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
2016-01-01
[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 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 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
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
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; 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 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 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.
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
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.
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.
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.
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
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.
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
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
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.
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
2015-01-01
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
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
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.
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.
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
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.
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.
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.
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.
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 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.
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.
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.
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
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 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.
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.
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.
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.
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
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.
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.
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 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.}
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.
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.
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.
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.
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
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
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.
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.
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.
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.
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
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.
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.
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.
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
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.
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.
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.
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
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.
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.
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)
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.
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.
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.
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.
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.
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
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.
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.
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.
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.
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.
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.
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 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.
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.
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.
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.
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
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.
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.
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.
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.
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
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.
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 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 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)
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.
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.
A novel method to determine the elastic modulus of extremely soft materials.
Stirling, Tamás; Zrínyi, Miklós
2015-06-01
Determination of the elastic moduli of extremely soft materials that may deform under their own weight is a rather difficult experimental task. A new method has been elaborated by means of which the elastic modulus of such materials can be determined. This method is generally applicable to all soft materials with purely neo-Hookean elastic deformation behaviour with elastic moduli lower than 1 kPa. Our novel method utilises the self-deformation of pendent gel cylinders under gravity. When suspended, the material at the very top bears the weight of the entire gel cylinder, but that at the bottom carries no load at all. Due to the non-uniform stress distribution along the gel sample both the stress and the resulting strain show position dependence. The cross-sectional area of the material is lowest at the top of the sample and gradually increases towards its bottom. The equilibrium geometry of the pendant gel is used to evaluate the elastic modulus. Experimental data obtained by the proposed new method were compared to the results obtained from underwater measurements. The parameters affecting the measurement uncertainty were studied by a Pareto analysis of a series of adaptive Monte Carlo simulations. It has been shown that our method provides an easily achievable method to provide an accurate determination of the elastic modulus of extremely soft matter typically applicable for moduli below 1 kPa. PMID:25873419
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
Muhs, Jeffrey D.; Capps, Gary J.; Smith, David B.; White, Clifford P.
1994-01-01
Fiber optic sensing means for the detection and measurement of events such as dynamic loadings imposed upon elastic materials including cementitious materials, elastomers, and animal body components and/or the attrition of such elastic materials are provided. One or more optical fibers each having a deformable core and cladding formed of an elastomeric material such as silicone rubber are embedded in the elastic material. Changes in light transmission through any of the optical fibers due the deformation of the optical fiber by the application of dynamic loads such as compression, tension, or bending loadings imposed on the elastic material or by the attrition of the elastic material such as by cracking, deterioration, aggregate break-up, and muscle, tendon, or organ atrophy provide a measurement of the dynamic loadings and attrition. The fiber optic sensors can be embedded in elastomers subject to dynamic loadings and attrition such as commonly used automobiles and in shoes for determining the amount and frequency of the dynamic loadings and the extent of attrition. The fiber optic sensors are also useable in cementitious material for determining the maturation thereof.
Structural and elastic properties of fcc/fcc metallic multilayers: A molecular-dynamics study
NASA Astrophysics Data System (ADS)
Tȩcza, Grzegorz W.
1992-12-01
Interplanar and intraplanar spacings as well as the elastic constants of fcc/fcc metallic multilayers stacked along [001] were determined via variable-cell molecular-dynamics simulation in (HtN) and (EhN) ensembles at room temperature. Qualitative differences in the structural and elastic properties of the multilayers, simulated using various 12-6 Lennard-Jones potentials, were observed. The anomalous behavior of the elastic constants and the biaxial modulus was linked to the modulation wavelength dependence of various structural parameters. The importance of the fluctuation contributions for the calculation of the full elastic constants is demonstrated.
Elastic Behavior of pr Substituted Y-123 Superconducting Materials
NASA Astrophysics Data System (ADS)
Dole, B. N.; Purushotham, Y.; Reddy, P. Venugopal; Shah, S. S.
The longitudinal (Vl) and shear (Vs) wave velocities of Praseodymium substituted YB2Cu3O7-δ high temperature superconductors were determined at room temperature by the pulse transmission technique. The values of Young's (E), rigidity (n) and bulk (k) moduli have been corrected to zero porosity. The zero porous corrected values of the elastic moduli are found to increase with increasing Praseodymium concentration. A linear relationship between the Debye temperature (θD) and average sound velocity (Vm) has also been observed and the behavior is explained qualitatively.
Nguyen, Ba Nghiep; Paquette, Joshua
2010-08-01
Fiber-reinforced polymer composites can offer important advantages over metals where lightweight, cost-effective manufacturing and high mechanical performance can be achieved. To date, these materials have not been used in hydropower systems. In view of the possibility to tailor their mechanical properties to specific applications, they now have become a subject of research for potential use in hydropower systems. The first step in any structural design that uses composite materials consists of evaluating the basic composite mechanical properties as a function of the as-formed composite microstructure. These basic properties are the elastic stiffness, stress-strain response, and strength. This report describes the evaluation of the elastic stiffness for a series of common discontinuous fiber polymer composites processed by injection molding and compression molding in order to preliminarily estimate whether these composites could be used in hydropower systems for load-carrying components such as turbine blades. To this end, the EMTA (Copyright © Battelle 2010) predictive modeling tool developed at the Pacific Northwest National Laboratory (PNNL) has been applied to predict the elastic properties of these composites as a function of three key microstructural parameters: fiber volume fraction, fiber orientation distribution, and fiber length distribution. These parameters strongly control the composite mechanical performance and can be tailored to achieve property enhancement. EMTA uses the standard and enhanced Mori-Tanaka type models combined with the Eshelby equivalent inclusion method to predict the thermoelastic properties of the composite based on its microstructure.
NASA Astrophysics Data System (ADS)
Oudry, Jennifer; Lynch, Ted; Vappou, Jonathan; Sandrin, Laurent; Miette, Véronique
2014-10-01
Elastographic techniques used in addition to imaging techniques (ultrasound, resonance magnetic or optical) provide new clinical information on the pathological state of soft tissues. However, system-dependent variation in elastographic measurements may limit the clinical utility of these measurements by introducing uncertainty into the measurement. This work is aimed at showing differences in the evaluation of the elastic properties of phantoms performed by four different techniques: quasi-static compression, dynamic mechanical analysis, vibration-controlled transient elastography and hyper-frequency viscoelastic spectroscopy. Four Zerdine® gel materials were tested and formulated to yield a Young’s modulus over the range of normal and cirrhotic liver stiffnesses. The Young’s modulus and the shear wave speed obtained with each technique were compared. Results suggest a bias in elastic property measurement which varies with systems and highlight the difficulty in finding a reference method to determine and assess the elastic properties of tissue-mimicking materials. Additional studies are needed to determine the source of this variation, and control for them so that accurate, reproducible reference standards can be made for the absolute measurement of soft tissue elasticity.
Determination of elastic properties of a film-substrate system by using the neural networks
NASA Astrophysics Data System (ADS)
Xu, Baiqiang; Shen, Zhonghua; Ni, Xiaowu; Wang, Jijun; Guan, Jianfei; Lu, Jian
2004-12-01
An inverse method based on artificial neural network (ANN) is presented to determine the elastic properties of films from laser-genrated surface waves. The surface displacement responses are used as the inputs for the ANN model; the outputs of the ANN are the Young's modulus, density, Poisson's ratio, and thickness of the film. The finite element method is used to calculate the surface displacement responses in a film-substrate system. Levenberg Marquardt algorithm is used as numerical optimization to speed up the training process for the ANN model. In this method, the materials parameters are not recovered from the dispersion curves but rather directly from the transient surface displacement. We have also found that this procedure is very efficient for determining the materials parameters of layered systems.
Investigating the elastic properties of sedimentary basins on different spatial scales
NASA Astrophysics Data System (ADS)
Krause, Martin; Methe, Pascal; Goepel, Andreas; Bleibinhaus, Florian; Kukowski, Nina
2014-05-01
The study of subsurface fluid motion is important e.g. for understanding ground water motion or processes of compaction, diagenesis, and hydrocarbon migration in sedimentary basins. The multidisciplinary project INFLUINS (INtegrated FLUid dynamics IN Sedimentary basins) aims for investigating the coupled dynamics of near surface and deep fluid patterns and material transport in the Thuringian Basin (Germany). In order to gain information on how fluid flow processes depend on basin architecture, and therefore its physical properties, we first image the subsurface structure of the Thuringian Basin using seismic methods. Then, relations between hydraulic and elastic material parameters are required to also image the hydraulic structure of the basin's subsurface. As hydraulic properties often significantly vary with spatial scales, such a study requires a combination of small- to large-scale seismic data sets. In the framework of INFLUINS a variety of seismic data sets aiming for different subsurface parameters and spatial scales have been acquired. Basin scale seismic data sets are available from a set of 2D reflection seismic profiles as well as 2.5D and 3D seismic travel time tomography. Laboratory scale seismic data characterizing the basin's rocks is provided by ultrasound experiments on drill cores from the Thuringian Basin. Deep drilling conducted in the framework of INFLUINS in 2013 provides further useful data sets for our purpose: we acquired core material for laboratory ultrasound analysis and sonic-log data. As the drill site is located at the cross point of two seismic reflection profiles and also within the array of seismic stations we used for the 3D travel time tomography, it serves a direct transfer of elastic properties between different scales.
Transversely isotropic elastic properties of multiwalled carbon nanotubes
NASA Astrophysics Data System (ADS)
Shen, Lianxi; Li, Jackie
2005-01-01
Five independent effective elastic moduli of a transversely isotropic multiwalled carbon nanotube (MWNT) are studied by analyzing its deformations under four loading conditions, i.e., axial tension, torsional moment, in-plane biaxial tension, and in-plane tension-compression stress. Two distributions of the tension loading on the outermost tube and on all tubes are considered, which correspond to the tensile and compressive Young’s moduli. The general relations between the interwall stresses and strains are linearized due to the small strain condition, where the interwall stresses correspond to the variation of the interwall van der Waals forces. Three interwall elastic constants are used to characterize the linear relations associated with three basic interwall deformation modes, i.e., normal deformation in radial direction and two shear deformations in axial and circumferential directions. By taking each tube as a single-walled carbon nanotube, the analytical expressions for the interwall shear stress under the tensile loading on the outermost tube and five elastic moduli of a double-walled carbon nanotube are first obtained. Then, a replacement method is proposed to derive the corresponding expressions for the cases of more walls than two. These analytical expressions are plotted for the case of MWNT’s composed of armchair tubes, where the interwall elastic constants are approximated as the corresponding ones of the graphite. The effect of the wall number, diameter, chirality, and length of the MWNT on the shear stress and five elastic moduli are displayed and discussed.
Studies on Effective Elastic Properties of CNT/Nano-Clay Reinforced Polymer Hybrid Composite
NASA Astrophysics Data System (ADS)
Thakur, Arvind Kumar; Kumar, Puneet; Srinivas, J.
2016-02-01
This paper presents a computational approach to predict elastic propertiesof hybrid nanocomposite material prepared by adding nano-clayplatelets to conventional CNT-reinforced epoxy system. In comparison to polymers alone/single-fiber reinforced polymers, if an additional fiber is added to the composite structure, it was found a drastic improvement in resultant properties. In this regard, effective elastic moduli of a hybrid nano composite are determined by using finite element (FE) model with square representative volume element (RVE). Continuum mechanics based homogenization of the nano-filler reinforced composite is considered for evaluating the volumetric average of the stresses and the strains under different periodic boundary conditions.A three phase Halpin-Tsai approach is selected to obtain the analytical result based on micromechanical modeling. The effect of the volume fractions of CNTs and nano-clay platelets on the mechanical behavior is studied. Two different RVEs of nano-clay platelets were used to investigate the influence of nano-filler geometry on composite properties. The combination of high aspect ratio of CNTs and larger surface area of clay platelets contribute to the stiffening effect of the hybrid samples. Results of analysis are validated with Halpin-Tsai empirical formulae.
NASA Astrophysics Data System (ADS)
Xu, C.; Li, Q.; Liu, C. M.; Duan, M. Y.; Wang, H. K.
2016-05-01
First-principles calculations are employed to investigate the structural and elastic properties, formation enthalpies and chemical bonding features as well as hardness values of chromium tetraboride (CrB4) with different structures. The lattice parameters, Poisson’s ratio and B/G ratio are also derived. Our calculations indicate that the orthorhombic structure with Pnnm symmetry is the most energetically stable one for CrB4. Except for WB4P63/mmc structure with imaginary frequencies, another six new structures are investigated through the full phonon dispersion calculations. Their mechanical and thermodynamic stabilities are also studied by calculating the elastic constants and formation enthalpies. Our calculations show that the thermodynamic stabilities of all these CrB4 phases can be enhanced under high pressure. The large shear moduli, Young’s moduli and hardness values indicate that these CrB4 phases are potential hard materials. Analyses of the densities of states (DOSs) and electron localization functions (ELFs) provide further understandings of the chemical and physical properties of these CrB4 phases. It is observed that the large occupations and high strengths of the B-B covalent bonds are important for the stabilities, incompressibility and hardnesses of these CrB4 phases.
Electronic, magnetic, elastic and thermodynamic properties of Cu2MnGa
NASA Astrophysics Data System (ADS)
Ghosh, Sukriti; Gupta, Dinesh C.
2016-08-01
The full-potential linearized augmented plane wave method in the stable Fm-3m phase has been implemented to investigate the structural, elastic, magnetic and electronic properties of Cu2MnGa. The optimized equilibrium lattice parameter in stable phase is found to be 5.9495 Å. By the spin resolved density of states calculations, we have shown that the exchange splitting due to Mn atom is the main reason of ferromagnetic behavior of Cu2MnGa. The absence of energy gap in both the spin channels predicts that the material is metallic. The total and partial density of states, elastic constants, Shear, Bulk and Young's moduli, Zener isotropy factor, Cauchy pressure, Pugh's ductility, Kleinman parameter and Poisson's ratio are reported for the first time for the alloy. Cauchy's pressure and Pugh's index of ductility label Cu2MnGa as ductile. Cu2MnGa is found to be ferromagnetic and anisotropic in nature. The quasi-harmonic approximations have been employed to study the pressure and temperature dependent thermodynamic properties of Cu2MnGa.
NASA Astrophysics Data System (ADS)
Yuping, Cang; Xiaoling, Yao; Dong, Chen; Fan, Yang; Huiming, Yang
2016-07-01
The ultrasoft pseudo-potential plane wave method combined with the quasi-harmonic approach have been used to study the electronic, elastic and thermodynamic properties of the tetragonal, monoclinic and orthorhombic Ge3N4. The negative formation enthalpies, the satisfactory of Born's criteria and the linear variations of elastic constants with pressure indicate that the three polymorphs can retain their stabilities in the pressure range of 0–25 GPa. The three Ge3N4 are brittle solids at 0 GPa, while they behave in ductile manners in the pressure range of 5–25 GPa. t- and o-Ge3N4 are hard materials but anisotropic. m-Ge3N4 has the largest ductility among the three phases. The results reveal that m-Ge3N4 belongs to an indirect band gap semiconductor, while t- and o-Ge3N4 have direct band gaps. For the thermal properties, several interesting features can be observed above 300 K. o-Ge3N4 exhibits the largest heat capacity, while m-Ge3N4 shows the highest Debye temperature. The results predicted in this work can provide reference data for future experiments. Project supported by the National Natural Science Foundation of China (Nos. 61475132, 11475143, 61501392, 11304141) and the National Training Programs of Innovation and Entrepreneurship for Undergraduates (No. 201510477001).
Urban Aerosol Optical Properties Measurement by Elastic Counter-Look Lidar
NASA Astrophysics Data System (ADS)
Wang, X.; Boselli, A.; He, Y.; Sannino, A.; Song, C.; Spinelli, N.
2016-06-01
The new developed elastic lidar system utilizes two identical elastic lidars, in counter-look configuration, to measure aerosol backscattering and extinction coefficients without any hypotheses. Compared to elastic-Raman lidar and high spectral resolution lidar, the proposed counter-look elastic lidar can use low power eyesafe laser and all available wavelengths. With this prototype lidar system, urban aerosol optical properties and their spatial distribution have been directly measured, including backscatter coefficient, extinction coefficient and lidar ratio. The preliminary results show that the low cost and eye-safe counter-look configured elastic lidar system can be used to measure the aerosol optical properties distribution and give the hint of aerosol type.
Structural and elastic properties of La{sub 2}Mg{sub 17} from first-principles calculations
Luo, Tao-Peng; Ma, Li; Pan, Rong-Kai; Zhou, Si-Chen; Wang, Hai-Chen; Tang, Bi-Yu
2013-10-15
Structural and elastic properties of La{sub 2}Mg{sub 17} with layer structure have been investigated within framework of the density functional theory. Different from the general layer-structured materials, the obtained c/a is less than unity. The calculated elastic constants C{sub 33} is larger than C{sub 11}, being novel in comparison with other alloys with layer structure. The calculated bulk, shear and Young’s modulus of La{sub 2}Mg{sub 17} are higher than other Mg–La alloys with higher La content, implying the stronger covalent bonding. Moreover, the elastic isotropies of La{sub 2}Mg{sub 17} are more excellent. The electronic structure within basal plane is highly symmetric, and the electronic interaction within basal plane is slightly weaker than one between basal planes, which reveal the underlying mechanism for the structural and elastic properties of La{sub 2}Mg{sub 17}. - Graphical abstract: The crystal structure (a) and the atomic positions for (b) (0 0 0 2), (c) (0 0 0 4) and (d) (1 2{sup ¯} 1 0) plane of La{sub 2}Mg{sub 17}. Display Omitted - Highlights: • The c/a of La{sub 2}Mg{sub 17} is anomalously less than unity. • It is novel that for La{sub 2}Mg{sub 17} the elastic constants C{sub 33} is larger than C{sub 11}. • The elastic modulus of La{sub 2}Mg{sub 17} is higher than other Mg–La alloys. • The elastic isotropy of La{sub 2}Mg{sub 17} is excellent. • The electronic structure within basal plane is highly symmetric.
Stokes, Ian A F; Laible, Jeffrey P; Gardner-Morse, Mack G; Costi, John J; Iatridis, James C
2011-01-01
Intervertebral disks support compressive forces because of their elastic stiffness as well as the fluid pressures resulting from poroelasticity and the osmotic (swelling) effects. Analytical methods can quantify the relative contributions, but only if correct material properties are used. To identify appropriate tissue properties, an experimental study and finite element analytical simulation of poroelastic and osmotic behavior of intervertebral disks were combined to refine published values of disk and endplate properties to optimize model fit to experimental data. Experimentally, nine human intervertebral disks with adjacent hemi-vertebrae were immersed sequentially in saline baths having concentrations of 0.015, 0.15, and 1.5 M and the loss of compressive force at constant height (force relaxation) was recorded over several hours after equilibration to a 300-N compressive force. Amplitude and time constant terms in exponential force-time curve-fits for experimental and finite element analytical simulations were compared. These experiments and finite element analyses provided data dependent on poroelastic and osmotic properties of the disk tissues. The sensitivities of the model to alterations in tissue material properties were used to obtain refined values of five key material parameters. The relaxation of the force in the three bath concentrations was exponential in form, expressed as mean compressive force loss of 48.7, 55.0, and 140 N, respectively, with time constants of 1.73, 2.78, and 3.40 h. This behavior was analytically well represented by a model having poroelastic and osmotic tissue properties with published tissue properties adjusted by multiplying factors between 0.55 and 2.6. Force relaxation and time constants from the analytical simulations were most sensitive to values of fixed charge density and endplate porosity. PMID:20711754
Structural, Elastic, Electronic Optical and Thermodynamic Properties of {ZnAl}2{S}4
NASA Astrophysics Data System (ADS)
Haddou, A.; Murtaza, G.; Khachai, H.; Khenata, R.; Bin Omran, S.; Ullah, Naeem; Varshney, Dinesh; Bouhemadou, A.
2015-11-01
The structural, elastic, electronic, optical, and thermodynamic properties of the {ZnAl}2{S}_{4 } compound are calculated in the frame work of the density functional theory where the calculated structural parameters are found to be in good agreement with the experimental data and other theoretical calculations. The calculations show that the material is elastically stable and isotropic. Furthermore, the calculated band gap is observed to be wide and direct and is comparable with earlier experimental data as well as with other theoretical calculations; hence, it is an optically active material for optoelectronic applications. In addition, the compound is found to have mixed ionic and covalent bonding nature. The optical nature of the compound is described in terms of the complex dielectric function, complex refractive index, reflectivity, and energy loss function. On the other hand, variation of the unit cell volume, bulk modulus, heat capacity, and Debye temperature are described as a function of temperature at different pressures for the {ZnAl}2{S}4 compound.
Elasto-Mammography: Elastic Property Reconstruction in Breast Tissues
Wang, Z. G.; Liu, Y.; Wang, G.; Sun, L. Z.
2008-02-15
Mammography is the primary method for screening and detecting breast cancers. However, it frequently fails to detect small tumors and is not quite specific in terms of tumor benignity and malignancy. The objective of this paper is to develop a new imaging modality called elasto-mammography that generates the modulus elastograms based on conventional mammographs. A new elastic reconstruction method is described based on elastography and mammography for breast tissues. Elastic distribution can be reconstructed through the measurement of displacement provided by mammographic projection. It is shown that the proposed elasto-mammography provides higher sensitivity and specificity than the conventional mammography on its own for breast cancer diagnosis.
Structural, electronic and elastic properties of the cubic CaTiO{sub 3} under pressure: A DFT study
Tariq, Saad Ahmed, Afaq; Tariq, Samar; Saad, Saher
2015-07-15
Using highly accurate FP-LAPW method with GGA approximation structural, electronic and elastic properties of cubic CaTiO{sub 3} have been calculated from 0-120 GPa range of pressure. It is observed that lattice constant, bond length and anisotropy factor decrease with increase in pressure. Also the brittle nature and indirect band-gap of the compound become ductile and direct band-gap respectively at 120 GPa. Moduli of elasticity, density of the material, Debye temperature and wave elastic wave velocities increase with increase in pressure. Spin dependent DOS’s plots show invariant anti-ferromagnetic nature of the compound under pressure. Our calculated results are in good agreement with available theoretical and experimental results.
Structural, electronic and elastic properties of the cubic CaTiO3 under pressure: A DFT study
NASA Astrophysics Data System (ADS)
Tariq, Saad; Ahmed, Afaq; Saad, Saher; Tariq, Samar
2015-07-01
Using highly accurate FP-LAPW method with GGA approximation structural, electronic and elastic properties of cubic CaTiO3 have been calculated from 0-120 GPa range of pressure. It is observed that lattice constant, bond length and anisotropy factor decrease with increase in pressure. Also the brittle nature and indirect band-gap of the compound become ductile and direct band-gap respectively at 120 GPa. Moduli of elasticity, density of the material, Debye temperature and wave elastic wave velocities increase with increase in pressure. Spin dependent DOS's plots show invariant anti-ferromagnetic nature of the compound under pressure. Our calculated results are in good agreement with available theoretical and experimental results.
Computation of elastic properties of 3D digital cores from the Longmaxi shale
NASA Astrophysics Data System (ADS)
Zhang, Wen-Hui; Fu, Li-Yun; Zhang, Yan; Jin, Wei-Jun
2016-06-01
The dependence of elastic moduli of shales on the mineralogy and microstructure of shales is important for the prediction of sweet spots and shale gas production. Based on 3D digital images of the microstructure of Longmaxi black shale samples using X-ray CT, we built detailed 3D digital images of cores with porosity properties and mineral contents. Next, we used finite-element (FE) methods to derive the elastic properties of the samples. The FE method can accurately model the shale mineralogy. Particular attention is paid to the derived elastic properties and their dependence on porosity and kerogen. The elastic moduli generally decrease with increasing porosity and kerogen, and there is a critical porosity (0.75) and kerogen content (ca. ≤3%) over which the elastic moduli decrease rapidly and slowly, respectively. The derived elastic moduli of gas- and oil-saturated digital cores differ little probably because of the low porosity (4.5%) of the Longmaxi black shale. Clearly, the numerical experiments demonstrated the feasibility of combining microstructure images of shale samples with elastic moduli calculations to predict shale properties.
Calculation of the elastic properties of a triangular cell core for lightweight composite mirrors
NASA Astrophysics Data System (ADS)
Penado, F. Ernesto; Clark, James H., III; Walton, Joshua P.; Romeo, Robert C.; Martin, Robert N.
2007-09-01
The use of composite materials in the fabrication of optical telescope mirrors offers many advantages over conventional methods, including lightweight, portability and the potential for lower manufacturing costs. In the construction of the substrate for these mirrors, sandwich construction offers the advantage of even lower weight and higher stiffness. Generally, an aluminum or Nomex honeycomb core is used in composite applications requiring sandwich construction. However, the use of a composite core offers the potential for increased stiffness and strength, low thermal distortion compatible with that of the facesheets, the absence of galvanic corrosion and the ability to readily modify the core properties. In order to design, analyze and optimize these mirrors, knowledge of the mechanical properties of the core is essential. In this paper, the mechanical properties of a composite triangular cell core (often referred to as isogrid) are determined using finite element analysis of a representative unit cell. The core studied offers many advantages over conventional cores including increased thermal and dimensional stability, as well as low weight. Results are provided for the engineering elastic moduli of cores made of high stiffness composite material as a function of the ply layup and cell size. Finally, in order to illustrate the use of these properties in a typical application, a 1.4-m diameter composite mirror is analyzed using the finite element method, and the resulting stiffness and natural frequencies are presented.
Elastic Properties of Nucleic Acids by Single-Molecule Force Spectroscopy.
Camunas-Soler, Joan; Ribezzi-Crivellari, Marco; Ritort, Felix
2016-07-01
We review the current knowledge on the use of single-molecule force spectroscopy techniques to extrapolate the elastic properties of nucleic acids. We emphasize the lesser-known elastic properties of single-stranded DNA. We discuss the importance of accurately determining the elastic response in pulling experiments, and we review the simplest models used to rationalize the experimental data as well as the experimental approaches used to pull single-stranded DNA. Applications used to investigate DNA conformational transitions and secondary structure formation are also highlighted. Finally, we provide an overview of the effects of salt and temperature and briefly discuss the effects of contour length and sequence dependence. PMID:27145878
Elastic properties of alpha quartz and the alkali halides based on an interatomic force model.
NASA Technical Reports Server (NTRS)
Weidner, D. J.; Simmons, G.
1972-01-01
A two-body central-force atomic model can be used to describe accurately the elastic properties of alpha quartz if the nontetrahedral O:O forces are included. The strength of the Si:O interaction has little effect on the bulk modulus. The technique is sufficiently general to allow calculations of the elastic properties of a specified structure under arbitrary pressure from a complete description of the interatomic forces. The elastic constants for the NaCl structure and the CsCl structure are examined. Our model includes two-body, central, anion-anion, anion-cation, and electrostatic interactions.
Mechanical properties of nanophase materials
Siegel, R.W.; Fougere, G.E.
1993-11-01
It has become possible in recent years to synthesize new materials under controlled conditions with constituent structures on a nanometer size scale (below 100 nm). These novel nanophase materials have grain-size dependent mechanical properties significantly different than those of their coarser-grained counterparts. For example, nanophase metals are much stronger and apparently less ductile than conventional metals, while nanophase ceramics are more ductile and more easily formed than conventional ceramics. The observed mechanical property changes are related to grain size limitations and/or the large percentage of atoms in grain boundary environments; they can also be affected by such features as flaw populations, strains and impurity levels that can result from differing synthesis and processing methods. An overview of what is presently known about the mechanical properties of nanophase materials, including both metals and ceramics, is presented. Some possible atomic mechanisms responsible for the observed behavior in these materials are considered in light of their unique structures.
Effect of Water on Elastic and Creep Properties of Self-Standing Clay Films.
Carrier, Benoit; Vandamme, Matthieu; Pellenq, Roland J-M; Bornert, Michel; Ferrage, Eric; Hubert, Fabien; Van Damme, Henri
2016-02-01
We characterized experimentally the elastic and creep properties of thin self-standing clay films, and how their mechanical properties evolved with relative humidity and water content. The films were made of clay montmorillonite SWy-2, obtained by evaporation of a clay suspension. Three types of films were manufactured, which differed by their interlayer cation: sodium, calcium, or a mixture of sodium with calcium. The orientational order of the films was characterized by X-ray diffractometry. The films were mechanically solicited in tension, the resulting strains being measured by digital image correlation. We measured the Young's modulus and the creep over a variety of relative humidities, on a full cycle of adsorption-desorption for what concerns the Young's modulus. Increasing relative humidity made the films less stiff and made them creep more. Both the elastic and creep properties depended significantly on the interlayer cation. For the Young's modulus, this dependence must originate from a scale greater than the scale of the clay layer. Also, hysteresis disappeared when plotting the Young's modulus versus water content instead of relative humidity. Independent of interlayer cation and of relative humidity greater than 60%, after a transient period, the creep of the films was always a logarithmic function of time. The experimental data gathered on these mesoscale systems can be of value for modelers who aim at predicting the mechanical behavior of clay-based materials (e.g., shales) at the engineering macroscopic scale from the one at the atomistic scale, for them to validate the first steps of their upscaling scheme. They provide also valuable reference data for bioinspired clay-based hybrid materials. PMID:26752345
NASA Astrophysics Data System (ADS)
Mueller, H. J.
2011-12-01
The Earth's deep interior is only accessible by indirect methods, first and foremost seismological studies. The interpretation of these seismic data and the corresponding numerical modelling requires measurements of the elastic properties of representative Earth materials under experimental simulated in-situ pressure-temperature conditions. For experiments under uppermost mantle conditions highly metamorphic and exhumed natural rocks can still be used as specimen. The benefit of considering a natural texture is attended by the possible influence of minor retrograde metamorphosis. The simulation of transition zone conditions and beyond require multi-anvil devices, also called as large volume presses, because they provide sample volumes 3 to 7 orders of magnitude bigger than in diamond anvil cells. 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 at the same time. The sample deformation under in-situ conditions is measured by X-radiography. Various experimental techniques and their results are described including standard-free pressure measurement, elastic properties across unquenchable phase transitions, measurements with molten encapsulated samples and falling sphere viscosimetry.
NASA Astrophysics Data System (ADS)
Le Page, Yvon; Saxe, Paul
2002-03-01
generality of the approach described here enabled the creation of a robust user interface going seamlessly from the database search to the printout of the elastic coefficients. With it, even nonspecialist users can reliably produce technologically relevant results like those discussed here in a simple point-and-click fashion from corresponding entries in the CRYSTMET® and ICSD® structure databases, i.e., for all pure-phase nonorganic materials with known crystal structure. The case of Ti4As3 exposes, on a first cluster of properties, stiffness, compliance, and the isotropic properties that can be derived from them, the current reality of mining crystal structure databases with ab initio software for technological properties that were never measured before. Further developments in that direction are currently underway.
MaterialCloning: Acquiring Elasticity Parameters from Images for Medical Applications.
Yang, Shan; Lin, Ming C
2016-09-01
We present a practical approach for automatically estimating the material properties of soft bodies from two sets of images, taken before and after deformation. We reconstruct 3D geometry from the given sets of multiple-view images; we use a coupled simulation-optimization-identification framework to deform one soft body at its original, non-deformed state to match the deformed geometry of the same object in its deformed state. For shape correspondence, we use a distance-based error metric to compare the estimated deformation fields against the actual deformation field from the reconstructed geometry. The optimal set of material parameters is thereby determined by minimizing the error metric function. This method can simultaneously recover the elasticity parameters of multiple types of soft bodies using Finite Element Method-based simulation (of either linear or nonlinear materials undergoing large deformation) and particle-swarm optimization methods. We demonstrate this approach on real-time interaction with virtual organs in patient-specific surgical simulation, using parameters acquired from low-resolution medical images. We also highlight the results on physics-based animation of virtual objects using sketches from an artist's conception. PMID:26661471
NASA Astrophysics Data System (ADS)
Wei, Ning; Zhang, Xiaoli; Zhang, Chuanguo; Hou, Songjun; Zeng, Z.
2015-10-01
We have investigated the elastic and thermodynamic properties of ZrO2 under pressure up to 120 Gpa by the plane wave pseudopotential density functional theory with the generalized gradient approximation (GGA) method. The elastic constants of ZrO2 are calculated and meet the generalized stability criteria, suggesting that ZrO2 is mechanically stable within this pressure range. The pressure effects on the elastic properties reveal that the elastic modulus B, shear modulus G and Young's modulus Y increase linearly with the pressure increasing, implying that the resistance to deformation is enhanced. In addition, by analyzing the Poisson's ratio ν and the value of B/G, we notice that ZrO2 is regarded as being a ductile material under high pressure and the ductility can be improved by the pressure increasing. Then, we employ the quasi-harmonic Debye model considering the phononic effects to obtain the thermodynamic properties of ZrO2. Debye temperature ΘD, thermal expansion coefficient α, heat capacity Cp and Grüneisen parameter γ are systematically explored at pressure of 0-80 Gpa and temperature of 0-1000 K. Our results have provided fundamental facts and evidences for further experimental and theoretical researches.
Elastic Properties of Clay Minerals Determined by Atomic Force Acoustic Microscopy Technique
NASA Astrophysics Data System (ADS)
Kopycinska-Müller, M.; Prasad, M.; Rabe, U.; Arnold, W.
Seismic wave propagation in geological formations is altered by the presence of clay minerals. Knowledge about the elastic properties of clay is therefore essential for the interpretation and modeling of the seismic response of clay-bearing formations. However, due to the layered structure of clay, it is very difficult to investigate its elastic properties. We measured elastic properties of clay using atomic force acoustic microscopy (AFAM). The forces applied during the experiments were not higher than 50 nN. The adhesion forces were measured from the pull-off forces and included into our calculations by means of the Derjaguin-Mueller-Toporov model for contact mechanics. The obtained values of the elastic modulus for clay varied from 10 to 17 GPa depending on various parameters that describe the dynamics of a vibrating beam
The role of material properties in adhesion
NASA Technical Reports Server (NTRS)
Buckley, D. H.
