyright © 2017 Journal of Shoulder and Elbow Surgery Board of Trustees. Published by Elsevier Inc. All rights reserved.

The Value of Elastic Modulus Index as a Novel Surrogate Marker for Cardiovascular Risk Stratification by Dimensional Speckle-Tracking Carotid Ultrasonography

PubMed Central

Yoon, Ji Hyun; Cho, In-Jeong; Sung, Ji Min; Lee, Jinyong; Ryoo, Hojin; Shim, Chi Young; Hong, Geu-Ru; Chung, Namsik

2016-01-01

Background Carotid intima media thickness (CIMT) and the presence of carotid plaque have been used for risk stratification of cardiovascular disease (CVD). To date, however, the association between multi-directional functional properties of carotid artery and CVD has not been fully elucidated. We sought to explore the multi-directional mechanics of the carotid artery in relation to cardiovascular risk. Methods Four hundred one patients who underwent carotid ultrasound were enrolled between January 2010 and April 2013. A high risk of CVD was defined as more than 20% of 10-year risk based on the Framingham risk score. Using a speckle-tracking technique, the longitudinal and radial movements were analyzed in the B-mode images. Peak longitudinal and radial displacements, strain and strain rate were also measured. Beta stiffness and elastic modulus index were calculated from the radial measurements. Results Of the overall sample, 13% (52) of patients comprised the high-risk group. In multivariate logistic regression, CIMT and elastic modulus index were independently associated with a high-risk of CVD {odds ratio (OR): 1.810 [95% confidence interval (CI) 1.249–2.622] and OR: 1.767 (95% CI: 1.177–2.652); p = 0.002, 0.006, respectively}. The combination of CIMT and elastic modulus index correlated with a high-risk of CVD more so than CIMT alone. Conclusion The elastic modulus index of the carotid artery might serve as a novel surrogate marker of high-risk CVD. Measurement of the multi-directional mechanics of the carotid artery using the speckle tracking technique has potential for providing further information over conventional B-mode ultrasound for stratification of CVD risk. PMID:27721952

Influence of sickle hemoglobin polymerization and membrane properties on deformability of sickle erythrocytes in the microcirculation.

PubMed Central

Dong, C; Chadwick, R S; Schechter, A N

1992-01-01

The rheological properties of normal erythrocytes appear to be largely determined by those of the red cell membrane. In sickle cell disease, the intracellular polymerization of sickle hemoglobin upon deoxygenation leads to a marked increase in intracellular viscosity and elastic stiffness as well as having indirect effects on the cell membrane. To estimate the components of abnormal cell rheology due to the polymerization process and that due to the membrane abnormalities, we have developed a simple mathematical model of whole cell deformability in narrow vessels. This model uses hydrodynamic lubrication theory to describe the pulsatile flow in the gap between a cell and the vessel wall. The interior of the cell is modeled as a Voigt viscoelastic solid with parameters for the viscous and elastic moduli, while the membrane is assigned an elastic shear modulus. In response to an oscillatory fluid shear stress, the cell--modeled as a cylinder of constant volume and surface area--undergoes a conical deformation which may be calculated. We use published values of normal and sickle cell membrane elastic modulus and of sickle hemoglobin viscous and elastic moduli as a function of oxygen saturation, to estimate normalized tip displacement, d/ho, and relative hydrodynamic resistance, Rr, as a function of polymer fraction of hemoglobin for sickle erythrocytes. These results show the transition from membrane to internal polymer dominance of deformability as oxygen saturation is lowered. More detailed experimental data, including those at other oscillatory frequencies and for cells with higher concentrations of hemoglobin S, are needed to apply fully this approach to understanding the deformability of sickle erythrocytes in the microcirculation. The model should be useful for reconciling the vast and disparate sets of data available on the abnormal properties of sickle cell hemoglobin and sickle erythrocyte membranes, the two main factors that lead to pathology in patients with this disease. PMID:1420913

Effects of ion irradiation on the surface mechanical behavior of hybrid sol-gel derived silicate thin films

NASA Astrophysics Data System (ADS)

Ghisleni, Rudy

A study on the effects of ion irradiation on the surface mechanical behavior of hybrid sol-gel derived thin films has been performed. Hybrid organic/inorganic modified silicate thin films were synthesized by sol-gel processing from tetraethoxysilane (TEOS) and methyltriethoxysilane (MTES) precursors and spin-coated onto (100) Si substrates. The synthesized films were investigated by nanoindentation, photoluminescence spectroscopy, and Raman spectroscopy. Hybrid TEOS/MTES sol-gel films modified by ion irradiation with deposited electronic energies of 1.87 x 1025 eV/cm3 or higher showed higher values of reduced elastic modulus and hardness than 800°C heat treated films. Thus, ion irradiation was found to be an effective means in converting the polymer sol into ceramic type coatings. The ions used in this study were Cu2+, N2+, Si+, O+, N+, He+, and H+, with incident energies ranging from 100 keV to 2 MeV, and fluences ranging from 1 x 1014 to 1 x 1017 ions/cm2. Both the reduced elastic modulus and hardness were seen to increase monotonically with the increase in ion fluence, with an observed maximum hardness of 7.7 GPa (an unirradiated film hardness was 0.4 GPa) and a maximum reduced elastic modulus of 84.0 GPa (an unirradiated film reduced elastic modulus was 7.1 GPa) for 250 keV N2+ irradiation with a 5 x 1016 ions/cm2 fluence. The electronic stopping power was found to be principally responsible for the film hardening, while the role of nuclear stopping power was minimal. A monotonic increase in hardness with increase in electronic energy deposited to the film surface was found. A model describing the hardening of ion irradiated films was developed. This model characterizes the hardening effectiveness of the ion species considered by two parameters: the constant hardening cross-section and the hardening coefficient. Where the hardening cross-section represents the cross-sectional area hardened by the interaction of an incident ion with the target, and the hardening coefficient represents an index of the cross-sectional area gradient as a function of fluence. The increase in hardness of hybrid sol-gel films following ion irradiation was linked to structural changes. Ion irradiation results in a cross-linked silica film as well as the segregation of amorphous carbon clusters, both of which contributed to increase the mechanical properties of the films.

First-principles investigation of thermodynamic, elastic and electronic properties of Al{sub 3}V and Al{sub 3}Nb intermetallics under pressures

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

Chen, Zhe; Zhang, Peng; Chen, Dong

2015-02-28

The thermodynamic, elastic, and electronic properties of D0{sub 22}-type Al{sub 3}V and Al{sub 3}Nb intermetallics were studied using the first-principle method. The results showed the pressure has profound effects on the structural, mechanical and electronic properties in both Al{sub 3}V and Al{sub 3}Nb. Thermodynamically, the formation enthalpies for Al{sub 3}V and Al{sub 3}Nb were derived, which agreed well with available experimental and theoretical values. Comparably, Al{sub 3}Nb was a more stable phase with the more negative H{sub f} than Al{sub 3}V. Mechanically, the calculated elastic constants showed linearly increasing tendencies, and satisfied the Born's criteria from 0–20 GPa, indicating the mechanicallymore » stability of Al{sub 3}V and Al{sub 3}Nb under this pressure range. Further, the mechanical parameters (i.e., bulk modulus (B), shear modulus (G), and Young's modulus (E)) were derived using the Voigt-Reuss-Hill (VRH) method, and in good agreement with available experimental results at the ground state. All these parameters presented the linearly increasing dependences on the external pressure. The B/G ratios and Poisson's ratio indicated that the Al{sub 3}V and Al{sub 3}Nb crystals should exhibit brittle behavior at 0–20 GPa. Additionally, the bulk modulus can be obtained through fitting the Birch-Murnaghan equation (B{sub 0}), computing by VRH method (B{sub H}), and deriving from the elastic theory (B{sub relax}) in both intermetallics. The uniformity of these calculated bulk moduli in each compound exhibited the excellent reliability and self-consistency. In addition, Debye temperature was estimated from the average sound velocity. The Debye temperature showed an increasing dependence on the pressures. Finally, through density of states analysis, Al{sub 3}V and Al{sub 3}Nb were suggested to possess naturally metallic behavior. Under pressures, it was noted that the shapes of peaks and pseudogaps exhibited relative few changes, suggesting Al{sub 3}V and Al{sub 3}Nb has kept structurally stable up to 20 GPa. At zero pressure, Al{sub 3}Nb was considered as a more structurally stable phase with the more number of bonding electrons per atom than Al{sub 3}V. This conclusion was in consistent with the one drawn from the thermodynamic analysis.« less

Release characteristics of reattached barnacles to non-toxic silicone coatings.

PubMed

Kim, Jongsoo; Nyren-Erickson, Erin; Stafslien, Shane; Daniels, Justin; Bahr, James; Chisholm, Bret J

2008-01-01

Release mechanisms of barnacles (Amphibalanus amphitrite or Balanus amphitrite) reattached to platinum-cured silicone coatings were studied as a function of coating thickness (210-770 microm), elastic modulus (0.08-1.3 MPa), and shear rate (2-22 microm s(-1)). It was found that the shear stress of the reattached, live barnacles necessary to remove from the silicone coatings was controlled by the combined term (E/t)(0.5) of the elastic modulus (E) and thickness (t). As the ratio of the elastic modulus to coating thickness decreased, the barnacles were more readily removed from the silicone coatings, showing a similar release behavior to pseudobarnacles (epoxy glue). The barnacle mean shear stress ranged from 0.017 to 0.055 MPa whereas the pseudobarnacle mean shear stress ranged from 0.022 to 0.095 MPa.

Experimental and theoretical modal analysis of full-sized wood composite panels supported on four nodes

Treesearch

Cheng Guan; Houjiang Zhang; Xiping Wang; Hu Miao; Lujing Zhou; Fenglu Liu

2017-01-01

Key elastic properties of full-sized wood composite panels (WCPs) must be accurately determined not only for safety, but also serviceability demands. In this study, the modal parameters of full-sized WCPs supported on four nodes were analyzed for determining the modulus of elasticity (E) in both major and minor axes, as well as the in-plane shear modulus of panels by...

Comparison of Nondestructive Testing Methods for Evaluating No. 2 Southern Pine Lumber: Part A, Modulus of Elasticity

Treesearch

B.Z. Yang; R.D. Seale; R. Shmulsky; J. Dahlen; Xiping Wang

2015-01-01

Modulus of elasticity (MOE, or E) is one of the main quality indicators in structural lumber stress grading systems. Due to a relatively high amount of variability in contemporary sawn lumber, it is important that nondestructive evaluation technology be utilized to better discern high-E-value pieces from low-E-value pieces. The research described in this study is from...

Modeling temperature effect on dynamic modulus of elasticity of red pine (Pinus resinosa) in frozen and non-frozen states

Treesearch

Shan Gao; Xiping Wang; Lihai Wang

2015-01-01

The response of dynamic and static modulus of elasticity (MOEdyn and MOEsta) of red pine small clear wood (25.4 × 25.4 × 407 mm3) within the temperature range -40 to 40°C has been investigated. The moisture content (MC) of the specimens ranged from 0 to 118%. The MOEdyn was...

Stress wave velocity and dynamic modulus of elasticity of yellow-poplar ranging from 100 to 10 percent moisture content

Treesearch

Jody D. Gray; Shawn T. Grushecky; James P. Armstrong

2008-01-01

Moisture content has a significant impact on mechanical properties of wood. In recent years, stress wave velocity has been used as an in situ and non-destructive method for determining the stiffness of wooden elements. The objective of this study was to determine what effect moisture content has on stress wave velocity and dynamic modulus of elasticity. Results...

In Vivo Estimation of Perineal Body Properties Using Ultrasound Quasistatic Elastography in Nulliparous Women

PubMed Central

Chen, Luyun; Low, Lisa Kane; DeLancey, John OL; Ashton-Miller, James A

2015-01-01

Objective The perineal body must undergo a remarkable transformation during pregnancy to accommodate an estimated stretch ratio of over 3.3 in order to permit vaginal delivery of the fetal head. Yet measurements of perineal body elastic properties are lacking in vivo, whether in the pregnant or non-pregnant state. The objective of this study, therefore, was to develop a method for measuring perineal body elastic modulus and to test its feasibility in young nulliparous women. Methods An UltraSONIX RP500 ultrasound system was equipped with elastography software. Approximately 1 Hz free-hand sinusoidal compression loading of the perineum was used to measure the relative stiffness of the perineal body compared to that of a custom reference standoff pad with a modulus of 36.7 kPa. Measurements were made in 20 healthy nulliparous women. Four subjects were invited back for second and third visits to evaluate within- and between-visit repeatability using the coefficient of variation. Results The mean± SD elastic compression modulus of the perineal body was 28.9 ± 4.7 kPa. Within- and between-visit repeatability averaged 3.4% and 8.3%, respectively. Conclusion Ultrasound elastography using a standoff pad reference provides a valid method for evaluating the elastic modulus of the perineal body in living women. PMID:25801422

Experimental Observation of Two Features Unexpected from the Classical Theories of Rubber Elasticity

NASA Astrophysics Data System (ADS)

Nishi, Kengo; Fujii, Kenta; Chung, Ung-il; Shibayama, Mitsuhiro; Sakai, Takamasa

2017-12-01

Although the elastic modulus of a Gaussian chain network is thought to be successfully described by classical theories of rubber elasticity, such as the affine and phantom models, verification experiments are largely lacking owing to difficulties in precisely controlling of the network structure. We prepared well-defined model polymer networks experimentally, and measured the elastic modulus G for a broad range of polymer concentrations and connectivity probabilities, p . In our experiment, we observed two features that were distinct from those predicted by classical theories. First, we observed the critical behavior G ˜|p -pc|1.95 near the sol-gel transition. This scaling law is different from the prediction of classical theories, but can be explained by analogy between the electric conductivity of resistor networks and the elasticity of polymer networks. Here, pc is the sol-gel transition point. Furthermore, we found that the experimental G -p relations in the region above C* did not follow the affine or phantom theories. Instead, all the G /G0-p curves fell onto a single master curve when G was normalized by the elastic modulus at p =1 , G0. We show that the effective medium approximation for Gaussian chain networks explains this master curve.

Mechanical properties of injection-molded thermoplastic denture base resins.

PubMed

Hamanaka, Ippei; Takahashi, Yutaka; Shimizu, Hiroshi

2011-03-01

To investigate the mechanical properties of injection-molded thermoplastic denture base resins. Four injection-molded thermoplastic resins (two polyamides, one polyethylene terephthalate, one polycarbonate) and, as a control, a conventional heat-polymerized polymethyl methacrylate (PMMA), were used in this study. The flexural strength at the proportional limit (FS-PL), the elastic modulus, and the Charpy impact strength of the denture base resins were measured according to International Organization for Standardization (ISO) 1567 and ISO 1567:1999/Amd 1:2003. The descending order of the FS-PL was: conventional PMMA > polyethylene terephthalate, polycarbonate > two polyamides. The descending order of the elastic moduli was: conventional PMMA > polycarbonate > polyethylene terephthalate > two polyamides. The descending order of the Charpy impact strength was: polyamide (Nylon PACM12) > polycarbonate > polyamide (Nylon 12), polyethylene terephthalate > conventional PMMA. All of the injection-molded thermoplastic resins had significantly lower FS-PL, lower elastic moduli, and higher or similar impact strength compared to the conventional PMMA. The polyamide denture base resins had low FS-PL and low elastic moduli; one of them possessed very high impact strength, and the other had low impact strength. The polyethylene terephthalate denture base resin showed a moderately high FS-PL, moderate elastic modulus, and low impact strength. The polycarbonate denture base resin had a moderately high FS-PL, moderately high elastic modulus, and moderate impact strength.

Ultrahigh Elastic Strain Energy Storage in Metal-Oxide-Infiltrated Patterned Hybrid Polymer Nanocomposites

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

Dusoe, Keith J.; Ye, Xinyi; Kisslinger, Kim

Modulus of resilience, the measure of a material’s capacity to store and release elastic strain energy, is critical for realizing advanced mechanical actuation technologies in micro/nanoelectromechanical systems. In general, engineering the modulus of resilience is difficult because it requires asymmetrically increasing yield strength and Young’s modulus against their mutual scaling behavior. This task becomes further challenging if it needs to be carried out at the nanometer scale. Here, we demonstrate organic–inorganic hybrid composite nanopillars with one of the highest modulus of resilience per density by utilizing vapor-phase aluminum oxide infiltration in lithographically patterned negative photoresist SU-8. In situ nanomechanical measurementsmore » reveal a metal-like high yield strength (~500 MPa) with an unusually low, foam-like Young’s modulus (~7 GPa), a unique pairing that yields ultrahigh modulus of resilience, reaching up to ~24 MJ/m 3 as well as exceptional modulus of resilience per density of ~13.4 kJ/kg, surpassing those of most engineering materials. The hybrid polymer nanocomposite features lightweight, ultrahigh tunable modulus of resilience and versatile nanoscale lithographic patternability with potential for application as nanomechanical components which require ultrahigh mechanical resilience and strength.« less

Ultrahigh Elastic Strain Energy Storage in Metal-Oxide-Infiltrated Patterned Hybrid Polymer Nanocomposites

DOE PAGES

Dusoe, Keith J.; Ye, Xinyi; Kisslinger, Kim; ...

2017-10-19

Modulus of resilience, the measure of a material’s capacity to store and release elastic strain energy, is critical for realizing advanced mechanical actuation technologies in micro/nanoelectromechanical systems. In general, engineering the modulus of resilience is difficult because it requires asymmetrically increasing yield strength and Young’s modulus against their mutual scaling behavior. This task becomes further challenging if it needs to be carried out at the nanometer scale. Here, we demonstrate organic–inorganic hybrid composite nanopillars with one of the highest modulus of resilience per density by utilizing vapor-phase aluminum oxide infiltration in lithographically patterned negative photoresist SU-8. In situ nanomechanical measurementsmore » reveal a metal-like high yield strength (~500 MPa) with an unusually low, foam-like Young’s modulus (~7 GPa), a unique pairing that yields ultrahigh modulus of resilience, reaching up to ~24 MJ/m 3 as well as exceptional modulus of resilience per density of ~13.4 kJ/kg, surpassing those of most engineering materials. The hybrid polymer nanocomposite features lightweight, ultrahigh tunable modulus of resilience and versatile nanoscale lithographic patternability with potential for application as nanomechanical components which require ultrahigh mechanical resilience and strength.« less

Effects of temperature distribution and elastic properties of materials on gas-turbine-disk stresses

NASA Technical Reports Server (NTRS)

Holms, Arthur G; Faldetta, Richard D

1947-01-01

Calculations were made to determine the influence of changes in temperature distribution and in elastic material properties on calculated elastic stresses for a typical gas-turbine disk. Severe temperature gradients caused thermal stresses of sufficient magnitude to reduce the operating safety of the disk. Small temperature gradients were found to be desirable because they produced thermal stresses that subtracted from the centrifugal stresses in the region of the rim. The thermal gradients produced a tendency for a severe stress condition to exist near the rim but this stress condition could be shifted away from the region of blade attachment by altering the temperature distribution. The investigation of elastic material properties showed that centrifugal stresses are slightly affected by changes in modulus of elasticity, but that thermal stresses are approximately proportional to modulus of elasticity and to coefficient of thermal expansion.

Elastic properties of suspended black phosphorus nanosheets

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

Wang, Jia-Ying; Li, Yang; Zhen, Liang

2016-01-04

The mechanical properties of black phosphorus (BP) nanosheets suspended over circular holes were measured by an atomic force microscope nanoindentation method. The continuum mechanic model was introduced to calculate the elastic modulus and pretension of BP nanosheets with thicknesses ranging from 14.3 to 34 nm. Elastic modulus of BP nanosheets declines with thickness, and the maximum value is 276 ± 32.4 GPa. Besides, the effective strain of BP ranges from 8 to 17% with a breaking strength of 25 GPa. Our results show that BP nanosheets serve as a promising candidate for flexible electronic applications.

Theoretical Investigations of Si-Ge Alloys in P42/ncm Phase: First-Principles Calculations

PubMed Central

Ma, Zhenyang; Liu, Xuhong; Yu, Xinhai; Shi, Chunlei; Yan, Fang

2017-01-01

The structural, mechanical, anisotropic, electronic and thermal properties of Si, Si0.667Ge0.333, Si0.333Ge0.667 and Ge in P42/ncm phase are investigated in this work. The calculations have been performed with an ultra-soft pseudopotential by using the generalized gradient approximation and local density approximation in the framework of density functional theory. The achieved results for the lattice constants and band gaps of P42/ncm-Si and P42/ncm-Ge in this research have good accordance with other results. The calculated elastic constants and elastic moduli of the Si, Si0.667Ge0.333, Si0.333Ge0.667 and Ge in P42/ncm phase are better than that of the Si, Si0.667Ge0.333, Si0.333Ge0.667 and Ge in P42/mnm phase. The Si, Si0.667Ge0.333, Si0.333Ge0.667 and Ge in P42/ncm phase exhibit varying degrees of mechanical anisotropic properties in Poisson’s ratio, shear modulus, Young’s modulus, and universal anisotropic index. The band structures of the Si, Si0.667Ge0.333, Si0.333Ge0.667 and Ge in P42/ncm phase show that they are all indirect band gap semiconductors with band gap of 1.46 eV, 1.25 eV, 1.36 eV and 1.00 eV, respectively. In addition, we also found that the minimum thermal conductivity κmin of the Si, Si0.667Ge0.333, Si0.333Ge0.667 and Ge in P42/ncm phase exhibit different degrees of anisotropic properties in (001), (010), (100) and (01¯0) planes. PMID:28772964

High-pressure structural, elastic, and electronic properties of the scintillator host material KMgF3

NASA Astrophysics Data System (ADS)

Vaitheeswaran, G.; Kanchana, V.; Kumar, Ravhi S.; Cornelius, A. L.; Nicol, M. F.; Svane, A.; Delin, A.; Johansson, B.

