Temperature Dependence Of Elasticity Research Articles

Mechanical stability parameters of chalcogenides and pnictides based optoelectronic materials

A study of experimental data reveals that the bulk modulus of chalcogenides and pnictides based chalcopyrites (AIIBIVC2 V and AI BIIIC2 VI) can be explained by a simple scaling rule that rely only on the crystal ionicity, ionic charge product, and the melting temperature. PVV theory of crystal ionicity, temperature dependence of elasticity and product of ionic charge theory are taken into account for the study. Based on this result, a simple microhardnessbulk modulus relation is applied to evaluate the microhardness of the complex compounds; which correspond well with the experimental data and other published results. The proposed findings support in the modeling of emerging semiconductor materials and even understanding of their mechanical properties for optoelectronics, photovoltaic, electromagnetic (EM) screening, and spintronic applications. PACS: 62.20.-x; 62.20.Qp

Empirical predictions for bulk and shear moduli of zinc-blende structured binary solids

An empirical relationship has been found to evaluate the bulk modulus (B) and shear modulus (G) with the help of two experimental physical quantities (the melting temperature and the crystal ionicity), which are drawn from various pieces of literature. The PVV theory of crystal ionicity and temperature dependence of elasticity are taken into account for the study. The evaluated bulk modulus and shear modulus values are found to be in excellent conformity with experimental and reported values of other researchers. The current research supports the modelling of emerging semiconductor materials and even understanding of their mechanical properties for photovoltaic, spintronics, LiB systems, FLB phenomenon, and superhard material applications.

Correlation between Uniaxial Negative Thermal Expansion and Negative Linear Compressibility in Ag3[Co(CN)6

Density functional theory (DFT) calculations are used to investigate the correlation between the uniaxial negative thermal expansion (NTE) and negative linear compressibility (NLC) behaviors in Ag3[Co(CN)6]. First, we reproduce the uniaxial-NTE and NLC behaviors under temperature- and pressure-field. And then the temperature dependence of elasticity is studied. The abnormal nature of elastic constants C33 and C11+C12 as the function of temperature is predicted. The hardening of phonon modes (below 568.7 cm–1) with increasing temperature can be as an indicative for abnormal physical properties of Ag3[Co(CN)6]. Through analyzing the vibration mode with the strongest phonon hardening, the deformation of wine-rack motif in anisotropic framework can be identified as the mechanism that leads to the coexistence of uniaxial-NTE and NLC in Ag3[Co(CN)6]. The response of phonon group velocity along c-axis is intense and quicker than that of a-axis on heating and on compression, facilitating c-axis itself to be the c...

High-temperature elastic anisotropy of B2-type FeAl

The electromagnetic acoustic resonance method was applied to measure the elastic constants ( c 11 , c 12 , and c 44 ) of Fe–40, –43 and –46Al (at.%) single crystals from room temperature to 1173 K. The temperature dependence of the energy factor, K , and the elastic anisotropy factor, A , was obtained. A increased monotonously with increasing temperature and reached ∼7 at ∼1200 K. Therefore, it was confirmed that B2-type FeAl shows an anomalous temperature dependence of elasticity.

Frequency Stability of a Closed-Loop Oscillator Using Micro-Electro-Mechanical Cantilever Resonator Against Temperature Fluctuation

The frequency stability of a silicon cantilever resonator against temperature was investigated under open-loop and closed-loop conditions. The authors found that the adjustment of the circuit phase in the closed-loop condition induced a significant change in temperature coefficient. The observed temperature coefficient dependence on the circuit phase was analyzed with the temperature dependence of elasticity in silicon and the phase shift originated from the oscillation circuit. The existence of a phase shift of 1.37°/°C was evaluated from the measured results. The phase effect was comparable to the elasticity effect on the temperature coefficient.

Thermal, Mechanical, and Dielectric Properties of a Dielectric Elastomer for Actuator Applications

Dielectric elastomers (DE) are a new type of electro-active material, which is able to produce a large degree of deformation under electrical stimulation. The thermal, mechanical, and dielectric properties of the most widely used dielectric acrylic elastomer (VHB 4910), commercially available from the company 3M, were studied by differential scanning calorimetry (DSC), thermal gravimetric analysis (TGA), dynamic mechanical analysis (DMA), and broadband dielectric spectroscopy (BDS) analyzer, respectively. DSC experiments on the VHB 4910 showed a glass transition at about −40°C. VHB 4910 started to lose weight at about 250°C from the TGA study. The results of DMA indicated the storage modulus of VHB 4910 increased with frequency and had a strong temperature dependence of elasticity. The dielectric constant of VHB 4910 increased as a function of temperature up to 0°C, followed by a drop till 100°C. The mechanical and electrical efficiency of dielectric elastomer actuators (DEA) of VHB 4910 were analyzed. It was demonstrated that the actuation performance is dominated by the mechanical properties of the elastomer and is less influenced by the frequency and the temperature dependence of the dielectric properties; this may be used to guide the design of actuator configurations, as well as the choice of actuator materials.

Stress and temperature in the bending lithosphere as constrained by experimental rock mechanics

Summary. Previous attempts to deduce the stress distribution in the bending lithosphere near a consuming plate margin have relied on the observed bathymetry and an assumed constitutive relation for lithospheric behaviour, eg. perfectly elastic, viscous/perfectly plastic, or elastic perfectly plastic. From the point of view of rock mechanics, each of these approximations fails to describe one or more of several basic phenomena, including brittle failure of rock, temperature dependence of elasticity, and temperature and/or strain rate dependence of ductile behaviour. In order to formulate a more realistic constitutive relation, a limiting yield strength curve, which is primarily a function of temperature, is constructed from data from brittle failure and ductile flow experiments. The moments which can be supported by plates with this constitutive behaviour are compared to the moments calculated from bathymetric profiles. The comparison indicates that moments required by the bathymetric data are consistent with moments supported by plates with experimentally determined constitutive laws as extrapolated to geo- logically reasonable temperatures and strain rates. The stresses developed in such models are required to reach values greater than 100 MPat in the depth range 25-45 km. Geotherms necessary for strength curves consistent with moments calculated from the bathymetric data match those derived from heat flow data for the Aleutian, Bonin, Mariana and Tonga trenches. Of the trenches studied, only the geotherm inferred from the Kuril trench data is significantly different, perhaps implying that the Kuril plate is weaker than the others. The strength curves show that as a first approximation it is better to assume that bending moment is independent of curvature of the plate than to assume that bending moment and curvature are linearly related.

Dynamic rheological properties of polyisobutylene

AbstractThe viscoelastic properties of polyisobutylene melts were investigated as functions of temperature, molecular weight, and molecular weight distribution. The effect of molecular weight distribution was studied through the use of blends of narrow distribution polymers. The Ninomiya and Ferry theory was used successfully to predict the viscosity of the blends. It was observed that the temperature coefficient for flow was independent of molecular weight distribution and of molecular weight. It was shown, at least in the case of polyisobutylene melts, that the temperature dependence of elasticity is less for polymers with greater polydispersity.