1984-01-01
When two solid surfaces are brought into contact strong adhesive bond forces can develop between the materials. The magnitude of the forces will depend upon the state of the surfaces, cleanliness and the fundamental properties of the two solids, both surface and bulk. Adhesion between solids is addressed from a theoretical consideration of the electronic nature of the surfaces and experimentally relating bond forces to the nature of the interface resulting from solid state contact. Surface properties correlated with adhesion include, atomic or molecular orientation, reconstruction and segregation as well as the chemistry of the surface specie. Where dissimilar solids are in contact the contribution of each is considered as is the role of their interactive chemistry on bond strength. Bulk properties examined include elastic and plastic behavior in the surficial regions, cohesive binding energies, crystal structure, crystallographic orientation and state. Materials examined with respect to interfacial adhesive interactions include metals, alloys, ceramics, polymers and diamond. They are reviewed both in single and polycrystalline form. The surfaces of the contacting solids are studied both in the atomic or molecularly clean state and in the presence of selected surface contaminants.
Elastic properties of sand-peat moss mixtures from ultrasonic measurements
Trombino, C N
1998-09-02
Effective remediation of an environmental site requires extensive knowledge of the geologic setting, as well as the amount and distribution of contaminants. Seismic investigations provide a means to examine the subsurface with minimum disturbance, Laboratory measurements are needed to interpret field data. In this experiment, laboratory tests were performed to characterize manufactured soil samples in terms of their elastic properties. The soil samples consisted of small (mass) percentages (1 to 20 percent) of peat moss mixed with pure quartz sand. Sand was chosen as the major component because its elastic properties are well known except at the lowest pressures. The ultrasonic pulse transmission technique was used to collect elastic wave velocity data. These data were analyzed and mathematically processed to calculate the other elastic properties such as the modulus of elasticity. This experiment demonstrates that seismic data are affected by the amount~of peat moss added to pure sand samples. Elastic wave velocities, velocity gradients, and elastic moduli vary with pressure and peat moss amounts. In particular, ultrasonic response changes dramatically when pore space fills with peat. With some further investigation, the information gathered in this experiment could be applied to seismic field research.
Residual stresses calculation in autofrettage using variable material properties method
Jahed, H.; Dubey, R.N.
1996-12-01
Autofrettaged cylinders are used for variety of applications in chemical and nuclear industries where large internal pressures have to be withstood. Autofrettage is in the process by which beneficial residual stresses are introduced into thick-walled tubes by initially subjected the tube to high internal pressure which causes inelastic deformation. Here, the variable material properties method is employed to obtain elastic-plastic analysis of an autofrettaged tube. This method develops inelastic solution from the elastic solution by treating the material properties as field variables. The distribution of these parameters are obtained in an iterative manner as a part of the solution. An energy based scheme is used to update these variables. The residual stress field of autofrettaged tubes based on the actual material curve and isotropic and kinematic hardening models are obtained. The results are shown to be in good agreement with the published experimental and finite element results.
NASA Astrophysics Data System (ADS)
Bouvier, Adeline; Deleaval, Flavien; Doyley, Marvin M.; Yazdani, Saami K.; Finet, Gérard; Le Floc'h, Simon; Cloutier, Guy; Pettigrew, Roderic I.; Ohayon, Jacques
2013-12-01
The peak cap stress (PCS) amplitude is recognized as a biomechanical predictor of vulnerable plaque (VP) rupture. However, quantifying PCS in vivo remains a challenge since the stress depends on the plaque mechanical properties. In response, an iterative material finite element (FE) elasticity reconstruction method using strain measurements has been implemented for the solution of these inverse problems. Although this approach could resolve the mechanical characterization of VPs, it suffers from major limitations since (i) it is not adapted to characterize VPs exhibiting high material discontinuities between inclusions, and (ii) does not permit real time elasticity reconstruction for clinical use. The present theoretical study was therefore designed to develop a direct material-FE algorithm for elasticity reconstruction problems which accounts for material heterogeneities. We originally modified and adapted the extended FE method (Xfem), used mainly in crack analysis, to model material heterogeneities. This new algorithm was successfully applied to six coronary lesions of patients imaged in vivo with intravascular ultrasound. The results demonstrated that the mean relative absolute errors of the reconstructed Young's moduli obtained for the arterial wall, fibrosis, necrotic core, and calcified regions of the VPs decreased from 95.3±15.56%, 98.85±72.42%, 103.29±111.86% and 95.3±10.49%, respectively, to values smaller than 2.6 × 10-8±5.7 × 10-8% (i.e. close to the exact solutions) when including modified-Xfem method into our direct elasticity reconstruction method.
Metric Description of Defects in Amorphous Elastic Materials
NASA Astrophysics Data System (ADS)
Moshe, Michael; Sharon, Eran; Kupferman, Raz
2014-03-01
We suggest a description for dislocations, using a torsion-free Riemannian manifold equipped with a reference metric. This metric expresses the local equilibrium geometry within the material. In this description, dislocations are singularities in the intrinsic curvature structure. The model is not based on a crystalline structure; therefore it can describe dislocations even in amorphous materials. We provide explicit expression for edge dislocation, which is a dipole of curvature. Apparently, higher multipoles of curvature can be used to describe plastic deformations in amorphous materials. The model is supported with experimental results.
A modified direct method for the calculation of elastic moduli of composite materials
Wang, J.A.; Lubliner, J.; Monteiro, P.J.M.
1996-02-01
The modified direct method is a scheme for the estimation of elastic moduli of composite materials and is based on micromechanical theory and classical elasticity. Using the statistical homogeneous assumption and the two-phase composite approach, one takes the average field of the composite. Due to the complexity of composite materials, the modeling parameters for the exact analytical theory are not always available and then the effective bounds are usually too wide for practical application. For engineering purposes a more practical and general model is desired. The modified direct method was developed to approach the above requirements. In this work the modified direct method is compared with different available experiment data and methods, for example, Kuster-Toksoez, Christensen-Lo. The comparison results show that the modified direct method provides a very good estimation of the elastic moduli in different kinds of problems, such as the soft and hard inclusion cases, porous materials, at various concentrations and/or various porosities.
Property Status of Lunar Material
NASA Astrophysics Data System (ADS)
Pop, V.
Most of the lunar material in private hands is of meteoric origin, and its property sta- tus does not present many challenges. The intention of Applied Space Resources, Inc, to fly a commercial lunar sample return mission and to subsequently offer lunar ma- terial for sale, raises the issue of the legality of exploitation and private ownership of retrieved lunar material. Lunar samples have been returned in the past by means of the Apollo (US) and Luna (USSR) missions and, while most of the material re- mains government property and is used for scientific means, a small fraction has been transferred abroad and some has entered the private market. Apollo-collected moon- rocks have been offered, symbolically, to heads of States, and some foreign nations have subsequently transferred ownership to private individuals. The same, lunar ma- terial of Soviet provenience has entered the private market, this forming a valuable legal precedent for the lawfulness of sale of lunar material. Recently, plans were made public to award the Apollo astronauts with lunar rocks. While in the US there is a popular misconception that it is illegal to own lunar material, the truth lies elsewhere. As the Apollo samples are the property of the US government and a small fraction was stolen, lost, or misplaced, the US government intends to recover this material, unlawfully owned. In the same time, a significant number of individuals have been prosecuted for offering for sale fake lunar rocks. The present paper will analyse the different categories of lunar material according to its ownership status, and will as- sert that private property of lunar material is lawful, and lunar material that will be returned in the future will be able to enter the market without hindrances.
Spatial mapping of the electrical and elastic properties of granular media
NASA Astrophysics Data System (ADS)
Greeney, Nathan S.
The goal of this research is to design a set of methods to spatially map the electrical and physical properties of a spatially complex granular material. Aiming for a resolution of sub-millimeter allows the the possibility for developing a relationship between the electrical and physical properties at this scale as well as the ability to upscale to larger scales. Spatial mapping at this scale fills a unique niche between existing methods in the microscopic and macroscopic scales. Using methods analogous with optical near-field scanning, we develop a millimeter near-field scanning system. This system spatially scans thin samples between two dielectric probes to map the spatially varying dielectric properties of the sample. Using a millimeter wave vector network analyzer allows us to directly measure the phase and amplitude of the reflected and transmitted fields allowing mapping of both the real and imaginary parts of the dielectric properties. With this system we achieve a resolution of 100 mum (smaller than lambda/10). This resolution is not limited by diffraction but limited by the size of our probe and has the possibility of improvement. In order to develop a high resolution spatial mapping of the physical properties we developed an unconventional laser ultrasound scanning system. This system measures the travel time of shear waves directly through the sample to localize measurements allowing high resolution mapping of the spatially varying elastic properties of the sample. Using a focused infrared laser and laser Doppler vibrometer on opposite sides of a thin sample, we are able to achieve sub-millimeter resolution limited by the spot size and thickness of the sample. In testing these systems we looked at various applications. We have mapped the mineralogy of heterogeneous granite and have looked into a correlation between electrical and mechanical properties properties. By looking at maps of oil shale we are able to see the spatial hydrocarbon content before
Pedesseau, L. E-mail: jacky.even@insa-rennes.fr; Even, J. E-mail: jacky.even@insa-rennes.fr; Durand, O.; Modreanu, M.; Chaussende, D.; Sarigiannidou, E.; Chaix-Pluchery, O.
2015-12-01
New experimental results supported by theoretical analyses are proposed for aluminum silicon carbide (Al{sub 4}SiC{sub 4}). A state of the art implementation of the density functional theory is used to analyze the experimental crystal structure, the Born charges, the elastic properties, and the piezoelectric properties. The Born charge tensor is correlated to the local bonding environment for each atom. The electronic band structure is computed including self-consistent many-body corrections. Al{sub 4}SiC{sub 4} material properties are compared to other wide band gap wurtzite materials. From a comparison between an ellipsometry study of the optical properties and theoretical results, we conclude that the Al{sub 4}SiC{sub 4} material has indirect and direct band gap energies of about 2.5 eV and 3.2 eV, respectively.
Elastic properties of silver borate glasses doped with praseodymium oxide
Gowda, G. V. Jagadeesha; Eraiah, B.
2014-04-24
A series of glasses xPr{sub 6}O{sub 11−}(35−x) Ag{sub 2}O−65B{sub 2}O{sub 3} with x=0, 0.1, 0.2, 0.3, 0.4 and 0.5 mol % were synthesized by melt quenching technique. Longitudinal and shear ultrasonic velocity were measured at 5 MHz frequency and at room temperature. Elastic moduli, Poisson's ratio and Debye temperature have been calculated from the measured density and ultrasonic velocity at room temperature. The experimental results indicate that the elastic constants depend upon the composition of the glasses. The role of the Pr{sub 6}O{sub 11} inside the glass network was discussed.
Coupled magnetic and elastic properties in LaPr(CaSr)MnO manganites
NASA Astrophysics Data System (ADS)
Eslava, G. G.; Parisi, F.; Bernardo, P. L.; Quintero, M.; Leyva, G.; Cohen, L. F.; Ghivelder, L.
2016-09-01
We investigate a series of manganese oxides, the La0.225Pr0.4(Ca1-xSrx)0.375MnO3 system. The x = 0 sample is a prototype compound for the study of phase separation in manganites, where ferromagnetic and charge ordered antiferromagnetic phases coexist. Replacing Ca2+ by Sr2+ gradually turns the system into a homogeneous ferromagnet. Our results show that the material structure plays a major role in the observed magnetic properties. On cooling, at temperatures below ∼ 100 K, a strong contraction of the lattice is followed by an increase in the magnetization. This is observed both through thermal expansion and magnetostriction measurements, providing distinct evidence of magneto-elastic coupling in these phase separated compounds.
First-principles study of structural, elastic, and electronic properties of chromium carbides
NASA Astrophysics Data System (ADS)
Jiang, Chao
2008-01-01
Using first-principles calculations, we systematically studied the structural, elastic, and electronic properties of the technologically important chromium carbides: Cr3C2, Cr7C3, Cr23C6, Cr3C, and CrC. Our calculations show that the ground state structure for Cr7C3 is hexagonal, not orthorhombic. We further predict WC to be the energetically most stable structure for CrC. Our results indicate that all chromium carbides considered in this study are metallic and mechanically stable under the ambient condition. Among all chromium carbides, WC-type CrC exhibits the highest bulk and shear moduli and the lowest Poisson's ratio, and is a potential low-compressibility and hard material.
Elastic properties of a-C :N:H films
NASA Astrophysics Data System (ADS)
Wang, Chengbing; Yang, Shengrong; Li, Hongxuan; Zhang, Junyan
2007-01-01
Dual dc-rf plasma system has been used to deposit hydrogenated carbon nitride (CNx:H) films that exhibit high elastic recovery (75%). Transmission electron microscopy (TEM), Fourier transform infrared (FTIR) spectra and Raman spectra were subsequently used to study the microstructure and bonding of the resultant films. The structure of the films from TEM is seen to consist of many particles embedded in an amorphous carbon matrix, and the films can be described as graphitelike or onionlike with interplanar distances of ≈1.15, 1.95, and 3.5Å, as obtained from selected area electron diffraction (SAED). FTIR shows that nitrogen promotes the formation of sp2 C C/CN aromatic rings in the films. Raman spectra shows two apparent peaks at about 700 and 1200cm-1 in addition to the G and D peaks. Only by adding two extra peaks at approximately 1230 and 1470cm-1 can we deconvolute the Raman spectra of CNx:H in the region of 1000-2000cm-1. Combining TEM and SAED, we attribute the three peaks at about 700, 1200, and 1470cm-1 to fullerene or onion structure. However, the elastic recovery is relatively lower than elastic hydrogenated free carbon nitride films. We think that this is due to the fact that hydrogen is mainly incorporated to sp3 carbon and suppresses cross-linking three-dimensional (3D) network growth.
Properties of aircraft tire materials
NASA Technical Reports Server (NTRS)
Dodge, Richard N.; Clark, Samuel K.
1988-01-01
A summary is presented of measured elastomeric composite response suitable for linear structural and thermoelastic analysis in aircraft tires. Both real and loss properties are presented for a variety of operating conditions including the effects of temperature and frequency. Suitable micro-mechanics models are used for predictions of these properties for other material combinations and the applicability of laminate theory is discussed relative to measured values.
NASA Astrophysics Data System (ADS)
Varshney, Dinesh; Jain, S.; Shriya, S.; Khenata, R.
2016-04-01
Pressure- and temperature-dependent mechanical, elastic, and thermodynamical properties of rock salt to CsCl structures in semiconducting SrX (X = O, S, Se, and Te) chalcogenides are presented based on model interatomic interaction potential with emphasis on charge transfer interactions, covalency effect, and zero point energy effects apart from long-range Coulomb, short-range overlap repulsion extended and van der Waals interactions. The developed potential with non-central forces validates the Cauchy discrepancy among elastic constants. The volume collapse (V P/V 0) in terms of compressions in SrX at higher pressure indicates the mechanical stiffening of lattice. The expansion of SrX lattice is inferred from steep increase in V T/V 0 and is attributed to thermal softening of SrX lattice. We also present the results for the temperature-dependent behaviors of hardness, heat capacity, and thermal expansion coefficient. From the Pugh's ratio (ϕ = B T /G H), the Poisson's ratio (ν) and the Cauchy's pressure (C 12-C 44), we classify SrO as ductile but SrS, SrSe, and SrTe are brittle material. To our knowledge these are the first quantitative theoretical prediction of the pressure and temperature dependence of mechanical stiffening, thermally softening, and brittle nature of SrX (X = O, S, Se, and Te) and still await experimental confirmations.
NASA Astrophysics Data System (ADS)
Varshney, Dinesh; Jain, S.; Shriya, S.; Khenata, R.
2016-09-01
Pressure- and temperature-dependent mechanical, elastic, and thermodynamical properties of rock salt to CsCl structures in semiconducting Sr X ( X = O, S, Se, and Te) chalcogenides are presented based on model interatomic interaction potential with emphasis on charge transfer interactions, covalency effect, and zero point energy effects apart from long-range Coulomb, short-range overlap repulsion extended and van der Waals interactions. The developed potential with non-central forces validates the Cauchy discrepancy among elastic constants. The volume collapse ( V P/ V 0) in terms of compressions in Sr X at higher pressure indicates the mechanical stiffening of lattice. The expansion of Sr X lattice is inferred from steep increase in V T/ V 0 and is attributed to thermal softening of Sr X lattice. We also present the results for the temperature-dependent behaviors of hardness, heat capacity, and thermal expansion coefficient. From the Pugh's ratio (ϕ = B T /G H), the Poisson's ratio ( ν) and the Cauchy's pressure ( C 12- C 44), we classify SrO as ductile but SrS, SrSe, and SrTe are brittle material. To our knowledge these are the first quantitative theoretical prediction of the pressure and temperature dependence of mechanical stiffening, thermally softening, and brittle nature of Sr X ( X = O, S, Se, and Te) and still await experimental confirmations.
Salguero, Laura; Saadat, Fatemeh; Sevostianov, Igor
2014-10-17
The paper analyzes the connection between microstructure of the osteonal cortical bone and its overall elastic properties. The existing models either neglect anisotropy of the dense tissue or simplify cortical bone microstructure (accounting for Haversian canals only). These simplifications (related mostly to insufficient mathematical apparatus) complicate quantitative analysis of the effect of microstructural changes - produced by age, microgravity, or some diseases - on the overall mechanical performance of cortical bone. The present analysis fills this gap; it accounts for anisotropy of the dense tissue and uses realistic model of the porous microstructure. The approach is based on recent results of Sevostianov et al. (2005) and Saadat et al. (2012) on inhomogeneities in a transversely-isotropic material. Bone's microstructure is modeled according to books of Martin and Burr (1989), Currey (2002), and Fung (1993) and includes four main families of pores. The calculated elastic constants for porous cortical bone are in agreement with available experimental data. The influence of each of the pore types on the overall moduli is examined. PMID:25234350
Functional Properties of Nanostructured Materials
NASA Astrophysics Data System (ADS)
Kassing, Rainer; Petkov, Plamen; Kulisch, Wilhelm; Popov, Cyril
This book, based on the lectures and contributions of the NATO ASI on "Functional Properties of Nanostructured Materials", gives a broad overview on this topic, as it combines basic theoretical articles, papers dealing with experimental techniques, and contributions on advanced and up-to-date applications in fields such as microelectronics, optoelectronics, electrochemistry, sensorics, and biotechnology. In addition, it presents an interdisciplinary approach since the authors came from such different fields as physics, chemistry, engineering, materials science and biology.
Quantitative nondestructive characterization of visco-elastic materials at high pressure
Aizawa, Tatsuhiko; Kihara, Junji; Ohno, Jun
1995-11-01
New anvil apparatus was developed to realize high pressure atmosphere suitable to investigation of viscoelastic behaviors of such soft materials as polymers, lubricants, proteins and so forth. In addition, ultrasonic spectroscopy system was also newly constructed to make quantitative nondestructive evaluation of elasticity and viscosity of soft materials at high pressure. In order to demonstrate the validity and effectiveness of the developed system and methodology for quantitative nondestructive visco-elastic characterization, various silicone oils are employed, and measured spectra are compared to the theoretical results calculated by the three linear element model.
Martin, S.E.; Newman, J.B.
1980-11-01
A thermomechanical theory of large deformation elastic-inelastic material behavior is developed which is based on a multiplicative decomposition of the strain. Very general assumptions are made for the elastic and inelastic constitutive relations and effects such as thermally-activated creep, fast-neutron-flux-induced creep and growth, annealing, and strain recovery are compatible with the theory. Reduced forms of the constitutive equations are derived by use of the second law of thermodynamics in the form of the Clausius-Duhem inequality. Observer invariant equations are derived by use of an invariance principle which is a generalization of the principle of material frame indifference.
NASA Astrophysics Data System (ADS)
Knackstedt, Mark A.; Arns, Christoph H.; Saadatfar, Mohammad; et al.
2006-09-01
We describe a three-dimensional imaging and analysis study of eight industrial cellular foam morphologies. The foam morphologies were generated by differing industrial processing methods. Tomograms are acquired on an X-ray micro-computed tomography facility at scales of approximately equal to (5mm)3 at resolutions down to 7μm. The image quality is sufficient in all cases to measure local structure and connectivity of the foamed material, and the field of view large enough to calculate a range of material properties. Phase separation into solid and porous components is straightforward.Three-dimensional structural characteristics are measured directly on the porous and solid phases of the images. A number of morphological parameters are obtained, including pore volume-to-surface-area ratio, connectivity, the pore and solid phase size distributions defined by maximal sphere openings and chord length measurements. We further calculate the pore size distribution associated with capillary pressure via simulating of mercury drainage on the digital images.The binarized microstructures are used as a basis for calculations of transport properties (fluid permeability, diffusivity and thermal conductivity) and elastic moduli. From the data, we generate property-porosity relationships for the range of foam morphologies imaged and quantitatively analyse the effects of porosity and microstructure on the resultant properties of the foams.We compare our numerical data to commonly used theoretical and empirical property-porosity relationships. For thermal conductivity, we find that the numerical results agree extremely well with an empirical expression based on experimental data of various foams. The upper Hashin-Shtrikman bound also provides an excellent prediction of the data across all densities. From simulation of the diffusivity, we can define the tortuosity of the pore space within the cellular solid. We find that different processing methods lead to strong variations in the
Zhang, Da-Guang; Li, Meng-Han; Zhou, Hao-Miao
2015-10-15
For magnetostrictive rods under combined axial pre-stress and magnetic field, a general one-dimension nonlinear magneto-elastic coupled constitutive model was built in this paper. First, the elastic Gibbs free energy was expanded into polynomial, and the relationship between stress and strain and the relationship between magnetization and magnetic field with the polynomial form were obtained with the help of thermodynamic relations. Then according to microscopic magneto-elastic coupling mechanism and some physical facts of magnetostrictive materials, a nonlinear magneto-elastic constitutive with concise form was obtained when the relations of nonlinear strain and magnetization in the polynomial constitutive were instead with transcendental functions. The comparisons between the prediction and the experimental data of different magnetostrictive materials, such as Terfenol-D, Metglas and Ni showed that the predicted magnetostrictive strain and magnetization curves were consistent with experimental results under different pre-stresses whether in the region of low and moderate field or high field. Moreover, the model can fully reflect the nonlinear magneto-mechanical coupling characteristics between magnetic, magnetostriction and elasticity, and it can effectively predict the changes of material parameters with pre-stress and bias field, which is useful in practical applications.
Ikezoe, Tome; Umegaki, Hiroki; Kobayashi, Takuya; Nishisita, Satoru; Ichihashi, Noriaki
2016-01-01
Background Passive mechanical properties are important in muscle function because they are related to the muscle extensibility. Recently, the assessment of muscle shear elastic modulus using shear-wave elastographic (SWE) imaging was developed. However, reliability and validity of shear elastic modulus measurements during passive stretching remain undefined. Purpose To investigate the reproducibility and validity of the shear elastic modulus measured by SWE imaging during passive stretching. Material and Methods Ten healthy men volunteered for this study. The shear elastic modulus of medial gastrocnemius (MG) muscle belly was measured using ultrasonic SWE imaging during passive dorsiflexion. To assess the intra-session and inter-day reliabilities, the protocol was performed twice by the same investigator with a 5-min rest period between measurement sessions and twice on two different days by the same investigator with a 1–2-week interval between the two sessions. To assess the inter-investigator reliability, the protocol was performed on the same day by two investigators with a 5-min rest between measurement sessions. In addition, B-mode ultrasonography was used to determine the displacement of myotendinous junction (MTJ) of MG during passive ankle dorsiflexion. Results The intra-session, inter-day, and inter-investigator reliabilities of the method was confirmed on the basis of acceptably low coefficient of variations and substantially high intraclass correlation coefficients. In addition, a significant correlation was found between MTJ displacement and shear elastic modulus. Conclusion These results suggested that shear elastic modulus measured using SWE imaging is a reproducible index reflecting the passive mechanical properties. PMID:27170845
Ni, Yilu; Tang, Zhurong; Cao, Wanxu; Lin, Hai; Fan, Yujiang; Guo, Likun; Zhang, Xingdong
2015-03-01
Natural polysaccharides are extensively investigated as cell scaffold materials for cellular adhesion, proliferation, and differentiation due to their excellent biocompatibility, biodegradability, and biofunctions. However, their application is often severely limited by their mechanical behavior. In this study, a tough and elastic hydrogel scaffold was prepared with hyaluronic acid (HA) and chondroitin sulfate (CS). HA and CS were conjugated with tyramine (TA) and the degree of substitution (DS) was 10.7% and 11.3%, respectively, as calculated by (1)H NMR spectra. The hydrogel was prepared by mixing HA-TA and CS-TA in presence of H2O2 and HRP. The sectional morphology of hydrogels was observed by SEM, static and dynamic mechanical properties were analyzed by Shimadzu electromechanical testing machine and dynamic mechanical thermal analyzer Q800. All samples showed good ability to recover their appearances after deformation, the storage modulus (E') of hydrogels became higher as the testing frequency went up. Hydrogels also showed fatigue resistance to cyclic compression. Mesenchymal stem cells encapsulated in hydrogels showed good cell viability as detected by CLSM. This study suggests that the hydrogels have both good mechanical properties and biocompatibility, and may serve as model systems to explore mechanisms of deformation and energy dissipation or find some applications in tissue engineering. PMID:25445680
Ilegbusi, Olusegun; Li, Ziang; Min, Yugang; Meeks, Sanford; Kupelian, Patrick; Santhanam, Anand P
2012-01-01
The aim of this paper is to model the airflow inside lungs during breathing and its fluid-structure interaction with the lung tissues and the lung tumor using subject-specific elastic properties. The fluid-structure interaction technique simultaneously simulates flow within the airway and anisotropic deformation of the lung lobes. The three-dimensional (3D) lung geometry is reconstructed from the end-expiration 3D CT scan datasets of humans with lung cancer. The lung is modeled as a poro-elastic medium with anisotropic elastic property (non-linear Young's modulus) obtained from inverse lung elastography of 4D CT scans for the same patients. The predicted results include the 3D anisotropic lung deformation along with the airflow pattern inside the lungs. The effect is also presented of anisotropic elasticity on both the spatio-temporal volumetric lung displacement and the regional lung hysteresis. PMID:22356987
NASA Astrophysics Data System (ADS)
Heczko, Oleg; Seiner, Hanuš; Sedlák, Petr; Kopeček, Jaromír; Kopecký, Vít; Landa, Michal
2013-02-01
Resonant ultrasound spectroscopy (RUS) was used to investigate the changes of elastic properties induced by magnetic field in magnetic shape memory alloys Ni-Mn-Ga and Co-Ni-Al. In contrast to large magneto-elastic response of Ni2MnGa austenite, there is only very weak response of Co-Ni-Al. This indicates that the austenite phase of Ni-Mn-Ga can have a privileged position and this may be a reason for the existence of magnetic shape memory effect. In contrast to austenite, the magneto-elastic response in Ni-Mn-Ga martensite is very small with large damping due to existence of twin boundaries. The measurement showed that RUS can be a powerful method to probe magneto-elastic properties of shape memory alloys.
A method for measuring non-linear elastic properties of thermal barrier coatings
Johnson, C.A.; Ruud, J.A.; Kaya, A.C.; deLorenzi, H.G.
1995-06-01
Accurate characterization of the elastic properties of thermal barrier coatings (TBC`s) is important for failure prediction. Thermally sprayed coatings often exhibit anisotropic and nonlinear elastic properties due to the coating microstructure that results from the thermal spray process. A method was developed for determining the elastic behavior of TBC`s on substrates by measuring the in-plane modulus as a function of residual coating stress. The in-plane modulus was determined by resonant frequency measurement, and the residual stress was measured from the substrate curvature. The residual stress was varied both by increasing the temperature of the TBC and substrate and by applying compressive plastic strain to the metal substrate. The stress-strain behavior of the TBC was derived from the data for modulus versus residual stress, and significant nonlinear elastic behavior was observed.
Shyam, Amit; Lara-Curzio, Edgar
2009-01-01
Mechanical properties of plasma sprayed ceramic coatings are extremely important to engine design. However, the determination of these properties is often difficult because of the unique and complicated microstructure of the coatings. In this presentation the determination of the elastic constants of plasma sprayed Yttria stabilized Zirconia thermal barrier coatings using resonant ultrasound spectroscopy will be described along with an analysis that enables the determination of the elastic constants as a function of temperature and coating direction. In this work, results on the following issues will be discussed: 1) the elastic anisotropy of thermal barrier coatings, which is associated with coating failure modes; 2) sintering effects on coating compliance comparing with thermal behavior, which is important to coating performance on engineering structures, such as turbine engines; 3) coating elastic modulus at high temperatures close to the service condition, which provides insights of coating mechanical behavior in both fundamental and practical studies.
Acoustic and elastic properties of Sn(2)P(2)S(6) crystals.
Mys, O; Martynyuk-Lototska, I; Grabar, A; Vlokh, R
2009-07-01
We present the results concerned with acoustic and elastic properties of Sn(2)P(2)S(6) crystals. The complete matrices of elastic stiffness and compliance coefficients are determined in both the crystallographic coordinate system and the system associated with eigenvectors of the elastic stiffness tensor. The acoustic slowness surfaces are constructed and the propagation and polarization directions of the slowest acoustic waves promising for acousto-optic interactions are determined on this basis. The acoustic obliquity angle and the deviation of polarization of the acoustic waves from purely transverse or longitudinal states are quantitatively analysed. PMID:21828470
Static and dynamic elastic properties of rocks from the Canadian Shield
King, M.S.
1983-01-01
As part of a number of research studies in the Canadian Shield associated with the stability of underground mine openings, seismic reflection surveys, and the proposed use of a tunnel-boring machine (TBM) for developing mine headings, a long-term laboratory rock mechanics program has been conducted to determine the static and dynamic elastic properties of samples of igneous and metamorphic rocks from the Canadian Shield. This paper reports the results of 174 measurements of static elastic modulus and 152 measurements of uniaxial compressive strength for these rocks as a function of dynamic elastic modulus. 20 references, 5 figures.
NASA Astrophysics Data System (ADS)
Henann, David; Wang, Yuhao
Surface energy is an important factor in the deformation of fluids but is typically a minimal or negligible effect in solids. However, when a solid is soft and its characteristic dimension is small, forces due to surface energy can become important and induce significant elastic deformation. The interplay between surface energy and elasticity can lead to interesting elasto-capillary phenomena. We have developed a finite-element formulation for problems involving these effects in both 2D and 3D settings and will demonstrate the simulation capability by examining two elasto-capillary problems. (1) The Rayleigh-Plateau instability in an elastic material - In a fluid, this instability causes fluid jets to break up into droplets; however, as shown in recent experiments (Mora et al., PRL, 2010), break-up is prohibited in an elastic material, resulting in a stable undulatory configuration. (2) The effect of fluid-filled droplet inclusions on a soft solid - When the matrix material is stiff, the presence of fluid-filled inclusions leads to a more compliant composite material; however, recent experiments (Style, et al., Nature Physics, 2014) have shown that when the matrix material is more compliant, the presence of droplets leads to stiffening. In this talk, we will show that our simulation capability predicts all experimentally observed phenomena and provides a straightforward route for describing nonlinear aspects of elasto-capillarity, which are difficult to address via analytics.
NASA Astrophysics Data System (ADS)
Singh, Mayanglambam Suheshkumar; Jiang, Huabei
2016-02-01
We report our study that shows selection in operating frequency of US-transducer used for boundary detection of PA-signals, which result due to the contrast in elastic property distribution ( E ( r → ) ) in sample material other than that of optical absorption coefficient (μa). Studies were carried out, experimentally, in tissue-mimicking Agar phantoms employing acoustic resolution photoacoustic microscopy (AR-PAM) system as an imaging unit. In the experiments, various transducers having different operating frequencies, ranging from 1MHz to 50MHz, were employed for studying frequency response of the photoacoustic signals. The study shows that, for detecting photoacoustic signals due to the contrast in elastic property, ultrasound transducer with higher operating frequency (˜50MHz) is demanded.
Ab-initio study of electronic structure and elastic properties of ZrC
NASA Astrophysics Data System (ADS)
Mund, H. S.; Ahuja, B. L.
2016-05-01
The electronic and elastic properties of ZrC have been investigated using the linear combination of atomic orbitals method within the framework of density functional theory. Different exchange-correlation functionals are taken into account within generalized gradient approximation. We have computed energy bands, density of states, elastic constants, bulk modulus, shear modulus, Young's modulus, Poisson's ratio, lattice parameters and pressure derivative of the bulk modulus by calculating ground state energy of the rock salt structure type ZrC.
