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The Leeb hardness test is a non-destructive and portable technique that can be used both in the laboratory and in-field applications. The main purpose of this study is to predict the dynamic elastic constants of the igneous and sedimentary rocks using Leeb dynamic hardness testing. For this purpose, three vital topics have been investigated and analyzed. First, the relationships between ultrasonic wave velocities and dynamic elastic constants with the Leeb hardness were investigated. Thereafter, by determining the rock quality index (IQ) using microscopic studies and by analyzing the quality index-porosity plot, the variation of the Leeb hardness values was studied. Eventually, the longitudinal waveform in rock samples with different quality indexes and Leeb hardness were analyzed. To achieve these outputs, 33 samples of igneous and sedimentary rocks with a wide range of physical, mechanical, and textural features were collected and tested. The results of the analyses show that in both igneous and sedimentary rocks, the dynamic modulus of elasticity (E d ) has a significant correlation with the Leeb hardness. Generally, based on the microscopic studies, it was observed that the existence of the porosity in sedimentary rocks and intercrystalline and intracrystalline fissures in igneous rocks sharply reduce the Leeb hardness and thus lead to changes in the form of the longitudinal waves.

The experimental work described in this paper was carried out in order to discover about the effects of petrographic characteristics on the ultrasonic pulse velocity and dynamic elastic constants of granitic rocks. For this, petrographic characteristics include the mean mineral grain size (MGS) and ratio of Quartz to Feldspar (Qz/Fl), ultrasonic pulse velocity include the P-wave (Vp) and S-wave velocity (Vs), and dynamic elastic constants include the elastic modulus (E) and Poisson’s ratio (ν) of ten different granitic rock were determined. By data analysis, correlations between Vp, Vs, E and ν with MGS and Qz/Fl were developed. It is concluded that the MGS and Qz/Fl have significant effects on the Vp, Vs, E and ν. Moreover, the results showed that MGS and Qz/Fl are in good accuracy for estimating the Vp, Vs and E, while there are no meaningful correlations between ν with MGS and Qz/Fl.

In this study, the mechano-chemical properties of aromatic polymer polyetheretherketone (PEEK) samples, irradiated by high energy electrons at 200 and 400 kGy doses, were investigated by Nanoindentation, Brillouin light scattering spectroscopy and Fourier-transform infrared spectroscopy (FTIR). Irradiating electrons penetrated down to a 5 mm depth inside the polymer, as shown numerically by the monte CArlo SImulation of electroN trajectory in sOlids (CASINO) method. The irradiation of PEEK samples at 200 kGy caused the enhancement of surface roughness by almost threefold. However, an increase in the irradiation dose to 400 kGy led to a decrease in the surface roughness of the sample. Most likely, this was due to the processes of erosion and melting of the sample surface induced by high dosage irradiation. It was found that electron irradiation led to a decrease of the elastic constant C11, as well as a slight decrease in the sample’s hardness, while the Young’s elastic modulus decrease was more noticeable. An intrinsic bulk property of PEEK is less radiation resistance than at its surface. The proportionality constant of Young’s modulus to indentation hardness for the pristine and irradiated samples were 0.039 and 0.038, respectively. In addition, a quasi-linear relationship between hardness and Young’s modulus was observed. The degradation of the polymer’s mechanical properties was attributed to electron irradiation-induced processes involving scission of macromolecular chains.

First-principles calculations on a huge configuration space of four different binary alloy systems reveal that stiffness and heat of formation are negatively and linearly correlated. A stiff test for stability This study asks a fundamental question: is the most thermodynamically stable atomic configuration of a material the hardest, stiffest or strongest form of that material? Or could some metastable configurations improve on that performance? Focusing on stiffness, the authors perform first-principles calculations on a huge configuration space of four different binary-alloy systems. They find that, at least in the systems they research, stiffness and heat of formation are negatively and linearly correlated. That is, the more stable a system is, the harder the material will be. The methods used here should, in principle, be applicable to the investigation of other relationships between stability and mechanical properties. Any thermodynamically stable or metastable phase corresponds to a local minimum of a potentially very complicated energy landscape. But however complex the crystal might be, this energy landscape is of parabolic shape near its minima. Roughly speaking, the depth of this energy well with respect to some reference level determines the thermodynamic stability of the system, and the steepness of the parabola near its minimum determines the system’s elastic properties. Although changing alloying elements and their concentrations in a given material to enhance certain properties dates back to the Bronze Age 1 , 2 , the systematic search for desirable properties in metastable atomic configurations at a fixed stoichiometry is a very recent tool in materials design 3 . Here we demonstrate, using first-principles studies of four binary alloy systems, that the elastic properties of face-centred-cubic intermetallic compounds obey certain rules. We reach two conclusions based on calculations on a huge subset of the face-centred-cubic configuration space. First, the stiffness and the heat of formation are negatively correlated with a nearly constant Spearman correlation 4 for all concentrations. Second, the averaged stiffness of metastable configurations at a fixed concentration decays linearly with their distance to the ground-state line (the phase diagram of an alloy at zero Kelvin). We hope that our methods will help to simplify the quest for new materials with optimal properties from the vast configuration space available.