2007-07-01

The high-pressure structural behavior of the fluoroperovskite KMgF3 is investigated by theory and experiment. Density functional calculations were performed within the local density approximation and the generalized gradient approximation for exchange and correlation effects, as implemented within the full-potential linear muffin-tin orbital method. In situ high-pressure powder x-ray diffraction experiments were performed up to a maximum pressure of 40GPa using synchrotron radiation. We find that the cubic Pm3¯m crystal symmetry persists throughout the pressure range studied. The calculated ground state properties—the equilibrium lattice constant, bulk modulus, and elastic constants—are in good agreement with experimental results. By analyzing the ratio between the bulk and shear moduli, we conclude that KMgF3 is brittle in nature. Under ambient conditions, KMgF3 is found to be an indirect gap insulator, with the gap increasing under pressure.

Effect of emulsifier type and concentration, aqueous phase volume and wax ratio on physical, material and mechanical properties of water in oil lipsticks.

PubMed

Beri, A; Norton, J E; Norton, I T

2013-12-01

Water-in-oil emulsions in lipsticks could have the potential to improve moisturizing properties and deliver hydrophilic molecules to the lips. The aims of this work were (i) to investigate the effect of emulsifier type (polymer vs. monomer, and saturated vs. unsaturated chain) and concentration on droplet size and (ii) to investigate the effect of wax ratio (carnauba wax, microcrystalline wax, paraffin wax and performalene) and aqueous phase volume on material properties (Young's modulus, point of fracture, elastic modulus and viscous modulus). Emulsion formation was achieved using a high shear mixer. Results showed that the saturated nature of the emulsifier had very little effect on droplet size, neither did the use of an emulsifier with a larger head group (droplet size ~18-25 μm). Polyglycerol polyricinoleate (PGPR) resulted in emulsions with the smallest droplets (~3-5 μm), as expected from previous studies that show that it produces a thick elastic interface. The results also showed that both Young's modulus and point of fracture increase with increasing percentage of carnauba wax (following a power law dependency of 3), but decrease with increasing percentage of microcrystalline wax, suggesting that the carnauba wax is included in the overall wax network formed by the saturated components, whereas the microcrystalline wax forms irregular crystals that disrupt the overall wax crystal network. Young's modulus, elastic modulus and viscous modulus all decrease with increasing aqueous phase volume in the emulsions, although the slope of the decrease in elastic and viscous moduli is dependent on the addition of solid wax, as a result of strengthening the network. This work suggests the potential use for emulsions in lipstick applications, particularly when PGPR is used as an emulsifier, and with the addition of solid wax, as it increases network strength. © 2013 Society of Cosmetic Scientists and the Société Française de Cosmétologie.

Frequency Analysis of Strain of Cylindrical Shell for Assessment of Viscosity

NASA Astrophysics Data System (ADS)

Hasegawa, Hideyuki; Kanai, Hiroshi

2005-06-01

For tissue characterization of atherosclerotic plaque, we have developed a method, namely, the phased tracking method, [H. Kanai et al.: IEEE Trans. Ultrason. Ferroelectr. Freq. Control 43 (1996) 791] to measure the regional strain (change in wall thickness) and elasticity of the arterial wall. In addition to the regional elasticity, we are attempting to measure the regional viscosity for a more precise tissue characterization. Previously, we showed that the viscosity can be obtained by measuring the frequency dependence of the elastic modulus using remote actuation [H. Hasegawa et al.: Jpn. J. Appl. Phys. 43 (2004) 3197]. However, in this method, we need to apply external actuation to the subject. To simplify the measurement, we instead to obtain the frequency dependence of the elastic modulus from the change in arterial wall thickness spontaneously caused by the heartbeat because this change in thickness consists of frequency components up to 20-30 Hz. In this paper, the frequency dependence of the elastic modulus of a silicone rubber tube was investigated by applying frequency analysis to the change in wall thickness caused by the change in internal pressure simulating the actual arterial blood pressure.

Infrared spectroscopy, nano-mechanical properties, and scratch resistance of esthetic orthodontic coated archwires.

PubMed

da Silva, Dayanne Lopes; Santos, Emanuel; Camargo, Sérgio de Souza; Ruellas, Antônio Carlos de Oliveira

2015-09-01

To evaluate the material composition, mechanical properties (hardness and elastic modulus), and scratch resistance of the coating of four commercialized esthetic orthodontic archwires. The coating composition of esthetic archwires was assessed by Fourier-transform infrared spectroscopy (FTIR). Coating hardness and elastic modulus were analyzed with instrumented nano-indentation tests. Scratch resistance of coatings was evaluated by scratch test. Coating micromorphologic characteristics after scratch tests were observed in a scanning electron microscope. Statistical differences were investigated using analysis of variance and Tukey post hoc test. The FTIR results indicate that all analyzed coatings were markedly characterized by the benzene peak at about 1500 cm(-1). The coating hardness and elastic modulus average values ranged from 0.17 to 0.23 GPa and from 5.0 to 7.6 GPa, respectively. Scratch test showed a high coating elasticity after load removal with elastic recoveries >60%, but different failure features could be observed along the scratches. The coatings of esthetic archwires evaluated are probably a composite of polyester and polytetrafluoroethylene. Delamination, crack propagation, and debris generation could be observed along the coating scratches and could influence its durability in the oral environment.

A first principle calculation of anisotropic elastic, mechanical and electronic properties of TiB

NASA Astrophysics Data System (ADS)

Zhang, Junqin; Zhao, Bin; Ma, Huihui; Wei, Qun; Yang, Yintang

2018-04-01

The structural, mechanical and electronic properties of the NaCl-type structure TiB are theoretically calculated based on the first principles. The density of states of TiB shows obvious density peaks at -0.70eV. Furthermore, there exists a pseudogap at 0.71eV to the right of the Fermi level. The calculated structural and mechanical parameters (i.e., bulk modulus, shear modulus, Young's modulus, Poisson's ratio and universal elastic anisotropy index) were in good agreement both with the previously reported experimental values and theoretical results at zero pressure. The mechanical stability criterion proves that TiB at zero pressure is mechanistically stable and exhibits ductility. The universal anisotropic index and the 3D graphics of Young's modulus are also given in this paper, which indicates that TiB is anisotropy under zero pressure. Moreover, the effects of applied pressures on the structural, mechanical and anisotropic elastic of TiB were studied in the range from 0 to 100GPa. It was found that ductility and anisotropy of TiB were enhanced with the increase of pressure.

Investigation of the structural, electronic, elastic and thermodynamic properties of Curium Monopnictides: An ab initio study

NASA Astrophysics Data System (ADS)

Baaziz, H.; Guendouz, Dj.; Charifi, Z.; Akbudak, S.; Uğur, G.; Uğur, Ş.; Boudiaf, K.

2017-12-01

The structural, electronic, elastic and thermodynamic properties of Curium Monopnictides CmX (X = N, P, As, Sb and Bi) are investigated using first-principles calculations based on the density functional theory (DFT) and full potential linearized augmented plane wave (FP-LAPW) method under ambient condition and high pressure. The exchange-correlation term is treated using two approximations spin-polarized local density approximation (LSDA) and spin-polarized generalized gradient approximation generalized (GGA). The structural parameters such as the equilibrium lattice parameters, bulk modulus and the total energies are calculated in two phases: namely NaCl (B1) and CsCl (B2). The obtained results are compared with the previous theoretical and experimental results. A structural phase transition from B1 phase to B2 phase for Curium pnictides has been obtained. The highest transition pressure is 122 GPa for CmN and the lowest one is 10.0 GPa for CmBi compound. The electronic properties show that these materials exhibit half-metallic behavior in both phases. The magnetic moment is found to be around 7.0 μB. The mechanical properties of CmX (X = N, P, As, Sb and Bi) are predicted from the calculated elastic constants. Our calculated results are in good agreement with the theoretical results in literature. The effect of pressure and temperature on the thermodynamic properties like the cell volume, bulk modulus and the specific heats C𝜗 and CP, the entropy 𝒮 and the Grüneisen parameter γ have been foreseen at expanded pressure and temperature ranges.

Contact mechanics for coated spheres that includes the transition from weak to strong adhesion

DOE PAGES

Reedy, Earl David

2007-09-01

Recently published results for a rigid spherical indenter contacting a thin, linear elastic coating on a rigid planar substrate have been extended to include the case of two contacting spheres, where each sphere is rigid and coated with a thin, linear elastic material. This is done by using an appropriately chosen effective radius and coating modulus. Finally, the earlier work has also been extended to provide analytical results that span the transition between the previously derived Derjaguin–Müller–Toporov (DMT)-like (work of adhesion/coating-modulus ratio is small) and Johnson–Kendall–Roberts (JKR)-like (work of adhesion/coating-modulus ratio is large) limits.

A first-principles investigation on the effects of magnetism on the Bain transformation of α-phase FeNi systems

NASA Astrophysics Data System (ADS)

Rahman, Gul; Gee Kim, In; Bhadeshia, H. K. D. H.

2012-03-01

The effects of magnetism on the Bain transformation of α-phase FeNi systems are investigated by using the full potential linearized augmented plane wave method based on the generalized gradient approximation. We found that Ni impurity in bcc Fe increases the lattice constant in the ferromagnetic (FM) states, but not in the nonmagnetic (NM) states. The shear modulus, G, and Young's modulus, E, of bcc Fe are also increased by raising the concentration of nickel. All the compositions considered show high shear anisotropy, and the ratio of the bulk to shear modulus is greater than 1.75, implying ductility. The mean sound velocities in the [100] directions are greater than in the [110] directions. The Bain transformation, which is a component of martensitic transformation, has also been studied to reveal that NixFe1-x alloys are elastically unstable in the NM states, but not so in the FM states. The electronic structures explain these results in terms of the density of states at the Fermi level. It is evident that magnetism cannot be neglected when dealing with the Bain transformation in iron and its alloys.

Mechanical properties and phase stability of monoborides using density functional theory calculations

NASA Astrophysics Data System (ADS)

Kim, Hyojung; Trinkle, Dallas R.

2017-06-01

We compute the structural energies, elastic constants, and stacking fault energies, and investigate the phase stability of monoborides with different compositions (" close=")X1-x 1Xx2)">X1-x 1Xx2B (X =Ti/Fe/Mo/Nb/V ) using density functional theory in order to search for Ti monoborides with improved mechanical properties. Our computed Young's modulus and Pugh's modulus ratio, which correlate with stiffness and toughness, agree well with predictions from Vegard's law with the exceptions of mixed monoborides containing Mo and Fe. Among all the monoborides considered in this paper, TiB has the smallest Pugh's ratio, which suggests that the addition of solutes can improve the toughness of a Ti matrix. When X1B and X2B are respectively most stable in the B27 and Bf structures, the mixed monoborides (X0.51X0.52)B , mixed (Ti0.5Mo0.5 )B and mixed (Ti0.5V0.5 )B have a higher Young's modulus, a higher Pugh's ratio, and a smaller stacking fault energy than TiB. We also construct phase diagrams and find large solubility limits for solid solutions containing Ti compared to those containing Fe.

Electronic and mechanic properties of trigonal boron nitride by first-principles calculations

NASA Astrophysics Data System (ADS)

Mei, Hua Yue; Pang, Yong; Liu, Ding Yu; Cheng, Nanpu; Zheng, Shaohui; Song, Qunliang; Wang, Min

2018-07-01

A new boron nitride allotrope with 6 atoms in a unit cell termed as trigonal BN (TBN), which belongs to P3121 space group, is theoretically investigated. Electronic structures, mechanic properties, phonon spectra and other properties were calculated by using first-principles based on density functional theory (DFT). The elastic constants reveal that TBN is mechanically stable. Furthermore, phonon dispersion indicates that TBN is dynamically stable. The calculated bulk modulus and shear modulus of TBN are 323 and 342 GPa, respectively. The calculated Young's modulus are Ex = Ey = 760 GPa, Ez = 959 GPa, indicating that TBN is a super-hard and brittle material. The universal anisotropy index, which is only 0.296, shows its weak anisotropy. Band structure states clearly that TBN is an indirect semiconductor with a band gap of 3.87 eV. The valence bands are mainly composed of N 2p states, and the conduction bands are mainly contributed by B 2p states. Simulated X-ray diffraction patterns (XRD) and Raman spectra were also provided for future experimental characterizations. Due to its band gap and super-hard properties, TBN may possess potential in super-hard, optical and electronic applications.

Noninvasive Vascular Displacement Estimation for Relative Elastic Modulus Reconstruction in Transversal Imaging Planes

PubMed Central

Hansen, Hendrik H.G.; Richards, Michael S.; Doyley, Marvin M.; de Korte, Chris L.

2013-01-01

Atherosclerotic plaque rupture can initiate stroke or myocardial infarction. Lipid-rich plaques with thin fibrous caps have a higher risk to rupture than fibrotic plaques. Elastic moduli differ for lipid-rich and fibrous tissue and can be reconstructed using tissue displacements estimated from intravascular ultrasound radiofrequency (RF) data acquisitions. This study investigated if modulus reconstruction is possible for noninvasive RF acquisitions of vessels in transverse imaging planes using an iterative 2D cross-correlation based displacement estimation algorithm. Furthermore, since it is known that displacements can be improved by compounding of displacements estimated at various beam steering angles, we compared the performance of the modulus reconstruction with and without compounding. For the comparison, simulated and experimental RF data were generated of various vessel-mimicking phantoms. Reconstruction errors were less than 10%, which seems adequate for distinguishing lipid-rich from fibrous tissue. Compounding outperformed single-angle reconstruction: the interquartile range of the reconstructed moduli for the various homogeneous phantom layers was approximately two times smaller. Additionally, the estimated lateral displacements were a factor of 2–3 better matched to the displacements corresponding to the reconstructed modulus distribution. Thus, noninvasive elastic modulus reconstruction is possible for transverse vessel cross sections using this cross-correlation method and is more accurate with compounding. PMID:23478602

The influence of architecture on the elasticity and strength of Si(3)N(4)/BN fibrous-monolithic ceramic laminates

NASA Astrophysics Data System (ADS)

King, Bruce H.

Fibrous-monolithic ceramics are a class of material with many similarities to layered ceramic composites. Like layered composites, fibrous monoliths depend on a weak interphase to promote crack deflection and energy absorption, avoiding catastrophic failure. However, in a fibrous monolith, the interphase surrounds fiber-like "cells" of the strong phase, forming a continuous, 2-dimensional honeycomb network. In the most simple architecture, all cells are aligned unidirectionally. More complex architectures are easily produced by varying the orientation of successive layers relative to each other. The Young's modulus of the unidirectional architecture is predicted accurately along principal axes using a "brick" model, while the modulus at angles between 0sp° and 90sp° is predicted using laminate theory. Laminate theory may also be used to accurately predict the Young's modulus of multidirectional architectures such as a cross-ply 0sp°/90sp° and a quasi-isotropic 0sp°/{±}45sp°/90sp°. Unidirectional fibrous monolithic ceramics are linear elastic in flexure until the first major failure event. The flexural strength of the unidirectional architecture tested at orientations between 0sp° and 90sp° is observed to fall into three distinct regions. Between 0sp° and 10sp° the strength is a constant 450 MPa, but between 10sp° and 45sp°, it gradually drops to 80 MPa. Above 45sp° the strength remains essentially constant. Between 0sp° and 30sp°, the strength is accurately predicted using the Maximum Stress theory. Above 30sp°, the strength is predicted using the Tsai-Hill model. The multidirectional architectures exhibit nonlinearity in flexural loading prior to the peak stress. Cyclic loading experiments indicate that this nonlinearity is a result-of microcracking in the boron nitride cell boundaries of the off-axis layers. The cross-ply architecture exhibits a strength of 334 ± 35 MPa, while the quasi-isotropic has a strength of 255 ± 22 MPa. The models developed to describe the unidirectional architecture may be extended to predict upper and lower bounds on the strength of multidirectional architectures.

Assessing the impact of wood decay fungi on the modulus of elasticity of slash pine (Pinus elliottii) by stress wave non-destructive testing

Treesearch

Zhong Yang; Zhehui Jiang; Chung Y. Hse; Ru Liu

2017-01-01

Small wood specimens selected from six slash pine (Pinus elliottii) trees were inoculated with brown-rot and white-rot fungi and then evaluated for static modulus of elasticity (MOE) and dynamic MOE (MOEsw). The experimental variables studied included a brown-rot fungus (Gloeophyllum trabeum) and a white-rot fungus (Trametes versicolor) for six exposure periods (2, 4,...

Stress Wave Interactions with Tunnels Buried in Well-Characterized Jointed Media.

DTIC Science & Technology

1980-06-01

27 14 Particle Velocity and Principal Stress Fields at 62 jisec for the Elastic- Plastic Media Model (Case 1, 0.8 kbar...is used; the basic formulation is similar to the HEMP code (Ref. 3) . Tn numerical solutions and material properties are luscriben in Section 3. 3...media is 16A rock simulant. The elastic- plastic properties are modeled with the following parameters: Bulk Modulus K = .131 Mbar Shear Modulus G

Dynamic determination of modulus of elasticity of full-size wood composite panels using a vibration method

Treesearch

Cheng Guan; Houjiang Zhang; Lujing Zhou; Xiping Wang

2015-01-01

A vibration testing method based on free vibration theory in a ‘‘free–free” support condition was investigated for evaluating the modulus of elasticity (MOE) of full-size wood composite panels (WCPs). Vibration experiments were conducted on three types of WCPs (medium density fibreboard, particleboard, and plywood) to determine the dynamic MOE of the panels. Static...

Determination of mechanical properties of polymer film materials

NASA Technical Reports Server (NTRS)

Hughes, E. J.; Rutherford, J. L.

1975-01-01

Five polymeric film materials, Tedlar, Teflon, Kapton H, Kapton F, and a fiberglass reinforced polyimide, PG-402, in thickness ranging from 0.002 to 0.005 inch, were tested over a temperature range of -195 to 200 C in the "machine" and transverse direction to determine: elastic modulus, Poisson's ratio, three percent offset yield stress, fracture stress, and strain to fracture. The elastic modulus, yield stress and fracture stress decreased with increasing temperature for all the materials while the fracture strain increased. Teflon and Tedlar had the greatest temperature dependence and PG-402 the least. At 200 C the Poisson ratio values ranged from 0.39 to 0.5; they diminished as the temperature decreased covering a range of 0.26 to 0.42 at -195 C. Shortening the gauge length from eight inches to one inch increased the strain to fracture and lowered the elastic modulus values.

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

Berdova, Maria; Liu, Xuwen; Franssila, Sami, E-mail: sami.franssila@aalto.fi

The investigation of mechanical properties of atomic layer deposition HfO{sub 2} films is important for implementing these layers in microdevices. The mechanical properties of films change as a function of composition and structure, which accordingly vary with deposition temperature and post-annealing. This work describes elastic modulus, hardness, and wear resistance of as-grown and annealed HfO{sub 2}. From nanoindentation measurements, the elastic modulus and hardness remained relatively stable in the range of 163–165 GPa and 8.3–9.7 GPa as a function of deposition temperature. The annealing of HfO{sub 2} caused significant increase in hardness up to 14.4 GPa due to film crystallization and densification. Themore » structural change also caused increase in the elastic modulus up to 197 GPa. Wear resistance did not change as a function of deposition temperature, but improved upon annealing.« less

Elastic Properties of Pore-Spanning Apical Cell Membranes Derived from MDCK II Cells.

PubMed

Nehls, Stefan; Janshoff, Andreas

2017-10-17

The mechanical response of adherent, polarized cells to indentation is frequently attributed to the presence of an endogenous actin cortex attached to the inner leaflet of the plasma membrane. Here, we scrutinized the elastic properties of apical membranes separated from living cells and attached to a porous mesh in the absence of intracellular factors originating from the cytosol, organelles, the substrate, neighbors, and the nucleus. We found that a tension-based model describes the data very well providing essentially the prestress of the shell generated by adhesion of the apical membrane patches to the pore rim and the apparent area compressibility modulus, an intrinsic elastic modulus modulated by the surface excess stored in membrane reservoirs. Removal of membrane-associated proteins by proteases decreases the area compressibility modulus, whereas fixation and cross-linking of proteins with glutaraldehyde increases it. Copyright © 2017 Biophysical Society. Published by Elsevier Inc. All rights reserved.

Anisotropy of demineralized bone matrix under compressive load.

PubMed

Trębacz, Hanna; Zdunek, Artur

2011-01-01

Two groups of cubic specimens from diaphysis of bovine femur, intact and completely demineralized, were axially compressed. One half of the samples from each group were loaded along the axis of the femur (L) and the other - perpendicularly (T). Intact samples were characterized in terms of elastic modulus; for demineralized samples secant modulus of elasticity was calculated. During compression an acoustic emission (AE) signal was recorded and AE events and energy were analyzed. Samples of intact bone did not reveal any anisotropy under compression at the stress of 80 MPa. However, AE signal indicated an initiation of failure in samples loaded in T direction. Demineralized samples were anisotropic under compression. Both secant modulus of elasticity and AE parameters were significantly higher in T direction than in L direction, which is attributed to shifting and separation of lamellae of collagen fibrils and lamellae in bone matrix.