Seiner, Hanuš; Sedlák, Petr; Bodnárová, Lucie; Drahokoupil, Jan; Kopecký, Vít; Kopeček, Jaromír; Landa, Michal; Heczko, Oleg
2013-10-23
The evolution of elastic properties with temperature and magnetic field was studied in two differently heat-treated single crystals of the Ni-Mn-Ga magnetic shape memory alloy using resonant ultrasound spectroscopy. Quenching and slow furnace cooling were used to obtain different densities of antiphase boundaries. We found that the crystals exhibited pronounced differences in the c' elastic coefficient and related shear damping in high-temperature ferromagnetic phases (austenite and premartensite). The difference can be ascribed to the formation of fine magnetic domain patterns and pinning of the magnetic domain walls on antiphase boundaries in the material with a high density of antiphase boundaries due to quenching. The fine domain pattern arising from mutual interactions between antiphase boundaries and ferromagnetic domain walls effectively reduces the magnetocrystalline anisotropy and amplifies the contribution of magnetostriction to the elastic response of the material. As a result, the anomalous elastic softening prior to martensite transformation is significantly enhanced in the quenched sample. Thus, for any comparison of experimental data and theoretical calculations the microstructural changes induced by specific heat treatment must be taken into account. PMID:24067443
The Elastic and Vibrational Properties of Co to 120 GPa
Crowhurst, J; Goncharov, A F; Zaug, J M
2003-11-21
Impulsive stimulated light scattering and Raman spectroscopy measurements have been made on hcp cobalt to a static pressure of 120 GPa. This is the highest static pressure to date at which acoustic velocities have been directly measured. We find that at pressures above 60 GPa the shear elastic modulus and the Raman frequency of the E{sub 2g} transverse optical phonon exhibit a departure from a linear dependence on density. We relate this behavior to a collapse of the magnetic moment under pressure that has been predicted theoretically, but until now not observed experimentally.
García-Arribas, Alfredo; Gutiérrez, Jon; Kurlyandskaya, Galina V; Barandiarán, José M; Svalov, Andrey; Fernández, Eduardo; Lasheras, Andoni; de Cos, David; Bravo-Imaz, Iñaki
2014-01-01
The outstanding properties of selected soft magnetic materials make them successful candidates for building high performance sensors. In this paper we present our recent work regarding different sensing technologies based on the coupling of the magnetic properties of soft magnetic materials with their electric or elastic properties. In first place we report the influence on the magneto-impedance response of the thickness of Permalloy films in multilayer-sandwiched structures. An impedance change of 270% was found in the best conditions upon the application of magnetic field, with a low field sensitivity of 140%/Oe. Second, the magneto-elastic resonance of amorphous ribbons is used to demonstrate the possibility of sensitively measuring the viscosity of fluids, aimed to develop an on-line and real-time sensor capable of assessing the state of degradation of lubricant oils in machinery. A novel analysis method is shown to sensitively reveal the changes of the damping parameter of the magnetoelastic oscillations at the resonance as a function of the oil viscosity. Finally, the properties and performance of magneto-electric laminated composites of amorphous magnetic ribbons and piezoelectric polymer films are investigated, demonstrating magnetic field detection capabilities below 2.7 nT. PMID:24776934
García-Arribas, Alfredo; Gutiérrez, Jon; Kurlyandskaya, Galina V.; Barandiarán, José M.; Svalov, Andrey; Fernández, Eduardo; Lasheras, Andoni; de Cos, David; Bravo-Imaz, Iñaki
2014-01-01
The outstanding properties of selected soft magnetic materials make them successful candidates for building high performance sensors. In this paper we present our recent work regarding different sensing technologies based on the coupling of the magnetic properties of soft magnetic materials with their electric or elastic properties. In first place we report the influence on the magneto-impedance response of the thickness of Permalloy films in multilayer-sandwiched structures. An impedance change of 270% was found in the best conditions upon the application of magnetic field, with a low field sensitivity of 140%/Oe. Second, the magneto-elastic resonance of amorphous ribbons is used to demonstrate the possibility of sensitively measuring the viscosity of fluids, aimed to develop an on-line and real-time sensor capable of assessing the state of degradation of lubricant oils in machinery. A novel analysis method is shown to sensitively reveal the changes of the damping parameter of the magnetoelastic oscillations at the resonance as a function of the oil viscosity. Finally, the properties and performance of magneto-electric laminated composites of amorphous magnetic ribbons and piezoelectric polymer films are investigated, demonstrating magnetic field detection capabilities below 2.7 nT. PMID:24776934
Deficiencies in numerical models of anisotropic nonlinearly elastic materials.
Ní Annaidh, A; Destrade, M; Gilchrist, M D; Murphy, J G
2013-08-01
Incompressible nonlinearly hyperelastic materials are rarely simulated in finite element numerical experiments as being perfectly incompressible because of the numerical difficulties associated with globally satisfying this constraint. Most commercial finite element packages therefore assume that the material is slightly compressible. It is then further assumed that the corresponding strain-energy function can be decomposed additively into volumetric and deviatoric parts. We show that this decomposition is not physically realistic, especially for anisotropic materials, which are of particular interest for simulating the mechanical response of biological soft tissue. The most striking illustration of the shortcoming is that with this decomposition, an anisotropic cube under hydrostatic tension deforms into another cube instead of a hexahedron with non-parallel faces. Furthermore, commercial numerical codes require the specification of a 'compressibility parameter' (or 'penalty factor'), which arises naturally from the flawed additive decomposition of the strain-energy function. This parameter is often linked to a 'bulk modulus', although this notion makes no sense for anisotropic solids; we show that it is essentially an arbitrary parameter and that infinitesimal changes to it result in significant changes in the predicted stress response. This is illustrated with numerical simulations for biaxial tension experiments of arteries, where the magnitude of the stress response is found to change by several orders of magnitude when infinitesimal changes in 'Poisson's ratio' close to the perfect incompressibility limit of 1/2 are made. PMID:23011411
From Process Modeling to Elastic Property Prediction for Long-Fiber Injection-Molded Thermoplastics
Nguyen, Ba Nghiep; Kunc, Vlastimil; Frame, Barbara J.; Phelps, Jay; Tucker III, Charles L.; Bapanapalli, Satish K.; Holbery, James D.; Smith, Mark T.
2007-09-13
This paper presents an experimental-modeling approach to predict the elastic properties of long-fiber injection-molded thermoplastics (LFTs). The approach accounts for fiber length and orientation distributions in LFTs. LFT samples were injection-molded for the study, and fiber length and orientation distributions were measured at different locations for use in the computation of the composite properties. The current fiber orientation model was assessed to determine its capability to predict fiber orientation in LFTs. Predicted fiber orientations for the studied LFT samples were also used in the calculation of the elastic properties of these samples, and the predicted overall moduli were then compared with the experimental results. The elastic property prediction was based on the Eshelby-Mori-Tanaka method combined with the orientation averaging technique. The predictions reasonably agree with the experimental LFT data
Dimpled elastic sheets: a new class of non-porous negative Poisson’s ratio materials
Javid, Farhad; Smith-Roberge, Evelyne; Innes, Matthew C.; Shanian, Ali; Weaver, James C.; Bertoldi, Katia
2015-01-01
In this study, we report a novel periodic material with negative Poisson’s ratio (also called auxetic materials) fabricated by denting spherical dimples in an elastic flat sheet. While previously reported auxetic materials are either porous or comprise at least two phases, the material proposed here is non-porous and made of a homogeneous elastic sheet. Importantly, the auxetic behavior is induced by a novel mechanism which exploits the out-of-plane deformation of the spherical dimples. Through a combination of experiments and numerical analyses, we demonstrate the robustness of the proposed concept, paving the way for developing a new class of auxetic materials that significantly expand their design space and possible applications. PMID:26671169
Dimpled elastic sheets: a new class of non-porous negative Poisson's ratio materials.
Javid, Farhad; Smith-Roberge, Evelyne; Innes, Matthew C; Shanian, Ali; Weaver, James C; Bertoldi, Katia
2015-01-01
In this study, we report a novel periodic material with negative Poisson's ratio (also called auxetic materials) fabricated by denting spherical dimples in an elastic flat sheet. While previously reported auxetic materials are either porous or comprise at least two phases, the material proposed here is non-porous and made of a homogeneous elastic sheet. Importantly, the auxetic behavior is induced by a novel mechanism which exploits the out-of-plane deformation of the spherical dimples. Through a combination of experiments and numerical analyses, we demonstrate the robustness of the proposed concept, paving the way for developing a new class of auxetic materials that significantly expand their design space and possible applications. PMID:26671169
Dimpled elastic sheets: a new class of non-porous negative Poisson’s ratio materials
NASA Astrophysics Data System (ADS)
Javid, Farhad; Smith-Roberge, Evelyne; Innes, Matthew C.; Shanian, Ali; Weaver, James C.; Bertoldi, Katia
2015-12-01
In this study, we report a novel periodic material with negative Poisson’s ratio (also called auxetic materials) fabricated by denting spherical dimples in an elastic flat sheet. While previously reported auxetic materials are either porous or comprise at least two phases, the material proposed here is non-porous and made of a homogeneous elastic sheet. Importantly, the auxetic behavior is induced by a novel mechanism which exploits the out-of-plane deformation of the spherical dimples. Through a combination of experiments and numerical analyses, we demonstrate the robustness of the proposed concept, paving the way for developing a new class of auxetic materials that significantly expand their design space and possible applications.
Stress analysis of thermally affected rotating nanoshafts with varying material properties
NASA Astrophysics Data System (ADS)
Kiani, Keivan
2016-04-01
Based on the surface elasticity theory of Gurtin-Murdoch, thermo-elastic fields within rotating nanoshafts with varying material properties subjected to a thermal field are explicitly examined. Accounting for the surface energy effect, the nonclassical boundary conditions are enforced in the cases of fixed-free and free-free conditions. The effects of variation of material properties, temperature of the environment, angular velocity, and radius of the outer radius on the radial displacement, hoop and radial stresses are investigated. In all performed studies, the role of the surface effect on the thermo-elastic field of the nanostructure is methodically discussed.
Theoretical Investigations on the Elastic and Thermodynamic Properties of Rhenium Phosphide
NASA Astrophysics Data System (ADS)
Wei, Qun; Yan, Haiyan; Zhu, Xuanmin; Lin, Zhengzhe; Yao, Ronghui
2016-01-01
Structural, mechanical, and electronic properties of orthorhombic rhenium phosphide (Re2P) are systematically investigated by using first principles calculations. The elastic constants and anisotropy of elastic properties are obtained. The metallic character of Re2P is demonstrated by density of state calculations. The quasi-harmonic Debye model is applied to the study of the thermodynamic properties. The thermal expansion, heat capacities, and Grüneisen parameter on the temperature and pressure have been determined as a function of temperature and pressure in the pressure range from 0 to 100 GPa and the temperature range from 0 to 1600 K.
Elastic properties of swollen polyelectrolyte gels in aqueous salt solutions.
Sasaki, Shigeo
2006-03-01
The elastic relaxation responding to a uniaxially stretched poly(acrylic acid) rodlike gel in the aqueous NaCl solution was investigated. The relaxation elucidated the shear (mu) and bulk (K) moduli and the frictional coefficients (sigma) of the fully ionized gel at pH above 9 as functions of the degree of swelling, which was controlled by the NaCl concentration (C(S)) of the solution. Two gels, cross-linked chains of which consist of 500 (GelA500) and 50 (GelA50) monomeric units, were examined to investigate the effect of the chain length on the elastic behavior. The moduli of GelA500 increased with swelling at C(S) below 100 mM and decreased at C(S) above it. The mu values of both gels can be characterized by the power function of gel diameter, d as mu proportional, variantd(beta). The beta values being -1 at C(S) above 100 mM transitionally changed to 1.2 at C(S) about 100 mM. That is, the dimensionality of space for the chains to distribute, n(dim) [= (beta+5)/(beta+2) according to the conventional theory [Sasaki et al., J. Chem. Phys. 102, 5694 (1995)
Bulk elastic properties of chicken embryos during somitogenesis
2010-01-01
We present measurements of the bulk Young's moduli of early chick embryos at Hamburger-Hamilton stage 10. Using a micropipette probe with a force constant k ~0.025 N/m, we applied a known force in the plane of the embryo in the anterior-posterior direction and imaged the resulting tissue displacements. We used a two-dimensional finite-element simulation method to model the embryo as four concentric elliptical elastic regions with dimensions matching the embryo's morphology. By correlating the measured tissue displacements to the displacements calculated from the in-plane force and the model, we obtained the approximate short time linear-elastic Young's moduli: 2.4 ± 0.1 kPa for the midline structures (notocord, neural tube, and somites), 1.3 ± 0.1 kPa for the intermediate nearly acellular region between the somites and area pellucida, 2.1 ± 0.1 kPa for the area pellucida, and 11.9 ± 0.8 kPa for the area opaca. PMID:20353597
NASA Astrophysics Data System (ADS)
Hoffmeister, Brentley Keith
1995-01-01
This thesis seeks to contribute to a better understanding of the physics of interaction of ultrasonic waves with inhomogeneous and anisotropic media, one example of which is the human heart. The clinical success of echocardiography has generated a considerable interest in the development of ultrasonic techniques to measure the elastic properties of heart tissue. It is hypothesized that the elastic properties of myocardium are influenced by the interstitial content and organization of collagen. Collagen, which is the main component of tendon, interconnects the muscle cells of the heart to form locally unidirectional myofibers. This thesis therefore employs ultrasonic techniques to characterize the linear elastic properties of both heart and tendon. The linear elastic properties of tissues possessing a unidirectional arrangement of fibers may be described in terms of five independent elastic stiffness coefficients. Three of these coefficients were determined for formalin fixed specimens of bovine Achilles tendon and human myocardium by measuring the velocity of longitudinal mode ultrasonic pulses as a function of angle of propagation relative to the fiber axis of the tissue. The remaining two coefficients were determined by measuring the velocity of transverse mode ultrasonic waves through these tissues. To overcome technical difficulties associated with the extremely high attenuation of transverse mode waves at low megahertz frequencies, a novel measurement system was developed based on the sampled continuous wave technique. Results of these measurements were used to assess the influence of interstitial collagen, and to model the mechanical properties of heart wall.
Determining the elastic properties of aptamer-ricin single molecule multiple pathways
Technology Transfer Automated Retrieval System (TEKTRAN)
Ricin and an anti-ricin aptamer showed three stable binding conformations with their special chemomechanical properties. The elastic properties of the ricin-aptamer single-molecule interactions were investigated by the dynamic force spectroscopy (DFS). The worm-like-chain model and Hook’s law were ...
The influence of phonon anharmonicity on thermal and elastic properties of neptunium
NASA Astrophysics Data System (ADS)
Filanovich, A.; Povzner, A.
2013-06-01
A self-consistent thermodynamic model describing the thermal and elastic properties of α- and β-phases of neptunium was developed. The presence of strong phonon anharmonicity of Np is established. The obtained results are in good agreement with the experimental data and enable to predict the Np properties in wide temperature range.
NASA Astrophysics Data System (ADS)
Maccabi, A.; Taylor, Z.; Bajwa, N.; Mallen-St. Clair, J.; St. John, M.; Sung, S.; Grundfest, W.; Saddik, G.
2016-02-01
Tissue hardness, often quantified in terms of elasticity, is an important differentiating criterion for pathological identity and is extensively used by surgeons for tumor localization. Delineation of malignant regions from benign regions is typically performed by visual inspection and palpation. Although practical, this method is highly subjective and does not provide quantitative metrics. We have previously reported on Vibro-Acoustography (VA) for tumor delineation. VA is unique in that it uses the specific, non-linear properties of tumor tissue in response to an amplitude modulated ultrasound beam to generate spatially resolved, high contrast maps of tissue. Although the lateral and axial resolutions (sub-millimeter and sub-centimeter, respectively) of VA have been extensively characterized, the relationship between static stiffness assessment (palpation) and dynamic stiffness characterization (VA) has not been explicitly established. Here we perform a correlative exploration of the static and dynamic properties of tissue-mimicking phantoms, specifically elasticity, using VA and a muscle motor system. Muscle motor systems, commonly used to probe the mechanical properties of materials, provide absolute, quantitative point measurements of the elastic modulus, analogous to Young's modulus, of a target. For phantoms of varying percent-by-weight concentrations, parallel VA and muscle motor studies conducted on 18 phantoms reveal a negative correlation (p < - 0.85) between mean signal amplitude levels observed with VA and calculated elastic modulus values from force vs. indentation depth curves. Comparison of these elasticity measurements may provide additional information to improve tissue modeling, system characterization, as well as offer valuable insights for in vivo applications, specifically surgical extirpation of tumors.
Bulk electronic, elastic, structural, and dielectric properties of the Weyl semimetal TaAs
NASA Astrophysics Data System (ADS)
Buckeridge, J.; Jevdokimovs, D.; Catlow, C. R. A.; Sokol, A. A.
2016-03-01
We present results of electronic structure calculations of the bulk properties of the Weyl semimetal TaAs. The emergence of Weyl (massless) fermions in TaAs, due to its electronic band structure, is indicative of a new state of matter in the condensed phase that is of great interest for fundamental physics and possibly new applications. Many of the physical properties of the material, however, are unknown. We have calculated the structural parameters, dielectric function, elastic constants, phonon dispersion, electronic band structure, and Born effective charges using density functional theory within the generalized gradient approximation, including spin-orbit coupling where necessary. Our results provide essential information on the material; and our calculations agree well with the relatively small number of experimental data available. Moreover, we have determined the relative stability of the ground state body-centered tetragonal phase with respect to other common binary phases as a function of pressure at the athermal limit, predicting a transition to the CsCl cubic structure at 23.3 GPa. Finally, we have determined the band structure using an unbiased hybrid density functional that includes 25% exact exchange, in order to refine the previously determined positions in k space of the Weyl points.
Role of non-covalent interactions in the production of visco-elastic material from zein
Technology Transfer Automated Retrieval System (TEKTRAN)
Zein has been used in the production of a wide variety of materials during the last century. One of the more intriguing developments in zein utilization has been the discovery that zein can be made to form a visco-elastic dough for bread production. Although significant research has been conducted t...
Satellite material contaminant optical properties
NASA Technical Reports Server (NTRS)
Wood, B. E.; Bertrand, W. T.; Seiber, B. L.; Kiech, E. L.; Falco, P. M.; Holt, J. D.
1990-01-01
The Air Force Wright Research and Development Center and the Arnold Engineering Development Center are continuing a program for measuring optical effects of satellite material outgassing products on cryo-optic surfaces. Presented here are infrared (4000 to 700 cm(-1)) transmittance data for contaminant films condensed on a 77 K geranium window. From the transmittance data, the contaminant film refractive and absorptive indices (n, k) were derived using an analytical thin-film interference model with a nonlinear least-squares algorithm. To date 19 materials have been studied with the optical contents determined for 13 of those. The materials include adhesives, paints, composites, films, and lubricants. This program is continuing and properties for other materials will be available in the future.
NASA Astrophysics Data System (ADS)
Stackhouse, S.; Liu, T.
2014-12-01
Seismic studies report the presence of regions below Africa and the Pacific, which exhibit shear-wave velocity reductions of about 3 percent. These so-called large low shear velocity provinces (LLSVPs), cover approximately half of the core-mantle boundary, making them an important interface between the core and lowermost mantle. The fact that they exhibit different seismic properties indicates that they are different from surrounding mantle, either in temperature and/or composition. The reported sharpness of the boundaries of large low shear velocity provinces suggests that they are at least in part compositional anomalies. One potential explanation is that they comprise the relics of subducted slabs, and thus have mid-ocean ridge basalt (MORB). The high temperature and pressure seismic properties of MORB phases, needed to compare with seismic observations, are unknown. Here we report the high temperature and pressure elastic properties of several aluminous phases, which comprise about 20 percent of MORB material. In particular, we have looked at MgAl2O4, NaMg2Al5SiO12, and KMg2Al5SiO12, with the calcium ferrite (CF) and new aluminous (NAL) structure. These should provide further constraints to aid the interpretation of seismic observations, contributing to the thermal vs compositional anomaly debate.
Elastic properties of protein functionalized nanoporous polymer films
Charles T. Black; Wang, Haoyu; Akcora, Pinar
2015-12-16
Retaining the conformational structure and bioactivity of immobilized proteins is important for biosensor designs and drug delivery systems. Confined environments often lead to changes in conformation and functions of proteins. In this study, lysozyme is chemically tethered into nanopores of polystyrene thin films, and submicron pores in poly(methyl methacrylate) films are functionalized with streptavidin. Nanoindentation experiments show that stiffness of streptavidin increases with decreasing submicron pore sizes. Lysozymes in polystyrene nanopores are found to behave stiffer than the submicron pore sizes and still retain their specific bioactivity relative to the proteins on flat surfaces. Lastly, our results show that proteinmore » functionalized ordered nanoporous polystyrene/poly(methyl methacrylate) films present heterogeneous elasticity and can be used to study interactions between free proteins and designed surfaces.« less
Elastic Properties of Lysozyme Confined in Nanoporous Polymer Films
NASA Astrophysics Data System (ADS)
Wang, Haoyu; Akcora, Pinar
Retaining the conformational structure and bioactivity of immobilized proteins is important for biosensor designs and drug delivery systems. It is known that confined media provide a protective environment to the encapsulated proteins and prevent diffusion of the denaturant. In this study, different types of proteins (streptavidin, lysozyme and fibrinogen) were chemically attached into the nanopores of poly(methyl methacrylate) thin films. Heterogeneous flat surfaces with varying cylinder pore sizes (10-50 nm) were used to confine proteins of different sizes and shapes. Stiffness of protein functionalized nanopores was measured in nanoindentation experiments. Our results showed that streptavidin behaved more stiffly when pore dimension changed from micron to nanosize. Further, it was found that lysozyme confined within nanopores showed higher specific bioactivity than proteins on flat surfaces. These results on surface elasticity and protein activity may help in understanding protein interactions with surfaces of different topologies and chemistry.
Elastic Properties of Protein Functionalized Nanoporous Polymer Films.
Wang, Haoyu; Black, Charles T; Akcora, Pinar
2016-01-12
Retaining the conformational structure and bioactivity of immobilized proteins is important for biosensor designs and drug delivery systems. Confined environments often lead to changes in conformation and functions of proteins. In this study, lysozyme is chemically tethered into nanopores of polystyrene thin films, and submicron pores in poly(methyl methacrylate) films are functionalized with streptavidin. Nanoindentation experiments show that stiffness of streptavidin increases with decreasing submicron pore sizes. Lysozymes in polystyrene nanopores are found to behave stiffer than the submicron pore sizes and still retain their specific bioactivity relative to the proteins on flat surfaces. Our results show that protein functionalized ordered nanoporous polystyrene/poly(methyl methacrylate) films present heterogeneous elasticity and can be used to study interactions between free proteins and designed surfaces. PMID:26672623
Elastic properties of protein functionalized nanoporous polymer films
Charles T. Black; Wang, Haoyu; Akcora, Pinar
2015-12-16
Retaining the conformational structure and bioactivity of immobilized proteins is important for biosensor designs and drug delivery systems. Confined environments often lead to changes in conformation and functions of proteins. In this study, lysozyme is chemically tethered into nanopores of polystyrene thin films, and submicron pores in poly(methyl methacrylate) films are functionalized with streptavidin. Nanoindentation experiments show that stiffness of streptavidin increases with decreasing submicron pore sizes. Lysozymes in polystyrene nanopores are found to behave stiffer than the submicron pore sizes and still retain their specific bioactivity relative to the proteins on flat surfaces. Lastly, our results show that protein functionalized ordered nanoporous polystyrene/poly(methyl methacrylate) films present heterogeneous elasticity and can be used to study interactions between free proteins and designed surfaces.
Nonlinear Anisotropic Elastic Properties of the Canine Aorta
Vaishnav, Ramesh N.; Young, John T.; Janicki, Joseph S.; Patel, Dali J.
1972-01-01
A nonlinear theory of large elastic deformations of the aortic tissue has been developed. The wall tissue has been considered to be incompressible and curvilinearly orthotropic. The strain energy density function for the tissue is expressed as a polynomial in the circumferential and longitudinal Green-St. Venant strains. Limiting application to states of strains wherein the geometric axes are the principal axes and truncating the energy expression to include terms with highest degrees 2, 3, and 4, three expressions with 3, 7, and 12 constitutive constants are obtained. Results of application of these expressions to data from three series of in vitro and in vivo experiments involving 31 dogs have been presented. Whereas all the three expressions are found to be applicable to various degrees, the third-degree expression for the strain energy density function with seven constitutive constants is particularly recommended for general use. PMID:5044576
Elastic properties of graphene flakes: Boundary effects and lattice vibrations
NASA Astrophysics Data System (ADS)
Bera, S.; Arnold, A.; Evers, F.; Narayanan, R.; Wölfle, P.
2010-11-01
We present a phenomenological theory together with explicit calculations of the electronic ground-state energy, the surface contribution, and the elastic constants (“Lamé parameters,” i.e., Poisson ratio, Young’s modulus) of graphene flakes on the level of the density-functional theory employing different standard functionals. We observe that the Lamé parameters in small flakes can differ from the bulk values by 30% for hydrogenated zigzag edges. The change results from the edge of the flake that compresses the interior. When including the vibrational zero-point motion, we detect a decrease in the bending rigidity, κ , by ˜26% . The vibrational frequencies flow with growing N due to the release of the edge-induced compression. We calculate the corresponding Grüneisen parameters and find good agreement with previous authors.
Elastically driven cooperative response of a molecular material impacted by a laser pulse
NASA Astrophysics Data System (ADS)
Bertoni, Roman; Lorenc, Maciej; Cailleau, Hervé; Tissot, Antoine; Laisney, Jérôme; Boillot, Marie-Laure; Stoleriu, Laurentiu; Stancu, Alexandru; Enachescu, Cristian; Collet, Eric
2016-06-01
Photoinduced phase transformations occur when a laser pulse impacts a material, thereby transforming its electronic and/or structural orders, consequently affecting the functionalities. The transient nature of photoinduced states has thus far severely limited the scope of applications. It is of paramount importance to explore whether structural feedback during the solid deformation has the capacity to amplify and stabilize photoinduced transformations. Contrary to coherent optical phonons, which have long been under scrutiny, coherently propagating cell deformations over acoustic timescales have not been explored to a similar degree, particularly with respect to cooperative elastic interactions. Herein we demonstrate, experimentally and theoretically, a self-amplified responsiveness in a spin-crossover material during its delayed volume expansion. The cooperative response at the material scale prevails above a threshold excitation, significantly extending the lifetime of photoinduced states. Such elastically driven cooperativity triggered by a light pulse offers an efficient route towards the generation and stabilization of photoinduced phases in many volume-changing materials.
Gap Formations in Simulations of Shpb Tests on Elastic Materials Soft in Shear
NASA Astrophysics Data System (ADS)
Raftenberg, M. N.; Scheidler, M. J.
2009-12-01
The LS-DYNA code was applied to split Hopkinson pressure bar tests on a material at least two orders of magnitude stiffer in dilatation than in shear. Two constitutive models were applied, linear elasticity and a compressible form of Mooney-Rivlin elasticity. The latter was fitted to data from ballistic gelatin. The incident and transmission bars were aluminum. The nominal strain rate was 2500/s. Gaps appeared at the interfaces between the specimen and both bars. Unloading of the specimen and bars accompanied these gaps. The input-velocity rise time was varied to observe pulse shaping effects. Mesh sensitivity and contact-parameter sensitivity studies were performed.
NASA Astrophysics Data System (ADS)
Liu, B.; Arsenlis, A.; Aubry, S.
2016-06-01
Driven by the growing interest in numerical simulations of dislocation–interface interactions in general crystalline materials with elastic anisotropy, we develop algorithms for the integration of interface tractions needed to couple dislocation dynamics with a finite element or boundary element solver. The dislocation stress fields in elastically anisotropic media are made analytically accessible through the spherical harmonics expansion of the derivative of Green’s function, and analytical expressions for the forces on interface elements are derived by analytically integrating the spherical harmonics series recursively. Compared with numerical integration by Gaussian quadrature, the newly developed analytical algorithm for interface traction integration is highly beneficial in terms of both computation precision and speed.
Soft-materials elastic and shear moduli measurement using piezoelectric cantilevers
NASA Astrophysics Data System (ADS)
Markidou, Anna; Shih, Wan Y.; Shih, Wei-Heng
2005-06-01
We have developed a soft-material elastic modulus and shear modulus sensor using piezoelectric cantilevers. A piezoelectric cantilever is consisted of a highly piezoelectric layer, e.g., lead-zirconate-titanate bonded to a nonpiezoelectric layer, e.g., stainless steel. Applying an electric field in the thickness direction causes a piezoelectric cantilever to bend, generating an axial displacement or force. When a piezoelectric cantilever is in contact with an object, this electric field-generated axial displacement is reduced due to the resistance by the object. With a proper design of the piezoelectric cantilever's geometry, its axial displacements with and without contacting the object could be accurately measured. From these measurements the elastic modulus of the object can be deduced. In this study, we tailored the piezoelectric cantilevers for measuring the elastic and shear moduli of tissue-like soft materials with forces in the submilli Newton to milliNewton range. Elastic moduli and shear moduli of soft materials were measured using piezoelectric cantilevers with a straight tip and an L-shaped tip, respectively. Using gelatin and commercial rubber material as model soft tissues, we showed that a piezoelectric cantilever 1.5-2cm long could measure the elastic modulus and the shear modulus of a small soft material sample (1-3mm wide) in the small strain range (<1%). For samples 5mm high, the resultant compressive (shear) strains were less than 0.5% (1%). The measurements were validated by (1) comparing the measured Young's modulus of the commercial rubber sample with its known value and (2) by measuring both the Young's modulus and shear modulus on the samples and confirming the thus deduced Poisson's ratios with the separately measured Poisson's ratios.
Thermal stress fracture in elastic-brittle materials
NASA Technical Reports Server (NTRS)
Emery, A. F.
1980-01-01
The reported investigation shows that the assessment of the possibility of the thermal fracture of brittle materials depends upon an accurate evaluation of the thermal stresses and the determination of the resulting stress intensity factors. The stress intensity factors can be calculated in a variety of ways ranging from the very precise to approximate, but only for a limited number of geometries. The main difficulty is related to the determination of the thermal stress field because of its unusual character and its dependence upon boundary conditions at points far from the region of thermal activity. Examination of a number of examples suggests that the best visualization of the thermal stresses and any associated fracture can be made by considering the problem to be the combination of thermal and isothermal problems or by considering that the prime effect of the temperature is in the generation of thermal strains and that the thermal stresses are simply the result of the region trying to accommodate these strains.
Saturation effects on the joint elastic-dielectric properties of carbonates
NASA Astrophysics Data System (ADS)
Han, Tongcheng; Clennell, Michael Ben; Pervukhina, Marina; Josh, Matthew
2016-06-01
We used a common microstructural model to investigate the cross-property relations between elastic wave velocities and dielectric permittivity in carbonate rocks. A unified model based on validated self-consistent effective medium theory was used to quantify the effects of porosity and water saturation on both elastic properties (compressional and shear wave velocities) and electromagnetic properties (dielectric permittivity). The results of the forward models are presented as a series of cross-plots covering a wide range of porosities and water saturations and for microstructures that correspond to different predominant aspect ratios. It was found that dielectric permittivity correlated approximately linearly with elastic wave velocity at each saturation stage, with slopes varying gradually from positive at low saturation conditions to negative at higher saturations. The differing sensitivities of the elastic and dielectric rock properties to changes in porosity, pore morphology and water saturation can be used to reduce uncertainty in subsurface fluid saturation estimation when co-located sonic and dielectric surveys are available. The joint approach is useful for cross-validation of rock physics models for analysing pore structure and saturation effects on elastic and dielectric responses.
Non-contacting transfer of elastic energy into explosive simulants for dynamic property estimation
Greeney, Nathan S.; Strovink, Kurt M.; Scales, John A.; Jessop, Andrew M.; Stuart Bolton, J.; Watson, Christopher C.; Adams, Douglas E.
2014-05-21
Non-contacting acoustical methods can be used to extract various material properties of liquid or solid samples without disturbing the sample. These methods are useful even in the lab since they do not involve coupling anything to the sample, which might change its properties. A forteriori, when dealing with potentially dangerous materials, non-contacting methods may be the only safe solutions to mechanical characterization. Here, we show examples of using laser ultrasound to remotely insonify and monitor the elastic properties of several granular explosive simulants. The relatively short near-infrared laser pulse length (a few hundred nanoseconds) provides a broad-band thermoelastic source of ultrasound; we intentionally stay in the thermoelastic regime to avoid damaging the material. Then, we use a scanning laser Doppler vibrometer to measure the ultrasonic response of the sample. LDV technology is well established and very sensitive at ultrasonic frequencies; atomic level motions can be measured with modest averaging. The resulting impulse response of the explosive simulant can be analyzed to determine decay rates and wave speeds, with stiffer samples showing faster wave speeds and lower decay rates. On the other hand, at the low-frequency end of the acoustic spectrum, we use an electronically phased array to couple into a freely suspended sample's normal modes. This allows us to gently heat up the sample (3 °C in just under 5 min, as shown with a thermal IR camera). In addition to the practical interest in making the sample more chemically visible through heat, these two measurements (low-frequency resonant excitation vs high-frequency wave propagation) bracket the frequency range of acoustic non-destructive evaluation methods available.
Nihei, K.T.; Nakagawa, S.; Reverdy, F.; Meyer, L.R.; Duranti, L.; Ball, G.
2010-12-15
Sediments undergoing compaction typically exhibit transversely isotropic (TI) elastic properties. We present a new experimental apparatus, the phased array compaction cell, for measuring the TI elastic properties of clay-rich sediments during compaction. This apparatus uses matched sets of P- and S-wave ultrasonic transducers located along the sides of the sample and an ultrasonic P-wave phased array source, together with a miniature P-wave receiver on the top and bottom ends of the sample. The phased array measurements are used to form plane P-waves that provide estimates of the phase velocities over a range of angles. From these measurements, the five TI elastic constants can be recovered as the sediment is compacted, without the need for sample unloading, recoring, or reorienting. This paper provides descriptions of the apparatus, the data processing, and an application demonstrating recovery of the evolving TI properties of a compacting marine sediment sample.
