NDE Elastic Properties of Fiber-Reinforced Composite Materials
NASA Technical Reports Server (NTRS)
Bar-Cohen, Y.
1995-01-01
Fiber-reinforced composites are increasingly replacing metallic alloys as structural materials for primary components of fracture-critical structures. This trend is a result of the growing understanding of material behavior and recognition of the desirable properties of composites. A research program was conducted on NDE methods for determining the elastic properties of composites.
Elastic therapeutic tape: do they have the same material properties?
Boonkerd, Chuanpis; Limroongreungrat, Weerawat
2016-04-01
[Purpose] Elastic therapeutic tape has been widely used for rehabilitation and treatment of sports injuries. Tapes with different elastic properties serve different treatment purposes with inappropriate tension reducing tape effectiveness. Many tapes are available in the market, but studies on tape properties are limited. The aim of this study was to examine the material properties of elastic therapeutic tape. [Subjects and Methods] Brands of elastic therapeutic tape included KinesioTex(®), ATex, Mueller, 3M, and ThaiTape. The Material Testing System Insight(®) 1 Electromechanical Testing Systems was used to apply a tensile force on elastic therapeutic tape. Ten specimens of each brand were tested. Stress, load, and Young's modulus at 25%, 50%, 75%, 100%, and maximum point were collected. One-way analysis of variance with post hoc testing was used to analyze tape parameters. [Results] Maximum elongation and Young's modulus at all percentages were significantly different between brands. There were no differences in maximum load and maximum stress. [Conclusion] Mechanical properties are different for commercial elastic therapeutic tapes. Physiotherapists and other clinicians should be aware of mechanical tape properties to correctly apply kinesio tape. PMID:27190472
Elastic therapeutic tape: do they have the same material properties?
Boonkerd, Chuanpis; Limroongreungrat, Weerawat
2016-01-01
[Purpose] Elastic therapeutic tape has been widely used for rehabilitation and treatment of sports injuries. Tapes with different elastic properties serve different treatment purposes with inappropriate tension reducing tape effectiveness. Many tapes are available in the market, but studies on tape properties are limited. The aim of this study was to examine the material properties of elastic therapeutic tape. [Subjects and Methods] Brands of elastic therapeutic tape included KinesioTex®, ATex, Mueller, 3M, and ThaiTape. The Material Testing System Insight® 1 Electromechanical Testing Systems was used to apply a tensile force on elastic therapeutic tape. Ten specimens of each brand were tested. Stress, load, and Young’s modulus at 25%, 50%, 75%, 100%, and maximum point were collected. One-way analysis of variance with post hoc testing was used to analyze tape parameters. [Results] Maximum elongation and Young’s modulus at all percentages were significantly different between brands. There were no differences in maximum load and maximum stress. [Conclusion] Mechanical properties are different for commercial elastic therapeutic tapes. Physiotherapists and other clinicians should be aware of mechanical tape properties to correctly apply kinesio tape. PMID:27190472
Elastic properties of nanostructured materials with layered grain boundary structure
NASA Astrophysics Data System (ADS)
Karakasidis, T. E.; Charitidis, C. A.; Skarakis, D.; Chouliaras, F.
2007-08-01
Atomistic calculations of the elastic constants for a bulk nanostructured material that consists of a layered structure where alternating layers meet along high angle grain boundaries and where atoms interact via a Lennard-Jones potential are presented. The calculations of the elastic constants were performed in the frame of homogeneous deformations for a wide range of layer widths ranging from 2.24 up to 74.62 nm. The results showed that the relaxation of the atomic structure affects the elastic constants for the cases where more than 5% of atoms are located in the GB region. Also it was found that the way that external stresses are applied on the system affects the values of the obtained elastic properties, with the elastic constants related to the characteristic directions of the grain boundary being the most affected ones. The findings of this work are of interest for the fabrication methods of nanostructured materials, the measurement methods of their elastic properties as well as multiscale modeling schemes of nanostructured materials.
Cyclic material properties tests supporting elastic-plastic analysis development
Hodge, S.C.; Minicucci, J.M.
1996-11-01
Correlation studies have shown that hardening models currently available in the ABAQUS finite element code (isotropic, kinematic) do not accurately capture the inelastic strain reversals that occur due to structural rebounding from a rapidly applied transient dynamic load. The purpose of the Cyclic Material properties Test program was to obtain response data for the first several cycles of inelastic strain reversal from a cyclic properties test. This data is needed to develop elastic-plastic analysis methods that can accurately predict strains and permanent sets in structures due to rapidly applied transient dynamic loading. Test specimens were cycled at inelastic strain levels typical of rapidly applied transient dynamic analyses (0.5% to 4.0%). In addition to the inelastic response data, cyclic material properties for high yield strength (80 ksi) steel were determined including a cyclic stress-strain curve for a stabilized specimen. Two test methods, the Incremental Step method and the Companion specimen Method, were sued to determine cyclic properties. The incrementally decreasing strain amplitudes in the first loading block of the Incremental Step method test is representative of the response of structures subjected to rapidly applied transient dynamic loads. The inelastic strain history data generated by this test program will be used to support development of a material model that can accurately predict inelastic material behavior including inelastic strain reversals. Additionally, this data can be used to verify material model enhancements to elastic-plastic finite element analysis codes.
Adler, Thomas A.
1996-01-01
The invention pertains a method of determining elastic and plastic mechanical properties of ceramics, intermetallics, metals, plastics and other hard, brittle materials which fracture prior to plastically deforming when loads are applied. Elastic and plastic mechanical properties of ceramic materials are determined using spherical indenters. The method is most useful for measuring and calculating the plastic and elastic deformation of hard, brittle materials with low values of elastic modulus to hardness.
Nonlinear elastic properties of various man-made materials
Darvennes, C.M.; Hou, X.
1998-12-31
Second harmonic generation was measured in several man-made materials for possible application of nonlinear elastic properties to non-destructive testing. Samples included several thicknesses of two types of carbon fiber/polymer matrix composites, three types of concretes, and plywood. Steel and Aluminum specimens were used as references and one of the composite samples was evaluated before and after fatigue cycles. Some interesting observations were made: (1) the two composites were much more nonlinear than the metals, (2) the concretes and the wood were extremely absorptive, (3) one of the concrete samples exhibited a third harmonic but no second harmonic, and (4) fatigue cycles significantly increased the second harmonic, even though no damage was observed by C-scan. The possible applications of these results to NDE will be discussed.
Nonlinear elastic properties of materials with residual stresses
NASA Astrophysics Data System (ADS)
Korobov, A.; Romanov, A.; Morozov, A.
2012-12-01
The non-linear elastic properties of rock samples and metal samples of microcrystalline aluminium alloy were studied using NRUS method. The residual shear strains were initially introduced in metal samples. In these samples the effect of slow dynamics was also investigated. Based on the analysis of experimental results it was concluded: the effect of slow dynamics, observed in the experiment, can not be explained solely by thermoelastic effects, but it is associated, in our opinion, with the slow relaxation of the internal structure of the samples.
Stress effects on the elastic properties of amorphous polymeric materials
NASA Astrophysics Data System (ADS)
Caponi, S.; Corezzi, S.; Mattarelli, M.; Fioretto, D.
2014-12-01
Brillouin light scattering measurements have been used to study the stress induced modification in the elastic properties of two glass forming polymers: polybutadiene and epoxy-amine resin, prototypes of linear and network polymers, respectively. Following the usual thermodynamic path to the glass transition, polybutadiene has been studied as a function of temperature from the liquid well into the glassy phase. In the epoxy resin, the experiments took advantage of the system ability to reach the glass both via the chemical vitrification route, i.e., by increasing the number of covalent bonds among the constituent molecules, as well as via the physical thermal route, i.e., by decreasing the temperature. Independently from the particular way chosen to reach the glassy phase, the measurements reveal the signature of long range tensile stresses development in the glass. The stress presence modifies both the value of the sound velocities and their mutual relationship, so as to break the generalized Cauchy-like relation. In particular, when long range stresses, by improvise sample cracking, are released, the frequency of longitudinal acoustic modes increases more than 10% in polybutadiene and ˜4% in the epoxy resin. The data analysis suggests the presence of at least two different mechanisms acting on different length scales which strongly affect the overall elastic behaviour of the systems: (i) the development of tensile stress acting as a negative pressure and (ii) the development of anisotropy which increases its importance deeper and deeper in the glassy state.
Stress effects on the elastic properties of amorphous polymeric materials
Caponi, S. E-mail: silvia.corezzi@unipg.it; Fioretto, D.
2014-12-07
Brillouin light scattering measurements have been used to study the stress induced modification in the elastic properties of two glass forming polymers: polybutadiene and epoxy-amine resin, prototypes of linear and network polymers, respectively. Following the usual thermodynamic path to the glass transition, polybutadiene has been studied as a function of temperature from the liquid well into the glassy phase. In the epoxy resin, the experiments took advantage of the system ability to reach the glass both via the chemical vitrification route, i.e., by increasing the number of covalent bonds among the constituent molecules, as well as via the physical thermal route, i.e., by decreasing the temperature. Independently from the particular way chosen to reach the glassy phase, the measurements reveal the signature of long range tensile stresses development in the glass. The stress presence modifies both the value of the sound velocities and their mutual relationship, so as to break the generalized Cauchy-like relation. In particular, when long range stresses, by improvise sample cracking, are released, the frequency of longitudinal acoustic modes increases more than 10% in polybutadiene and ∼4% in the epoxy resin. The data analysis suggests the presence of at least two different mechanisms acting on different length scales which strongly affect the overall elastic behaviour of the systems: (i) the development of tensile stress acting as a negative pressure and (ii) the development of anisotropy which increases its importance deeper and deeper in the glassy state.
Stress effects on the elastic properties of amorphous polymeric materials.
Caponi, S; Corezzi, S; Mattarelli, M; Fioretto, D
2014-12-01
Brillouin light scattering measurements have been used to study the stress induced modification in the elastic properties of two glass forming polymers: polybutadiene and epoxy-amine resin, prototypes of linear and network polymers, respectively. Following the usual thermodynamic path to the glass transition, polybutadiene has been studied as a function of temperature from the liquid well into the glassy phase. In the epoxy resin, the experiments took advantage of the system ability to reach the glass both via the chemical vitrification route, i.e., by increasing the number of covalent bonds among the constituent molecules, as well as via the physical thermal route, i.e., by decreasing the temperature. Independently from the particular way chosen to reach the glassy phase, the measurements reveal the signature of long range tensile stresses development in the glass. The stress presence modifies both the value of the sound velocities and their mutual relationship, so as to break the generalized Cauchy-like relation. In particular, when long range stresses, by improvise sample cracking, are released, the frequency of longitudinal acoustic modes increases more than 10% in polybutadiene and ∼4% in the epoxy resin. The data analysis suggests the presence of at least two different mechanisms acting on different length scales which strongly affect the overall elastic behaviour of the systems: (i) the development of tensile stress acting as a negative pressure and (ii) the development of anisotropy which increases its importance deeper and deeper in the glassy state. PMID:25481163
Elastic properties of granular materials under uniaxial compaction cycles
NASA Technical Reports Server (NTRS)
Warren, N.; Anderson, O. L.
1973-01-01
Data on andesitic and basaltic sands are presented showing compressional sound velocity, density, and creep as functions of uniaxial loading through several compaction cycles. Maximum pressures over which acoustic measurements were made were in the range from 600 to 700 bars. The dynamic elastic modulus varies with pressure in a manner analogous to that of a static elastic modulus defined by small pressure perturbations on a typical compaction cycle. After several compaction cycles, two compressional elastic moduli apparently exist at low pressure (thus two modes of compressional wave propagation through the samples are indicated). The elastic moduli observations are briefly discussed in terms of a general expression for compressibility.
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.
Influence of point defects on the elastic properties of mantle minerals and superhard materials
NASA Astrophysics Data System (ADS)
Chang, Yun-Yuan
Perfect crystals do not exist in nature. Defects in crystals modify their physical and chemical properties. Elastic properties relate stress to reversible strain and reflect the strength of interatomic bonding forces, which may be influenced by defects. This thesis advances our understanding of how defects influence the elastic properties of mantle minerals and superhard materials. In this study, I focused on defects associated with ferric iron (Fe 3+) and hydrogen (H) substitution in mantle minerals with application to interpreting the water content of the mantle from observed seismic wave speeds. High-pressure, single-crystal X-ray diffraction experiments were carried out to determine the comparative compressibility of hydrous and anhydrous Fo90 wadsleyite, the dominant phase in Earth's mantle transition zone (410-660 km depth). The results show that hydration of wadsleyite with 1 wt.% H2O reduces its bulk modulus by 4.7%, but has no influence on its pressure derivative. Therefore, the reduction in bulk sound velocity of wadsleyite associated with H defects should persist to mantle pressures. In another study, the equation of state and electronic spin state of ferric iron (Fe3+) in Fe-Al-phase D were determined, pertaining to dense hydrous magnesium silicates that could potentially transport water into the lower mantle. The results show that Fe3+ undergoes a gradual spin transition between 40 and 65 GPa, causing pronounced bulk-elastic softening of Fe-Al phase D within the spin transition pressure interval. Results provide an alternative interpretation for small-scale seismic heterogeneities beneath the Pacific rim. In addition to mantle silicates, I have determined the influence of nitrogen defects on the elastic properties of natural and synthetic diamond. The measurements of elastic moduli of synthetic nano-polycrystalline diamond (NPD) and natural type Ia diamond feature a newly developed optical contact micrometer for ultrasonic sample thickness measurements
NASA Astrophysics Data System (ADS)
Schindler, Stefan; Mergheim, Julia; Zimmermann, Marco; Aurich, Jan C.; Steinmann, Paul
2016-07-01
A two-scale material modeling approach is adopted in order to determine macroscopic thermal and elastic constitutive laws and the respective parameters for metal matrix composite (MMC). Since the common homogenization framework violates the thermodynamical consistency for non-constant temperature fields, i.e., the dissipation is not conserved through the scale transition, the respective error is calculated numerically in order to prove the applicability of the homogenization method. The thermomechanical homogenization is applied to compute the macroscopic mass density, thermal expansion, elasticity, heat capacity and thermal conductivity for two specific MMCs, i.e., aluminum alloy Al2024 reinforced with 17 or 30 % silicon carbide particles. The temperature dependency of the material properties has been considered in the range from 0 to 500°C, the melting temperature of the alloy. The numerically determined material properties are validated with experimental data from the literature as far as possible.
Homogenized mechanical properties of auxetic composite materials in finite-strain elasticity
NASA Astrophysics Data System (ADS)
Kochmann, Dennis M.; Venturini, Gabriela N.
2013-08-01
Careful microstructural design can result in materials with counterintuitive effective (macroscale) mechanical properties such as a negative Poisson’s ratio, commonly referred to as auxetic behavior. One specific approach to achieving auxetic behavior is to elastically connect structural elements with rotational degrees of freedom to result in elastic structures that unfold under uniaxial loading in specific directions, thereby giving rise to bi- or triaxial expansion, i.e. auxetic behavior (transverse expansion under uniaxial extension). This concept has been applied successfully to elastically coupled two-dimensional rigid rotational elements (such as rotating rectangles and triangles) which exhibit a negative effective in-plane Poisson’s ratio under uniaxial (ex)tension. Here, we adopt this fundamental design principle but take it to the next level by achieving auxetic behavior in finitely strained composites made of stiff inclusions in a hyperelastic matrix, and we study the resulting elastic properties under in-plane strain by numerical homogenization. Our results highlight the emergence of auxetic behavior based on geometric arrangement and properties of the base material and demonstrate a path towards simple inclusion-matrix composites with auxetic behavior.
Dynamic Bending Tolerance and Elastic-Plastic Material Properties of the Human Femur
Funk, J. R.; Kerrigan, J. R.; Crandall, J. R.
2004-01-01
The objective of this study was to provide data on the structural tolerance and material properties of the human femur in dynamic bending. Fifteen (15) isolated femurs from eight (8) males were tested in either posterior-to-anterior or lateral-to-medial three-point bending. The failure moment was 458 ± 95 Nm and did not differ significantly with loading direction. A method was developed to estimate the elastic-plastic material properties of the bone using both force-deflection data and strain gauge measurements. The bone material appeared to yield at about one third of the ultimate strain level prior to fracture. It is hoped that these data will aid in the development of injury criteria and finite element models for predicting injuries to pedestrians and vehicle occupants. PMID:15319127
NASA Astrophysics Data System (ADS)
Vila, F. D.; Rehr, J. J.
Effects of thermal vibrations are essential to obtain a more complete understanding of the properties of complex materials. For example, they are important in the analysis and simulation of x-ray absorption spectra (XAS). In previous work we introduced an ab initio approach for a variety of vibrational effects, such as crystallographic and XAS Debye-Waller factors, Debye and Einstein temperatures, and thermal expansion coefficients. This approach uses theoretical dynamical matrices from which the locally-projected vibrational densities of states are obtained using a Lanczos recursion algorithm. In this talk I present recent improvements to our implementation, which permit simulations of more complex materials with up to two orders of magnitude larger simulation cells. The method takes advantage of parallelization in calculations of the dynamical matrix with VASP. To illustrate these capabilities we discuss two problems of considerable interest: negative thermal expansion in ZrW2O8; and local inhomogeneities in the elastic properties of supported metal nanoparticles. Both cases highlight the importance of a local treatment of vibrational properties. Supported by DOE Grant DE-FG02-03ER15476, with computer support from DOE-NERSC.
Elastic properties of minerals
Aleksandrov, K.S.; Prodaivoda, G.T.
1993-09-01
Investigations of the elastic properties of the main rock-forming minerals were begun by T.V. Ryzhova and K.S. Aleksandrov over 30 years ago on the initiative of B.P. Belikov. At the time, information on the elasticity of single crystals in general, and especially of minerals, was very scanty. In the surveys of that time there was information on the elasticity of 20 or 30 minerals. These, as a rule, did not include the main rock-forming minerals; silicates were represented only by garnets, quartz, topaz, tourmaline, zircon, beryl, and staurolite, which are often found in nature in the form of large and fairly high-quality crystals. Then and even much later it was still necessary to prove a supposition which now seems obvious: The elastic properties of rocks, and hence the velocities of elastic (seismic) waves in the earth`s crust, are primarily determined by the elastic characteristics of the minerals composing these rocks. Proof of this assertion, with rare exceptions of mono-mineralic rocks (marble, quartzite, etc.) cannot be obtained without information on the elasticities of a sufficiently large number of minerals, primarily framework, layer, and chain silicates which constitute the basis of most rocks. This also served as the starting point and main problem of the undertakings of Aleksandrov, Ryzhova, and Belikov - systematic investigations of the elastic properties of minerals and then of various rocks. 108 refs., 7 tabs.
Milhans, Jacqueline; Ahzi, Said; Garmestani, Hamid; Khaleel, Mohammad A.; Sun, Xin; Koeppel, Brian J.
2009-05-01
In this study, the effective elastic properties and coefficients of thermal expansion (CTE) of a glass-ceramic were predicted using homogenization techniques. Using G18, a glass-ceramic solid oxide fuel cell (SOFC) sealant as an initial reference material, the effectiveness of different homogenization models was investigated for a two-phase glass-ceramic. The elastic properties and CTEs of the G18 amorphous phase are currently unknown. Thus, estimated values were used as an input to the models. The predictive model offers accurate macroscopic values on both the elastic modulus and the CTE of glass-ceramic materials, providing the estimated amorphous values are reasonable. This model can be used in designing glass-ceramic SOFC seal materials for its specific operation conditions.
Doyle, Heather; Lohfeld, Stefan; McHugh, Peter
2014-03-01
This study assesses the ability of finite element (FE) models to capture the mechanical behaviour of sintered orthopaedic scaffold materials. Individual scaffold struts were fabricated from a 50:50 wt% poly-ε-caprolactone (PCL)/β-tricalcium phosphate (β-TCP) blend, using selective laser sintering. The tensile elastic modulus of single struts was determined experimentally. High resolution FE models of single struts were generated from micro-CT scans (28.8 μm resolution) and an effective strut elastic modulus was calculated from tensile loading simulations. Three material assignment methods were employed: (1) homogeneous PCL elastic constants, (2) composite PCL/β-TCP elastic constants based on rule of mixtures, and (3) heterogeneous distribution of micromechanically-determined elastic constants. In comparison with experimental results, the use of homogeneous PCL properties gave a good estimate of strut modulus; however it is not sufficiently representative of the real material as it neglects the β-TCP phase. The rule of mixtures method significantly overestimated strut modulus, while there was no significant difference between strut modulus evaluated using the micromechanically-determined elastic constants and experimentally evaluated strut modulus. These results indicate that the multi-scale approach of linking micromechanical modelling of the sintered scaffold material with macroscale modelling gives an accurate prediction of the mechanical behaviour of the sintered structure. PMID:24057867
A NONLINEAR MESOSCOPIC ELASTIC CLASS OF MATERIALS
P. JOHNSON; R. GUYER; L. OSTROVSKY
1999-09-01
It is becoming clear that the elastic properties of rock are shared by numerous other materials (sand, soil, some ceramics, concrete, etc.). These materials have one or more of the following properties in common strong nonlinearity, hysteresis in stress-strain relation, slow dynamics and discrete memory. Primarily, it is the material's compliance, the mesoscopic linkages between the rigid components, that give these materials their unusual elastic properties.
Milhans, Jacqueline; Li, Dongsheng; Khaleel, Mohammad A.; Sun, Xin; Garmestani, Hamid
2010-09-01
A full statistical analysis of the microstructure of glass–ceramic solid oxide fuel cell (SOFC) seal material, G18, is performed to calculate elastic properties. Predictions are made for samples aged for 4 h and 1000 h, giving different crystallinity levels. Microstructure of the glass–ceramic G18 is characterized by correlation function for each individual phase. Predicted results are compared with the Voigt and Reuss bounds in this study. The weak contrast analysis results in elastic modulus predictions between the upper and lower bounds but closer to the upper bound.
Sewell, T. D.; Bedrov, D.; Menikoff, Ralph; Smith, G. D.
2001-01-01
Atomistic molecular dynamics simulations have been used to calculate isothermal elastic properties for {beta}-, {alpha}-, and {delta}-HMX. The complete elastic tensor for each polymorph was determined at room temperature and pressure via analysis of microscopic strain fluctuations using formalism due to Rahman and Parrinello [J. Chem. Phys. 76,2662 (1982)]. Additionally, the isothermal compression curve was computed for {beta}-HMX for 0 {le} p {le} 10.6 GPa; the bulk modulus K and its pressure derivative K{prime} were obtained from two fitting forms employed previously in experimental studies of the {beta}-HMX equation of state. Overall, the results indicate good agreement between the bulk modulus predicted from the measured and calculated compression curves. The bulk modulus determined directly from the elastic tensor of {beta}-HMX is in significant disagreement with the compression curve-based results. The explanation for this discrepancy is an area of current research.
Elastic Properties of Mantle Minerals
NASA Astrophysics Data System (ADS)
Duffy, T. S.; Stan, C. V.
2012-12-01
The most direct information about the interior structure of the Earth comes from seismic wave velocities. Interpretation of seismic data requires an understanding of how sound velocities and elastic properties of minerals vary with pressure, temperature, crystal structure, and composition as well as the role of anelasticity, melts, etc. More generally, elastic moduli are important for understanding many solid-state phenomena including mechanical stability, interatomic interactions, material strength, compressibility, and phase transition mechanisms. The database of mineral elasticity measurements has been growing rapidly in recent years. In this work, we report initial results of an ongoing survey of our current knowledge of mineral elasticity at both ambient conditions and high pressures and temperatures. The analysis is selective, emphasizing single crystal measurements but also incorporating polycrystalline measurements and volume compression data as appropriate. The goal is to synthesize our current understanding of mineral elasticity in terms of structure and composition, and to identify the major remaining needs for experimental and theoretical work. Clinopyroxenes (Cpx) provide an example of our approach. A wide range of clinopyroxene compositions are found geologically and Mg-, Ca-, and Na-rich clinopyroxenes are expected to be important components in the upper mantle. The single-crystal elastic properties of a number of endmember Cpx compositions have been measured and these exhibit a range of ~25% in shear velocity. Those with monovalent cations (spodumene, jadeite) in the M2 site exhibit the highest velocities while Fe-rich (hendenbergit, acmite) compositions have the lowest velocities. The effects on velocity due to a wide range of chemical substitutions can be defined, but there are important discrepancies and omissions in the database. New measurements of omphacites, intermediate diopside-hedenbergite compositions, aegerine/acmite, augite, etc. are
Elastic properties of hedenbergite
NASA Astrophysics Data System (ADS)
Kandelin, John; Weidner, Donald J.
1988-02-01
The single-crystal elastic moduli of hedenbergite (CaFeSi2O6) hare been measured at 20°C and 1 bar using Brillouin spectroscopy. The moduli are (in gigapascals): C11 = 222, C22 = 176, C23 = 249, C44 = 55, C55 = 63, C66 = 60, C12 = 69, C13 = 79, C33, = 86, C15 = 12, C25 = 13, C35 = 26, C46 = -10. The comparison of elastic properties among Mg-Fe-Ca bearing pyroxenes, known as quadrilateral pyroxenes, reveals only weak variations with changes in composition. Of the four quadrilateral pyroxenes, orthoferrosilite has elastic properties distinctive from the others. The principal differences among these pyroxenes are due to subtle structural differences. In particular, the mechanical linkage between the M2 polyhedral chains in clinopyroxenes enhances the importance of the cation in this site. In contrast to the orthopyroxenes, the aggregate shear modulus μ of the calcium-bearing clinopyroxenes (diopside and hedenbergite) exhibits no dependence on the amount of iron (Fe2+) present in the structure, while the ratio K/μ does. As a result, the compressional and shear acoustic velocities of the calcium-bearing clinopyroxenes show a smaller dependency on iron content than do the orthopyroxenes.
NASA Astrophysics Data System (ADS)
Milhet, X.; Gadaud, P.; Caccuri, V.; Bertheau, D.; Mellier, D.; Gerland, M.
2015-10-01
Silver pastes are good candidates as alternative materials to lead solder alloys. However, little is known about the relationship between their microstructure and their mechanical properties. This issue is addressed by developing a specific route to obtain standalone sintered bulk specimens representative of the real sintered joints. The relationship between the density and the pore surface fraction is established, allowing the density of the material to be obtained independently from its size and geometry. The elastic constants of both sintered joints and sintered bulk specimens are investigated using dynamic resonant testing. A strong correlation between the elastic constants and the density is established. In contrast to the sintered bulk specimens, for which the Young's modulus remains constant after annealing, Young's modulus of the sintered joints evolves significantly towards a stabilized value. This is derived from thermal stresses relaxation within the sintered joint.
NASA Astrophysics Data System (ADS)
Enakoutsa, Koffi
2014-09-01
Recently, the works by Toupin, Mindlin, Sokolowski and Germain have been developed following two research streams. In the first one, higher-order gradient continuum models were developed based on the Cauchy tetrahedron argument (see, e.g., dell'Isola and Seppecher in Comptes Rendus de l Academie de Sciences 17 Serie IIb: Mecanique, Physique, Chimie, Astronomie 321:303-308, 1995, Meccanica 32:33-52 1997, Zeitschrift fr Angewandte Mathematik und Physik 63(6):1119-1141, 2012). In the second one, the structure of higher-order gradient models is developed with a view to the applications. In particular in the model of linear isotropic solids proposed by Dell'Isola, Sciarra and Vidoli (DSV), the main constitutive equation is obtained for the case of second gradient models. This model introduces in addition to the two well-known Lame's elastic constants five constitutive constants. The practical applications of this model remain in its infancy since the issue of determining the new moduli it introduces is not yet completely addressed. Also, analytical solutions of simple boundary value problems that can be helpful to grasp some of the physical foundations of this model are missing. This paper aims to address these two issues by providing the analytical solutions for two model problems, a spherical shell subjected to axisymmetric loading conditions and the circular bending of a beam in plane strain, both the beam and the shell obeying the DSV second gradient isotropic elastic model. The solution of the circular bending of a beam has served to grasp some of the physical soundness of the model. A framework based on homogenization under inhomogeneous boundary conditions is also suggested to determine the unknown constitutive constants, which are provided in the particular case of elastic porous heterogeneous materials.
NASA Astrophysics Data System (ADS)
Enakoutsa, Koffi
2015-06-01
Recently, the works by Toupin, Mindlin, Sokolowski and Germain have been developed following two research streams. In the first one, higher-order gradient continuum models were developed based on the Cauchy tetrahedron argument (see, e.g., dell'Isola and Seppecher in Comptes Rendus de l Academie de Sciences 17 Serie IIb: Mecanique, Physique, Chimie, Astronomie 321:303-308, 1995, Meccanica 32:33-52 1997, Zeitschrift fr Angewandte Mathematik und Physik 63(6):1119-1141, 2012). In the second one, the structure of higher-order gradient models is developed with a view to the applications. In particular in the model of linear isotropic solids proposed by Dell'Isola, Sciarra and Vidoli (DSV), the main constitutive equation is obtained for the case of second gradient models. This model introduces in addition to the two well-known Lame's elastic constants five constitutive constants. The practical applications of this model remain in its infancy since the issue of determining the new moduli it introduces is not yet completely addressed. Also, analytical solutions of simple boundary value problems that can be helpful to grasp some of the physical foundations of this model are missing. This paper aims to address these two issues by providing the analytical solutions for two model problems, a spherical shell subjected to axisymmetric loading conditions and the circular bending of a beam in plane strain, both the beam and the shell obeying the DSV second gradient isotropic elastic model. The solution of the circular bending of a beam has served to grasp some of the physical soundness of the model. A framework based on homogenization under inhomogeneous boundary conditions is also suggested to determine the unknown constitutive constants, which are provided in the particular case of elastic porous heterogeneous materials.
Haycraft, James J
2009-12-01
The acoustic phonons of the epsilon polymorph of 2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaazatetracyclo [5.5.0.0(5,9).0(3,11)] dodecane (epsilon-CL-20) have been studied using Brillouin scattering spectroscopy. Analysis of the acoustic phonon velocities allowed determination of the complete stiffness tensor for this energetic material. The results are compared to a theoretical determination of the epsilon-CL-20 elastic constants, bulk moduli, and shear moduli. The observed ordering of elastic constants, C(22)>C(33)>C(11), is noted to be different from other nitramine energetic materials. Finally, the elasticity of epsilon-CL-20 is compared to recently published reports on cyclotrimethylene trinitramine's (RDX) elasticity and the beta polymorph of cyclotetramethylene tetranitramine's (beta-HMX) elasticity. PMID:19968345
NASA Astrophysics Data System (ADS)
Zheng, Zhaoyang; Jiang, Xue; Zhao, Jijun
2015-05-01
The structural, electronic and elastic properties for metal-organic frameworks (MOFs) as energetic materials are investigated using non-local density functional theory with dispersion correction. The lattice constants of MOF-EMs are reproduced well by optPBE-vdW functional. The electronic structure analysis reveals that NHN is a metal, while the others are semiconductors or insulators with band gap from 0.1 eV to 4.7 eV. NHP, CHP, CHHP and CuAN are predicted to be magnetic. We also discuss the impact sensitivities of MOF-EMs in terms of their electronic structures. The calculated bulk modulus ranges from 15.1 GPa (CuAN) to 35.0 GPa (NHN).