Elastic moduli of a Brownian colloidal glass former

NASA Astrophysics Data System (ADS)

Fritschi, S.; Fuchs, M.

2018-01-01

The static, dynamic and flow-dependent shear moduli of a binary mixture of Brownian hard disks are studied by an event-driven molecular dynamics simulation. Thereby, the emergence of rigidity close to the glass transition encoded in the static shear modulus G_∞ is accessed by three methods. Results from shear stress auto-correlation functions, elastic dispersion relations, and the elastic response to strain deformations upon the start-up of shear flow are compared. This enables one to sample the time-dependent shear modulus G(t) consistently over several decades in time. By that a very precise specification of the glass transition point and of G_∞ is feasible. Predictions by mode coupling theory of a finite shear modulus at the glass transition, of α-scaling in fluid states close to the transition, and of shear induced decay in yielding glass states are tested and broadly verified.

Multi-modality gellan gum-based tissue-mimicking phantom with targeted mechanical, electrical, and thermal properties.

PubMed

Chen, Roland K; Shih, A J

2013-08-21

This study develops a new class of gellan gum-based tissue-mimicking phantom material and a model to predict and control the elastic modulus, thermal conductivity, and electrical conductivity by adjusting the mass fractions of gellan gum, propylene glycol, and sodium chloride, respectively. One of the advantages of gellan gum is its gelling efficiency allowing highly regulable mechanical properties (elastic modulus, toughness, etc). An experiment was performed on 16 gellan gum-based tissue-mimicking phantoms and a regression model was fit to quantitatively predict three material properties (elastic modulus, thermal conductivity, and electrical conductivity) based on the phantom material's composition. Based on these material properties and the regression model developed, tissue-mimicking phantoms of porcine spinal cord and liver were formulated. These gellan gum tissue-mimicking phantoms have the mechanical, thermal, and electrical properties approximately equivalent to those of the spinal cord and the liver.

Mechanical Sensing with Flexible Metallic Nanowires

NASA Astrophysics Data System (ADS)

Dobrokhotov, Vladimir; Yazdanpanah, Mehdi; Pabba, Santosh; Safir, Abdelilah; Cohn, Robert

2008-03-01

A calibrated method of force sensing is demonstrated in which the buckled shape of a long flexible metallic nanowire is interpreted to determine the applied force. Using a nanomanipulator the nanowire is buckled in the chamber of a scanning electron microscope (SEM) and the buckled shapes are recorded in SEM images. Force is determined as a function of deflection for an assumed elastic modulus by fitting the shapes using the generalized elastica model. In this calibration the elastic modulus was determined using an auxiliary AFM measurement, with the needle in the same orientation as in the SEM. Following this calibration the needle was used as a sensor in a different orientation than the AFM coordinates to deflect a suspended PLLA polymer fiber from which the elastic modulus (2.96 GPa) was determined. In this study the same needle remained rigidly secured to the AFM cantilever throughout the entire SEM/AFM calibration procedure and the characterization of the nanofiber.

Effect of Curing Period on Properties of Steel and Polypropylene Fibre Reinforced Ultra-High Performance Concrete

NASA Astrophysics Data System (ADS)

Smarzewski, Piotr

2017-10-01

This study has investigated the effect of curing period on the mechanical properties of straight polypropylene and hooked-end steel fibre reinforced ultra-high performance concrete (UHPC). Various physical properties are evaluated, i.e. absorbability, apparent density and open porosity. Compressive strength, tensile splitting strength, flexural strength and modulus of elasticity were determined at 28, 56 and 730 days. Comparative strength development of fibre reinforced mixes at 0.5%, 1%, 1.5% and 2% by volume fractions in relation to the mix without fibres was observed. Good correlations between the compressive strength and the modulus of elasticity are established. Steel and polypropylene fibres significantly increased the compressive strength, tensile splitting strength, flexural strength and modulus of elasticity of UHPC after two years curing period when fibre content volume was at least 1%. It seems that steel fibre reinforced UHPC has better properties than the polypropylene fibre reinforced UHPC.

Effects of process variables on the encapsulation of oil in ca-alginate capsules using an inverse gelation technique.

PubMed

Abang, Sariah; Chan, Eng-Seng; Poncelet, Denis

2012-01-01

The objective of this study was to investigate the effects of process variables on the encapsulation of oil in a calcium alginate membrane using an inverse gelation technique. A dispersion of calcium chloride solution in sunflower oil (water-in-oil emulsion) was added dropwise to the alginate solution. The migration of calcium ions to the alginate solution initiates the formation of a ca-alginate membrane around the emulsion droplets. The membrane thickness of wet capsules and the elastic modulus of dry capsules increased following first-order kinetics with an increasing curing time. An increase in the calcium chloride concentration increased the membrane thickness of wet capsules and the elastic modulus of dry capsules. An increase in the alginate concentration decreased the mean diameter of wet capsules but increased the elastic modulus of dry capsules.

Solvent-free, supersoft and superelastic bottlebrush melts and networks

NASA Astrophysics Data System (ADS)

Daniel, William F. M.; Burdyńska, Joanna; Vatankhah-Varnoosfaderani, Mohammad; Matyjaszewski, Krzysztof; Paturej, Jarosław; Rubinstein, Michael; Dobrynin, Andrey V.; Sheiko, Sergei S.

2016-02-01

Polymer gels are the only viable class of synthetic materials with a Young's modulus below 100 kPa conforming to biological applications, yet those gel properties require a solvent fraction. The presence of a solvent can lead to phase separation, evaporation and leakage on deformation, diminishing gel elasticity and eliciting inflammatory responses in any surrounding tissues. Here, we report solvent-free, supersoft and superelastic polymer melts and networks prepared from bottlebrush macromolecules. The brush-like architecture expands the diameter of the polymer chains, diluting their entanglements without markedly increasing stiffness. This adjustable interplay between chain diameter and stiffness makes it possible to tailor the network's elastic modulus and extensibility without the complications associated with a swollen gel. The bottlebrush melts and elastomers exhibit an unprecedented combination of low modulus (~100 Pa), high strain at break (~1,000%), and extraordinary elasticity, properties that are on par with those of designer gels.

Nonlinear effects in thermal stress analysis of a solid propellant rocket motor

NASA Technical Reports Server (NTRS)

Francis, E. C.; Peeters, R. L.; Murch, S. A.

1976-01-01

Direct characterization procedures were used to determine the relaxation modulus as a function of time, temperature, and state of strain. Using the quasi-elastic method of linearviscoelasticity, these properties were employed in a finite element computer code to analyze a thick-walled, nonlinear viscoelastic cylinder in the state of plane strain bonded to a thin (but stiff) elastic casing and subjected to slow thermal cooling. The viscoelastic solution is then expressed as a sequence of elastic finite element solutions. The strain-dependent character of the relaxation modulus is included by replacing the single relaxation curve used in the linear viscoelastic theory by a family of relaxation functions obtained at various strain levels. These functions may be regarded as a collection of stress histories or responses to specific loads (in this case, step strains) with which the cooldown solution is made to agree by iterations on the modulus and strain level.

Theoretical requirements for broadband perfect absorption of acoustic waves by ultra-thin elastic meta-films

PubMed Central

Duan, Yuetao; Luo, Jie; Wang, Guanghao; Hang, Zhi Hong; Hou, Bo; Li, Jensen; Sheng, Ping; Lai, Yun

2015-01-01

We derive and numerically demonstrate that perfect absorption of elastic waves can be achieved in two types of ultra-thin elastic meta-films: one requires a large value of almost pure imaginary effective mass density and a free space boundary, while the other requires a small value of almost pure imaginary effective modulus and a hard wall boundary. When the pure imaginary density or modulus exhibits certain frequency dispersions, the perfect absorption effect becomes broadband, even in the low frequency regime. Through a model analysis, we find that such almost pure imaginary effective mass density with required dispersion for perfect absorption can be achieved by elastic metamaterials with large damping. Our work provides a feasible approach to realize broadband perfect absorption of elastic waves in ultra-thin films. PMID:26184117

Propagating elastic vibrations dominate thermal conduction in amorphous silicon

NASA Astrophysics Data System (ADS)

Moon, Jaeyun; Latour, Benoit; Minnich, Austin J.

2018-01-01

The thermal atomic vibrations of amorphous solids can be distinguished by whether they propagate as elastic waves or do not propagate due to lack of atomic periodicity. In a -Si, prior works concluded that nonpropagating waves are the dominant contributors to heat transport, with propagating waves being restricted to frequencies less than a few THz and scattered by anharmonicity. Here, we present a lattice and molecular dynamics analysis of vibrations in a -Si that supports a qualitatively different picture in which propagating elastic waves dominate the thermal conduction and are scattered by local fluctuations of elastic modulus rather than anharmonicity. We explicitly demonstrate the propagating nature of waves up to around 10 THz, and further show that pseudoperiodic structures with homogeneous elastic properties exhibit a marked temperature dependence characteristic of anharmonic interactions. Our work suggests that most heat is carried by propagating elastic waves in a -Si and demonstrates that manipulating local elastic modulus variations is a promising route to realize amorphous materials with extreme thermal properties.

Investigation into local cell mechanics by atomic force microscopy mapping and optical tweezer vertical indentation

NASA Astrophysics Data System (ADS)

Coceano, G.; Yousafzai, M. S.; Ma, W.; Ndoye, F.; Venturelli, L.; Hussain, I.; Bonin, S.; Niemela, J.; Scoles, G.; Cojoc, D.; Ferrari, E.

2016-02-01

Investigating the mechanical properties of cells could reveal a potential source of label-free markers of cancer progression, based on measurable viscoelastic parameters. The Young’s modulus has proved to be the most thoroughly studied so far, however, even for the same cell type, the elastic modulus reported in different studies spans a wide range of values, mainly due to the application of different experimental conditions. This complicates the reliable use of elasticity for the mechanical phenotyping of cells. Here we combine two complementary techniques, atomic force microscopy (AFM) and optical tweezer microscopy (OTM), providing a comprehensive mechanical comparison of three human breast cell lines: normal myoepithelial (HBL-100), luminal breast cancer (MCF-7) and basal breast cancer (MDA-MB-231) cells. The elastic modulus was measured locally by AFM and OTM on single cells, using similar indentation approaches but different measurement parameters. Peak force tapping AFM was employed at nanonewton forces and high loading rates to draw a viscoelastic map of each cell and the results indicated that the region on top of the nucleus provided the most meaningful results. OTM was employed at those locations at piconewton forces and low loading rates, to measure the elastic modulus in a real elastic regime and rule out the contribution of viscous forces typical of AFM. When measured by either AFM or OTM, the cell lines’ elasticity trend was similar for the aggressive MDA-MB-231 cells, which were found to be significantly softer than the other two cell types in both measurements. However, when comparing HBL-100 and MCF-7 cells, we found significant differences only when using OTM.

Influence of elastic parameters on the evolution of elasticity modulus of thin films

NASA Astrophysics Data System (ADS)

Gacem, A.; Doghmane, A.; Hadjoub, Z.; Beldi, I.; Doghmane, M.

2012-09-01

In recent years, it appears many structures in the form of thin films or multilayers, used as coatings for surface protection, or to provide materials with new properties different from those of substrates. These properties are the subject of a growing number of studies in order to produce Nano or micro structures with different degrees of quality, and cost as well as the manufacture of thin film properties more functional and more controllable. As the thicknesses are close to micrometric or nanometric scales, the modulus of elasticity are difficult to measure and experimental results are rarely published in the literature. In this context, we propose an analytical qualitative methodology to describe the influence of acoustic parameters of thin films on the evolution of elastic moduli the most used. This method is based on the determination of the acoustic signature V(z) of several thin layers deposited on different substrates, as well the information on the propagation velocity of ultrasonic waves are obtained. Thus, the dispersion curves representing the variation of the modulus of elasticity (Young and the shear), were determined. We have noticed that, according to the type of substrate (light, medium or heavy), we observed the appearance of some anomalies in curves that are generally associated with changes in the acoustic properties of each of the examined layers. We have shown that these anomalies are mainly due to the effect loading, and represent one of the fundamental parameters determining the appearance or disappearance of a phenomenon and represent one of the basic parameters determining the appearance or disappearance of phenomena. Finally, we determine the Poisson ratio of thin films in order to calculate other elastic parameters such as the compressor modulus.

Electronic structure, mechanical and thermodynamic properties of BaPaO3 under pressure.

PubMed

Khandy, Shakeel Ahmad; Islam, Ishtihadah; Gupta, Dinesh C; Laref, Amel

2018-05-07

Density functional theory (DFT)-based investigations have been put forward on the elastic, mechanical, and thermo-dynamical properties of BaPaO 3 . The pressure dependence of electronic band structure and other physical properties has been carefully analyzed. The increase in Bulk modulus and decrease in lattice constant is seen on going from 0 to 30 GPa. The predicted lattice constants describe this material as anisotropic and ductile in nature at ambient conditions. Post-DFT calculations using quasi-harmonic Debye model are employed to envisage the pressure-dependent thermodynamic properties like Debye temperature, specific heat capacity, Grüneisen parameter, thermal expansion, etc. Also, the computed Debye temperature and melting temperature of BaPaO 3 at 0 K are 523 K and 1764.75 K, respectively.

Electronic and optical properties of RESn{sub 3} (RE=Pr & Nd) intermetallics: A first principles study

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

Pagare, G., E-mail: gita-pagare@yahoo.co.in; Abraham, Jisha A.; Department of Physics, National Defence Academy, Pune-411023

2015-06-24

A theoretical study of structural, electronic and optical properties of RESn{sub 3} (RE = Pr & Nd) intermetallics have been investigated systematically using first principles density functional theory. The calculations are carried out within the PBE-GGA and LSDA for the exchange correlation potential. The ground state properties such as lattice parameter (a{sub 0}), bulk modulus (B) and its pressure derivative (B′) are calculated and the calculated lattice parameters show well agreement with the experimental results. We first time predict elastic constants for these compounds. From energy dispersion curves, it is found that these compounds are metallic in nature. The linearmore » optical response of these compounds are also studied and the higher value of static dielectric constant shows the possibility to use them as good dielectric materials.« less

Temperature effect of elastic anisotropy and internal strain development in advanced nanostructured alloys: An in-situ synchrotron X-ray investigation

DOE PAGES

Gan, Yingye; Mo, Kun; Yun, Di; ...

2017-03-19

Nanostructured ferritic alloys (NFAs) are promising structural materials for advanced nuclear systems due to their exceptional radiation tolerance and high-temperature mechanical properties. Their remarkable properties result from the ultrafine ultrahigh density Y-Ti-O nanoclusters dispersed within the ferritic matrix. In this work, we performed in-situ synchrotron X-ray diffraction tests to study the tensile deformation process of the three types of NFAs: 9YWTV, 14YWT-sm13, and 14YWT-sm170 at both room temperature and elevated temperatures. A technique was developed, combining Kroner's model and X-ray measurement, to determine the intrinsic monocrystal elastic-stiffness constants, and polycrystal Young's modulus and Poisson's ratio of the NFAs. Temperature dependencemore » of elastic anisotropy was observed in the NFAs. Lastly, an analysis of intergranular strain and strengthening factors determined that 14YWT-sm13 had a higher resistance to temperature softening compared to 9YWTV, attributed to the more effective nanoparticle strengthening during high-temperature mechanical loading.« less

An analytical model of the mechanical properties of bulk coal under confined stress

USGS Publications Warehouse

Wang, G.X.; Wang, Z.T.; Rudolph, V.; Massarotto, P.; Finley, R.J.

2007-01-01

This paper presents the development of an analytical model which can be used to relate the structural parameters of coal to its mechanical properties such as elastic modulus and Poisson's ratio under a confined stress condition. This model is developed primarily to support process modeling of coalbed methane (CBM) or CO2-enhanced CBM (ECBM) recovery from coal seam. It applied an innovative approach by which stresses acting on and strains occurring in coal are successively combined in rectangular coordinates, leading to the aggregated mechanical constants. These mechanical properties represent important information for improving CBM/ECBM simulations and incorporating within these considerations of directional permeability. The model, consisting of constitutive equations which implement a mechanically consistent stress-strains correlation, can be used as a generalized tool to study the mechanical and fluid behaviors of coal composites. An example using the model to predict the stress-strain correlation of coal under triaxial confined stress by accounting for the elastic and brittle (non-elastic) deformations is discussed. The result shows a good agreement between the prediction and the experimental measurement. ?? 2007 Elsevier Ltd. All rights reserved.

Temperature effect of elastic anisotropy and internal strain development in advanced nanostructured alloys: An in-situ synchrotron X-ray investigation

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

Gan, Yingye; Mo, Kun; Yun, Di

2017-04-01

Nanostructured ferritic alloys (NFAs) are a promising structural material for advanced nuclear systems due to their exceptional radiation tolerance and high-temperature mechanical properties. Their remarkable properties result from the ultrafine ultrahigh density Y-Ti-O nanoclusters dispersed within the ferritic matrix. In this work, we performed in-situ synchrotron X-ray diffraction tests to study the tensile deformation process of the three types of NFAs: 9YWTV, 14YWT-sm13, and 14YWT-sm170 at both room temperature and elevated temperatures. A technique was developed, combining Kroner’s model and X-ray measurement, to determine the intrinsic monocrystal elastic-stiffness constants, and polycrystal Young’s modulus and Poisson’s ratio of the NFAs. Temperaturemore » dependence of elastic anisotropy was observed in the NFAs. An analysis of intergranular strain and strengthening factors determined that 14YWT-sm13 had a higher resistance to temperature softening compared to 9YWTV, attributed to the more effective nanoparticle strengthening during high-temperature mechanical loading.« less

Porous and strong bioactive glass (13–93) scaffolds prepared by unidirectional freezing of camphene-based suspensions

PubMed Central

Liu, Xin; Rahaman, Mohamed N.; Fu, Qiang; Tomsia, Antoni P.

2011-01-01

Scaffolds of 13–93 bioactive glass (6Na2O, 12K2O, 5MgO, 20CaO, 4P2O5, 53SiO2; wt %) with an oriented pore architecture were formed by unidirectional freezing of camphene-based suspensions, followed by thermal annealing of the frozen constructs to grow the camphene crystals. After sublimation of the camphene, the constructs were sintered (1 h at 700 °C) to produce a dense glass phase with oriented macropores. The objective of this work was to study how constant freezing rates (1–7 °C/min) during the freezing step influenced the pore orientation and mechanical response of the scaffolds. When compared to scaffolds prepared by freezing the suspensions on a substrate kept at a constant temperature of 3 °C (time-dependent freezing rate), higher freezing rates resulted in better pore orientation, a more homogeneous microstructure, and a marked improvement in the mechanical response of the scaffolds in compression. Scaffolds fabricated using a constant freezing rate of 7 °C/min (porosity = 50 ± 4%; average pore diameter = 100 μm), had a compressive strength of 47 ± 5 MPa and an elastic modulus of 11 ± 3 GPa (in the orientation direction). In comparison, scaffolds prepared by freezing on the constant-temperature substrate had strength and modulus values of 35 ± 11 MPa and 8 ± 3 GPa, respectively. These oriented bioactive glass scaffolds prepared by the constant freezing rate route could potentially be used for the repair of defects in load-bearing bones, such as segmental defects in the long bones. PMID:21855661

Rubber elasticity for percolation network consisting of Gaussian chains.

PubMed

Nishi, Kengo; Noguchi, Hiroshi; Sakai, Takamasa; Shibayama, Mitsuhiro

2015-11-14

A theory describing the elastic modulus for percolation networks of Gaussian chains on general lattices such as square and cubic lattices is proposed and its validity is examined with simulation and mechanical experiments on well-defined polymer networks. The theory was developed by generalizing the effective medium approximation (EMA) for Hookian spring network to Gaussian chain networks. From EMA theory, we found that the ratio of the elastic modulus at p, G to that at p = 1, G0, must be equal to G/G0 = (p - 2/f)/(1 - 2/f) if the position of sites can be determined so as to meet the force balance, where p is the degree of cross-linking reaction. However, the EMA prediction cannot be applicable near its percolation threshold because EMA is a mean field theory. Thus, we combine real-space renormalization and EMA and propose a theory called real-space renormalized EMA, i.e., REMA. The elastic modulus predicted by REMA is in excellent agreement with the results of simulations and experiments of near-ideal diamond lattice gels.