Anisotropic elastic properties of MB (M = Cr, Mo, W) monoborides: a first-principles investigation
NASA Astrophysics Data System (ADS)
Li, Run-Yue; Duan, Yong-Hua
2016-04-01
First principles calculations were performed to systematically investigate structure properties, phase stability and mechanical properties of MB (M = Cr, Mo, W) monoborides in orthorhombic and tetragonal structures. The results of equilibrium structures are in good agreement with other available theoretical and experimental data. The elastic properties, including bulk modulus B, shear modulus G, Young's modulus E and Poisson's ratio ν were calculated by the Voigt-Reuss-Hill approximation. All considered monoborides are mechanically stable. The results of elastic anisotropies show that elastic anisotropy of orthorhombic structure is larger than that of tetragonal structure. Moreover, the minimum thermal conductivities were also estimated using the Cahill's model, and the results indicate that the minimum thermal conductivities show a dependence on directions.
First principle study of elastic and thermodynamic properties of FeB4 under high pressure
NASA Astrophysics Data System (ADS)
Zhang, Xinyu; Qin, Jiaqian; Ning, Jinliang; Sun, Xiaowei; Li, Xinting; Ma, Mingzhen; Liu, Riping
2013-11-01
The elastic properties, elastic anisotropy, and thermodynamic properties of the lately synthesized orthorhombic FeB4 at high pressures are investigated using first-principles density functional calculations. The calculated equilibrium parameters are in good agreement with the available experimental and theoretical data. The obtained normalized volume dependence of high pressure is consistent with the previous experimental data investigated using high-pressure synchrotron x-ray diffraction. The complete elastic tensors and crystal anisotropies of the FeB4 are also determined in the pressure range of 0-100 GPa. By the elastic stability criteria and vibrational frequencies, it is predicted that the orthorhombic FeB4 is stable up to 100 GPa. In addition, the calculated B/G ratio reveals that FeB4 possesses brittle nature in the range of pressure from 0 to 100 GPa. The calculated elastic anisotropic factors suggest that FeB4 is elastically anisotropic. By using quasi-harmonic Debye model, the compressibility, bulk modulus, the coefficient of thermal expansion, the heat capacity, and the Grüneisen parameter of FeB4 are successfully obtained in the present work.
‘Granular Elasticity’ and the loss of elastic stability in granular materials
P. W. Humrickhouse
2009-07-01
A recently proposed hyperelastic model for granular materials, called "granular elasticity", identifies a yield angle as a result of thermodynamic instability. GE gives yield angles that are smaller than those found in real materials; a generalization of the theory is considered here that includes dependence on the third strain invariant. This generalization proves unsuccessful, as it gives smaller, not larger, yield angles. Fully convex hyperelastic models are identified as a point for future investigation.
First-principles study of structural, elastic and thermodynamic properties of AuIn2
NASA Astrophysics Data System (ADS)
Wu, Hai Ying; Chen, Ya Hong; Deng, Chen Rong; Yin, Peng Fei; Cao, Hong
2015-12-01
The structural, elastic and thermodynamic properties of AuIn2 in the CaF2 structure under pressure have been investigated using ab initio plane wave pseudopotential method within the generalized gradient approximation. The calculated structural parameters and equation of state are in excellent agreement with the available experimental and theoretical results. The elastic constants of AuIn2 at ambient condition are calculated, and the bulk modulus obtained from these calculated elastic constants agrees well with the experimental data. The pressure dependence of the elastic constants, bulk modulus, shear modulus and Young’s modulus has also been investigated. The Debye temperature presents a slight increase with pressure. AuIn2 exhibits ductibility and low hardness characteristics, the ductibility increases while the hardness decreases with the increasing of pressure. The pressure effect on the heat capacity and thermal expansion coefficient for AuIn2 is much larger.
Theoretical Predictions for High-Pressure Elastic, Mechanical, and Phonon Properties of SiGe Alloy
NASA Astrophysics Data System (ADS)
Güler, M.; Güler, E.
2016-04-01
Elastic, mechanical, and phonon properties of zinc blende (ZB)-type SiGe ordered alloy were theoretically investigated in detail under pressures up to 12 GPa. Unlike earlier theoretical calculations of literature, a Stillinger-Weber-type interatomic potential was applied to this work for the first time with geometry optimization calculations. Pressure dependence of typical cubic elastic constants, bulk, shear and Young moduli, elastic wave velocities, Kleinman parameter, elastic anisotropy factor, phonon dispersion, as well as density of states of SiGe alloy were calculated and compared with other results when available. In general, our results for the above considered quantities of SiGe alloy are satisfactory and compare well the former theoretical data of alloy.
Numerical Calculation of Nonlinear Seismic Pulse Propagation in a Hysteretic Elastic Material
NASA Astrophysics Data System (ADS)
Kosik, Dan
2007-04-01
The stress-strain relation for materials such as soil and sand exhibit hysteretic elastic behavior and are modeled using the Preisach-Mayergoyz method for a numerical calculation of a propagating seismic pulse. The source pulse is taken to be the result of pressure applied to the inner surface of a cylindrical cavity in order to simulate a two dimensional dynamite source. The nonlinear differential equation of motion that is solved includes traditional nonlinear elasticity terms appropriate to materials with atomic elasticity and the dominant anelastic terms appropriate to consolidated materials that exhibit hysteretic elastic behavior. For parameters characteristic of sand at the Earth's surface, a comparison of nonlinear to linear seismic pulse propagation gives a nonlinear pulse with a much larger amplitude and slower propagation speed than a corresponding linear pulse. These results have important implications for the detailed behavior of strong seismic waves moving in soft sediments, their dominant frequencies, amplitudes, and methods by which they may be attenuated will depend on getting the detailed pulse structure right.
Ganeshraj, C.; Santhosh, P. N.
2014-10-14
We report first-principles study of structural, electronic, vibrational, dielectric, and elastic properties of Ba₂YTaO₆, a pinning material in high temperature superconductors (HTS), by using density functional theory. By using different exchange-correlation potentials, the accuracy of the calculated lattice constants of Ba₂YTaO₆ has been achieved with GGA-RPBE, since many important physical quantities crucially depend on change in volume. We have calculated the electronic band structure dispersion, total and partial density of states to study the band gap origin and found that Ba₂YTaO₆ is an insulator with a direct band gap of 3.50 eV. From Mulliken population and charge density studies, we conclude that Ba₂YTaO₆ have a mixed ionic-covalent character. Moreover, the vibrational properties, born effective charges, and the dielectric permittivity tensor have been calculated using linear response method. Vibrational spectrum determined through our calculations agrees well with the observed Raman spectrum, and allows assignment of symmetry labels to modes. We perform a detailed analysis of the contribution of the various infrared-active modes to the static dielectric constant to explain its anisotropy, while electronic dielectric tensor of Ba₂YTaO₆ is nearly isotropic, and found that static dielectric constant is in good agreement with experimental value. The six independent elastic constants were calculated and found that tetragonal Ba₂YTaO₆ is mechanically stable. Other elastic properties, including bulk modulus, shear modulus, Young's modulus, Poisson's ratio, and elastic anisotropy ratios are also investigated and found that Poisson's ratio and Young's modulus of Ba₂YTaO₆ are similar to that of other pinning materials in HTS.
A model for compression-weakening materials and the elastic fields due to contractile cells
NASA Astrophysics Data System (ADS)
Rosakis, Phoebus; Notbohm, Jacob; Ravichandran, Guruswami
2015-12-01
We construct a homogeneous, nonlinear elastic constitutive law that models aspects of the mechanical behavior of inhomogeneous fibrin networks. Fibers in such networks buckle when in compression. We model this as a loss of stiffness in compression in the stress-strain relations of the homogeneous constitutive model. Problems that model a contracting biological cell in a finite matrix are solved. It is found that matrix displacements and stresses induced by cell contraction decay slower (with distance from the cell) in a compression weakening material than linear elasticity would predict. This points toward a mechanism for long-range cell mechanosensing. In contrast, an expanding cell would induce displacements that decay faster than in a linear elastic matrix.
An elastic-perfectly plastic flow model for finite element analysis of perforated materials
Jones, D.P.; Gordon, J.L.; Hutula, D.N.; Banas, D.; Newman, J.B.
1999-02-01
This paper describes the formulation of an elastic-perfectly plastic flow theory applicable to equivalent solid [EQS] modeling of perforated materials. An equilateral triangular array of circular penetrations is considered. The usual assumptions regarding geometry and loading conditions applicable to the development of elastic constants for EQS modeling of perforated plates are considered to apply here. An elastic-perfectly plastic [EPP] EQS model is developed for a collapse surface that includes fourth-order stress terms. The fourth order yield function has been shown to be appropriate for plates with a triangular array of circular holes. A complete flow model is formulated using the consistent tangent modulus approach based on the fourth order yield function.
Detecting Damage in Composite Material Using Nonlinear Elastic Wave Spectroscopy Methods
NASA Astrophysics Data System (ADS)
Meo, Michele; Polimeno, Umberto; Zumpano, Giuseppe
2008-05-01
Modern aerospace structures make increasing use of fibre reinforced plastic composites, due to their high specific mechanical properties. However, due to their brittleness, low velocity impact can cause delaminations beneath the surface, while the surface may appear to be undamaged upon visual inspection. Such damage is called barely visible impact damage (BVID). Such internal damages lead to significant reduction in local strengths and ultimately could lead to catastrophic failures. It is therefore important to detect and monitor damages in high loaded composite components to receive an early warning for a well timed maintenance of the aircraft. Non-linear ultrasonic spectroscopy methods are promising damage detection and material characterization tools. In this paper, two different non-linear elastic wave spectroscopy (NEWS) methods are presented: single mode nonlinear resonance ultrasound (NRUS) and nonlinear wave modulation technique (NWMS). The NEWS methods were applied to detect delamination damage due to low velocity impact (<12 J) on various composite plates. The results showed that the proposed methodology appear to be highly sensitive to the presence of damage with very promising future NDT and structural health monitoring applications.
Ortiz, Aurélie U; Boutin, Anne; Fuchs, Alain H; Coudert, François-Xavier
2012-11-01
We performed ab initio calculations of the elastic constants of five flexible metal-organic frameworks (MOFs): MIL-53(Al), MIL-53(Ga), MIL-47, and the square and lozenge structures of DMOF-1. Tensorial analysis of the elastic constants reveals a highly anisotropic elastic behavior, some deformation directions exhibiting very low Young's modulus and shear modulus. This anisotropy can reach a 400:1 ratio between the most rigid and weakest directions, in stark contrast to the case of nonflexible MOFs such as MOF-5 and ZIF-8. In addition, we show that flexible MOFs can display extremely large negative linear compressibility. These results uncover the microscopic roots of stimuli-induced structural transitions in flexible MOFs, by linking the local elastic behavior of the material and its multistability. PMID:23215398
Material properties of oxide superconductors
Phillips, J.C.
1996-12-31
The differences between the old (inter-) metallic superconductors and the new oxide superconductors are not limited to the much higher values of {Tc} attainable in the latter. There are many pervasive differences caused directly by oxide chemistry, quasi-perovskite local coordination configurations, and layered metal-semiconductor-metal{prime}-semiconductor-structures. When these differences are ignored, for instance in theoretical models which make effective medium approximations, many experiments appear to present anomalous results. These anomalies largely disappear when account is taken of the real materials properties of the cuprates and other new oxide superconductors, for instance in theoretical models which treat transport as a partially percolative process. This percolative process directly reflects the fact that the highest values of {Tc}, as well as the most anomalous normal-state transport properties, occur in materials vicinal to a metal-insulator transition. As the metallic and insulating regions alternate even in single-crystal samples, effective medium models, and most effective-medium parameters, lose their significance. Examples of attempts to measure microscopic properties illustrate the importance of filamentary effects on both normal-state and superconductive properties.
EQUIVALENCE BETWEEN SHORT-TIME BIPHASIC AND INCOMPRESSIBLE ELASTIC MATERIAL RESPONSES
Ateshian, Gerard A.; Ellis, Benjamin J.; Weiss, Jeffrey A.
2009-01-01
Porous-permeable tissues have often been modeled using porous media theories such as the biphasic theory. This study examines the equivalence of the short-time biphasic and incompressible elastic responses for arbitrary deformations and constitutive relations from first principles. This equivalence is illustrated in problems of unconfined compression of a disk, and of articular contact under finite deformation, using two different constitutive relations for the solid matrix of cartilage, one of which accounts for the large disparity observed between the tensile and compressive moduli in this tissue. Demonstrating this equivalence under general conditions provides a rationale for using available finite element codes for incompressible elastic materials as a practical substitute for biphasic analyses, so long as only the short-time biphasic response is sought. In practice, an incompressible elastic analysis is representative of a biphasic analysis over the short-term response δt≪Δ2/‖C4‖||K||, where Δ is a characteristic dimension, C4 is the elasticity tensor and K is the hydraulic permeability tensor of the solid matrix. Certain notes of caution are provided with regard to implementation issues, particularly when finite element formulations of incompressible elasticity employ an uncoupled strain energy function consisting of additive deviatoric and volumetric components. PMID:17536908
Dong, Bing; Zhou, Xiao-Lin E-mail: lkworld@126.com; Chang, Jing; Liu, Ke E-mail: lkworld@126.com
2014-08-07
The structural and elastic properties of RuN{sub 2} were investigated through the first-principles calculation using generalized gradient approximation (GGA) and local density approximation (LDA) within the plane-wave pseudopotential density functional theory. The obtained equilibrium structure and mechanical properties are in excellent agreement with other theoretical results. Then we compared the elastic modulus of RuN{sub 2} with several other isomorphic noble metal nitrides. Results show that RuN{sub 2} can nearly rival with OsN{sub 2} and IrN{sub 2}, which indicate RuN{sub 2} is a potentially ultra-incompressible and hard material. By the elastic stability criteria, it is predicted that RuN{sub 2} is stable in our calculations (0–100 GPa). The calculated B/G ratios indicate that RuN{sub 2} possesses brittle nature at 0 GPa and when the pressure increases to 13.4 GPa (for LDA) or 20.8 GPa (for GGA), it begins to prone to ductility. Through the quasi-harmonic Debye model, we also investigated the thermodynamic properties of RuN{sub 2}.
Sato, Akihiro; Pennec, Yan; Shingne, Nitin; Thurn-Albrecht, Thomas; Knoll, Wolfgang; Steinhart, Martin; Djafari-Rouhani, Bahram; Fytas, George
2010-06-22
Anodic aluminum oxide (AAO) containing arrays of aligned cylindrical nanopores infiltrated with polymers is a well-defined model system for the study of hypersound propagation in polymer nanocomposites. Hypersonic phononic properties of AAO/polymer nanocomposites such as phonon localization and anisotropic sound propagation can be tailored by adjusting elastic contrast and density contrast between the components. Changes in density and elastic properties of the component located in the nanopores induced by phase transitions allow reversible modification of the phononic band structure and mode switching. As example in case, the crystallization and melting of poly(vinylidene difluoride) inside AAO was investigated. PMID:20509665
Rotational Seismic AVO For Estimation Of Gas Hydrate Elastic Rock Properties
NASA Astrophysics Data System (ADS)
Barak, O.; Dvorkin, J. P.; Ronen, S.
2013-12-01
Gas hydrates represent a potential future energy resource. They are a form of water crystal that have a specific structure, and which are stabilized by the inclusion of methane gas molecules. The presence of a gas hydrate saturated layer can be seen in some seismic data as a result of the high impedance contrast between the gas hydrate layer and the underlying sediment. Several rock physics models exist to describe the way the gas hydrate is included in the host rock. To determine the best model, knowledge of several material parameters is required. Some of the material parameters can be estimated by observing the seismic AVO curve of the hydrate layer, which indicates P-wave reflectivity. However, the P-wave reflectivity is not very sensitive to the shear stiffness of the medium, which is one of the crucial parameters that helps clearly separate gas hydrates from their typical sedimentary surrounding. In this study we propose constructing converted-wave AVO curves from rotational seismic data acquired on the sea-bottom. Rotation data is a proxy for the reflected shear-wave energy. Since the shear-wave reflectivity is more dependent on the rigidity (or shear) modulus, we expect to see a greater sensitivity of the converted-wave AVO to spatial and temporal variations in rock-physics properties of the gas hydrate layer. Utilizing the rock-physics models and data from a well log near the Blake Outer Ridge where a hydrate layer is present, we constructed a 1.5D medium with effective elastic properties. We then use forward modeling to predict how a change in rock physics parameters may affect the AVO curve of the rotational-motion components recorded by rotation sensors, and compare the response to AVO obtained from the hydrophone component. We also compare the effect of layer thinning on the standard P-wave AVO versus on the rotational AVO. We conclude that rotational AVO is more sensitive to a change in the rock-physics parameters than is the conventional P-wave AVO
Elastic and Thermal Properties of Silicon Compounds from First-Principles Calculations
NASA Astrophysics Data System (ADS)
Hou, Haijun; Zhu, H. J.; Cheng, W. H.; Xie, L. H.
2016-07-01
The structural and elastic properties of V-Si (V3Si, VSi2, V5Si3, and V6Si5) compounds are studied by using first-principles method. The calculated equilibrium lattice parameters and formation enthalpy are in good agreement with the available experimental data and other theoretical results. The calculated results indicate that the V-Si compounds are mechanically stable. Elastic properties including bulk modulus, shear modulus, Young's modulus, and Poisson's ratio are also obtained. The elastic anisotropies of V-Si compounds are investigated via the three-dimensional (3D) figures of directional dependences of reciprocals of Young's modulus. Finally, based on the quasi-harmonic Debye model, the internal energy, Helmholtz free energy, entropy, heat capacity, thermal expansion coefficient, Grüneisen parameter, and Debye temperature of V-Si compounds have been calculated.
Structural, elastic and thermodynamic properties of Mo3Si and Mo3Ge
NASA Astrophysics Data System (ADS)
Zhong, Sheng-Yi; Chen, Zhe; Wang, Mingliang; Chen, Dong
2016-01-01
The structural, elastic and thermodynamic properties of the cubic Mo3Si and Mo3Ge intermetallics were investigated using density functional theory within the local density approximation (LDA) and generalized gradient approximation (GGA) methods. The results showed that the structural and elastic properties (i.e., elastic constants, bulk modulus, shear modulus and Young's modulus) derived by the GGA method were in good agreement with the available experimental and theoretical values. Using the quasi-harmonic Debye model, the variations of the Debye temperature, heat capacity and coefficient of thermal expansion under pressure ranging from 0 to 25 GPa and at temperature ranging from 0 to 1800 K were obtained and analyzed for both compounds.
Korsa, Radim; Lukes, Jaroslav; Sepitka, Josef; Mares, Tomas
2015-08-01
Knowledge of the anisotropic elastic properties of osteon and osteonal lamellae provides a better understanding of various pathophysiological conditions, such as aging, osteoporosis, osteoarthritis, and other degenerative diseases. For this reason, it is important to investigate and understand the elasticity of cortical bone. We created a bidirectional micromechanical model based on inverse homogenization for predicting the elastic properties of osteon and osteonal lamellae of cortical bone. The shape, the dimensions, and the curvature of osteon and osteonal lamellae are described by appropriately chosen curvilinear coordinate systems, so that the model operates close to the real morphology of these bone components. The model was used to calculate nine orthotropic elastic constants of osteonal lamellae. The input values have the elastic properties of a single osteon. We also expressed the dependence of the elastic properties of the lamellae on the angle of orientation. To validate the model, we performed nanoindentation tests on several osteonal lamellae. We compared the experimental results with the calculated results, and there was good agreement between them. The inverted model was used to calculate the elastic properties of a single osteon, where the input values are the elastic constants of osteonal lamellae. These calculations reveal that the model can be used in both directions of homogenization, i.e., direct homogenization and also inverse homogenization. The model described here can provide either the unknown elastic properties of a single lamella from the known elastic properties at the level of a single osteon, or the unknown elastic properties of a single osteon from the known elastic properties at the level of a single lamella. PMID:25901781
Elastic properties of porous structural ceramics produced by plasma-spraying
Wanner, A.
1998-12-31
This study focuses on the relationship between porosity and elastic stiffness of structural ceramic materials produced by plasma-spraying. Mg-Al-spinel was chosen as a model material and studied in as-sprayed condition as well as upon annealing to increasingly higher temperatures up to 1650 C. The detailed analysis of the stiffness and mass density evolution offers a deep insight into the initial microstructural state of the material and into the morphological changes that occur upon heat treatment.
Temperature-dependent elastic properties of Ti1-xAlxN alloys
NASA Astrophysics Data System (ADS)
Shulumba, Nina; Hellman, Olle; Rogström, Lina; Raza, Zamaan; Tasnádi, Ferenc; Abrikosov, Igor A.; Odén, Magnus
2015-12-01
Ti1-xAlxN is a technologically important alloy that undergoes a process of high temperature age-hardening that is strongly influenced by its elastic properties. We have performed first principles calculations of the elastic constants and anisotropy using the symmetry imposed force constant temperature dependent effective potential method, which include lattice vibrations and therefore the effects of temperature, including thermal expansion and intrinsic anharmonicity. These are compared with in situ high temperature x-ray diffraction measurements of the lattice parameter. We show that anharmonic effects are crucial to the recovery of finite temperature elasticity. The effects of thermal expansion and intrinsic anharmonicity on the elastic constants are of the same order, and cannot be considered separately. Furthermore, the effect of thermal expansion on elastic constants is such that the volume change induced by zero point motion has a significant effect. For TiAlN, the elastic constants soften non-uniformly with temperature: C11 decreases substantially when the temperature increases for all compositions, resulting in an increased anisotropy. These findings suggest that an increased Al content and annealing at higher temperatures will result in a harder alloy.
Fritsch, Andreas; Hellmich, Christian
2007-02-21
Bone materials are characterized by an astonishing variability and diversity. Still, because of 'architectural constraints' due to once chosen material constituents and their physical interaction, the fundamental hierarchical organization or basic building plans of bone materials remain largely unchanged during biological evolution. Such universal patterns of microstructural organization govern the mechanical interaction of the elementary components of bone (hydroxyapatite, collagen, water; with directly measurable tissue-independent elastic properties), which are here quantified through a multiscale homogenization scheme delivering effective elastic properties of bone materials: at a scale of 10nm, long cylindrical collagen molecules, attached to each other at their ends by approximately 1.5nm long crosslinks and hosting intermolecular water inbetween, form a contiguous matrix called wet collagen. At a scale of several hundred nanometers, wet collagen and mineral crystal agglomerations interpenetrate each other, forming the mineralized fibril. At a scale of 5-10microm, the extracellular solid bone matrix is represented as collagen fibril inclusions embedded in a foam of largely disordered (extrafibrillar) mineral crystals. At a scale above the ultrastructure, where lacunae are embedded in extracellular bone matrix, the extravascular bone material is observed. Model estimates predicted from tissue-specific composition data gained from a multitude of chemical and physical tests agree remarkably well with corresponding acoustic stiffness experiments across a variety of cortical and trabecular, extracellular and extravascular materials. Besides from reconciling the well-documented, seemingly opposed concepts of 'mineral-reinforced collagen matrix' and 'collagen-reinforced mineral matrix' for bone ultrastructure, this approach opens new possibilities in the exploitation of computer tomographic data for nano-to-macro mechanics of bone organs. PMID:17074362
Determination of the elastic properties of tomato fruit cells with an atomic force microscope.
Zdunek, Artur; Kurenda, Andrzej
2013-01-01
Since the mechanical properties of single cells together with the intercellular adhesive properties determine the macro-mechanical properties of plants, a method for evaluation of the cell elastic properties is needed to help explanation of the behavior of fruits and vegetables in handling and food processing. For this purpose, indentation of tomato mesocarp cells with an atomic force microscope was used. The Young's modulus of a cell using the Hertz and Sneddon models, and stiffness were calculated from force-indentation curves. Use of two probes of distinct radius of curvature (20 nm and 10,000 nm) showed that the measured elastic properties were significantly affected by tip geometry. The Young's modulus was about 100 kPa ± 35 kPa and 20 kPa ± 14 kPa for the sharper tip and a bead tip, respectively. Moreover, large variability regarding elastic properties (>100%) among cells sampled from the same region in the fruit was observed. We showed that AFM provides the possibility of combining nano-mechanical properties with topography imaging, which could be very useful for the study of structure-related properties of fruits and vegetables at the cellular and sub-cellular scale. PMID:24030683
Food material properties and early hominin processing techniques.
Zink, Katherine D; Lieberman, Daniel E; Lucas, Peter W
2014-12-01
Although early Homo is hypothesized to have used tools more than australopiths to process foods prior to consumption, it is unknown how much the food processing techniques they used altered the material properties of foods, and therefore the masticatory forces they generated, and how well they were able to comminute foods. This study presents experimental data on changes to food material properties caused by mechanical tenderization (pounding with a stone tool) and cooking (dry roasting) of two foods likely to have been important components of the hominin diet: meat and tubers. Mechanical tenderization significantly decreased tuber toughness by 42%, but had no effect on meat toughness. Roasting significantly decreased several material properties of tubers correlated with masticatory effort including toughness (49%), fracture stress (28%) and elastic modulus (45%), but increased the toughness (77%), fracture stress (50%-222%), and elastic modulus of muscle fibers in meat (308%). Despite increasing many material properties of meat associated with higher masticatory forces, roasting also decreased measured energy loss by 28%, which likely makes it easier to chew. These results suggest that the use of food processing techniques by early Homo probably differed for meat and tubers, but together would have reduced masticatory effort, helping to relax selection to maintain large, robust faces and large, thickly enameled teeth. PMID:25439707
NASA Astrophysics Data System (ADS)
Rauter, N.; Lammering, R.
2015-04-01
In order to detect micro-structural damages accurately new methods are currently developed. A promising tool is the generation of higher harmonic wave modes caused by the nonlinear Lamb wave propagation in plate like structures. Due to the very small amplitudes a cumulative effect is used. To get a better overview of this inspection method numerical simulations are essential. Previous studies have developed the analytical description of this phenomenon which is based on the five-constant nonlinear elastic theory. The analytical solution has been approved by numerical simulations. In this work first the nonlinear cumulative wave propagation is simulated and analyzed considering micro-structural cracks in thin linear elastic isotropic plates. It is shown that there is a cumulative effect considering the S1-S2 mode pair. Furthermore the sensitivity of the relative acoustical nonlinearity parameter regarding those damages is validated. Furthermore, an influence of the crack size and orientation on the nonlinear wave propagation behavior is observed. In a second step the micro-structural cracks are replaced by a nonlinear material model. Instead of the five-constant nonlinear elastic theory hyperelastic material models that are implemented in commonly used FEM software are used to simulate the cumulative effect of the higher harmonic Lamb wave generation. The cumulative effect as well as the different nonlinear behavior of the S1-S2 and S2-S4 mode pairs are found by using these hyperelastic material models. It is shown that, both numerical simulations, which take into account micro-structural cracks on the one hand and nonlinear material on the other hand, lead to comparable results. Furthermore, in comparison to the five-constant nonlinear elastic theory the use of the well established hyperelastic material models like Neo-Hooke and Mooney-Rivlin are a suitable alternative to simulate the cumulative higher harmonic generation.
Elastic properties of SiC nanoscopic wires
NASA Astrophysics Data System (ADS)
Makeev, Maxim; Menon, Madhu; Srivastava, Deepak
2006-03-01
Mechanical properties of crystalline and amorphous SiC nanowires have been investigated using molecular dynamics simulations with the Tersoff bond-order interatomic potential. The crystalline and a-SiC nanowires of different diameters were studied under tension/compression, torsion, and bending. The bending and torsion rigidities are found to be strongly dependent on the wire size. This is unlike the Young's modulus computed from uniaxial loading curves. Atomistic relaxations effects near the thresholds of structural stability are investigated for the four employed load types. The mechanical properties of crystalline SiC nanowires are compared with a-SiC wires of the same radii.
Point defect modeling in materials: Coupling ab initio and elasticity approaches
NASA Astrophysics Data System (ADS)
Varvenne, Céline; Bruneval, Fabien; Marinica, Mihai-Cosmin; Clouet, Emmanuel
2013-10-01
Modeling point defects at an atomic scale requires careful treatment of the long-range atomic relaxations. This elastic field can strongly affect point defect properties calculated in atomistic simulations because of the finite size of the system under study. This is an important restriction for ab initio methods which are limited to a few hundred atoms. We propose an original approach coupling ab initio calculations and linear elasticity theory to obtain the properties of an isolated point defect for reduced supercell sizes. The reliability and benefit of our approach are demonstrated for three problematic cases: the self-interstitial in zirconium, clusters of self-interstitials in iron, and the neutral vacancy in silicon.
Sound Transmission Through Multi-Panel Structures Lined with Elastic Porous Materials
NASA Astrophysics Data System (ADS)
Bolton, J. S.; Shiau, N.-M.; Kang, Y. J.
1996-04-01
Theory and measurements related to sound transmission through double panels lined with elastic porous media are presented. The information has application to the design of noise control barriers and to the optimization of aircraft fuselage transmission loss, for example. The major difference between the work described here and earlier research in this field relates to the treatment of the porous material that is used to line the cavity between the two panels of the double panel structure. Here we have used the porous material theory proposed by Biot since it takes explicit account of all the wave types known to propagate in elastic porous materials. As a result, it is possible to use the theory presented here to calculate the transmission loss of lined double panels at arbitrary angles of incidence; results calculated over a range of incidence angles may then be combined to yield the random incidence transmission loss. In this paper, the equations governing wave propagation in an elastic porous material are first considered briefly and then the general forms for the stresses and displacements within the porous material are given. Those solutions are expressed in terms of a number of constants that can be determined by application of appropriate boundary conditions. The boundary conditions required to model double panels having linings that are either directly attached to the facing panels or separated?!from them by air gaps are presented and discussed. Measurements of the random incidence transmission loss of aluminium double-panel structures lined with polyurethane foam are presented and have been found to be in good agreement with theoretical predictions. Both the theoretical predictions and the measured results have shown that the method by which an elastic porous lining material is attached to the facing panels can have a profound influence on the transmission loss of the panel system. It has been found, for example, that treatments in which the lining material
NASA Astrophysics Data System (ADS)
Zhuang, Houlong; Chen, Mohan; Carter, Emily A.
2016-06-01
Magnesium-aluminum (Mg-Al) alloys are important metal alloys with a wide range of engineering applications. We investigate the elastic and thermodynamic properties of Mg, Al, and four stoichiometric Mg-Al compounds including Mg17Al12 , Mg13Al14 , and Mg23Al30 , and MgAl2 with orbital-free density-functional theory (OFDFT). We first calculate the lattice constants, zero-temperature formation energy, and independent elastic constants of these six materials and compare the results to those computed via Kohn-Sham DFT (KSDFT) benchmarks. We obtain excellent agreement between these two methods. Our calculated elastic constants of hexagonal close-packed Mg and face-centered-cubic Al are also consistent with available experimental data. We next compute their phonon spectra using the force constants extracted from the very fast OFDFT calculations, because such calculations are computationally challenging using KSDFT. This is especially the case for the Mg23Al30 compound, whose 3 ×3 ×3 supercell consists of 1431 atoms. We finally employ the quasiharmonic approximation to investigate temperature-dependent thermodynamic properties, including formation energies, heat capacities, and thermal expansion of the four Mg-Al intermetallic compounds. The calculated heat capacity and thermal expansion of both Mg and Al agree well with experimental data. We additionally find that Mg13Al14 and MgAl2 are both unstable, consistent with their absence from the equilibrium Mg-Al phase diagram. Our work demonstrates that OFDFT is an efficient and accurate quantum-mechanical computational tool for predicting elastic and thermodynamic properties of complicated Mg-Al alloys and also should be applicable to many other engineering alloys.
Elastic and Electronic Properties of CsI to 19 GPa: An Analog for Xe Deep Inside Planets
NASA Astrophysics Data System (ADS)
Arveson, S. M.; Jeanloz, R.
2015-12-01
The isoelectronic analogs xenon and CsI (i.e. having the same, noble-gas electronic configuration) both undergo a fundamental change in chemical bonding under pressure, becoming metallic by 135 (±20) GPa, the pressure at Earth's core-mantle boundary. Using Brillouin spectroscopy and diamond-anvil cells to 19 GPa at 290 K, we find that the electronic polarizability of CsI increases with pressure, quantifying the delocalization of electron charge density as the initially ionic salt is compressed toward the metallic state. Our results show a different trend from a previous measurement of refractive index under pressure and are consistent with the Herzfeld criterion that metallization is achieved when electron polarization is comparable to (or exceeds) inter-atomic distances. Our measurements of longitudinal elastic-wave velocity, VP, are in good accord with prior ultrasonic determinations below 1 GPa but suggest a slightly larger pressure derivative for the average shear modulus than previously thought. This conclusion is based on using Eulerian finite-strain descriptions of the equation of state and elastic moduli under pressure, and assumes that nonhydrostatic effects are unimportant. Our measurements were made on decompression as well as compression, using polycrystalline samples. Experimental measurements of changes in electronic and elastic properties under pressure can be used to validate and improve first-principles quantum mechanical calculations of bonding and other material properties, and can characterize the evolution of noble-gas toward chemically bonded systems at conditions deep inside planets.
NASA Astrophysics Data System (ADS)
Rogovoi, A. A.
2015-09-01
The dependence of a scalar measure of the structural changes occurring in a material under plastic deformation on a plastic strain measure and the dependence of a free energy measure on a structural change measure are constructed using experimental data that allow the expended plastic work to be divided into a latent part and a thermal part. The obtained dependences, kinematic relations, a constitutive equation, and a heat-conduction equation that satisfy the principles of thermodynamics and objectivity are used to construct a model of thermo-elastic-inelastic processes in the presence of finite deformations and structural changes in the material. The model is tested on the problem of temperature changes in the process of adiabatic elastic-plastic compression, which has experimental support.
NASA Astrophysics Data System (ADS)
Gascón, F.; Salazar, F.