Elastic Properties of Plasticine, Silly Putty, and Tennis Strings
ERIC Educational Resources Information Center
Cross, Rod
2012-01-01
How would a physicist describe the elastic properties of an apple or a banana? Physics students and teachers are familiar with the elastic properties of metal springs, but are likely to be less familiar with the elastic properties of other common materials. The behavior of a metal spring is commonly examined in the laboratory by adding masses to…
Probing hysteretic elasticity in weakly nonlinear materials
Johnson, Paul A; Haupert, Sylvain; Renaud, Guillaume; Riviere, Jacques; Talmant, Maryline; Laugier, Pascal
2010-12-07
Our work is aimed at assessing the elastic and dissipative hysteretic nonlinear parameters' repeatability (precision) using several classes of materials with weak, intermediate and high nonlinear properties. In this contribution, we describe an optimized Nonlinear Resonant Ultrasound Spectroscopy (NRUS) measuring and data processing protocol applied to small samples. The protocol is used to eliminate the effects of environmental condition changes that take place during an experiment, and that may mask the intrinsic elastic nonlinearity. As an example, in our experiments, we identified external temperature fluctuation as a primary source of material resonance frequency and elastic modulus variation. A variation of 0.1 C produced a frequency variation of 0.01 %, which is similar to the expected nonlinear frequency shift for weakly nonlinear materials. In order to eliminate environmental effects, the variation in f{sub 0} (the elastically linear resonance frequency proportional to modulus) is fit with the appropriate function, and that function is used to correct the NRUS calculation of nonlinear parameters. With our correction procedure, we measured relative resonant frequency shifts of 10{sup -5} , which are below 10{sup -4}, often considered the limit to NRUS sensitivity under common experimental conditions. Our results show that the procedure is an alternative to the stringent control of temperature often applied. Applying the approach, we report nonlinear parameters for several materials, some with very small nonclassical nonlinearity. The approach has broad application to NRUS and other Nonlinear Elastic Wave Spectroscopy approaches.
Babu, K. Ephraim; Murali, N.; Babu, K. Vijaya; Veeraiah, V.; Babu, B. Kishore
2015-05-15
The first principles calculation within the full potential linearized augmented plane wave (FP-LAPW) method is applied to study the structural, electronic and elastic properties of cubic perovskite-type compounds KCaF{sub 3} and RbCaF{sub 3}. The exchange correlation effects are included through the LDA, GGA and modified Becke-Johnson (mBJ) exchange potential. The calculated structural properties such as equilibrium lattice constant, the bulk modulus and its pressure derivative are in good agreement with the available data. KCaF{sub 3} and RbCaF{sub 3} have wide and indirect band gaps and they agree with experimental values. The elastic properties such as elastic constants, anisotropy factor, shear modulus, Young’s modulus and Poisson’s ratio are obtained for the first time. KCaF{sub 3} and RbCaF{sub 3} are elastically anisotropic and the B/G ratio indicate that these are ductile materials.
On the anisotropic elastic properties of hydroxyapatite.
NASA Technical Reports Server (NTRS)
Katz, J. L.; Ukraincik, K.
1971-01-01
Experimental measurements of the isotropic elastic moduli on polycrystalline specimens of hydroxyapatite and fluorapatite are compared with elastic constants measured directly from single crystals of fluorapatite in order to derive a set of pseudo single crystal elastic constants for hydroxyapatite. The stiffness coefficients thus derived are given. The anisotropic and isotropic elastic properties are then computed and compared with similar properties derived from experimental observations of the anisotropic behavior of bone.
Identification of heterogeneous elastic material characteristics by virtual fields method
NASA Astrophysics Data System (ADS)
Sato, Yuya; Arikawa, Shuichi; Yoneyama, Satoru
2015-03-01
In this study, a method for identifying the elastic material characteristics of a heterogeneous material from measured displacements is proposed. The virtual fields method is employed for determining the elastic material characteristics. The solid propellant is considered as heterogeneous materials for the test subject. An equation representing the distribution of the material properties of the solid propellant is obtained by Fick's law, and the distribution is applied to the virtual fields method. The effectiveness of the proposed method is demonstrated by applying to displacement fields obtained using finite element analysis. Results show that the heterogeneous material properties can be obtained by the proposed method.
Mesoscale elastic properties of marine sponge spicules.
Zhang, Yaqi; Reed, Bryan W; Chung, Frank R; Koski, Kristie J
2016-01-01
Marine sponge spicules are silicate fibers with an unusual combination of fracture toughness and optical light propagation properties due to their micro- and nano-scale hierarchical structure. We present optical measurements of the elastic properties of Tethya aurantia and Euplectella aspergillum marine sponge spicules using non-invasive Brillouin and Raman laser light scattering, thus probing the hierarchical structure on two very different scales. On the scale of single bonds, as probed by Raman scattering, the spicules resemble a combination of pure silica and mixed organic content. On the mesoscopic scale probed by Brillouin scattering, we show that while some properties (Young's moduli, shear moduli, one of the anisotropic Poisson ratios and refractive index) are nearly the same as those of artificial optical fiber, other properties (uniaxial moduli, bulk modulus and a distinctive anisotropic Poisson ratio) are significantly smaller. Thus this natural composite of largely isotropic materials yields anisotropic elastic properties on the mesoscale. We show that the spicules' optical waveguide properties lead to pronounced spontaneous Brillouin backscattering, a process related to the stimulated Brillouin backscattering process well known in artificial glass fibers. These measurements provide a clearer picture of the interplay of flexibility, strength, and material microstructure for future functional biomimicry. PMID:26672719
Weld stresses beyond elastic limit: Materials discontinuity
NASA Technical Reports Server (NTRS)
Verderaime, V.
1989-01-01
When welded structures depend on properties beyond the elastic limit to qualify their ultimate safety factor, and weld-parent materials abruptly change at the interface, then stress discontinuity is inevitable. The stress concentration is mildly sensitive to material relative strain hardening and acutely sensitive to applied stress fields. Peak stresses occur on the weld surface, at the interface, and dissipate within a 0.01-inch band. When the stress is intense, the weld will always fracture at the interface. The analysis incorporates a classical mechanics model to more sharply define stress spikes within the bandwidth, and suggests a relative material index and Poisson's ratio related to strain hardening. Implications are discussed which are applicable to industries of high performance structures.
Elastic and viscous properties of Silly Putty
NASA Astrophysics Data System (ADS)
Cross, Rod
2012-10-01
We consider in this paper the elastic and viscous properties of Silly Putty and confirm the well known fact that the properties depend on the rate at which the material is deformed. Rapid deformations were studied by dropping masses onto one end of a Silly Putty cylinder, and slow deformations were studied by compressing the cylinder in a materials testing machine. The results were compared with a simple engineering model of viscoelastic materials to estimate the stiffness and the viscosity of the Silly Putty cylinder. It was found that stress induced in Silly Putty relaxes with a time constant of about 0.1 s, Young's modulus for a rapid deformation is about 1.7 × 106 N/m2, and the viscosity for a slow compression is about 8 × 104 Pa s. When subject to a short impact, Silly Putty vibrates as a result of compressional wave propagation through the material.
Single-Crystal Elasticity of Earth Materials: An Appraisal
NASA Astrophysics Data System (ADS)
Duffy, T. S.
2015-12-01
The elastic properties of minerals are of central importance for interpreting seismic data for the Earth's crust, mantle, and core. Mineral elasticity data also have more general applications towards understanding equations of state, phase equilibria, interatomic forces, material strength, and phase transitions. The singe-crystal elastic properties are the most generally useful as they provide complete information on the anisotropy of elastic moduli (e.g. Poisson's ratio, Young's modulus), sound velocities, and compressibility. Measurement of the full set of single-crystal elastic properties remains challenging especially for lower symmetry crystals. In this talk, I present an overview of our current understanding of single-crystal elasticity based on a newly constructed database of single-crystal elastic properties. At ambient conditions the full elastic tensor of about 150 minerals have now been measured, along with about another 60 related compounds that are not formally minerals. About two-thirds of the measured minerals are oxides or silicates. A limitation of the existing database is that only about 10% of the measurements are on crystals of monoclinic or triclinic symmetry, while these two systems account for about 40% of known minerals. Additionally, only a smaller subset of minerals have been examined at high pressure or temperature conditions. Several applications of the database will be presented emphasizing trends in elastic anisotropy. The pyroxenes will be used as an illustrative example.
Visco elasticity in 2D materials
NASA Astrophysics Data System (ADS)
Cortijo, Alberto; Ferreirós, Yago; Landsteiner, Karl; Vozmediano, María A. H.
2016-03-01
The combination of Dirac physics and elasticity has been explored at length in graphene where the so-called ‘elastic gauge fields’ have given rise to an entire new field of research and applications: straintronics. The fact that these elastic fields couple to fermions as the electromagnetic field, implies that many electromagnetic responses will have elastic counterparts not yet explored. In this work we will first show that the presence of elastic gauge fields is the rule rather than the exception in most of the topologically non-trivial materials in two- and three-dimensions. We will show that, associated to the physics of the anomalies, and as a counterpart of the Hall conductivity, elastic two-dimension materials will have a Hall viscosity with a coefficient orders of magnitude bigger than the previously studied response. The magnitude and generality of the new effect will greatly improve the chances for the experimental observation of this topological response.
Elastic properties of spherically anisotropic piezoelectric composites
NASA Astrophysics Data System (ADS)
Wei, En-Bo; Gu, Guo-Qing; Poon, Ying-Ming
2010-09-01
Effective elastic properties of spherically anisotropic piezoelectric composites, whose spherically anisotropic piezoelectric inclusions are embedded in an infinite non-piezoelectric matrix, are theoretically investigated. Analytical solutions for the elastic displacements and the electric potentials under a uniform external strain are derived exactly. Taking into account of the coupling effects of elasticity, permittivity and piezoelectricity, the formula is derived for estimating the effective elastic properties based on the average field theory in the dilute limit. An elastic response mechanism is revealed, in which the effective elastic properties increase as inclusion piezoelectric properties increase and inclusion dielectric properties decrease. Moreover, a piezoelectric response mechanism, of which the effective piezoelectric response vanishes due to the symmetry of spherically anisotropic composite, is also disclosed.
NASA Astrophysics Data System (ADS)
Jeppson, T.; Tobin, H. J.
2014-12-01
The 11 March 2011 Tohoku-Oki earthquake (Mw=9.0) produced large displacements of ~50 meters near the Japan Trench. In order to understand earthquake propagation and slip stabilization in this environment, quantitative values of the real elastic properties of fault zones and their surrounding wall rock material is crucial. Because elastic and mechanical properties of faults and wallrocks are controlling factors in fault strength, earthquake generation and propagation, and slip stabilization, an understanding of these properties and their depth dependence is essential to understanding and accurately modeling earthquake rupture. In particular, quantitatively measured S-wave speeds, needed for estimation of elastic properties, are scarce in the literature. We report laboratory ultrasonic velocity measurements performed at elevated pressures, as well as the calculated dynamic elastic moduli, for samples of the rock surrounding the Tohoku earthquake principal fault zone recovered by drilling during IODP Expedition 343, Japan Trench Fast Drilling Project (JFAST). We performed measurements on five samples of gray mudstone from the hanging wall and one sample of underthrust brown mudstone from the footwall. We find P- and S-wave velocities of 2.0 to 2.4 km/s and 0.7 to 1.0 km/s, respectively, at 5 MPa effective pressure. At the same effective pressure, the hanging wall samples have shear moduli ranging from 1.4 to 2.2 GPa and the footwall sample has a shear modulus of 1.0 GPa. While these values are perhaps not surprising for shallow, clay-rich subduction zone sediments, they are substantially lower than the 30 GPa commonly assumed for rigidity in earthquake rupture and propagation models [e.g., Ide et al., 1993; Liu and Rice, 2005; Loveless and Meade, 2011]. In order to better understand the elastic properties of shallow subduction zone sediments, our measurements from the Japan Trench are compared to similar shallow drill core samples from the Nankai Trough, Costa Rica
Elastic properties of glasses: a multiscale approach
NASA Astrophysics Data System (ADS)
Rouxel, Tanguy
2006-12-01
Very different materials are named 'Glass', with Young's modulus E and Poisson's ratio ν extending from 5 to 180 GPa and from 0.1 to 0.4, respectively, in the case of bulk inorganic glasses. Glasses have in common the lack of long range order in the atomic organization. Beside the essential role of elastic properties for materials selection in mechanical design, we show in this analysis that macroscopical elastic characteristics ( E,ν) provide an interesting way to get insight into the short- and medium-range orders existing in glasses. In particular, ν, the packing density ( C) and the glass network dimensionality appear to be strongly correlated. Networks consisting primarily of chains and layers units (chalcogenides, low Si-content silicate glasses) correspond to ν>0.25 and C>0.56, with maximum values observed for metallic glasses ( ν˜0.4 and C>0.7). On the contrary, ν<0.25 is associated to a highly cross-linked network with a tri-dimensional organization resulting in a low packing density. Moreover, the temperature dependence of the elastic moduli brings a new light on the 'fragility' of glasses (as introduced by Angell) and on the level of cooperativity of atomic movements at the source of the deformation process. To cite this article: T. Rouxel, C. R. Mecanique 334 (2006).
Chen, Jiankang; Wang, Wencai; Wang, Ji; Yang, Zengtao; Yang, Jiashi
2008-08-01
We studied thickness vibration of 2 elastic layers with an elastic interface mounted on a plate piezoelectric resonator. The effect of the interface elasticity on resonant frequencies was examined. The result obtained suggests an acoustic wave sensor for measuring the elastic property of an interface between 2 materials. PMID:18986911
Homogenization of Heterogeneous Elastic Materials with Applications to Seismic Anisotropy
NASA Astrophysics Data System (ADS)
Vel, S. S.; Johnson, S. E.; Okaya, D. A.; Cook, A. C.
2014-12-01
The velocities of seismic waves passing through a complex Earth volume can be influenced by heterogeneities at length scales shorter than the seismic wavelength. As such, seismic wave propagation analyses can be performed by replacing the actual Earth volume by a homogeneous i.e., "effective", elastic medium. Homogenization refers to the process by which the elastic stiffness tensor of the effective medium is "averaged" from the elastic properties, orientations, modal proportions and spatial distributions of the finer heterogeneities. When computing the homogenized properties of a heterogeneous material, the goal is to compute an effective or bulk elastic stiffness tensor that relates the average stresses to the average strains in the material. Tensor averaging schemes such as the Voigt and Reuss methods are based on certain simplifying assumptions. The Voigt method assumes spatially uniform strains while the Reuss method assumes spatially uniform stresses within the heterogeneous material. Although they are both physically unrealistic, they provide upper and lower bounds for the actual homogenized elastic stiffness tensor. In order to more precisely determine the homogenized stiffness tensor, the stress and strain distributions must be computed by solving the three-dimensional equations of elasticity over the heterogeneous region. Asymptotic expansion homogenization (AEH) is one such structure-based approach for the comprehensive micromechanical analysis of heterogeneous materials. Unlike modal volume methods, the AEH method takes into account how geometrical orientation and alignment can increase elastic stiffness in certain directions. We use the AEH method in conjunction with finite element analysis to calculate the bulk elastic stiffnesses of heterogeneous materials. In our presentation, wave speeds computed using the AEH method are compared with those generated using stiffness tensors derived from commonly-used analytical estimates. The method is illustrated
Introduction to physical properties and elasticity models: Chapter 20
Dvorkin, Jack; Helgerud, Michael B.; Waite, William F.; Kirby, Stephen H.; Nur, Amos
2003-01-01
Estimating the in situ methane hydrate volume from seismic surveys requires knowledge of the rock physics relations between wave speeds and elastic moduli in hydrate/sediment mixtures. The elastic moduli of hydrate/sediment mixtures depend on the elastic properties of the individual sedimentary particles and the manner in which they are arranged. In this chapter, we present some rock physics data currently available from literature. The unreferenced values in Table I were not measured directly, but were derived from other values in Tables I and II using standard relationships between elastic properties for homogeneous, isotropic material. These derivations allow us to extend the list of physical property estimates, but at the expense of introducing uncertainties due to combining property values measured under different physical conditions. This is most apparent in the case of structure II (sII) hydrate for which very few physical properties have been measured under identical conditions.
Elastic properties of suspended multilayer WSe2
NASA Astrophysics Data System (ADS)
Zhang, Rui; Koutsos, Vasileios; Cheung, Rebecca
2016-01-01
We report the experimental determination of the elastic properties of suspended multilayer WSe2, a promising two-dimensional (2D) semiconducting material combined with high optical quality. The suspended WSe2 membranes have been fabricated by mechanical exfoliation of bulk WSe2 and transfer of the exfoliated multilayer WSe2 flakes onto SiO2/Si substrates pre-patterned with hole arrays. Then, indentation experiments have been performed on these membranes with an atomic force microscope. The results show that the 2D elastic modulus of the multilayer WSe2 membranes increases linearly while the prestress decreases linearly as the number of layers increases. The interlayer interaction in WSe2 has been observed to be strong enough to prevent the interlayer sliding during the indentation experiments. The Young's modulus of multilayer WSe2 (167.3 ± 6.7 GPa) is statistically independent of the thickness of the membranes, whose value is about two thirds of other most investigated 2D semiconducting transition metal dichalcogenides, namely, MoS2 and WS2. Moreover, the multilayer WSe2 can endure ˜12.4 GPa stress and ˜7.3% strain without fracture or mechanical degradation. The 2D WSe2 can be an attractive semiconducting material for application in flexible optoelectronic devices and nano-electromechanical systems.
Elastic Properties of Sedimentary Rocks
NASA Astrophysics Data System (ADS)
Melendez Martinez, Jaime
Sedimentary rocks are an important research topic since such rocks are associated to sources of ground water as well as oil, gas, and mineral reservoirs. In this work, elastic and physical properties of a variety of sedimentary samples that include glacial sediments, carbonates, shales, one evaporite, and one argillite from a variety of locations are investigated. Assuming vertical transverse isotropy, ultrasonic compressional- and shear-waves (at 1 MHz central frequency) were measured as a function of confining pressure on all samples with the exception of glacial samples which were tested assuming isotropy. Tensile strength tests (Brazilian test) were also carried out on selected glacial samples and, in addition, static-train measurements were conducted on shales and argillite samples. Lithological and textural features of samples were obtained through thin section techniques, scanning electron microscopy images and micro-tomography images. X-ray diffraction and X-Ray fluorescence provided the mineralogical oxides content information. Porosity, density, and pore structure were studied by using a mercury intrusion porosimeter and a helium pycnometer. The wide range of porosities of the studied samples (ranging from a minimum of 1% for shales to a maximum 45% for some glacial sediments) influence the measured velocities since high porosity sample shows an noticeable velocity increment as confining pressure increases as a consequence of closure of microcracks and pores, unlike low porosity samples where increment is quasi-lineal. Implementation of Gassmann's relation to ultrasonic velocities obtained from glacial samples has negligible impact on them when assuming water saturated samples, which suggests that state of saturation it is no so important in defining such velocities and instead they are mainly frame-controlled. On the other hand, velocities measured on carbonate and evaporite samples show that samples are at best weak anisotropic, thus the intrinsic
Statistical properties of a folded elastic rod
NASA Astrophysics Data System (ADS)
Bayart, Elsa; Deboeuf, Stéphanie; Boué, Laurent; Corson, Francis; Boudaoud, Arezki; Adda-Bedia, Mokhtar
2010-03-01
A large variety of elastic structures naturally seem to be confined into environments too small to accommodate them; the geometry of folded structures span a wide range of length-scales. The elastic properties of these confined systems are further constrained by self-avoidance as well as by the dimensionality of both structures and container. To mimic crumpled paper, we devised an experimental setup to study the packing of a dimensional elastic object in 2D geometries: an elastic rod is folded at the center of a circular Hele-Shaw cell by a centripetal force. The initial configuration of the rod and the acceleration of the rotating disk allow to span different final folded configurations while the final rotation speed controls the packing intensity. Using image analysis we measure geometrical and mechanical properties of the folded configurations, focusing on length, curvature and energy distributions.
Anisotropic linear elastic properties of fractal-like composites.
Carpinteri, Alberto; Cornetti, Pietro; Pugno, Nicola; Sapora, Alberto
2010-11-01
In this work, the anisotropic linear elastic properties of two-phase composite materials, made up of square inclusions embedded in a matrix, are investigated. The inclusions present a fractal hierarchical distribution and are supposed to have the same Poisson's ratio as the matrix but a different Young's modulus. The effective elastic moduli of the medium are computed at each fractal iteration by coupling a position-space renormalization-group technique with a finite element analysis. The study allows to obtain and generalize some fundamental properties of fractal composite materials. PMID:21230552
Petrova, A. E.; Krasnorussky, V. N.; Stishov, S. M.
2010-09-15
Measurements of the sound velocities in a single crystal of FeSi were performed in the temperature range 4-300 K. Elastic constants C{sub 11} and C{sub 44} deviate from a quasiharmonic behavior at high temperature; on the other hand, elastic constants C{sub 12} increases anomalously in the entire temperature range, indicating a change in the electron structure of this material.
Elasticity of fractal materials using the continuum model with non-integer dimensional space
NASA Astrophysics Data System (ADS)
Tarasov, Vasily E.
2015-01-01
Using a generalization of vector calculus for space with non-integer dimension, we consider elastic properties of fractal materials. Fractal materials are described by continuum models with non-integer dimensional space. A generalization of elasticity equations for non-integer dimensional space, and its solutions for the equilibrium case of fractal materials are suggested. Elasticity problems for fractal hollow ball and cylindrical fractal elastic pipe with inside and outside pressures, for rotating cylindrical fractal pipe, for gradient elasticity and thermoelasticity of fractal materials are solved.
Charting the complete elastic properties of inorganic crystalline compounds
de Jong, Maarten; Chen, Wei; Angsten, Thomas; Jain, Anubhav; Notestine, Randy; Gamst, Anthony; Sluiter, Marcel; Krishna Ande, Chaitanya; van der Zwaag, Sybrand; Plata, Jose J; Toher, Cormac; Curtarolo, Stefano; Ceder, Gerbrand; Persson, Kristin A.; Asta, Mark
2015-01-01
The elastic constant tensor of an inorganic compound provides a complete description of the response of the material to external stresses in the elastic limit. It thus provides fundamental insight into the nature of the bonding in the material, and it is known to correlate with many mechanical properties. Despite the importance of the elastic constant tensor, it has been measured for a very small fraction of all known inorganic compounds, a situation that limits the ability of materials scientists to develop new materials with targeted mechanical responses. To address this deficiency, we present here the largest database of calculated elastic properties for inorganic compounds to date. The database currently contains full elastic information for 1,181 inorganic compounds, and this number is growing steadily. The methods used to develop the database are described, as are results of tests that establish the accuracy of the data. In addition, we document the database format and describe the different ways it can be accessed and analyzed in efforts related to materials discovery and design. PMID:25984348
NASA Astrophysics Data System (ADS)
Djellab, Sihem; Bouhadda, Youcef; Bououdina, Mohamed; Fenineche, Noureddine; Boudouma, Youcef
2016-08-01
The structural, electronic and elastic properties of MgH2, CaH2 and Ca4Mg3H14 have been determined using first principles calculation based on density functional theory. The calculated lattice constants were in good agreement with the experimental values. The electronic density of states revealed that these hydrides are insulators. The calculated elastic constants of MgH2, CaH2 and Ca4Mg3H14 indicated that these hydrides are mechanically stable at zero pressure. The bulk modulus B, shear modulus G, Young's modulus E, and Poisson's ratio ν were derived, and the ductility was discussed.
Magnetodeformation and elastic properties of ferrogels and ferroelastomers
NASA Astrophysics Data System (ADS)
Zubarev, A. Yu.; Elkady, Ashraf S.
2014-11-01
The work deals with a theoretical study of magnetoelastic properties of soft composite materials, consisting of a polymer matrix filled with micron-sized magnetizable particles (ferrogels and ferroelastomers). The systems with a homogeneous gas-like spatial distribution of particles in the matrix are considered. The impact of the particles magnetic interaction on the macroscopic elastic characteristics of the composites is studied. Analysis shows that this interaction increases elastic moduli of the materials. This effect must be especially significant for the composites with soft gel matrix.
Elastic properties of suspended black phosphorus nanosheets
NASA Astrophysics Data System (ADS)
Wang, Jia-Ying; Li, Yang; Zhan, Zhao-Yao; Li, Tie; Zhen, Liang; Xu, Cheng-Yan
2016-01-01
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.
Elastic Properties of Plasticine, Silly Putty, and Tennis Strings
NASA Astrophysics Data System (ADS)
Cross, Rod
2012-12-01
How would a physicist describe the elastic properties of an apple or a banana? Physics students and teachers are familiar with the elastic properties of metal springs, but are likely to be less familiar with the elastic properties of other common materials. The behavior of a metal spring is commonly examined in the laboratory by adding masses to measure the change in the extension or compression. A banana or an apple or any other relatively soft material could just as easily be examined in the same way, as an additional and entertaining exercise. Even if an apparatus is not readily available to undertake such an experiment, it can easily be constructed.1,2 In this article I compare the elastic properties of Plasticine (a brand of modeling clay), Silly Putty, and tennis strings. All three materials behave in the same qualitative manner when stretched or compressed slowly, despite the fact that they are quite different when stretched or compressed rapidly and despite the fact that Plasticine and Silly Putty are both much softer than a tennis string. Typical results for a slow deformation are shown in Fig. 1.
NASA Astrophysics Data System (ADS)
Vincent, Abhilash
Due to their therapeutic applications such as radical scavenging, MRI contrast imaging, Photoluminescence imaging, drug delivery, etc., nanoparticles (NPs) have a significant importance in bio-nanotechnology. The reason that prevents the utilizing NPs for drug delivery in medical field is mostly due to their biocompatibility issues (incompatibility can lead to toxicity and cell death). Changes in the surface conditions of NPs often lead to NP cytotoxicity. Investigating the role of NP surface properties (surface charges and surface chemistry) on their interactions with biomolecules (Cells, protein and DNA) could enhance the current understanding of NP cytotoxicity. Hence, it is highly beneficial to the nanotechnology community to bring more attention towards the enhancement of surface properties of NPs to make them more biocompatible and less toxic to biological systems. Surface functionalization of NPs using specific ligand biomolecules have shown to enhance the protein adsorption and cellular uptake through more favorable interaction pathways. Cerium oxide NPs (CNPs also known as nanoceria) are potential antioxidants in cell culture models and understanding the nature of interaction between cerium oxide NPs and biological proteins and cells are important due to their therapeutic application (especially in site specific drug delivery systems). The surface charges and surface chemistry of CNPs play a major role in protein adsorption and cellular uptake. Hence, by tuning the surface charges and by selecting proper functional molecules on the surface, CNPs exhibiting strong adhesion to biological materials can be prepared. By probing the nanoscale interaction forces acting between CNPs and protein molecules using Atomic Force Microscopy (AFM) based force-distance (F-D) spectroscopy, the mechanism of CNP-protein adsorption and CNP cellular uptake can be understood more quantitatively. The work presented in this dissertation is based on the application of AFM in
Elastic properties of magnetosome chains
NASA Astrophysics Data System (ADS)
Kiani, Bahareh; Faivre, Damien; Klumpp, Stefan
2015-04-01
Magnetotactic bacteria swim and orient in the direction of a magnetic field thanks to the magnetosome chain, a cellular ‘compass needle’ that consists of a string of vesicle-enclosed magnetic nanoparticles aligned on a cytoskeletal filament. Here we investigate the mechanical properties of such a chain, in particular the bending stiffness. We determine the contribution of magnetic interactions to the bending stiffness and the persistence length of the chain. This contribution is comparable to, but typically smaller than the contribution of the semiflexible filament. For a chain of magnetic nanoparticles without a semiflexible filament, the linear configuration is typically metastable and the lowest energy structures are closed chains (flux closure rings) without a net magnetic moment that are thus not functional as a cellular compass. Our calculations show that the presence of the cytoskeletal filament stabilizes the chain against ring closure, either thermodynamically or kinetically, depending on the stiffness of the filament, confirming that such stabilization is one of the roles of this structure in these bacterial cells.
Elastic Properties of Clay Minerals
NASA Astrophysics Data System (ADS)
Vanorio, T.; Prasad, M.; Nur, A.
2001-12-01
We present ultrasonic P- and S-waves velocity measurements on pure clay samples using three different experiment setups. These experiments provided petrophysical and acoustic properties of clay minerals as a function both of mineralogy and compaction. In the first experiment, acoustic measurements were performed on cold-pressed clay aggregates at ambient and at hydrostatic pressure conditions. Porosity and grain density values of the different clay mineralogy aggregates ranged from 4 to 43% and 2.13 to 2.83 g cm-3, respectively. In the second experiment, we measured P-wave velocity and attenuation in a kaolinite-water suspension in which clay concentration was increased up to 60%. In the third experiment, P- and S- wave velocities were measured during uniaxial stress compaction of clay powders. Results from all three experiments revealed low bulk (K) and shear (μ ) moduli for kaolinite, montmorillonite, and smectite; the values range between 6-12 GPa for K and 4-6 GPa for μ , respectively. Using these clay moduli values in effective medium and granular porous media models, velocity is predicted in saturated pure kaolinite samples, kaolinite suspension and shaly sandstones fairly well. Experimental results also showed that water interlayers play an important role in the compaction and strength of clay aggregates. Clay minerals carrying on water interlayers in their structure showed high compaction and strength. This study is relevant for a more reliable assessment of the seismic response in reservoirs and/or basins characterized by clay-bearing formations.
Elastic Properties of Clay Minerals
NASA Astrophysics Data System (ADS)
Vanorio, T.; Prasad, M.; Nur, A.
We present ultrasonic P- and S-waves velocity measurements on pure clay samples us- ing three different experiment setups. These experiments provided petrophysical and acoustic properties of clay minerals as a function both of mineralogy and compaction. In the first experiment, acoustic measurements were performed on cold-pressed clay aggregates at ambient and at hydrostatic pressure conditions. Porosity and grain den- sity values of the different clay mineralogy aggregates ranged from 4 to 43% and 2.13 to 2.83 g cm-3, respectively. In the second experiment, we measured P-wave velocity and attenuation in a kaolinite-water suspension in which clay concentration was in- creased up to 60%. In the third experiment, P- and S- wave velocities were measured during uniaxial stress compaction of clay powders. Results from all three experiments revealed low bulk (K) and shear (µ) moduli for kaolinite, montmorillonite, and smec- tite; the values range between 6-12 GPa for K and 4-6 GPa for µ, respectively. Using these clay moduli values in effective medium and granular porous media (theories) models, velocity is predicted in saturated pure kaolinite samples, kaolinite suspension and shaly sandstone fairly well. Experimental results also showed that water interlay- ers play an important role in the compaction and strength of clay aggregates. Clay minerals carrying on water interlayers in their structure showed high compaction and strength. This study is relevant for a more reliable assessment of the seismic response in reservoirs and/or basins characterized by clay-bearing formations.
Membrane Elastic Properties and Cell Function
Pontes, Bruno; Ayala, Yareni; Fonseca, Anna Carolina C.; Romão, Luciana F.; Amaral, Racκele F.; Salgado, Leonardo T.; Lima, Flavia R.; Farina, Marcos; Viana, Nathan B.; Moura-Neto, Vivaldo; Nussenzveig, H. Moysés
2013-01-01
Recent studies indicate that the cell membrane, interacting with its attached cytoskeleton, is an important regulator of cell function, exerting and responding to forces. We investigate this relationship by looking for connections between cell membrane elastic properties, especially surface tension and bending modulus, and cell function. Those properties are measured by pulling tethers from the cell membrane with optical tweezers. Their values are determined for all major cell types of the central nervous system, as well as for macrophage. Astrocytes and glioblastoma cells, which are considerably more dynamic than neurons, have substantially larger surface tensions. Resting microglia, which continually scan their environment through motility and protrusions, have the highest elastic constants, with values similar to those for resting macrophage. For both microglia and macrophage, we find a sharp softening of bending modulus between their resting and activated forms, which is very advantageous for their acquisition of phagocytic functions upon activation. We also determine the elastic constants of pure cell membrane, with no attached cytoskeleton. For all cell types, the presence of F-actin within tethers, contrary to conventional wisdom, is confirmed. Our findings suggest the existence of a close connection between membrane elastic constants and cell function. PMID:23844071
NASA Astrophysics Data System (ADS)
Levin, V.; Petronyuk, Yu.; Morokov, E.; Chernozatonskii, L.; Kuzhir, P.; Fierro, V.; Celzard, A.; Bellucci, S.; Bistarelli, S.; Mastrucci, M.; Tabacchioni, I.