Rubber elasticity for percolation network consisting of Gaussian chains

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

Nishi, Kengo, E-mail: kengo.nishi@phys.uni-goettingen.de, E-mail: sakai@tetrapod.t.u-tokyo.ac.jp, E-mail: sibayama@issp.u-tokyo.ac.jp; Noguchi, Hiroshi; Shibayama, Mitsuhiro, E-mail: kengo.nishi@phys.uni-goettingen.de, E-mail: sakai@tetrapod.t.u-tokyo.ac.jp, E-mail: sibayama@issp.u-tokyo.ac.jp

2015-11-14

A theory describing the elastic modulus for percolation networks of Gaussian chains on general lattices such as square and cubic lattices is proposed and its validity is examined with simulation and mechanical experiments on well-defined polymer networks. The theory was developed by generalizing the effective medium approximation (EMA) for Hookian spring network to Gaussian chain networks. From EMA theory, we found that the ratio of the elastic modulus at p, G to that at p = 1, G{sub 0}, must be equal to G/G{sub 0} = (p − 2/f)/(1 − 2/f) if the position of sites can be determined somore » as to meet the force balance, where p is the degree of cross-linking reaction. However, the EMA prediction cannot be applicable near its percolation threshold because EMA is a mean field theory. Thus, we combine real-space renormalization and EMA and propose a theory called real-space renormalized EMA, i.e., REMA. The elastic modulus predicted by REMA is in excellent agreement with the results of simulations and experiments of near-ideal diamond lattice gels.« less

The effects of fractional CO2 laser, Nano-hydroxyapatite and MI paste on mechanical properties of bovine enamel after bleaching

PubMed Central

Moosavi, Horieh

2017-01-01

Background This study investigated the effect of post bleaching treatments to the change of enamel elastic modulus and microhardness after dental bleaching in- vitro. Material and Methods Fifty bovine incisor slab were randomly assigned into five groups (n=10). The samples were bleached for three times; 20 minutes each time, by 40% hydrogen peroxide. Next it was applied fractional CO2 laser for two minutes, Nano- hydroxy apatite (N-HA) and MI-paste for 7 days and 2 minutes per day. The sound enamel and bleached teeth without post treatment remained as control groups. The elastic modulus and microhardness were measured at three times; 24 hours, 1 and 2 months. Data were statistically analyzed by two-way analysis of variance with 95% confidence level. Results Different methods of enamel treatment caused a significant increase in elastic modulus compared to bleached group (P<0.05). Modulus was significantly increased in 1 and 2 months (P<0/001: bleach, P= 0/015: laser, P= 0/008: NHA, P=0/010: MI paste) but there were no significantly difference between 1 and 2 months (P>0.05). There was any significance difference for hardness among treated and control groups, but hardness increased significantly by increasing storage time (P<0.05). Conclusions The use of the protective tested agents can be useful in clinical practice to reduce negative changes of enamel surface after whitening procedures. Key words:Bleaching enamel, CO2 laser, MI pastes, Nano-hydroxy apatite, Microhardness, Elastic modulus. PMID:29410753

Elastic Modulus Determination of Normal and Glaucomatous Human Trabecular Meshwork

PubMed Central

Last, Julie A.; Pan, Tingrui; Ding, Yuzhe; Reilly, Christopher M.; Keller, Kate; Acott, Ted S.; Fautsch, Michael P.; Murphy, Christopher J.; Russell, Paul

2011-01-01

Purpose. Elevated intraocular pressure (IOP) is a risk factor for glaucoma. The principal outflow pathway for aqueous humor in the human eye is through the trabecular meshwork (HTM) and Schlemm's canal (SC). The junction between the HTM and SC is thought to have a significant role in the regulation of IOP. A possible mechanism for the increased resistance to flow in glaucomatous eyes is an increase in stiffness (increased elastic modulus) of the HTM. In this study, the stiffness of the HTM in normal and glaucomatous tissue was compared, and a mathematical model was developed to predict the impact of changes in stiffness of the juxtacanalicular layer of HTM on flow dynamics through this region. Methods. Atomic force microscopy (AFM) was used to measure the elastic modulus of normal and glaucomatous HTM. According to these results, a model was developed that simulated the juxtacanalicular layer of the HTM as a flexible membrane with embedded pores. Results. The mean elastic modulus increased substantially in the glaucomatous HTM (mean = 80.8 kPa) compared with that in the normal HTM (mean = 4.0 kPa). Regional variation was identified across the glaucomatous HTM, possibly corresponding to the disease state. Mathematical modeling suggested an increased flow resistance with increasing HTM modulus. Conclusions. The data indicate that the stiffness of glaucomatous HTM is significantly increased compared with that of normal HTM. Modeling exercises support substantial impairment in outflow facility with increased HTM stiffness. Alterations in the biophysical attributes of the HTM may participate directly in the onset and progression of glaucoma. PMID:21220561

Characterization of ultraviolet light cured polydimethylsiloxane films for low-voltage, dielectric elastomer actuators

NASA Astrophysics Data System (ADS)

Töpper, Tino; Wohlfender, Fabian; Weiss, Florian; Osmani, Bekim; Müller, Bert

2016-04-01

The reduction the operation voltage has been the key challenge to realize of dielectric elastomer actuators (DEA) for many years - especially for the application fields of robotics, lens systems, haptics and future medical implants. Contrary to the approach of manipulating the dielectric properties of the electrically activated polymer (EAP), we intend to realize low-voltage operation by reducing the polymer thickness to the range of a few hundred nanometers. A study recently published presents molecular beam deposition to reliably grow nanometer-thick polydimethylsiloxane (PDMS) films. The curing of PDMS is realized using ultraviolet (UV) radiation with wavelengths from 180 to 400 nm radicalizing the functional side and end groups. The understanding of the mechanical properties of sub-micrometer-thin PDMS films is crucial to optimize DEAs actuation efficiency. The elastic modulus of UV-cured spin-coated films is measured by nano-indentation using an atomic force microscope (AFM) according to the Hertzian contact mechanics model. These investigations show a reduced elastic modulus with increased indentation depth. A model with a skin-like SiO2 surface with corresponding elastic modulus of (2.29 +/- 0.31) MPa and a bulk modulus of cross-linked PDMS with corresponding elastic modulus of (87 +/- 7) kPa is proposed. The surface morphology is observed with AFM and 3D laser microscopy. Wrinkled surface microstructures on UV-cured PDMS films occur for film thicknesses above (510 +/- 30) nm with an UV-irradiation density of 7.2 10-4 J cm-2 nm-1 at a wavelength of 190 nm.

Nanoscale deformation and fracture mechanics of polycrystalline silicon and diamond-like carbon for MEMS by the AFM/DIC method

NASA Astrophysics Data System (ADS)

Cho, Sung Woo

A method for nanoscale experimental mechanics was developed to address problems in deformation and fracture of micron-scale components in Microelectromechanical Systems (MEMS). Specifically, the effective and local, elastic and fracture behavior of polycrystalline silicon (polysilicon) and tetrahedral amorphous diamond-like carbon (ta-C) were studied using freestanding thin films subject to uniaxial tension. In this method, direct measurements of local deformations were derived from Atomic Force Microscopy (AFM) images in specimen areas varying between 1x2 mum2 and 15x15 mum2 using Digital Image Correlation (DIC) to extract displacements and strains with spatial resolution of 1-2 nm. The effective elastic modulus and Poisson's ratio of polysilicon and ta-C from the Sandia National Laboratories (SUMMiT) were 155 +/- 6 GPa and 0.22 +/- 0.02, and 759 +/- 22 GPa and 0.17 +/- 0.03, respectively. Similarly, the elastic modulus and Poisson's ratio of polysilicon fabricated at MCNC via the Multi-User MEMS Processes (MUMPs) with <110> texture were 164 +/- 7 GPa and 0.22 +/- 0.02, respectively. A second problem studied using the AFM/DIC method was the fracture of polysilicon in the presence of atomically sharp cracks. The effective (macroscopic) Mode-I critical stress intensity factor for polysilicon from different MUMPs runs was 1.00 +/- 0.1 MPa√m, where 0.1 MPa√m was the standard deviation, attributed to local cleavage anisotropy and grain boundary toughening. The variation in the effective critical stress intensity factor and the subcritical crack growth of polysilicon that was spatially recorded and quantified for the first time were the result of the spatial variation of the 4 local stress intensity factor at the crack tip that controlled crack initiation and thus, the overall fracture process. The AFM/DIC method was also applied to determine the minimum size of a polysilicon domain whose effective mechanical behavior could be described by the isotropic elastic constants. The isotropic material constants are applicable to MEMS components comprised of at least 15x15 grains, which correspond to a specimen area of 10x10-mum2 for SUMMiT and of 5x5-mum2 for MUMPs polysilicon, respectively.

A first-principles study of elastic and diffusion properties of magnesium based alloys

NASA Astrophysics Data System (ADS)

Ganeshan, Swetha

2011-12-01

In this thesis, the influence of alloying elements on the elastic and diffusion properties of Magnesium (Mg) has been studied based on first-principles density functional theory. The stress-strain method has been used to predict the elastic constants of the Mg based alloys studied herein. This method involves calculating the resultant change in stress due to application of strain. The validity of this method has been successfully tested for both 0K as well as at finite temperatures. The elastic constants predicted in this work have been correlated to ductility, fracture toughness, stiffness, elastic anisotropy and bond directionality, thus providing a better understanding of the influence of alloying elements on the mechanical and physical properties of Mg. Elastic constants, as a function of temperature have been predicted using first-principles quasi-static approximation. In this approach elastic stiffness coefficients calculated with respect to volume (cij( V)) have been correlated to the equilibrium volume as a function of temperature V(T) from phonon calculations to obtain temperature dependence of elastic stiffness coefficients cij(T). To compare our calculated temperature dependent elastic constants with that of experiments an isentropic correction term has been introduced. It is seen that the influence of this isentropic correction term on the elastic constants becomes significant at high temperatures. The quasi-static approximation has been primarily applied to calculate temperature dependent elastic constants of Mg2Ge, Mg2Si, Mg 2Sn and Mg2Pb. In the case of dilute Mg alloys, a 36 atom supercell with 35 atoms of Mg and one atom of the alloying impurity has been used for calculating the corresponding elastic constants. It is seen that there is a direct correspondence between the trends in the elastic constants and the lattice parameters of all the Mg based alloys studied herein. Elements that cause a decrease (increase) in the lattice constants result in an increase (decrease) in the bulk modulus. Self-diffusion calculations of Mg have been performed within both LDA and GGA. It is seen that, in the absence of surface corrections, while results of the two approximations (i.e. LDA and GGA) bound experimental data, better agreement is seen with respect to results from LDA, in comparison with experimental measurements. The effect of thermal expansion on the diffusivity of Mg has been studied using both HA and QHA. It is seen that the influence of anharmonicity on the diffusivity of Mg is negligible. Self-diffusion of Mg is faster in the basal plane than between adjacent basal planes. Partial correlation factors corresponding to the diffusion of a Mg atom from one basal plane to the adjacent basal plane, i.e. fBx and fBz, decrease with temperature whereas the partial correlation factor corresponding to the diffusion of Mg atom within the basal plane, i.e. fAx , increases with temperature. The ratio of jump frequencies w⊥/w∥ for self-diffusion of Mg increase with increase in temperature. The method used to calculate self-diffusion coefficients has been extended to compute impurity diffusion coefficients of Al, Ca, Sn and Zn in Mg. For these calculations, a 36 atom supercell with 1 vacant site and 1 impurity has been used. The 8-frequencey model has been implemented to obtain the different atom jump frequencies in order to calculate impurity diffusion coefficients in Mg. The trend in the impurity diffusion coefficients, with the exception of DZn-Mg is as follows: D Mg-Ca>DMg>DMg-Sn> DMg-Al. For impurity diffusion of Zn in Mg, at high temperatures DMg-Zn overlaps with that of DMg-Al , while at low temperatures it overlaps with that of D Mg-Sn. The different atom jump frequencies computed during the diffusion calculations are seen to be temperature dependent, increasing with increase in temperature. The correlation factors for all the alloy systems considered herein, is close to 1. This is expected to be due to the close packing of Mg lattice. (Abstract shortened by UMI.)

Estimation of the Young’s modulus of cellulose Iß by MM3 and quantum mechanics

USDA-ARS?s Scientific Manuscript database

Young’s modulus provides a measure of the resistance to deformation of an elastic material. In this study, modulus estimations for models of cellulose Iß relied on calculations performed with molecular mechanics (MM) and quantum mechanics (QM) programs. MM computations used the second generation emp...

Second order Method for Solving 3D Elasticity Equations with Complex Interfaces

PubMed Central

Wang, Bao; Xia, Kelin; Wei, Guo-Wei

2015-01-01

Elastic materials are ubiquitous in nature and indispensable components in man-made devices and equipments. When a device or equipment involves composite or multiple elastic materials, elasticity interface problems come into play. The solution of three dimensional (3D) elasticity interface problems is significantly more difficult than that of elliptic counterparts due to the coupled vector components and cross derivatives in the governing elasticity equation. This work introduces the matched interface and boundary (MIB) method for solving 3D elasticity interface problems. The proposed MIB elasticity interface scheme utilizes fictitious values on irregular grid points near the material interface to replace function values in the discretization so that the elasticity equation can be discretized using the standard finite difference schemes as if there were no material interface. The interface jump conditions are rigorously enforced on the intersecting points between the interface and the mesh lines. Such an enforcement determines the fictitious values. A number of new techniques has been developed to construct efficient MIB elasticity interface schemes for dealing with cross derivative in coupled governing equations. The proposed method is extensively validated over both weak and strong discontinuity of the solution, both piecewise constant and position-dependent material parameters, both smooth and nonsmooth interface geometries, and both small and large contrasts in the Poisson’s ratio and shear modulus across the interface. Numerical experiments indicate that the present MIB method is of second order convergence in both L∞ and L2 error norms for handling arbitrarily complex interfaces, including biomolecular surfaces. To our best knowledge, this is the first elasticity interface method that is able to deliver the second convergence for the molecular surfaces of proteins.. PMID:25914422

Improving impact resistance of ceramic materials by energy absorbing surface layers

NASA Technical Reports Server (NTRS)

Kirchner, H. P.; Seretsky, J.

1974-01-01

Energy absorbing surface layers were used to improve the impact resistance of silicon nitride and silicon carbide ceramics. Low elastic modulus materials were used. In some cases, the low elastic modulus was achieved using materials that form localized microcracks as a result of thermal expansion anisotropy, thermal expansion differences between phases, or phase transformations. In other cases, semi-vitreous or vitreous materials were used. Substantial improvements in impact resistance were observed at room and elevated temperatures.

A Focused Fundamental Study of Predicting Materials Degradation & Fatigue. Volume 1

DTIC Science & Technology

1997-05-31

physical properties are: bulk modulus, shear strength, coefficient of friction, modulus of elasticity/ rigidity and Poisson’s ratio. Each of these physical...acting on a subsurface crack when abrasive motion occurs on the surface using linear elastic fracture mechanics theory. Both mechanisms involve a...The body of the scattering 5 cell was a 4-way Swagelok*(Crawford Fitting Co., Solon, OH) connector with a 1.5 mm hole drilled in the top for

Substrate-dependent cell elasticity measured by optical tweezers indentation

NASA Astrophysics Data System (ADS)

Yousafzai, Muhammad S.; Ndoye, Fatou; Coceano, Giovanna; Niemela, Joseph; Bonin, Serena; Scoles, Giacinto; Cojoc, Dan

2016-01-01

In the last decade, cell elasticity has been widely investigated as a potential label free indicator for cellular alteration in different diseases, cancer included. Cell elasticity can be locally measured by pulling membrane tethers, stretching or indenting the cell using optical tweezers. In this paper, we propose a simple approach to perform cell indentation at pN forces by axially moving the cell against a trapped microbead. The elastic modulus is calculated using the Hertz-model. Besides the axial component, the setup also allows us to examine the lateral cell-bead interaction. This technique has been applied to measure the local elasticity of HBL-100 cells, an immortalized human cell line, originally derived from the milk of a woman with no evidence of breast cancer lesions. In addition, we have studied the influence of substrate stiffness on cell elasticity by performing experiments on cells cultured on two substrates, bare and collagen-coated, having different stiffness. The mean value of the cell elastic modulus measured during indentation was 26±9 Pa for the bare substrate, while for the collagen-coated substrate it diminished to 19±7 Pa. The same trend was obtained for the elastic modulus measured during the retraction of the cell: 23±10 Pa and 13±7 Pa, respectively. These results show the cells adapt their stiffness to that of the substrate and demonstrate the potential of this setup for low-force probing of modifications to cell mechanics induced by the surrounding environment (e.g. extracellular matrix or other cells).

Oxynitride glass fibers

NASA Technical Reports Server (NTRS)

Patel, Parimal J.; Messier, Donald R.; Rich, R. E.

1991-01-01

Research at the Army Materials Technology Laboratory (AMTL) and elsewhere has shown that many glass properties including elastic modulus, hardness, and corrosion resistance are improved markedly by the substitution of nitrogen for oxygen in the glass structure. Oxynitride glasses, therefore, offer exciting opportunities for making high modulus, high strength fibers. Processes for making oxynitride glasses and fibers of glass compositions similar to commercial oxide glasses, but with considerable enhanced properties, are discussed. We have made glasses with elastic moduli as high as 140 GPa and fibers with moduli of 120 GPa and tensile strengths up to 2900 MPa. AMTL holds a U.S. patent on oxynitride glass fibers, and this presentation discusses a unique process for drawing small diameter oxynitride glass fibers at high drawing rates. Fibers are drawn through a nozzle from molten glass in a molybdenum crucible at 1550 C. The crucible is situated in a furnace chamber in flowing nitrogen, and the fiber is wound in air outside of the chamber, making the process straightforward and commercially feasible. Strengths were considerably improved by improving glass quality to minimize internal defects. Though the fiber strengths were comparable with oxide fibers, work is currently in progress to further improve the elastic modulus and strength of fibers. The high elastic modulus of oxynitride glasses indicate their potential for making fibers with tensile strengths surpassing any oxide glass fibers, and we hope to realize that potential in the near future.

A small punch test technique for characterizing the elastic modulus and fracture behavior of PMMA bone cement used in total joint replacement.

PubMed

Giddings, V L; Kurtz, S M; Jewett, C W; Foulds, J R; Edidin, A A

2001-07-01

Polymethylmethacrylate (PMMA) bone cement is used in total joint replacements to anchor implants to the underlying bone. Establishing and maintaining the integrity of bone cement is thus of critical importance to the long-term outcome of joint replacement surgery. The goal of the present study was to evaluate the suitability of a novel testing technique, the small punch or miniaturized disk bend test, to characterize the elastic modulus and fracture behavior of PMMA. We investigated the hypothesis that the crack initiation behavior of PMMA during the small punch test was sensitive to the test temperature. Miniature disk-shaped specimens, 0.5 mm thick and 6.4 mm in diameter, were prepared from PMMA and Simplex-P bone cement according to manufacturers' instructions. Testing was conducted at ambient and body temperatures, and the effect of test temperature on the elastic modulus and fracture behavior was statistically evaluated using analysis of variance. For both PMMA materials, the test temperature had a significant effect on elastic modulus and crack initiation behavior. At body temperature, the specimens exhibited "ductile" crack initiation, whereas at room temperature "brittle" crack initiation was observed. The small punch test was found to be a sensitive and repeatable test method for evaluating the mechanical behavior of PMMA. In light of the results of this study, future small punch testing should be conducted at body temperature.

Nano and micro mechanical properties of uncross-linked and cross-linked chitosan films

PubMed Central

Aryaei, Ashkan; Jayatissa, Ahalapitiya H.; Jayasuriya, A. Champa

2016-01-01

The aim of this study is to determine the nano and micro mechanical properties for uncross-linked and cross-linked chitosan films. Specifically, we looked at nanoindentation hardness, microhardness, and elastic modulus. It is important to study the nano and microscale mechanical properties of chitosan since chitosan has been widely used for biomedical applications. Using the solvent-cast method, the chitosan films were prepared at room temperature on the cleaned glass plates. The chitosan solution was prepared by dissolving chitosan in acetic acid 1% (v/v). Tripolyphosphate (TPP) was used to create the cross-links between amine groups in chitosan and phosphate groups in TPP. In this study, atomic force microscopy was used to measure the nanoindentation hardness and surface topography of the uncross-linked and cross-linked chitosan films. Elastic modulus was then calculated from the nanoindentation results. The effective elastic modulus was determined by microhardness with some modifications to previous theories. The microhardness of the chitosan films were measured using Vicker’s hardness meter under three different loads. Our results show that the microhardness and elastic modulus for cross-linked chitosan films are higher than the uncross-linked films. However, the cross-linked chitosan films show increased brittleness when compared to uncross-linked films. By increasing the load magnitude, the microhardness increases for both uncross-linked and cross-linked chitosan films. PMID:22100082

Porous titanium materials with entangled wire structure for load-bearing biomedical applications.

PubMed

He, Guo; Liu, Ping; Tan, Qingbiao

2012-01-01

A kind of porous metal-entangled titanium wire material has been investigated in terms of the pore structure (size and distribution), the strength, the elastic modulus, and the mechanical behavior under uniaxial tensile loading. Its functions and potentials for surgical application have been explained. In particular, its advantages over competitors (e.g., conventional porous titanium) have been reviewed. In the study, a group of entangled titanium wire materials with non-woven structure were fabricated by using 12-180 MPa forming pressure, which have porosity in a range of 48%-82%. The pores in the materials are irregular in shape, which have a nearly half-normal distribution in size range. The yield strength, ultimate tensile strength, and elastic modulus are 75 MPa, 108 MPa, and 1.05 GPa, respectively, when its porosity is 44.7%. The mechanical properties decrease significantly as the porosity increases. When the porosity is 57.9%, these values become 24 MPa, 47.5 MPa, and 0.33 GPa, respectively. The low elastic modulus is due to the structural flexibility of the entangled titanium wire materials. For practical reference, a group of detailed data of the porous structure and the mechanical properties are reported. This kind of material is very promising for implant applications because of their very good toughness, perfect flexibility, high strength, adequate elastic modulus, and low cost. Copyright © 2011 Elsevier Ltd. All rights reserved.