1996-02-01
The displacement suffered by the points located on one face of a parallelepipedic specimen made of isotropic elastic material is studied, while subject to simple compression, which generates not only strain but also both a translational and a rotation effect. The displacement is measured by double-exposure speckle photography. The elastic constants of a material are computed by measuring the in-plane displacement of three points. The effect of the in-plane and out-of-plane displacements due to translation and rotation are analyzed. Extreme values for the tilt angle are estimated, as well as the maximum diameter of the read-out beam. The systematic uncertainty of the method is also studied. Both Young's modulus and Poisson's ratio are experimentally measured in aluminum.
NASA Astrophysics Data System (ADS)
Fraggedakis, Dimitris; Dimakopoulos, Yiannis; Tsamopoulos, John
2015-11-01
For several decades, Carbopol is assumed to be the ideal plastic material, exhibiting only yield phenomena without viscoelastic effects in yielded regions. Recently, it has been shown that when stresses do not overcome the yield criterion, it behaves as an ideal Hookean solid, Piau (2007). Also, experiments (Putz et al. (2006); Holenberg et al. (2012)) reveal phenomena which can be attributed only to elastic properties of the fluidized region, such as the appearance of the so-called ``negative wake,'' Harlen (2002), downstream the sphere and the loss of fore-aft symmetry of the yield surface around a sedimenting particle. Our study is based on the sedimentation of a confined particle in materials which exhibit elastoviscoplastic behavior and proves that Carbopol cannot be considered as the ideal plastic material anymore. Moreover, when elasticity comes into play, the derived stoppage criterion for a sedimenting sphere by Beris et al. (1985) and experimentally confirmed by Tabuteau et al. (2007) is not satisfied, as a complex stress field is developed around the particle and fluidization near the rigid surface is favored. The existence of the yield surface near the sphere enhances the formation of shear layers, which are responsible for the formation of the negative wake, irrespectively of the position of the confinement in relation to the sphere. GSRT Greece-Israel bilateral projects PHARMAMUDS #3163.
A 3D Orthotropic Strain-Rate Dependent Elastic Damage Material Model.
English, Shawn Allen
2014-09-01
A three dimensional orthotropic elastic constitutive model with continuum damage and cohesive based fracture is implemented for a general polymer matrix composite lamina. The formulation assumes the possibility of distributed (continuum) damage followed b y localized damage. The current damage activation functions are simply partially interactive quadratic strain criteria . However, the code structure allows for changes in the functions without extraordinary effort. The material model formulation, implementation, characterization and use cases are presented.
NASA Technical Reports Server (NTRS)
Trice, R.; Warren, N.; Anderson, O. L.
1974-01-01
Linear strain measurements are presented for two lunar basalts, 14310,82 and 71055,15 and one breccia, 15498,23 to 5 kb hydrostatic pressure. Compressional and shear acoustic velocities to 5 kb are also presented for the basalts, 14310,82 and 71055,15. These elastic properties, along with geological, seismological and rock mechanics considerations are consistent with a model of the structure of the Taurus-Littrow valley as follows, a thin surface regolith overlying a fractured mixture of basalt flows and ejecta material which in turn overlies a coherent breccia of highland ejecta debris.
NASA Astrophysics Data System (ADS)
Guo, San-Dong
2014-03-01
We investigate the electronic structures of {{\\rm{X}}_{3}}{\\rm{Sb}} (X = Li, K, Cs) by using Tran and Blaha's modified Becke and Johnson exchange potential. Calculated energy gaps are substantially better than previous first-principles results with respect to experimental values. The substantial improvement is achieved because the conduction bands are correctly calculated with the new exchange potential. The approach should be applicable to other similar materials. The elastic properties of {{\\rm{X}}_{3}}{\\rm{Sb}} (X = Li, K, Cs) are also studied in detail with the generalized gradient approximation such as bulk modulus, shear modulus, Young's modulus, Poisson's ratio, sound velocities, and Debye temperature.
Characterization of the Nonlinear Elastic Properties of Graphite/Epoxy Composites Using Ultrasound
NASA Technical Reports Server (NTRS)
Prosser, William H.; Green, Robert E., Jr.
1990-01-01
The normalized change in ultrasonic "natural" velocity as a function of stress and temperature was measured in a unidirectional laminate of T300/5208 graphite/epoxy composite using a pulsed phase locked loop ultrasonic interferometer. These measurements were used together with the linear (second order) elastic moduli to calculate some of the nonlinear (third order) moduli of this material.
NASA Astrophysics Data System (ADS)
Schmidt, Martin Jeffrey
The goal of this dissertation was to experimentally investigate the high rate and high pressure mechanical response of a mortar and concrete mix and use or develop a constitutive model able to describe the observed behavior. Triaxial compression tests at a strain rate of 10-6/ s, and for confining pressures ranging from 0 to 0.5 GPa were conducted. Dynamic tests in the range 60/s to about 160/s under both unconfined and confined conditions were conducted using the University of Florida's 7.62 cin diameter split Hopkinson pressure bar (SHPB). The data obtained in such tests allowed the quantification of the combined effects of confining pressure and strain rate on the deformation and strength of the materials. For mortar, dilatancy has been observed at high levels of the principal stress difference for both dynamic and quasi-static conditions. The unconfined dynamic compressive strengths are approximately double those of the quasi-static compressive strengths. Most of the confined SHPB mortar specimens showed very little damage post-test other than some chipping around the top edges, most likely due to localized tensile effects. For the concrete selected for this research. WES5000, quasi-static hydrostatic tests conducted up to a pressure of 0.5 GPa allowed for the accurate determination of the dependence of the bulk modulus on pressure and the correct estimation of the material's compaction properties when subjected to pressures in the range encountered in dynamic events. For confined quasi-static conditions, the material exhibited hardening behavior up to failure. Both compressibility and dilatancy regimes of the volumetric behavior were observed, the dilatancy threshold being highly dependent on the level of confinement. The unconfined dynamic strength is as high as 1.5 times the quasi-static strength, the material generally exhibiting far more cracking under similar loading conditions than was observed in mortar. The confined dynamic tests showed similar stress
Impact of Texture Heterogeneity on Elastic and Viscoelastic Properties of Carbonates
NASA Astrophysics Data System (ADS)
Sharma, Ravi
This thesis discusses the impacts of fabric heterogeneity, fluids and fluid saturations, effective pressures, and frequency of investigation on the elastic and viscoelastic properties of calcite-rich limestone and chalk formations. Carbonate reservoirs have been analyzed either with empirical relations and analogs from siliciclastic reservoirs or using simplistic models. However, under the varying parameters mentioned above, their seismic response can be very different. The primary reason is because these rocks of biochemical origins readily undergo textural changes and support heterogeneous distribution of fluid flow and elastic properties. Thus, many current rock physics models are unable to predict the time-lapse elastic response in these reservoirs. I have measured elastic properties of calcite rich rocks in the seismic frequency range of 2 to 2000 Hz and at the ultrasonic frequency of 800 kHz. The samples selected for this study represent the typical heterogeneities found in carbonate formations. These measurements covering a large frequency range provide an understanding of the dispersion and attenuation mechanisms during seismic wave propagation in the subsurface. I find that a heterogeneous formation shows significant velocity dispersion and attenuations when saturated with brine, and even more on saturation with CO2. I also show that the shear modulus of carbonate rocks changes significantly (from 8% for brine saturation to 70% for CO2 saturation) upon fluid saturation with polar fluids. I evaluated rock physics models, such as Gassmann's and with uniform and patchy fluid substitution, and Hashin-Shtrikman to predict saturated elastic properties in carbonates. Fluid sensitivity is directly related to the initial stiffness of the rock instead of porosity, as normally assumed. The Gassmann model can predict elastic properties for uniform saturations - mostly in homogenous rocks. Heterogeneous rocks, however, are better modeled using a patchy fluid saturation
Ramesh Babu, K; Vaitheeswaran, G
2014-06-11
We report a systematic first principles density functional study on the electronic structure, elastic and optical properties of nitrogen based solid hydrogen storage materials LiNH2, NaNH2, KNH2, and RbNH2. The ground state structural properties are calculated by using standard density functional theory, and also dispersion corrected density functional theory. We find that van der Waals interactions are dominant in LiNH2 whereas they are relatively weak in other alkali metal amides. The calculated elastic constants show that all the compounds are mechanically stable and LiNH2 is found to be a stiffer material among the alkali metal amides. The melting temperatures are calculated and follow the order RbNH2 < KNH2 < NaNH2 < LiNH2. The electronic band structure is calculated by using the Tran–Blaha modified Becke–Johnson potential and found that all the compounds are insulators, with a considerable band gap. The [NH2]− derived states completely dominate in the entire valence band region while the metal atom states occupy the conduction band. The calculated band structure is used to analyze the different interband optical transitions occurring between valence and conduction bands. Our calculations show that these materials have considerable optical anisotropy. PMID:25932472
NASA Astrophysics Data System (ADS)
Chang, Y.; Jacobsen, S. D.; Holl, C. M.; Bina, C. R.
2009-12-01
Elastic properties of solids are fundamentally important in Earth and materials science because they govern seismic wave propagation at the geophysical scale, but are controlled at the atomic scale by the nature of interatomic bonding. GHz-ultrasonic interferometry utilizes thin-film piezoelectric transducers driven by pulse modulated, microwave-range carrier frequencies at 0.5-2.0 GHz to measure sound wave travel times in sub-millimeter sized samples (Spetzler et al. 1993). Travel times are determined from the spacing of interference fringes produced by measuring the amplitude of overlapping echoes scanned in frequency (wavelength) from opposite polished faces of single crystals. The ultrasonic signals are near-optical in wavelength at 5-20 km/s in high-modulus materials, allowing study of samples as small as a few tens of micrometers in thickness, including micro-crystals loaded in diamond-anvil cells at high pressures and temperatures. Following Jacobsen et al. (2004), both longitudinal and shear-wave measurements are possible. Although relative changes in travel time on compression or heating are measured with standard deviation of about 0.02 nanoseconds out of 20-200 ns (depending on sample thickness), the absolute accuracy of ultrasonic measurements at standard conditions, required to anchor high P-T measurements, has been limited by our ability to measure sample thickness mechanically at STP, with only 1-2 micrometer accuracy out of 20-200 μm for typical samples. Thus, we have recently installed a commercial heterodyne optical interferometer to determine ultrasonic sample lengths at STP conditions. Using a double-pass laser interferometer we achieve λ/4 fundamental optical resolution with λ/128 (about 5 nm) system resolution through software-based interpolation. By adding real-time corrections for air temperature, humidity, and pressure applied to the laser wavelength, we achieve high accuracy with standard deviations of about 0.02 micrometers in the
NASA Astrophysics Data System (ADS)
Dutta, Parikshit; Urban, Matthew W.; Le Maître, Olivier P.; Greenleaf, James F.; Aquino, Wilkins
2015-07-01
The elastic and geometric properties of arteries have been long recognized as important predictors of cardiovascular disease. This work presents a robust technique for the noninvasive characterization of anisotropic elastic properties as well as thickness and diameter in arterial vessels. In our approach, guided waves are excited along arteries using the radiation force of ultrasound. Group velocity is used as the quantity of interest to reconstruct elastic and geometric features of the vessels. One of the main contributions of this work is a systematic approach based on sparse-grid collocation interpolation to construct surrogate models of arteries. These surrogate models are in turn used with direct-search optimization techniques to produce fast and accurate estimates of elastic properties, diameter, and thickness. One of the attractive features of the proposed approach is that once a surrogate model is built, it can be used for near real-time identification across many different types of arteries. We demonstrate the feasibility of the method using simulated and in vitro laboratory experiments on a silicon rubber tube and a porcine carotid artery. Our results show that using our proposed method, we can reliably identify the longitudinal modulus, thickness, and diameter of arteries. The circumferential modulus was found to have little influence in the group velocity, which renders the former quantity unidentifiable using the current experimental setting. Future work will consider the measurement of circumferential waves with the objective of improving the identifiability of the circumferential modulus.
Dutta, Parikshit; Urban, Matthew W; Le Maître, Olivier P; Greenleaf, James F; Aquino, Wilkins
2015-07-01
The elastic and geometric properties of arteries have been long recognized as important predictors of cardiovascular disease. This work presents a robust technique for the noninvasive characterization of anisotropic elastic properties as well as thickness and diameter in arterial vessels. In our approach, guided waves are excited along arteries using the radiation force of ultrasound. Group velocity is used as the quantity of interest to reconstruct elastic and geometric features of the vessels. One of the main contributions of this work is a systematic approach based on sparse-grid collocation interpolation to construct surrogate models of arteries. These surrogate models are in turn used with direct-search optimization techniques to produce fast and accurate estimates of elastic properties, diameter, and thickness. One of the attractive features of the proposed approach is that once a surrogate model is built, it can be used for near real-time identification across many different types of arteries. We demonstrate the feasibility of the method using simulated and in vitro laboratory experiments on a silicon rubber tube and a porcine carotid artery. Our results show that using our proposed method, we can reliably identify the longitudinal modulus, thickness, and diameter of arteries. The circumferential modulus was found to have little influence in the group velocity, which renders the former quantity unidentifiable using the current experimental setting. Future work will consider the measurement of circumferential waves with the objective of improving the identifiability of the circumferential modulus. PMID:26109582
A new model to simulate the elastic properties of mineralized collagen fibril.
Yuan, F.; Stock, S.R.; Haeffner, D.R.; Almer, J.D.; Dunand , D.C.; Brinson, K.
2011-01-01
Bone, because of its hierarchical composite structure, exhibits an excellent combination of stiffness and toughness, which is due substantially to the structural order and deformation at the smaller length scales. Here, we focus on the mineralized collagen fibril, consisting of hydroxyapatite plates with nanometric dimensions aligned within a protein matrix, and emphasize the relationship between the structure and elastic properties of a mineralized collagen fibril. We create two- and three-dimensional representative volume elements to represent the structure of the fibril and evaluate the importance of the parameters defining its structure and properties of the constituent mineral and collagen phase. Elastic stiffnesses are calculated by the finite element method and compared with experimental data obtained by synchrotron X-ray diffraction. The computational results match the experimental data well, and provide insight into the role of the phases and morphology on the elastic deformation characteristics. Also, the effects of water, imperfections in the mineral phase and mineral content outside the mineralized collagen fibril upon its elastic properties are discussed.
A new model to simulate the elastic properties of mineralized collagen fibril
Yuan, F.; Stock, S.R.; Haeffner, D.R.; Almer, J.D.; Dunand, D.C.; Brinson, L.C.
2012-05-02
Bone, because of its hierarchical composite structure, exhibits an excellent combination of stiffness and toughness, which is due substantially to the structural order and deformation at the smaller length scales. Here, we focus on the mineralized collagen fibril, consisting of hydroxyapatite plates with nanometric dimensions aligned within a protein matrix, and emphasize the relationship between the structure and elastic properties of a mineralized collagen fibril. We create two- and three-dimensional representative volume elements to represent the structure of the fibril and evaluate the importance of the parameters defining its structure and properties of the constituent mineral and collagen phase. Elastic stiffnesses are calculated by the finite element method and compared with experimental data obtained by synchrotron X-ray diffraction. The computational results match the experimental data well, and provide insight into the role of the phases and morphology on the elastic deformation characteristics. Also, the effects of water, imperfections in the mineral phase and mineral content outside the mineralized collagen fibril upon its elastic properties are discussed.
Dutta, Parikshit; Urban, Matthew W.; Le Maître, Olivier P.; Greenleaf, James F.; Aquino, Wilkins
2015-01-01
The elastic and geometric properties of arteries have been long recognized as important predictors of cardiovascular disease. This work presents a robust technique for the noninvasive characterization of anisotropic elastic properties as well as thickness and diameter in arterial vessels. In our approach, guided waves are excited along arteries using the radiation force of ultrasound. Group velocity is used as the quantity of interest to reconstruct elastic and geometric features of the vessels. One of the main contributions of this work is a systematic approach based on sparse-grid collocation interpolation to construct surrogate models of arteries. These surrogate models are in turn used with direct-search optimization techniques to produce fast and accurate estimates of elastic properties, diameter, and thickness. One of the attractive features of the proposed approach is that once a surrogate model is built, it can be used for near real-time identification across many different types of arteries. We demonstrate the feasibility of the method using simulated and in vitro laboratory experiments on a silicon rubber tube and a porcine carotid artery. Our results show that using our proposed method, we can reliably identify the longitudinal modulus, thickness, and diameter of arteries. The circumferential modulus was found to have little influence in the group velocity, which renders the former quantity unidentifiable using the current experimental setting. Future work will consider the measurement of circumferential waves with the objective of improving the identifiability of the circumferential modulus. PMID:26109582
Elastic properties of methane-propane mixed gas hydrate under high pressure
NASA Astrophysics Data System (ADS)
Miwa, Shinya; Kanou, Masaki; Kume, Tetsuji; Sasaki, Shigeo
2013-06-01
Methane hydrate (MH) is widely observed in Earth's environment such as permafrost and deep sea floors. At low temperature and low pressure conditions, pure MH crystallizes a cubic structure I (sI) which consists of hydrogen-bonded two small and six medium water cages which enclathrate methane molecules as guests. However, actual MH in deep sea deposits contains not only methane molecules but also ethane and propane molecules. Therefore, the estimation of elastic properties and mechanical stability for both sI and structure II (sII) are required for the safe extraction of methane gas from the deep sea floors. The purpose of this study is to determine the elastic properties of methane-propane mixed gas hydrate (MPH) with sII by applying the high-pressure Brillouin spectroscopy to a single crystal of MPH-sII grown in a diamond anvil cell. The obtained elastic constant C11 of MPH-sII showing independent of pressure is obviously different from that of pure MH-sI. On the other hand, the C12 and C44 are similar to MH-sI. The present results suggest that a variety of gas hydrates have the individual elastic properties and stability depending on the gas hydrate structures.
Role of defects in frictional properties of 2-D materials
NASA Astrophysics Data System (ADS)
Kavalur, Aditya; Kim, Woo Kyun
Graphene and other 2-D materials have provided a promising prospect to improve the tribological properties of small length scale devices such as MEMS/NEMS due to their low friction coefficient and excellent wear resistance. Several recent research efforts have been devoted to unveiling the physical origin of the superior tribological properties of these 2-D materials from both experimental and theoretical standpoints, however, many of them still remain far from clearly understood. Recently, it was shown that lamellar materials do not conform to the predictions of the Prandtl-Tomlinson model due to additional friction mechanisms of delamination and visco-elastic ploughing. These mechanisms are critical as they explain the low and negative coefficients of friction observed in recent AFM experiments. However, thus far, most simulation and theoretical studies about these novel friction mechanisms have focused on only pristine graphene whereas real graphene sheets prepared by CVD and other conventional techniques possess various forms of defects such as vacancies and non-hexagonal rings. In this study we examine the role of these defects in frictional properties of 2-D materials in relation to delamination and visco-elastic ploughing.
Elastic properties of the titanate pyrochlore Tb2Ti2O7
NASA Astrophysics Data System (ADS)
Keppens, V.; Luan, Y.; Migliori, A.; Betts, J.; Zhou, H. D.; Dabkowska, H. A.; Gaulin, B. D.
2012-02-01
The presence of geometric frustration inhibits the formation of long-range spin ordering in Tb2Ti2O7 even at very low temperatures, making this compound the prototype of a ``spin liquid.'' We have initiated a study of the elastic properties of Tb2Ti2O7 as a function of temperature (0.5-300 K) and magnetic field (0-15T) using Resonant Ultrasound Spectroscopy (RUS). All three elastic constants show a pronounced softening below 50 K, indicative of a possible structural transition at very low temperatures. Application of a magnetic field partially suppresses the elastic softening in this compound, suggesting that the magnetoelastic coupling plays a significant role in the spin liquid physics of Tb2Ti2O7 at low temperatures.
Structural, elastic, electronic, magnetic and vibrational properties of CuCoMnGa under pressure
İyigör, Ahmet; Uğur, Şule
2014-10-06
First principles calculations for the structural, electronic, elastic and phonon properties of the cubic quaternary heusler alloy CuCoMnGa on pressure have been reported by density functional theory (DFT) within generalized gradient approximation (GGA). The calculated values of the elastic constants were used for estimations of the Debye temperatures, the bulk modulus, the shear modulus, the young modulus E, the poisson's ratio σ and the B/G ratio. The elastic constants satisfy all of the mechanical stability criteria. The electronic structures of the ferromagnetic configuration for CuCoMnGa have a metallic character. The estimated magnetic moment per formula unit is 3.76 μ{sub B}. The phonon dispersion is studied using the supercell approach, and the stable nature at 0.2 GPa pressure is observed.
NASA Astrophysics Data System (ADS)
Haddadi, K.; Bouhemadou, A.; Bin-Omran, S.; Maabed, S.; Khenata, R.
2015-01-01
The structural parameters, elastic constants, electronic structure and optical properties of the recently reported monoclinic quaternary nitridoaluminate LiCaAlN2 are investigated in detail using the ab initio plane-wave pseudopotential method within the generalized gradient approximation. The calculated equilibrium structural parameters are in excellent agreement with the experimental data, which validate the reliability of the applied theoretical method. The chemical and structural stabilities of LiCaAlN2 are confirmed by calculating the cohesion energy and enthalpy of formation. Chemical band stiffness is calculated to explain the pressure dependence of the lattice parameters. Through the band structure calculation, LiCaAlN2 is predicted to be an indirect band gap of 2.725 eV. The charge-carrier effective masses are estimated from the band structure dispersions. The frequency-dependent dielectric function, absorption coefficient, refractive index, extinction coefficient, reflectivity coefficient and electron energy loss function spectra are calculated for polarized incident light in a wide energy range. Optical spectra exhibit a noticeable anisotropy. Single-crystal and polycrystalline elastic constants and related properties, including isotropic sound velocities and Debye temperatures, are numerically estimated. The calculated elastic constants and elastic compliances are used to analyse and visualize the elastic anisotropy of LiCaAlN2. The calculated elastic constants demonstrate the mechanical stability and brittle behaviour of the considered material.
Pressure and temperature induced elastic properties of rare earth chalcogenides
NASA Astrophysics Data System (ADS)
Shriya, S.; Singh, N.; Sapkale, R.; Varshney, M.; Varshney, Dinesh
2016-05-01
The pressure and temperature dependent mechanical properties as Young modulus, Thermal expansion coefficient of rare earth REX (RE = La, Pr, Eu; X = O, S, Se, and Te) chalcogenides are studied. The rare earth chalcogenides showed a structural phase transition (B1-B2). Pressure dependence of Young modulus discerns an increase in pressure inferring the hardening or stiffening of the lattice as a consequence of bond compression and bond strengthening. Suppressed Young modulus as functions of temperature infers the weakening of the lattice results in bond weakening in REX. Thermal expansion coefficient demonstrates that REX (RE = La, Pr, Eu; X = O, S, Se, and Te) chalcogenides is mechanically stiffened, and thermally softened on applied pressure and temperature.
Manipulating lipid bilayer material properties using biologically active amphipathic molecules
NASA Astrophysics Data System (ADS)
Ashrafuzzaman, Md; Lampson, M. A.; Greathouse, D. V.; Koeppe, R. E., II; Andersen, O. S.
2006-07-01
Lipid bilayers are elastic bodies with properties that can be manipulated/controlled by the adsorption of amphipathic molecules. The resulting changes in bilayer elasticity have been shown to regulate integral membrane protein function. To further understand the amphiphile-induced modulation of bilayer material properties (thickness, intrinsic monolayer curvature and elastic moduli), we examined how an enantiomeric pair of viral anti-fusion peptides (AFPs)—Z-Gly-D-Phe and Z-Gly-Phe, where Z denotes a benzyloxycarbonyl group, as well as Z-Phe-Tyr and Z-D-Phe-Phe-Gly—alters the function of enantiomeric pairs of gramicidin channels of different lengths in planar bilayers. For both short and long channels, the channel lifetimes and appearance frequencies increase as linear functions of the aqueous AFP concentration, with no apparent effect on the single-channel conductance. These changes in channel function do not depend on the chirality of the channels or the AFPs. At pH 7.0, the relative changes in channel lifetimes do not vary when the channel length is varied, indicating that these compounds exert their effects primarily by causing a positive-going change in the intrinsic monolayer curvature. At pH 4.0, the AFPs are more potent than at pH 7.0 and have greater effects on the shorter channels, indicating that these compounds now change the bilayer elastic moduli. When AFPs of different anti-fusion potencies are compared, the rank order of the anti-fusion activity and the channel-modifying activity is similar, but the relative changes in anti-fusion potency are larger than the changes in channel-modifying activity. We conclude that gramicidin channels are useful as molecular force transducers to probe the influence of small amphiphiles upon lipid bilayer material properties.
NASA Astrophysics Data System (ADS)
Shankar, A.; Rai, D. P.; Chettri, Sandeep; Khenata, R.; Thapa, R. K.
2016-08-01
We have investigated the electronic structure, elastic and thermoelectric properties of the filled skutterudite CeRu4Sb12 using the density functional theory (DFT). The full potential linearized augmented plane wave (FP-LAPW) method within a framework of the generalized gradient approximation (GGA) approach is used to perform the calculations presented here. The electronic structure calculation suggests an indirect band gap semiconducting nature of the material with energy band gap of 0.08 eV. The analysis of the elastic constants at relaxed positions reveals the ductile nature of the sample material with covalent contribution in the inter-atomic bonding. The narrow band gap semiconducting nature with high value of Seebeck coefficient suggests the possibility of the thermoelectric application of the material. The analysis of the thermal transport properties confirms the result obtained from the energy band structure of the material with high thermopower and dimensionless figure of merit 0.19 at room temperature.
NASA Astrophysics Data System (ADS)
Kanoun, Mohammed Benali; Goumri-Said, Souraya; Reshak, Ali H.; Merad, Abdelkarim E.
2010-05-01
We have performed ab initio calculations for the nanolaminates Zr 2AC (A = Ti, In, Tl, Si, Ge, Sn, Pb, P, As, S) ceramics to study their electronic structure, elastic and optical properties. In this work, we used the accurate augmented plane wave plus local orbital method with density functional theory to find the equilibrium structural parameters, dielectric functions and to compute the full elastic tensors. The obtained elastic constants were used to quantify the stiffness of the Zr 2AC phases and to appraise their mechanical stability. The relationship between elastic, electronic and valence electron concentration is discussed. Our results show that the bulk modulus and shear modulus increase across the periodic table for Zr 2AC. Furthermore, trends in elastic stiffness are well explained in terms of electronic structure analysis, as occupation of valence electrons in states near the Fermi level of Zr 2AC. We show that increments of bulk moduli originate from additional valence electrons filling states involving Zr d-A p. We show also that Zr d-A p hybridizations are located just below the Fermi level and are weaker bonds than the Zr d-C p hybridizations, which are deeper in energy. As a function of the p-state filling of the A element the Zr d-A p bands are driven to deeper energy. The optical spectra were analyzed by means of the electronic structure, which provides theoretical understanding of the conduction mechanism of these ceramics.
Elastic properties of Thiel-embalmed human ankle tendon and ligament.
Liao, Xiaochun; Kemp, Sandy; Corner, George; Eisma, Roos; Huang, Zhihong
2015-10-01
Thiel embalming is recommended as an alternative to formalin-based embalming because it preserves tissue elasticity, color, and flexibility in the long term, with low infection and toxicity risk. The degree to which Thiel embalming preserves elasticity has so far been assessed mainly by subjective scoring, with little quantitative verification. The aim of this study is to quantify the effect of Thiel embalming on the elastic properties of human ankle tendons and ligament. Biomechanical tensile tests were carried out on six Thiel-embalmed samples each of the peroneus longus, peroneus brevis, and calcaneal tendons, and the calcaneofibular ligament, with strain rates of 0.25%s(-1), 2%s(-1), and 8%s(-1). The stress-strain relationship was calculated from the force-extension response with cross-sectional area and gauge length. Young's modulus was determined from the stress-strain curve. The results showed that the tendon and ligament elasticity were lower after Thiel embalming than the literature values for fresh nonembalmed tendons and ligament. The biomechanical tensile test showed that the measured elasticity of Thiel-embalmed tendons and ligaments increased with the strain rate. The Thiel embalming method is useful for preserving human ankle tendons and ligaments for anatomy and surgery teaching and research, but users need to be aware of its softening effects. The method retains the mechanical strain rate effect on tendons and ligament. PMID:25707906
Significance of 1B and 2B domains in modulating elastic properties of lamin A.
Bera, Manindra; Ainavarapu, Sri Rama Koti; Sengupta, Kaushik
2016-01-01
Nuclear lamins are type V intermediate filament proteins which form an elastic meshwork underlying the inner nuclear membrane. Lamins directly contribute to maintain the nuclear shape and elasticity. More than 400 mutations have been reported in lamin A that are involved in diseases known as laminopathies. These mutations are scattered mainly in the lamin rod domain along with some in its C-terminal domain. The contribution of the rod domain towards the elasticity of lamin A molecule was hitherto unknown. Here, we have elucidated the significance of the 1B and 2B domains of the rod in modulating the elastic behavior of lamin A by single-molecule force spectroscopy. In addition, we have also studied the network forming capacity of these domains and their corresponding viscoelastic behavior. We have shown that the 1B domain has the ability to form a lamin-like network and resists larger deformation. However at the single-molecular level, both the domains have comparable mechanical properties. The self-assembly of the 1B domain contributes to the elasticity of the lamin A network. PMID:27301336
Significance of 1B and 2B domains in modulating elastic properties of lamin A
Bera, Manindra; Ainavarapu, Sri Rama Koti; Sengupta, Kaushik
2016-01-01
Nuclear lamins are type V intermediate filament proteins which form an elastic meshwork underlying the inner nuclear membrane. Lamins directly contribute to maintain the nuclear shape and elasticity. More than 400 mutations have been reported in lamin A that are involved in diseases known as laminopathies. These mutations are scattered mainly in the lamin rod domain along with some in its C-terminal domain. The contribution of the rod domain towards the elasticity of lamin A molecule was hitherto unknown. Here, we have elucidated the significance of the 1B and 2B domains of the rod in modulating the elastic behavior of lamin A by single-molecule force spectroscopy. In addition, we have also studied the network forming capacity of these domains and their corresponding viscoelastic behavior. We have shown that the 1B domain has the ability to form a lamin-like network and resists larger deformation. However at the single-molecular level, both the domains have comparable mechanical properties. The self-assembly of the 1B domain contributes to the elasticity of the lamin A network. PMID:27301336
The effect of tissue elastic properties and surfactant on alveolar stability.
Andreassen, Steen; Steimle, Kristoffer L; Mogensen, Mads L; Bernardino de la Serna, Jorge; Rees, Stephen; Karbing, Dan S
2010-11-01
This paper presents a novel mathematical model of alveoli, which simulates the effects of tissue elasticity and surfactant on the stability of human alveoli. The model incorporates a spherical approximation to the alveolar geometry, the hysteretic behavior of pulmonary surfactant and tissue elasticity. The model shows that the alveolus without surfactant and the elastic properties of the lung tissue are always at an unstable equilibrium, with the capability both to collapse irreversibly and to open with infinite volume when the alveolus has small opening radii. During normal tidal breathing, the alveolus can becomes stable, if surfactant is added. Including the passive effect of tissue elasticity stabilizes the alveolus, further allowing the alveoli to be stable, even for lung volumes below residual volume. The model is the first to describe the combined effects of tissue elasticity and surfactant on alveolar stability. The model may be used as an integrated part of a more comprehensive model of the respiratory system, since it can predict opening pressures of alveoli. PMID:20724566
Bocskai, Zoltán I; Sándor, Gábor L; Kiss, Zoltán; Bojtár, Imre; Nagy, Zoltán Z
2014-10-17
The mechanical behaviour of zonular fibres greatly affects the accommodation process in mammalian eyes. This paper introduces a detailed measurement procedure for the purpose of obtaining the force-displacement diagram necessary to evaluate the mechanical properties of porcine zonular fibres in situ. It is a complex technique, keeping the integrity of the zonular bundles between the crystalline lens and the ciliary muscle cells. We present a brief description of the measurement procedure both in theory and in practice, along with the force-displacement diagrams acquired from a porcine sample group. The strengths of this newly developed method are the unequivocal force transmission between the sample and the transducer, and the intact connection between the ciliary body and the crystalline lens via zonular fibres. With the aid of these measurements, we define an estimated material model for the zonular apparatus both analytically and using the finite element method. The two different evaluation methods show close agreement in the calculated Young's modulus for the zonular fibres. The range of the calculated elastic modulus is 200-250 kPa. This new measuring method is adaptable to human specimens. Despite its complexity, the entire procedure and the evaluation part are reproducible. The constitutive model aims to shed light on the mechanics of the accommodation process. PMID:25242131
Effect of minor elements (Al3+ and H+) on the elastic properties of mantle minerals
NASA Astrophysics Data System (ADS)
Sanchez-Valle, Carmen; Wang, Jingyun
2010-05-01
Over the past decades, the improvement on the seismic techniques have provided a more detailed picture of the structure of the mantle and revealed complexities in the seismic velocity profiles. In particular, high-resolution seismic tomography studies provide evidence for strong lateral velocity variations in the lower mantle that may be partially associated to chemical heterogeneities. The sound velocities, elasticity, and crystal chemistry of silicate and oxide minerals in Earth's mantle are therefore essential for the interpretation of seismic observations, as well as for the modeling of the geochemical and geodynamical evolution of the mantle. However, while the elastic properties of end-member mineral phases have received much attention over the past years, the influence of minor element substitutions on the elastic properties of mantle minerals is not yet well constrained. In this talk we review recent investigations of the effect of minor elements, namely Al3+ and H+, on the high pressure elastic properties of major minerals in the upper and lower mantle. In particular, we will present recent Brillouin spectroscopy measurements to determine the acoustic velocities and elasticity of single-crystal hydrous aluminous-bearing orthopyroxene (AlOpx) containing 6.3wt% Al2O3 and 1500 ppm H2O. The results confirm that the stiffening of the bulk modulus reported in natural Opx relative to Mg-end-members and Mg-Fe solid solutions is related to the substitution of Al3+ for smaller Si4+ in tetrahedral sites. AlOpx is also characterized by compressional (VP) and shear (VS) wave velocities that are 7% and 4% higher than those of the magnesium end-member. These observations indicate that Al3+ has the strongest effect on the seismic velocities of Opx of all minor elements and may be taken into account to refine compositional and mineralogical models of the upper mantle. The evolution with pressure of the elastic properties, their relation to crystal structure and the effect
NASA Astrophysics Data System (ADS)
Mohapatra, Himansu; Eckhardt, Craig J.