2016-05-01
Bulk microstructure and elastic properties of epoxy-nanocarbon nanocomposites for diverse types and different content of carbon nanofiller has been studied by using impulse acoustic microscopy technique. It has been shown occurrence of various types of mesoscopic structure formed by nanoparticles inside the bulk of nanocomposite materials, including nanoparticle conglomerates and nanoparticle aerogel systems. In spite of the bulk microstructure, nanocarbon composites demonstrate elastic uniformity and negligible influence of nanofiller on elastic properties of carbon nanocomposite materials.
NASA Astrophysics Data System (ADS)
Knuth, M. W.; Tobin, H. J.; Marone, C.; Saffer, D. M.; Hashimoto, Y.
2009-12-01
We present results of ultrasonic P and S-wave velocity measurements on core material recovered during NanTroSEIZE Stage 1 Expeditions 315 and 316 to the Nankai Trough Accretionary Margin, focusing on how different stress paths during subduction and exhumation along regional thrust faults influence the elastic moduli and anisotropy of various components of the accretionary prism. The influence of changes in pore pressure and confining pressure on the elastic properties of prism material has important implications for its mechanical strength, and understanding how elastic properties change along various stress paths will help us use 3D seismic tomography to draw inferences about overpressurization and fluid flow within the accretionary prism. We compare the velocities measured during shipboard physical properties characterization and logging-while-drilling data from Expedition 314 with 3D seismic velocity data and the results of previous shore-based studies to establish in situ conditions for material at various locations within the prism. We test both intact core material and disaggregated gouge and unlithified sediments from the upper prism, subjecting both samples types to a progression of confining pressure, pore pressure, and axial loading conditions representing normal consolidation and overconsolidation stress paths due to compaction and dewatering during burial and subsequent uplift by thrust faulting. While making continuous ultrasonic velocity measurements to determine changes in dynamic and quasistatic elastic moduli during axial and isotropic loading, we also subject granular material to frictional shear in a biaxial double-direct shearing configuration to measure how its frictional properties vary as a function of stress history.
Crystal Structure Anisotropy Explains Anomalous Elastic Properties of Metal Nanorods
NASA Astrophysics Data System (ADS)
Goupalov, Serguei
2014-03-01
It is demonstrated that the frequency of the extensional vibrational mode of a nanorod made of an elastically anisotropic crystalline material deviates widely from the predictions of the theories based on the analysis of the long-wavelength limit. The dispersion relation for the fundamental extensional mode of a gold rod grown in the [ 100 ] direction is calculated and found to be in an excellent agreement with experimental data obtained from the transient optical absorption measurements on gold nanorods.[1] This explains an anomaly in the elastic properties of nanorods which was previously attributed to a 26% decrease in Young's modulus for nanorods compared to its bulk value.
Linear elastic properties derivation from microstructures representative of transport parameters.
Hoang, Minh Tan; Bonnet, Guy; Tuan Luu, Hoang; Perrot, Camille
2014-06-01
It is shown that three-dimensional periodic unit cells (3D PUC) representative of transport parameters involved in the description of long wavelength acoustic wave propagation and dissipation through real foam samples may also be used as a standpoint to estimate their macroscopic linear elastic properties. Application of the model yields quantitative agreement between numerical homogenization results, available literature data, and experiments. Key contributions of this work include recognizing the importance of membranes and properties of the base material for the physics of elasticity. The results of this paper demonstrate that a 3D PUC may be used to understand and predict not only the sound absorbing properties of porous materials but also their transmission loss, which is critical for sound insulation problems. PMID:24907783
Interface waves in almost incompressible elastic materials
NASA Astrophysics Data System (ADS)
Virta, Kristoffer; Kreiss, Gunilla
2015-12-01
We study the problem of two elastic half-planes in contact and the Stoneley interface wave that may exist at the interface between two different elastic materials, emphasis being put on the case when the half-planes are almost incompressible. We show that numerical simulations involving interface waves require an unexpectedly high number of grid points per wavelength as the materials become more incompressible. Let λ, μ, ρ and λ‧, μ‧, ρ‧ be the Lamé parameters and densities of the first and second half-plane, respectively. A theoretical study shows that if K is a real constant, λ‧ = Kλ, μ‧ = Kμ, ρ‧ = Kρ and μ → 0, then for an accurate solution the required number of grid points per wavelength scales as (μ / λ) - 1 / p, where p is the order of accuracy of the numerical method. This requirement becomes very restrictive close to the incompressible limit μ ≪ λ, especially for lower order methods i.e., a small p. The theoretical findings are supported by numerical experiments that illustrate the demanding resolution requirement as well as the superiority of higher order methods. The scaling is also seen to hold for a more general choice of Lamé parameters. Numerical experiments when one of the half-planes is a vacuum are also presented, where the higher resolution requirement is illustrated in a numerical solution of Lamb's problem.
Elastic properties of polycrystals—influence of texture and stereology
NASA Astrophysics Data System (ADS)
Bunge, H. J.; Kiewel, R.; Reinert, Th; Fritsche, L.
2000-01-01
The macroscopic elastic properties of polycrystalline materials depend on the elastic properties of the crystallites and the way how these are 'arranged' in the polycrystalline aggregate. This comprises the volume fraction of crystal orientations (texture) as well as their arrangement in space (stereology). It is estimated that the stereological aggregate parameters may contribute up to 25% of the maximum texture influence. Model calculations of the effective macroscopic elastic properties were carried out using a grain cluster model which is a finite discretization of the aggregate function g( x) describing the complete 'orientation-stereology' of the polycrystalline material. The most important stereological parameters influencing the effective elastic constants are grain shape expressed by two axis ratios, grain packing expressed by the space filling factor of the lattice of grain centres and orientation pair correlation of neighbouring grains expressed by the misorientation distribution function. By rotating the orientation of only one grain it can be shown that grain interaction strains decrease rapidly and may be neglected beyond the second order neighbours.
Measuring Elastic Properties of Thin Biological Films Using Capillary Wrinkling
NASA Astrophysics Data System (ADS)
Iyer, N.; Cooper, K.; Yang, J.; Zenhausern, F.
2008-08-01
Imprinting of soft biological cells to create microenvironments for cell culture has gained significant importance in studying biological processes. Developments in soft lithography techniques have caused a decrease in the size of these imprinted biological cells. Where pattern sizes were in the range of 50 um, they are now being fabricated in the range of 1 um. However, there has been very little work done to characterize the elastic properties of these imprinted gels at this scale. In this work, we attempt to use an unique technique that uses the wrinkling that occurs when a floating thin film is subject to a normal loading force. A previous study has reported the use of this metrology method to measure elastic properties of floating thin polystyrene films by counting the number and length of wrinkles that are created when subjected to radial stresses from a droplet of water. In this case, we extend this theory to study wrinkle formation in floating polystyrene films coated with biological cells, and fibronectin. Also, we attempt to study capillary wrinkling in biological films such as agarose and Matrigel™. Wrinkles are induced in thin films of these materials by applying a droplet of fluid on the film surface. Using an appropriate scaling relationship, the elastic properties of these films may be obtained. The dependence of these elastic properties on gel aspect ratios, concentration, and, film floating media will be discussed.
Elastic properties of hollow colloidal particles
NASA Astrophysics Data System (ADS)
Zoldesi, C. I.; Ivanovska, I. L.; Quilliet, C.; Wuite, G. J. L.; Imhof, A.
2008-11-01
The elastic properties of micrometer-sized hollow colloidal particles obtained by emulsion templating are probed by nanoindentation measurements in which point forces are applied to solvent-filled particles supported on a flat substrate. We show that the shells respond linearly up to forces of 7-21nN , where the indentation becomes of the order of the shell thickness (20-40nm) . In the linear region, the particle deformation is reversible. The measured Young’s modulus (˜200MPa) is comparable to values for stiff rubbers or soft polymers. At larger applied force, we observe a crossover into a nonlinear regime, where the shells assume a buckled shape. Here, the force increases approximately as the square root of the indentation, in agreement with the theory of elasticity of thin shells. We also observe permanent deformation of the shells after probing them repetitively beyond the linear regime. Finally, the measured elastic properties of the shells nicely explain their spontaneous buckling in solution and due to drying.
Elastic properties of alkali-feldspars
NASA Astrophysics Data System (ADS)
Waeselmann, N.; Brown, J.; Angel, R. J.; Ross, N.; Kaminsky, W.
2013-12-01
New measurements of single crystal elastic moduli for a suite of the alkali feldspars are reported. In order to interpret Earth's seismic structure, knowledge of the elastic properties of constituent minerals is essential. The elasticity of feldspar minerals, despite being the most abundant phase in Earth's crust (estimated to be more than 60%), were previously poorly characterized. All prior seismic and petrologic studies have utilized 50-year-old results, of questionable quality, based on 1-bar measurements on pseudo-single crystals. Alkali-feldspars present a large experimental challenge associated with their structural complexity. In the K-end member (KAlSi3O8) the symmetry is governed by Al/Si ordering, in the Na-end member (NaAlSi3O8) the symmetry is governed by whether or not there is a displacive collapse of the framework independent of the Al/Si ordering. K-feldspars exhibit monoclinic (C2/m) symmetry (necessitating determination of 13 elastic moduli) if disordered and triclinic (C-1) symmetry (21 elastic moduli) if ordered. Exsolution of Na-rich and K-rich phases is ubiquitous in natural samples, making it difficult to find suitable single phase and untwinned samples for study. The small single domain samples selected for this study were previously characterized by x-ray diffraction and microprobe analysis to ensure adequate sample quality. Surface wave velocities were measured on oriented surfaces of natural and synthetic single crystals using impulsively stimulated light scattering. A surface corrugation with a spacing of about 2 microns was impulsively created by the overlap of 100 ps infrared light pulses. The time evolution of the stimulated standing elastic waves was detected by measuring the intensity of diffraction from the surface corrugation of a variably delayed probe pulse. This method allows accurate (better than 0.2%) determination of velocities on samples smaller than 100 microns. The combination of measured surface wave velocities and
Perreard, I M; Pattison, A J; Doyley, M; McGarry, M D J; Barani, Z; Van Houten, E E; Weaver, J B; Paulsen, K D
2013-01-01
The mechanical model commonly used in magnetic resonance elastography (MRE) is linear elasticity. However, soft tissue may exhibit frequency-and direction-dependent (FDD) shear moduli in response to an induced excitation causing a purely linear elastic model to provide an inaccurate image reconstruction of its mechanical properties. The goal of this study was to characterize the effects of reconstructing FDD data using a linear elastic inversion (LEI) algorithm. Linear and FDD phantoms were manufactured and LEI images were obtained from time-harmonic MRE acquisitions with variations in frequency and driving signal amplitude. LEI responses to artificially imposed uniform phase shifts in the displacement data from both purely linear elastic and FDD phantoms were also evaluated. Of the variety of FDD phantoms considered, LEI appeared to tolerate viscoelastic data-model mismatch better than deviations caused by poroelastic and anisotropic mechanical properties in terms of visual image contrast. However, the estimated shear modulus values were substantially incorrect relative to independent mechanical measurements even in the successful viscoelastic cases and the variations in mean values with changes in experimental conditions associated with uniform phase shifts, driving signal frequency and amplitude were unpredictable. Overall, use of LEI to reconstruct data acquired in phantoms with FDD material properties provided biased results under the best conditions and significant artifacts in the worst cases. These findings suggest that the success with which LEI is applied to MRE data in tissue will depend on the underlying mechanical characteristics of the tissues and/or organs systems of clinical interest. PMID:21030746
Oxides and oxide superconductors: Elastic and related properties
Lei, M.; Ledbetter, H.
1991-08-01
Using both measurements and modeling, the elastic and related properties of some oxides and oxide superconductors were studied. The polycrystal elastic constants were measured using a MHz-frequency pulse-echo method between 295 and 4 K and corrected to the void-free state by using a model for a composite material containing spherical particles. The elastic moduli of the high-T(c) superconductor Y1Ba2Cu3O7 (YBCO) were compared with that of oxides, especially the perovskites BaTiO3 and SrTiO3, which are crystal-structure building blocks for the YBCO superconductor. The bulk moduli were also calculated using a Born ionic model with two energy terms: electrostatic (Madelung) and ion-core-repulsion. The calculated bulk modulus of YBCO, 98 GPa, agrees well with measurement, 101 GPa. Based on monocrystal measurements combined with analysis-theory, elastic stiffnesses C(ij) for orthorhombic YBCO were estimated. The bulk modulus obtained from the estimated C(ij) by the Voigt-Reuss-Hill averaging method agrees with the monocrystal measurement. From the measured polycrystalline elastic constants, the Debye characteristic temperatures were calculated.
Learning targeted materials properties from data
NASA Astrophysics Data System (ADS)
Lookman, Turab; Balachandran, Prasanna V.; Dezhen, Xue; Theiler, James; Hogden, John
We compare several strategies using a data set of 223 M2AX family of compounds for which the elastic properties [bulk (B), shear (G), and Young's (E) modulus] have been computed using density functional theory. The strategy is decomposed into two steps: a regressor is trained to predict elastic properties in terms of elementary orbital radii of the individual components of the materials; and a selector uses these predictions to choose the next material to investigate. The ultimate goal is to obtain a material with desired elastic properties. We examine how the choice of data set size, regressor and selector impact the results.
NASA Astrophysics Data System (ADS)
Sava, Mihaela; Hadǎr, Anton; Pǎrǎuşanu, Ioan; Petrescu, Horia-Alexandru; Baciu, Florin; Marinel, Stǎnescu Marius
2016-06-01
The influence of discontinuities is important for a correct determination of static and dynamic elastic characteristics of the material. In this paper we presented differences arising between the elastic modulus static and dynamic, laminated composite materials reinforced with carbon fiber, aramid and carbon-aramid, depending on the non-uniformity coefficient. For the study were determined static elastic modulus by carrying out traction tests and dynamic elastic modulus by determining the vibration frequency, on specimens of each type of material with and without discontinuities [1]. The elastic properties of composite materials resistance and can be influenced by various defects that arise from technological manufacturing process. This is important for the production of large series of parts of fiber-reinforced composite material, the fibers in the matrix distribution is not uniform. Studies on the mechanical behavior of composites with random distribution of fabrics are made in [2].
Half-oxidized phosphorene: band gap and elastic properties modulation
NASA Astrophysics Data System (ADS)
Drissi, L. B.; Sadki, S.; Sadki, K.
2016-04-01
Based on a first principles approach, we study structural, electronic and elastic properties, as well as stabilities of all possible half-oxidized phosphorene conformers. Stability analysis reveals that oxygen chemisorption is an exothermic process in the six configurations despite the formation of interstitial oxygen bridges in three of them. Electronic structure calculations show that oxidation induces a band gap modulation ranging between 0.54 and 1.57 eV in the generalized gradient approximation corrected to 1.19 and 2.88 eV using GW. The mechanical response of the conformers is sensitively dependent on direction and indicates that the new derivatives are incompressible materials and one configuration has an auxetic behavior. The present results provide a basis for tailoring the electronic and elastic properties of phosphorene via half oxidation.
Half-oxidized phosphorene: band gap and elastic properties modulation.
Drissi, L B; Sadki, S; Sadki, K
2016-04-13
Based on a first principles approach, we study structural, electronic and elastic properties, as well as stabilities of all possible half-oxidized phosphorene conformers. Stability analysis reveals that oxygen chemisorption is an exothermic process in the six configurations despite the formation of interstitial oxygen bridges in three of them. Electronic structure calculations show that oxidation induces a band gap modulation ranging between 0.54 and 1.57 eV in the generalized gradient approximation corrected to 1.19 and 2.88 eV using GW. The mechanical response of the conformers is sensitively dependent on direction and indicates that the new derivatives are incompressible materials and one configuration has an auxetic behavior. The present results provide a basis for tailoring the electronic and elastic properties of phosphorene via half oxidation. PMID:26964522
Structural stability and elastic properties of prototypical covalent organic frameworks
NASA Astrophysics Data System (ADS)
Zhou, Wei; Wu, Hui; Yildirim, Taner
2010-10-01
We report the first investigation of the structural stabilities and elastic properties of covalent organic frameworks (COFs), a new class of porous crystalline materials. Representative 2D COFs were found to prefer shifted AA stacking, somewhat similar to graphite. The shear moduli of 2D COFs are exceedingly small, suggesting that the layer-layer coupling in 2D COFs is rather weak, and stacking faults may widely exist. Representative 3D COFs were found to exhibit relatively low elastic stiffness overall. In particular, COF-108, the least dense crystal known, exhibits rather low bulk and shear moduli. Our findings provide important structural and physical details to be considered in the further development of COF materials.
Busignies, Virginie; Mazel, Vincent; Diarra, Harona; Tchoreloff, Pierre
2013-11-30
The effect of the elasticity of various pharmaceutical materials on the interfacial adhesion in bilayer tablets was investigated. The elastic properties of five pharmaceutical products were characterized by their total elastic recovery. To test the interfacial strength of the bilayer tablets a new flexural test was proposed. Thanks to the test configuration, the experimental breaking force is directly correlated with the interfacial layer strength. Depending on the materials, the fracture occurred over the interface or in one of the two layers. In most cases, the highest breaking forces were obtained when the materials had close elastic recovery. On the contrary, for materials with different elastic recovery, the breaking forces were reduced. The observed changes in the interfacial mechanical strength were statistically analyzed. Such an approach has an importance in the growing interest in the Quality by Design (QbD) concept in pharmaceutical industry. PMID:24055440
The elastic properties of fractured rocks
NASA Astrophysics Data System (ADS)
Darcel, C.; Le Goc, R.; Davy, P.
2013-12-01
The consequences of fracturing on rock mass strength still remain an issue for rock engineering practices, including excavation or repository design, support design, slope stability and caving in mines. The difficulty is twice and concerns both the description of the fracturing pattern, and the relationship between fracture characteristics and rock mass mechanical properties. This is generally assessed by empirical knowledge but no complete quantitative and theoretical relations are yet established. To our knowledge, the only theoretical work was to found a relationship between the elastic strength and the percolation parameter (i.e. a normalized sum of the cube of fracture radius) for 3D frictionless fracture networks. The relationship has been demonstrated for Poissonian (randomly distributed) low-density (i.e. where fractures are not almost intersecting) networks, with a narrow range of fracture radius. By means of finite-element models and Green's function methods, we extend the analysis to fracture networks with geologically realistic geometry: i.e. non-Poissonian, relatively high densities, and power-law length distributions. The elastic strength of the fractured rock mass is still found to decrease exponentially with the percolation parameter on average. But large deviations from the mean exist for heavy tailed fracture length distribution, i.e. when the probability of having fractures of the order of the system size is no more negligible. We discuss the way to ameliorate the prediction by taking into account configuration details that are not described by statistical parameters.
Analysis of the Elastic Field in Functionally Graded Materials
NASA Astrophysics Data System (ADS)
Mohammadi, Mohsen
In this thesis, the elastic field in circular beams and pipes made of functionally graded materials is considered. The following aspects are presented. First, the thermoelastic stress field in a functionally graded curved beam, where the elastic stiffness varies in the radial direction, is considered. An analytical solution is obtained where the radial variation of the stiffness is represented by a fairly general form. The stress fields corresponding to two different cases for the elastic properties are examined. The flexural stress in the curved beam is then compared with that of a ring. A relatively simple approximate solution is then developed and this is shown to be in good agreement with the analytical results. Secondly, the effect of a nonconstant Poisson's ratio upon the elastic field in functionally graded axisymmetric solids is analyzed. Both of the elastic coefficients, i.e. Young's modulus and Poisson's ratio, are permitted to vary in the radial direction. These elastic coefficients are considered to be functions of composition and are related on this basis. This allows a closed form solution for the stress function to be obtained. Two cases are discussed in this investigation: a) both Young's modulus and Poisson's ratio are allowed to vary across the radius and the effect of spatial variation of Poisson's ratio upon the maximum radial displacement is investigated; b) Young's modulus is taken as constant and the change in the maximum hoop stress resulting from a variable Poisson's ratio is calculated. Thirdly, the stress concentration factor around a circular hole in an infinite plate subjected to uniform biaxial tension and pure shear is considered. The plate is made of a functionally graded material where both Young's modulus and Poisson's ratio vary in the radial direction. For plane stress conditions, the governing differential equation for the stress function is derived and solved. A general form for the stress concentration factor in case of
Elastic properties of liquid and solid argon in nanopores.
Schappert, Klaus; Pelster, Rolf
2013-10-16
We have measured sorption isotherms and determined the intrinsic longitudinal elastic modulus β(Ar,ads) of nanoconfined material via ultrasonic measurements combined with a special effective medium analysis. In the liquid regime the adsorbate only contributes to the measured effective properties when the pores are completely filled and the modulus is bulklike. At partial fillings its contribution is cancelled out by the high compressibility of the vapour phase. In contrast, at lower temperatures frozen argon as well as underlying liquid surface layers cause a linear increase of the effective longitudinal modulus upon filling. During sorption the contribution of the liquid surface layers near the pore wall β(Ar,surf) increases with the thickness of the solid layers reaching the bulk value β(Ar,liquid) only in the limit of complete pore filling. We interpret this effect as due to the gradual stiffening of the solid argon membrane. The measurements and their analysis show that longitudinal ultrasonic waves are well suited to the study of the elastic properties and liquid-solid phase transitions in porous systems. This method should also help to detect the influence of nanoconfinement on elastic properties in further research. PMID:24057946
Oxides and oxide superconductors: Elastic and related properties
Ming Lei.
1991-01-01
Using both measurements and modeling, the elastic and related properties of some oxides and oxide superconductors were studied. The polycrystal elastic constants were measured using a MHz-frequency pulse-echo method between 295 and 4 K and corrected to the void-free state by using a model for a composite material containing spherical particles. The elastic moduli of the high-{Tc} superconductor YBa{sub 2}Cu{sub 3}O{sub 7} (YBCO) were compared with that of oxides, especially the perovskites BaTiO{sub 3} and SrTiO{sub 3}, which are crystal-structure building blocks for the YBCO superconductor. The bulk moduli were also calculated using a Born ionic model with two energy terms: electrostatic (Madelung) and ion-core-repulsion. The calculated bulk modulus of YBCO, 98 GPa, agrees well with measurement, 101 GPa. Based on monocrystal measurements combined with analysis-theory, elastic stiffnesses C{sub ij} for orthorhombic YBCO were estimated. The bulk modulus obtained from the estimated C{sub ij} by the Voigt-Reuss-Hill averaging method agrees with the monocrystal measurement.
Bulk elastic fingering in soft materials
NASA Astrophysics Data System (ADS)
Saintyves, Baudouin; Biggins, John; Wei, Zhiyan; Bouchaud, Elisabeth; Mahadevan, L.; Harvard University Team; Ec2M/Espci Collaboration; Cambridge University Collaboration
2014-11-01
Systematic experiments have been performed in purely elastic polyacrylamide gels in Hele-Shaw cells. We have shown that a bulk fingering instability arises in the highly deformable confined elastomers. A systematic study shows that surface tension is not relevant. This instability is sub-critical, with a clear hysteretic behavior. Our experimental observations have been compared very favorably to theoretical and finite element simulations results. In particular, the instability wavelength and the critical front advance have been shown to be proportional to the distance between the two glass plates constituting the cell. A very important feature is that elasticity doesn't influence this lengthscale, making this instability very generic. We will also show some new results about an elastic counterpart experiment of the famous Saffman-Taylor experiment, where we push a soft gel in a stiff one.
Bulk Elastic Fingering in Soft Materials
NASA Astrophysics Data System (ADS)
Saintyves, Baudouin; Biggins, John; Wei, Zhiyan; Mora, Serge; Mahadevan, L.; Bouchaud, Elisabeth; Harvard University Team; Espci-Paristech Collaboration; Cambridge University Collaboration; Montpellier 2 University Collaboration
2015-03-01
Systematic experiments have been performed in purely elastic polyacrylamide gels in Hele-Shaw cells. We have shown that a bulk fingering instability arises in the highly deformable confined elastomers. A systematic study shows that surface tension is not relevant. This instability is sub-critical, with a clear hysteretic behavior. Our experimental observations have been compared very favorably to theoretical and finite element simulations results. In particular, the instability wavelength and the critical front advance have been shown to be proportional to the distance between the two glass plates constituting the cell. A very important feature is that elasticity doesn't influence this lengthscale, making this instability very generic. We will also show some new results about an elastic counterpart experiment of the famous Saffman-Taylor experiment, where we push a soft gel in a stiff one.
Elastic properties of solids at high pressure
NASA Astrophysics Data System (ADS)
Vekilov, Yu Kh; Krasilnikov, O. M.; Lugovskoy, A. V.
2015-11-01
This review examines the elastic response of solids under load. The definitions of isothermal and adiabatic elastic constants of ( n≥2) for a loaded crystal are given. For the case of hydrostatic pressure, two techniques are proposed for calculating the second-, third-, and fourth-order elastic constants from the energy-strain and stress-strain relations. As an example, using the proposed approach within the framework of the density functional theory, the second- to fourth-order elastic constants of bcc tungsten are calculated for the pressure range of 0-600 GPa.
Elastic and Acoustic Properties of Hexagonal Cr2Nb Compound
NASA Astrophysics Data System (ADS)
Yadawa, Pramod Kumar
2013-01-01
The ultrasonic properties like ultrasonic sound velocity in the hexagonal structured Cr2Nb compound have been studied along unique axis at room temperature. The second- and third-order elastic constants (SOECs and TOECs) have been calculated for this compound using Lennard-Jones potential. The velocities VL and VS1 have minima and maxima respectively with 45° with unique axis of the crystal, while VS2 increases with the angle from unique axis. Debye average sound velocities of Cr2Nb have been found to be increasing with the angle and has maximum at 55° with unique axis at room temperature. Hence, when a sound wave travels at 55° with unique axis of this material, then the average sound velocity is found to be maximum. The inconsistent behavior of angle dependent velocities is associated to the action of SOECs. The ultrasonic properties are discussed in correlation with elastic, thermal and electrical properties. It has been found that the thermal conductivity is the main contributor to the behavior of ultrasonic attenuation and the cause of attenuation is phonon-phonon interaction. The mechanical properties of Cr2Nb are better than other chromium-based alloys (Cr2Ta, Cr2Zr and Cr2Hf) at room temperature, because it has high ultrasonic velocity and low ultrasonic attenuation.
Elastic scintillation materials based on polyorganosiloxane
Grinev, B.V.; Andryushchenko, L.A.; Shershukov, V.M.; Ulanenko, K.B.; Minakova, R.A.; Sevastjanova, I.V.
1994-12-31
The developed elastic scintillators based on polymethyl-phenylsiloxane rubber are characterized by an elevated light output and a low toxicity. The increase of their light output is achieved by raising the content of phenyl chains, varying the chemical structure of luminescent additions and using isopropylnaphthalene. This high-boiling solvent introduced into the scintillation siloxane compositions is confined within siloxane matrix after the hardening of the rubber.
Novel Super-Elastic Materials for Advanced Bearing Applications
NASA Technical Reports Server (NTRS)
Dellacorte, Christopher
2014-01-01
Tribological surfaces of mechanical components encounter harsh conditions in terrestrial, marine and aerospace environments. Brinell denting, abrasive wear and fatigue often lead to life-limiting bearing and gear failures. Novel superelastic materials based upon Ni-Ti alloys are an emerging solution. Ni-Ti alloys are intermetallic materials that possess characteristics of both metals and ceramics. Ni-Ti alloys have intrinsically good aqueous corrosion resistance (they cannot rust), high hardness, relatively low elastic modulus, are chemically inert and readily lubricated. Ni-Ti alloys also belong to the family of superelastics and, despite high hardness, are able to withstand large strains without suffering permanent plastic deformation. In this paper, the use of hard, resilient Ni-Ti alloys for corrosion-proof, shockproof bearing and gear applications are presented. Through a series of bearing and gear development projects, it is demonstrated that Ni-Tis unique blend of materials properties lead to significantly improved load capacity, reduced weight and intrinsic corrosion resistance not found in any other bearing materials. Ni-Ti thus represents a new materials solution to demanding tribological applications.
The elastic properties of woven polymeric fabric
Warren, W.E. )
1989-01-01
The in-plane linear elastic constants of woven fabric are determined in terms of the specific fabric microstructure. The fabric is assumed to be a spatially periodic interlaced network of orthogonal yarns and the individual yarns are modeled as extensible elastica. These results indicate that a significant coupling of bending and stretching effects occurs during deformation. Results of this theoretical analysis compare favorable with measured in-plane elastic constants for Vincel yarn fabrics. 17 refs., 2 figs., 1 tab.
NASA Astrophysics Data System (ADS)
Matveenko, V. P.; Fedorov, A. Yu.; Shardakov, I. N.
2016-01-01
The results of analytical and numerical investigations on estimating the character of the singularity of stresses in a vicinity of different variants of special points of the 2D elastic solids made of functionally graded materials (FGMs) are presented. The variant of construction by analytical methods in the polar system of coordinates is considered for eigensolutions in the flat wedges made of the FGM, the elastic properties of which are represented as power series in terms of the radial coordinate.
Elastic Properties of Several Silicon Nitride Films
Liu, X.; Metcalf, T. H.; Wang, Q.; Photiadis, D. M.
2007-01-01
We have measured the internal friction (Q{sup -1}) of amorphous silicon nitride (a-SiN{sub x}) films prepared by a variety of methods, including low-pressure chemical-vapor deposition (LPCVD), plasma-enhanced chemical-vapor deposition (PECVD), and hot-wire chemical-vapor deposition (HWCVD) from 0.5 K to room temperature. The measurements are made by depositing the films onto extremely high-Q silicon double paddle oscillator substrates with a resonant frequency of {approx}5500 Hz. We find the elastic properties of these a-SiN{sub x} films resemble those of amorphous silicon (a-Si) films, demonstrating considerable variation which depends on the film growth methods and post deposition annealing. The internal friction for most of the films shows a broad temperature-independent plateau below 30 K, characteristic of amorphous solids. The values of Q{sup -1}, however, vary from film to film in this plateau region by more than one order of magnitude. This has been observed in tetrehedrally covalent-bonded amorphous thin films, like a-Si, a-Ge, and a-C. The PECVD films have the highest Q{sup -1} just like a normal amorphous solid, while LPCVD films have an internal friction more than one order of magnitude lower. All the films show a reduction of Q{sup -1} after annealing at 800 C, even for the LPCVD films which were prepared at 850 C. This can be viewed as a reduction of structural disorder.
Elastic properties of inhomogeneous media with chaotic structure.
Novikov, V V; Wojciechowski, K W; Belov, D V; Privalko, V P
2001-03-01
The elastic properties of an inhomogeneous medium with chaotic structure were derived within the framework of a fractal model using the iterative averaging approach. The predicted values of a critical index for the bulk elastic modulus and of the Poisson ratio in the vicinity of a percolation threshold were in fair agreement with the available experimental data for inhomogeneous composites. PMID:11308722
2-Point microstructure archetypes for improved elastic properties
NASA Astrophysics Data System (ADS)
Adams, Brent L.; Gao, Xiang
2004-01-01
Rectangular models of material microstructure are described by their 1- and 2-point (spatial) correlation statistics of placement of local state. In the procedure described here the local state space is described in discrete form; and the focus is on placement of local state within a finite number of cells comprising rectangular models. It is illustrated that effective elastic properties (generalized Hashin Shtrikman bounds) can be obtained that are linear in components of the correlation statistics. Within this framework the concept of an eigen-microstructure within the microstructure hull is useful. Given the practical innumerability of the microstructure hull, however, we introduce a method for generating a sequence of archetypes of eigen-microstructure, from the 2-point correlation statistics of local state, assuming that the 1-point statistics are stationary. The method is illustrated by obtaining an archetype for an imaginary two-phase material where the objective is to maximize the combination C_{xxxx}^{*} + C_{xyxy}^{*}
Slimani, A.; Boukheddaden, K. Varret, F.; Nishino, M.; CREST, JST, 4-1-8 Honcho Kawaguchi, Saitama 332-0012 ; Miyashita, S.; Department of Physics, Graduate School of Science, The University of Tokyo, Bunkyo-Ku, Tokyo
2013-11-21
The present work is devoted to the spatio-temporal investigations of spin-crossover lattices during their thermal relaxation from high- to low-spin state. The analysis is performed using Monte Carlo simulations on a distortable 2D lattice the sites of which are occupied by high-spin (HS) or low-spin (LS) atoms. The lattice is circular in shape and the HS to LS transformation results in single domain nucleation followed by growth and propagation processes. The evolution of the LS:HS interface is monitored during the relaxation process, through the mapping of spin states, displacement fields, local stresses, and elastic energy. The results show a curved interface, the curvature of which is reversed at the mid-transformation. The local stresses and elastic energy peak at the vicinity of the HS:LS interface, with sizeable dependence upon the position along the front line which evidences the edge effects.