PECVD silicon-rich nitride and low stress nitride films mechanical characterization using membrane point load deflection

NASA Astrophysics Data System (ADS)

Bagolini, Alvise; Picciotto, Antonino; Crivellari, Michele; Conci, Paolo; Bellutti, Pierluigi

2016-02-01

An analysis of the mechanical properties of plasma enhanced chemical vapor (PECVD) silicon nitrides is presented, using micro fabricated silicon nitride membranes under point load deflection. The membranes are made of PECVD silicon-rich nitride and low stress nitride films. The mechanical performance of the bended membranes is examined both with analytical models and finite element simulation in order to extract the elastic modulus and residual stress values. The elastic modulus of low stress silicon nitride is calculated using stress free analytical models, while for silicon-rich silicon nitride and annealed low stress silicon nitride it is estimated with a pre-stressed model of point-load deflection. The effect of annealing both in nitrogen and hydrogen atmosphere is evaluated in terms of residual stress, refractive index and thickness variation. It is demonstrated that a hydrogen rich annealing atmosphere induces very little change in low stress silicon nitride. Nitrogen annealing effects are measured and shown to be much higher in silicon-rich nitride than in low stress silicon nitride. An estimate of PECVD silicon-rich nitride elastic modulus is obtained in the range between 240-320 GPa for deposited samples and 390 GPa for samples annealed in nitrogen atmosphere. PECVD low stress silicon nitride elastic modulus is estimated to be 88 GPa as deposited and 320 GPa after nitrogen annealing.

Size dependent elastic modulus and mechanical resilience of dental enamel.

PubMed

O'Brien, Simona; Shaw, Jeremy; Zhao, Xiaoli; Abbott, Paul V; Munroe, Paul; Xu, Jiang; Habibi, Daryoush; Xie, Zonghan

2014-03-21

Human tooth enamel exhibits a unique microstructure able to sustain repeated mechanical loading during dental function. Although notable advances have been made towards understanding the mechanical characteristics of enamel, challenges remain in the testing and interpretation of its mechanical properties. For example, enamel was often tested under dry conditions, significantly different from its native environment. In addition, constant load, rather than indentation depth, has been used when mapping the mechanical properties of enamel. In this work, tooth specimens are prepared under hydrated conditions and their stiffnesses are measured by depth control across the thickness of enamel. Crystal arrangement is postulated, among other factors, to be responsible for the size dependent indentation modulus of enamel. Supported by a simple structure model, effective crystal orientation angle is calculated and found to facilitate shear sliding in enamel under mechanical contact. In doing so, the stress build-up is eased and structural integrity is maintained. Copyright © 2014 Elsevier Ltd. All rights reserved.

Influence of CeO2 on structural properties of glasses by using ultrasonic technique: comparison between the local sand and SiO2.

PubMed

Laopaiboon, Raewat; Bootjomchai, Cherdsak

2013-04-01

Comparison between the local sand and SiO2 with different compositions of CeO2 on the structural properties of glasses was carried out by using ultrasonic technique. The ultrasonic velocities were measured by the pulse echo technique with a frequency of 4 MHz and at room temperature. From these obtained velocities and densities, various elastic moduli, micro-hardness and Poisson's ratio were calculated. The interesting point of the bulk modulus (SiO2 glass system) decreases at x = 1.25 mol.% initially before it turns to increase between x = 3.75 and x = 5.00 mol.%. While the bulk modulus of the local sand glass system is near constant. FTIR spectra were used to study the structural properties of the prepared glass system. The results supported our discussion of the formation of non-bridging oxygens (NBO) and bridging oxygens (BO). Copyright © 2013 Elsevier B.V. All rights reserved.

Investigation of the elastic modulus, tensile and flexural strength of five skull simulant materials for impact testing of a forensic skin/skull/brain model.

PubMed

Falland-Cheung, Lisa; Waddell, J Neil; Chun Li, Kai; Tong, Darryl; Brunton, Paul

2017-04-01

Conducting in vitro research for forensic, impact and injury simulation modelling generally involves the use of a skull simulant with mechanical properties similar to those found in the human skull. For this study epoxy resin, fibre filled epoxy resin, 3D-printing filaments (PETG, PLA) and self-cure acrylic denture base resin were used to fabricate the specimens (n=20 per material group), according to ISO 527-2 IBB and ISO20795-1. Tensile and flexural testing in a universal testing machine was used to measure their tensile/flexural elastic modulus and strength. The results showed that the epoxy resin and fibre filled epoxy resin had similar tensile elastic moduli (no statistical significant difference) with lower values observed for the other materials. The fibre filled epoxy resin had a considerably higher flexural elastic modulus and strength, possibly attributed to the presence of fibres. Of the simulants tested, epoxy resin had an elastic modulus and flexural strength close to that of mean human skull values reported in the literature, and thus can be considered as a suitable skull simulant for a skin/skull/brain model for lower impact forces that do not exceed the fracture stress. For higher impact forces a 3D printing filament (PLA) may be a more suitable skull simulant material, due to its closer match to fracture stresses found in human skull bone. Influencing factors were also anisotropy, heterogeneity and viscoelasticity of human skull bone and simulant specimens. Copyright © 2017 Elsevier Ltd. All rights reserved.

Dynamic analysis of bulk-fill composites: Effect of food-simulating liquids.

PubMed

Eweis, Ahmed Hesham; Yap, Adrian U-Jin; Yahya, Noor Azlin

2017-10-01

This study investigated the effect of food simulating liquids on visco-elastic properties of bulk-fill restoratives using dynamic mechanical analysis. One conventional composite (Filtek Z350 [FZ]), two bulk-fill composites (Filtek Bulk-fill [FB] and Tetric N Ceram [TN]) and a bulk-fill giomer (Beautifil-Bulk Restorative [BB]) were evaluated. Specimens (12 × 2 × 2mm) were fabricated using customized stainless steel molds. The specimens were light-cured, removed from their molds, finished, measured and randomly divided into six groups. The groups (n = 10) were conditioned in the following mediums for 7 days at 37°C: air (control), artificial saliva (SAGF), distilled water, 0.02N citric acid, heptane, 50% ethanol-water solution. Specimens were assessed using dynamic mechanical testing in flexural three-point bending mode and their respective mediums at 37°C and a frequency range of 0.1-10Hz. The distance between the supports were fixed at 10mm and an axial load of 5N was employed. Data for elastic modulus, viscous modulus and loss tangent were subjected to ANOVA/Tukey's tests at significance level p < 0.05. Significant differences in visco-elastic properties were observed between materials and mediums. Apart from bulk-fill giomer, elastic modulus was the highest after conditioning in heptane. No apparent trends were noted for viscous modulus. Generally, loss tangent was the highest after conditioning in ethanol. The effect of food-simulating liquids on the visco-elastic properties of bulk-fill composites was material and medium dependent. Copyright © 2017 Elsevier Ltd. All rights reserved.

Effect of AlF3 on the Density and Elastic Properties of Zinc Tellurite Glass Systems

PubMed Central

Sidek, Haji Abdul Aziz; Rosmawati, Shaharuddin; Halimah, Mohamed Kamari; Matori, Khamirul Amin; Talib, Zainal Abidin

2012-01-01

This paper presents the results of the physical and elastic properties of the ternary zinc oxyfluoro tellurite glass system. Systematic series of glasses (AlF3)x(ZnO)y(TeO2)z with x = 0–19, y = 0–20 and z = 80, 85, 90 mol% were synthesized by the conventional rapid melt quenching technique. The composition dependence of the physical, mainly density and molar volume, and elastic properties is discussed in term of the AlF3 modifiers addition that are expected to produce quite substantial changes in their physical properties. The absence of any crystalline peaks in the X-ray diffraction (XRD) patterns of the present glass samples indicates the amorphous nature. The addition of AlF3 lowered the values of the densities in ternary oxyfluorotellurite glass systems. The longitudinal and transverse ultrasonic waves propagated in each glass sample were measured using a MBS8020 ultrasonic data acquisition system. All the velocity data were taken at 5 MHz frequency and room temperature. The longitudinal modulus (L), shear modulus (G), Young’s modulus (E), bulk modulus (K) and Poisson’s ratio (σ) are obtained from both velocities data and their respective density. Experimental data shows the density and elastic moduli of each AlF3-ZnO-TeO2 series are found strongly depend upon the glass composition. The addition of AlF3 modifiers into the zinc tellurite causes substantial changes in their density, molar volume as well as their elastic properties.

Development of Space Station strut design

NASA Technical Reports Server (NTRS)

Johnson, R. R.; Bluck, R. M.; Holmes, A. M. C.; Kural, M. H.

1986-01-01

Candidate Space Station struts exhibiting high stiffness (38-40 msi modulus of elasticity) were manufactured and experimentally evaluated. One and two inch diameter aluminum-clad evaluation specimens were manufactured using a unique dry fiber resin injection process. Preliminary tests were performed on strut elements having 80 percent high-modulus graphite epoxy and 20 percent aluminum. Performed tests included modulus of elasticity, thermal cycling, and coefficient of thermal expansion. The paper describes the design approach, including an analytical assessment of strut thermal deformation behavior. The major thrust of this paper is the manufacturing process which produces aluminum-clad struts with precisely controlled properties which can be fine-tuned after fabrication. An impact test and evaluation procedure for evaluating toughness is described.

Elastic Properties in Tension and Shear of High Strength Nonferrous Metals and Stainless Steel - Effect of Previous Deformation and Heat Treatment

NASA Technical Reports Server (NTRS)

Mebs, R W; Mcadam, D J

1947-01-01

A resume is given of an investigation of the influence of plastic deformation and of annealing temperature on the tensile and shear elastic properties of high strength nonferrous metals and stainless steels in the form of rods and tubes. The data were obtained from earlier technical reports and notes, and from unpublished work in this investigation. There are also included data obtained from published and unpublished work performed on an independent investigation. The rod materials, namely, nickel, monel, inconel, copper, 13:2 Cr-Ni steel, and 18:8 Cr-Ni steel, were tested in tension; 18:8 Cr-Ni steel tubes were tested in shear, and nickel, monel, aluminum-monel, and Inconel tubes were tested in both tension and shear. There are first described experiments on the relationship between hysteresis and creep, as obtained with repeated cyclic stressing of annealed stainless steel specimens over a constant load range. These tests, which preceded the measurements of elastic properties, assisted in devising the loading time schedule used in such measurements. From corrected stress-set curves are derived the five proof stresses used as indices of elastic or yield strength. From corrected stress-strain curves are derived the secant modulus and its variation with stress. The relationship between the forms of the stress-set and stress-strain curves and the values of the properties derived is discussed. Curves of variation of proof stress and modulus with prior extension, as obtained with single rod specimens, consist in wavelike basic curves with superposed oscillations due to differences of rest interval and extension spacing; the effects of these differences are studied. Oscillations of proof stress and modulus are generally opposite in manner. The use of a series of tubular specimens corresponding to different amounts of prior extension of cold reduction gave curves almost devoid of oscillation since the effects of variation of rest interval and extension spacing were removed. Comparison is also obtained between the variation of the several properties, as measured in tension and in shear. The rise of proof stress with extension is studied, and the work-hardening rates of the various metals evaluated. The ratio between the tensile and shear proof stresses for the various annealed and cold-worked tubular metals is likewise calculated. The influence of annealing or tempering temperature on the proof stresses and moduli for the cold-worked metals and for air-hardened 13:2 Cr-Ni steel is investigated. An improvement of elastic strength generally is obtained, without important loss of yield strength, by annealing at suitable temperature. The variation of the proof stress and modulus of elasticity with plastic deformation or annealing temperature is explained in terms of the relative dominance of three important factors: namely, (a) internal stress, (b) lattice-expansion or work-hardening, and (c) crystal reorientation. Effective values of Poisson's ratio were computed from tensile and shear moduli obtained on tubular specimens. The variation of Poisson's ratio with plastic deformation and annealing temperature is explained in terms of the degree of anisotropy produced by changes of (a) internal stress and (b) crystal orientation.

TiCN thin films grown by reactive crossed beam pulsed laser deposition

NASA Astrophysics Data System (ADS)

Escobar-Alarcón, L.; Camps, E.; Romero, S.; Muhl, S.; Camps, I.; Haro-Poniatowski, E.

2010-12-01

In this work, we used a crossed plasma configuration where the ablation of two different targets in a reactive atmosphere was performed to prepare nanocrystalline thin films of ternary compounds. In order to assess this alternative deposition configuration, titanium carbonitride (TiCN) thin films were deposited. Two crossed plasmas were produced by simultaneously ablating titanium and graphite targets in an Ar/N2 atmosphere. Films were deposited at room temperature onto Si (100) and AISI 4140 steel substrates whilst keeping the ablation conditions of the Ti target constant. By varying the laser fluence on the carbon target it was possible to study the effect of the carbon plasma on the characteristics of the deposited TiCN films. The structure and composition of the films were analyzed by X-ray Diffraction, Raman Spectroscopy and non-Rutherford Backscattering Spectroscopy. The hardness and elastic modulus of the films was also measured by nanoindentation. In general, the experimental results showed that the TiCN thin films were highly oriented in the (111) crystallographic direction with crystallite sizes as small as 6.0 nm. It was found that the hardness increased as the laser fluence was increased, reaching a maximum value of about 33 GPa and an elastic modulus of 244 GPa. With the proposed configuration, the carbon content could be easily varied from 42 to 5 at.% by changing the laser fluence on the carbon target.

Intrinsic properties and strengthening mechanism of monocrystalline Ni-containing ternary concentrated solid solutions

DOE PAGES

Jin, K.; Gao, Y. F.; Bei, H.

2017-04-07

Ternary single-phase concentrated solid solution alloys (SP-CSAs), so-called "medium entropy alloys", not only possess notable mechanical and physical properties but also form a model system linking the relatively simple binary alloys to the complex high entropy alloys. Our knowledge of their intrinsic properties is vital to understand the material behavior and to prompt future applications. To this end, three model alloys NiCoFe, NiCoCr, and NiFe-20Cr have been selected and grown as single crystals. We measured their elastic constants using an ultrasonic method, and several key materials properties, such as shear modulus, bulk modulus, elastic anisotropy, and Debye temperatures have beenmore » derived. Furthermore, nanoindentation tests have been performed on these three alloys together with Ni, NiCo and NiFe on their (100) surface, to investigate the strengthening mechanisms. NiCoCr has the highest hardness, NiFe, NiCoFe and NiFe-20Cr share a similar hardness that is apparently lower than NiCoCr; NiCo has the lowest hardness in the alloys, which is similar to elemental Ni. The Labusch-type solid solution model has been applied to interpret the nanoindentation data, with two approaches used to calculate the lattice mismatch. Finally, by adopting an interatomic spacing matrix method, the Labusch model can reasonably predict the hardening effects for the whole set of materials.« less

Elasticity of human embryonic stem cells as determined by atomic force microscopy.

PubMed

Kiss, Robert; Bock, Henry; Pells, Steve; Canetta, Elisabetta; Adya, Ashok K; Moore, Andrew J; De Sousa, Paul; Willoughby, Nicholas A

2011-10-01

The expansive growth and differentiation potential of human embryonic stem cells (hESCs) make them a promising source of cells for regenerative medicine. However, this promise is off set by the propensity for spontaneous or uncontrolled differentiation to result in heterogeneous cell populations. Cell elasticity has recently been shown to characterize particular cell phenotypes, with undifferentiated and differentiated cells sometimes showing significant differences in their elasticities. In this study, we determined the Young's modulus of hESCs by atomic force microscopy using a pyramidal tip. Using this method we are able to take point measurements of elasticity at multiple locations on a single cell, allowing local variations due to cell structure to be identified. We found considerable differences in the elasticity of the analyzed hESCs, reflected by a broad range of Young's modulus (0.05-10 kPa). This surprisingly high variation suggests that elasticity could serve as the basis of a simple and efficient large scale purification/separation technique to discriminate subpopulations of hESCs.

Temperature dependence of the elastic moduli and damping for polycrystalline LiF-22 pct CaF2 eutectic salt

NASA Technical Reports Server (NTRS)

Wolfenden, A.; Lastrapes, G.; Duggan, M. B.; Raj, S. V.

1991-01-01

Young's and shear moduli and damping were measured for as-cast polycrystalline LiF-(22 mol pct)CaF2 eutectic specimens as a function of temperature using the piezoelectric ultrasonic composite oscillator technique. The shear modulus decreased with increasing temperature from about 40 GPa at 295 K to about 30 GPa at 1000 K, while the Young modulus decreased from about 115 GPa at 295 K to about 35 GPa at 900 K. These values are compared with those derived from the rule of mixtures using elastic moduli data for LiF and CaF2 single crystals. It is shown that, while the shear modulus data agree reasonably well with the predicted trend, there is a large discrepancy between the theoretical calculations and the Young modulus values, where this disagreement increases with increasing temperature.

The optimal density of cellular solids in axial tension.

PubMed

Mihai, L Angela; Alayyash, Khulud; Wyatt, Hayley

2017-05-01

For cellular bodies with uniform cell size, wall thickness, and shape, an important question is whether the same volume of material has the same effect when arranged as many small cells or as fewer large cells. To answer this question, for finite element models of periodic structures of Mooney-type material with different structural geometry and subject to large strain deformations, we identify a nonlinear elastic modulus as the ratio between the mean effective stress and the mean effective strain in the solid cell walls, and show that this modulus increases when the thickness of the walls increases, as well as when the number of cells increases while the volume of solid material remains fixed. Since, under the specified conditions, this nonlinear elastic modulus increases also as the corresponding mean stress increases, either the mean modulus or the mean stress can be employed as indicator when the optimum wall thickness or number of cells is sought.

Dynamics of an elastic sphere containing a thin creeping region and immersed in an acoustic region for similar viscous-elastic and acoustic time- and length-scales

NASA Astrophysics Data System (ADS)

Gat, Amir; Friedman, Yonathan

2017-11-01

The characteristic time of low-Reynolds number fluid-structure interaction scales linearly with the ratio of fluid viscosity to solid Young's modulus. For sufficiently large values of Young's modulus, both time- and length-scales of the viscous-elastic dynamics may be similar to acoustic time- and length-scales. However, the requirement of dominant viscous effects limits the validity of such regimes to micro-configurations. We here study the dynamics of an acoustic plane wave impinging on the surface of a layered sphere, immersed within an inviscid fluid, and composed of an inner elastic sphere, a creeping fluid layer and an external elastic shell. We focus on configurations with similar viscous-elastic and acoustic time- and length-scales, where the viscous-elastic speed of interaction between the creeping layer and the elastic regions is similar to the speed of sound. By expanding the linearized spherical Reynolds equation into the relevant spectral series solution for the hyperbolic elastic regions, a global stiffness matrix of the layered elastic sphere was obtained. This work relates viscous-elastic dynamics to acoustic scattering and may pave the way to the design of novel meta-materials with unique acoustic properties. ISF 818/13.

Charge-regularized swelling kinetics of polyelectrolyte gels: Elasticity and diffusion

NASA Astrophysics Data System (ADS)

Sen, Swati; Kundagrami, Arindam

2017-11-01

We apply a recently developed method [S. Sen and A. Kundagrami, J. Chem. Phys. 143, 224904 (2015)], using a phenomenological expression of osmotic stress, as a function of polymer and charge densities, hydrophobicity, and network elasticity for the swelling of spherical polyelectrolyte (PE) gels with fixed and variable charges in a salt-free solvent. This expression of stress is used in the equation of motion of swelling kinetics of spherical PE gels to numerically calculate the spatial profiles for the polymer and free ion densities at different time steps and the time evolution of the size of the gel. We compare the profiles of the same variables obtained from the classical linear theory of elasticity and quantitatively estimate the bulk modulus of the PE gel. Further, we obtain an analytical expression of the elastic modulus from the linearized expression of stress (in the small deformation limit). We find that the estimated bulk modulus of the PE gel decreases with the increase of its effective charge for a fixed degree of deformation during swelling. Finally, we match the gel-front locations with the experimental data, taken from the measurements of charged reversible addition-fragmentation chain transfer gels to show an increase in gel-size with charge and also match the same for PNIPAM (uncharged) and imidazolium-based (charged) minigels, which specifically confirms the decrease of the gel modulus value with the increase of the charge. The agreement between experimental and theoretical results confirms general diffusive behaviour for swelling of PE gels with a decreasing bulk modulus with increasing degree of ionization (charge). The new formalism captures large deformations as well with a significant variation of charge content of the gel. It is found that PE gels with large deformation but same initial size swell faster with a higher charge.