2007-03-01
Polymorphism is the property of a compound to crystallize in two or more crystalline phases containing different arrangements and/or conformations of the molecules in the crystal lattice. The Phenomenon of polymorphism is a major issue in the pharmaceutical industry especially in relation to drug uptake in the body, tablet processing and growth. This has led to considerable interest in predicting and understanding properties of drug polymorphs, and more recently the mechanical properties of the polymorphs. In this work, Brillouin scattering is used to probe the acoustic phonons of the monoclinic (P21/c) polymorph of the drug, carbamazepine (CBZ). By sampling a variety of acoustic phonons, the complete elastic constant tensor has been determined for this CBZ polymorph. The observed trend in the elastic constants: C11< C22˜C33 is qualitatively associated with the crystal growth pattern seen in CBZ. Investigation into the anisotropy of the intermolecular interactions has been investigated further by calculation of linear compressibilities.
Assessing the elastic properties and ductility of Fe-Cr-Al alloys from ab initio calculations
NASA Astrophysics Data System (ADS)
Nurmi, E.; Wang, G.; Kokko, K.; Vitos, L.
2016-01-01
Fe-Al is one of the best corrosion resistant alloys at high temperatures. The flip side of Al addition to Fe is the deterioration of the mechanical properties. This problem can be solved by adding a suitable amount of third alloying component. In the present work, we use ab initio calculations based on density functional theory to study the elastic properties of Fe?Cr?Al? alloys for Al and Cr contents up to 20 at.%. We assess the ductility as a function of chemistry by making use of the semi-empirical correlations between the elastic parameters and mechanical properties. In particular, we derive the bulk modulus to shear modulus ratio and the Cauchy pressure and monitor their trends in terms of chemical composition. The present findings are contrasted with the previously established oxidation resistance of Fe-Cr-Al alloys.
Elastic properties of forsterite at high pressure obtained from the high-temperature database
NASA Astrophysics Data System (ADS)
Cynn, Hyunchae; Isaak, Donald G.; Anderson, Orson L.
We examine the possibility of computing the high pressure P elastic properties of forsterite using acoustic resonant frequencies measured at elevated temperature T (but at P = 0). The transformation into P space from T space requires three imposed conditions: (1) that the property αKT be independent of volume V (α is the volume coefficient of thermal expansivity, and KT is the isothermal bulk modulus); (2) that CV, the heat capacity at constant volume, be quasiharmonic at high T; and (3) that the acoustic resonant mode frequencies be linear in P. We also compute the high-pressure elastic properties of NaCl and MgO to provide comparisons with the results for forsterite. We show that NaCl meets all three conditions, but that for MgO, the first condition is not met. For forsterite the second condition is not met.
Predicting Elastic Properties of β-HMX from First-principles Calculations
NASA Astrophysics Data System (ADS)
Peng, Qing; Rahul, -; Wang, Guangyu; Liu, Gui-Rong; Grimme, Stefan; de, Suvranu
2015-03-01
We investigate the performance of the van der Waals (vdW) functions in predicting the elastic constants of the β-polymorph of cyclotetramethylene tetranitramine (HMX) energetic molecular crystal using density functional theory (DFT) calculations. We confirm that the accuracy of the elastic constants is significantly improved using the vdW corrections with environment dependent C6 together with PBE and revised PBE exchange-correlation functionals. The elastic constants obtained using PBE-D3(0) calculations yield the most accurate mechanical response of β-HMX, with compared to the experimental stress-strain data. The PBEsol without vdW corrections can also predict the elastic constants well. Our results suggest that PBE-D3 calculations are reliable in predicting the elastic constants of this material. The authors would like to acknowledge the generous financial support from the Defense Threat Reduction Agency (DTRA) Grant # HDTRA1-13-1-0025, and the Office of Naval Research grants ONR Award # N00014-08-1-0462 and # N00014-12-1-0527.
Ling, Yuting; Li, Chunhui; Feng, Kairui; Duncan, Robyn; Eisma, Roos; Huang, Zhihong; Nabi, Ghulam
2016-05-01
Fixed and preserved tissues have been massively used in the development of biomedical equipment and instrumentation. Not only the tissue morphology, but also its mechanical properties need to be considered in the fixation and preservation procedures since mechanical properties have significant influence on the design and performance of such instruments. Understanding the effects of storage and preservation conditions on the mechanical properties of soft tissue has both clinical and experimental significance. To this end, we aimed to study the effects of tissue preservation (by 10% formalin and Thiel fluids) on the elastic properties of five different kinds of fresh tissues from pig and chicken; specifically fat, liver, muscle, tendon and cartilage. The tissue elasticity was measured intensively and strictly within a controlled timeline of 6 months by quantitative optical coherence elastography (OCE) system. Our findings suggest that the elasticity change of tissues in the formalin solution has an ascending trend, but that of Thiel remains almost constant, providing a more real texture and properties. PMID:26903410
Shirazi, Reza; Vena, Pasquale; Sah, Robert L.; Klisch, Stephen M.
2012-01-01
Despite distinct mechanical functions, biological soft tissues have a common microstructure in which a ground matrix is reinforced by a collagen fibril network. The microstructural properties of the collagen network contribute to continuum mechanical tissue properties that are strongly anisotropic with tensile-compressive asymmetry. In this study, a novel approach based on a continuous distribution of collagen fibril volume fractions is developed to model fibril reinforced soft tissues as a nonlinearly elastic and anisotropic material. Compared with other approaches that use a normalized number of fibrils for the definition of the distribution function, this representation is based on a distribution parameter (i.e. volume fraction) that is commonly measured experimentally while also incorporating pre-stress of the collagen fibril network in a tissue natural configuration. After motivating the form of the collagen strain energy function, examples are provided for two volume fraction distribution functions. Consequently, collagen second-Piola Kirchhoff stress and elasticity tensors are derived, first in general form and then specifically for a model that may be used for immature bovine articular cartilage. It is shown that the proposed strain energy is a convex function of the deformation gradient tensor and, thus, is suitable for the formation of a polyconvex tissue strain energy function. PMID:23390357
Designing functionally graded materials with superior load-bearing properties
Zhang, Yu; Sun, Ming-jie; Zhang, Denzil
2011-01-01
Ceramic prostheses often fail from fracture and wear. We hypothesize that these failures may be substantially mitigated by an appropriate grading of elastic modulus at the ceramic surface. In this study, we elucidate the effect of elastic modulus profile on the flexural damage resistance of functionally graded materials (FGMs), providing theoretical guidlines for designing FGM with superior load-bearing property. The Young's modulus of the graded structure is assumed to vary in a power-law relation with a scaling exponent n; this is in accordance with experimental observations from our laboratory and elsewhere. Based on the theory for bending of graded beams, we examine the effect of n value and bulk-to-surface modulus ratio (Eb/Es) on stress distribution through the graded layer. Theory predicts that a low exponent (0.15 < n < 0.5), coupled with a relatively small modulus ratio (3 < Eb/Es < 6), is most desirable for reducing the maximum stress and transferring it into the interior, while keeping the surface stress low. Experimentally, we demonstrate that elastically graded materials with various n values and Eb/Es ratios can be fabricated by infiltrating alumina and zirconia with a low-modulus glass. Flexural tests show that graded alumina and zirconia with suitable values of these parameters exhibit superior load-bearing capacity, 20% to 50% higher than their homogeneous counterparts. Improving load-bearing capacity of ceramic materials could have broad impacts on biomedical, civil, structural, and an array of other engineering applications. PMID:22178651
Peng, Qing; De, Suvranu
2014-10-21
Silicane is a fully hydrogenated silicene-a counterpart of graphene-having promising applications in hydrogen storage with capacities larger than 6 wt%. Knowledge of its elastic limit is critical in its applications as well as tailoring its electronic properties by strain. Here we investigate the mechanical response of silicane to various strains using first-principles calculations based on density functional theory. We illustrate that non-linear elastic behavior is prominent in two-dimensional nanomaterials as opposed to bulk materials. The elastic limits defined by ultimate tensile strains are 0.22, 0.28, and 0.25 along armchair, zigzag, and biaxial directions, respectively, an increase of 29%, 33%, and 24% respectively in reference to silicene. The in-plane stiffness and Poisson ratio are reduced by a factor of 16% and 26%, respectively. However, hydrogenation/dehydrogenation has little effect on its ultimate tensile strengths. We obtained high order elastic constants for a rigorous continuum description of the nonlinear elastic response. The limitation of second, third, fourth, and fifth order elastic constants are in the strain range of 0.02, 0.08, and 0.13, and 0.21, respectively. The pressure effect on the second order elastic constants and Poisson's ratio were predicted from the third order elastic constants. Our results could provide a safe guide for promising applications and strain-engineering the functions and properties of silicane monolayers. PMID:25190587
NASA Astrophysics Data System (ADS)
Namani, Ravi
Mechanical properties are essential for understanding diseases that afflict various soft tissues, such as osteoarthritic cartilage and hypertension which alters cardiovascular arteries. Although the linear elastic modulus is routinely measured for hard materials, standard methods are not available for extracting the nonlinear elastic, linear elastic and time-dependent properties of soft tissues. Consequently, the focus of this work is to develop indentation methods for soft biological tissues; since analytical solutions are not available for the general context, finite element simulations are used. First, parametric studies of finite indentation of hyperelastic layers are performed to examine if indentation has the potential to identify nonlinear elastic behavior. To answer this, spherical, flat-ended conical and cylindrical tips are examined and the influence of thickness is exploited. Also the influence of the specimen/substrate boundary condition (slip or non-slip) is clarified. Second, a new inverse method---the hyperelastic extraction algorithm (HPE)---was developed to extract two nonlinear elastic parameters from the indentation force-depth data, which is the basic measurement in an indentation test. The accuracy of the extracted parameters and the influence of noise in measurements on this accuracy were obtained. This showed that the standard Berkovitch tip could only extract one parameter with sufficient accuracy, since the indentation force-depth curve has limited sensitivity to both nonlinear elastic parameters. Third, indentation methods for testing tissues from small animals were explored. New methods for flat-ended conical tips are derived. These account for practical test issues like the difficulty in locating the surface or soft specimens. Also, finite element simulations are explored to elucidate the influence of specimen curvature on the indentation force-depth curve. Fourth, the influence of inhomogeneity and material anisotropy on the extracted
Magneto-elastic effects and thermodynamic properties of ferromagnetic hcp Co
NASA Astrophysics Data System (ADS)
Kuang, Fang-Guang; Kuang, Xiao-Yu; Kang, Shu-Ying; Mao, Ai-Jie
2014-05-01
Using first principles projector augmented wave (PAW) potential method, the magneto-elastic effects and thermodynamic properties of ferromagnetic hcp Cobalt at high pressure and temperature are investigated. The calculated elastic constants from PBE+U method demonstrate a noticeable improvement with regard to experimental data. Various physical quantities under high pressure also present significant improvements, such as the bulk modulus, shear modulus, Young's modulus, Debye temperature, various sound velocities and the normalized acoustic velocities in the meridian plane. That is due to the fact that Cobalt system possesses large correlation effects. Meanwhile, the phonon dispersion curves are in excellent agreement with experimental data. It is not observed any anomaly or instability under compression. However, according to the E2g-phonon frequencies, the obtained pressure variation of C44 elastic modulus also suggests that the system has miraculous magneto-elastic effects. Moreover, the pressure and temperature dependence of thermodynamic properties are derived within the quasi-harmonic approximation for the first time. The obtained Grüneisen ratio, Anderon-Grüneisen parameter and the volume dependence of Grüneisen ratio display manifestly temperature and pressure dependences.
Cyclic Material Properties Test to Determine Hardening/Softening Characteristics of HY-80 Steel
S.C. Hodge; J.M. Minicucci; T.F. Trimble
2003-04-30
The Cyclic Material Properties Test was structured to obtain and provide experimental data for determining cyclic hardening/softening characteristics of HY-80 steel. The inelastic strain history data generated by this test program and the resulting cyclic stress-strain curve will be used to enhance material models in the finite element codes used to perform nonlinear elastic-plastic analysis.
NASA Technical Reports Server (NTRS)
Poole, L. R.
1972-01-01
A computer program is presented by which the effects of nonlinear suspension-system elastic characteristics on parachute inflation loads and motions can be investigated. A mathematical elastic model of suspension-system geometry is coupled to the planar equations of motion of a general vehicle and canopy. Canopy geometry and aerodynamic drag characteristics and suspension-system elastic properties are tabular inputs. The equations of motion are numerically integrated by use of an equivalent fifth-order Runge-Kutta technique.
Sermeus, J.; Glorieux, C.; Sinha, R.; Vereecken, P. M.; Vanstreels, K.
2014-07-14
MnO{sub 2} is a material of interest in the development of high energy-density batteries, specifically as a coating material for internal 3D structures, thus ensuring rapid energy deployment. Its electrochemical properties have been mapped extensively, but there are, to the best of the authors' knowledge, no records of the elastic properties of thin film MnO{sub 2}. Impulsive stimulated thermal scattering (ISTS), also known as the heterodyne diffraction or transient grating technique, was used to determine the Young's modulus (E) and porosity (ψ) of a 500 nm thick MnO{sub 2} coating on a Si(001) substrate. ISTS is an all optical method that is able to excite and detect surface acoustic waves (SAWs) on opaque samples. From the measured SAW velocity dispersion, the Young's modulus and porosity were determined to be E = 25 ± 1 GPa and ψ=42±1%, respectively. These values were confirmed by independent techniques and determined by a most-squares analysis of the carefully fitted SAW velocity dispersion. This study demonstrates the ability of the presented technique to determine the elastic parameters of a thin, porous film on an anisotropic substrate.
Maciel, Alfredo; Presbítero, Gerardo; Piña, Cristina; del Pilar Gutiérrez, María; Guzmán, José; Munguía, Nadia
2015-01-01
A clear understanding of the dependence of mechanical properties of bone remains a task not fully achieved. In order to estimate the mechanical properties in bones for implants, pore cross-section area, calcium content, and apparent density were measured in trabecular bone samples for human implants. Samples of fresh and defatted bone tissue, extracted from one year old bovines, were cut in longitudinal and transversal orientation of the trabeculae. Pore cross-section area was measured with an image analyzer. Compression tests were conducted into rectangular prisms. Elastic modulus presents a linear tendency as a function of pore cross-section area, calcium content and apparent density regardless of the trabecular orientation. The best variable to estimate elastic modulus of trabecular bone for implants was pore cross-section area, and affirmations to consider Nukbone process appropriated for marrow extraction in trabecular bone for implantation purposes are proposed, according to bone mechanical properties. Considering stress-strain curves, defatted bone is stiffer than fresh bone. Number of pores against pore cross-section area present an exponential decay, consistent for all the samples. These graphs also are useful to predict elastic properties of trabecular samples of young bovines for implants. PMID:25585977
Elastic properties and apparent density of human edentulous maxilla and mandible
Seong, Wook-Jin; Kim, Uk-Kyu; Swift, James Q.; Heo, Young-Cheul; Hodges, James S.; Ko, Ching-Chang
2009-01-01
The aim of this study aim was to determine whether elastic properties and apparent density of bone differ in different anatomical regions of the maxilla and mandible. Additional analyses assessed how elastic properties and apparent density were related. Four pairs of edentulous maxilla and mandibles were retrieved from fresh human cadavers. Bone samples from four anatomical regions (maxillary anterior, maxillary posterior, mandibular anterior, mandibular posterior) were obtained. Elastic modulus (EM) and hardness (H) were measured using the nano-indentation technique. Bone samples containing cortical and trabecular bone were used to measure composite apparent density (cAD) using Archimedes’ principle. Statistical analyses used repeated measures ANOVA and Pearson correlations. Bone physical properties differed between regions of the maxilla and mandible. Generally, mandible had higher physical property measurements than maxilla. EM and H were higher in posterior than in anterior regions; the reverse was true for cAD. Posterior maxillary cAD was significantly lower than that in the three other regions. PMID:19647417
MPOD: A Material Property Open Database linked to structural information
NASA Astrophysics Data System (ADS)
Pepponi, Giancarlo; Gražulis, Saulius; Chateigner, Daniel
2012-08-01
Inspired by the Crystallography Open Database (COD), the Material Properties Open Database (MPOD) was given birth. MPOD aims at collecting and making publicly available at no charge tensorial properties (including scalar properties) of phases and linking such properties to structural information of the COD when available. MPOD files are written with the STAR file syntax, used and developed for the Crystallographic Information Files. A dictionary containing new definitions has been written according to the Dictionary Definition Language 1, although some tricks were adopted to allow for multiple entries still avoiding ambiguousness. The initial set includes mechanical properties, elastic stiffness and compliance, internal friction; electrical properties, resistivity, dielectric permittivity and stiffness, thermodynamic properties, heat capacity, thermal conductivity, diffusivity and expansion; electromechanical properties, piezoelectricity, electrostriction, electromechanical coupling; optical properties; piezooptic and photoelastic properties; superconducting properties, critical fields, penetration and coherence lengths. Properties are reported in MPOD files where the original published paper containing the data is cited and structural and experimental information is also given. One MPOD file contains information relative to only one publication and one phase. The files and the information contained therein can also be consulted on-line at http://www.materialproperties.org.
Material Property Measurement in Hostile Environments using Laser Acoustics
Ken L. Telschow
2004-08-01
Acoustic methods are well known and have been used to measure various intrinsic material properties, such as, elastic coefficients, density, crystal axis orientation, microstructural texture, and residual stress. Extrinsic properties, such as, dimensions, motion variables or temperature are also readily determined from acoustic methods. Laser acoustics, employing optical generation and detection of elastic waves, has a unique advantage over other acoustic methods—it is noncontacting, uses the sample surface itself for transduction, requires no couplant or invasive sample surface preparation and can be utilized in any hostile environment allowing optical access to the sample surface. In addition, optical generation and detection probe beams can be focused to the micron scale and/or shaped to alter the transduction process with a degree of control not possible using contact transduction methods. Laser methods are amenable to both continuous wave and pulse-echo measurements and have been used from Hz to 100’s of GHz (time scales from sec to psec) and with amplitudes sufficient to fracture materials. This paper shall review recent applications of laser acoustic methods to determining material properties in hostile environments that preclude the use of contacting transduction techniques. Example environments include high temperature (>1000C) sintering and molten metal processing, thin film deposition by plasma techniques, materials moving at high velocity during the fabrication process and nuclear high radiation regions. Recent technological advances in solid-state lasers and telecommunications have greatly aided the development and implementation of laser acoustic methods, particularly at ultra high frequencies. Consequently, laser acoustic material property measurements exhibit high precision and reproducibility today. In addition, optical techniques provide methods of imaging acoustic motion that is both quantitative and rapid. Possible future directions for
Elastically driven cooperative response of a molecular material impacted by a laser pulse.
Bertoni, Roman; Lorenc, Maciej; Cailleau, Hervé; Tissot, Antoine; Laisney, Jérôme; Boillot, Marie-Laure; Stoleriu, Laurentiu; Stancu, Alexandru; Enachescu, Cristian; Collet, Eric
2016-06-01
Photoinduced phase transformations occur when a laser pulse impacts a material, thereby transforming its electronic and/or structural orders, consequently affecting the functionalities. The transient nature of photoinduced states has thus far severely limited the scope of applications. It is of paramount importance to explore whether structural feedback during the solid deformation has the capacity to amplify and stabilize photoinduced transformations. Contrary to coherent optical phonons, which have long been under scrutiny, coherently propagating cell deformations over acoustic timescales have not been explored to a similar degree, particularly with respect to cooperative elastic interactions. Herein we demonstrate, experimentally and theoretically, a self-amplified responsiveness in a spin-crossover material during its delayed volume expansion. The cooperative response at the material scale prevails above a threshold excitation, significantly extending the lifetime of photoinduced states. Such elastically driven cooperativity triggered by a light pulse offers an efficient route towards the generation and stabilization of photoinduced phases in many volume-changing materials. PMID:27019383
Processing and nanostructure influences on mechanical properties of thermoelectric materials
NASA Astrophysics Data System (ADS)
Schmidt, Robert David
Thermoelectric (TE) materials are materials that can generate an electric current from a thermal gradient, with possible service in recovery of waste heat such as engine exhaust. Significant progress has been made in improving TE conversion efficiency, typically reported according to the figure of merit, ZT, with several recent papers publishing ZT values above 2. Furthermore, cost reductions may be made by the use of lower cost elements such as Mg, Si, Sn, Pb, Se and S in TE materials, while achieving ZT values between 1.3 and 1.8. To be used in a device, the thermoelectric material must be able to withstand the applied thermal and mechanical forces without failure. However, these materials are brittle, with low fracture toughness typically less than 1.5 MPa-m1/2, and often less than 0.5 MPa-m1/2. For comparison, window glass is approximately 0.75 MPa-m1/2. They have been optimized with nanoprecipitates, nanoparticles, doping, alterations in stoichiometry, powder processing and other techniques, all of which may alter the mechanical properties. In this study, the effect of SiC nanoparticle additions in Mg2Si, SnTe and Ag nanoparticle additions in the skutterudite Ba0.3Co 4Sb12 on the elastic moduli, hardness and fracture toughness are measured. Large changes (˜20%) in the elastic moduli in SnTe 1+x as a function of x at 0 and 0.016 are shown. The effect on mechanical properties of doping and precipitates of CdS or ZnS in a PbS or PbSe matrix have been reported. Changes in sintering behavior of the skutterudite with the Ag nanoparticle additions were explored. Possible liquid phase sintering, with associated benefits in lower processing temperature, faster densification and lower cost, has been shown. A technique has been proposed for determining additional liquid phase sintering aids in other TE materials. The effects of porosity, grain size, powder processing method, and sintering method were explored with YbAl3 and Ba0.3Co4Sb 12, with the porosity dependence of
Cyclic cryopreservation affects the nanoscale material properties of trabecular bone.
Landauer, Alexander K; Mondal, Sumona; Yuya, Philip A; Kuxhaus, Laurel
2014-11-01
Tissues such as bone are often stored via freezing, or cryopreservation. During an experimental protocol, bone may be frozen and thawed a number of times. For whole bone, the mechanical properties (strength and modulus) do not significantly change throughout five freeze-thaw cycles. Material properties at the trabecular and lamellar scales are distinct from whole bone properties, thus the impact of freeze-thaw cycling at this scale is unknown. To address this, the effect of repeated freezing on viscoelastic material properties of trabecular bone was quantified via dynamic nanoindentation. Vertebrae from five cervine spines (1.5-year-old, male) were semi-randomly assigned, three-to-a-cycle, to 0-10 freeze-thaw cycles. After freeze-thaw cycling, the vertebrae were dissected, prepared and tested. ANOVA (factors cycle, frequency, and donor) on storage modulus, loss modulus, and loss tangent, were conducted. Results revealed significant changes between cycles for all material properties for most cycles, no significant difference across most of the dynamic range, and significant differences between some donors. Regression analysis showed a moderate positive correlation between cycles and material property for loss modulus and loss tangent, and weak negative correlation for storage modulus, all correlations were significant. These results indicate that not only is elasticity unpredictably altered, but also that damping and viscoelasticity tend to increase with additional freeze-thaw cycling. PMID:25278046
NASA Astrophysics Data System (ADS)
Ortiz, Aurélie U.; Boutin, A.; Fuchs, Alain H.; Coudert, François-Xavier
2013-05-01
We present here a framework for the analysis of the full tensors of second-order elastic constants of metal-organic frameworks, which can be obtained by ab initio calculations. We describe the various mechanical properties one can derive from such tensors: directional Young's modulus, shear modulus, Poisson ratio, and linear compressibility. We then apply this methodology to four different metal-organic frameworks displaying a wine-rack structure: MIL-53(Al), MIL-47, MIL-122(In), and MIL-140A. From these results, we shed some light into the link between mechanical properties, geometric shape, and compliance of the framework of these porous solids. We conclude by proposing a simple criterion to assess the framework compliance, based on the lowest eigenvalue of its second-order elastic tensor.
GENERAL: Structure properties and Noether symmetries for super-long elastic slender rod
NASA Astrophysics Data System (ADS)
Fu, Jing-Li; Zhao, Wei-Jia; Weng, Yu-Quan
2008-07-01
DNA is a nucleic acid molecule with double-helical structures that are special symmetrical structures attracting great attention of numerous researchers. The super-long elastic slender rod, an important structural model of DNA and other long-train molecules, is a useful tool in analysing the symmetrical properties and the stabilities of DNA. This paper studies the structural properties of a super-long elastic slender rod as a structural model of DNA by using Kirchhoff's analogue technique and presents the Noether symmetries of the model by using the method of infinitesimal transformation. Based on Kirchhoff's analogue it analyses the generalized Hamilton canonical equations. The infinitesimal transformations with respect to the radial coordinate, the generalized coordinates, and the quasi-momenta of the model are introduced. The Noether symmetries and conserved quantities of the model are obtained.
NASA Astrophysics Data System (ADS)
Liu, X. P.; Ni, Y.; He, L. H.
2016-04-01
Atomistic molecular dynamics simulations are performed to study the elastic properties of alkylthiol-functionalized gold supracrystals. The predicted Young's and shear moduli are around 1 GPa and 100 MPa, respectively. We show that, with increasing NC size, the Young's modulus decreases while the shear modulus essentially remains invariant; with increasing ligand length, the Young's modulus increases but the shear modulus decreases. Moreover, significant increase in the Young's modulus is seen when the polycrystalline NCs are replaced by single-crystal ones of the same size. All these are in reasonable agreement with available experiments. We attribute the mechanisms to the interaction between capping ligands as well as its variations caused by the change in ligand length and NC geometry. The results may deepen our understanding of elastic properties of the supracrystals and their influential factors.
Frequency and fluid effects on elastic properties of basalt: Experimental investigations
NASA Astrophysics Data System (ADS)
Adelinet, M.; Fortin, J.; Guéguen, Y.; Schubnel, A.; Geoffroy, L.
2010-01-01
In order to investigate the effects of fluid and frequency on the elastic properties, we performed hydrostatic experiments on an Icelandic basalt specimen under both dry and saturated conditions. This basalt is characterized by a bimodal porosity, i.e., cracks and equant pores. The elastic properties -bulk moduli in our case- were investigated under high pressure through two experimental methods: (1) a classical one using ultrasonic P- and S-waves velocities (frequency 106 Hz), (2) and a new one, using oscillation tests (frequency 10-2 Hz). In dry condition, experimental data show no significant difference between high (HF) and low (LF) frequency bulk moduli. However, in saturated conditions, two effects are highlighted: a physico-chemical effect emphasized by a difference between drained and dry moduli, and a squirt-flow effect evidenced by a difference between HF and LF undrained moduli.
NASA Astrophysics Data System (ADS)
Xing, Mengjiang; Li, Binhua; Yu, Zhengtao; Chen, Qi
2016-04-01
The structural, mechanical, electronic and thermodynamic properties of the tetragonal structure germanium carbonitride (t-GeCN) were first investigated using the density function theory with the ultrasoft psedopotential scheme in the frame of the generalized gradient approximation and the local density approximation. The elastic constants have confirmed that the t-GeCN is mechanically stable and phonon spectra have confirmed that the t-GeCN is dynamically stable. The anisotropy studies show that t-GeCN exhibits a larger anisotropy in its Poisson's ratio, Young's modulus, shear modulus, sound velocities and universal elastic anisotropy index. Electronic structure study shows that t-GeCN is an indirect semiconductor with band gap of 0.628 eV. The thermodynamic properties of t-GeCN, including Debye temperature, heat capacity, Grüneisen parameter and thermal expansion coefficient are investigated utilizing the quasi-harmonic Debye model.
Evolutions of elastic-plastic shock compression waves in different materials
NASA Astrophysics Data System (ADS)
Kanel, G. I.; Zaretsky, E. B.; Razorenov, S. V.; Savinykh, A. S.; Garkushin, G. V.
2015-06-01
Measurements of decay of the elastic precursor wave are used to determine the initial plastic strain rate as a function of the stress. Last years we performed large series of such kind experiments with metals and alloys at various temperatures, ceramics and glasses. In course of these measurements we observed several unexpected effects which have not got exhaustive explanations yet. In the presentation, we'll discuss a departure from self-similar development of the wave process which is accompanied with apparent sub-sonic wave propagation, changes of shape of elastic precursor wave as a result of variations in the material structure and the temperature, unexpected peculiarities of reflection of elastic-plastic waves from free surface, effects of internal friction at shock compression of glasses and some other effects. It seems the experimental data contain more information about kinetics of the time-dependent phenomena than we are able to get from their analysis now. Financial support from the Russian Science Foundation via Grant No 14-12-01127 is gratefully acknowledged.
Sensitivity of the resonant ultrasound spectroscopy to weak gradients of elastic properties.
Seiner, Hanuš; Sedlák, Petr; Bodnárová, Lucie; Kruisová, Alena; Landa, Michal; de Pablos, Angel; Belmonte, Manuel
2012-05-01
The applicability of resonant ultrasound spectroscopy on materials with weak spatial gradients in elastic coefficients and density is analyzed. It is shown that such gradients do not affect measurably the resonant spectrum but have a significant impact on the modal shapes. A numerical inverse procedure is proposed to explore the possibility of reconstructing the gradients from experimentally obtained modal shapes. This procedure is tested on synthetic data and applied to determine the gradient of the shear modulus in a continuously graded silicon nitride ceramic material. The results are in a good agreement with the gradient calculated for the examined material theoretically as well as with the results of other experimental methods. PMID:22559353
Lin, Jung-Fu; Liu, Jin; Jacobs, Caleb; Prakapenka, Vitali B.
2012-05-10
Ferromagnesite [(Mg,Fe)CO{sub 3}] has been proposed as a candidate host mineral for carbon in the Earth's mantle. Studying its physical and chemical properties at relevant pressures and temperatures helps our understanding of deep-carbon storage in the planet's interior and on its surface. Here we have studied high-pressure vibrational and elastic properties of magnesian siderite [(Mg{sub 0.35}Fe{sub 0.65})CO{sub 3}] across the electronic spin transition by Raman and X-ray diffraction spectroscopies in a diamond-anvil cell. Our results show an increase in Raman shift of the observed lattice modes of magnesian siderite across the spin transition at 45 GPa as a result of an {approx}8% unit-cell volume collapse and a 10% stiffer lattice (higher bulk modulus). C-O bond lengthening in the strong, rigid (CO{sub 3}){sup 2-} unit across the spin transition contributes to a competitive decrease in Raman shift, most evident in the Raman shift decrease of the symmetric stretching mode. Combined vibrational and elastic results are used to derive the mode Grueneisen parameter of each mode, which drops significantly across the transition. These results suggest that the low-spin state has distinctive vibrational and elastic properties compared to the high-spin state. Analyses of all recent experimental results on the (Mg,Fe)CO{sub 3} system show no appreciable compositional effect on the transition pressure, indicating weak iron-iron exchange interactions. Our results provide new insight into understanding the effects of the spin transition on the vibrational, elastic, and thermodynamic properties of (Mg,Fe)CO{sub 3} as a candidate carbon-host in the deep mantle.
Sheleg, A.U.; Shesholko, E.V.
1995-07-01
In this work, the authors studied the effect of {gamma}-radiation on the elastic properties of TlInS{sub 2} in the range 140-240 K (including the existence region of this incommensurate phase), on ultrasound velocity in TGS crystals in the vicinity of the ferroelectric transition, and on the ultrasound velocity in Rb{sub 2}ZnBr{sub 4} crystals near the incommensurate-to-commensurate phase transition.
Prediction of natural frequency variability due to uncertainty in material properties
NASA Technical Reports Server (NTRS)
Li, Y. W.
1994-01-01
Composite materials are widely used in various types of modern engineering structures. Traditional studies on composite structures have been based on the assumption that the material properties of the composites are characterized by a priori known elastic moduli, and no uncertainties of these moduli have been considered. However, the composite materials are invariably subject to a certain amount of scatter in their measured elastic moduli. To a large extent, the properties of composite materials are dependent on the fabrication process. But even the composite materials manufactured by the same process demonstrate differences in their elastic properties. This paper proposes a new, non-probabilistic method to predict the variability in the natural frequencies of the composite cylindrical shell, resulting from the unavoidable scatter in elastic moduli. The available measurements of elastic moduli are fitted by the four-dimensional uncertainty ellipsoid. The upper and lower bounds of the natural frequency are derived. With these bounds, designers will have a better understanding of the real dynamic behavior of the structure.
Properties of a glass-ionomer/resin-composite hybrid material.