Elastic properties of fly ash-stabilized mixes.
Dimter, Sanja; Rukavina, Tatjana; Minažek, Krunoslav
2015-12-01
Stabilized mixes are used in the construction of bearing layers in asphalt and concrete pavement structures. Two nondestructive methods: resonant frequency method and ultrasonic pulse velocity method, were used for estimation of elastic properties of fly ash-stabilized mixes. Stabilized mixes were designed containing sand from the river Drava and binder composed of different share of cement and fly ash. The aim of the research was to analyze the relationship between the dynamic modulus of elasticity determined by different nondestructive methods. Data showed that average value of elasticity modulus obtained by the ultrasound velocity method is lower than the values of elasticity modulus obtained by resonant frequency method. For further analysis and enhanced discussion of elastic properties of fly ash stabilized mixes, see Dimter et al. [1]. PMID:26702415
Elastic properties of fly ash-stabilized mixes
Dimter, Sanja; Rukavina, Tatjana; Minažek, Krunoslav
2015-01-01
Stabilized mixes are used in the construction of bearing layers in asphalt and concrete pavement structures. Two nondestructive methods: resonant frequency method and ultrasonic pulse velocity method, were used for estimation of elastic properties of fly ash–stabilized mixes. Stabilized mixes were designed containing sand from the river Drava and binder composed of different share of cement and fly ash. The aim of the research was to analyze the relationship between the dynamic modulus of elasticity determined by different nondestructive methods. Data showed that average value of elasticity modulus obtained by the ultrasound velocity method is lower than the values of elasticity modulus obtained by resonant frequency method. For further analysis and enhanced discussion of elastic properties of fly ash stabilized mixes, see Dimter et al. [1]. PMID:26702415
NASA Astrophysics Data System (ADS)
Bukač, M.
2016-05-01
We model the interaction between an incompressible, viscous fluid, thin elastic structure and a poroelastic material. The poroelastic material is modeled using the Biot's equations of dynamic poroelasticity. The fluid, elastic structure and the poroelastic material are fully coupled, giving rise to a nonlinear, moving boundary problem with novel energy estimates. We present a modular, loosely coupled scheme where the original problem is split into the fluid sub-problem, elastic structure sub-problem and poroelasticity sub-problem. An energy estimate associated with the stability of the scheme is derived in the case where one of the coupling parameters, β, is equal to zero. We present numerical tests where we investigate the effects of the material properties of the poroelastic medium on the fluid flow. Our findings indicate that the flow patterns highly depend on the storativity of the poroelastic material and cannot be captured by considering fluid-structure interaction only.
Elastic properties of gamma-Pu by resonant ultrasound spectroscopy
Migliori, Albert; Betts, J; Trugman, A; Mielke, C H; Mitchell, J N; Ramos, M; Stroe, I
2009-01-01
Despite intense experimental and theoretical work on Pu, there is still little understanding of the strange properties of this metal. We used resonant ultrasound spectroscopy method to investigate the elastic properties of pure polycrystalline Pu at high temperatures. Shear and longitudinal elastic moduli of the {gamma}-phase of Pu were determined simultaneously and the bulk modulus was computed from them. A smooth linear and large decrease of all elastic moduli with increasing temperature was observed. We calculated the Poisson ratio and found that it increases from 0.242 at 519K to 0.252 at 571K.
Linearized analysis of Richtmyer-Meshkov flow for elastic materials
NASA Astrophysics Data System (ADS)
Plohr, Jeeyeon N.; Plohr, Bradley J.
2005-08-01
We present a study of Richtmyer Meshkov flow for elastic materials. This flow, in which a material interface is struck by a shock wave, was originally investigated for gases, where growth of perturbations of the interface is observed. Here we consider two elastic materials in frictionless contact. The governing system of equations comprises conservation laws supplemented by constitutive equations. To analyse it, we linearize the equations around a one-dimensional background solution under the assumption that the perturbation is small. The background problem defines a Riemann problem that is solved numerically; its solution contains transmitted and reflected shock waves in the longitudinal modes. The linearized Rankine Hugoniot condition provides the interface conditions at the longitudinal and shear waves; the frictionless material interface conditions are also linearized. The resulting equations, a linear system of partial differential equations, is solved numerically using a finite-difference method supplemented by front tracking. In verifying the numerical code, we reproduce growth of the interface in the gas case. For the elastic case, in contrast, we find that the material interface remains bounded: the non-zero shear stiffness stabilizes the flow. In particular, the linear theory remains valid at late time. Moreover, we identify the principal mechanism for the stability of Richtmyer Meshkov flow for elastic materials: the vorticity deposited on the material interface during shock passage is propagated away by the shear waves, whereas for gas dynamics it stays on the interface.
Oxides and Oxide Superconductors: Elastic and Related Properties
NASA Astrophysics Data System (ADS)
Lei, Ming
Using both measurements and modeling, the elastic and related properties of some oxides and oxide superconductors were studied. The polycrystal elastic constants were measured using a MHz-frequency pulse-echo method between 295 and 4 K and corrected to the void-free state by using a model for a composite material containing spherical particles. The elastic moduli of the high-T_{rm c} superconductor rm Y_1Ba _2Cu_3O_7 (YBCO) were compared with that of oxides, especially the perovskites BaTiO _3 and SrTiO_3, which are crystal-structure building blocks for the YBCO superconductor. The bulk moduli were also calculated using a Born ionic model with two energy terms: electrostatic (Madelung) and ion -core-repulsion. The calculated bulk modulus of YBCO, 98 GPa, agrees well with measurement, 101 GPa. Based on monocrystal measurements combined with analysis-theory, elastic stiffnesses C_{ij} for orthorhombic YBCO were estimated. The bulk modulus obtained from the estimated C_{ij} by the Voigt-Reuss-Hill averaging method agrees with the monocrystal measurement. From the measured polycrystalline elastic constants, the Debye characteristic temperatures, Theta_ D, were calculated. For YBCO, Theta_sp{D}{rm O} = 437 K. The electron-phonon parameters, lambda, were estimated from T _{c} and Theta_sp {D}{rm O} using Kresin's model, which is valid for all values of lambda . For YBCO, lambda = 2.24. By calculating the Madelung energy, two further features were studied: the valence of copper and the electron hole distribution. The results show that the hole prefers the CuO_2 plane at the oxygen sites. All the results are consistent with the assumption that all copper ions have valences near +2. Using a relationship between T _ c and Delta V_ A, the difference in Madelung site potentials for a hole at the apical and planar oxygens, the pressure derivative and stress and stain derivatives of T_ c were calculated. The results show that T _ c increases with decreasing a-axis, increasing b
Determination of Viral Capsid Elastic Properties from Equilibrium Thermal Fluctuations
NASA Astrophysics Data System (ADS)
May, Eric R.; Brooks, Charles L., III
2011-05-01
We apply two-dimensional elasticity theory to viral capsids to develop a framework for calculating elastic properties of viruses from equilibrium thermal fluctuations of the capsid surface in molecular dynamics and elastic network model trajectories. We show that the magnitudes of the long wavelength modes of motion available in a simulation with all atomic degrees of freedom are recapitulated by an elastic network model. For the mode spectra to match, the elastic network model must be scaled appropriately by a factor which can be determined from an icosahedrally constrained all-atom simulation. With this method we calculate the two-dimensional Young’s modulus Y, bending modulus κ, and Föppl-von Kármán number γ, for the T=1 mutant of the Sesbania mosaic virus. The values determined are in the range of previous theoretical estimates.
Elastic properties, strength and damage tolerance of pultruded composites
NASA Astrophysics Data System (ADS)
Saha, Mrinal Chandra
Pultruded composites are candidate materials for civil engineering infrastructural applications due their higher corrosion resistance and lower life cycle cost. Efficient use of materials like structural members requires thorough understanding of the mechanism that affects their response. The present investigation addresses the modeling and characterization of E-glass fiber/polyester resin matrix pultruded composites in the form of sheets of various thicknesses. The elastic constants were measured using static, vibration and ultrasonic methods. Two types of piezoelectric crystals were used in ultrasonic measurements. Finally, the feasibility of using a single specimen, in the form of a circular disk, was shown in measuring all the elastic constants using ultrasonic technique. The effects of stress gradient on tensile strength were investigated. A large number of specimens, parallel and transverse to the pultrusion direction, were tested in tension, 3-point flexure, and 4-point flexure. A 2-parameter Weibull model was applied to predict the tensile strength from the flexure tests. The measured and Weibull-predicted ratios did not show consistent agreement. Microstructural observations suggested that the flaw distribution in the material was not uniform, which appears to be a basic requirement for the Weibull distribution. Compressive properties were measured using a short-block compression test specimen of 44.4-mm long and 25.4-mm wide. Specimens were tested at 0°, 30°, 45°, 60° and 90° orientations. The compression test specimen was modeled using 4-noded isoparametric layered plate and shell elements. The predicted elastic properties for the roving layer and the continuous strand mat layer was used for the finite element study. The damage resistance and damage tolerance were investigated experimentally. Using a quasi-static indentation loading, damage was induced at various incrementally increased force levels to investigate the damage growth process. Damage
Nonlinear elastic behavior of phantom materials for elastography.
Pavan, Theo Z; Madsen, Ernest L; Frank, Gary R; Adilton O Carneiro, Antonio; Hall, Timothy J
2010-05-01
The development of phantom materials for elasticity imaging is reported in this paper. These materials were specifically designed to provide nonlinear stress/strain relationship that can be controlled independently of the small strain shear modulus of the material. The materials are mixtures of agar and gelatin gels. Oil droplet dispersions in these materials provide further control of the small strain shear modulus and the nonlinear parameter of the material. Since these materials are mostly water, they are assumed to be incompressible under typical experimental conditions in elasticity imaging. The Veronda-Westman model for strain energy density provided a good fit to all materials used in this study. Materials with a constant gelatin concentration (3.0% dry weight) but varying agar concentration (0.6-2.8% dry weight) demonstrated the same power law relationship between elastic modulus and agar concentration found for pure agar (1.89 +/- 0.02), consistent with percolation theory, and provided a consistent nonlinearity parameter of 4.5 +/- 0.3. The insights provided by this study will form the basis for stable elastography phantoms with stiffness and nonlinear stress/strain relationships in the background that differ from those in the target. PMID:20400811
Elasticity theory equations and fracture condition for materials of varying moduli
Oleinikov, A.I.
1986-11-01
Many massive rocks and composite materials belong to the class of materials of varying moduli with definite distinct deformation and strength properties under tension and compression. The results of experiments indicate that the difference between the properties of materials of different moduli is not limited to tension and compression cases but can also appear clearly for any change in the form of the state of stress. Elasticity theory equations are constructed here to describe the strain of materials of varying moduli as well as the dependence of the strength properties on the form of the state of strain. Tests were done on coal, limestone, diabase and cement and results are shown. Using the dependencies obtained, Poisson's ratio and the elastic modulus can be calculated for these rocks. The equations and conditions of fracture proposed, are written in a simple invariant form.
Nanoscale elastic properties of montmorillonite upon water adsorption.
Ebrahimi, Davoud; Pellenq, Roland J-M; Whittle, Andrew J
2012-12-11
Smectites are an important group of clay minerals that experience swelling upon water adsorption. This paper uses molecular dynamics with the CLAYFF force field to simulate isothermal isobaric water adsorption of interlayer Wyoming Na-montmorillonite, a member of the smectite group. Nanoscale elastic properties of the clay-interlayer water system are calculated from the potential energy of the model system. The transverse isotropic symmetry of the elastic constant matrix was assessed by calculating Euclidean and Riemannian distance metrics. Simulated elastic constants of the clay mineral are compared with available results from acoustic and nanoindentation measurements. PMID:23181550
A three dimensional calculation of elastic equilibrium for composite materials
NASA Technical Reports Server (NTRS)
Lustman, Liviu R.; Rose, Milton E.
1988-01-01
A compact scheme is applied to three-dimensional elasticity problems for composite materials, involving simple geometries. The mathematical aspects of this approach are discussed, in particular the iteration method. A vector processor code implementing the compact scheme is presented, and several numerical experiments are summarized.
A three dimensional calculation of elastic equilibrium for composite materials
NASA Technical Reports Server (NTRS)
Lustman, Liviu R.; Rose, Milton E.
1986-01-01
A compact scheme is applied to three-dimensional elasticity problems for composite materials, involving simple geometries. The mathematical aspects of this approach are discussed, in particular the iteration method. A vector processor code implementing the compact scheme is presented, and several numerical experiments are summarized.
Validity and reliability of estimated modulus of elasticity of cementitious materials
NASA Astrophysics Data System (ADS)
Kockal, N. U.
2015-12-01
Modulus of elasticity is a vital property in cementitious material (CM) design and analysis. A better understanding of the relationship between density, strength and stiffness is needed to construct proper structures especially with reinforced cementitious materials. For this purpose, modulus of elasticity of CMs with different waste aggregates was analyzed and the reliability of estimated values of various equations proposed by standards and sources in literature, suggested in this investigation and derived by a software chosen was discussed. The results demonstrated that as compared to experimental results, the model developed by software was the most accurate as the percentages of error in prediction were in a good agreement.
Mechanical behavior and elastic properties of prestrained columnar ice
NASA Astrophysics Data System (ADS)
Snyder, Scott Aaron
Experiments on columnar-grained ice at --10 °C reveal changes to its mechanical behavior and elastic properties due to compressive prestrain. Laboratory-grown (152-mm cube) specimens of freshwater and saline ice were prestrained under uniaxial across-column compression (to levels from epsilon p = 0.003 to epsilonp = 0.20, at constant strain rates in the ductile regime) and then reloaded, again under uniaxial across-column compression (at rates from 1x10--6 s--1 to 3 x 10--2s--1). Prestrain caused solid-state recrystallization as well as damage in the form of non-propagating microcracks. These microstructural changes were quantified by analysis of thin sections. Elastic properties in across-column directions, both parallel (x1) and perpendicular ( x2) to the initial loading direction, were obtained from P-wave and S-wave ultrasonic velocities. As a result (and depending on the level) of the prestrain imparted in both materials, Young's modulus E was reduced by as much as 30%; the ductile-to-brittle (D--B) transition strain rate epsilon D/B was increased up to a factor of 3 to 10; and the ductile behavior with respect to loading along a direction within the horizontal ( x1-x2) plane of the parent ice sheet changed from isotropic to anisotropic. As the prestrain rate approached the nominal D--B transition rate of initially undamaged material, the magnitudes of prestrain effects on elastic compliance increased. The shift in the D--B transition, on the other hand, was less sensitive to the prestrain rate. The results are interpreted within the framework of a recent model that predicts the transition strain rate based on the micromechanical boundary between creep and fracture processes. Prestrain primarily affected certain parameters in the model, specifically the power-law creep coefficient B (more so than the creep exponent n), Young's modulus E and, by extension, the fracture toughness KIc. The physical implications of these effects are discussed.
Micromechanics of intraply hybrid composites: Elastic and thermal properties
NASA Technical Reports Server (NTRS)
Chamis, C. C.; Sinclair, J. H.
1979-01-01
Composite micromechanics are used to derive equations for predicting the elastic and thermal properties of unidirectional intraply hybrid composites. The results predicted using these equations are compared with those predicted using approximate equations based on the rule of mixtures, linear laminate theory, finite element analysis and limited experimental data. The comparisons for three different intraply hybrids indicate that all four methods predict approximately the same elastic properties and are in good agreement with measured data. The micromechanics equations and linear laminate theory predict about the same values for thermal expansion coefficients. The micromechanics equations predict through-the-thickness properties which are in good agreement with the finite element results.
Elastic Properties and Internal Friction of Two Magnesium Alloys at Elevated Temperatures
Freels, M.; Liaw, P. K.; Garlea, E.; Morrell, J. S.; Radiovic, M.
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 strain 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
Ultrasonic material property determinations
NASA Technical Reports Server (NTRS)
Serabian, S.
1986-01-01
The use and potential offered by ultrasonic velocity and attenuation measurements to determine and/or monitor material properties is explored. The basis for such unique measurements along with examples of materials from a variety of industries are presented.
Elastic constants at low temperatures - Recent measurements on technological materials at NBS
NASA Technical Reports Server (NTRS)
Ledbetter, H. M.
1978-01-01
Solid-state low-temperature elastic properties have been experimentally studied at the NBS Cryogenic Division for four years. Most studies were between room temperature and liquid-helium temperature; some were only to liquid-nitrogen temperature. Two dynamic (high-frequency) experimental methods were used, pulse-echo and resonance, resulting in adiabatic elastic constants. The present paper reviews these studies for 47 technological materials - metals, alloys, and composites. The elastic constants primarily discussed are Young's modulus, the shear modulus, the bulk modulus (reciprocal compressibility), and Poisson's ratio. A summary table is presented to show which base metals tend to exhibit regular, irregular, or anomalous behavior in their elastic constant/temperature curves.
Elastic properties of metals and minerals under shock compression
Duffy, T.S.
1992-01-01
Comparison of laboratory elasticity data with seismic measurements of the Earth provides a means to understand the deep interior. In this work, elastic wave velocities have been measured under shock compression to 80 GPa in an Fe-Cr-Ni alloy, to 27 GPa in polycrystalline MgO, and to 81 GPa in molybdenum preheated to 1400[degrees]C. These measurements were made by recording particle velocity histories at a sample surface using the method of velocity interferometry. Compressional and bulk wave velocities in Fe-Cr-Ni alloy are consistent with third-order finite strain theory and ultrasonic data. The measured wave profiles can be successfully reproduced by numerical simulations utilizing elastic-plastic theory modified by a Bauschinger effect and stress relaxation. Material strength was found to increase by a factor of at least 5 up to 80 GPa and to be 2-3% of the total stress. Compressional and bulk velocities in Fe-Cr-Ni define linear velocity-density trends and can be modeled by averaging properties of Fe, Cr, and Ni. The effect of alloying [approximately]4 wt.% Ni with Fe would change both V[sub P] and V[sub B] by less than 1% under Earth's core conditions. Compressional and shear velocities in Fe-Ni are compatible with inner core values when corrected for thermal effects. Wave profile and EOS measurements in polycrystalline MgO define its EOS: U[sub S] = 6.77(0.08) + 1.27(0.04)[mu][sub p]. Compressional sound velocities to 27 GPa yield a longitudinal modulus and its pressure derivative which are in good agreement with ultrasonic determinations. The unloading wave profiles can be modeled using a modified elastic-plastic constitutive response originally developed for metals. Thermal expansivities in MgO have been determined to be 12 [+-] 14 [times] 10[sup [minus]6] K[sup [minus]1] at P = 174-200 GPa and T = 3100-3600 K from shock temperature and EOS data. These results imply that the Earth's lower mantle is enriched in Si and/or Fe relative to the upper mantle.
Experimental investigation of Rayleigh Taylor instability in elastic-plastic materials
NASA Astrophysics Data System (ADS)
Haley, Aaron Alan; Banerjee, Arindam
2010-11-01
The interface of an elastic-plastic plate accelerated by a fluid of lower density is Rayleigh Taylor (RT) unstable, the growth being mitigated by the mechanical strength of the plate. The instability is observed when metal plates are accelerated by high explosives, in explosive welding, and in volcanic island formation due to the strength of the inner crust. In contrast to the classical case involving Newtonian fluids, RT instability in accelerated solids is not well understood. The difficulties for constructing a theory for the linear growth phase in solids is essentially due to the character of elastic-plastic constitutive properties which has a nonlinear dependence on the magnitude of the rate of deformation. Experimental investigation of the phenomena is difficult due to the exceedingly small time scales (in high energy density experiments) and large measurement uncertainties of material properties. We performed experiments on our Two-Wheel facility to study the linear stage of the incompressible RT instability in elastic-plastic materials (yogurt) whose properties were well characterized. Rotation of the wheels imparted a constant centrifugal acceleration on the material interface that was cut with a small sinusoidal ripple. The controlled initial conditions and precise acceleration amplitudes are levied to investigate transition from elastic to plastic deformation and allow accurate and detailed measurements of flow properties.
Temperature Dependent Elastic moduli of Lead-Telluride based Thermoelectric Materials
Ren, Fei; Case, Eldon D; Ni, Jennifer E.; Timm, Edward J; Lara-Curzio, Edgar; Kanatzidis, Mercouri G.; Trejo, Rosa M; Lin, Chia-Her
2009-01-01
In the open literature, reports of mechanical properties are limited for semiconducting thermoelectric materials, including the temperature dependence of the elastic moduli. In this study, for both cast ingots and hot pressed billets of Ag-, Sb-, Sn-, and S- doped PbTe thermoelectric materials, Resonant Ultrasound Spectroscopy (RUS) was utilized to determine the temperature dependence of elastic moduli including Young's modulus, shear modulus, and Poisson's ratio. This study is the first to determine the temperature-dependent elastic moduli for these PbTe based thermoelectrics and among the few determinations of elasticity of any thermoelectric material for temperatures above 300 K. The Young s modulus and Poisson s ratio measured from room temperature to 773 K during heating and cooling agreed well. Also, the observed Young s modulus, E, versus temperature, T, relationship E(T) = E0(1 bT) is consistent with predictions for materials in the range well above the Debye temperature. A nanoindentation study of Young s modulus on the specimen faces showed that both the cast and hot pressed specimens were approximately elastically isotropic.
Wang, Qian; Ashley, Dennis W.; Dechow, Paul C.
2010-01-01
Understanding the mechanical features of cortical bone and their changes with growth and adaptation to function plays an important role in our ability to interpret the morphology and evolution of craniofacial skeletons. We assessed the elastic properties of cortical bone of juvenile and adult baboon mandibles using ultrasonic techniques. Results showed that, overall, cortical bone from baboon mandibles could be modeled as an orthotropic elastic solid. There were significant differences in the directions of maximum stiffness, thickness, density, and elastic stiffness among different functional areas, indicating regional adaptations. After maturity, the cortical bone becomes thicker, denser, and stiffer, but less anisotropic. There were differences in elastic properties of the corpus and ramus between male and female mandibles which are not observed in human mandibles. There were correlations between cortical thicknesses and densities, between bone elastic properties and microstructural configuration, and between the directions of maximum stiffness and bone anatomical axes in some areas. The relationships between bone extrinsic and intrinsic properties bring us insights into the integration of form and function in craniofacial skeletons and suggest that we need to consider both macroscopic form, microstructural variation, and the material properties of bone matrix when studying the functional properties and adaptive nature of the craniofacial skeleton in primates. The differences between baboon and human mandibles is at variance to the pattern of differences in crania, suggesting differences in bone adaption to varying skeletal geometries and loading regimes at both phylogenetic and ontogenetic levels. PMID:19927280
Elastic Properties of Lithium Germanate Glasses Studied by Brillouin Scattering
NASA Astrophysics Data System (ADS)
Kaneda, Kazuhiro; Matsuda, Yu; Kojima, Seiji
2010-07-01
To investigate the correlation between structural changes and physical properties, the elastic properties of lithium germanate glasses, xLi2O·(100-x)GeO2 represented as a function of Li2O mole fraction, have been studied in the composition range 6≤x≤36 mol % by Brillouin scattering spectroscopy. Raman spectra have also been measured to clarify the composition variation of structural changes. Several elastic properties, such as sound velocity and elastic modulus, have been determined from the Brillouin shift. The longitudinal and transverse sound velocities increase up to about x=20 mol %, and above x=20 mol %, they become nearly constant. Elastic moduli, such as longitudinal modulus (L) and shear modulus (G), increase gradually up to x=22 mol % and then decrease with a further increase in Li2O content. It is considered that such behaviors are due to the change in the coordination number of germanium atoms and the formation of nonbridging oxygen. Differently from other elastic moduli, Poisson's ratio (σ) shows a similar behavior to sound velocity.
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.
Synthesis, Crystal Structure, and Elastic Properties of Novel Tungsten Nitrides
Wang, Shanmin; Yu, Xiaohui; Lin, Zhijun; Zhang, Ruifeng; He, Duanwei; Qin, Jiaqian; Zhu, Jinlong; Han, Jiantao; Wang, Lin; Mao, Ho-kwang; Zhang, Jianzhong; Zhao, Yusheng
2012-12-13
Among transition metal nitrides, tungsten nitrides possess unique and/or superior chemical, mechanical, and thermal properties. Preparation of these nitrides, however, is challenging because the incorporation of nitrogen into tungsten lattice is thermodynamically unfavorable at atmospheric pressure. To date, most materials in the W-N system are in the form of thin films produced by nonequilibrium processes and are often poorly crystallized, which severely limits their use in diverse technological applications. Here we report synthesis of tungsten nitrides through new approaches involving solid-state ion exchange and nitrogen degassing under pressure. We unveil a number of novel nitrides including hexagonal and rhombohedral W{sub 2}N{sub 3}. The final products are phase-pure and well-crystallized in bulk forms. For hexagonal W{sub 2}N{sub 3}, hexagonal WN, and cubic W3N4, they exhibit elastic properties rivaling or even exceeding cubic-BN. All four nitrides are prepared at a moderate pressure of 5 GPa, the lowest among high-pressure synthesis of transition metal nitrides, making it practically feasible for massive and industrial-scale production.
Elastic properties of Li+ doped lead zinc borate glasses
NASA Astrophysics Data System (ADS)
Rajaramakrishna, R.; Lakshmikantha, R.; Anavekar, R. V.
2014-04-01
Glasses in the system 0.25PbO-(0.25-x) ZnO-0.5B2O3-xLi2O have been prepared by the melt quenching technique. Elastic properties, DSC studies have been employed to study the role of Li2O in the present glass system. Elastic properties and Debye temperature have been determined using pulsed echo ultrasonic interferometer operating at 10MHz. Sound velocities Vl, Vt and elastic moduli decrease up to 5 mol% and then gradually increase with increase in Li2O concentration. Debye temperature and the glass transition temperature decreases with increase in Li2O. Densities remains almost constant up to 15 mol% Li2O concentration and increases monotonically while the molar volume decreases with the increase of Li2O concentration. The results are discussed in view of the borate structural network and dual role of Zn and Pb in these glasses.
High pressure elasticity and thermal properties of depleted uranium
NASA Astrophysics Data System (ADS)
Jacobsen, M. K.; Velisavljevic, N.
2016-04-01
Studies of the phase diagram of uranium have revealed a wealth of high pressure and temperature phases. Under ambient conditions the crystal structure is well defined up to 100 gigapascals (GPa), but very little information on thermal conduction or elasticity is available over this same range. This work has applied ultrasonic interferometry to determine the elasticity, mechanical, and thermal properties of depleted uranium to 4.5 GPa. Results show general strengthening with applied load, including an overall increase in acoustic thermal conductivity. Further implications are discussed within. This work presents the first high pressure studies of the elasticity and thermal properties of depleted uranium metal and the first real-world application of a previously developed containment system for making such measurements.
Dynamic properties of ceramic materials
Grady, D.E.; Wise, J.L.
1993-09-01
Controlled impact methods have been employed to obtain dynamic response properties of armor materials. Experimental data have been obtained for high-strength ceramics. Continued analysis of time-resolved velocity interferometer measurements has produced systematic material-property data for Hugoniot and release response, initial and post-yield strength, pressure-induced phase transformation, and dynamic fracture strength. A new technique has been developed to measure hydrodynamic properties of ceramic through shock-wave experiments on metal-ceramic composites and data obtained for silicon carbide. Additional data on several titanium diboride ceramics and high-quality aluminum oxide ceramic have been acquired, and issues regarding the influence of microstructure on dynamic properties have emerged. Comparison of dynamic (Hugoniot elastic limit) strength and indentation hardness data has been performed and important correlations revealed. Innovative impact experiments on confined and unconfined alumina rods using axial and transverse VISAR diagnostics have been demonstrated which permit acquisition of multiaxial dynamic response data. Dynamic failure properties of a high-density aluminosilicate glass, similar in composition to the intergranular glassy phase of some aluminas, have been investigated with regard to yield, spall, and failure-wave propagation.
Bauer-Gogonea, S.; Camacho-Gonzalez, F.; Schwoediauer, R.; Ploss, B.; Bauer, S.
2007-09-17
Nonlinearities in ferroelectret polymer foam capacitors arise from voltage-dependent thickness changes. Such thickness changes are caused by the converse piezoelectric and electrostrictive effects in these soft materials. The authors show that the higher harmonics of the current response during application of a sinusoidal voltage to ferroelectret capacitors provide information on the elastic and electromechanical properties of the foam. The authors demonstrate the potential of this versatile measurement technique by investigating the temperature dependence of the piezoelectric response and by monitoring the changes in the elastic and electromechanical properties during inflation of cellular polypropylene.
NASA Technical Reports Server (NTRS)
Heyman, J. S.; Allison, S. G.; Salama, K.
1985-01-01
The behavior of higher order elastic properties, which are much more sensitive to material state than are second order properties, has been studied for steel alloys AISI 1016, 1045, 1095, and 8620 by measuring the stress derivative of the acoustic natural velocity to determine the stress acoustic constants (SAC's). Results of these tests show a 20 percent linear variation of SAC's with carbon content as well as even larger variations with prestrain (plastic deformation). The use of higher order elastic characterization permits quantitative evaluation of solids and may prove useful in studies of fatigue and fracture.
First Principles Calculations for X-ray Resonant Spectra and Elastic Properties
Yongbin Lee
2006-05-01
In this thesis, we discuss applications of first principles methods to x-ray resonant spectra and elastic properties calculation. We start with brief reviews about theoretical background of first principles methods, such as density functional theory, local density approximation (LDA), LDA+U, and the linear augmented plane wave (LAPW) method to solve Kohn-Sham equations. After that we discuss x-ray resonant scattering (XRMS), x-ray magnetic circular dichroism (XMCD) and the branching problem in the heavy rare earths Ledges. In the last chapter we discuss the elastic properties of the second hardest material AlMgB{sub 14}.
NASA Astrophysics Data System (ADS)
Karami, Keyhan; Abedi, Majid; Zamani Nejad, Mohammad; Lotfian, Mohammad Hassan
2012-12-01
On the basis of plane elasticity theory (PET), the displacement and stress components in a thick-walled spherical pressure vessels made of heterogeneous materials subjected to internal and external pressure is developed. The mechanical properties except the Poisson's ratio are assumed to obey the parabolic variations throughout the thickness. Effect of material inhomogeneity on the elastic deformations and stresses is investigated. The analytical solutions and the solutions carried out through the FEM have a good agreement. The values used in this study are arbitrary chosen to demonstrate the effect of inhomogeneity on displacements, and stresses distributions.
Atomic, Crystal, Elastic, Thermal, Nuclear, and Other Properties of Beryllium
Goldberg, A
2006-02-01
This report is part of a series of documents that provide a background to those involved in the construction of beryllium components and their applications. This report is divided into five sub-sections: Atomic/Crystal Structure, Elastic Properties, Thermal Properties, Nuclear Properties, and Miscellaneous Properties. In searching through different sources for the various properties to be included in this report, inconsistencies were at times observed between these sources. In such cases, the values reported by the Handbook of Chemistry and Physics was usually used. In equations, except where indicated otherwise, temperature (T) is in degrees Kelvin.