In the present paper, we have investigated the phase transition and elastic properties of BeO at high pressure using three-body potential model (TBPM). The present interaction potential consists of long-range coulomb and three-body interactions and short-range overlap repulsion effective up to second neighbour ions. We have studied the phase transition from wurtzite ( B 4 ) to rock salt ( B 1 ) for BeO. The phase transition pressure ( P t ) obtained from this approach shows a respectably good agreement with experimental and other theoretical data. We have also computed the collapse of relative volume changes (Δ V ( P t )/ V (0)). Three-body potential model has also been used to derive the correct expressions for third-order elastic constants and pressure derivatives of second-order elastic constants for BeO.

The elastic properties of CdxNi1−xFe2O4 (x = 0.2, 0.4, 0.6 and 0.8) spinel ferrite system synthesized by wet-chemical technique, have been studied by infra-red spectroscopy and X-ray diffraction pattern analysis before (W) and after high temperature annealing (AW). The average particle size for wet-samples was within the range 4–5 nm, which is much lower than the average particle size found for AW samples (≈85 nm). The force constants for tetrahedral and octahedral sites determined by infrared spectral analysis, lattice constant and X-ray density values by X-ray diffraction pattern analysis; have been used to calculate elastic constants. The elastic moduli for W-samples are found to be larger as compared to AW samples, which are explained on the basis of grain size reduction effect. The average crystallite size calculated from elastic data is in agreement to that determined from X-ray diffraction data analysis.

In this article, expressions are derived for the Voigt, Reuss, and Hill estimates of the third-order elastic constants for polycrystals with either cubic or hexagonal crystal symmetry and orthorhombic physical symmetry. General forms of the fourth- and sixth-rank elastic stiffness and compliance tensors for crystal and physical symmetries are given. Explicit expressions are reduced from these tensors for the case of polycrystals exhibiting orthorhombic sample symmetry with either cubic or hexagonal crystallites. The estimated third-order elastic constants of the textured polycrystal are obtained in terms of second- and third-order single-crystal elastic constants and orientation distribution coefficients (ODCs), which are used to account for anisotropic physical symmetry. The acoustic nonlinearity parameter, β ¯ , is defined through combinations of the second- and third-order Voigt, Reuss, and Hill estimates of the elastic constants for a textured polycrystal. The model predicts that β ¯ is dependent on the type of averaging scheme used and the texture-defining ODCs. The model is quantitatively evaluated for polycrystalline iron, aluminum, and titanium using second- and third-order single-crystal elastic constants and experimentally measured ODCs. The interrelation between β ¯ and polycrystalline anisotropy offers potential for techniques associated with quantitative texture analysis.

We have investigated the relation between the softening of elastic constants and martensitic transformation in Fe3Pt, which exhibits various kinds of martensitic transformation depending on its long-range order parameter S. The martensite phases of the examined alloys are BCT (S = 0.57), FCT1 (S = 0.75, c/a < 1) and FCT2 (S = 0.88, c/a > 1). The elastic constants C′ and C44 of these alloys decrease almost linearly with decreasing temperature. Although the temperature coefficient of C′ decreases as S increases, C′ at the transformation temperature is the smallest in the alloy with S = 0.75, which transforms to FCT1. This result implies that softening is most strongly related to the formation of the FCT1 martensite with tetragonality c/a < 1 among the three martensites.

The aim of this study was to provide a practical approach towards discovering the anisotropic behaviors of polyvinyl chloride (PVC)-coated fabrics under low tensile stresses, as well as those at the tensile failure stage. Test specimens were PVC-coated polyester woven fabrics. One group of bias tensile experiments, with off-axial angles of 0°, 15°, 30°, 45°, 60°, 75° and 90°, was conducted under low tensile stresses. The anisotropic behaviors on elastic constants of coated fabrics were analyzed with the application of off-axial constitutive response of orthotropic and elastic materials. The experiment data agreed well with the prediction of the off-axial constitutive response. It was proved that coated fabrics can be regarded as orthotropic and elastic materials within 20 % of the ultimate tensile stress. To analyze the anisotropic behaviors at the tensile failure stage, another group of bias tensile experiments with the same off-axial angles was carried out. Three types of failure mechanisms, pure tensile failure, pure shear failure and a mixed failure of tensile and shear, were observed by analyzing the fracture configuration of the specimens under each bias tensile loading. For the prediction of the anisotropic failure strength of coated fabrics, Tsai-Hill strength criterion was used and the results analyzed.

Using epitaxy and the misfit strain imposed by an underlying substrate, it is possible to elastically strain oxide thin films to percent levels—far beyond where they would crack in bulk. Under such strains, the properties of oxides can be dramatically altered. In this article, we review the use of elastic strain to enhance ferroics, materials containing domains that can be moved through the application of an electric field (ferroelectric), a magnetic field (ferromagnetic), or stress (ferroelastic). We describe examples of transmuting oxides that are neither ferroelectric nor ferromagnetic in their unstrained state into ferroelectrics, ferromagnets, or materials that are both at the same time (multiferroics). Elastic strain can also be used to enhance the properties of known ferroic oxides or to create new tunable microwave dielectrics with performance that rivals that of existing materials. Results show that for thin films of ferroic oxides, elastic strain is a viable alternative to the traditional method of chemical substitution to lower the energy of a desired ground state relative to that of competing ground states to create materials with superior properties.