Mapping of elasticity and damping in an α + β titanium alloy through atomic force acoustic microscopy

PubMed Central

Phani, M Kalyan; Kumar, Anish; Jayakumar, T; Samwer, Konrad

2015-01-01

Summary The distribution of elastic stiffness and damping of individual phases in an α + β titanium alloy (Ti-6Al-4V) measured by using atomic force acoustic microscopy (AFAM) is reported in the present study. The real and imaginary parts of the contact stiffness k * are obtained from the contact-resonance spectra and by using these two quantities, the maps of local elastic stiffness and the damping factor are derived. The evaluation of the data is based on the mass distribution of the cantilever with damped flexural modes. The cantilever dynamics model considering damping, which was proposed recently, has been used for mapping of indentation modulus and damping of different phases in a metallic structural material. The study indicated that in a Ti-6Al-4V alloy the metastable β phase has the minimum modulus and the maximum damping followed by α′- and α-phases. Volume fractions of the individual phases were determined by using a commercial material property evaluation software and were validated by using X-ray diffraction (XRD) and electron back-scatter diffraction (EBSD) studies on one of the heat-treated samples. The volume fractions of the phases and the modulus measured through AFAM are used to derive average modulus of the bulk sample which is correlated with the bulk elastic properties obtained by ultrasonic velocity measurements. The average modulus of the specimens estimated by AFAM technique is found to be within 5% of that obtained by ultrasonic velocity measurements. The effect of heat treatments on the ultrasonic attenuation in the bulk sample could also be understood based on the damping measurements on individual phases using AFAM. PMID:25977847

Finite element analysis for transverse carpal ligament tensile strain and carpal arch area.

PubMed

Yao, Yifei; Erdemir, Ahmet; Li, Zong-Ming

2018-05-17

Mechanics of carpal tunnel soft tissue, such as fat, muscle and transverse carpal ligament (TCL), around the median nerve may render the median nerve vulnerable to compression neuropathy. The purpose of this study was to understand the roles of carpal tunnel soft tissue mechanical properties and intratunnel pressure on the TCL tensile strain and carpal arch area (CAA) using finite element analysis (FEA). Manual segmentation of the thenar muscles, skin, fat, TCL, hamate bone, and trapezium bone in the transverse plane at distal carpal tunnel were obtained from B-mode ultrasound images of one cadaveric hand. Sensitivity analyses were conducted to examine the dependence of TCL tensile strain and CAA on TCL elastic modulus (0.125-10 MPa volar-dorsally; 1.375-110 MPa transversely), skin-fat and thenar muscle initial shear modulus (1.6-160 kPa for skin-fat; 0.425-42.5 kPa for muscle), and intratunnel pressure (60-480 mmHg). Predictions of TCL tensile strain under different intratunnel pressures were validated with the experimental data obtained on the same cadaveric hand. Results showed that skin, fat and muscles had little effect on the TCL tensile strain and CAA changes. However, TCL tensile strain and CAA increased with decreased elastic modulus of TCL and increased intratunnel pressure. The TCL tensile strain and CAA increased linearly with increased pressure while increased exponentially with decreased elastic modulus of TCL. Softening the TCL by decreasing the elastic modulus may be an alternative clinical approach to carpal tunnel expansion to accommodate elevated intratunnel pressure and alleviate median nerve compression neuropathy. Copyright © 2018 Elsevier Ltd. All rights reserved.

Mapping of elasticity and damping in an α + β titanium alloy through atomic force acoustic microscopy.

PubMed

Phani, M Kalyan; Kumar, Anish; Jayakumar, T; Arnold, Walter; Samwer, Konrad

2015-01-01

The distribution of elastic stiffness and damping of individual phases in an α + β titanium alloy (Ti-6Al-4V) measured by using atomic force acoustic microscopy (AFAM) is reported in the present study. The real and imaginary parts of the contact stiffness k (*) are obtained from the contact-resonance spectra and by using these two quantities, the maps of local elastic stiffness and the damping factor are derived. The evaluation of the data is based on the mass distribution of the cantilever with damped flexural modes. The cantilever dynamics model considering damping, which was proposed recently, has been used for mapping of indentation modulus and damping of different phases in a metallic structural material. The study indicated that in a Ti-6Al-4V alloy the metastable β phase has the minimum modulus and the maximum damping followed by α'- and α-phases. Volume fractions of the individual phases were determined by using a commercial material property evaluation software and were validated by using X-ray diffraction (XRD) and electron back-scatter diffraction (EBSD) studies on one of the heat-treated samples. The volume fractions of the phases and the modulus measured through AFAM are used to derive average modulus of the bulk sample which is correlated with the bulk elastic properties obtained by ultrasonic velocity measurements. The average modulus of the specimens estimated by AFAM technique is found to be within 5% of that obtained by ultrasonic velocity measurements. The effect of heat treatments on the ultrasonic attenuation in the bulk sample could also be understood based on the damping measurements on individual phases using AFAM.

Fluid Effects on Shear for Seismic Waves in Finely Layered Porous Media

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

Berryman, J G

Although there are five effective shear moduli for any layered VTI medium, one and only one effective shear modulus of the layered system (namely the uniaxial shear) contains all the dependence of pore fluids on the elastic or poroelastic constants that can be observed in vertically polarized shear waves. Pore fluids can increase the magnitude the shear energy stored in this modulus by an amount that ranges from the smallest to the largest effective shear moduli of the VTI system. But, since there are five shear moduli in play, the overall increase in shear energy due to fluids is reducedmore » by a factor of about 5 in general. We can therefore give definite bounds on the maximum increase of overall shear modulus, being about 20% of the allowed range as liquid is fully substituted for gas. An attendant increase of density (depending on porosity and fluid density) by approximately 5 to 10% decreases the shear wave speed and, thereby, partially offsets the effect of this shear modulus increase. The final result is an increase of shear wave speed on the order of 5 to 10%. This increase is shown to be possible under most favorable circumstances - i.e. when the shear modulus fluctuations are large (resulting in strong anisotropy) and the medium behaves in an undrained fashion due to fluid trapping. At frequencies higher than seismic (such as sonic and ultrasonic waves for well-logging or laboratory experiments), resulting short response times also produce the requisite undrained behavior and, therefore, fluids also affect shear waves at high frequencies by increasing rigidity.« less

Structure and elasticity of serpentine at high-pressure

NASA Astrophysics Data System (ADS)

Mookherjee, Mainak; Stixrude, Lars

2009-03-01

Serpentines occur in the subduction zone settings, both along the slab and within the mantle wedge, they are candidates for transporting water in to the deep earth. Their presence is manifested by serpentine mud volcanoes, high electrical conductivities, magnetic and seismic anomalies. Using theoretical methods, we predict a pressure induced structural transformations in serpentine. The transformations are related to the behavior of the silicate framework and misfit between octahedral and tetrahedral layers. As the structure is compressed, the octahedral layer and tetrahedral layers are compressed at different rates. At 7 GPa, the misfit between the layers vanishes. This causes non-linear pressure dependence of tetrahedral rotational angle. This is also manifested by the onset of anomalous pressure dependence of the elastic constants c11, c33, c12, c13. Beyond 7 GPa, the misfit between the layers grows again reaching extremum at 22 GPa. This is also manifested by discontinuity in average Si-O bond length, volume of tetrahedron and re-orientation of hydroxyl vector. The symmetry of the crystal-structure however, remains unaffected. Evidence of pressure-induced hydrogen bonding is absent in serpentine, as evident from reduction of O-H bond length upon compression. Results of compression for the low-pressure regime ( P < 7 GPa) is well represented by a fourth order Birch-Murnaghan finite strain expression with K0 = 79 GPa, K0' = 12 and K0″ = - 2, where K is the bulk modulus, prime indicates pressure derivatives, and O refers to zero pressure. Our best estimates of K0, K0' and the Grüneisen parameter, γ at 300 K and zero pressure based on our results are: 61 GPa, 17, and 0.77, respectively. At low pressures, serpentine structure is anisotropic with c11 ~ 2.4 × c33. The pressure derivative of elastic constants ( ∂cij/ ∂P) are such, that around 22 GPa c11~ c33. An elastic instability ( c66 < 0) at somewhat higher pressures (> 50 GPa) is also noted. The elastic constant tensor reveals large acoustic anisotropy (41% in VP) and seismic wave velocities that are significantly higher than those inferred from experiments on serpentinites.

Elastic properties of single-walled carbon nanotube thin film by nanoindentation test.

PubMed

Tang, Xingling; El-Hami, Abdelkhalak; El-Hami, Khalil; Eid, Mohamed; Si, Chaorun

2017-09-12

This paper carries out a preliminary study for the elastic properties of single walled carbon nanotube (SWCNT) thin film. The SWCNT thin films (~250 nm) are prepared by a simple and cost effective method of spin-coating technology. Nanoindentation test with a Berkovich indenter is used to determine the hardness and elastic modulus of the SWCNT thin film. It is important to note that the elastic properties of SWCNT film are indirectly derived from the information of load and displacement of the indenter under certain assumptions, deviation of the 'test value' is inevitable. In this regard, uncertainty analysis is an effective process in guarantying the validity of the material properties. This paper carries out uncertainty estimation for the tested elastic properties of SWCNT film by nanoindentation. Experimental results and uncertainty analysis indicates that nanoindentation test could be an effective and reliable method in determine the elastic properties of SWCNT thin film. Moreover, the obtained values of hardness and elastic modulus can further benefit the design of SWCNT thin film based components.

Computing the Sensitivity Kernels for 2.5-D Seismic Waveform Inversion in Heterogeneous, Anisotropic Media

NASA Astrophysics Data System (ADS)

Zhou, Bing; Greenhalgh, S. A.

2011-10-01

2.5-D modeling and inversion techniques are much closer to reality than the simple and traditional 2-D seismic wave modeling and inversion. The sensitivity kernels required in full waveform seismic tomographic inversion are the Fréchet derivatives of the displacement vector with respect to the independent anisotropic model parameters of the subsurface. They give the sensitivity of the seismograms to changes in the model parameters. This paper applies two methods, called `the perturbation method' and `the matrix method', to derive the sensitivity kernels for 2.5-D seismic waveform inversion. We show that the two methods yield the same explicit expressions for the Fréchet derivatives using a constant-block model parameterization, and are available for both the line-source (2-D) and the point-source (2.5-D) cases. The method involves two Green's function vectors and their gradients, as well as the derivatives of the elastic modulus tensor with respect to the independent model parameters. The two Green's function vectors are the responses of the displacement vector to the two directed unit vectors located at the source and geophone positions, respectively; they can be generally obtained by numerical methods. The gradients of the Green's function vectors may be approximated in the same manner as the differential computations in the forward modeling. The derivatives of the elastic modulus tensor with respect to the independent model parameters can be obtained analytically, dependent on the class of medium anisotropy. Explicit expressions are given for two special cases—isotropic and tilted transversely isotropic (TTI) media. Numerical examples are given for the latter case, which involves five independent elastic moduli (or Thomsen parameters) plus one angle defining the symmetry axis.

Effects of self-healing microcapsules on bending performance in composite brake pads

NASA Astrophysics Data System (ADS)

Zhang, Li; Dong, Xiu-ping; Wang, Hui

2009-07-01

For the purpose of reducing self-weight, friction noise and cost, improving shock absorption, enhancing corrosion and wear resistance, brake pads made of composite materials with self-healing function are prepared to substitute metal ones by designing ingredients and applying optimized production technology. As self-healing capsules are chosen, new method with technology of self-healing microcapsules, dicyclpentadiene (DCPD) microcapsules coated with poly (urea-formaldehyde), is put forward in this paper. In the crack's extending process, the stress is concentrated at the crack end, where the microcapsule is designed to be located. When the stress goes through the microcapsules and causes them to break, the self-healing liquid runs out to fill the crack by the capillary and it will poly-react with catalyst in the composite. As a result, the crack is healed. In this paper, polymer matrix composite brake pads with 6 prescriptions are prepared and studied. Three-point bending tests are carried out according to standards in GB/T 3356-1999 and the elastic constants of these polymer matrix composites are obtained by experiments. In accordance with the law of the continuous fiber composite, elastic constants of the short-fiber composite can be calculated by proportions of each ingredient. Results show that the theoretical expected results and the experimental values are consistent. 0.3-1.2 % mass proportion of microcapsules has little effects on the composite's bending intensity and modulus of elasticity. These studies also show that self-healing microcapsules used in composite brake pads is feasible.

Acoustoelastic effect of textured (Ba,Sr)TiO{sub 3} thin films under an initial mechanical stress

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

Kamel, Marwa; Mseddi, Souhir; Njeh, Anouar

Acoustoelastic (AE) analysis of initial stresses plays an important role as a nondestructive tool in current engineering. Two textured BST (Ba{sub 0.65}Sr{sub 0.35}TiO{sub 3}) thin films, with different substrate to target distance, were grown on Pt(111)/TiO{sub 2}/SiO{sub 2}/Si(001) substrate by rf-magnetron sputtering deposition techniques. A conventional “sin{sup 2} ψ” method to determine residual stress and strain in BST films by X-ray diffraction is applied. A laser acoustic waves (LA-waves) technique is used to generate surface acoustic waves (SAW) propagating in both samples. Young's modulus E and Poisson ratio ν of BST films in different propagation directions are derived from the measuredmore » dispersion curves. Estimation of effective second-order elastic constants of BST thin films in stressed states is served in SAW study. This paper presents an original investigation of AE effect in prestressed Ba{sub 0.65}Sr{sub 0.35}TiO{sub 3} films, where the effective elastic constants and the effect of texture on second and third order elastic tensor are considered and used. The propagation behavior of Rayleigh and Love waves in BST thin films under residual stress is explored and discussed. The guiding velocities affected by residual stresses, reveal some shifts which do not exceed four percent mainly in the low frequency range.« less

Mechanical, electronic and thermodynamic properties of full Heusler compounds Fe2VX(X = Al, Ga)

NASA Astrophysics Data System (ADS)

Khalfa, M.; Khachai, H.; Chiker, F.; Baki, N.; Bougherara, K.; Yakoubi, A.; Murtaza, G.; Harmel, M.; Abu-Jafar, M. S.; Omran, S. Bin; Khenata, R.

2015-11-01

The electronic structure, mechanical and thermodynamic properties of Fe2VX, (with X = Al and Ga), have been studied self consistently by employing state-of-the-art full-potential linearized approach of augmented plane wave plus local orbitals (FP-LAPW + lo) method. The exchange-correlation potential is treated with the local density and generalized gradient approximations (LDA and GGA). Our predicted ground state properties such as lattice constants, bulk modulus and elastic constants appear more accurate when we employed the GGA rather than the LDA, and these results are in very good agreement with the available experimental and theoretical data. Further, thermodynamic properties of Fe2VAl and Fe2VGa are predicted with pressure and temperature in the ranges of 0-40 GPa and 0-1500 K using the quasi-harmonic Debye model. We have obtained successfully the variations of the heat capacities, primitive cell volume and volume expansion coefficient.

Effects of Vacancy Concentration and Temperature on Mechanical Properties of Single-Crystal γ-TiAl Based on Molecular Dynamics Simulation

NASA Astrophysics Data System (ADS)

Ruicheng, Feng; Hui, Cao; Haiyan, Li; Zhiyuan, Rui; Changfeng, Yan

2018-01-01

Molecular dynamics simulation is used to analyze tensile strength and elastic modulus under different temperatures and vacancy concentrations. The effects of temperature and vacancy concentration on the mechanical properties of γ-TiAl alloy are investigated. The results show that the ultimate stress, ultimate strain and elastic modulus decrease nonlinearly with increasing temperature and vacancy concentration. As the temperature increases, the plastic of material is reinforced. The influence of temperature on strength and elastic modulus is larger than that of vacancy concentration. The evolution process of vacancy could be observed clearly. Furthermore, vacancies with different concentrations develop into voids first as a function of external forces or other factors, micro cracks evolve from those voids, those micro cracks then converge to a macro crack, and fracture will finally occur. The vacancy evolution process cannot be observed clearly owing to the thermal motion of atoms at high temperature. In addition, potential energy is affected by both temperature and vacancy concentration.

Nanoindentation study of bulk zirconium hydrides at elevated temperatures

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

Cinbiz, Mahmut Nedim; Balooch, Mehdi; Hu, Xunxiang

Here, the mechanical properties of zirconium hydrides was studied using nano-indentation technique at a temperature range of 25 – 400 °C. Temperature dependency of reduced elastic modulus and hardness of δ- and ε-zirconium hydrides were obtained by conducting nanoindentation experiments on the bulk hydride samples with independently heating capability of indenter and heating stage. The reduced elastic modulus of δ-zirconium hydride (H/Zr ratio =1.61) decreased from ~113 GPa to ~109 GPa while temperature increased from room temperature to 400°C. For ε-zirconium hydrides (H/Zr ratio=1.79), the reduced elastic modulus decreased from 61 GPa to 54 GPa as temperature increased from roommore » temperature to 300 °C. Whereas, hardness of δ-zirconium hydride significantly decreased from 4.1 GPa to 2.41 GPa when temperature increased from room temperature to 400 °C. Similarly, hardness of ε-zirconium hydride decreased from 3.06 GPa to 2.19 GPa with temperature increase from room temperature to 300°C.« less

Nanoindentation study of bulk zirconium hydrides at elevated temperatures

DOE PAGES

Cinbiz, Mahmut Nedim; Balooch, Mehdi; Hu, Xunxiang; ...

2017-08-02

Here, the mechanical properties of zirconium hydrides was studied using nano-indentation technique at a temperature range of 25 – 400 °C. Temperature dependency of reduced elastic modulus and hardness of δ- and ε-zirconium hydrides were obtained by conducting nanoindentation experiments on the bulk hydride samples with independently heating capability of indenter and heating stage. The reduced elastic modulus of δ-zirconium hydride (H/Zr ratio =1.61) decreased from ~113 GPa to ~109 GPa while temperature increased from room temperature to 400°C. For ε-zirconium hydrides (H/Zr ratio=1.79), the reduced elastic modulus decreased from 61 GPa to 54 GPa as temperature increased from roommore » temperature to 300 °C. Whereas, hardness of δ-zirconium hydride significantly decreased from 4.1 GPa to 2.41 GPa when temperature increased from room temperature to 400 °C. Similarly, hardness of ε-zirconium hydride decreased from 3.06 GPa to 2.19 GPa with temperature increase from room temperature to 300°C.« less

Fracture Toughness and Elastic Modulus of Epoxy-Based Nanocomposites with Dopamine-Modified Nano-Fillers

PubMed Central

Koh, Kwang Liang; Ji, Xianbai; Lu, Xuehong; Lau, Soo Khim; Chen, Zhong

2017-01-01

This paper examines the effect of surface treatment and filler shape factor on the fracture toughness and elastic modulus of epoxy-based nanocomposite. Two forms of nanofillers, polydopamine-coated montmorillonite clay (D-clay) and polydopamine-coated carbon nanofibres (D-CNF) were investigated. It was found that Young’s modulus increases with increasing D-clay and D-CNF loading. However, the fracture toughness decreases with increased D-clay loading but increases with increased D-CNF loading. Explanations have been provided with the aid of fractographic analysis using electron microscope observations of the crack-filler interactions. Fractographic analysis suggests that although polydopamine provides a strong adhesion between the fillers and the matrix, leading to enhanced elastic stiffness, the enhancement prohibits energy release via secondary cracking, resulting in a decrease in fracture toughness. In contrast, 1D fibre is effective in increasing the energy dissipation during fracture through crack deflection, fibre debonding, fibre break, and pull-out. PMID:28773136

Elasticity and anelasticity of microcrystalline aluminum samples having various deformation and thermal histories

NASA Astrophysics Data System (ADS)

Betekhtin, V. I.; Kadomtsev, A. G.; Kardashev, B. K.

2006-08-01

The effect of the amplitude of vibrational deformation on the elastic modulus and internal friction of microcrystalline aluminum samples produced by equal-channel angular pressing was studied. The samples have various deformation and thermal histories. The elastic and inelastic (microplastic) properties of the samples are investigated. As the degree of plastic deformation increases, the Young’s modulus E, the amplitude-independent decrement δi, and the microplastic flow stress σ increase. As the annealing temperature increases, the quantities δi and σ decrease noticeably and the modulus E exhibits a more complex behavior. The experimental data are discussed under the assumption that the dislocation mobility depends on both the spectrum of point defects and the internal stresses, whose level is determined by the degree of plastic deformation and the temperature of subsequent annealing. The concept of internal stresses is also used to analyze the data on the effect of the degree of deformation and annealing on the rupture strength of the samples.

Elasticity-dependent fast underwater adhesion demonstrated by macroscopic supramolecular assembly.

PubMed

Ju, Guannan; Cheng, Mengjiao; Guo, Fengli; Zhang, Qian; Shi, Feng

2018-05-30

Macroscopic supramolecular assembly (MSA) is a recent progress in supramolecular chemistry to associate visible building blocks through non-covalent interactions in a multivalent manner. Although various substrates (e. g. hydrogels, rigid materials) have been used, a general design rule of building blocks in MSA systems and interpretation of the assembly mechanism are still lacking and urgently in demand. Here we design three model systems with varied modulus and correlated the MSA probability with the elasticity. Based on the effects of substrate deformability on multivalency, we have proposed an elastic-modulus-dependent rule that building blocks below a critical modulus of 2.5 MPa can achieve MSA for the used host/guest system. Moreover, this MSA rule applies well to the design of materials applicable for fast underwater adhesion: Soft substrates (0.5 MPa) can achieve underwater adhesion within 10 s with one magnitude higher strength than that of rigid substrates (2.5 MPa). © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

The effect of boron concentration on the structure and elastic properties of Ru-Ir alloys: first-principles calculations

NASA Astrophysics Data System (ADS)

Li, Xiaolong; Zhou, Zhaobo; Hu, Riming; Zhou, Xiaolong; Yu, Jie; Liu, Manmen

2018-04-01

The Phase stability, electronic structure, elastic properties and hardness of Ru-Ir alloys with different B concentration were investigated by first principles calculations. The calculated formation enthaplies and cohesive energies show that these compounds are all thermodynamically stable. Information on electronic structure indicates that they possess metallic characteristic and Ru-Ir-B alloys were composed of the Ru-B and Ir-B covalent bond. The elastic properties were calculated, which included bulk modulus, shear modulus, Young’s modulus, Poisson’s ratio and hardness. The calculated results reveal that the plastic of Ru-Ir-B alloys increase with the increase of the content of B atoms, but the hardness of Ru-Ir-B alloys have no substantial progress with the increase of the content of B atoms. However, it is interesting that the hardness of the Ru-Ir-B compound was improved obviously as the B content was higher than 18 atoms because of a phase structure transition.