Determining the frequency dependence of elastic properties of fractured rocks
NASA Astrophysics Data System (ADS)
Ahrens, Benedikt; Renner, Jörg
2016-04-01
In the brittle crust, rocks often contain joints or faults on various length scales that have a profound effect on fluid flow and heat transport, as well as on the elastic properties of rocks. Improving the understanding of the effect of fractures and the role of stress state and heterogeneity along the fractures on elastic properties of rocks is potentially important for the characterization of deep geothermal reservoirs. Seismic surveys, typically covering a frequency range of about 1 to 1000 Hz, are a valuable tool to investigate fractured rocks but the extraction of fracture properties remains difficult. The elementary frequency-dependent interaction between fractured rock matrix and viscous pore fluids and the resulting effects on wave propagation require well-founded dispersion analyses of heterogeneous rocks. In this laboratory study, we investigate the stress dependence of the effective elastic properties of fractured reservoir rocks over a broad frequency range. To assess the effect of faults on the effective elastic properties, we performed cyclic axial loading tests on intact and fractured samples of Solnhofen limestone and Padang granodiorite. The samples contained an idealized fault, which was created by stacking two sample discs on top of each other that experienced various surface treatments to vary their roughness. The dynamic loading tests were conducted with frequencies up to 10 Hz and amplitudes reaching 10% of the statically applied stress. Simultaneously, P- and S-wave measurements were performed in the ultrasonic frequency range (above 100 kHz) with a total of 16 sensors, whose positioning above and below the samples guarantees a wide range of transmission and reflection angles. Preliminary results of static and dynamic elastic properties of intact Padang granodiorite show a pronounced increase in Young's moduli and Poisson's ratio with increasing axial stress. Stress relaxation is accompanied by a decrease of the modulus and the Poisson
Building Materials Property Table
2010-04-16
This information sheet describes a table of some of the key technical properties of many of the most common building materials taken from ASHRAE Fundamentals - 2001, Moisture Control in Buildings, CMHC, NRC/IRC, IEA Annex 24, and manufacturer data.
Erba, A; Mahmoud, A; Belmonte, D; Dovesi, R
2014-03-28
A computational strategy is devised for the accurate ab initio simulation of elastic properties of crystalline materials under pressure. The proposed scheme, based on the evaluation of the analytical stress tensor and on the automated computation of pressure-dependent elastic stiffness constants, is implemented in the CRYSTAL solid state quantum-chemical program. Elastic constants and related properties (bulk, shear and Young moduli, directional seismic wave velocities, elastic anisotropy index, Poisson's ratio, etc.) can be computed for crystals of any space group of symmetry. We apply such a technique to the study of high-pressure elastic properties of three silicate garnet end-members (namely, pyrope, grossular, and andradite) which are of great geophysical interest, being among the most important rock-forming minerals. The reliability of this theoretical approach is proved by comparing with available experimental measurements. The description of high-pressure properties provided by several equations of state is also critically discussed. PMID:24697466
Erba, A. Mahmoud, A.; Dovesi, R.; Belmonte, D.
2014-03-28
A computational strategy is devised for the accurate ab initio simulation of elastic properties of crystalline materials under pressure. The proposed scheme, based on the evaluation of the analytical stress tensor and on the automated computation of pressure-dependent elastic stiffness constants, is implemented in the CRYSTAL solid state quantum-chemical program. Elastic constants and related properties (bulk, shear and Young moduli, directional seismic wave velocities, elastic anisotropy index, Poisson's ratio, etc.) can be computed for crystals of any space group of symmetry. We apply such a technique to the study of high-pressure elastic properties of three silicate garnet end-members (namely, pyrope, grossular, and andradite) which are of great geophysical interest, being among the most important rock-forming minerals. The reliability of this theoretical approach is proved by comparing with available experimental measurements. The description of high-pressure properties provided by several equations of state is also critically discussed.
Revisit of the relationship between the elastic properties and sound velocities at high pressures
Wang, Chenju; Yan, Xiaozhen; Xiang, Shikai Chen, Haiyan; Gu, Jianbing; Yu, Yin; Kuang, Xiaoyu
2014-09-14
The second-order elastic constants and stress-strain coefficients are defined, respectively, as the second derivatives of the total energy and the first derivative of the stress with respect to strain. Since the Lagrangian and infinitesimal strain are commonly used in the two definitions above, the second-order elastic constants and stress-strain coefficients are separated into two categories, respectively. In general, any of the four physical quantities is employed to characterize the elastic properties of materials without differentiation. Nevertheless, differences may exist among them at non-zero pressures, especially high pressures. Having explored the confusing issue systemically in the present work, we find that the four quantities are indeed different from each other at high pressures and these differences depend on the initial stress applied on materials. Moreover, the various relations between the four quantities depicting elastic properties of materials and high-pressure sound velocities are also derived from the elastic wave equations. As examples, we calculated the high-pressure sound velocities of cubic tantalum and hexagonal rhenium using these nexus. The excellent agreement of our results with available experimental data suggests the general applicability of the relations.
First-principles elastic properties of (alpha)-Pu
Soderlind, P; Klepeis, J
2009-02-18
Density-functional electronic-structure calculations have been used to investigate the ambient pressure and low temperature elastic properties of the ground-state {alpha} phase of plutonium metal. The electronic structure and correlation effects are modeled within a fully relativistic antiferromagnetic treatment with a generalized gradient approximation for the electron exchange and correlation functional. The 13 independent elastic constants, for the monoclinic {alpha}-Pu system, are calculated for the observed geometry. A comparison of the results with measured data from recent resonant ultrasound spectroscopy for a cast sample is made.
First-principles elastic properties of (alpha)-Pu
Soderlind, P; Klepeis, J E
2008-11-04
Density-functional electronic structure calculations have been used to investigate the ambient pressure and low temperature elastic properties of the ground-state {alpha} phase of plutonium metal. The electronic structure and correlation effects are modeled within a fully relativistic anti-ferromagnetic treatment with a generalized gradient approximation for the electron exchange and correlation functionals. The 13 independent elastic constants, for the monoclinic {alpha}-Pu system, are calculated for the observed geometry. A comparison of the results with measured data from resonant ultrasound spectroscopy for a cast sample is made.
High pressure phase transition and elastic properties of americium telluride
NASA Astrophysics Data System (ADS)
Aynyas, Mahendra; Rukmangad, Aditi; Arya, B. S.; Sanyal, S. P.
2013-06-01
The structural and elastic properties of Americium Telluride (AmTe) have been investigated by using a modified inter-ionic potential theory (MIPT). This theory is capable of explaining first order phase transition with a crystallographic change NaCl to CsCl structure for this compound. The values of optimized lattice constant, phase transition pressure, zero pressure bulk modulus and second order elastic constants (C11, C44) agree well with their corresponding experimental data. Debye temperature (θD) is also calculated for this compound for the first time.
Electronic and elastic properties of MoS 2
NASA Astrophysics Data System (ADS)
Wei, Li; Jun-fang, Chen; Qinyu, He; Teng, Wang
2010-05-01
The electronic structures and elastic properties of molybdenum disulfide are studied using first-principles calculations. The energy band structure and density of state (DOS) of MoS 2 at 0 GPa are calculated. The band gap energy of MoS 2 versus the pressure 0-40 GPa is obtained. We find that the band gap energy decreases as the pressure increases. The geometry optimized structural parameters for lithium nitride under different pressures are listed. The parameters a, c, and E (the enthalpy) all decrease with increasing pressure. However, parameter B (the bulk modulus), S (the shear modulus) and Y (the Young’s modulus) increase with pressure. The normalized lattice constants and the elastic modulus as two functions of pressure from 0-40 GPa are obtained. All the calculated elastic constants Cij increase by different rates with increasing pressure.
Theoretical fracture criterion of the layered elastic composite materials
NASA Astrophysics Data System (ADS)
Ćilli, A.
2016-03-01
The theoretical fracture limit in compression of a composite material with two isotropic homogeneous elastic layers is studied using the piecewise homogeneous body model with the three-dimensional theory of elasticity. We assumed the layers have the initial local imperfections and these imperfections are moved with respect to each other by the same length which is expressed by the angle β. The aim of the investigations was to study the influence of this length on the values of the theoretical fracture criterion limit. The numerical results for the influence of the initial local imperfections on the values of fracture limit are presented. It is therefore concluded that the values of the theoretical fracture limit increase with the length of the shifting.
The structural, elastic and thermodynamic properties of thorium tetraboride
NASA Astrophysics Data System (ADS)
Aydin, Sezgin; Tatar, Aynur
2011-04-01
The structural, elastic and thermodynamic properties of thorium tetraboride (ThB 4) have been investigated by using first-principles plane-wave pseudopotential density functional theory with generalized gradient approximation. The behaviors of structural parameters under 0-70 GPa hydrostatic pressure are studied by means of Broyden, Fletcher, Goldfarb, and Shanno (BFGS) geometry optimization scheme. By using the stress-strain method, single crystal elastic constants are calculated to test the mechanical stability of the crystal structure and to determine mechanical properties such as bulk modulus at each pressure. However, in order to study the thermodynamic properties of ThB 4, the quasi-harmonic Debye model is used. Then, the dependencies of bulk modulus, heat capacities, thermal expansions, Grüneisen parameters and Debye temperatures on the temperature and pressure are obtained in the whole pressure range 0-70 GPa and temperature range 0-1500 K.
Structure dependent elastic properties of supergraphene
NASA Astrophysics Data System (ADS)
Hou, Juan; Yin, Zhengnan; Zhang, Yingyan; Chang, Tien-Chong
2016-04-01
Complete replacement of aromatic carbon bonds in graphene by carbyne chains gives rise to supergraphene whose mechanical properties are expected to depend on its structure. However, this dependence is to date unclear. In this paper, explicit expressions for the in-plane stiffness and Poisson's ratio of supergraphene are obtained using a molecular mechanics model. The theoretical results show that the in-plane stiffness of supergraphene is drastically (at least one order) smaller than that of graphene, whereas its Poisson's ratio is higher than 0.5. As the index number increases (i.e., the length of carbyne chains increases and the bond density decreases), the in-plane stiffness of supergraphene decreases while the Poisson's ratio increases. By analyzing the relation among the layer modulus, in-plane stiffness and Poisson's ratio, it is revealed that the mechanism of the faster decrease in the in-plane stiffness than the bond density is due to the increase of Poisson's ratio. These findings are useful for future applications of supergraphene in nanomechanical systems.
Water jet indentation for local elasticity measurements of soft materials.
Chevalier, N R; Dantan, Ph; Gazquez, E; Cornelissen, A J M; Fleury, V
2016-01-01
We present a novel elastography method for soft materials (100Pa-100kPa) based on indentation by a μm-sized water jet. We show that the jet creates a localized deformation ("cavity") of the material that can be easily visualized. We study experimentally how cavity width and depth depend on jet speed, height, incidence angle and sample elasticity. We describe how to calibrate the indenter using gels of known stiffness. We then demonstrate that the indenter yields quantitative elasticity values within 10% of those measured by shear rheometry. We corroborate our experimental findings with fluid-solid finite-element simulations that quantitatively predict the cavity profile and fluid flow lines. The water jet indenter permits in situ local stiffness measurements of 2D or 3D gels used for cell culture in physiological buffer, is able to assess stiffness heterogeneities with a lateral resolution in the range 50-500μm (at the tissue scale) and can be assembled at low cost with standard material from a biology laboratory. We therefore believe it will become a valuable method to measure the stiffness of a wide range of soft, synthetic or biological materials. PMID:26830759
Elastic properties of sulphur and selenium doped ternary PbTe alloys by first principles
Bali, Ashoka Chetty, Raju Mallik, Ramesh Chandra
2014-04-24
Lead telluride (PbTe) is an established thermoelectric material which can be alloyed with sulphur and selenium to further enhance the thermoelectric properties. Here, a first principles study of ternary alloys PbS{sub x}Te{sub (1−x)} and PbSe{sub x}Te{sub (1−x)} (0≤x≤1) based on the Virtual Crystal Approximation (VCA) is presented for different ratios of the isoelectronic atoms in each series. Equilibrium lattice parameters and elastic constants have been calculated and compared with the reported data. Anisotropy parameter calculated from the stiffness constants showed a slight improvement in anisotropy of elastic properties of the alloys over undoped PbTe. Furthermore, the alloys satisfied the predicted stability criteria from the elastic constants, showing stable structures, which agreed with the previously reported experimental results.
Homogenization of periodic elastic composites and locally resonant sonic materials
NASA Astrophysics Data System (ADS)
Nemat-Nasser, Sia; Willis, John R.; Srivastava, Ankit; Amirkhizi, Alireza V.
2011-03-01
A method for homogenization of an elastic composite with periodic microstructure is presented, focusing on the Floquet-type elastic waves. The resulting homogenized frequency-dependent elasticity and mass density then automatically satisfy the overall conservation laws and by necessity produce the exact dispersion relations. It is also shown that the dispersion relations and the associated field quantities can be accurately calculated using a mixed variational approach, based on the microstructure of the associated unit cell. The method is used to calculate the dynamic effective parameters for a layered composite by using both the exact solution and the results of the mixed variational formulation. The exact and approximate results are shown to be in close agreement, which makes it possible to use the approximate method for the proposed type of homogenization in cases where an exact solution does not exist. The homogenized frequency-dependent effective parameters give rise to the concept of dynamic Ashby charts that can be used to illustrate the effect of the microstructural architecture on the dynamic properties of a composite. In particular, the charts vividly display how this effective stiffness and density vary with frequency and may attain negative values within certain frequency ranges which can be changed as desired using the microarchitecture while keeping the volume fraction of the unit cell’s constituents constant.
Plate and butt-weld stresses beyond elastic limit, material and structural modeling
NASA Technical Reports Server (NTRS)
Verderaime, V.
1991-01-01
Ultimate safety factors of high performance structures depend on stress behavior beyond the elastic limit, a region not too well understood. An analytical modeling approach was developed to gain fundamental insights into inelastic responses of simple structural elements. Nonlinear material properties were expressed in engineering stresses and strains variables and combined with strength of material stress and strain equations similar to numerical piece-wise linear method. Integrations are continuous which allows for more detailed solutions. Included with interesting results are the classical combined axial tension and bending load model and the strain gauge conversion to stress beyond the elastic limit. Material discontinuity stress factors in butt-welds were derived. This is a working-type document with analytical methods and results applicable to all industries of high reliability structures.
Toward mineralogical interpretation of LLVSP: High-P,T elasticity of deep mantle materials
NASA Astrophysics Data System (ADS)
Tsuchiya, J.; Tsuchiya, T.
2010-12-01
Seismological studies have clarified that although most part of the lower mantle is fairly homogeneous, substantial heterogeneities exist at the bottom a few hundred km. They, in particular low-velocity anomalies observed beneath central-Pacific and Africa often called large low shear velocity provinces (LLSVP), attract great interest, since clarification of their nature is a key to understanding of chemical and dynamical properties of the Earth's mantle. Although they would be produced associated with temperature and/or compositional heterogeneities, details are still largely unknown. Elastic property of possible mantle constituents is one of the most important properties to clarify this issue. So many studies on the high-P,T elasticity of minerals have been performed to date. However, those are still limited for some major phases in the lowermost mantle condition, such as Mg-perovskite, post-perovskite, periclase, and Ca-perovskite. We therefore performed new ab initio simulations on the high-P,T elasticity of some other phases, which are expected not to be abundant in the average silicate mantle but to be substantial when considering differentiated materials. We will discuss possible compositional heterogeneity by constructing mineralogical models of the deep mantle based on the obtained elasticity. Research supported by JSPS Grant-in-Aid for Scientific Research Grants 20001005 and 21740379 and the Ehime Univ G-COE program "Deep Earth Mineralogy".
Size-dependent elastic properties of crystalline polymers via a molecular mechanics model
NASA Astrophysics Data System (ADS)
Zhao, Junhua; Guo, Wanlin; Zhang, Zhiliang; Rabczuk, Timon
2011-12-01
An analytical molecular mechanics model is developed to obtain the size-dependent elastic properties of crystalline polyethylene. An effective "stick-spiral" model is adopted in the polymer chain. Explicit equations are derived from the Lennard-Jones potential function for the van der Waals force between any two polymer chains. By using the derived formulas, the nine size-dependent elastic constants are investigated systematically. The present analytical results are in reasonable agreement with those from present united-atom molecular dynamics simulations. The established analytical model provides an efficient route for mechanical characterization of crystalline polymers and related materials toward nanoelectromechanical applications.
Elastic properties and electronic structures of lanthanide hexaborides
NASA Astrophysics Data System (ADS)
Duan, Jie; Zhou, Tong; Zhang, Li; Du, Ji-Guang; Jiang, Gang; Wang, Hong-Bin
2015-09-01
The structural, elastic, and electronic properties of a series of lanthanide hexaborides (LnB6) have been investigated by performing ab initio calculations based on the density functional theory using the Vienna ab initio simulation package. The calculated lattice and elastic constants of LnB6 are in good agreement with the available experimental data and other theoretical results. The polycrystalline Young’s modulus, shear modulus, the ratio of bulk to shear modulus B/G, Poisson’s ratios, Zener anisotropy factors, as well as the Debye temperature are calculated, and all of the properties display some regularity with increasing atomic number of lanthanide atoms, whereas anomalies are observed for EuB6 and YbB6. In addition, detailed electronic structure calculations are carried out to shed light on the peculiar elastic properties of LnB6. The total density of states demonstrates the existence of a pseudogap and indicates lower structure stability of EuB6 and YbB6 compared with others.
Analytical and Computational Study of One-Dimensional Impact of Graded Elastic Materials
NASA Astrophysics Data System (ADS)
Scheidler, Mike; Gazonas, George
2001-06-01
Traditional armor designs consist of discrete layers of homogeneous materials with different properties. Some recent efforts to improve the ballistic performance of lightweight armors involve replacing several or all of these layers by a monolithic material with continuous property variations. The stress waves generated by ballistic impact in these functionally graded materials tend to be much more complex than in the corresponding layered materials. This fact has led us to examine whether existing hydrocodes can capture the complex wave structures in graded materials and, in particular, whether these codes can accurately predict the peak stresses that may lead to material failure. In this paper we report on the initial phase of this program. We consider the one-dimensional impact of a homogeneous projectile on a graded target, with or without a homogeneous backing plate. All materials are assumed to be linear elastic. Smooth gradings in the density and the elastic modulus are chosen for which exact analytical solutions (including multiple reflections) can be derived using Laplace transforms. These exact solutions are compared with DYNA3D simulations of the same problems. The effects artificial viscosity, nodal spacing (i.e., mesh grading), and number of elements on the DYNA3D solutions are examined.
Ab initio investigations of the elastic properties of chlorates and perchlorates
NASA Astrophysics Data System (ADS)
Korabel'nikov, D. V.; Zhuravlev, Yu. N.
2016-06-01
Elastic properties of NaClO3, KClO3, LiClO4, NaClO4, and KClO4 have been investigated from first principles by the method of linear combination of atomic orbitals in the gradient approximation of the density functional theory using CRYSTAL software. The elastic constants and moduli, hardness, Poisson's ratio, and the anisotropy parameters have been calculated. The velocities of sound, the Debye temperature, the thermal conductivity, and the Grüneisen parameter have been estimated. It has been found that these compounds are mechanically stable, anisotropic, and ductile materials. The dependences of their elastic parameters on the atomic number of the cation have been calculated. The obtained results are in good agreement with the available experimental data.
Elastic properties of Pu metal and Pu-Ga alloys
Soderlind, P; Landa, A; Klepeis, J E; Suzuki, Y; Migliori, A
2010-01-05
We present elastic properties, theoretical and experimental, of Pu metal and Pu-Ga ({delta}) alloys together with ab initio equilibrium equation-of-state for these systems. For the theoretical treatment we employ density-functional theory in conjunction with spin-orbit coupling and orbital polarization for the metal and coherent-potential approximation for the alloys. Pu and Pu-Ga alloys are also investigated experimentally using resonant ultrasound spectroscopy. We show that orbital correlations become more important proceeding from {alpha} {yields} {beta} {yields} {gamma} plutonium, thus suggesting increasing f-electron correlation (localization). For the {delta}-Pu-Ga alloys we find a softening with larger Ga content, i.e., atomic volume, bulk modulus, and elastic constants, suggest a weakened chemical bonding with addition of Ga. Our measurements confirm qualitatively the theory but uncertainties remain when comparing the model with experiments.
Elastic properties of epithelial cells probed by atomic force microscopy.
Brückner, Bastian R; Janshoff, Andreas
2015-11-01
Cellular mechanics plays a crucial role in many biological processes such as cell migration, cell growth, embryogenesis, and oncogenesis. Epithelia respond to environmental cues comprising biochemical and physical stimuli through defined changes in cell elasticity. For instance, cells can differentiate between certain properties such as viscoelasticity or topography of substrates by adapting their own elasticity and shape. A living cell is a complex viscoelastic body that not only exhibits a shell architecture composed of a membrane attached to a cytoskeleton cortex but also generates contractile forces through its actomyosin network. Here we review cellular mechanics of single cells in the context of epithelial cell layers responding to chemical and physical stimuli. This article is part of a Special Issue entitled: Mechanobiology. PMID:26193077
Dynamic relaxation of the elastic properties of hard carbon films
Hirvonen, J.; Koskinen, J.; Kaukonen, M.; Nieminen, R.; Scheibe, H.
1997-06-01
The effect of enhanced atomic mobility on the growth of hard carbon films was examined. Tetrahedrally bonded amorphous carbon films were deposited by condensing energetic carbon ions using an arc-discharge deposition method. The deposition temperature varied between 50 and 400{degree}C. The dependence of elastic properties on deposition temperature was examined by determining the frequency-dependent propagation velocity of ultrasonic surface acoustic waves induced by a laser. A remarkable decrease in elastic coefficient was revealed above the deposition temperature of 300{degree}C and complete relaxation was obtained at 400{degree}C. This observation was analyzed by using a simple model which was in turn supported by molecular dynamics simulations. The relaxation turns out to be a thermally activated, dynamic process with an activation energy of 0.57 eV. Possible relaxation mechanisms associated with the migration of atoms or defects on a growing surface are discussed. {copyright} {ital 1997 American Institute of Physics.}
Dynamic elastic properties of magneto-rheological slurries
NASA Astrophysics Data System (ADS)
Donado, F. F.; Mendoza, M. E. M. E.; Carrillo, J. L.
2001-06-01
We study the propagation of elastic perturbations in magneto-rheological slurries of iron particles dispersed in glycerine. The complexity of these systems is revealed in the fibrillar structure acquired under the application of a magnetic field. Recently, it has been reported the observation of two different low frequency modes of propagation. One of these modes has been associated to the propagation of the perturbation through the fluid medium. The other one has been qualitatively explained as the propagation of the elastic perturbation through the suspended particles. This second mode appears when a magnetic field is applied to the slurry. The propagation speed for both modes depends on the field intensity and on the properties of the magnetic particles. Theoretically, we analyze these modes and calculate the sound velocity. We obtain a quantitative good agreement with the experimental results.
Hardness, elastic, and electronic properties of chromium monoboride
Han, Lei; Wang, Shanmin; Zhu, Jinlong; Han, Songbai; Li, Wenmin; Chen, Bijuan; Wang, Xiancheng; Yu, Xiaohui E-mail: liubc@jlu.edu.cn Long, Youwen; Cheng, Jinguang; Jin, Changqing; Liu, Baochang E-mail: liubc@jlu.edu.cn; Zhang, Ruifeng E-mail: liubc@jlu.edu.cn; Zhang, Jianzhong; Zhao, Yusheng
2015-06-01
We report high-pressure synthesis of chromium monoboride (CrB) at 6 GPa and 1400 K. The elastic and plastic behaviors have been investigated by hydrostatic compression experiment and micro-indentation measurement. CrB is elastically incompressible with a high bulk modulus of 269.0 (5.9) GPa and exhibits a high Vickers hardness of 19.6 (0.7) GPa under the load of 1 kg force. Based on first principles calculations, the observed mechanical properties are attributed to the polar covalent Cr-B bonds interconnected with strong zigzag B-B covalent bonding network. The presence of metallic Cr bilayers is presumably responsible for the weakest paths in shear deformation.
NASA Astrophysics Data System (ADS)
Mueller, H. J.
2012-12-01
The interpretation of highly resolved seismic data from Earths deep interior require measurements of the physical properties of Earth's materials under experimental simulated mantle conditions. More than decade ago seismic tomography clearly showed subduction of crustal material can reach the core mantle boundary under specific circumstances. That means there is no longer space for the assumption deep mantle rocks might be much less complex than deep crustal rocks known from exhumation processes. Considering this geophysical high pressure research is faced the challenge to increase pressure and sample volume at the same time to be able to perform in situ experiments with representative complex samples. High performance multi anvil devices using novel materials are the most promising technique for this exciting task. Recent large volume presses provide sample volumes 3 to 7 orders of magnitude bigger than in diamond anvil cells far beyond transition zone conditions. The sample size of several cubic millimeters allows elastic wave frequencies in the low to medium MHz range. Together with the small and even adjustable temperature gradients over the whole sample this technique makes anisotropy and grain boundary effects in complex systems accessible for elastic and inelastic properties measurements in principle. The measurements of both elastic wave velocities have also no limits for opaque and encapsulated samples. The application of triple-mode transducers and the data transfer function technique for the ultrasonic interferometry reduces the time for saving the data during the experiment to about a minute or less. That makes real transient measurements under non-equilibrium conditions possible. A further benefit is, both elastic wave velocities are measured exactly simultaneously. Ultrasonic interferometry necessarily requires in situ sample deformation measurement by X-radiography. Time-resolved X-radiography makes in situ falling sphere viscosimetry and even the
Elastic properties of thin poly(vinyl alcohol)-cellulose nanocrystal membranes
NASA Astrophysics Data System (ADS)
Pakzad, A.; Simonsen, J.; Yassar, R. S.
2012-03-01
In spite of extensive studies on the preparation and characterization of nanocomposite materials, the correlation of their properties at the nanoscale with those in bulk is a relatively unexplored area. This is of great importance, especially for materials with potential biomedical applications, where surface properties are as important in determining their applicability as bulk characteristics. In this study, the nanomechanical characteristics of thin poly(vinyl alcohol) (PVOH)-poly(acrylic acid) (PAA)-cellulose nanocrystal (CNC) membranes were studied using the nanoindentation module in an atomic force microscope (AFM) and the properties were compared with the macro-scale properties obtained by tensile tests. In general, the elastic properties measured by nanoindentation followed the same trend as macro-scale tensile tests except for the PVOH 85-PAA 0-CNC 15 sample. In comparison to the macro-scale elastic properties, the measured elastic moduli with AFM were higher. Macro-scale tensile test results indicated that, in the presence of PAA, incorporation of CNCs up to 20 wt% improved the elastic modulus of PVOH, but when no PAA was added, increasing the CNC content above 10 wt% resulted in their agglomeration and degradation in mechanical properties of PVOH. The discrepancy between macro-scale tensile tests and nanoindentation in the PVOH 85-PAA 0-CNC 15 sample was correlated to the high degree of inhomogeneity of CNC dispersion in the matrix. It was found that the composites reinforced with cellulose nanocrystals had smaller indentation imprints and the pile-up effect increased with the increase of cellulose nanocrystal content.
Elastic properties of thin poly(vinyl alcohol)-cellulose nanocrystal membranes.
Pakzad, A; Simonsen, J; Yassar, R S
2012-02-01
In spite of extensive studies on the preparation and characterization of nanocomposite materials, the correlation of their properties at the nanoscale with those in bulk is a relatively unexplored area. This is of great importance, especially for materials with potential biomedical applications, where surface properties are as important in determining their applicability as bulk characteristics. In this study, the nanomechanical characteristics of thin poly(vinyl alcohol) (PVOH)-poly(acrylic acid) (PAA)-cellulose nanocrystal (CNC) membranes were studied using the nanoindentation module in an atomic force microscope (AFM) and the properties were compared with the macro-scale properties obtained by tensile tests. In general, the elastic properties measured by nanoindentation followed the same trend as macro-scale tensile tests except for the PVOH 85-PAA 0-CNC 15 sample. In comparison to the macro-scale elastic properties, the measured elastic moduli with AFM were higher. Macro-scale tensile test results indicated that, in the presence of PAA, incorporation of CNCs up to 20 wt% improved the elastic modulus of PVOH, but when no PAA was added, increasing the CNC content above 10 wt% resulted in their agglomeration and degradation in mechanical properties of PVOH. The discrepancy between macro-scale tensile tests and nanoindentation in the PVOH 85-PAA 0-CNC 15 sample was correlated to the high degree of inhomogeneity of CNC dispersion in the matrix. It was found that the composites reinforced with cellulose nanocrystals had smaller indentation imprints and the pile-up effect increased with the increase of cellulose nanocrystal content. PMID:22293708
The Thermal Expansion, Elastic and Fracture Properties of Porous Cordierite at Elevated Temperatures
Shyam, Amit; Lara-Curzio, Edgar; Pandey, Amit; Watkins, Thomas R; More, Karren
2012-01-01
The properties that determine the thermal shock resistance in materials are reported for porous cordierite, a leading candidate material for the fabrication of diesel particulate filters. Fracture toughness and slow crack growth tests were performed on test specimens obtained from the walls of diesel particulate filter monolithic substrates using the double-torsion test method at temperatures between 20 C and 900 C. The thermal expansion and elastic properties were characterized between 20 C and 1000 C. The role of the microstructure of porous cordierite in determining its unusual thermal expansion and elevated temperature Young's modulus and fracture toughness are discussed.
RNA intrusions change DNA elastic properties and structure
NASA Astrophysics Data System (ADS)
Chiu, Hsiang-Chih; Koh, Kyung Duk; Evich, Marina; Lesiak, Annie L.; Germann, Markus W.; Bongiorno, Angelo; Riedo, Elisa; Storici, Francesca
2014-08-01
The units of RNA, termed ribonucleoside monophosphates (rNMPs), have been recently found as the most abundant defects present in DNA. Despite the relevance, it is largely unknown if and how rNMPs embedded in DNA can change the DNA structure and mechanical properties. Here, we report that rNMPs incorporated in DNA can change the elastic properties of DNA. Atomic force microscopy (AFM)-based single molecule elasticity measurements show that rNMP intrusions in short DNA duplexes can decrease - by 32% - or slightly increase the stretch modulus of DNA molecules for two sequences reported in this study. Molecular dynamics simulations and nuclear magnetic resonance spectroscopy identify a series of significant local structural alterations of DNA containing embedded rNMPs, especially at the rNMPs and nucleotide 3' to the rNMP sites. The demonstrated ability of rNMPs to locally alter DNA mechanical properties and structure may help in understanding how such intrusions impact DNA biological functions and find applications in structural DNA and RNA nanotechnology.The units of RNA, termed ribonucleoside monophosphates (rNMPs), have been recently found as the most abundant defects present in DNA. Despite the relevance, it is largely unknown if and how rNMPs embedded in DNA can change the DNA structure and mechanical properties. Here, we report that rNMPs incorporated in DNA can change the elastic properties of DNA. Atomic force microscopy (AFM)-based single molecule elasticity measurements show that rNMP intrusions in short DNA duplexes can decrease - by 32% - or slightly increase the stretch modulus of DNA molecules for two sequences reported in this study. Molecular dynamics simulations and nuclear magnetic resonance spectroscopy identify a series of significant local structural alterations of DNA containing embedded rNMPs, especially at the rNMPs and nucleotide 3' to the rNMP sites. The demonstrated ability of rNMPs to locally alter DNA mechanical properties and structure
Periyannan, Suresh; Balasubramaniam, Krishnan
2015-11-01
A novel technique for simultaneously measuring the moduli of elastic isotropic material, as a function of temperature, using two ultrasonic guided wave modes that are co-generated using a single probe is presented here. This technique can be used for simultaneously measuring Young's modulus (E) and shear modulus (G) of different materials over a wide range of temperatures (35 °C-1200 °C). The specimens used in the experiments have special embodiments (for instance, a bend) at one end of the waveguide and an ultrasonic guided wave generator/detector (transducer) at the other end for obtaining reflected signals in a pulse-echo mode. The orientation of the transducer can be used for simultaneously generating/receiving the L(0,1) and/or T(0,1) using a single transducer in a waveguide on one end. The far end of the waveguides with the embodiment is kept inside a heating device such as a temperature-controlled furnace. The time of flight difference, as a function of uniform temperature distribution region (horizontal portion) of bend waveguides was measured and used to determine the material properties. Several materials were tested and the comparison between values reported in the literature and measured values were found to be in agreement, for both elastic moduli (E and G) measurements, as a function of temperature. This technique provides significant reduction in time and effort over conventional means of measurement of temperature dependence of elastic moduli. PMID:26628161
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.