Mathis, R S; Ferracane, J L
1989-09-01
A small percentage of the liquid resin used in commercial dental composites was added to the liquid used in a commercial glass-ionomer restorative in order to produce a fluoride-containing hybrid restorative-type material that would adhere to dentin while being stronger, less brittle, and less sensitive to desiccation in the oral cavity than glass ionomer. Compressive strength, yield strength, elastic modulus, fracture toughness, and tensile strength were analyzed for this hybrid, light-cured material. In addition, the solubility in water, adhesion to dentin, and surface roughness were also examined in vitro. The results suggest that the early (one-hour) mechanical properties of the hybrid material exceed those of glass ionomer. In addition, the brittleness and solubility of the material are less than those of commercial glass ionomer, while adhesion to dentin is unaffected. Most importantly, surface crazing, a documented problem with some glass ionomers when they become desiccated, is alleviated with this hybrid formulation. PMID:2638281
Jahan, Ali; Arumugam, Manohar; Hassan, Mohd Roshdi
2013-01-01
Contact pressure in the knee joint is a key element in the mechanisms of knee pain and osteoarthritis. Assessing the contact pressure in tibiofemoral joint is a challenging mechanical problem due to uncertainty in material properties. In this study, a sensitivity analysis of tibiofemoral peak contact pressure to the material properties of the soft tissue was carried out through fractional factorial and Box-Behnken designs. The cartilage was modeled as linear elastic material, and in addition to its elastic modulus, interaction effects of soft tissue material properties were added compared to previous research. The results indicated that elastic modulus of the cartilage is the most effective factor. Interaction effects of axial/radial modulus with elastic modulus of cartilage, circumferential and axial/radial moduli of meniscus were other influential factors. Furthermore this study showed how design of experiment methods can help designers to reduce the number of finite element analyses and to better interpret the results. PMID:27006925
Outstanding mechanical properties of monolayer MoS2 and its application in elastic energy storage.
Peng, Qing; De, Suvranu
2013-11-28
The structural and mechanical properties of graphene-like honeycomb monolayer structures of MoS2 (g-MoS2) under various large strains are investigated using density functional theory (DFT). g-MoS2 is mechanically stable and can sustain extra large strains: the ultimate strains are 0.24, 0.37, and 0.26 for armchair, zigzag, and biaxial deformation, respectively. The in-plane stiffness is as high as 120 N m(-1) (184 GPa equivalently). The third, fourth, and fifth order elastic constants are indispensable for accurate modeling of the mechanical properties under strains larger than 0.04, 0.07, and 0.13 respectively. The second order elastic constants, including in-plane stiffness, are predicted to monotonically increase with pressure while the Poisson ratio monotonically decreases with increasing pressure. With the prominent mechanical properties including large ultimate strains and in-plane stiffness, g-MoS2 is a promising candidate of elastic energy storage for clean energy. It possesses a theoretical energy storage capacity as high as 8.8 MJ L(-1) and 1.7 MJ kg(-1), or 476 W h kg(-1), larger than a Li-ion battery and is environmentally friendly. PMID:24126736
Monteseguro, V.; Rodríguez-Hernández, P.; Muñoz, A.
2015-12-28
The structural, elastic, and vibrational properties of yttrium aluminum garnet Y{sub 3}Al{sub 5}O{sub 12} are studied under high pressure by ab initio calculations in the framework of the density functional theory. The calculated ground state properties are in good agreement with the available experimental data. Pressure dependences of bond length and bulk moduli of the constituent polyhedra are reported. The evolution of the elastic constants and the major elastic properties, Young and shear modulus, Poisson's ratios, and Zener anisotropy ratio, are described. The mechanical stability is analyzed, on the light of “Born generalized stability criteria,” showing that the garnet is mechanically unstable above 116 GPa. Symmetries, frequencies, and pressure coefficients of the Raman-active modes are discussed on the basis of the calculated total and partial phonon density of states, which reflect the dynamical contribution of each atom. The relations between the phonon modes of Y{sub 3}Al{sub 5}O{sub 12} and the internal and external molecular modes of the different polyhedra are discussed. Infrared-active modes, as well as the silent modes, and their pressure dependence are also investigated. No dynamical instabilities were found below 116 GPa.
Outstanding mechanical properties of monolayer MoS2 and its application in elastic energy storage
NASA Astrophysics Data System (ADS)
Peng, Qing; de, Suvranu
2014-03-01
The structural and mechanical properties of graphene-like honeycomb monolayer structures of MoS2(g-MoS2) under various large strains are investigated using density functional theory (DFT). g-MoS2 is mechanically stable and can sustain extra large strains: the ultimate strains are 0.24, 0.37, and 0.26 for armchair, zigzag, and biaxial deformation, respectively. The in-plane stiffness is as high as 120 N/m (184 GPa equivalently). The third, fourth, and fifth order elastic constants are indispensable for accurate modeling of the mechanical properties under strains larger than 0.04, 0.07, and 0.13 respectively. The second order elastic constants, including in-plane stiffness, are predicted to monotonically increase with pressure while the Poisson ratio monotonically decreases with increasing pressure. With the prominent mechanical properties including large ultimate strains and in-plane stiffness, g-MoS2 is a promising candidate of elastic energy storage for clean energy. It possesses a theoretical energy storage capacity as high as 8.8 MJ/L and 1.7 MJ/kg, or 476 Wh/kg, larger than a Li-ion battery and is environmentally friendly. Financial support from the Defence Threat Reduction Agency (DTRA) Grant # BRBAA08-C-2-0130 and.
Determination of elastic moduli of thin layers of soft material using the atomic force microscope.
Dimitriadis, Emilios K; Horkay, Ferenc; Maresca, Julia; Kachar, Bechara; Chadwick, Richard S
2002-01-01
We address three problems that limit the use of the atomic force microscope when measuring elastic moduli of soft materials at microscopic scales. The first concerns the use of sharp cantilever tips, which typically induce local strains that far exceed the linear material regime. We show that this problem can be alleviated by using microspheres as probes, and we establish the criteria for their use. The second relates to the common use of the Hertz contact mechanics model, which leads to significant errors when applied to thin samples. We develop novel, simple to use corrections to apply for such cases. Samples that are either bonded or not bonded to a rigid substrate are considered. The third problem concerns the difficulty in establishing when contact occurs on a soft material. We obtain error estimates for the elastic modulus resulting from such uncertainty and discuss the sensitivity of the estimation methods to error in contact point. The theoretical and experimental results are compared to macroscopic measurements on poly(vinyl-alcohol) gels. PMID:11964265
Morozov, Ilya A; Mamaev, Alexander S; Osorgina, Irina V; Lemkina, Larisa M; Korobov, Vladimir P; Belyaev, Anton Yu; Porozova, Svetlana E; Sherban, Marina G
2016-05-01
The surface of elastic polyurethane treated by plasma immersion N2(+) ion implantation at different fluences has been investigated. A folded surface structure is observed in all cases. Analysis has been performed to study the structural (roughness, steepness and fraction of folds, fractal characteristics), mechanical (stiffness, adhesion force between the AFM probe and the material) and wetting properties of surfaces. Under uniaxial stretching the cracks orthogonal to the axis of deformation and longitudinal folds are formed on the examined surfaces. After unloading the initial structure of the surface of deformed materials exposed to low fluences becomes smoother and does not recover, i.e. it has plastic properties. By contrast, the structure of the surfaces of materials subjected to high-fluence treatment recovers without visible changes and the cracks are fully closed. The study of Staphylococcus colonies grown on these materials has demonstrated significant reduction (from 3 to 5 times) in the vitality of bacteria on treated surfaces. This result was repeated on samples after 11months of storage. Such antibacterial properties are primarily related to the structural changes of the surfaces accompanied by the increased hydrophilicity. PMID:26952420
NASA Astrophysics Data System (ADS)
Zerr, A.; Kuriakose, M.; Raetz, S.; Chigarev, N.; Nikitin, S. M.; Gasteau, D.; Tournat, V.; Bulou, A.; Castagnede, B.; Gusev, V. E.; Lomonosov, A.
2015-12-01
In picosecond ultrasonic interferometry [1], femto- or picosecond pump laser pulses are first used to generate acoustic pulses ranging from several to a few tens of nanometres length, thanks to the optoacoustic transduction in a light absorbing generator. Time-delayed femto- or picosecond probe laser pulses are then used to follow the propagation of these ultrashort acoustic pulses through a transparent medium that is in contact with the generator surface. The transient signal thus contains, at each moment in time, information on the local elastic, optical and elasto-optical properties of the tested material at the position where the laser-generated picosecond acoustic pulse is located during its propagation in the sample depth. Hence, the technique allows evaluation of sound velocities and elastic anisotropy of micro-crystallites composing a transparent material compressed to high pressures in a diamond anvil cell (DAC). This interferometry technique also helps to understand the micro-crystallite orientations in a case of elastically anisotropic material. Here we report the preliminary results of picosecond ultrasonic interferometry applied to the evaluation of homogeneities and elastic properties of polycrystalline solid argon compressed to 10 GPa and 15 GPa. In comparison with the earlier reported experiments on H2O ice at Mbar pressures [2], more efforts were spent to the evaluation of the lateral microstructure of the sample at high pressures, i.e., to inhomogeneities along the surface of the optoacoustic generator, rather than to the in-depth imaging along the axis of the DAC. The lateral imaging is performed over a distance of 60 - 90 µm, nearly corresponding to the complete sample diameter. In addition to the presence of expected lateral inhomogeneities the obtained results demonstrate important changes in their distribution upon pressure increase from 10 to 15 GPa. On the basis of the analysis of the statistic probability in the detection of differently
The Effect of VMoS3 Point Defect on the Elastic Properties of Monolayer MoS2 with REBO Potentials
NASA Astrophysics Data System (ADS)
Li, Minglin; Wan, Yaling; Tu, Liping; Yang, Yingchao; Lou, Jun
2016-03-01
Structural defects in monolayer molybdenum disulfide (MoS2) have significant influence on the electric, optical, thermal, chemical, and mechanical properties of the material. Among all the types of structural defects of the chemical vapor phase-grown monolayer MoS2, the VMoS3 point defect (a vacancy complex of Mo and three nearby S atoms) is another type of defect preferentially generated by the extended electron irradiation. Here, using the classical molecular dynamics simulation with reactive empirical bond-order (REBO) potential, we first investigate the effect of VMoS3 point defects on the elastic properties of monolayer MoS2 sheets. Under the constrained uniaxial tensile test, the elastic properties of monolayer MoS2 sheets containing VMoS3 vacancies with defect fraction varying from 0.01 to 0.1 are obtained based on the plane anisotropic constitutive relations of the material. It is found that the increase of VMoS3 vacancy concentration leads to the noticeable decrease in the elastic modulus but has a slight effect on Poisson's ratio. The maximum decrease of the elastic modulus is up to 25 %. Increasing the ambient temperature from 10 K to 500 K has trivial influences on the elastic modulus and Poisson's ratio for the monolayer MoS2 without defect and with 5 % VMoS3 vacancies. However, an anomalous parabolic relationship between the elastic modulus and the temperature is found in the monolayer MoS2 containing 0.1 % VMoS3 vacancy, bringing a crucial and fundamental issue to the application of monolayer MoS2 with defects.
The Effect of VMoS3 Point Defect on the Elastic Properties of Monolayer MoS2 with REBO Potentials.
Li, Minglin; Wan, Yaling; Tu, Liping; Yang, Yingchao; Lou, Jun
2016-12-01
Structural defects in monolayer molybdenum disulfide (MoS2) have significant influence on the electric, optical, thermal, chemical, and mechanical properties of the material. Among all the types of structural defects of the chemical vapor phase-grown monolayer MoS2, the VMoS3 point defect (a vacancy complex of Mo and three nearby S atoms) is another type of defect preferentially generated by the extended electron irradiation. Here, using the classical molecular dynamics simulation with reactive empirical bond-order (REBO) potential, we first investigate the effect of VMoS3 point defects on the elastic properties of monolayer MoS2 sheets. Under the constrained uniaxial tensile test, the elastic properties of monolayer MoS2 sheets containing VMoS3 vacancies with defect fraction varying from 0.01 to 0.1 are obtained based on the plane anisotropic constitutive relations of the material. It is found that the increase of VMoS3 vacancy concentration leads to the noticeable decrease in the elastic modulus but has a slight effect on Poisson's ratio. The maximum decrease of the elastic modulus is up to 25 %. Increasing the ambient temperature from 10 K to 500 K has trivial influences on the elastic modulus and Poisson's ratio for the monolayer MoS2 without defect and with 5 % VMoS3 vacancies. However, an anomalous parabolic relationship between the elastic modulus and the temperature is found in the monolayer MoS2 containing 0.1 % VMoS3 vacancy, bringing a crucial and fundamental issue to the application of monolayer MoS2 with defects. PMID:27000023
Tooth and bone deformation: structure and material properties by ESPI
NASA Astrophysics Data System (ADS)
Zaslansky, Paul; Shahar, Ron; Barak, Meir M.; Friesem, Asher A.; Weiner, Steve
2006-08-01
In order to understand complex-hierarchical biomaterials such as bones and teeth, it is necessary to relate their structure and mechanical-properties. We have adapted electronic speckle pattern-correlation interferometry (ESPI) to make measurements of deformation of small water-immersed specimens of teeth and bones. By combining full-field ESPI with precision mechanical loading we mapped sub-micron displacements and determined material-properties of the samples. By gradually and elastically compressing the samples, we compensate for poor S/N-ratios and displacement differences of about 100nm were reliably determined along samples just 2~3mm long. We produced stress-strain curves well within the elastic performance range of these materials under biologically relevant conditions. For human tooth-dentin, Young's modulus in inter-dental areas of the root is 40% higher than on the outer sides. For cubic equine bone samples the compression modulus of axial orientations is about double the modulus of radial and tangential orientations (20 GPa versus 10 GPa respectively). Furthermore, we measured and reproduced a surprisingly low Poisson's ratio, which averaged about 0.1. Thus the non-contact and non-destructive measurements by ESPI produce high sensitivity analyses of mechanical properties of mineralized tissues. This paves the way for mapping deformation-differences of various regions of bones, teeth and other biomaterials.
Property Data Summaries for Advanced Materials
National Institute of Standards and Technology Data Gateway
SRD 150 NIST Property Data Summaries for Advanced Materials (Web, free access) Property Data Summaries are topical collections of property values derived from surveys of published data. Thermal, mechanical, structural, and chemical properties are included in the collections.
NIST Materials Properties Databases for Advanced Ceramics
Munro, R. G.
2001-01-01
The NIST Ceramics Division maintains two databases on the physical, mechanical, thermal, and other properties of high temperature superconductors and structural ceramics. Crystallographic data are featured prominently among the physical property data and serve several important functions in the classification and evaluation of the property values. The scope of materials, properties, and data evaluation protocols are discussed for the two databases.
NASA Astrophysics Data System (ADS)
Saadaoui, Fatiha; Driss Khodja, Fatima Zohra; Kadoun, Abd-Ed-Daïm; Driss Khodja, Mohammed; Elias, Abdelkader; Boudali, Abdelkader
2015-12-01
We have performed first-principles calculations of structural, elastic, thermodynamic, and electronic properties of anti-perovskites AIIICNi3 (AIII = Al, Ga, In), by using the full-potential linearized augmented plane wave (FP-LAPW) method combined with the quasi-harmonic Debye model. We carried out our calculations within the local density approximation (LDA) and the generalized gradient approximation (GGA-PBE and GGA-PBEsol functionals). Our results constitute interesting first predictions in the case of many elastic parameters of the anti-perovskites AIIICNi3, among them elastic parameters of AlCNi3 and GaCNi3 and some polycrystalline elastic parameters of InCNi3. We also report for the first time calculated values, at ambient conditions, of Grüneisen parameter, thermal expansion coefficient, specific heat at constant pressure, specific heat at constant volume, isothermal bulk modulus, and adiabatic bulk modulus for AlCNi3, GaCNi3, and InCNi3. Band structure, total and partial densities of states, and charge density have been obtained and analyzed. Electronic structure results show metallic behavior for the three compounds. Ni 3 d states play dominant role near the Fermi level and there is a strong hybridization between Ni 3 d and C 2 p states. In addition, as AIIICNi3 synthesized samples are expected to be carbon-deficient, we calculated structural, elastic, and thermodynamic properties of sub-stoichiometric AlC x Ni3 materials.
NASA Astrophysics Data System (ADS)
Tian, T.; Wang, X. F.; Li, W.
2013-03-01
As high-temperature structural materials, L12 intermetallic compounds have attracted the strong interest from both fundamental and industrial aspects. Understanding of elastic property is a basis for the complete investigations of mechanical behavior of L12 alloys. In an effort to explore the electronic origin of elastic properties of L12 intermetallics, we have performed a systematic study on elastic constants for single crystals, and Young's modulus, shear modulus, bulk modulus and Poisson's ratio for poly-crystals of 22 known Al3X and X3Al-type (X=transition or main group metal) intermetallics using the ab initio calculations. Based on the calculations of elastic constants and extreme (both positive and negative) Poisson's ratios, we found a pronounced correlation between the extreme Poisson's ratio and the elastic anisotropy, i.e., approximate 40% of the investigated L12 intermetallics exhibit intrinsic auxetic behavior. Furthermore, based on the distribution of bonding charge densities, we revealed that the ductility and extreme Poisson's ratios were attributable to the directionality of bonds of these alloys. Our findings provide a new method to predict mechanical behavior of intermetallics.
Dynamic material properties of refractory materials: Tantalum and tantalum/tungsten alloys
Furnish, M.D.; Chhabildas, L.C.; Lassila, D.H.; Steinberg, D.J.
1995-08-01
We have made a careful set of impact wave-profile measurements (16 profiles) on tantalum and tantalum-tungsten alloys at relatively low stresses (to 15 GPa). Alloys used were Ta{sub 97.5}W{sub 2.5} and Ta{sub 90}W{sub 10} (wt. %) with oxygen contents of 30--70 ppM. Information available from these experiments includes Hugoniot, elastic limits, loading fates, spall strength, unloading paths, reshock structure and specimen thickness effects. Hugoniot and spall properties are illustrated, and are consistent with expectations from earlier work. Modeling the tests with the Steinberg-Lund rate-dependent material model provides for an excellent match of the shape of the plastic wave, although the release wave is not well modeled. There is also a discrepancy between experiments and calculations regarding the relative timing of the elastic and plastic waves that may be due to texture effects.
The effect of iron on the elastic properties of ringwoodite at high pressure
NASA Astrophysics Data System (ADS)
Higo, Yuji; Inoue, Toru; Li, Baosheng; Irifune, Tetsuo; Liebermann, Robert C.
2006-12-01
Elastic wave velocities of ringwoodite with compositions of Mg 2SiO 4, (Mg 0.8Fe 0.2) 2SiO 4 and (Mg 0.5Fe 0.5) 2SiO 4 have been measured to address the effect of iron on the elastic properties of silicate spinel under high pressure. Ultrasonic measurements on specimens produced by hot-pressing at about 19 GPa and at 1200 °C were conducted at pressures up to 14 GPa at room temperature in a multianvil apparatus. Pressure was estimated from a relationship between the travel time in an Al 2O 3 buffer rod and the pressure estimated from in situ X-ray diffraction measurements. Thus, measured bulk modulus ( K) of ringwoodite slightly increases with increasing iron content, while the pressure derivative of the bulk modulus remains virtually the same ( K' = 4.4 for XFe = Fe/(Fe + Mg) = 0-0.5). In contrast, the shear modulus ( G) decreases significantly with increasing iron content, while the pressure derivative of the shear modulus slightly decreases or remains almost unchanged ( G' = 1.4-1.0 for XFe = 0-0.5). The effects of iron content on the elastic moduli are somewhat different from those of an earlier study using Brillion scattering method, but are consistent with the elastic moduli of the Fe 2SiO 4 end-member measured in a piston-cylinder apparatus using ultrasonic interferometry. The effects of iron on the elastic moduli of ringwoodite are described as K = 184(1) + 16(1) XFe (GPa) and G = 124(2) - 45(3) XFe (GPa), by combining the present and earlier results based on the ultrasonic interferometry at high pressure. The present result suggests that the temperature anomalies, rather than the variations of iron content in ringwoodite, are more likely causes for the observed variations in seismic velocities in the mantle transition region.
The Effect of Iron on the Elastic Properties of Ringwoodite at High Pressure
Higo,Y.; Inoue, T.; Li, B.; Irifune, T.; Liebermann, R.
2006-01-01
Elastic wave velocities of ringwoodite with compositions of Mg2SiO4, (Mg0.8Fe0.2)2SiO4 and (Mg0.5Fe0.5)2SiO4 have been measured to address the effect of iron on the elastic properties of silicate spinel under high pressure. Ultrasonic measurements on specimens produced by hot-pressing at about 19 GPa and at 1200 C were conducted at pressures up to 14 GPa at room temperature in a multianvil apparatus. Pressure was estimated from a relationship between the travel time in an Al2O3 buffer rod and the pressure estimated from in situ X-ray diffraction measurements. Thus, measured bulk modulus (K) of ringwoodite slightly increases with increasing iron content, while the pressure derivative of the bulk modulus remains virtually the same (K' = 4.4 for XFe = Fe/(Fe + Mg) = 0-0.5). In contrast, the shear modulus (G) decreases significantly with increasing iron content, while the pressure derivative of the shear modulus slightly decreases or remains almost unchanged (G' = 1.4-1.0 for XFe = 0-0.5). The effects of iron content on the elastic moduli are somewhat different from those of an earlier study using Brillion scattering method, but are consistent with the elastic moduli of the Fe2SiO4 end-member measured in a piston-cylinder apparatus using ultrasonic interferometry. The effects of iron on the elastic moduli of ringwoodite are described as K = 184(1) + 16(1)XFe (GPa) and G = 124(2) - 45(3)XFe (GPa), by combining the present and earlier results based on the ultrasonic interferometry at high pressure. The present result suggests that the temperature anomalies, rather than the variations of iron content in ringwoodite, are more likely causes for the observed variations in seismic velocities in the mantle transition region.
NASA Astrophysics Data System (ADS)
Tsuchiya, J.; Tsuchiya, T.
2011-12-01
Serpentine is formed by reaction between peridotite and water which is released from hydrous mineral in subducting slab under pressure. Partially serpentinized peridotite may be a significant reservoir for water in the subducted cold slab and is considered to play an important role in subduction zone processes such as generation of arc magmatism. Precise determination of structure, vibrational and elastic properties of serpentine become the basis for understanding the transporting processes of water into deep Earth interior. Here we investigate by first principles calculation, the detailed structures, vibrational and elastic properties of lizardite, chlorite, and antigorite which are major hydrous minerals in the serpentinized peridotite. We found a very sudden softening of the elastic constants at high pressure condition. This anomaly is associated with a slight change in the compressibility of the c axis which corresponds to the layer normal direction. The calculated OH stretching frequencies also increase suddenly associated with the anomaly and these vibrational behaviors are consistent with the previous Raman measurements. Since other hydrous phyllosilicates such as clay minerals, and mica have similar crystal structures to these hydrous minerals, these anomalous softening is also expected in these minerals under pressure. Research supported in part by special coordination funds for promoting science and technology (Supporting Young Researchers with Fixed-term Appointments) and Grants-In-Aid for Scientific Research from the Japan Society for the Promotion of Science (Nos. 21740380, 20103005, and 24740357).
First-principles study of structural, elastic, and thermodynamic properties of ZrHf alloy
NASA Astrophysics Data System (ADS)
Wei, Zhao; Zhai, Dong; Shao, Xiao-Hong; Lu, Yong; Zhang, Ping
2015-04-01
Structural parameters, elastic constants, and thermodynamic properties of ordered and disordered solid solutions of ZrHf alloys are investigated through first-principles calculations based on density-functional theory (DFT). The special quasi-random structure (SQS) method is used to model the disordered phase as a single unit cell, and two lamella structures are generated to model the ordered alloys. Small strains are applied to the unit cells to measure the elastic behavior and mechanical stability of ZrHf alloys and to obtain the independent elastic constants by the stress-strain relationship. Phonon dispersions and phonon density of states are presented to verify the thermodynamic stability of the considered phases. Our results show that both the ordered and disordered phases of ZrHf alloys are structurally stable. Based on the obtained phonon frequencies, thermodynamic properties, including Gibbs free energy, entropy, and heat capacity, are predicted within the quasi-harmonic approximation. It is verified that there are no obvious differences in energy between ordered and disordered phases over a wide temperature range. Project supported by the National Natural Science Foundation of China (Grant No. 51102009) and the Long-Term Subsidy Mechanism from the Ministry of Finance and the Ministry of Education of China.
Electronic structure, phase transition, and elastic properties of ScC under high pressure
NASA Astrophysics Data System (ADS)
Zhao, Yu-Xin; Zhu, Jun; Hao, Yan-Jun; Li, Zi-Yuan; Chen, Long-Qing; Ji, Guang-Fu
2015-12-01
The structural properties and the phase transition for scandium carbide (ScC) have been studied in NaCl (B1), CsCl (B2), ZB (B3), WZ (B4), NiAs (B81), WC (B h ), and Pmmn structures by using the pseudopotential plane-wave method in the framework of the density functional theory. Our theoretical results show that the most stable structure is the B1 phase, contrary to the result of Rahim et al. The phase transitions B1 → Pmmn and Pmmn → B2 are predicted at 83.7 and 109.7 GPa, respectively. At the same time, we find that the B3, B4, B81, and B h phases are not stable over the whole pressure range considered. In particular, the elastic constants of Pmmn-ScC under high pressure are obtained successfully. The effects of pressure on the elastic properties of B1-ScC and Pmmn-ScC are also predicted. The Debye temperatures Θ and the sound velocities of these two structures are estimated from the elastic constants, and by analyzing G/ B, the brittle-ductile behavior of ScC is assessed. In addition, the density of states of B1-ScC at high pressures is also discussed.
Topology of charge density and elastic properties of Ti3SiC2 polymorphs
Yu, Rong; Zhang, Xiao Feng; He, Lian Long; Ye, Heng Qiang
2004-06-24
Using an all-electron, full potential first-principles method, we have investigated the topology of charge density and elastic properties of the two polymorphs, alpha and beta, of Ti3SiC2. The bonding effect was analyzed based on Bader's quantum theory of ''atoms in molecules'' (AIM). It was found that the Ti-Si bonding effect is significantly weaker in beta than in alpha, giving less stabilizing effect for beta. The Si-C bonds, which are absent in alpha, are formed in beta and provide additional stabilizing effect for beta. In contrast to conventional thinking, there is no direction interaction between Ti atoms in both alpha and beta. The calculated elastic properties are in good agreement with the experimental results, giving the bulk modulus of about 180 GPa and the Poisson's ratio of 0.2. The beta phase is generally softer than the alpha phase. As revealed by the direction dependent Young's modulus, there is only slight elastic anisotropy in Ti3SiC2. For alpha, Young's modulus is minimum in the c direction and maximum in the directions 42o from c. For beta, the maximum lies in the c direction, in part due to the formation of Si-C bonds in this direction.
NASA Astrophysics Data System (ADS)
Andreaus, Ugo; Giorgio, Ivan; Madeo, Angela
2015-02-01
In this paper, a continuum mixture model with evolving mass densities and porosity is proposed to describe the process of bone remodeling in the presence of bio-resorbable materials as driven by externally applied loads. From a mechanical point of view, both bone tissue and biomaterial are modeled as linear elastic media with voids in the sense of Cowin and Nunziato (J Elast 13:125-147, 1983). In the proposed continuum model, the change of volume fraction related to the void volume is directly accounted for by considering porosity as an independent kinematical field. The bio-mechanical coupling is ensured by the introduction of a suitable stimulus which allows for discriminating between resorption (of both bone and biomaterial) and synthesis (of the sole natural bone) depending on the level of externally applied loads. The presence of a `lazy zone' associated with intermediate deformation levels is also considered in which neither resorption nor synthesis occur. Some numerical solutions of the integro-differential equations associated with the proposed model are provided for the two-dimensional case. Ranges of values of the parameters for which different percentages of biomaterial substitution occur are proposed, namely parameters characterizing initial and maximum values of mass densities of bone tissue and of the bio-resorbable material.
Sun, Qicheng; Jin, Feng; Wang, Guangqian; Song, Shixiong; Zhang, Guohua
2015-01-01
Mesoscopic structures form in dense granular materials due to the self-organisation of the constituent particles. These structures have internal structural degrees of freedom in addition to the translational degree of freedom. The resultant granular elasticity, which exhibits intrinsic variations and inevitable relaxation, is a key quantity that accounts for macroscopic solid- or fluid-like properties and the transitions between them. In this work, we propose a potential energy landscape (PEL) with local stable basins and low elastic energy barriers to analyse the nature of granular elasticity. A function for the elastic energy density is proposed for stable states and is further calibrated with ultrasonic measurements. Fluctuations in the elastic energy due to the evolution of internal structures are proposed to describe a so-called configuration temperature Tc as a counterpart of the classical kinetic granular temperature Tk that is attributed to the translational degrees of freedom. The two granular temperatures are chosen as the state variables, and a fundamental equation is established to develop non-equilibrium thermodynamics for granular materials. Due to the relatively low elastic energy barrier in the PEL, granular elasticity relaxes more under common mechanical loadings, and a simple model based on mean-field theory is developed to account for this behaviour. PMID:25951049
Lu, Jinwen; Zhao, Yongqing; Niu, Hongzhi; Zhang, Yusheng; Du, Yuzhou; Zhang, Wei; Huo, Wangtu
2016-05-01
The present study is to investigate the microstructural characteristics, electrochemical corrosion behavior and elasticity properties of Ti-6Al-xFe alloys with Fe addition for biomedical application, and Ti-6Al-4V alloy with two-phase (α+β) microstructure is also studied as a comparison. Microstructural characterization reveals that the phase and crystal structure are sensitive to the Fe content. Ti-6Al alloy displays feather-like hexagonal α phase, and Ti-6Al-1Fe exhibits coarse lath structure of hexagonal α phase and a small amount of β phase. Ti-6Al-2Fe and Ti-6Al-4Fe alloys are dominated by elongated, equiaxed α phase and retained β phase, but the size of α phase particle in Ti-6Al-4Fe alloy is much smaller than that in Ti-6Al-2Fe alloy. The corrosion resistance of these alloys is determined in SBF solution at 37 °C. It is found that the alloys spontaneously form a passive oxide film on their surface after immersion for 500 s, and then they are stable for polarizations up to 0 VSCE. In comparison with Ti-6Al and Ti-6Al-4V alloys, Ti-6Al-xFe alloys exhibit better corrosion resistance with lower anodic current densities, larger polarization resistances and higher open-circuit potentials. The passive layers show stable characteristics, and the wide frequency ranges displaying capacitive characteristics occur for high iron contents. Elasticity experiments are performed to evaluate the elasticity property at room temperature. Ti-6Al-4Fe alloy has the lowest Young's modulus (112 GPa) and exhibits the highest strength/modulus ratios as large as 8.6, which is similar to that of c.p. Ti (8.5). These characteristics of Ti-6Al-xFe alloys form the basis of a great potential to be used as biomedical implantation materials. PMID:26952395
Correlation of materials properties with the atomic density concept
NASA Technical Reports Server (NTRS)
1975-01-01
Based on the hypothesis that the number of atoms per unit volume, accurately calculable for any substance of known real density and chemical composition, various characterizing parameters (energy levels of electrons interacting among atoms of the same or different kinds, atomic mass, bond intensity) were chosen for study. A multiple exponential equation was derived to express the relationship. Various properties were examined, and correlated with the various parameters. Some of the properties considered were: (1) heat of atomization, (2) boiling point, (3) melting point, (4) shear elastic modulus of cubic crystals, (5) thermal conductivity, and (6) refractive index for transparent substances. The solid elements and alkali halides were the materials studied. It is concluded that the number of different properties can quantitively be described by a common group of parameters for the solid elements, and a wide variety of compounds.
Elastic properties and line tension of self-assembled bilayer membranes.
Li, Jianfeng; Pastor, Kyle A; Shi, An-Chang; Schmid, Friederike; Zhou, Jiajia
2013-07-01
The elastic properties of a self-assembled bilayer membrane are studied using the self-consistent field theory, applied to a model system composed of flexible amphiphilic chains dissolved in hydrophilic polymeric solvents. Examining the free energy of bilayer membranes with different geometries allows us to calculate their bending modulus, Gaussian modulus, two fourth-order membrane moduli, and the line tension. The dependence of these parameters on the microscopic characteristics of the amphiphilic chain, characterized by the volume fraction of the hydrophilic component, is systematically studied. The theoretical predictions are compared with the results from a simple monolayer model, which approximates a bilayer membrane by two monolayers. The region of validity of the linear elasticity theory is analyzed by examining the higher-order contributions. PMID:23944501
Elastic properties and line tension of self-assembled bilayer membranes
NASA Astrophysics Data System (ADS)
Li, Jianfeng; Pastor, Kyle A.; Shi, An-Chang; Schmid, Friederike; Zhou, Jiajia
2013-07-01
The elastic properties of a self-assembled bilayer membrane are studied using the self-consistent field theory, applied to a model system composed of flexible amphiphilic chains dissolved in hydrophilic polymeric solvents. Examining the free energy of bilayer membranes with different geometries allows us to calculate their bending modulus, Gaussian modulus, two fourth-order membrane moduli, and the line tension. The dependence of these parameters on the microscopic characteristics of the amphiphilic chain, characterized by the volume fraction of the hydrophilic component, is systematically studied. The theoretical predictions are compared with the results from a simple monolayer model, which approximates a bilayer membrane by two monolayers. The region of validity of the linear elasticity theory is analyzed by examining the higher-order contributions.
NASA Astrophysics Data System (ADS)
Alexandrov, Y. V.; Batanova, A. A.; Gladkova, E. V.; Dyshlovenko, P. E.; Nagatkin, A. N.; Nizametdinov, A. F.
2016-02-01
Two-dimensional charge-stabilized colloidal crystal with a hexagonal crystal lattice and constant electric potential on the particles is studied numerically. The properties of the crystal are described by the theory based on the Poisson-Boltzmann non-linear differential equation. The force constants and the equilibrium pressure in the crystals are calculated for a broad range of the lattice parameters. The numerical procedures of the force constant and pressure determination is briefly described. Elastic constants of the first and second order are also calculated on the base of the force constants to obtain information about the many-body effective interactions in the system. It was shown that the Cauchy relation between the elastic constants breaks down in the whole range of the lattice parameter especially at higher densities. This can be interpreted as an effect of the many-body effective interaction between the particles in the crystal.