Geometrical and material parameters to assess the macroscopic mechanical behaviour of fresh cranial bone samples.

PubMed

Auperrin, Audrey; Delille, Rémi; Lesueur, Denis; Bruyère, Karine; Masson, Catherine; Drazétic, Pascal

2014-03-21

The present study aims at providing quantitative data for the personalisation of geometrical and mechanical characteristics of the adult cranial bone to be applied to head FE models. A set of 351 cranial bone samples, harvested from 21 human skulls, were submitted to three-point bending tests at 10 mm/min. For each of them, an apparent elastic modulus was calculated using the beam's theory and a density-dependant beam inertia. Thicknesses, apparent densities and percentage of ash weight were also measured. Distributions of characteristics among the different skull bones show their symmetry and their significant differences between skull areas. A data analysis was performed to analyse potential relationship between thicknesses, densities and the apparent elastic modulus. A specific regression was pointed out to estimate apparent elastic modulus from the product of thickness by apparent density. These results offer quantitative tools in view of personalising head FE models and thus improve definition of local injury criteria for this body part. Copyright © 2014 Elsevier Ltd. All rights reserved.

Elastic properties and mechanical stability of chiral and filled viral capsids

NASA Astrophysics Data System (ADS)

Buenemann, Mathias; Lenz, Peter

2008-11-01

The elasticity and mechanical stability of empty and filled viral capsids under external force loading are studied in a combined analytical and numerical approach. We analyze the influence of capsid structure and chirality on the mechanical properties. We find that generally skew shells have lower stretching energy. For large Föppl-von Kármán numbers γ (γ≈105) , skew structures are stiffer in their elastic response than nonchiral ones. The discrete structure of the capsules not only leads to buckling for large γ but also influences the breakage behavior of capsules below the buckling threshold: the rupture force shows a γ1/4 scaling rather than a γ1/2 scaling as expected from our analytical results for continuous shells. Filled viral capsids are exposed to internal anisotropic pressure distributions arising from regularly packaged DNA coils. We analyze their influence on the elastic properties and rupture behavior and we discuss possible experimental consequences. Finally, we numerically investigate specific sets of parameters corresponding to specific phages such as ϕ29 and cowpea chlorotic mottle virus (CCMV). From the experimentally measured spring constants we make predictions about specific material parameters (such as bending rigidity and Young’s modulus) for both empty and filled capsids.

Yttrium aluminium garnet under pressure: Structural, elastic, and vibrational properties from ab initio studies

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

Monteseguro, V.; Rodríguez-Hernández, P.; Muñoz, A., E-mail: amunoz@ull.es

The structural, elastic, and vibrational properties of yttrium aluminum garnet Y{sub 3}Al{sub 5}O{sub 12} are studied under high pressure by ab initio calculations in the framework of the density functional theory. The calculated ground state properties are in good agreement with the available experimental data. Pressure dependences of bond length and bulk moduli of the constituent polyhedra are reported. The evolution of the elastic constants and the major elastic properties, Young and shear modulus, Poisson's ratios, and Zener anisotropy ratio, are described. The mechanical stability is analyzed, on the light of “Born generalized stability criteria,” showing that the garnet ismore » mechanically unstable above 116 GPa. Symmetries, frequencies, and pressure coefficients of the Raman-active modes are discussed on the basis of the calculated total and partial phonon density of states, which reflect the dynamical contribution of each atom. The relations between the phonon modes of Y{sub 3}Al{sub 5}O{sub 12} and the internal and external molecular modes of the different polyhedra are discussed. Infrared-active modes, as well as the silent modes, and their pressure dependence are also investigated. No dynamical instabilities were found below 116 GPa.« less

First-principles calculations of the structural, elastic and thermodynamic properties of mackinawite (FeS) and pyrite (FeS2)

NASA Astrophysics Data System (ADS)

Wen, Xiangli; Liang, Yuxuan; Bai, Pengpeng; Luo, Bingwei; Fang, Teng; Yue, Luo; An, Teng; Song, Weiyu; Zheng, Shuqi

2017-11-01

The thermodynamic properties of Fe-S compounds with different crystal structure are very different. In this study, the structural, elastic and thermodynamic properties of mackinawite (FeS) and pyrite (FeS2) were investigated by first-principles calculations. Examination of the electronic density of states shows that mackinawite (FeS) is metallic and that pyrite (FeS2) is a semiconductor with a band gap of Eg = 1.02 eV. Using the stress-strain method, the elastic properties including the bulk modulus and shear modulus were derived from the elastic Cij data. Density functional perturbation theory (DFPT) calculations within the quasi-harmonic approximation (QHA) were used to calculate the thermodynamic properties, and the two Fe-S compounds are found to be dynamically stable. The isothermal bulk modulus, thermal expansion coefficient, heat capacities, Gibbs free energy and entropy of the Fe-S compounds are obtained by first-principles phonon calculations. Furthermore, the temperature of the mackinawite (FeS) ⟶ pyrite (FeS2) phase transition at 0 GPa was predicted. Based on the calculation results, the model for prediction of Fe-S compounds in the Fe-H2S-H2O system was improved.

Tolerance to structural disorder and tunable mechanical behavior in self-assembled superlattices of polymer-grafted nanocrystals

DOE PAGES

Gu, X. Wendy; Ye, Xingchen; Koshy, David M.; ...

2017-02-27

Large, freestanding membranes with remarkably high elastic modulus ( > 10 GPa) have been fabricated through the self-Assembly of ligand-stabilized inorganic nanocrystals, even though these nanocrystals are connected only by soft organic ligands (e.g., dodecanethiol or DNA) that are not cross-linked or entangled. Recent developments in the synthesis of polymer-grafted nanocrystals have greatly expanded the library of accessible superlattice architectures,which allows superlattice mechanical behavior to be linked to specific structural features. Here, colloidal self-Assembly is used to organize polystyrene-grafted Au nanocrystals at a fluid interface to form ordered solids with sub-10-nm periodic features. We used thin-film buckling and nanoindentation tomore » evaluate the mechanical behavior of polymer-grafted nanocrystal superlattices while exploring the role of polymer structural conformation, nanocrystal packing, and superlattice dimensions. Superlattices containing 3-20 vol % Au are found to have an elastic modulus of ~6-19 GPa, and hardness of ~120-170 MPa. We also found that rapidly self-Assembled superlattices have the highest elastic modulus, despite containing significant structural defects. Polymer extension, interdigitation, and grafting density are determined to be critical parameters that govern superlattice elastic and plastic deformation.« less

The effects of a 4-week static stretching programme on the individual muscles comprising the hamstrings.

PubMed

Ichihashi, Noriaki; Umegaki, Hiroki; Ikezoe, Tome; Nakamura, Masatoshi; Nishishita, Satoru; Fujita, Kosuke; Umehara, Jun; Nakao, Sayaka; Ibuki, Satoko

2016-12-01

The aims of this study were to investigate the effects of a 4-week intervention of static stretching (SS) on muscle hardness of the semitendinosus (ST), semimembranosus (SM) and biceps femoris (BF) muscles. Shear elastic modulus was measured by using ultrasound shear wave elastography as the index of muscle hardness. Thirty healthy men (age 22.7 ± 2.2 years) volunteered for this study and were randomly assigned to the SS intervention group (n = 15) or the control group (n = 15). Participants in the SS intervention group received a 4-week stretch intervention for the hamstrings of their dominant leg. Shear elastic moduli of the hamstrings were measured at initial evaluation and after 4 weeks in both groups at a determined angle. In all muscles, the shear elastic modulus decreased significantly after SS intervention. The percentage change in the shear elastic modulus from the value at initial evaluation to after 4 weeks intervention was greatest in the SM. These results suggest that SS intervention has chronic effects on reducing hardness of the hamstring muscle components, especially the SM muscle.

Optimizing signal output: effects of viscoelasticity and difference frequency on vibroacoustic radiation of tissue-mimicking phantoms

NASA Astrophysics Data System (ADS)

Namiri, Nikan K.; Maccabi, Ashkan; Bajwa, Neha; Badran, Karam W.; Taylor, Zachary D.; St. John, Maie A.; Grundfest, Warren S.; Saddik, George N.

2018-02-01

Vibroacoustography (VA) is an imaging technology that utilizes the acoustic response of tissues to a localized, low frequency radiation force to generate a spatially resolved, high contrast image. Previous studies have demonstrated the utility of VA for tissue identification and margin delineation in cancer tissues. However, the relationship between specimen viscoelasticity and vibroacoustic emission remains to be fully quantified. This work utilizes the effects of variable acoustic wave profiles on unique tissue-mimicking phantoms (TMPs) to maximize VA signal power according to tissue mechanical properties, particularly elasticity. A micro-indentation method was utilized to provide measurements of the elastic modulus for each biological replica. An inverse relationship was found between elastic modulus (E) and VA signal amplitude among homogeneous TMPs. Additionally, the difference frequency (Δf ) required to reach maximum VA signal correlated with specimen elastic modulus. Peak signal diminished with increasing Δf among the polyvinyl alcohol specimen, suggesting an inefficient vibroacoustic response by the specimen beyond a threshold of resonant Δf. Comparison of these measurements may provide additional information to improve tissue modeling, system characterization, as well as insights into the unique tissue composition of tumors in head and neck cancer patients.

Elastic properties, reaction kinetics, and structural relaxation of an epoxy resin polymer during cure

NASA Astrophysics Data System (ADS)

Heili, Manon; Bielawski, Andrew; Kieffer, John

The cure kinetics of a DGEBA/DETA epoxy is investigated using concurrent Raman and Brillouin light scattering. Raman scattering allows us to monitor the in-situ reaction and quantitatively assess the degree of cure. Brillouin scattering yields the elastic properties of the system, providing a measure of network connectivity. We show that the adiabatic modulus evolves non-uniquely as a function of cure degree, depending on the cure temperature and the molar ratio of the epoxy. Two mechanisms contribute to the increase in the elastic modulus of the material during curing. First, there is the formation of covalent bonds in the network during the curing process. Second, following bond formation, the epoxy undergoes structural relaxation toward an optimally packed network configuration, enhancing non-bonded interactions. We investigate to what extent the non-bonded interaction contribution to structural rigidity in cross-linked polymers is reversible, and to what extent it corresponds to the difference between adiabatic and isothermal moduli obtained from static tensile, i.e. the so-called relaxational modulus. To this end, we simultaneously measure the adiabatic and isothermal elastic moduli as a function of applied strain and deformation rate.

Tolerance to structural disorder and tunable mechanical behavior in self-assembled superlattices of polymer-grafted nanocrystals

NASA Astrophysics Data System (ADS)

Gu, X. Wendy; Ye, Xingchen; Koshy, David M.; Vachhani, Shraddha; Hosemann, Peter; Alivisatos, A. Paul

2017-03-01

Large, freestanding membranes with remarkably high elastic modulus (>10 GPa) have been fabricated through the self-assembly of ligand-stabilized inorganic nanocrystals, even though these nanocrystals are connected only by soft organic ligands (e.g., dodecanethiol or DNA) that are not cross-linked or entangled. Recent developments in the synthesis of polymer-grafted nanocrystals have greatly expanded the library of accessible superlattice architectures, which allows superlattice mechanical behavior to be linked to specific structural features. Here, colloidal self-assembly is used to organize polystyrene-grafted Au nanocrystals at a fluid interface to form ordered solids with sub-10-nm periodic features. Thin-film buckling and nanoindentation are used to evaluate the mechanical behavior of polymer-grafted nanocrystal superlattices while exploring the role of polymer structural conformation, nanocrystal packing, and superlattice dimensions. Superlattices containing 3-20 vol % Au are found to have an elastic modulus of ˜6-19 GPa, and hardness of ˜120-170 MPa. We find that rapidly self-assembled superlattices have the highest elastic modulus, despite containing significant structural defects. Polymer extension, interdigitation, and grafting density are determined to be critical parameters that govern superlattice elastic and plastic deformation.

Base course resilient modulus for the mechanistic-empirical pavement design guide : [summary].

DOT National Transportation Integrated Search

2011-01-01

Elastic modulus determination is often used in designing pavements and evaluating pavement performance. The Mechanistic-Empirical Pavement Design Guide (MEPDG) has become an important source of guidance for pavement design and rehabilitation. MEPDG r...

Method of measuring material properties of rock in the wall of a borehole

DOEpatents

Overmier, David K.

1985-01-01

To measure the modulus of elasticity of the rock in the wall of a borehole, a plug is cut in the borehole wall. The plug, its base attached to the surrounding rock, acts as a short column in response to applied forces. A loading piston is applied to the top of the plug and compression of the plug is measured as load is increased. Measurement of piston load and plug longitudinal deformation are made to determine the elastic modulus of the plug material. Poisson's ratio can be determined by simultaneous measurements of longitudinal and lateral deformation of the plug in response to loading. To determine shear modulus, the top of the plug is twisted while measurements are taken of torsional deformation.

Method of measuring material properties of rock in the wall of a borehole

DOEpatents

Overmier, D.K.

1984-01-01

To measure the modulus of elasticity of the rock in the wall of a borehole, a plug is cut in the borehole wall. The plug, its base attached to the surrounding rock, acts as a short column in response to applied forces. A loading piston is applied to the top of the plug and compression of the plug is measured as load is increased. Measurements of piston load and plug longitudinal deformation are made to determine the elastic modulus of the plug material. Poisson's ratio can be determined by simultaneous measurements of longitudinal and lateral deformation of the plug in response to loading. To determine shear modulus, the top of the plug is twisted while measurements are taken of torsional deformation.

Young's modulus and internal friction of the SiC/Si biomorphic composite based on the sapele wood precursor

NASA Astrophysics Data System (ADS)

Kardashev, B. K.; Orlova, T. S.; Smirnov, B. I.; de Arellano-Lopez, A. R.; Martinez-Fernandez, J.

2009-04-01

The effect of the vibrational strain amplitude on the Young’s modulus and ultrasound absorption (internal friction) of a SiC/Si biomorphic composite prepared by pyrolysis of sapele wood followed by infiltration of silicon were investigated. The studies were conducted in air and in vacuum by the acoustic resonance method with the use of a composite vibrator in longitudinal vibrations at frequencies of about 100 kHz. Measurements performed on sapele wood-based bio-SiC/Si samples revealed a substantial effect of adsorption-desorption of molecules contained in air on the effective elasticity modulus and elastic vibration decrement. Microplastic characteristics of the SiC/Si composites prepared from wood of different tree species were compared.

Readily fiberizable glasses having a high modulus of elasticity

NASA Technical Reports Server (NTRS)

Bacon, J. F.

1970-01-01

New glass compositions yield composites having higher moduli of elasticity and specific moduli of elasticity than commercially available glasses. Over a reasonable temperature range the glasses have a viscosity of about 20,000 poises. They consist of silica, alumina, magnesia, and beryllia, plus at least one uncommon oxide.

Low Velocity Sphere Impact of a Soda Lime Silicate Glass

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

Wereszczak, Andrew A; Fox, Ethan E; Morrissey, Timothy G

2011-10-01

This report summarizes TARDEC-sponsored work at Oak Ridge National Laboratory (ORNL) during the FY11 involving low velocity (< 30 m/s or < 65 mph) ball impact testing of Starphire soda lime silicate glass. The intent was to better understand low velocity impact response in the Starphire for sphere densities that bracketed that of rock. Five sphere materials were used: borosilicate glass, soda-lime silicate glass, steel, silicon nitride, and alumina. A gas gun was fabricated to produce controlled velocity delivery of the spheres against Starphire tile targets. Minimum impact velocities to initiate fracture in the Starphire were measured and interpreted inmore » context to the kinetic energy of impact and the elastic property mismatch between the any of the five sphere-Starphire-target combinations. The primary observations from this low velocity (< 30 m/s or < 65 mph) testing were: (1) Frictional effects contribute to fracture initiation. (2) Spheres with a lower elastic modulus require less force to initiate fracture in the Starphire than spheres with a higher elastic modulus. (3) Contact-induced fracture did not initiate in the Starphire SLS for impact kinetic energies < 150 mJ. Fracture sometimes initiated or kinetic energies between {approx} 150-1100 mJ; however, it tended to occur when lower elastic modulus spheres were impacting it. Contact-induced fracture would always occur for impact energies > 1100 mJ. (4) The force necessary to initiate contact-induced fracture is higher under dynamic or impact conditions than it is under quasi-static indentation conditions. (5) Among the five used sphere materials, silicon nitride was the closest match to 'rock' in terms of both density and (probably) elastic modulus.« less

Gelling ability of kefiran in the presence of sucrose and fructose and physicochemical characterization of the resulting cryogels.

PubMed

Zavala, Lucía; Roberti, Paula; Piermaria, Judith A; Abraham, Analía G

2015-08-01

In this work, the influence of sucrose and fructose on the gel-forming capacity of kefiran was investigated as well as the physicochemical characteristics of the resulting gels. The addition of sugar to gel-forming solutions did not alter the pseudoplastic flow properties of kefiran solutions and after one freeze-thaw cycle translucent gels with high water-holding capability were obtained. A highly porous matrix was revealed by microscopy whose pore size varied with sugar concentration. Sucrose and fructose had different effects on the rheological characteristics of sugar-kefiran gels. An increment in the strength of the gels with progressive concentrations of sucrose was evidenced by an increase in the elastic modulus (G'), indicating that sucrose reinforces the binding interactions between the polymer molecules (p ≤ 0.05). A drastic reduction in elastic modulus occurred, however, when 50.0 % w/w sucrose was added to kefiran gels, resulting in less elasticity. In contrast, when fructose was added to kefiran gels, elastic modulus decreased slightly with progressive sugar concentrations up to 10 %, thereafter increasing up to 50 % (p ≤ 0.05). Supplementation with up to 30 % sugar contributed to water retention and increased the viscous modulus. The relative increment in the elastic and viscous moduli elevated the loss tangent (tanδ) depending on the type and concentration of sugar. Sugars (sucrose, fructose) present in the matrix of the polysaccharide networks modified water-polymer and polymer-polymer interactions and consequently changed the gels' physicochemical characteristics, thus allowing the possibility of selecting the appropriate formulation through tailor-made kefiran cryogels.

Biomechanics of isolated tomato (Solanum lycopersicum L.) fruit cuticles: the role of the cutin matrix and polysaccharides.

PubMed

López-Casado, Gloria; Matas, Antonio J; Domínguez, Eva; Cuartero, Jesús; Heredia, Antonio

2007-01-01

The mechanical characteristics of the cuticular membrane (CM), a complex composite biopolymer basically composed of a cutin matrix, waxes, and hydrolysable polysaccharides, have been described previously. The biomechanical behaviour and quantitative contribution of cutin and polysaccharides have been investigated here using as experimental material mature green and red ripe tomato fruits. Treatment of isolated CM with anhydrous hydrogen fluoride in pyridine allowed the selective elimination of polysaccharides attached to or incrusted into the cutin matrix. Cutin samples showed a drastic decrease in elastic modulus and stiffness (up to 92%) compared with CM, which clearly indicates that polysaccharides incorporated into the cutin matrix are responsible for the elastic modulus, stiffness, and the linear elastic behaviour of the whole cuticle. Reciprocally, the viscoelastic behaviour of CM (low elastic modulus and high strain values) can be assigned to the cutin. These results applied both to mature green and red ripe CM. Cutin elastic modulus, independently of the degree of temperature and hydration, was always significantly higher for the ripe than for the green samples while strain was lower; the amount of phenolics in the cutin network are the main candidates to explain the increased rigidity from mature green to red ripe cutin. The polysaccharide families isolated from CM were pectin, hemicellulose, and cellulose, the main polymers associated with the plant cell wall. The three types of polysaccharides were present in similar amounts in CM from mature green and red ripe tomatoes. Physical techniques such as X-ray diffraction and Raman spectroscopy indicated that the polysaccharide fibres were mainly randomly oriented. A tomato fruit CM scenario at the supramolecular level that could explain the observed CM biomechanical properties is presented and discussed.