The elastic properties of beta-eucryptite in the glassy and microcracked crystalline states
Shyam, Amit; Lara-Curzio, Edgar; Muth, Joseph T.
2012-01-01
Amorphous and crystalline {beta}-eucryptite (LiAlSiO{sub 4}) specimens were prepared with controlled grain sizes and varying levels of microcracking, and their elastic moduli were determined using resonant ultrasound spectroscopy. It was found that the relationship between Young's modulus, Poisson's ratio and degree of microcracking in these materials can be described well with fracture-mechanics-based models. It was also found that if glassy {beta}-eucryptite is considered to be a microcracked medium in which broken Si-O bonds, with respect to the crystalline material, constitute microcracks, then its elastic properties can be described equally well by these models. Such considerations are explained by noting the differences in atomic bond density among the different states of the material and by accounting for differences in strain energy release rate measurements on glass and ceramic specimens.
NASA Technical Reports Server (NTRS)
Lineback, L. D.
1974-01-01
The model was developed upon the physical properties of surface energy and intrinsic modulus of elasticity of a material containing a number of equal sized microcracks which are independent of one another. The effect of these cracks upon the strain energy per unit volume of material necessary to continue simultaneous crack growth as well as the measured physical properties was established, and the thermal stress resistance is developed in terms of this energy. The model is expressed in its final form in terms of the measured physical properties of fracture strength, effective modulus of elasticity, and coefficient of thermal expansion. The model was applied to existent thermal stress data of ceramic materials for which these physical properties had been measured. On the basis of these data it was concluded that the thermal stress resistance of a material may be improved by increasing the fracture strength.
Monitoring the Elastic Properties of Ice with Resonant Ultrasound Spectroscopy
NASA Astrophysics Data System (ADS)
van Wijk, K.; Vaughan, M. J.; Prior, D. J.
2015-12-01
The elastic properties of ice are of interest in understanding (theevolution of) sea ice, glaciers and ice sheets, in general. Such dataare crucial if we are to use elastic (ultrasonic to seismic) data toconstrain the internal structure and fabric of ice bodies and theirenvironmental conditions. Fabric (crystallographic preferredorientation) and temperature are two key factors that control therheology of ice sheets. Fabric and temperature data at depth arelimited to the very small number of ice drill holes in Antarctica andGreenland, mostly at ice divides. Thus, there is a need to develop ourunderstanding of elastic properties and wave propagation in ice toextract better ice information from seismic data sets. Resonant Ultrasound Spectroscopy (RUS) is used to measure the resonantmodes of samples, from which we can invert for the full elastictensor, and estimate the attenuation quality factor. Compared to moretraditional time-of-flight ultrasound measurements, there a fewobvious advantages. First, RUS is typically done at an order ofmagnitude lower in frequency, which brings it closer to seismicfrequencies. This is important when attempting to map out thedispersive nature of these elastic properties. Second, it is often farfrom trivial to pick the shear wave arrivals in ultrasound inheterogeneous media. RUS does not rely on this distinctionbetween primary and shear wave. After having developed and applied RUS successfully to rocksamples, an extension of RUS to ice cores in the Physical AcousticsLaboraty shows great promise. For example, we successfully invertedfor the isotropic parameters (bulk and shear modulus) of crystallineman-made ice, and estimated the attenuation quality factor Q. Bycontrolling the freezer settings in the set-up, we were able tomonitor changes in these properties as a function of temperature. Theresultant data are consistent with published results from otherapproaches in the laboratory and the field. RUS is sufficiently fast and portable that
NASA Technical Reports Server (NTRS)
Biaglow, James A.
1995-01-01
Tensile data were obtained from four different types of rhenium at ambient and elevated temperatures. The four types of rhenium included chemical vapor deposition (CVD) and three powder metallurgy (PM) types, i.e., rolled sheet and pressed and sintered bars, with and without hot isostatic pressure (HIP) treatment. Results revealed a wide range of values with ultimate strengths at ambient temperatures varying from 663 MPa for CVD rhenium to 943 MPa for rolled sheet. A similar spread was also obtained for material tested at 1088 K and 1644 K. The wide variance observed with the different materials indicated that the rhenium manufacturing process, material composition and prior handling strongly dictated its properties. In addition to tensile properties, CVD, pressed and sintered material and HIP rhenium successfully completed 100 cycles of low cycle fatigue. Creep data were also obtained showing that CVD and pressed and sintered rhenium could sustain five hours of testing under a tension of 27.5 MPa at 1922 K.
Biaglow, J.A.
1995-09-01
Tensile data were obtained from four different types of rhenium at ambient and elevated temperatures. The four types of rhenium included chemical vapor deposition (CVD) and three powder metallurgy (PM) types, i.e., rolled sheet and pressed and sintered bars, with and without hot isostatic pressure (HIP) treatment. Results revealed a wide range of values with ultimate strengths at ambient temperatures varying from 663 MPa for CVD rhenium to 943 MPa for rolled sheet. A similar spread was also obtained for material tested at 1088 K and 1644 K. The wide variance observed with the different materials indicated that the rhenium manufacturing process, material composition and prior handling strongly dictated its properties. In addition to tensile properties, CVD, pressed and sintered material and HIP rhenium successfully completed 100 cycles of low cycle fatigue. Creep data were also obtained showing that CVD and pressed and sintered rhenium could sustain five hours of testing under a tension of 27.5 MPa at 1922 K.
Materials property measurements
Boyd, D.M.; Green, E.R.; Doctor, S.R.; Good, M.S.
1990-04-19
An in-depth review of the measurement techniques that could be used in materials characterization is presented. The measurement techniques to non-destructively determine the in-service or time-related aging of materials considered include ultrasonic velocity and attenuation, eddy current conductivity, neutron scattering and absorption, conventional and tomographic imaging for ultrasonic and radiation imaging, x-ray scattering, thermal impedance, and magnetic hysteresis. The three sections of the report include a review of failure mechanisms in steel and a discussion of nondestructive evaluation techniques and fracture mechanics, a description of a chart on Measurement Techniques versus Material Properties, and recommendations on the techniques and tests to be performed for the experimental investigations and analysis task of the project. 49 refs., 7 figs.
Characterization of nuclear graphite elastic properties using laser ultrasonic methods
Zeng, Fan W; Han, Karen; Olasov, Lauren R; Gallego, Nidia C; Contescu, Cristian I; Spicer, James B
2015-01-01
Laser ultrasonic methods have been used to characterize the elastic behaviors of commercially-available and legacy nuclear graphites. Since ultrasonic techniques are sensitive to various aspects of graphite microstructure including preferred grain orientation, microcrack orientation and porosity, laser ultrasonics is a candidate technique for monitoring graphite degradation and structural integrity in environments expected in high-temperature, gas-cooled nuclear reactors. Aspects of materials texture can be assessed by studying ultrasonic wavespeeds as a function of propagation direction and polarization. Shear wave birefringence measurements, in particular, can be used to evaluate elastic anisotropy. In this work, laser ultrasonic measurements of graphite moduli have been made to provide insight into the relationship between the microstructures and the macroscopic stiffnesses of these materials. In particular, laser ultrasonic measurements have been made using laser line sources to produce shear waves with specific polarizations. By varying the line orientation relative to the sample, shear wave birefringence measurements have been recorded. Results from shear wave birefringence measurements show that an isostatically molded graphite, such as PCIB, behaves isotropically, while an extruded graphite, such as H-451, displays significant ultrasonic texture. Graphites have complicated microstructures that depend on the manufacturing processes used, and ultrasonic texture in these materials could originate from grain orientation and preferred microcrack alignment. Effects on material isotropy due to service related microstructural changes are possible and the ultimate aim of this work is to determine the degree to which these changes can be assessed nondestructively using laser ultrasonics measurements
Spontaneous Oscillations of Elastic Contractile Materials with Turnover
NASA Astrophysics Data System (ADS)
Dierkes, Kai; Sumi, Angughali; Solon, Jérôme; Salbreux, Guillaume
2014-10-01
Single and collective cellular oscillations driven by the actomyosin cytoskeleton have been observed in numerous biological systems. Here, we propose that these oscillations can be accounted for by a generic oscillator model of a material turning over and contracting against an elastic element. As an example, we show that during dorsal closure of the Drosophila embryo, experimentally observed changes in actomyosin concentration and oscillatory cell shape changes can, indeed, be captured by the dynamic equations studied here. We also investigate the collective dynamics of an ensemble of such contractile elements and show that the relative contribution of viscous and friction losses yields different regimes of collective oscillations. Taking into account the diffusion of force-producing molecules between contractile elements, our theoretical framework predicts the appearance of traveling waves, resembling the propagation of actomyosin waves observed during morphogenesis.
Polymorphism and Elastic Response of Molecular Materials from First Principles: How Hard Can it Be?
NASA Astrophysics Data System (ADS)
Reilly, Anthony; Tkatchenko, Alexandre
2014-03-01
Molecular materials are of great fundamental and applied importance in science and industry, with numerous applications in pharmaceuticals, electronics, sensing, and catalysis. A key challenge for theory has been the prediction of their stability, polymorphism and response to perturbations. While pairwise models of van der Waals (vdW) interactions have improved the ability of density functional theory (DFT) to model these systems, substantial quantitative and even qualitative failures remain. In this contribution we show how a many-body description of vdW interactions can dramatically improve the accuracy of DFT for molecular materials, yielding quantitative description of stabilities and polymorphism for these challenging systems. Moreover, the role of many-body vdW interactions goes beyond stabilities to response properties. In particular, we have studied the elastic properties of a series of molecular crystals, finding that many-body vdW interactions can account for up to 30% of the elastic response, leading to quantitative and qualitative changes in elastic behavior. We will illustrate these crucial effects with the challenging case of the polymorphs of aspirin, leading to a better understanding of the conflicting experimental and theoretical studies of this system.
Elastic properties of gas hydrate-bearing sediments
Lee, M.W.; Collett, T.S.
2001-01-01
Downhole-measured compressional- and shear-wave velocities acquired in the Mallik 2L-38 gas hydrate research well, northwestern Canada, reveal that the dominant effect of gas hydrate on the elastic properties of gas hydrate-bearing sediments is as a pore-filling constituent. As opposed to high elastic velocities predicted from a cementation theory, whereby a small amount of gas hydrate in the pore space significantly increases the elastic velocities, the velocity increase from gas hydrate saturation in the sediment pore space is small. Both the effective medium theory and a weighted equation predict a slight increase of velocities from gas hydrate concentration, similar to the field-observed velocities; however, the weighted equation more accurately describes the compressional- and shear-wave velocities of gas hydrate-bearing sediments. A decrease of Poisson's ratio with an increase in the gas hydrate concentration is similar to a decrease of Poisson's ratio with a decrease in the sediment porosity. Poisson's ratios greater than 0.33 for gas hydrate-bearing sediments imply the unconsolidated nature of gas hydrate-bearing sediments at this well site. The seismic characteristics of gas hydrate-bearing sediments at this site can be used to compare and evaluate other gas hydrate-bearing sediments in the Arctic.
NASA Astrophysics Data System (ADS)
Ramanna, J.; Yedukondalu, N.; Ramesh Babu, K.; Vaitheeswaran, G.
2013-06-01
We report the structural, elastic, electronic, and optical properties of antiperovskite alkali metal oxyhalides Na3OCl, Na3OBr, and K3OBr using two different density functional methods within generalized gradient approximation (GGA). Plane wave pseudo potential (PW-PP) method has been used to calculate the ground state structural and elastic properties while the electronic structure and optical properties are calculated explicitly using full potential-linearized augmented plane wave (FP-LAPW) method. The calculated ground state properties of the investigated compounds agree quite well with the available experimental data. The predicted elastic constants using both PW-PP and FP-LAPW methods are in good accord with each other and show that the materials are mechanically stable. The low values of the elastic moduli indicate that these materials are soft in nature. The bulk properties such as shear moduli, Young's moduli, and Poisson's ratio are derived from the calculated elastic constants. Tran-Blaha modified Becke-Johnson (TB-mBJ) potential improves the band gaps over GGA and Engel-Vosko GGA. The computed TB-mBJ electronic band structure reveals that these materials are direct band gap insulators. The complex dielectric function of the metal oxyhalide compounds have been calculated and the observed prominent peaks are analyzed through the TB-mBJ electronic structures. By using the knowledge of complex dielectric function other important optical properties including absorption, reflectivity, refractive index and loss function have been obtained as a function of energy.
Hysteresis and the Dynamic Elasticity of Consolidated Granular Materials
NASA Astrophysics Data System (ADS)
Guyer, R. A.; Tencate, James; Johnson, Paul
1999-04-01
Quasistatic elasticity measurements on rocks show them to be strikingly nonlinear and to have elastic hysteresis with end point memory. When the model for this quasistatic elasticity is extended to the description of nonlinear dynamic elasticity the elastic elements responsible for the hysteresis dominate the behavior. Consequently, in a resonant bar, driven to nonlinearity, the frequency shift and the attenuation are predicted to be nonanalytic functions of the strain field. A resonant bar experiment yielding results in substantial qualitative and quantitative accord with these predictions is reported.
Hardrock Elastic Physical Properties: Birch's Seismic Parameter Revisited
NASA Astrophysics Data System (ADS)
Wu, M.; Milkereit, B.
2014-12-01
Identifying rock composition and properties is imperative in a variety of fields including geotechnical engineering, mining, and petroleum exploration, in order to accurately make any petrophysical calculations. Density is, in particular, an important parameter that allows us to differentiate between lithologies and estimate or calculate other petrophysical properties. It is well established that compressional and shear wave velocities of common crystalline rocks increase with increasing densities (i.e. the Birch and Nafe-Drake relationships). Conventional empirical relations do not take into account S-wave velocity. Physical properties of Fe-oxides and massive sulfides, however, differ significantly from the empirical velocity-density relationships. Currently, acquiring in-situ density data is challenging and problematic, and therefore, developing an approximation for density based on seismic wave velocity and elastic moduli would be beneficial. With the goal of finding other possible or better relationships between density and the elastic moduli, a database of density, P-wave velocity, S-wave velocity, bulk modulus, shear modulus, Young's modulus, and Poisson's ratio was compiled based on a multitude of lab samples. The database is comprised of isotropic, non-porous metamorphic rock. Multi-parameter cross plots of the various elastic parameters have been analyzed in order to find a suitable parameter combination that reduces high density outliers. As expected, the P-wave velocity to S-wave velocity ratios show no correlation with density. However, Birch's seismic parameter, along with the bulk modulus, shows promise in providing a link between observed compressional and shear wave velocities and rock densities, including massive sulfides and Fe-oxides.
Elastic properties of a porous titanium-bone tissue composite.
Rubshtein, A P; Makarova, E B; Rinkevich, A B; Medvedeva, D S; Yakovenkova, L I; Vladimirov, A B
2015-01-01
The porous titanium implants were introduced into the condyles of tibias and femurs of sheep. New bone tissue fills the pore, and the porous titanium-new bone tissue composite is formed. The duration of composite formation was 4, 8, 24 and 52 weeks. The formed composites were extracted from the bone and subjected to a compression test. The Young's modulus was calculated using the measured stress-strain curve. The time dependence of the Young's modulus of the composite was obtained. After 4 weeks the new bone tissue that filled the pores does not affect the elastic properties of implants. After 24 and 52 weeks the Young's modulus increases by 21-34% and 62-136%, respectively. The numerical calculations of the elasticity of porous titanium-new bone tissue composite were conducted using a simple polydisperse model that is based on the consideration of heterogeneous structure as a continuous medium with spherical inclusions of different sizes. The kinetics of the change in the elasticity of the new bone tissue is presented via the intermediate characteristics, namely the relative ultimate tensile strength or proportion of mature bone tissue in the bone tissue. The calculated and experimentally measured values of the Young's modulus of the composite are in good agreement after 8 weeks of composite formation. The properties of the porous titanium-new bone tissue composites can only be predicted when data on the properties of new bone tissue are available after 8 weeks of contact between the implant and the native bone. PMID:25953540
Analytical modeling of elastic-plastic wave behavior near grain boundaries in crystalline materials
Loomis, Eric; Greenfield, Scott; Luo, Shengnian; Swift, Damian; Peralta, Pedro
2009-01-01
It is well known that changes in material properties across an interface will produce differences in the behavior of reflected and transmitted waves. This is seen frequently in planar impact experiments, and to a lesser extent, oblique impacts. In anisotropic elastic materials, wave behavior as a function of direction is usually accomplished with the aid of velocity surfaces, a graphical method for predicting wave scattering configurations. They have expanded this method to account for inelastic deformation due to crystal plasticity. The set of derived equations could not be put into a characteristic form, but instead led to an implicit problem. to overcome this difficulty an algorithm was developed to search the parameters space defined by a wave normal vector, particle velocity vector, and a wave speed. A solution was said to exist when a set from this parameter space satisfied the governing vector equation. Using this technique they can predict the anisotropic elastic-plastic velocity surfaces and grain boundary scattering configuration for crystalline materials undergoing deformation by slip. Specifically, they have calculated the configuration of scattered elastic-plastic waves in anisotropic NiAl for an incident compressional wave propagating along a <111> direction and contacting a 45 degree inclined grain boundary and found that large amplitude transmitted waves exist owing to the fact that the wave surface geometry forces it to propagate near the zero Schmid factor direction <100>.
NASA Astrophysics Data System (ADS)
M, Shakil; Muhammad, Zafar; Shabbir, Ahmed; Muhammad Raza-ur-rehman, Hashmi; M, A. Choudhary; T, Iqbal
2016-07-01
The plane wave pseudo-potential method was used to investigate the structural, electronic, and elastic properties of CdSe1‑x Te x in the zinc blende phase. It is observed that the electronic properties are improved considerably by using LDA+U as compared to the LDA approach. The calculated lattice constants and bulk moduli are also comparable to the experimental results. The cohesive energies for pure CdSe and CdTe binary and their mixed alloys are calculated. The second-order elastic constants are also calculated by the Lagrangian theory of elasticity. The elastic properties show that the studied material has a ductile nature.
Anomalous elastic buckling of layered crystalline materials in the absence of structure slenderness
NASA Astrophysics Data System (ADS)
Ren, Manrui; Liu, Yilun; Zhe Liu, Jefferson; Wang, Lifeng; Zheng, Quanshui
2016-03-01
Layered crystalline materials, such as graphene, boron nitride, tungsten sulfate, phosphorene, etc., have attracted enormous attentions, due to their unique crystal structures and superior mechanical, thermal, and physical properties. Making use of mechanical buckling is a promising route to control their structural morphology and thus tune their physical properties, giving rise to many novel applications. In this paper, we employ molecular dynamics (MD) simulations and theoretical modeling to study the compressive buckling of a column made of layered crystalline materials with the crystal layers parallel to the compressive direction. We find that the mechanical buckling of the layered crystalline materials exhibits two anomalous and counter-intuitive features as approaching the zero slenderness ratio. First, the critical buckling strain εcr has a finite value that is much lower than the material's elastic limit strain. A continuum mechanics model (by homogenizing the layered materials) is proposed for the εcr, which agrees well with the results of MD simulations. We find that the εcr solely depends on elastic constants without any structural dimension, which appears to be an intrinsic material property and thus is defined as intrinsic buckling strain (IBS), εcrIBS , in this paper. Second, below a certain nanoscale length, l0, in the compressive direction (e.g., about 20 nm for graphite), the critical buckling strain εcr shows a size effect, i.e., increasing as the column length L decreases. To account for the size effect, inspired by our recently developed multi-beam shear model (Liu et al., 2011), a bending energy term of individual crystal layer is introduced in our continuum model. The theoretical model of εcr agrees well with the size effects observed in MD simulations. This study could lay a ground for engineering layered crystalline materials in various nano-materials and nano-devices via mechanical buckling.
Phase stability and elastic properties of Cr-V alloys
Gao, M C; Suzuki, Y; Schweiger, H; Doğan, Ö N; Hawk, J; Widom, M
2013-01-23
V is the only element in the periodic table that forms a complete solid solution with Cr and thus is particularly important in alloying strategy to ductilize Cr. This study combines first-principles density functional theory calculations and experiments to investigate the phase stability and elastic properties of Cr–V binary alloys. The cluster expansion study reveals the formation of various ordered compounds at low temperatures that were not previously known. These compounds become unstable due to the configurational entropy of bcc solid solution as the temperature is increased. The elastic constants of ordered and disordered compounds are calculated at both T = 0 K and finite temperatures. The overall trends in elastic properties are in agreement with measurements using the resonant ultrasound spectroscopy method. The calculations predict that addition of V to Cr decreases both the bulk modulus and the shear modulus, and enhances the Poisson’s ratio, in agreement with experiments. Decrease in the bulk modulus is correlated to decrease in the valence electron density and increase in the lattice constant. An enhanced Poisson’s ratio for bcc Cr–V alloys (compared to pure Cr) is associated with an increased density of states at the Fermi level. Furthermore, the difference charge density in the bonding region in the (110) slip plane is highest for pure Cr and decreases gradually as V is added. The present calculation also predicts a negative Cauchy pressure for pure Cr, and it becomes positive upon alloying with V. The intrinsic ductilizing effect from V may contribute, at least partially, to the experimentally observed ductilizing phenomenon in the literature.
Elastic-plastic characterization of a cast stainless steep pipe elbow material
Joyce, J.A.; Hackett, E.M.; Roe, C.
1992-01-01
Tests conducted in Japan as part of the High Level Vibration Test (HLVT) program for reactor piping systems revealed fatigue crack growth in a cast stainless steel pipe elbow. The material tested was equivalent to ASME SA-351CF8M. The David Taylor Research Center (DTRC) was tasked to developed the appropriate material property data to characterize cyclic deformation, cyclic elastic-plastic crack growth and ductile tearing resistance in the pipe elbow material. It was found that the cast stainless steel was very resistant to ductile crack extension. J-R curves essentially followed a blunting behavior to very high J levels. Low cycle fatigue crack growth rate data obtained on this material using a cyclic J integral approach was consistent with the high cycle fatigue crack growth rate and with a standard textbook correlation equation typical for this type of material. Evaluation of crack closure effects was essential to accurately determine the crack driving force for cyclic elastic- plastic crack growth in this material. SEM examination of several of the cyclic J test fracture surfaces indicated that fatigue was the primary mode of fracture with ductile crack extension intervening only during the last few cycles of loading.
Telschow, Kenneth Louis; Deason, Vance Albert
2002-12-01
An important material property in the paper industry is the anisotropic stiffness distribution due to the fibrous microstructure of paper and to processing procedures. Ultrasonic methods offer a means of determining the stiffness of sheets of paper from the anisotropic propagation characteristics of elastic Lamb waves along the machine direction and the cross direction. That is, along and perpendicular to the direction of paper production. Currently, piezoelectric ultrasonic methods are employed in the industry to measure the elastic polar diagram of paper through multiple contacting measurements made in all directions. This paper describes a new approach utilizing the INEEL Laser Ultrasonic Camera to provide a complete image of the elastic waves traveling in all directions in the plane of the paper sheet. This approach is based on optical dynamic holographic methods that record the out of plane ultrasonic motion over the entire paper surface simultaneously without scanning. The full-field imaging technique offers great potential for increasing the speed of the measurement and it ultimately provides a substantial amount of information concerning local property variations and flaws in the paper. This report shows the success of the method and the manner in which it yields the elastic polar diagram for the paper from the dispersive flexural or antisymmetric Lamb wave.
Silicon carbide nanowires: Elastic properties, defects, and surface formations
NASA Astrophysics Data System (ADS)
Rich, Ryan Michael
A highly reproducible method of producing SiC nanowires on a large scale is presented, and the average size of SiC nanowires was 30 nm. XRD revealed that the molar yield increased linearly with time. TEM showed a distribution of nanowire sizes that shifted towards larger diameters as sintering time increased. It is known that vapor-liquid-solid reactions involving a metal catalyst play a role in their formation, and there is further evidence that a vapor-solid mechanism contributes as well. The elastic properties of the following SiC morphologies were explored with pressure applied via a diamond anvil cell: 20 nm grains, 50 nm grains, 130 nm grains, and 30 nm nanowires The bulk modulus of nanowires increased by 8%, while that of 20 nm grains increased 30% in comparison to bulk material. The increased bulk modulus is explained by the core-shell model, where nanoparticles possess one or more distinct regions near the surface with identical crystal symmetry but different interatomic distances. Defects may also affect the bulk modulus, especially in the heavily faulted nanowires. As seen by TEM, planar faults were abundant, and their quantity decreased with decreasing diameter. The extended Convolutional Multiple Whole Profile (eCMWP) analysis was employed to quantitate the defects by XRD. This analysis concluded that twins are the most frequently occurring planar fault with a 2.20% probability of formation, which corresponds to a defect spacing of 38 nm. SiC nanowires are formed with an amorphous outer layer a few nanometers deep. It was concluded that the layer consisted mainly of amorphous SiC, but EDS confirmed that this structure was rich in oxygen. FTIR confirmed the presence of Si-O bands which increased in population with thermal treatment. The surface of SiC nanowires was modified by etching in HF and HNO3 acids. Silica bands were reduced and functional groups appeared after treatment. XRD found that grain size increased by 186% and dislocations decreased by
NASA Astrophysics Data System (ADS)
Mozafari, E.; Shulumba, N.; Steneteg, P.; Alling, B.; Abrikosov, Igor A.
2016-08-01
We present a theoretical scheme to calculate the elastic constants of magnetic materials in the high-temperature paramagnetic state. Our approach is based on a combination of disordered local moments picture and ab initio molecular dynamics (DLM-MD). Moreover, we investigate a possibility to enhance the efficiency of the simulations of elastic properties using the recently introduced method: symmetry imposed force constant temperature-dependent effective potential (SIFC-TDEP). We have chosen cubic paramagnetic CrN as a model system. This is done due to its technological importance and its demonstrated strong coupling between magnetic and lattice degrees of freedom. We have studied the temperature-dependent single-crystal and polycrystalline elastic constants of paramagentic CrN up to 1200 K. The obtained results at T = 300 K agree well with the experimental values of polycrystalline elastic constants as well as the Poisson ratio at room temperature. We observe that the Young's modulus is strongly dependent on temperature, decreasing by ˜14 % from T = 300 K to 1200 K. In addition we have studied the elastic anisotropy of CrN as a function of temperature and we observe that CrN becomes substantially more isotropic as the temperature increases. We demonstrate that the use of Birch law may lead to substantial errors for calculations of temperature induced changes of elastic moduli. The proposed methodology can be used for accurate predictions of mechanical properties of magnetic materials at temperatures above their magnetic order-disorder phase transition.
Temperature dependence of elastic properties in alkali borate binary glasses
NASA Astrophysics Data System (ADS)
Kawashima, Mitsuru; Matsuda, Yu; Kojima, Seiji
2011-05-01
The elastic properties of alkali borate glasses, xM 2O·(100 - x)B 2O 3 (M = Li, Na, K, Rb, Cs, x = 14, 28), have been investigated by Brillouin scattering spectroscopy from room temperature up to 1100 °C. Above the glass transition temperature, Tg, the longitudinal sound velocity, VL, decreases markedly on heating. Such significant changes of the elastic properties result from the breakdown of the glass network above Tg. Alkali borate family with the same x shows the similar behavior in the temperature variations of VL up to around Tg. The absorption coefficient, αL, increases gradually above Tg. With the increase of the size of an alkali ion, the slope of VL just above Tg decreases. Since the fragility is related to the slope, the present results suggest that the fragility of alkali borate glasses increases as the size of alkali ion decreases. Such an alkali dependence of the fragility is discussed on the basis of the fluctuation of the boron coordination number.
Elastic properties of low density core (LDC) Ti-6Al-4V sandwich cores
Queheillalt, D.T.; Wadley, H.N.G.; Schwartz, D.S.
1998-12-31
Lightweight, structurally efficient low density core (LDC) sandwich structures can be produced by entrapping argon gas within a finely dispersed distribution of pores in a microstructure and using a high temperature anneal to cause pore growth by gas expansion. This results in a porous microstructure with a relative density as low as {approximately}0.70. Laser ultrasonic methods have been used to measure the longitudinal and shear wave velocities and hence the elastic properties of LDC Ti-6Al-4V cores prior to, and after gas expansion treatments of up to 48 hr at 920 C. The data were compared with several analytical models for predicting the volume fraction of porosity dependent elastic properties of porous materials.
NASA Astrophysics Data System (ADS)
Abramovich, A.
2012-12-01
Cermets is a ceramic-metal composite usually produced by sintering a precompacted mixture of the initial powders. These composite materials were created for industrial applications to produce engineering structures possessing a high strength, thermal stability and resistance to aggressive media. In the present work elastic properties of cermets samples, obtained by sintering of corundum (α-Al2O3) and stainless steel powders were investigated in dependence on steel concentration 5 - 35% wt. and on temperature of sintering in vacuum 1400-1700°C. It was stated that values of elastic moduli are in complex dependence on concentration and temperature, reach maxima at steel concentration 15 - 20% wt. and increase with sintering temperature rise. In the work also the results of cermets microstructure researches and discussion of these results are presented. The results are discussed from stand view of ultrasound propagation through medium having grain boundaries which influence on the physical properties of composite.
Structural, elastic, electronic and optical properties of new layered semiconductor BaGa2P2
NASA Astrophysics Data System (ADS)
Bouhemadou, A.; Khenata, R.; Bin-Omran, S.; Murtaza, G.; Al-Douri, Y.
2015-08-01
We report the results of a detailed first-principles based density functional theory study of the structural, elastic, electronic and optical properties of a recently synthesized layered semiconductor BaGa2P2. The optimized structural parameters are in excellent agreement with the experimental structural findings, which validates the used theoretical method. The single crystal and polycrystalline elastic constants are numerically estimated using the strain-stress method and Voigt-Reuss-Hill approximations. Predicted values of the elastic constants suggest that the considered material is mechanically stable, brittle and very soft material. The three-dimensional surface and its planar projections of Young's modulus are visualized to illustrate the elastic anisotropy. It is found that Young's modulus of BaGa2P2 show strong dependence on the crystallographic directions. Band structure calculation reveals that BaGa2P2 is a direct energy band gap semiconductor. The effective masses of electrons and holes at the minimum of the conduction band and maximum of the valence band are numerically estimated. The density of state, charge density distribution and charge transfers are calculated and analyzed to determine the chemical bonding nature. Dielectric function, refractive index, extinction coefficient, absorption coefficient, reflectivity and electron-loss energy function spectra are computed for a wide photon energy range up to 20 eV. Calculated optical spectra exhibit a noticeable anisotropy.
NASA Astrophysics Data System (ADS)
Saha, Sourav; Mojumder, Satyajit; Mahboob, Monon; Islam, M. Zahabul
2016-07-01
Tungsten is a promising material and has potential use as battery anode. Tungsten nanowires are gaining attention from researchers all over the world for this wide field of application. In this paper, we investigated effect of temperature and geometric parameters (diameter and aspect ratio) on elastic properties of Tungsten nanowire. Aspect ratios (length to diameter ratio) considered are 8:1, 10:1, and 12:1 while diameter of the nanowire is varied from 1-4 nm. For 2 nm diameter sample (aspect ratio 10:1), temperature is varied (10K ~ 1500K) to observe elastic behavior of Tungsten nanowire under uniaxial tensile loading. EAM potential is used for molecular dynamic simulation. We applied constant strain rate of 109 s-1 to deform the nanowire. Elastic behavior is expressed through stress vs. strain plot. We also investigated the fracture mechanism of tungsten nanowire and radial distribution function. Investigation suggests peculiar behavior of Tungsten nanowire in nano-scale with double peaks in stress vs. strain diagram. Necking before final fracture suggests that actual elastic behavior of the material is successfully captured through atomistic modeling.