Measurement of material properties of 6000 Al-sheet for car body application using thermal imaging
Schleich, Ralf; Liewald, Mathias; Dillenz, Alexander
2007-04-07
The paper presents experimental results of thermo-graphical measurement of material properties. The analytical expression for the temperature variation of the specimen deformed in the elastic state is determined starting from the first law of thermodynamics. The experimental method for determining material properties based on the Joule-Thompson effect is presented in detail. The thermo-graphical method has been used to determine formability in different state of stresses of the AA 6016-T4 aluminium alloys.
NASA Astrophysics Data System (ADS)
Goldenberg, C.; Tanguy, A.; Barrat, J.-L.
2007-10-01
We study the local disorder in the deformation of amorphous materials by decomposing the particle displacements into a continuous, inhomogeneous field and the corresponding fluctuations. We compare these fields to the commonly used non-affine displacements in an elastically deformed 2D Lennard-Jones glass. Unlike the non-affine field, the fluctuations are very localized, and exhibit a much smaller (and system size independent) correlation length, on the order of a particle diameter, supporting the applicability of the notion of local "defects" to such materials. We propose a scalar "noise" field to characterize the fluctuations, as an additional field for extended continuum models, e.g., to describe the localized irreversible events observed during plastic deformation.
Yan, Jia; Wu, Tianhao; Ding, Zezun; Li, Xiaokang
2016-01-20
Carbon nanotubes/chitosan (CNTs/CHI) composite foams with ordered lamellar structure were prepared by unidirectionally freezing a dispersion of CNTs in chitosan aqueous solution and subsequent freeze drying. The structure and thermal stability of the composite foams have been characterized by wide-angle X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy, and thermogravimetry analysis. And their elastic behaviors were investigated by cyclic compression tests. The produced CNTs/CHI composite foams have better recoverability and improved elastic properties compared with the pure chitosan foams. Freezing rate, fraction of CNTs and density are the important factors affecting on the micro morphology, elasticity and mechanical strength of CNTs/CHI composite foams. Due to less ice dendrites and thicker lamellas being formed under low freezing rate, the CNTs/CHI composite foams prepared under low freezing rate (6 mm min(-1)) possesses better mechanical properties than those prepared under high freezing rate (10 cm min(-1)). With the increasing CNTs fraction, the recovery ability of CNTs/CHI composite increases and achieves the maximum at a critical point, and then decreases dramatically due to the inadequate chitosan matrix and aggregation of CNTs. The critical point herein appears at the CNTs fraction ≥ 0.5 and ≥ 0.3, respectively, for the samples with density of 0.02 and 0.01 g cm(-3). The CNTs/CHI composite foams with high density (0.02 g cm(-3)) possess better elasticity and mechanical strength than the ones with low density (0.01 g cm(-3)). PMID:26572473
NASA Astrophysics Data System (ADS)
Jalilian, Jaafar; Motiepour, Pouria
2015-12-01
In a recent article by Ahmad et al. (2015) [1] structural, elastic, electronic, magnetic and optical properties of RbSrX (C, Si, Ge) half-Heusler compounds have been studied by the first principles calculations. After studying this article, we found that there are some physical and computational mistakes in electronic and optical properties sections. In investigating optical properties, they did not consider intraband transitions contribution in complex dielectric function term, while this term has significant effect on optical spectra for half-metallic materials.
Mechanical properties of low dimensional materials
NASA Astrophysics Data System (ADS)
Saini, Deepika
Recent advances in low dimensional materials (LDMs) have paved the way for unprecedented technological advancements. The drive to reduce the dimensions of electronics has compelled researchers to devise newer techniques to not only synthesize novel materials, but also tailor their properties. Although micro and nanomaterials have shown phenomenal electronic properties, their mechanical robustness and a thorough understanding of their structure-property relationship are critical for their use in practical applications. However, the challenges in probing these mechanical properties dramatically increase as their dimensions shrink, rendering the commonly used techniques inadequate. This dissertation focuses on developing techniques for accurate determination of elastic modulus of LDMs and their mechanical responses under tensile and shear stresses. Fibers with micron-sized diameters continuously undergo tensile and shear deformations through many phases of their processing and applications. Significant attention has been given to their tensile response and their structure-tensile properties relations are well understood, but the same cannot be said about their shear responses or the structure-shear properties. This is partly due to the lack of appropriate instruments that are capable of performing direct shear measurements. In an attempt to fill this void, this dissertation describes the design of an inexpensive tabletop instrument, referred to as the twister, which can measure the shear modulus (G) and other longitudinal shear properties of micron-sized individual fibers. An automated system applies a pre-determined twist to the fiber sample and measures the resulting torque using a sensitive optical detector. The accuracy of the instrument was verified by measuring G for high purity copper and tungsten fibers. Two industrially important fibers, IM7 carbon fiber and KevlarRTM 119, were found to have G = 17 and 2.4 GPa, respectively. In addition to measuring the shear
NASA Astrophysics Data System (ADS)
Rubin, M. B.; Vorobiev, O.; Vitali, E.
2016-07-01
A large deformation thermomechanical model is developed for shock loading of a material that can exhibit elastic and inelastic anisotropy. Use is made of evolution equations for a triad of microstructural vectors mathbf{m}i (hbox {i}=1,2,3) which model elastic deformations and directions of anisotropy. Specific constitutive equations are presented for a material with orthotropic elastic response. The rate of inelasticity depends on an orthotropic yield function that can be used to model weak fault planes with failure in shear and which exhibits a smooth transition to isotropic response at high compression. Moreover, a robust, strongly objective numerical algorithm is proposed for both rate-independent and rate-dependent response. The predictions of the continuum model are examined by comparison with exact steady-state solutions. Also, the constitutive equations are used to obtain a simplified continuum model of jointed rock which is compared with high fidelity numerical solutions that model a persistent system of joints explicitly in the rock medium.
Elastic Properties of the Solid Electrolyte Li7La3Zr2O12 (LLZO)
Yu, Seungho; Schmidt, Robert D.; Garcia-mendez, Regina; Herbert, Erik G.; Dudney, Nancy J.; Wolfenstine, Jeff; Sakamoto, Jeff; Seigel, Donald
2015-12-16
The oxide known as LLZO, with nominal composition Li7La3Zr2O12, is a promising solid electrolyte for Li-based batteries due to its high Li-ion conductivity and chemical stability with respect to lithium. Solid electrolytes may also enable the use of metallic Li anodes by serving as a physical barrier that suppresses dendrite initiation and propagation during cycling. Prior linear elasticity models of the Li electrode/solid electrolyte interface suggest that the stability of this interface is highly dependent on the elastic properties of the solid separator. For example, dendritic suppression is predicted to be enhanced as the electrolyte s shear modulus increases. Inmore » the present study a combination of first-principles calculations, acoustic impulse excitation measurements, and nanoindentation experiments are used to determine the elastic constants and moduli for highconductivity LLZO compositions based on Al and Ta doping. The calculated and measured isotropic shear moduli are in good agreement and fall within the range of 56-61 GPa. These values are an order of magnitude larger than that for Li metal and far exceed the minimum value ( 8.5 GPa) believed to be necessary to suppress dendrite initiation. These data suggest that LLZO exhibits sufficient stiffness to warrant additional development as a solid electrolyte for Li batteries.« less
NASA Astrophysics Data System (ADS)
Güler, M.; Güler, E.
2016-07-01
Although several theoretical works were performed to describe the high pressure behavior of typical cubic elastic constants of cubic diamond silicon (dc-Si), some of the obtained results of these studies still remain inadequate and disagree with the experimental findings. To get more satisfactory results, we have investigated the phase transition, elasticity and other relevant mechanical properties of dc-Si were under pressures up to 14 GPa by applying original form of modified embedded atom method type interatomic potential for the first time with geometry optimization calculations. Phase transition pressure from dc-Si to β-Sn phase was found to be as 13 GPa which agree well with experiments. As well, under pressure, typical cubic elastic constants mimic the increasing behavior of experimental data and removes the earlier theoretical conflicts, in particular for C 44. Further, bulk, Young and shear moduli, longitudinal and shear wave velocities, structural stability and brittle (ductile) character of dc-Si were also investigated under pressure. Obtained data of these surveyed quantities for the ground state of dc-Si well compare the previous experiments and other theoretical findings.
Elastic Properties of the Solid Electrolyte Li7La3Zr2O12 (LLZO)
Yu, Seungho; Schmidt, Robert D.; Garcia-mendez, Regina; Herbert, Erik G.; Dudney, Nancy J.; Wolfenstine, Jeff; Sakamoto, Jeff; Seigel, Donald
2015-12-16
The oxide known as LLZO, with nominal composition Li_{7}La_{3}Zr_{2}O_{12}, is a promising solid electrolyte for Li-based batteries due to its high Li-ion conductivity and chemical stability with respect to lithium. Solid electrolytes may also enable the use of metallic Li anodes by serving as a physical barrier that suppresses dendrite initiation and propagation during cycling. Prior linear elasticity models of the Li electrode/solid electrolyte interface suggest that the stability of this interface is highly dependent on the elastic properties of the solid separator. For example, dendritic suppression is predicted to be enhanced as the electrolyte s shear modulus increases. In the present study a combination of first-principles calculations, acoustic impulse excitation measurements, and nanoindentation experiments are used to determine the elastic constants and moduli for highconductivity LLZO compositions based on Al and Ta doping. The calculated and measured isotropic shear moduli are in good agreement and fall within the range of 56-61 GPa. These values are an order of magnitude larger than that for Li metal and far exceed the minimum value ( 8.5 GPa) believed to be necessary to suppress dendrite initiation. These data suggest that LLZO exhibits sufficient stiffness to warrant additional development as a solid electrolyte for Li batteries.
Determination of the elasticity of parachute materials under dynamic loading conditions
Behr, V.L.; Clements, P.J.; Silbert, M.N.
1996-12-31
In the design of parachute systems it is important to use material properties that have been acquired under representative strain rates expected in flight. Without such data the designer is potentially forced to incorporate unrealistic safety margins resulting in a heavier and costlier than required design. Laboratory test data has generally been limited to that which can be acquired at quasi-steady strain rates. This paper investigates a technique, which takes advantage of advances in solid state electronics in the past ten years, to achieve an economical means of acquiring material properties under dynamic strain conditions. Data obtained with this technique is compared to standard test data for representative parachute materials.
Breathing mode vibrations and elastic properties of single-crystal and penta-twinned gold nanorods.
Gan, Yong; Sun, Zheng; Chen, Zhen
2016-08-10
The acoustic vibrations of individual single-crystal and penta-twinned gold nanorods with widths from ∼7 to ∼26 nm are studied using atomic-level simulations and finite element calculations. It is demonstrated that the continuum model in the limit of an infinite rod length could be used to describe the breathing periods of nanorods with an aspect ratio as small as ∼2.5, in combination with bulk material elastic constants. The elastic moduli of gold nanorods are determined via their atomistically simulated extensional periods and the dispersion relation based on long-wavelength approximation. The twinned nanorods become stiffer as the width is reduced, which is in contrast to the size dependence of the modulus in single-crystal nanorods. Further finite element calculations for the breathing periods of nanorods are performed using isotropic elastic constants of bulk gold. We find that the breathing vibrations of the penta-twinned nanorods are more affected by the crystal structure effect than those of single-crystal nanorods, because a smaller range of crystal directions perpendicular to the long axis is involved in the breathing vibrations of twinned nanorods. PMID:27476532
Acoustical properties of double porosity granular materials.
Venegas, Rodolfo; Umnova, Olga
2011-11-01
Granular materials have been conventionally used for acoustic treatment due to their sound absorptive and sound insulating properties. An emerging field is the study of the acoustical properties of multiscale porous materials. An example of these is a granular material in which the particles are porous. In this paper, analytical and hybrid analytical-numerical models describing the acoustical properties of these materials are introduced. Image processing techniques have been employed to estimate characteristic dimensions of the materials. The model predictions are compared with measurements on expanded perlite and activated carbon showing satisfactory agreement. It is concluded that a double porosity granular material exhibits greater low-frequency sound absorption at reduced weight compared to a solid-grain granular material with similar mesoscopic characteristics. PMID:22087905
Elastic properties of poly(vinyldene fluoride) (PVDF) crystals: A density functional theory study
NASA Astrophysics Data System (ADS)
Pei, Yong; Zeng, Xiao Cheng
2011-05-01
We computed structural and elastic properties of totally nine phases of poly(vinyldene fluoride) (PVDF) crystals using the density-functional theory (DFT) method with and without inclusion of the dispersion corrections. In addition to the four known crystalline forms, mechanic properties of five theoretically predicted crystalline forms of PVDF are also investigated. The all-trans form Ip exhibits the largest cohesive energy, bulk, and Young's modulus among the nine crystalline forms. The DFT calculations suggest that the δ crystalline forms (IIIau, IIIpu, IIIpd, and IIIad) possess poor chain rigidity among the nine PVDF crystalline forms. In contrast, a change of relative orientation of PVDF chains does not lead to significant change in cohesive energy and mechanic properties. A comparison of the cohesive energies of nine crystalline forms of PVDF suggests that the theoretically proposed crystalline forms of PVDF are quite stable.
NASA Astrophysics Data System (ADS)
Ozyar, U. F.; Deligoz, E.; Colakoglu, K.
2015-02-01
The anisotropic elastic properties of XYSb (X = Ti, Zr, Hf; Y = Si, Ge) compounds have been investigated by using first-principles calculations based on density functional theory. The calculated lattice parameters are in excellent agreement with the available experimental data. The computed elastic constants indicate that all compounds are mechanically stable according to the elastic stability criteria under pressure. We have calculated the bulk modulus, shear modulus, Young's modulus, Poisson's ratio, Debye temperature, and anisotropy value from the obtained elastic constants according to the Voigt-Reuss-Hill approximation. Additionally, the ductility and brittleness are characterized with the estimation from Pugh's rule (B/G) and Poisson's ratio. Furthermore, the elastic anisotropy have been visualized in detail by plotting the directional dependence of compressibility, Young's and shear moduli.
Elastic, Electronic, Optical and Thermal Properties of Na2Po: An Ab Initio Study
NASA Astrophysics Data System (ADS)
Baki, N.; Eithiraj, R. D.; Khachai, H.; Khenata, R.; Murtaza, G.; Bouhemadou, A.; Seddik, T.; Bin-Omran, S.
2016-01-01
The structural, elastic, electronic, optical and thermodynamic properties of the sodium polonide Na2Po compound have been studied through the full potential linearized augmented plane wave plus local orbitals (FP-LAPW + lo) and tight-binding linear muffin-tin orbital (TB-LMTO) methods. The exchange-correlation potential was treated within the local density approximation for the TB-LMTO calculations and within the generalized gradient approximation for the FP-LAPW + lo calculations. In addition, Tran and Blaha-modified Becke-Johnson (TB-mBJ) potential and Engel-Vosko generalized gradient approximation were used for the electronic and optical properties. Ground state properties such as the equilibrium lattice constant, bulk modulus and its pressure derivative were calculated and compared with available data. The single-crystal and polycrystalline elastic constants of the considered compound were calculated via the total energy versus strain in the framework of the FP-LAPW + lo approach. The calculated electronic structure reveals that Na2Po is a direct band gap semiconductor. The frequency-dependent dielectric function, refractive index, extinction coefficient, reflectivity coefficient and electron energy loss function spectra are calculated for a wide energy range. The variations of the lattice constant, bulk modulus, heat capacity, volume expansion coefficient and Debye temperature with temperature and pressure were calculated successfully using the FP-LAPW + lo method in combination with the quasi-harmonic Debye model.
NASA Astrophysics Data System (ADS)
Alsteens, David; Dupres, Vincent; McEvoy, Kevin; Wildling, Linda; Gruber, Hermann J.; Dufrêne, Yves F.
2008-09-01
Although the chemical composition of yeast cell walls is known, the organization, assembly, and interactions of the various macromolecules remain poorly understood. Here, we used in situ atomic force microscopy (AFM) in three different modes to probe the ultrastructure, cell wall elasticity and polymer properties of two brewing yeast strains, i.e. Saccharomyces carlsbergensis and S. cerevisiae. Topographic images of the two strains revealed smooth and homogeneous cell surfaces, and the presence of circular bud scars on dividing cells. Nanomechanical measurements demonstrated that the cell wall elasticity of S. carlsbergensis is homogeneous. By contrast, the bud scar of S. cerevisiae was found to be stiffer than the cell wall, presumably due to the accumulation of chitin. Notably, single molecule force spectroscopy with lectin-modified tips revealed major differences in polysaccharide properties of the two strains. Polysaccharides were clearly more extended on S. cerevisiae, suggesting that not only oligosaccharides, but also polypeptide chains of the mannoproteins were stretched. Consistent with earlier cell surface analyses, these findings may explain the very different aggregation properties of the two organisms. This study demonstrates the power of using multiple complementary AFM modalities for probing the organization and interactions of the various macromolecules of microbial cell walls.
Investigation of the elastic properties of a lipid bilayer by fluorescence interferometry
NASA Astrophysics Data System (ADS)
Gui, Dong; Lin, Hsiang-Ku; Noruzifar, Ehsan; Pryadko, Leonid; Zandi, Roya; Mohideen, Umar
2012-02-01
Freestanding curved lipid bilayers were formed on micron diameter wells fabricated on a silicon chip. The height profile of the lipid bilayers was measured using fluorescence interference contrast microscopy. Dark and bright rings resulted from the interference of emission from the fluorophores in the lipid bilayers with the same light reflected from the bottom surface of the well. By changing the osmotic pressure difference across the bilayers, the relationship between the pressure and the membrane curvature was studied. By using Helfrich theory, the surface tension of the bilayer was extracted. The influence of detergents and antibiotics on the elastic property of lipid bilayers was also investigated.
Measuring the elastic properties of living cells with atomic force microscopy indentation.
Mackay, Joanna L; Kumar, Sanjay
2013-01-01
Atomic force microscopy (AFM) is a powerful and versatile tool for probing the mechanical properties of biological samples. This chapter describes the procedures for using AFM indentation to measure the elastic moduli of living cells. We include step-by-step instructions for cantilever calibration and data acquisition using a combined AFM/optical microscope system, as well as a detailed protocol for data analysis. Our protocol is written specifically for the BioScope™ Catalyst™ AFM system (Bruker AXS Inc.); however, most of the general concepts can be readily translated to other commercial systems. PMID:23027009
Characterization of elastic-plastic properties of AS4/APC-2 thermoplastic composite
NASA Technical Reports Server (NTRS)
Sun, C. T.; Yoon, K. J.
1988-01-01
Elastic and inelastic properties of AS4/APC-2 composites were characterized with respect to temperature variation by using a one-parameter orthotropic plasticity model and a one parameter failure criterion. Simple uniaxial off-axis tension tests were performed on coupon specimens of unidirectional AS4/APC-2 thermoplastic composite at various temperatures. To avoid the complication caused by the extension-shear coupling effect in off-axis testing, new tabs were designed and used on the test specimens. The experimental results showed that the nonlinear behavior of constitutive relations and the failure strengths can be characterized quite well using the one parameter plasticity model and the failure criterion, respectively.
Mobility of vacancies under deformation and their effect on the elastic properties of graphene
Fedorov, A. S.; Fedorov, D. A.; Popov, Z. I.; Anan'eva, Yu. E.; Eliseeva, N. S.; Kuzubov, A. A.
2011-05-15
The effect of isolated vacancies on the elastic properties of a graphene sheet has been investigated by the ab initio density functional method. An almost inverse linear dependence of the Young's modulus on the concentration of vacancies has been revealed. The height of potential barriers for the motion of vacancies in various directions has been calculated as a function of various independent applied strains. The velocity of vacancies at various temperatures has been calculated as a function of applied strains using the transition state theory.
MACKEY TC; ABATT FG; JOHNSON KI
2009-01-16
The purpose of this study was to determine the sensitivity of the dynamic response of the Hanford double-shell tanks (DSTs) to the assumptions regarding the constitutive properties of the contained waste. In all cases, the waste was modeled as a uniform linearly elastic material. The focus of the study was on the changes in the modal response of the tank and waste system as the extensional modulus (elastic modulus in tension and compression) and shear modulus of the waste were varied through six orders of magnitude. Time-history analyses were also performed for selected cases and peak horizontal reaction forces and axial stresses at the bottom of the primary tank were evaluated. Because the analysis focused on the differences in the responses between solid-filled and liquid-filled tanks, it is a comparative analysis rather than an analysis of record for a specific tank or set of tanks. The shear modulus was varied between 4 x 10{sup 3} Pa and 4.135 x 10{sup 9} Pa. The lowest value of shear modulus was sufficient to simulate the modal response of a liquid-containing tank, while the higher values are several orders of magnitude greater than the upper limit of expected properties for tank contents. The range of elastic properties used was sufficient to show liquid-like response at the lower values, followed by a transition range of semi-solid-like response to a clearly identifiable solid-like response. It was assumed that the mechanical properties of the tank contents were spatially uniform. Because sludge-like materials are expected only to exist in the lower part of the tanks, this assumption leads to an exaggeration of the effects of sludge-like materials in the tanks. The results of the study show that up to a waste shear modulus of at least 40,000 Pa, the modal properties of the tank and waste system are very nearly the same as for the equivalent liquid-containing tank. This suggests that the differences in critical tank responses between liquid-containing tanks
Elastic airtight container for the compaction of air-sensitive materials.
Shoulders, W Taylor; Locke, Richard; Gaume, Romain M
2016-06-01
We report on the design and fabrication of a simple and versatile elastic canister for the compaction and hot-pressing of air-sensitive materials. This device consists of a heated double-ended floating die assembly, enclosed in a compressible stainless steel bellows that allows the action of an external hydraulic press in a uniaxial motion. The enclosure is fitted with vacuum, gas, and electrical feedthroughs to allow for atmosphere control, heating, and in situ process monitoring. The overall chamber is compact enough to be portable and transferrable into and out of a standard laboratory glovebox, thus eliminating the problem of exposing samples to ambient atmosphere during loading and unloading. Our design has been tested up to 600 °C and 7500 kg-force applied load, conditions within which transparent ceramics of anhydrous halides can be produced. PMID:27370471
Sound transmission through double panel constructions lined with elastic porous materials
NASA Astrophysics Data System (ADS)
Bolton, J. S.; Green, E. R.
1986-07-01
Attention is given to a theory governing one-dimensional wave motion in elastic porous materials which is capable of reproducing experimental transmission measurements for unfaced polyurethane foam layers. Calculations of the transmission loss of fuselage-like foam-lined double panels are presented and it is shown that the foam/panel boundary conditions have a large effect on the panel performance; a hybrid arrangement whereby the foam is bonded directly to one panel and separated from the other by a thin air gap appears to be the most advantageous under practical circumstances. With this configuratiom, the mass-air-mass resonance is minimized and increased low-frequency performance is offered.
Elastic airtight container for the compaction of air-sensitive materials
NASA Astrophysics Data System (ADS)
Shoulders, W. Taylor; Locke, Richard; Gaume, Romain M.
2016-06-01
We report on the design and fabrication of a simple and versatile elastic canister for the compaction and hot-pressing of air-sensitive materials. This device consists of a heated double-ended floating die assembly, enclosed in a compressible stainless steel bellows that allows the action of an external hydraulic press in a uniaxial motion. The enclosure is fitted with vacuum, gas, and electrical feedthroughs to allow for atmosphere control, heating, and in situ process monitoring. The overall chamber is compact enough to be portable and transferrable into and out of a standard laboratory glovebox, thus eliminating the problem of exposing samples to ambient atmosphere during loading and unloading. Our design has been tested up to 600 °C and 7500 kg-force applied load, conditions within which transparent ceramics of anhydrous halides can be produced.
Yano, Shinya; Mori, Megumi; Teramoto, Naozumi; Iisaka, Makoto; Suzuki, Natsumi; Noto, Masanari; Kaimoto, Yasuko; Kakimoto, Masashi; Yamada, Michio; Shiratsuchi, Eri; Shimasaki, Toshiaki; Shibata, Mitsuhiro
2015-01-01
Photocrosslinked hydrogels reinforced by microfibrillated cellulose (MFC) were prepared from a methacrylate-functionalized fish elastin polypeptide and MFC dispersed in dimethylsulfoxide (DMSO). First, a water-soluble elastin peptide with a molecular weight of ca. 500 g/mol from the fish bulbus arteriosus was polymerized by N,N′-dicyclohexylcarbodiimide (DCC), a condensation reagent, and then modified with 2-isocyanatoethyl methacrylate (MOI) to yield a photocrosslinkable fish elastin polypeptide. The product was dissolved in DMSO and irradiated with UV light in the presence of a radical photoinitiator. We obtained hydrogels successfully by substitution of DMSO with water. The composite gel with MFC was prepared by UV irradiation of the photocrosslinkable elastin polypeptide mixed with dispersed MFC in DMSO, followed by substitution of DMSO with water. The tensile test of the composite gels revealed that the addition of MFC improved the tensile properties, and the shape of the stress–strain curve of the composite gel became more similar to the typical shape of an elastic material with an increase of MFC content. The rheology measurement showed that the elastic modulus of the composite gel increased with an increase of MFC content. The cell proliferation test on the composite gel showed no toxicity. PMID:25584682
NASA Astrophysics Data System (ADS)
Blake, O. O.; Faulkner, D. R.; Tatham, D.
2013-12-01
Fracture in rock is a major factor that affects the rock's elastic properties. Elastic properties can be measured statically where stress and strain data are recorded during slow loading of a specimen, or dynamically, where the elasticity can be calculated from P- and S- wave velocity. During crustal deformation, rocks deform nearly statically, hence the relationship between the static and dynamic elastic properties must be known so that the dynamic elastic properties can be converted to static elastic properties to allow geomechanical and geodynamic modelling. In this study, the dynamic and static elastic properties were measured for dry crystalline rocks (Westerly granite) that were thermally treated to 250, 450, 650 and 850°C. Increasing the temperature produces an increased fracture density that is isotropically distributed. Experiments were carried out under confining pressure up to crack-closure pressure, 130MPa (~8km burial depth under hydrostatic pore pressure conditions). Increased fracture density within the rock results in a reduction in Young modulus and an increase in the Poisson's ratio, in both the static and dynamic case which is very significant above 573°C. The reduction and increase are retarded with increasing confining pressure. At crack-closure pressure the fracture density, in terms of effective medium models, is zero even though the rock still contains cracks. The crack-closure pressure is independent of fracture damage incurred in the rock. We compared the static and dynamic measurements and found a linear relationship between the static and dynamic Young's modulus with very high correlation and a gradient of one which is independent of confining pressure and the amount of fracturing incurred in the samples from thermal treatment. We also found that the static and dynamic Poisson's ratio are in agreement for values less than 0.34. Above this value, the static Poisson's ratio is much higher than the dynamic Poisson's ratio. Voigt
Mechanical properties of materials with nanometer scale microstructures
Nix, W.D.
1991-07-01
For the past two years we have been engaged in a program of research on the mechanical properties of a variety of new materials with nanometer scale microstructures. These materials have been developed recently using vapor phase synthesis techniques and are available in the form of compositionally-modulated (multilayered) thin film materials and ultrafine-grained (nanocrystalline) solids. They have interesting microstructures and mechanical properties that may lead to new applications for these materials. In this report we give a brief summary of some of the results we have obtained to date in the course of this research. Other, more detailed, descriptions of some of this work can be found in the papers that we have published. These are listed at the end of this report along with a listing of the oral presentations we have given. We report briefly on our studies of the elastic properties of metallic multilayered thin films. Using indentation and microbeam deflection techniques, we have found that Au/Ni multilayers do not show supermodulus effects, contrary to some previous reports based on bulge test results. However, we have discovered large and significant substrate interaction stresses in these films which depend systematically on the composition modulation wavelength. We believe that these residual stresses may have led to bulge testing errors which in turn led to erroneous reports of supermodulus effects.
Synthesis and properties of nanophase materials
Siegel, R.W.
1993-03-01
Nanophase materials, with their grain sizes or phase dimensions in the nanometer size regime, are now being produced by a wide variety of synthesis and processing methods. The interest in these new ultrafine-grained materials results primarily from the special nature of their various physical, chemical, and mechanical properties and the possibilities to control these properties during the synthesis and subsequent processing procedures. Since it is now becoming increasingly apparent that their properties can be engineered effectively during synthesis and processing, and that they can also be produced in quantity, nanophase materials should have considerable potential for technological development in a variety of applications. Some of the recent research on nanophase materials related to their synthesis and properties is briefly reviewed and the future potential of these new materials is considered.
Mechanical Properties and Simulated Wear of Provisional Resin Materials.
Takamizawa, T; Barkmeier, W W; Tsujimoto, A; Scheidel, D; Erickson, R L; Latta, M A; Miyazaki, M
2015-01-01
The purpose of this study was to determine flexural properties and erosive wear behavior of provisional resin materials. Three bis-acryl base provisional resins-1) Protemp Plus (PP), 2) Integrity (IG), 3) Luxatemp Automix Plus (LX)-and a conventional poly(methylmethacrylate) (PMMA) resin, UniFast III (UF), were evaluated. A resin composite, Z100 Restorative (Z1), was included as a benchmark material. Six specimens for each of the four materials were used to determine flexural strength and elastic modulus according to ISO Standard 4049. Twelve specimens for each material were used to examine wear using a generalized wear simulation model. The test materials were each subjected to wear challenges of 25,000, 50,000, 100,000, and 200,000 cycles in a Leinfelder-Suzuki (Alabama) wear simulator. The materials were placed in custom cylinder-shaped stainless-steel fixtures, and wear was generated using a cylindrical-shaped flat-ended stainless-steel antagonist in a slurry of nonplasticized PMMA beads. Wear (mean facet depth [μm] and volume loss [mm(3)]) was determined using a noncontact profilometer (Proscan 2100) with Proscan and AnSur 3D software. The laboratory data were evaluated using two-way analysis of variance (ANOVA; factors: 1) material and 2) cycles) followed by Tukey HSD post hoc test (α=0.05). The flexural strength ranged from 68.2 to 150.6 MPa, and the elastic modulus ranged from 2.0 to 15.9 GPa. All of the bis-acryl provisional resins (PP, IG, and LX) demonstrated significantly higher values than the PMMA resin (UF) in flexural strength and elastic modulus (p<0.05). However, there was no significant difference (p>0.05) in flexural properties among three bis-acryl base provisional resins (PP, IG, and LX). Z1 demonstrated significantly (p<0.05) higher flexural strength and elastic modulus than the other materials tested. The results for mean facet wear depth (μm) and standard deviations (SD) for 200,000 cycles were as follows: PP, 22.4 (5.0); IG, 51.0 (6
Design of meta-materials with novel thermoelastic properties
NASA Astrophysics Data System (ADS)
Watts, Seth
The development of new techniques in micro-manufacturing in recent years has enabled the fabrication of material microstructures with essentially arbitrary designs, including those with multiple constituent materials and void space in nearly any geometry. With an essentially open design space, the onus is now on the engineer to design composite materials which are optimal for their purpose. These new materials, called meta-materials or materials with architected microstructures, offer the potential to mix and match properties in a way that exceeds that of traditional composites. We concentrate on the thermal and elastic properties of isotropic meta-materials, and design microstructures with combinations of Young's modulus, Poisson's ratio, thermal conductivity, thermal expansion, and mass density which are not found among naturally-occurring or traditional composite materials. We also produce designs with thermal expansion far below other materials. We use homogenization theory to predict the material properties of a bulk meta-material comprised of a periodic lattice of unit cells, then use topology optimization to rearrange two constituent materials and void space within the unit cell in order to extremize an objective function which yields the combinations of properties we seek. This method is quite general and can be extended to consider additional properties of interest. We constrain the design space to satisfy material isotropy directly (2D), or to satisfy cubic symmetry (3D), from which point an isotropy constraint function is easily applied. We develop and use filtering, nonlinear interpolation, and thresholding methods to render the design problem well-posed, and as a result ensure our designs are manufacturable. We have written two computer implementations of this design methodology. The first is for creating two-dimensional designs, which can run on a serial computer in approximately half an hour. The second is a parallel implementation to allow
A first-principles study of elastic and diffusion properties of magnesium based alloys
NASA Astrophysics Data System (ADS)
Ganeshan, Swetha
2011-12-01
In this thesis, the influence of alloying elements on the elastic and diffusion properties of Magnesium (Mg) has been studied based on first-principles density functional theory. The stress-strain method has been used to predict the elastic constants of the Mg based alloys studied herein. This method involves calculating the resultant change in stress due to application of strain. The validity of this method has been successfully tested for both 0K as well as at finite temperatures. The elastic constants predicted in this work have been correlated to ductility, fracture toughness, stiffness, elastic anisotropy and bond directionality, thus providing a better understanding of the influence of alloying elements on the mechanical and physical properties of Mg. Elastic constants, as a function of temperature have been predicted using first-principles quasi-static approximation. In this approach elastic stiffness coefficients calculated with respect to volume (cij( V)) have been correlated to the equilibrium volume as a function of temperature V(T) from phonon calculations to obtain temperature dependence of elastic stiffness coefficients cij(T). To compare our calculated temperature dependent elastic constants with that of experiments an isentropic correction term has been introduced. It is seen that the influence of this isentropic correction term on the elastic constants becomes significant at high temperatures. The quasi-static approximation has been primarily applied to calculate temperature dependent elastic constants of Mg2Ge, Mg2Si, Mg 2Sn and Mg2Pb. In the case of dilute Mg alloys, a 36 atom supercell with 35 atoms of Mg and one atom of the alloying impurity has been used for calculating the corresponding elastic constants. It is seen that there is a direct correspondence between the trends in the elastic constants and the lattice parameters of all the Mg based alloys studied herein. Elements that cause a decrease (increase) in the lattice constants result in