Fabrication and characterization of carbon nanotube turfs

NASA Astrophysics Data System (ADS)

Qiu, Anqi

Carbon nanotube turfs are vertically aligned, slightly tortuous and entangled functional nanomaterials that exhibit high thermal and electrical properties. CNT turfs exhibit unique combinations of thermal and electrical conductivity, energy absorbing capability, low density and adhesive behavior. The objective of this study is to fabricate, measure, manipulate and characterize CNT turfs and thus determine the relationship between a turf's properties and its morphology, and provide guidance for developing links between turf growth conditions and of the subsequent turf properties. Nanoindentation was utilized to determine the mechanical and in situ electrical properties of CNT turfs. Elastic properties do not vary significantly laterally within a single turf, quantifying for the first time the ability to treat the turf as a mechanical continuum throughout. The use of the average mechanical properties for any given turf should be suitable for design purpose without the necessity of accounting for lateral spatial variation in structure. Properties variation based on time dependency, rate dependency, adhesive behavior and energy absorption and dissipation behavior have been investigated for these CNT turfs. Electrical properties measurements of CNT turfs have been carried out and show that a constant electrical current at a constant penetration depth indicates that a constant number of CNTs in contact with the tip; combining with the results that adhesive load increased with an increasing penetration hold time, thus we conclude that during a hold period of nanoindentation, individual tubes increase their individual attachment to the tip. CNT turfs show decreased adhesion and modulus after exposure to an electron beam due to carbon deposition and subsequent oxidation. To increase the modulus of the turf, axial compression and solvent capillary were used to increase the density of the turf by up to 15 times. Structure-property relationships were determined from the density and tortuosity measurements carried out through in situ electrical measurements and directionality measurements. Increasing density increases the mechanical properties as well as electrical conductivity. The modulus increased with a lower tortuosity, which may be related to the compressive buckling positioning.

Study on rheological properties of CMC/Eu-Tb solutions with different concentrations

NASA Astrophysics Data System (ADS)

Fu, Z. C.; Ye, J.; Xiong, J.

2018-05-01

The rheological properties of polymer solution are sensitive to variations in the polymer structure. Carboxymethyl cellulose (CMC) aqueous solution has been used in many fields, such as food, medicine and paper industry. In this paper, the effects of different concentrations (2% - 6%) of CMC/Eu-Tb on their rheological properties were investigeted, including steady-state flow and viscoelastic response. The results show that, the viscosity of CMC/Eu-Tb is lower than that of CMC, at the same concentrations; the products solutions present a nearly Newtonian behavior at the low concentrations (2% - 3%); while at the higher concentrations (4% - 6%), the products solutions present a pseudoplastic behavior; shear-thinning behavior is due to the polymer chains unravel under the action of flow and the molecular chains are oriented in the flow direction. The results also show that the viscosity of the solutions decreases with increasing temperature. Dynamic rheological tests show that CMC/Eu-Tb has viscoelasticity in the concentrations of 2% - 6%. At lower concentrations, the elastic modulus G‧ is slightly higher than the viscous modulus G″, and as the concentrations increase, the elastic modulus G‧ is significantly higher than the viscous modulus G″. It means that at the lower solution concentrations, the solutions tend to be less elastic and easier to flow. Most of the energies are lost through the viscous flow. As the solution concentrations increase, the solutions tend to be more elastic, and the system tends to form a gel.

Examining platelet-fibrin interactions during traumatic shock in a swine model using platelet contractile force and clot elastic modulus.

PubMed

White, Nathan J; Martin, Erika J; Brophy, Donald F; Ward, Kevin R

2011-07-01

A significant proportion of severely injured patients develop early coagulopathy, characterized by abnormal clot formation, which impairs resuscitation and increases mortality. We have previously demonstrated an isolated decrease in clot strength by thrombelastography in a swine model of nonresuscitated traumatic shock. In order to more closely examine platelet-fibrin interactions in this setting, we define the observed decrease in clot strength in terms of platelet-induced clot contraction and clot elastic modulus using the Hemostasis Analysis System (HAS) (Hemodyne Inc., Richmond, Virginia, USA). Whole blood was sampled for HAS measurements, metabolic measurements, cell counts, and fibrinogen concentration at baseline prior to injury and again at a predetermined level of traumatic shock defined by oxygen debt. Male swine (N=17) received femur fracture and controlled arterial hemorrhage to achieve an oxygen debt of 80 ml/kg. Platelet counts were unchanged, but fibrinogen concentration was reduced significantly during shock (167.6 vs. 66.7 mg/dl, P=0.0007). Platelet contractile force generated during clot formation did not change during shock (11.7 vs. 10.4 kdynes, P=0.41), but clot elastic modulus was dynamically altered, resulting in a lower final value (22.9 vs. 17.3 kdynes/cm, P<0.0001). In this model of traumatic shock, platelet function was preserved, whereas terminal clot elastic modulus was reduced during shock in a manner most consistent with early changes in the mechanical properties of the developing fibrin fiber network.

The changes of red blood cell viscoelasticity and sports anemia in male 24-hr ultra-marathoners.

PubMed

Liu, Che-Hung; Tseng, Yen-Fang; Lai, Jiun-I; Chen, Yin-Quan; Wang, Shih-Hao; Kao, Wei-Fong; Li, Li-Hua; Chiu, Yu-Hui; How, Chorng-Kuang; Chang, Wen-Han

2018-05-01

In endurance sports, stress, dehydration and release of chemical factors have been associated with red blood cell (RBC) alterations of structure and function, which may contribute to sports anemia, a well-observed phenomenon during long-distance running. Until now, the investigation of the changes of viscoelastic properties of RBC membrane, a decisive factor of RBC deformability to avoid hemolysis, is lacking, especially in an Oriental population. nineteen runners were prospectively recruited into our study. Hematological parameters were analyzed before and immediately after the 2015 Taipei 24H Ultra-Marathon Festival, Taiwan. Video particle tracking microrheology was used to determine viscoelastic properties of each RBC sample by calculating the dynamic elastic modulus G'(f) and the viscous modulus G″(f) at frequency f = 20 Hz. Haptoglobin, RBC count, hemoglobin, hematocrit, mean cell hemoglobin, plasma free hemoglobin and unsaturated iron-binding capacity values of the recruited runners showed a statistically significant drop in the post-race values. Blood concentration of reticulocyte and ferritin were significantly higher at post-race compared with pre-race. 15 out of the 19 runners had a concurrent change in the elastic and the viscous moduli of their RBCs. Changes in the elastic and the viscous moduli were correlated with changes in the RBC count, hemoglobin and hematocrit. Viscoelasticity properties, the elastic modulus G'(f) and the viscous modulus G″(f) of RBCs are associated with endurance exercise-induced anemia. Copyright © 2017. Published by Elsevier Taiwan LLC.

Biomimicry in biomedical research

PubMed Central

Zhang, Ge

2012-01-01

Biomimicry (literally defined as the imitation of life or nature) has sparked a variety of human innovations and inspired countless cutting-edge designs. From spider silk-made artificial skin to lotus leaf-inspired self-cleaning materials, biomimicry endeavors to solve human problems. Biomimetic approaches have contributed significantly to advances biomedical research during recent years. Using polyacrylamide gels to mimic the elastic modulus of different biological tissues, Disher’s lab has directed meschymal stem cell differentiation into specific lineages.1 They have shown that soft substrates mimicking the elastic modulus of brain tissues (0.1~1 kPa) were neurogenic, substrates of intermediate elastic modulus mimicking muscle (8 ~17 kPa) were myogenic, and substrates with bone-like elastic modulus (25~40 kPa) were osteogenic. This work represents a novel way to regulate the fate of stem cells and exerts profound influence on stem cell research. Biomimcry also drives improvements in tissue engineering. Novel scaffolds have been designed to capture extracellular matrix-like structures, binding of ligands, sustained release of cytokines, and mechanical properties intrinsic to specific tissues for tissue engineering applications.2,3 For example, tissue engineering skin grafts have been designed to mimic the cell composition and layered structure of native skin.4 Similarly, in the field of regenerative medicine, researchers aim to create biomimetic scaffolds to mimic the properties of a native stem cell environment (niche) to dynamically interact with the entrapped stem cells and direct their response.5 PMID:23275257

Effect of pressure variation on structural, elastic, mechanical, optoelectronic and thermodynamic properties of SrNaF3 fluoroperovskite

NASA Astrophysics Data System (ADS)

Erum, Nazia; Azhar Iqbal, Muhammad

2017-12-01

The effect of pressure variation on structural, electronic, elastic, mechanical, optical and thermodynamic characteristics of cubic SrNaF3 fluoroperovskite have been investigated by employing first-principles method within the framework of gradient approximation (GGA). For the total energy calculations, we have used the full-potential linearized augmented plane wave (FP-LAPW) method. Thermodynamic properties are computed in terms of quasi-harmonic Debye model. The pressure effects are determined in the range of 0-25 GPa, in which mechanical stability of SrNaF3 fluoroperovskite remains valid. A prominent decrease in lattice constant and bonds length is observed with the increase in pressure from 0 to 25 GPa. The effect of increase in pressure on band structure calculations with GGA and GGA plus Tran-Blaha modified Becke-Johnson (TB-mBJ) potential reveals a predominant characteristic associated with widening of bandgap. The influence of pressure on set of isotropic elastic parameters and their related properties are numerically estimated for SrNaF3 polycrystalline aggregate. Apart of linear dependence of elastic coefficients, transition from brittle to ductile behavior is observed as pressure is increased from 0 to 25 GPa. We have successfully obtained variation of lattice constant, volume expansion, bulk modulus, Debye temperature and specific heat capacities with pressure and temperature in the range of 0-25 GPa and 0-600 K. All the calculated optical properties such as the complex dielectric function ɛ(ω), optical conductivity σ(ω), energy loss function L(ω), absorption coefficient α(w), refractive index n(ω), reflectivity R(ω), and effective number of electrons n eff, via sum rules shift towards the higher energies under the application of pressure.

Evaluation of Metakaolin and Slag for GDOT Concrete Specifications and Mass Concrete Provision - Phase I

DOT National Transportation Integrated Search

2017-11-01

This report documents the evaluation of cement replacement with mekaolin and slag materials supplied by multiple vendors by measuring compressive strength, tensile strength, modulus of rupture, modulus of elasticity, sulfate expansion, alkali-silica ...

Indentation analysis of active viscoelastic microplasmodia of P. polycephalum

NASA Astrophysics Data System (ADS)

Fessel, Adrian; Oettmeier, Christina; Wechsler, Klaus; Döbereiner, Hans-Günther

2018-01-01

Simple organisms like Physarum polycephalum realize complex behavior, such as shortest path optimization or habituation, via mechanochemical processes rather than by a network of neurons. A full understanding of these phenomena requires detailed investigation of the underlying mechanical properties. To date, micromechanical measurements on P. polycephalum are sparse and lack reproducibility. This prompts study of microplasmodia, a reproducible and homogeneous form of P. polycephalum that resembles the plasmodial ectoplasm responsible for mechanical stability and generation of forces. We combine investigation of ultra-structure and dimension of P. polycephalum with the analysis of data obtained by indentation of microplasmodia, employing a novel nonlinear viscoelastic scaling model that accounts for finite dimension of the sample. We identify the multi-modal distribution of parameters such as Young’s moduls, Poisson’s ratio, and relaxation times associated with viscous processes that cover five orders of magnitude. Results suggest a characterization of microplasmodia as porous, compressible structures that act like elastic solids with high Young’s modulus on short time scales, whereas on long time-scales and upon repeated indentation viscous behavior dominates and the effective modulus is significantly decreased. Furthermore, Young’s modulus is found to oscillate in phase with shape of microplasmodia, emphasizing that modeling P. polycephalum oscillations as a driven oscillator with constant moduli is not practicable.

Determination of replicate composite bone material properties using modal analysis.

PubMed

Leuridan, Steven; Goossens, Quentin; Pastrav, Leonard; Roosen, Jorg; Mulier, Michiel; Denis, Kathleen; Desmet, Wim; Sloten, Jos Vander

2017-02-01

Replicate composite bones are used extensively for in vitro testing of new orthopedic devices. Contrary to tests with cadaveric bone material, which inherently exhibits large variability, they offer a standardized alternative with limited variability. Accurate knowledge of the composite's material properties is important when interpreting in vitro test results and when using them in FE models of biomechanical constructs. The cortical bone analogue material properties of three different fourth-generation composite bone models were determined by updating FE bone models using experimental and numerical modal analyses results. The influence of the cortical bone analogue material model (isotropic or transversely isotropic) and the inter- and intra-specimen variability were assessed. Isotropic cortical bone analogue material models failed to represent the experimental behavior in a satisfactory way even after updating the elastic material constants. When transversely isotropic material models were used, the updating procedure resulted in a reduction of the longitudinal Young's modulus from 16.00GPa before updating to an average of 13.96 GPa after updating. The shear modulus was increased from 3.30GPa to an average value of 3.92GPa. The transverse Young's modulus was lowered from an initial value of 10.00GPa to 9.89GPa. Low inter- and intra-specimen variability was found. Copyright © 2016 Elsevier Ltd. All rights reserved.

Mechanical, Anisotropic, and Electronic Properties of XN (X = C, Si, Ge): Theoretical Investigations.

PubMed

Ma, Zhenyang; Liu, Xuhong; Yu, Xinhai; Shi, Chunlei; Wang, Dayun

2017-08-08

The structural, mechanical, elastic anisotropic, and electronic properties of Pbca -XN (X = C, Si, Ge) are investigated in this work using the Perdew-Burke-Ernzerhof (PBE) functional, Perdew-Burke-Ernzerhof for solids (PBEsol) functional, and Ceperly and Alder, parameterized by Perdew and Zunger (CA-PZ) functional in the framework of density functional theory. The achieved results for the lattice parameters and band gap of Pbca -CN with the PBE functional in this research are in good accordance with other theoretical results. The band structures of Pbca -XN (X = C, Si, Ge) show that Pbca -SiN and Pbca -GeN are both direct band gap semiconductor materials with a band gap of 3.39 eV and 2.22 eV, respectively. Pbca -XN (X = C, Si, Ge) exhibits varying degrees of mechanical anisotropic properties with respect to the Poisson's ratio, bulk modulus, shear modulus, Young's modulus, and universal anisotropic index. The (001) plane and (010) plane of Pbca -CN/SiN/GeN both exhibit greater elastic anisotropy in the bulk modulus and Young's modulus than the (100) plane.

A study of the influence of micro and nano phase morphology on the mechanical properties of a rubber-modified epoxy resin

NASA Astrophysics Data System (ADS)

Russell, Bobby Glenn

Epoxy resins are thermosets with extraordinary adhesion; high strength; good resistance to creep, heat, and chemicals; and they have low shrinkage. Conversely, these polymers are brittle, they are sensitive to moisture, and they exhibit poor toughness. To improve their toughness, they are often modified by introducing dispersed rubber particles in the primary phase. In this study, the epoxy resin was modified with carboxyl-terminated butadiene acrylonitrile (CTBN), liquid-reactive rubbers. The initiator concentration, percent acrylonitrile in the CTBN rubber, and cure temperatures were altered to give varying materials properties. Statistical analysis of the morphology data showed that the percentage of rubber acrylonitrile had an effect on both the rubber particle size and volume fraction. The cure temperature had an effect on the rubber particle volume and modulus. Plots of the rubber particle size, volume fraction, and modulus versus bulk elastic storage modulus and fracture toughness revealed that rubber particle size had no effect on bulk properties, volume fraction and rubber particle modulus had an effect on both the bulk storage elastic modulus and fracture toughness.

Design optimization of a radial functionally graded dental implant.

PubMed

Ichim, Paul I; Hu, Xiaozhi; Bazen, Jennifer J; Yi, Wei

2016-01-01

In this work, we use FEA to test the hypothesis that a low-modulus coating of a cylindrical zirconia dental implant would reduce the stresses in the peri-implant bone and we use design optimization and the rule of mixture to estimate the elastic modulus and the porosity of the coating that provides optimal stress shielding. We show that a low-modulus coating of a dental implant significantly reduces the maximum stresses in the peri-implant bone without affecting the average stresses thus creating a potentially favorable biomechanical environment. Our results suggest that a resilient coating is capable of reducing the maximum compressive and tensile stresses in the peri-implant bone by up to 50% and the average stresses in the peri-implant bone by up to 15%. We further show that a transitional gradient between the high-modulus core and the low-modulus coating is not necessary and for a considered zirconia/HA composite the optimal thickness of the coating is 100 µ with its optimal elastic at the lowest value considered of 45 GPa. © 2015 Wiley Periodicals, Inc.

Mechanical, Anisotropic, and Electronic Properties of XN (X = C, Si, Ge): Theoretical Investigations

PubMed Central

Ma, Zhenyang; Liu, Xuhong; Yu, Xinhai; Shi, Chunlei; Wang, Dayun

2017-01-01

The structural, mechanical, elastic anisotropic, and electronic properties of Pbca-XN (X = C, Si, Ge) are investigated in this work using the Perdew–Burke–Ernzerhof (PBE) functional, Perdew–Burke–Ernzerhof for solids (PBEsol) functional, and Ceperly and Alder, parameterized by Perdew and Zunger (CA–PZ) functional in the framework of density functional theory. The achieved results for the lattice parameters and band gap of Pbca-CN with the PBE functional in this research are in good accordance with other theoretical results. The band structures of Pbca-XN (X = C, Si, Ge) show that Pbca-SiN and Pbca-GeN are both direct band gap semiconductor materials with a band gap of 3.39 eV and 2.22 eV, respectively. Pbca-XN (X = C, Si, Ge) exhibits varying degrees of mechanical anisotropic properties with respect to the Poisson’s ratio, bulk modulus, shear modulus, Young’s modulus, and universal anisotropic index. The (001) plane and (010) plane of Pbca-CN/SiN/GeN both exhibit greater elastic anisotropy in the bulk modulus and Young’s modulus than the (100) plane. PMID:28786960

Dynamic Simulation of VEGA SRM Bench Firing By Using Propellant Complex Characterization

NASA Astrophysics Data System (ADS)

Di Trapani, C. D.; Mastrella, E.; Bartoccini, D.; Squeo, E. A.; Mastroddi, F.; Coppotelli, G.; Linari, M.

2012-07-01

During the VEGA launcher development, from the 2004 up to now, 8 firing tests have been performed at Salto di Quirra (Sardinia, Italy) and Kourou (Guyana, Fr) with the objective to characterize and qualify of the Zefiros and P80 Solid Rocket Motors (SRM). In fact the VEGA launcher configuration foreseen 3 solid stages based on P80, Z23 and Z9 Solid Rocket Motors respectively. One of the primary objectives of the firing test is to correctly characterize the dynamic response of the SRM in order to apply such a characterization to the predictions and simulations of the VEGA launch dynamic environment. Considering that the solid propellant is around 90% of the SRM mass, it is very important to dynamically characterize it, and to increase the confidence in the simulation of the dynamic levels transmitted to the LV upper part from the SRMs. The activity is articulated in three parts: • consolidation of an experimental method for the dynamic characterization of the complex dynamic elasticity modulus of elasticity of visco-elastic materials applicable to the SRM propellant operative conditions • introduction of the complex dynamic elasticity modulus in a numerical FEM benchmark based on MSC NASTRAN solver • analysis of the effect of the introduction of the complex dynamic elasticity modulus in the Zefiros FEM focusing on experimental firing test data reproduction with numerical approach.

MR-ARFI-based method for the quantitative measurement of tissue elasticity: application for monitoring HIFU therapy

NASA Astrophysics Data System (ADS)

Vappou, Jonathan; Bour, Pierre; Marquet, Fabrice; Ozenne, Valery; Quesson, Bruno

2018-05-01

Monitoring thermal therapies through medical imaging is essential in order to ensure that they are safe, efficient and reliable. In this paper, we propose a new approach, halfway between MR acoustic radiation force imaging (MR-ARFI) and MR elastography (MRE), allowing for the quantitative measurement of the elastic modulus of tissue in a highly localized manner. It relies on the simulation of the MR-ARFI profile, which depends on tissue biomechanical properties, and on the identification of tissue elasticity through the fitting of experimental displacement images measured using rapid MR-ARFI. This method was specifically developed to monitor MR-guided high intensity focused ultrasound (MRgHIFU) therapy. Elasticity changes were followed during HIFU ablations (N  =  6) performed ex vivo in porcine muscle samples, and were compared to temperature changes measured by MR-thermometry. Shear modulus was found to increase consistently and steadily a few seconds after the heating started, and such changes were found to be irreversible. The shear modulus was found to increase from 1.49  ±  0.48 kPa (before ablation) to 3.69  ±  0.93 kPa (after ablation and cooling). Thanks to its ability to perform quantitative elasticity measurements in a highly localized manner around the focal spot, this method proved to be particularly attractive for monitoring HIFU ablations.

Effect of cholesterol lowering on stiffness of aortic and femoral arterial walls in rabbits on a high fat diet.

PubMed

Xue, Li; Xu, Wan-Hai; Xu, Jin-Zhi; Zhang, Tong; Bi, Hong-Yuan; Shen, Bao-Zhong

2009-06-20

Researches in arterial elasticity have increased over the past few years. We investigated the effects of simvastatin on vascular stiffness in fat fed rabbits by ultrasonography. Thirty rabbits were assigned randomly to 3 groups: normal control group (A), the cholesterol group (B), simvastatin group (C: high fat diet for 4 weeks and high fat diet + simvastatin for further 4 weeks). Stiffness coefficient, pressure strain elastic modulus and velocity of pulse waves in abdominal aorta and femoral artery were measured by ultrasonographic echo tracking at the end of the 4th and the 8th weeks. At the end of the 4th week, stiffness coefficient, pressure strain elastic modulus and pulse wave velocity of femoral artery were significantly increased in group B compared with those in group A. Similarly, at the end of the 8th week, the same parameters of abdominal aorta were significantly increased in group B compared with those in group A. In contrast, stiffness coefficient, pressure strain elastic modulus and pulse wave velocity of femoral artery were significantly decreased in group C compared with those in group B, however, there was no significant difference in parameters of abdominal aorta between groups B and C. Short term administration of simvastatin can improve the elasticity of femoral artery but not abdominal aorta.