Upscaling of elastic properties for large scale geomechanical simulations
NASA Astrophysics Data System (ADS)
Chalon, F.; Mainguy, M.; Longuemare, P.; Lemonnier, P.
2004-09-01
Large scale geomechanical simulations are being increasingly used to model the compaction of stress dependent reservoirs, predict the long term integrity of under-ground radioactive waste disposals, and analyse the viability of hot-dry rock geothermal sites. These large scale simulations require the definition of homogenous mechanical properties for each geomechanical cell whereas the rock properties are expected to vary at a smaller scale. Therefore, this paper proposes a new methodology that makes possible to define the equivalent mechanical properties of the geomechanical cells using the fine scale information given in the geological model. This methodology is implemented on a synthetic reservoir case and two upscaling procedures providing the effective elastic properties of the Hooke's law are tested. The first upscaling procedure is an analytical method for perfectly stratified rock mass, whereas the second procedure computes lower and upper bounds of the equivalent properties with no assumption on the small scale heterogeneity distribution. Both procedures are applied to one geomechanical cell extracted from the reservoir structure. The results show that the analytical and numerical upscaling procedures provide accurate estimations of the effective parameters. Furthermore, a large scale simulation using the homogenized properties of each geomechanical cell calculated with the analytical method demonstrates that the overall behaviour of the reservoir structure is well reproduced for two different loading cases. Copyright
Accounting for the elastic properties of viscoplastic lubricant between coaxial rotating cylinders
NASA Astrophysics Data System (ADS)
Begun, A. S.; Burenin, A. A.; Zhilin, S. G.; Kovtanyuk, L. V.
2015-05-01
This paper presents a solution of the boundary-value problem of the stress-strain state of a friction unit placed in the gap between rigid rotating cylinders. It is assumed that the two-layer incompressible material of these unit has elastic, viscous, and plastic properties and different values of the elastic moduli, stress limit, and viscosity. The conditions of the occurrence of viscoplastic flow, motion of the elastoplastic boundary in a deformable medium, and interaction of the latter with the contact boundary of the materials were determined. Limiting values of the characteristic rotation parameters at which the damping layer of the friction unit is not deformed plastically are given. The velocity and stress fields for acceleration and deceleration of the lubricant flow are calculated.
A first principle study of the pressure dependent elastic properties of monazite LaPO4
NASA Astrophysics Data System (ADS)
Ali, Kawsar; Arya, A.; Ghosh, P. S.; Dey, G. K.
2016-05-01
DFT based ab-initio simulations have been performed to study the effect of pressure on the elastic properties of monazite LaPO4 which is a promising host material for immobilization of high level nuclear waste. The phase is found to be stable up to 30 GPa. The calculated polycrystalline bulk, shear and Young moduli show an increasing trend as a function of pressure. The ductility and anisotropy in shear modulus of the material have been found to increase with pressure; whilethe bulk modulus anisotropy decreases with pressure.
Galo, Rodrigo; Contente, Marta Maria Martins Giamatei; Galafassi, Daniel; Borsatto, Maria Cristina
2015-01-01
Objectives: The purpose of this study was to determine the Young's modulus and the hardness of deciduous and permanent teeth following wear challenges using different dental materials. Materials and Methods: Wear challenges were performed against four dental materials: A resin-based fissure sealant (Fluoroshield®), a glass ionomer based fissure sealant (Vitremer®), and two microhybrid composite resins (Filtek Z250 and P90®). Using the pin-on-plate design, a deciduous or a permanent tooth was made into a pin (4 mm × 4 mm × 2 mm) working at a 3 N vertical load, 1 Hz frequency, and 900 cycles (15 min) with Fusayama artificial saliva as a lubricant. Before and after the tribological tests, the hardness and elasticity modulus of the tooth samples were measured by creating a nanoindentation at load forces up to 50 mN and 150 mN. All of the results were statistically analyzed using ANOVA and post-hoc Duncan's tests (P < 0.05). Results: No difference in hardness was encountered between deciduous and permanent teeth (P < 0.05) or modulus of elasticity (P < 0.05) before or after the wear challenges for all of the dental materials tested. Conclusions: Wear challenges against the studied dental materials did not alter the properties of permanent or deciduous teeth after the application of a 3 N load. PMID:26929700
Hard tissue as a composite material. I - Bounds on the elastic behavior.
NASA Technical Reports Server (NTRS)
Katz, J. L.
1971-01-01
Recent determination of the elastic moduli of hydroxyapatite by ultrasonic methods permits a re-examination of the Voigt or parallel model of the elastic behavior of bone, as a two phase composite material. It is shown that such a model alone cannot be used to describe the behavior of bone. Correlative data on the elastic moduli of dentin, enamel and various bone samples indicate the existence of a nonlinear dependence of elastic moduli on composition of hard tissue. Several composite models are used to calculate the bounds on the elastic behavior of these tissues. The limitations of these models are described, and experiments to obtain additional critical data are discussed.
Elastic Properties of Polymerised and Fluid Membranes Under Stress
NASA Astrophysics Data System (ADS)
Shillcock, Julian Charles
The stability of a living cell relies on the properties and interrelations of its constituent parts. The fluid bilayer surrounding the cell separates the cytoplasm inside the cell from the extracellular environment. A cross-linked network of proteins within the cytoplasm supports the fluid bilayer and contributes to the cell's elasticity. Three properties relating to the behaviour of a model fluid bilayer and polymerised network are investigated by Monte Carlo simulation: the phase behaviour of a system of discotic liquid crystal molecules, the elastic properties of a model polymerised network, and the stability and rupture of a model fluid membrane. The isotropic to nematic transition induced by hydrostatic pressure in a system of discotic liquid cystal molecules in three dimensions is presented. The study concentrates on the phase behaviour resulting from the anisotropy of the disks. The transition is present for disks whose thickness to radius ratio is less than 40%, but is absent for thicker disks. A more specialised model of disks restricted to intersect a planar interface between two immiscible fluids is investigated, but has no isotropic -nematic phase transition at finite temperature. The elastic properties of a two-dimensional, triangulated network of Hookean springs are investigated as a function of temperature and applied tension. The compression modulus decreases, and the shear modulus increases, as the tension on the network is increased. The elastic properties of self-avoiding networks at low temperature are well described by a mean field theory. When the self-avoidance constraint is removed, the network undergoes a phase transition to a collapsed state of small area as the tension is reduced to zero. Both types of network show an unstable expansion of their area when the stretching tension exceeds a specified value. Both networks also have the unusual property (referred to as a negative Poisson ratio) of expanding transversely when stretched
NASA Astrophysics Data System (ADS)
Stoynov, Yonko
2015-11-01
Functionally graded materials are composite materials with continuously variable material properties. They possess huge potential for applications in modern industry, because of their enhanced qualities: thermal barrier effects, protection from corrosion and oxidation, improved toughness and stress. In our research we consider functionally graded magneto-electro-elastic materials with cracks, subjected to anti-plane wave and evaluate stress concentration near the crack tips in this type of materials with respect to external loading for different material grading. Boundary integral equation method (BIEM) is used for the numerical solution. Numerical examples are presented to show the dependence between the stress intensity factors and the frequency of the applied dynamic load.
Anisotropic Elastic Properties of Muscle-like Nematic Elastomers
NASA Astrophysics Data System (ADS)
Ratna, Banahalii; Thomseniii, Donald L.; Shenoy, Devanand; Srinivasan, Amritha; Keller, Patrick
2001-03-01
De Gennes suggested in 1997 that the liquid crystal elastomers are an excellent framework to mimic muscular action. We have prepared anisotropic freestanding films of nematic elastomers from laterally attached side-chain polymers that show muscle-like mechanical properties. The orientational order of the liquid crystal side groups imposes a conformational anisotropy in the polymer backbone. When the order parameter drops at the nematic-isotropic phase transition, there is a concomitant loss of order in the backbone which results in a contraction of the film in the direction of the director orientation. Dynamic mechanical data along directions parallel and perpendicular to the optic axis, show anisotropic stress-strain behavior. The film exhibits soft elasticity when strained in the perpendicular direction when the liquid crystal mesogens reorient without appreciable stress build up. Thermostrictive studies in the parallel direction show 40constriction at the nematic-isotropic phase transition. Isometric studies show that the elastic energy stored is purely entropic in origin and the elastomer acts like a spring with unusually large spring constant at the NI transition. The maximum stress measured is 300kPa. A strain rate of 5s-1 is estimated from shear relaxation studies.
An In-Depth Tutorial on Constitutive Equations for Elastic Anisotropic Materials
NASA Technical Reports Server (NTRS)
Nemeth, Michael P.
2011-01-01
An in-depth tutorial on the constitutive equations for elastic, anisotropic materials is presented. Basic concepts are introduced that are used to characterize materials, and notions about how anisotropic material deform are presented. Hooke s law and the Duhamel-Neuman law for isotropic materials are presented and discussed. Then, the most general form of Hooke s law for elastic anisotropic materials is presented and symmetry requirements are given. A similar presentation is also given for the generalized Duhamel-Neuman law for elastic, anisotropic materials that includes thermal effects. Transformation equations for stress and strains are presented and the most general form of the transformation equations for the constitutive matrices are given. Then, specialized transformation equations are presented for dextral rotations about the coordinate axes. Next, concepts of material symmetry are introduced and criteria for material symmetries are presented. Additionally, engineering constants of fully anisotropic, elastic materials are derived from first principles and the specialized to several cases of practical importance.
Visco-Elastic Properties of Sodium Hyaluronate Solutions
NASA Astrophysics Data System (ADS)
Kulicke, Werner-Michael; Meyer, Fabian; Bingöl, Ali Ö.; Lohmann, Derek
2008-07-01
Sodium Hyaluronate (NaHA) is a member of the glycosaminoglycans and is present in the human organism as part of the synovial fluid and the vitreous body. HA is mainly commercialized as sodium or potassium salt. It can be extracted from cockscombs or can be produced by bacterial fermentation ensuring a low protein content. Because of its natural origin and toxicological harmlessness, NaHA is used to a great extent for pharmaceutical and cosmetic products. In medical applications, NaHA is already being used as a component of flushing and stabilizing fluids in the treatment of eye cataract and as a surrogate for natural synovial fluid. Another growing domain in the commercial utilization of NaHA is the field of skin care products like dermal fillers or moisturizers. In this spectrum, NaHA is used in dilute over semidilute up to concentrated (0
Stability, elastic and electronic properties of palladium nitride.
Chen, W; Tse, J S; Jiang, J Z
2010-01-13
The crystal structure, stability, elastic constants and electronic properties of PdN(2) for four polymorph structures: pyrite, marcasite, CoSb(2) and ST(AA), have been investigated using first-principles calculations. At zero pressure all four polymorphs are metallic and thermodynamically unstable but mechanically stable. Pyrite PdN(2) is found to be the lowest energy phase. It is metallic at ambient pressure but becomes a semiconductor at pressures higher than 18 GPa. The calculated phonon band structures of pyrite PdN(2) show the structure is dynamically stable up to 60 GPa. Good agreement between calculated and observed Raman frequencies was found, indicating that the recently synthesized palladium nitride at high pressure is likely to have a pyrite structure. PMID:21386226
Stability, elastic and electronic properties of palladium nitride
NASA Astrophysics Data System (ADS)
Chen, W.; Tse, J. S.; Jiang, J. Z.
2010-01-01
The crystal structure, stability, elastic constants and electronic properties of PdN2 for four polymorph structures: pyrite, marcasite, CoSb2 and STAA, have been investigated using first-principles calculations. At zero pressure all four polymorphs are metallic and thermodynamically unstable but mechanically stable. Pyrite PdN2 is found to be the lowest energy phase. It is metallic at ambient pressure but becomes a semiconductor at pressures higher than 18 GPa. The calculated phonon band structures of pyrite PdN2 show the structure is dynamically stable up to 60 GPa. Good agreement between calculated and observed Raman frequencies was found, indicating that the recently synthesized palladium nitride at high pressure is likely to have a pyrite structure.
Elastic properties and atomic bonding character in metallic glasses
NASA Astrophysics Data System (ADS)
Rouxel, T.; Yokoyama, Y.
2015-07-01
The elastic properties of glasses from different metallic systems were studied in the light of the atomic packing density and bonding character. We found that the electronegativity mismatch (Δe-) between the host- and the major solute-elements provides a plausible explanation to the large variation observed for Poisson's ratio (ν) among metallic glasses (MGs) (from 0.28 for Fe-based to 0.43 for Pd-based MGs), notwithstanding a similar atomic packing efficiency (Cg). Besides, it is found that ductile MGs correspond to Δe- smaller than 0.5 and to a relatively steep atomic potential well. Ductility is, thus, favored in MGs exhibiting a weak bond directionality on average and opposing a strong resistance to volume change.
NASA Astrophysics Data System (ADS)
Hemzalová, P.; Friák, M.; Šob, M.; Ma, D.; Udyansky, A.; Raabe, D.; Neugebauer, J.
2013-11-01
We have employed parameter-free density functional theory calculations to study the thermodynamic stability and structural parameters as well as elastic and electronic properties of Ni4N in eight selected crystallographic phases. In agreement with the experimental findings, the cubic structure with Pearson symbol cP5, space group Pm3¯m (221) is found to be the most stable and it is also the only thermodynamically stable structure at T=0 K with respect to decomposition to the elemental Ni crystal and N2 gas phase. We determine structural parameters, bulk moduli, and their pressure derivatives for all eight allotropes. The thermodynamic stability and bulk modulus is shown to be anticorrelated. Comparing ferromagnetic and nonmagnetic states, we find common features between the magnetism of elemental Ni and studied ferromagnetic Ni4N structures. For the ground-state Ni4N structure and other two Ni4N cubic allotropes, we predict a complete set of single-crystalline elastic constants (in the equilibrium and under hydrostatic pressure), the Young and area moduli, as well as homogenized polycrystalline elastic moduli obtained by different homogenization methods. We demonstrate that the elastic anisotropy of the ground-state Ni4N is qualitatively opposite to that in the elemental Ni, i.e., these materials have hard and soft crystallographic directions interchanged. Moreover, one of the studied metastable cubic phases is found auxetic, i.e., exhibiting negative Poisson ratio.
NASA Astrophysics Data System (ADS)
Menzel, Andreas M.
2016-08-01
One possibility to adjust material properties to a specific need is to embed units of one substance into a matrix of another substance. Even materials that are readily tunable during operation can be generated in this way. In (visco)elastic substances, both the matrix material as well as the inclusions and/or their immediate environment can be dynamically deformed. If the typical dynamic response time of the inclusions and their surroundings approach the macroscopic response time, their deformation processes need to be included into a dynamic macroscopic characterization. Along these lines, we present a hydrodynamic description of (visco)elastic composite materials. For this purpose, additional strain variables reflect the state of the inclusions and their immediate environment. These additional strain variables in general are not set by a coarse-grained macroscopic displacement field. Apart from that, during our derivation, we also include the macroscopic variables of relative translations and relative rotations that were previously introduced in different contexts. As a central point, our approach reveals and classifies the importance of a macroscopic variable termed relative strains. We analyze two simplified minimal example geometries as an illustration.
Quantitative microstructure characterization and elastic properties upscaling of carbonate rocks
NASA Astrophysics Data System (ADS)
Vialle, Stephanie; Lebedev, Maxim
2016-04-01
Most Rock Physics models commonly used to predict elastic properties rely on a very simplified representation of the pore and grains geometry. Initially developed for siliclastic rocks, they do not apply easily and/or with as much success, to rocks with more complicated microstructure such as carbonates, which exhibit complex relationships between geophysical attributes and rock properties, such as P-wave velocity versus porosity. Furthermore, until recently, most microstructure imaging techniques such as optical microscopy, SEM, X-ray micro-CT, etc., only give a qualitative description of the pore and grain arrangement. Nano-indentation technique is a method that gives quantitative information by mean of local (micrometer size) measurements of elastic moduli. We used this technique to obtain 300 μm * 300 μm maps of Young's moduli (around 1000 data points) of two microporous carbonates of same mineralogy but of two different microstructures. As the size of the indenter tip is much smaller than the characteristic length of the heterogeneities in microstructure, the distribution of the Young's moduli can be deconvolved into its component parts (i.e. phases). SEM imaging of the same areas than the ones mapped by nano-indentation shows correlations between type of micrite and phases of different mean Young's modulus: tight micrites exhibiting a higher Young's modulus (up to 64 GPa) than microporous micrites (as low as 9 GPa). We then investigate different ways to upscale the measurements in order to get the effective bulk and shear moduli, from simply using volume fractions of the different phases, classical Hashin-Shrikman bounds, and Hill average; to using micro-CT imaging and analysis combined with rock physics models. Though more work is still needed to render nano-indentation technique a robust method for rock physics, both on the theory behind and on the upscaling of the measurements, these results that use nano-indentation method in a statistical way are very
Thermal and elastic properties of Sr1- x A x CoO3 (A=Zn and Ho)
NASA Astrophysics Data System (ADS)
Thakur, Rasna; Thakur, Rajesh K.; Gaur, N. K.
2015-03-01
We have investigated the elastic and thermal properties for Sr1- x A x CoO3 (A=Zn, Ho, and 0≤ x≤0.4) probably for the first time, by using the modified rigid ion model (MRIM). The computed elastic constants ( C 11, C 12, C 44) are the first report on them. Using these elastic constants, we have computed other related elastic properties like the Bulk modulus ( B), Young's modulus ( Y), Shear modulus ( G), Poisson's ratio ( σ), Lame's parameter ( μ, λ), transverse, longitudinal and average wave velocity ( υ t, υ l, υ m) and Anisotropy parameter ( A). Furthermore, by the elastic stability criteria, we predict that Sr1- x A x CoO3 (A=Zn, Ho, and 0≤ x≤0.4) are mechanically stable and belongs to metallically bonding materials. Moreover, the thermodynamic properties such as the thermal expansion coefficient ( α), cohesive energy ( ϕ), molecular force constant ( f), Reststrahlen frequency ( υ), Debye temperature ( θ D), and Gruneisen parameter ( γ) have also been predicted. Besides, the variations of specific heat with temperature are reported for a wide range. To our knowledge, some of the properties are being reported for the first report on these materials.
Elastic properties of anorthite at high temperature and high pressure
NASA Astrophysics Data System (ADS)
Matsukage, K. N.; Nishihara, Y.; Noritake, F.; Tsujino, N.; Sakurai, M.; Higo, Y.; Kawamura, K.; Takahashi, E.
2012-12-01
To understand the elastic properties of subducted crustal minerals at P-T conditions of crust and upper most mantle, we performed in situ measurement of the elastic wave velocities of anorthite at temperatures up to 1100 oC at less than 2.0 GPa (in stability field) and up to 500 oC at 2.0-7.0 GPa. A fine grained polycrystalline anorthite was synthesised by using gas pressure apparatus installed at magma factory in Tokyo Institute of Technology. The quenched glass with anorthite composition was ground in ethanol and was loaded into a sealed Pt tube (3.0 mm inner diameter and 0.2 mm thickness) container. The sample was preheated at 900°C for 2 hours, and then keep at 1100°C for 20 hours at pressure of 0.3 GPa. The maximum grain size of the synthesized polycrystalline anorthite was about 15μm. The experiments were performed using the SPEED-1500 apparatus installed on beam line BL04B1 at synchrotron facility of SPring-8, Japan (Utsumi et al. 1998). The experimental design for in situ elastic wave velocities measurement at BL04B1 was presented by Higo et al. (2009). Pressure was generated by eight 26 mm tungsten carbide anvils with 11 mm truncated edge length. A Co-doped semi-sintered MgO octahedron with an 18 mm edge length was used as a pressure medium. The sample was enclosed in a BN sleeve container, and was placed in the central part (hot spot) of the furnace. Platinum foils (2.5 μm in thickness) were inserted at the both side of the sample for determination of sample length by using X-ray radiographic imaging techniques. An Al2O3 rod (5.3 mm in length and 2.0 mm in diameter) was used as buffer rod which transmit ultrasonic wave to the sample. Temperature was measured by a W97Re3-W75Re25 thermocouple. MgO was used as a pressure marker, and it was mixed with BN (MgO:BN = 1:1 by weight) to prevent grain growth at high temperatures. The ultrasonic signals were generated and received by 10oY-cut LiNbO3 transducer of 50 μm in thickness and 3.2 mm in diameter. We
Majtyka, A; Chrobak, D; Romanowski, B; Ratuszna, A; Nowak, R
2016-06-01
This paper pertains to elastic properties of InAs and GaAs semiconducting crystals containing various amounts of vacancies--the relevant issue in the case of nanostructured electronic materials. The linear relationship between elastic constants and point defects concentration deduced from our classical molecular dynamic and ab initio calculations, confirms that an increasing vacancy content results in a decrease of pertinent elastic parameters, namely the crystal elastic stiffness-tensor components, the effect called herein "the softening of material" for simplicity. The pseudo-potential-based approach provides us results compatible with the available experimental data, while the alternatively used empirical potentials failed to account for different kind of vacancies on the elastic properties of semiconductors. Our results provide an expanded insight into the problems of modeling of the properties of the defected InAs and GaAs crystal structures. This issue is of interest to nanoelectronics and production of nanomaterials currently. PMID:27427736
Elastic properties of a polyimide film determined by Brillouin scattering and mechanical techniques
Kumar, R.S.; Schuller, I.K.; Kumar, S.S.; Fartash, A.; Grimsditch, M.
1993-06-01
We discuss here the complete determination of the elastic properties of a polyimide film using two experimental techniques. One technique employs the polymer film as a vibrating membrane and allows a direct determination of the ``macroscopic`` biaxial modulus. Brillouin scattering, which measures the elastic properties on a {approximately} 100{mu} scale, allows for a complete characterization of the elastic behavior. Results obtained by the two techniques are in agreement within reported error bars.
Lakel, S.; Okbi, F.; Ibrir, M.; Almi, K.
2015-03-30
We have performed first-principles calculations to investigate the behavior under hydrostatic pressure of the structural, elastic and lattice dynamics properties of aluminum phosphide crystal (AlP), in both zinc-blende (B3) and nickel arsenide (B8) phases. Our calculated structural and electronic properties are in good agreement with previous theoretical and experimental results. The elastic constants, bulk modulus (B), shear modulus (G), and Young's modulus (E), Born effective charge and static dielectric constant ε{sub 0}, were calculated with the generalized gradient approximations and the density functional perturbation theory (DFPT). Our results in the pressure behavior of the elastic and dielectric properties of both phases are compared and contrasted with the common III–V materials. The Born effective charge ZB decreases linearly with pressure increasing, while the static dielectric constant decreases quadratically with the increase of pressure.
Elastic wave propagation in adaptive honeycomb-based materials with high connectivity
NASA Astrophysics Data System (ADS)
Zhu, Zhi-Wei; Deng, Zi-Chen
2016-08-01
Beam-type periodic materials with high connectivity have displayed unique band gap behaviors analogous to locally resonant band gaps in acoustic metamaterials. In this study, structurally square re-entrant honeycomb, one highly connected lattice configuration featuring eight folded beams connected at each joint, is introduced to be the host structure of a smart material to tailor the elastic wave propagation. Finite length piezoelectric patches connected with negative capacitance shunting circuits are arranged on the beam surfaces, providing active adjustment via altering the parameters of shunting circuits. The characteristics of band structure of this smart structured material are investigated through the application of finite element method in conjunction with the Bloch theorem. Results demonstrate that the variation of internally resonant band gaps induced by the alteration of the piezoelectric patches to those positions and mechanical properties, can be precisely estimated by simple heuristic models proposed according to deformation characteristics of standing wave modes. This founding could promote the practical implementation of the highly connected honeycombs in the adaptive control to elastic wave.
Elastic properties of the transition metal oxides Ca2-xSrxRuO4
NASA Astrophysics Data System (ADS)
Luan, Yanbing; Keppens, Veerle; Jin, Rongying; Mandrus, David
2008-03-01
Layered perovskite ruthenates have attracted considerable interest since the discovery of superconductivity in Sr2RuO4, the only copper-free superconductor isostructural to the cuprates. Among the doped varieties of Sr2RuO4, the Ca2-xSrxRuO4 series is heavily studied, as it connects the Mott insulator Ca2RuO4 with the superconductor Sr2RuO4 and exhibits a variety of physical properties. The current work focuses on the elastic properties of Ca2-xSrxRuO4. Resonant Ultrasound Spectroscopy (RUS) has been used to study the elastic response of the samples, and results are presented for single crystals with x = 0.2, 0.3, 0.4, 0.5, 1, 1.5, 1.9 and 2.0. The temperature-dependence of the elastic behavior is found to be quite unusual and reflects the rich phase diagram of these materials. Almost all measured Ca2-xSrxRuO4 samples show a soft phonon mode at low temperatures, which is believed to be associated with the dynamics of the RuO6 octahedra.
Room temperature elastic properties of Rh-based alloys studied by surface Brillouin scattering
NASA Astrophysics Data System (ADS)
Sumanya, C.; Mathe, B. A.; Comins, J. D.; Every, A. G.; Osawa, M.; Harada, H.
2014-10-01
Platinum metal group alloys are promising materials for use in a new generation of gas turbine engines owing to their excellent high-temperature properties. In the present work, room temperature elastic properties of single crystals of Rh3Nb and Rh3Zr are investigated. Surface Brillouin scattering spectra for a range of wave vector directions on the (001) surface have been acquired in order to determine the angular variation of the velocities of the Rayleigh and pseudo-surface acoustic waves and that of the longitudinal lateral wave (LLW) threshold within the Lamb shoulder. The elastic stiffness constants C11, C12, and C44 of these cubic crystal specimens have been derived using two approaches: the first involving the least-squares fit of the combined measured wave velocity data to calculated values and the second an analytical approach using the Rayleigh velocities in the [100] and [110] directions and LLW velocity in the [100] direction, and extracting the elastic stiffness constants from the secular equations for these velocities. Results from the two methods are in good agreement and are for Rh3Nb, C11 = 368 ± 3, C12 = 186 ± 5, and C44 = 161 ± 3 in GPa; and for Rh3Zr, C11 = 329 ± 4, C12 = 185 ± 6, and C44 = 145 ± 4 in GPa.
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.
The effects of cadmium on the structure and elastic properties of carotid arteries from rats.
Terpin, T; Roach, M R
1980-01-01
Cadmium chloride (0.6 mg/kg) was injected intraperitoneally into seventy-five rats to determine if this material altered the static elastic properties of the carotid arteries. Control rats were either injected with saline or left untreated. The elastic properties were determined from cylindrical segments of artery which were distended with water of known volume. The pressure and length were measured. Experiments were done either at constant in vivo length or with the artery untethered so the length altered with pressure. Comparison of the methods allowed analysis of the role of elastin and collagen oriented circumferentially, longitudinally, of helically. The major changes occurred in the longitudinal direction. The initial part of the curve has previously been shown to be due to elastin, and the final part to collagen. Collagen increased more than elastin and muscle (as determined from point counting of trichrome-stained sections), but appeared to have the same elastic modulus as normal collagen. The major change was in the "cross-linking" between collagen fibres. This increased with time on the CdCl2 in a manner comparable to that seen with age in humans. Many of the changes were biphasic, and changes that occurred between one and four weeks on the CdCl2 were often recovered with continued treatment. The reason for this is obscure. PMID:7441096
Materials properties data base computerization
NASA Technical Reports Server (NTRS)
Baur, R. G.; Donthnier, M. L.; Moran, M. C.; Mortman, I.; Pinter, R. S.
1984-01-01
Material property data plays a key role in the design of jet engine components. Consistency, accuracy and efficient use of material property data is of prime importance to the engineering community. The system conception, development, implementation, and future plans for computer software that captures the Material Properties Handbook into a scientific data base are described. The engineering community is given access to raw data and property curves, display of multiple curves for material evaluation and selection, direct access by design analysis computer programs, display of the material specification, and a historical repository for the material evolution. The impact of this activity includes significant productivity gains and cost reductions; all users have access to the same information nd provides consistent, rapid response to the needs of the engineering community. Future plans include incorporating the materials properties data base into a network environment to access information from other data bases and download information to engineering work stations.
Laser-Ultrasonic Measurement of Elastic Properties of Anodized Aluminum Coatings
NASA Astrophysics Data System (ADS)
Singer, F.
Anodized aluminum oxide plays a great role in many industrial applications, e.g. in order to achieve greater wear resistance. Since the hardness of the anodized films strongly depends on its processing parameters, it is important to characterize the influence of the processing parameters on the film properties. In this work the elastic material parameters of anodized aluminum were investigated using a laser-based ultrasound system. The anodized films were characterized analyzing the dispersion of Rayleigh waves with a one-layer model. It was shown that anodizing time and temperature strongly influence Rayleigh wave propagation.
Nonuniform elastic properties of macromolecules and effect of prestrain on their continuum nature
NASA Astrophysics Data System (ADS)
Aggarwal, Ankush; May, Eric R.; Brooks, Charles L.; Klug, William S.
2016-01-01
Many experimental and theoretical methods have been developed to calculate the coarse-grained continuum elastic properties of macromolecules. However, all of those methods assume uniform elastic properties. Following the continuum mechanics framework, we present a systematic way of calculating the nonuniform effective elastic properties from atomic thermal fluctuations obtained from molecular dynamics simulation at any coarse-grained scale using a potential of the mean-force approach. We present the results for a mutant of Sesbania mosaic virus capsid, where we calculate the elastic moduli at different scales and observe an apparent problem with the chosen reference configuration in some cases. We present a possible explanation using an elastic network model, where inducing random prestrain results in a similar behavior. This phenomenon provides a novel insight into the continuum nature of macromolecules and defines the limits on details that the elasticity theory can capture. Further investigation into prestrains could elucidate important aspects of conformational dynamics of macromolecules.
Nonuniform elastic properties of macromolecules and effect of prestrain on their continuum nature.
Aggarwal, Ankush; May, Eric R; Brooks, Charles L; Klug, William S
2016-01-01
Many experimental and theoretical methods have been developed to calculate the coarse-grained continuum elastic properties of macromolecules. However, all of those methods assume uniform elastic properties. Following the continuum mechanics framework, we present a systematic way of calculating the nonuniform effective elastic properties from atomic thermal fluctuations obtained from molecular dynamics simulation at any coarse-grained scale using a potential of the mean-force approach. We present the results for a mutant of Sesbania mosaic virus capsid, where we calculate the elastic moduli at different scales and observe an apparent problem with the chosen reference configuration in some cases. We present a possible explanation using an elastic network model, where inducing random prestrain results in a similar behavior. This phenomenon provides a novel insight into the continuum nature of macromolecules and defines the limits on details that the elasticity theory can capture. Further investigation into prestrains could elucidate important aspects of conformational dynamics of macromolecules. PMID:26871111
NASA Astrophysics Data System (ADS)
Li, Guangyan; Adebisi, Resheed; Gladden, Josh
2009-03-01
Thermoelectric (TE) materials can be used to convert heat including waste heat to electrical power. They are one component to energy savings and independence. Silicon germanium (SiGe) and Zintl phase compounds are excellent candidates for high temperature applications. The mechanical properties of these materials need to be known before their actual applications in high temperature (1000C) environments. The temperature dependent elastic moduli of five different SiGe alloys were successfully measured using a high temperature resonant ultrasound spectroscopy (RUS) technique. A linear trend is generally observed up to 600C, a downward curvature especially in two n-type samples is noticeable at higher temperatures. Hysteresis is only observed in one of the n-type SiGe samples. Phase transitions, indicated by shifts in the natural frequencies of a Zintl sample, were observed near 792, 892, 931C. The nature of these transitions will be discussed.
Optoelectronic Properties, Elastic Moduli and Thermoelectricity of SrAlGa: An Ab Initio Study
NASA Astrophysics Data System (ADS)
Roshan, Ali; Murtaza, G.; Takagiwa, Y.; Khenata, R.; Haleem, Uddin; Ullah, H.; A. Khan, S.
2014-04-01
Half-Heusler compounds are an impressive class of materials with a huge potential for different applications such as in future energy, especially in the fields of thermoelectrics and solar cells. We present ab initio total energy calculations within the modified Becke—Johnson generalized gradient approximation (mBJ-GGA) to obtain the physical properties of SrAlGa compounds. The structural, elastic, acoustic, electronic, chemical bonding, optical, and thermoelectric properties are calculated and compared with the available calculation data. The SrAlGa is found to be a small-band-gap (0.125-0.175 eV) material, suitable for thermoelectric applications with a relatively high Seebeck coefficient. Also, SrAlGa has the potential in the optoelectronic applications due to high optical conductivity and reflectivity in the infrared and visible region of electromagnetic spectra.
Davis, Frances M; Luo, Yuanming; Avril, Stéphane; Duprey, Ambroise; Lu, Jia
2015-10-01
In this manuscript, we present a combined experimental and computational technique that can identify the heterogeneous elastic properties of planar soft tissues. By combining inverse membrane analysis, digital image correlation, and bulge inflation tests, we are able to identify a tissue's mechanical properties locally. To show how the proposed method could be implemented, we quantified the heterogeneous material properties of a human ascending thoracic aortic aneurysm (ATAA). The ATAA was inflated at a constant rate using a bulge inflation device until it ruptured. Every 3 kPa images were taken using a stereo digital image correlation system. From the images, the three-dimensional displacement of the sample surface was determined. A deforming NURBS mesh was derived from the displacement data, and the local strains were computed. The wall stresses at each pressure increment were determined using inverse membrane analysis. The local material properties of the ATAA were then identified using the pointwise stress and strain data. To show that it is necessary to consider the heterogeneous distribution of the mechanical properties in the ATAA, three different forward finite element simulations using pointwise, elementwise, and homogeneous material properties were compared. The forward finite element predictions revealed that heterogeneous nature of the ATAA must be accounted for to accurately reproduce the stress-strain response. PMID:25576390
Effect of doping and elastic properties in (Mn,Fe ) 2(Si ,P )
NASA Astrophysics Data System (ADS)
Roy, P.; Torun, E.; de Groot, R. A.
2016-03-01
Mixed magnetism (the coexistence of strong and weak magnetism in one material) is regarded as the origin of the giant magnetocaloric effect (GMCE). A good example is (Mn,Fe ) 2(Si ,P ), which is established as one of the best magnetocaloric materials available. Tuning the material properties are essential for optimizing its performance, and a straightforward way to do that is by doping. In this article, an ab initio electronic structure method was used to calculate the structure and magnetic properties of 3 d -transition-metal-doped (Mn,Fe ) 2(Si ,P ) materials for magnetocaloric applications (transition metals are Cr, Co, Mn, Ni, Cu). For a steady performance, the material should be mechanically stable. A detailed analysis of the elastic constants shows that the mechanical stability of the (Mn,Fe ) 2(Si ,P ) system increases significantly by doping with boron without affecting the magnetic properties. Insights of the influence of doping enable future studies to understand and predict better magnetocaloric materials.
NASA Astrophysics Data System (ADS)
Wang, Jun-Fei; Fu, Xiao-Nan; Zhang, Xiao-Dong; Wang, Jun-Tao; Li, Xiao-Dong; Jiang, Zhen-Yi
2016-08-01
The structural, elastic, electronic, and thermodynamic properties of thermoelectric material MgAgSb in γ,β,α phases are studied with first-principles calculations based on density functional theory. The optimized lattice constants accord well with the experimental data. According to the calculated total energy of the three phases, the phase transition order is determined from α to γ phase with cooling, which is in agreement with the experimental result. The physical properties such as elastic constants, bulk modulus, shear modulus, Young’s modulus, Poisson’s ratio, and anisotropy factor are also discussed and analyzed, which indicates that the three structures are mechanically stable and each has a ductile feature. The Debye temperature is deduced from the elastic properties. The total density of states (TDOS) and partial density of states (PDOS) of the three phases are investigated. The TDOS results show that the γ phase is most stable with a pseudogap near the Fermi level, and the PDOS analysis indicates that the conduction band of the three phases is composed mostly of Mg-3s, Ag-4d, and Sb-5p. In addition, the changes of the free energy, entropy, specific heat, thermal expansion of γ-MgAgSb with temperature are obtained successfully. The obtained results above are important parameters for further experimental and theoretical tuning of doped MgAgSb as a thermoelectric material at high temperature. Project supported by the National Natural Science Foundation of China (Grant No. 11504088), the Fund from Henan University of Technology, China (Grant Nos. 2014YWQN08 and 2013JCYJ12), the Natural Science Fund from the Henan Provincial Education Department, China (Grant No. 16A140027), the Natural Science Foundation of Shaanxi Province of China (Grant Nos. 2013JQ1018 and 15JK1759), and the Science Foundation of Northwest University of China (Grant No. 14NW23).
Identification of elastic basin properties by large-scale inverse earthquake wave propagation
NASA Astrophysics Data System (ADS)
Epanomeritakis, Ioannis K.
The importance of the study of earthquake response, from a social and economical standpoint, is a major motivation for the current study. The severe uncertainties involved in the analysis of elastic wave propagation in the interior of the earth increase the difficulty in estimating earthquake impact in seismically active areas. The need for recovery of information about the geological and mechanical properties of underlying soils motivates the attempt to apply inverse analysis on earthquake wave propagation problems. Inversion for elastic properties of soils is formulated as an constrained optimization problem. A series of trial mechanical soil models is tested against a limited-size set of dynamic response measurements, given partial knowledge of the target model and complete information on source characteristics, both temporal and geometric. This inverse analysis gives rise to a powerful method for recovery of a material model that produces the given response. The goal of the current study is the development of a robust and efficient computational inversion methodology for material model identification. Solution methods for gradient-based local optimization combine with robustification and globalization techniques to build an effective inversion framework. A Newton-based approach deals with the complications of the highly nonlinear systems generated in the inversion solution process. Moreover, a key addition to the inversion methodology is the application of regularization techniques for obtaining admissible soil models. Most importantly, the development and use of a multiscale strategy offers globalizing and robustifying advantages to the inversion process. In this study, a collection of results of inversion for different three-dimensional Lame moduli models is presented. The results demonstrate the effectiveness of the inversion methodology proposed and provide evidence for its capabilities. They also show the path for further study of elastic property
NASA Astrophysics Data System (ADS)
Silverberg, Jesse; Bonassar, Lawrence; Cohen, Itai
2013-03-01
Contemporary developments in therapeutic tissue engineering have been enabled by basic research efforts in the field of biomechanics. Further integration of technology in medicine requires a deeper understanding of the mechanical properties of soft biological materials and the structural origins of their response under extreme stresses and strains. Drawing on the science generated by the ``Extreme Mechanics'' community, we present experimental results on the mechanical properties of articular cartilage, a hierarchically structured soft biomaterial found in the joints of mammalian long bones. Measurements of the spatially localized structure and mechanical properties will be compared with theoretical descriptions based on networks of deformed rods, poro-visco-elasticity, and standard continuum models. Discrepancies between experiment and theory will be highlighted, and suggestions for how models can be improved will be given.
Ultrasonic measurement of the elastic properties of ultra-high performance concrete (UHPC)
NASA Astrophysics Data System (ADS)
Washer, Glenn; Fuchs, Paul; Rezai, Ali; Ghasemi, Hamid
2005-05-01
This paper discusses research to develop ultrasonic methods for materials characterization of an innovative new material known as Reactive Powder Concrete (RPC). Also known as Ultra-high performance concrete (UHPC), this relatively new material has been proposed for the construction of civil structures. UHPC mix designs typically include no aggregates larger than sand, and include steel fibers 0.2 mm in diameter and 12 mm in length. These steel fibers increase the strength and toughness of the UHPC significantly relative to more traditional concretes. Compressive strengths of 200 to 800 MPa have been achieved with UHPC, compared with maximum compressive strength of 50 to 100 MPa for more traditional concrete materials. Young"s modulus of 50 to 60 GPa are common for UHPC. However, the curing methods employed have a significant influence on the strength and modulus of UHPC. This paper reports on the development of ultrasonic methods for monitoring the elastic properties of UHPC under a series of curing scenarios. Ultrasonic velocity measurements are used to estimate the bulk elastic modulus of UHPC and results are compared with traditional, destructive methods. Measurements of shear moduli and Poisson's ratio based on ultrasonic velocity are also reported. The potential for the development of quality control techniques for the future implementation of UHPC is discussed.
Microstructures and elastic properties of sheared calcite flowstone
NASA Astrophysics Data System (ADS)
Mitrovic, Ivanka; Grasemann, Bernhard; Plan, Lukas; Tesei, Telemaco; Baron, Ivo
2016-04-01
Flowstone is a monomineralic rock precipitated along cave walls and floors, composed of columnar centimeter-scale calcite crystals with strong growth orientation perpendicular to the growth surface. Broken and scratched flowstone can serve as evidence for active faulting and has been found in several alpine caves in Austria. In order to understand the fault mechanics, and associated potential earthquake hazard, experimentally deformed flowstone is studied using microstructural analysis and EBSD-measured physical properties of calcite crystals. For that purpose, we have performed sliding experiments using a rock deformation biaxial apparatus on rectangular blocks of flowstone that were sheared perpendicular to the calcite growth direction. The experiments were performed under room conditions, with sub-seismic sliding velocity (0.001-0.01 mm/s) and constant effective normal stress (3-10 MPa). The deformed samples show diverse brittle features, including high fracture density, the development of calcite-rich fault gouge with Riedel shears within a foliated cataclasite, and drastic grain size reduction down to nm-scale grains. The dominant plastic microstructure is mechanical twinning. Due to the strong growth orientation of calcite in flowstone, crystals can be bent due to shearing. We examine the bending by applying orientation distribution, Schmid factor and elasticity tensor calculations using MTEX Toolbox from EBSD data. In this unique case the flowstone deformation experiments bridge the gap between single crystal and rock powder experiments. This study is supported by the Austrian Science Foundation: SPELEOTECT project (P25884-N29).
Transport properties of elastically coupled fractional Brownian motors
NASA Astrophysics Data System (ADS)
Lv, Wangyong; Wang, Huiqi; Lin, Lifeng; Wang, Fei; Zhong, Suchuan
2015-11-01
Under the background of anomalous diffusion, which is characterized by the sub-linear or super-linear mean-square displacement in time, we proposed the coupled fractional Brownian motors, in which the asymmetrical periodic potential as ratchet is coupled mutually with elastic springs, and the driving source is the external harmonic force and internal thermal fluctuations. The transport mechanism of coupled particles in the overdamped limit is investigated as the function of the temperature of baths, coupling constant and natural length of the spring, the amplitude and frequency of driving force, and the asymmetry of ratchet potential by numerical stimulations. The results indicate that the damping force involving the information of historical velocity leads to the nonlocal memory property and blocks the traditional dissipative motion behaviors, and it even plays a cooperative role of driving force in drift motion of the coupled particles. Thus, we observe various non-monotonic resonance-like behaviors of collective directed transport in the mediums with different diffusion exponents.
Elastic, micro- and macroplastic properties of polycrystalline beryllium
NASA Astrophysics Data System (ADS)
Kardashev, B. K.; Kupriyanov, I. B.
2011-12-01
The Young's modulus and the internal friction of beryllium polycrystals (size grain from 6 to 60 μm) prepared by the powder metallurgy method have been studied as functions of the amplitude and temperature in the range from 100 to 873 K. The measurements have been performed using the composite piezoelectric vibrator method for longitudinal vibrations at frequencies about 100 kHz. Based on the acoustic measurements, the data have been obtained on the elastic and inelastic (microplastic) properties as functions of vibration stress amplitudes within the limits from 0.2 to 30-60 MPa. The microplastic deformation diagram is shown to become nonlinear at the amplitudes higher than 5 MPa. The beryllium mechanical characteristics (the yield strength σ 0.2, the ultimate strength σ u , and the conventional microscopic yield strength σ y ) obtained with various grain sizes are compared. At room temperature, all the parameters satisfactorily obey the Hall-Petch relationship, although there is no complete similarity. The temperature dependences are quite different, namely: σ 0.2( T) and σ u ( T) decrease monotonically during heating from room temperature to higher temperatures; however, σ y ( T) behaves unusually, and it has a minimum near 400 K. The different levels of stresses and the absence of similarity indicate that the scattering of the ultrasound energy and the formation of a level of the macroscopic flow stresses in beryllium occur on dislocation motion obstacles of different origins.
Recent developments in testing techniques for elastic mechanical properties of 1-D nanomaterials.
Wang, Weidong; Li, Shuai; Zhang, Hongti; Lu, Yang
2015-01-01
One-dimensional (1-D) nanomaterials exhibit great potentials in their applications to functional materials, nano-devices and systems owing to their excellent properties. In the past decade, considerable studies have been done, with new patents being developed, on these 1-D building blocks for for their mechanical properties, especially elastic properties, which provide a solid foundation for the design of nanoelectromechanical systems (NEMS) and predictions of reliability and longevity for their devices. This paper reviews some of the recent investigations on techniques as well as patents available for the quantitative characterization of the elastic behaviors of various 1-D nanomaterials, with particular focus on on-chip testing system. The review begins with an overview of major testing methods for 1-D nanostructures' elastic properties, including nanoindentation testing, AFM (atomic force microscopy) testing, in situ SEM (scanning electron microscopy) testing, in situ TEM (transmission electron microscopy) testing and the testing system on the basis of MEMS (micro-electro-mechanical systems) technology, followed by advantages and challenges of each testing approach. This review also focuses on the MEMS-based testing apparatus, which can be actuated and measured inside SEM and TEM with ease, allowing users to highly magnify the continuous images of the specimen while measuring load electronically and independently. The combination of on-chip technologies and the in situ electron microscopy is expected to be a potential testing technique for nanomechanics. Finally, details are presented on the key challenges and possible solutions in the implementation of the testing techniques referred above. PMID:25986228
NASA Technical Reports Server (NTRS)
Prosser, William H.
1987-01-01
The theoretical treatment of linear and nonlinear elasticity in a unidirectionally fiber reinforced composite as well as measurements for a unidirectional graphite/epoxy composite (T300/5208) are presented. Linear elastic properties were measured by both ultrasonic and strain gage measurements. The nonlinear properties were determined by measuring changes in ultrasonic natural phase velocity with a pulsed phase locked loop interferometer as a function of stress and temperature. These measurements provide the basis for further investigations into the relationship between nonlinear elastic properties and other important properties such as strength and fiber-matrix interfacial stength in graphite/epoxy composites.
Pressure effect on structural, elastic, and thermodynamic properties of tetragonal B{sub 4}C{sub 4}
Zheng, Baobing; Zhang, Meiguang; Luo, Hong-Gang
2015-03-15
The compressibility, elastic anisotropy, and thermodynamic properties of the recently proposed tetragonal B{sub 4}C{sub 4} (t-B{sub 4}C{sub 4}) are investigated under high temperature and high pressure by using of first-principles calculations method. The elastic constants, bulk modulus, shear modulus, Young’s modulus, Vickers hardness, Pugh’s modulus ratio, and Poisson’s ratio for t-B{sub 4}C{sub 4} under various pressures are systematically explored, the obtained results indicate that t-B{sub 4}C{sub 4} is a stiffer material. The elastic anisotropies of t-B{sub 4}C{sub 4} are discussed in detail under pressure from 0 GPa to 100 GPa. The thermodynamic properties of t-B{sub 4}C{sub 4}, such as Debye temperature, heat capacity, and thermal expansion coefficient are investigated by the quasi-harmonic Debye model.
Khatam, Hamed; Ravi-Chandar, K.
2013-01-01
A nonlinear optimization procedure is established to determine the elastic modulus of slender, soft materials using beams with unknown initial curvature in the presence of large rotations. Specifically, the deflection of clamped-free beams under self-weight – measured at different orientations with respect to gravity – is used to determine the modulus of elasticity and the intrinsic curvature in the unloaded state. The approach is validated with experiments on a number of different materials – steel, polyetherimide, rubber and pig skin. Since the loading is limited to self-weight, the strain levels attained in these tests are small enough to assume a linear elastic material behavior. This nondestructive methodology is also applicable to engineered tissues and extremely delicate materials in order to obtain a quick estimate of the material’s elastic modulus. PMID:24159244
Rohlmann, A; Zilch, H; Bergmann, G; Kölbel, R
1980-01-01
The time independent material behavior of cylindrical specimens obtained from the cancelous bone of 20 cadaveric human femora were determined. In this part of the publication, the nominal values for compressive strength, limits of elasticity (yield point), strain, elastic modulus and apparent density are being reported for the cancellous bone of the femoral head and condyle. The correlations between the various parameters are analysed. A positive linear correlation between the four parameters compressive stength, limit of elasticity, modulus of elasticity and apparent density could not be excluded. The material properties vary considerably both within one single bone and between individuals. Compressive strength, modulus of elasticity and apparent density found for cancellous bone of the femoral head are greater than those found in the condyles. Within the condyles, compressive strength, elastic modulus and apparent density increase from the proximal parts to the parts closer to the joint. The medial femoral condyle showed higher compressive strength than the lateral one. Relating each of the three other parameters to the apparent density of the individual specimen did not result in equalizing the data for the material properties. This indicates that the mechanical properties of cancellous bone are strongly related to the direction of loading. PMID:7458606
Influence of anisotropic elasticity on the mechanical properties of fivefold twinned nanowires
NASA Astrophysics Data System (ADS)
Niekiel, Florian; Spiecker, Erdmann; Bitzek, Erik
2015-11-01
Previous atomistic simulations and experiments have shown an increased Young's modulus and yield strength of fivefold twinned (FT) face-centered cubic metal nanowires (NWs) when compared to single crystalline (SC) NWs of the same orientation. Here we report the results of atomistic simulations of SC and FT Ag, Al, Au, Cu and Ni NWs with diameters between 2 and 50 nm under tension and compression. The simulations show that the differences in Young's modulus between SC and FT NWs are correlated with the elastic anisotropy of the metal, with Al showing a decreased Young's modulus. We develop a simple analytical model based on disclination theory and constraint anisotropic elasticity to explain the trend in the difference of Young's modulus between SC and FT NWs. Taking into account the role of surface stresses and the elastic properties of twin boundaries allows to account for the observed size effect in Young's modulus. The model furthermore explains the different relative yield strengths in tension and compression as well as the material and loading dependent failure mechanisms in FTNWs.
From viscous fingering to bulk elastic fingering in soft materials
NASA Astrophysics Data System (ADS)
Saintyves, Baudouin; Biggins, John; Wei, Zhiyan; Mora, Serge; Dauchot, Olivier; Mahadevan, L.; Bouchaud, Elisabeth
2014-03-01
Systematic experiments have been performed in purely elastic polyacrylamide gels in Hele-Shaw cells. We have shown that a bulk fingering instability arises in the highly deformable confined elastomers. It shares some similarities with the famous Saffman-Taylor instability, but a systematic study shows that surface tension is not relevant. This instability is sub-critical, with a clear hysteretic behavior. Our experimental observations have been compared very favorably to theoretical and finite element simulations results. In particular, the instability wavelength and the critical front advance have been shown to be proportional to the distance between the two glass plates constituting the cell. We have also shown that in Maxwell viscoelastic fluids, one crosses over continuously from a viscous to an elastic fingering instability.
Palpationlike soft-material elastic modulus measurement using piezoelectric cantilevers
NASA Astrophysics Data System (ADS)
Szewczyk, Steven T.; Shih, Wan Y.; Shih, Wei-Heng
2006-04-01
We have developed an all-electrical piezoelectric cantilever sensor that can self-excite and self-detect for tissue elastic modulus measurement. An all-electrical piezoelectric cantilever is consisted of a sandwich of piezoelectric layer, e.g., lead zirconate titanate (PZT), a nonpiezoelectric layer, e.g., stainless steel, and a second piezoelectric layer. The top piezoelectric layer serves as the driving layer (self-exciting) and the second piezoelectric layer as the sensing layer (self-sensing). The driving and sensing piezoelectric layers may be of different lengths. Applying a dc voltage across the driving PZT layer causes the piezoelectric cantilever to bend. The resultant bending stress in the sensing PZT layer generates a piezoelectric voltage across the sensing PZT layer that rises rapidly to a maximum before it decays with time. The maximum induced voltage was used to measure the axial displacement of the piezoelectric cantilever. With its force generation and displacement sensing capability, we show that an all-electrical piezoelectric cantilever can measure the elastic modulus of tissues both under the regular compression geometry and the flat-punch indentation geometry. In addition, the sensor can map the local elastic modulus variations of tissues much like palpation.
Elastic properties of model 3-D porous ceramics and foams
NASA Astrophysics Data System (ADS)
Roberts, Anthony; Garboczi, Edward
2000-03-01
The novel properties of many new porous materials are related to their interesting internal microstructure. Apart from simple cases, there exist no theoretical means of predicting the bulk properties of these materials. This limits our ability to guide microstructure optimization for a particular purpose. We use a large scale finite element method to demonstrate the complex relationship between microstructure and the effective properties of realistic three-dimensional model porous ceramics and foams. We find that pore-shape and interconnectivity strongly influence the properties of sintered ceramics. For porous foams we have studied the role of coordination number, random disorder, and strut shape on the Young's modulus and Poisson's ratio. We find that that Voronoi tesselations, commonly used to model solid foams, show unphysical behavior, in particular they are incompressible (rubber-like) at low densities. Deletion of just 10% of the bonds in the model reduces the bulk modulus by 75%, more in line with experimental evidence. The FEM results are generally in good agreement with experimental data for ceramics and foams, and can be used as both a predictive and interpretative tool by experimentalists.
Tan, Yang; Shyam, Amit; Choi, Wanhuk Brian; Lara-Curzio, Edgar; Sampath, Sanjay
2010-01-01
The determination of elastic properties of plasma-sprayed ceramic and metallic coatings is difficult due to their complex microstructure, which involves a myriad array of pores, interfaces and other defects. Furthermore, the splat-based build-up of the coating results in transverse anisotropy in the elastic properties. In this paper, we report on the anisotropic elastic properties of these coatings determined by resonant ultrasound spectroscopy (RUS). This approach along with the analysis presented enables, for the first time, the determination of elastic properties as a function of direction and temperature for these complex systems with concomitant implications for design. The coating systems investigated included plasma-sprayed yttria-stabilized zirconia (YSZ) and nickel. An additional nickel coating deposited by high-velocity oxygen-fuel process was investigated and its elastic properties were compared to those of plasma-sprayed nickel. Average Young s moduli of the coatings were independently measured by using the instrumented indentation method. The elastic properties determined from the RUS and indentation methodologies allowed description of the microstructure elastic property relationships in the coatings.
Fast tool for evaluation of iliac crest tissue elastic properties using the reduced-basis methods.
Lee, Taeyong; Garlapati, Revanth Reddy; Lam, Kathy; Lee, Peter Vee Sin; Chung, Yoon-Sok; Choi, Jae Bong; Vincent, Tan Beng Chye; Das De, Shamal
2010-12-01
Computationally expensive finite element (FE) methods are generally used for indirect evaluation of tissue mechanical properties of trabecular specimens, which is vital for fracture risk prediction in the elderly. This work presents the application of reduced-basis (RB) methods for rapid evaluation of simulation results. Three cylindrical transiliac crest specimens (diameter: 7.5 mm, length: 10-12 mm) were obtained from healthy subjects (20 year-old, 22 year-old, and 24 year-old females) and scanned using microcomputed tomography imaging. Cubic samples of dimensions 5×5×5 mm(3) were extracted from the core of the cylindrical specimens for FE analysis. Subsequently, a FE solution library (test space) was constructed for each of the specimens by varying the material property parameters: tissue elastic modulus and Poisson's ratio, to develop RB algorithms. The computational speed gain obtained by the RB methods and their accuracy relative to the FE analysis were evaluated. Speed gains greater than 4000 times, were obtained for all three specimens for a loss in accuracy of less than 1% in the maxima of von-Mises stress with respect to the FE-based value. The computational time decreased from more than 6 h to less than 18 s. RB algorithms can be successfully utilized for real-time reliable evaluation of trabecular bone elastic properties. PMID:21142323
NASA Technical Reports Server (NTRS)
Kim, H. Alicia; Hardie, Robert; Yamakov, Vesselin; Park, Cheol
2015-01-01
This paper is the second part of a two-part series where the first part presents a molecular dynamics model of a single Boron Nitride Nanotube (BNNT) and this paper scales up to multiple BNNTs in a polymer matrix. This paper presents finite element (FE) models to investigate the effective elastic and piezoelectric properties of (BNNT) nanocomposites. The nanocomposites studied in this paper are thin films of polymer matrix with aligned co-planar BNNTs. The FE modelling approach provides a computationally efficient way to gain an understanding of the material properties. We examine several FE models to identify the most suitable models and investigate the effective properties with respect to the BNNT volume fraction and the number of nanotube walls. The FE models are constructed to represent aligned and randomly distributed BNNTs in a matrix of resin using 2D and 3D hollow and 3D filled cylinders. The homogenisation approach is employed to determine the overall elastic and piezoelectric constants for a range of volume fractions. These models are compared with an analytical model based on Mori-Tanaka formulation suitable for finite length cylindrical inclusions. The model applies to primarily single-wall BNNTs but is also extended to multi-wall BNNTs, for which preliminary results will be presented. Results from the Part 1 of this series can help to establish a constitutive relationship for input into the finite element model to enable the modeling of multiple BNNTs in a polymer matrix.
NASA Astrophysics Data System (ADS)
Stan, Gheorghe; Cook, Robert
2010-03-01
The synthesis and processing of materials into nanostructures opens new avenues for advancement and diversification of current electronic, optoelectronic, and sensor applications. Among these structures, Si NWs are distinctly remarkable as they bring the previous decades knowledge of silicon technology into nanoscale applications. From this perspective, the characterization and understanding of the mechanical properties of nonplanar Si-SiO2 interfaces are of significant utility in developing Si nanostructures for Si-based integrated circuits. To investigate the elastic properties of as-grown and oxidized Si NWs we have extended and specifically tailored the applicability of contact-resonance atomic force microscopy (CR- AFM). From such CR-AFM measurements, the effect of the compressive stress at the Si-SiO2 interface was revealed in a diameter dependence of the elastic modulus of oxidized Si NWs. A modified core-shell model that includes the interface stress developed during oxidation captures the observed dependence. The values of strain and stress as well as the width of the stressed transition region at the Si-SiO2 interface agree with those reported from simulations and other experiments. This novel approach advances CR-AFM applicability in investigating structure-mechanical property relationships at the nanoscale.
NASA Astrophysics Data System (ADS)
Chen, Shuai; Duan, Yong-Hua; Huang, Bo; Hu, Wen-Cheng
2015-11-01
The structural properties, phase stabilities, anisotropic elastic properties and electronic structures of Cu-Ti intermetallics have been systematically investigated using first principles based on the density functional theory. The calculated equilibrium structural parameters agree well with available experimental data. The ground-state convex hull of formation enthalpies as a function of Cu content is slightly symmetrical at CuTi with a minimal formation enthalpy (-13.861 kJ/mol of atoms), which indicates that CuTi is the most stable phase. The mechanical properties, including elastic constants, polycrystalline moduli and anisotropic indexes, were evaluated. G/B is more pertinent to hardness than to the shear modulus G due to the high power indexes of 1.137 for G/B. The mechanical anisotropy was also characterized by describing the three-dimensional (3D) surface constructions. The order of elastic anisotropy is Cu4Ti3 > Cu3Ti2 > α-Cu4Ti > Cu2Ti > CuTi > β-Cu4Ti > CuTi2. Finally, the electronic structures were discussed and Cu2Ti is a semiconductor.
Using structural modularity in cocrystals to engineer properties: elasticity.
Saha, Subhankar; Desiraju, Gautam R
2016-06-01
Cocrystal formation of heterocyclic bases with halogenated aromatic acids increases the tendency for stacking and with this, an increase in structural isotropy occurs that leads to crystal elasticity. PMID:27228952
Physical Properties of Synthetic Resin Materials
NASA Technical Reports Server (NTRS)
Fishbein, Meyer
1939-01-01
A study was made to determine the physical properties of synthetic resins having paper, canvas, and linen reinforcements, and of laminated wood impregnated with a resin varnish. The results show that commercial resins have moduli of elasticity that are too low for structural considerations. Nevertheless, there do exist plastics that have favorable mechanical properties and, with further development, it should be possible to produce resin products that compare favorably with the light-metal alloys. The results obtained from tests on Compound 1840, resin-impregnated wood, show that this material can stand on its own merit by virtue of a compressive strength four times that of the natural wood. This increase in compressive strength was accomplished with an increase of density to a value slightly below three times the normal value and corrected one of the most serious defects of the natural product.
Seung-Kyu Park; Sung-Hoon Baik; Hyung-Ki Cha; Stephen J. Reese; David H. Hurley
2010-08-01
Resonant ultrasound spectroscopy (RUS) is a useful technique for measuring the elastic properties of materials. In this study, two experimental approaches for performing RUS are experimentally analyzed and compared: 1) contact transduction using piezoelectric transducers (PZT) and 2) laser transduction using pulse laser excitation and laser interferometric detection. A single Zircaloy sample cut from a nuclear pressure tube was used for this study. By virtue of the non-contact nature, the quality factor, Q, for laser RUS is shown to be higher than the contact RUS. In addition, the probe beam for laser-RUS can be scanned to form a 2D image of each vibrational mode, which in turn enables unique mode identification. These defining characteristics of laser-RUS enable straightforward discrimination of closely spaced resonant modes and provide key advantages for improving the resolution of resonant ultrasound spectroscopy.
Jiang, Jian-jun; Li, He-ping; Dai, Li-dong; Hu, Hai-ying; Wang, Yan; Zhao, Chao-shuai
2015-09-01
In-situ experimental results on the elastic wave velocity of Earth materials at high pressure and high temperature in combination with data from seismic observation can help to inverse the chemical composition, state and migration of materials in Earth's interior, providing an important approach to explore information of deep earth. Applying the Brillouin scattering into the Diamond Anvil Cell (DAC) to obtain the in situ elastic wave velocities of minerals, is the important approach to investigate elastic properties of Earth's Interior. With the development of DAC technology, on the one hand, the high temperature and high pressure experimental environment to simulate different layers of the earth can be achieved; on the other hand, the optical properties of DAC made many kinds of optical analysis and test methods have been widely applied in this research field. In order to gain the elastic wave velocity under high temperature and high pressure, the accurate experimental pressure and heating temperature of the sample in the cavity should be measured and calibrated first, then the scattering signal needs to dealt with, using the Brillouin frequency shift to calculate the velocity in the sample. Combined with the lattice constants obtained from X ray technique, by a solid elastic theory, all the elastic parameters of minerals can be solved. In this paper, firstly, application of methods based on optical spectrum such as Brillouin and Raman scattering in elasticity study on materials in Earth's interior, and the basic principle and research progress of them in the velocity measurement, pressure and temperature calibration are described in detail. Secondly, principle and scope of application of two common methods of spectral pressure calibration (fluorescence and Raman spectral pressure standard) are analyzed, in addition with introduce of the application of two conventional means of temperature calibration (blackbody radiation and Raman temperature scale) in
Dynamic properties of ceramic materials
Grady, D.E.
1995-02-01
The present study offers new data and analysis on the transient shock strength and equation-of-state properties of ceramics. Various dynamic data on nine high strength ceramics are provided with wave profile measurements, through velocity interferometry techniques, the principal observable. Compressive failure in the shock wave front, with emphasis on brittle versus ductile mechanisms of deformation, is examined in some detail. Extensive spall strength data are provided and related to the theoretical spall strength, and to energy-based theories of the spall process. Failure waves, as a mechanism of deformation in the transient shock process, are examined. Strength and equation-of-state analysis of shock data on silicon carbide, boron carbide, tungsten carbide, silicon dioxide and aluminum nitride is presented with particular emphasis on phase transition properties for the latter two. Wave profile measurements on selected ceramics are investigated for evidence of rate sensitive elastic precursor decay in the shock front failure process.