Hydrostatic stress

About: Hydrostatic stress is a research topic. Over the lifetime, 1568 publications have been published within this topic receiving 37773 citations.

Effect of hydrostatic initial stress and rotation in green-naghdi (type iii) thermoelastic half-space with two temperature

Abstract: Green and Naghdi theory of thermoelasticity is employed to study the deformation of thermoelastic solid half-space under hydrostatic initial stress and rotation with two temperature. The normal mode analysis is used to obtain the analytical expressions of the displacement components, force stress, temperature distribution and conductive temperature. The numerical results are given and presented graphically when mechanical force is applied. Some particular cases are also discussed in context of the problem. Comparisons are made in the presence and absence of hydrostatic initial stress and rotation.

Incorporating tissue anisotropy and heterogeneity in finite element models of trabecular bone altered predicted local stress distributions

Abstract: Trabecular bone is composed of organized mineralized collagen fibrils, which results in heterogeneous and anisotropic mechanical properties at the tissue level. Recently, biomechanical models computing stresses and strains in trabecular bone have indicated a significant effect of tissue heterogeneity on predicted stresses and strains. However, the effect of the tissue-level mechanical anisotropy on the trabecular bone biomechanical response is unknown. Here, a computational method was established to automatically impose physiologically relevant orientation inherent in trabecular bone tissue on a trabecular bone microscale finite element model. Spatially varying tissue-level anisotropic elastic properties were then applied according to the bone mineral density and the local tissue orientation. The model was used to test the hypothesis that anisotropy in both homogeneous and heterogeneous models alters the predicted distribution of stress invariants. Linear elastic finite element computations were performed on a 3 mm cube model isolated from a microcomputed tomography scan of human trabecular bone from the distal femur. Hydrostatic stress and von Mises equivalent stress were recorded at every element, and the distributions of these values were analyzed. Anisotropy reduced the range of hydrostatic stress in both tension and compression more strongly than the associated increase in von Mises equivalent stress. The effect of anisotropy was independent of the spatial redistribution high compressive stresses due to tissue elastic heterogeneity. Tissue anisotropy and heterogeneity are likely important mechanisms to protect bone from failure and should be included for stress analyses in trabecular bone.

Crystal structure of CaSiO3 perovskite at 28–62 GPa and 300 K under quasi-hydrostatic stress conditions

Abstract: Abstract To find the thermodynamically stable crystal structure of CaSiO3 perovskite (CaPv) at high pressure and 300 K, we have conducted synchrotron X-ray diffraction (XRD) on thermally stress-annealed samples in a Ne pressure medium in the diamond-anvil cell at 28–62 GPa. Rietveld refinements of the diffraction patterns are significantly improved in fitting the positions and intensities of the split lines of CaPv if the starting model is a tetragonal perovskite-type structure with the SiO6 octahedral rotation around the tetragonal c-axis. The result is in contrast with other previous experiments, but is consistent with first-principles calculations, reconciling the discrepancy between computations and experiments on the crystal structure of CaPv. We attribute the observed difference to the formation of the thermodynamically more stable phase under improved stress conditions in our experiments. Our fitting shows that the bulk modulus of CaPv is 223 ± 6 GPa when its pressure derivative fixed to 4, which is also consistent with first-principles calculations. The previous observations of the diffraction patterns of CaPv inconsistent with the first-principles studies could be due to the formation of a metastable crystal structure of CaPv under elevated deviatoric stresses.

Asymptotic analysis of growing crack stress/deformation fields in porous ductile metals and implications for stable crack growth

Abstract: Asymptotic stress and deformation fields near a quasi-statically growing plane strain tensile crack tip in porous elastic-ideally plastic material, characterized by the Gurson-Tvergaard yield condition and associated flow rule, are derived for small uniform porosity levels throughout the range 0 to 4.54 percent. The solution configuration resembles that for crack growth in fully dense, elastically compressible, elastic-ideally plastic Huber-Mises material for this porosity range, except that the angular extents and border locations of near-tip solution sectors vary with porosity level, as do the stress and deformation fields within sectors. Increasing porosity is found to result in a dramatic reduction in maximum hydrostatic stress level, greater than that for a stationary crack; it also causes a significant angular redistribution of stresses, particularly for a range of angles ahead of the crack and adjacent to the crack flank. The near-tip deformation fields derived are employed to generalize a previously-developed, successful ductile crack growth criterion. Our model predicts that for materials having the same initial slopes of their crack growth resistance curves, but different levels of uniform porosity, higher porosity results in a substantially greater propensity for stable crack growth.

A Finite Element Algorithm for Microvoid Nucleation, Growth and Coalescence:

Abstract: A radial return algorithm is developed for large strain elasto-plastic struc tures in order to easily compute microvoid volume fraction rates. The basic feature subroutines are described in detail and forwards four typical problems are analysed: Q4 element tensile test, Q4 element compression test, notched cylinder tensile test and pipe bulging. The influence of microvoids volume fraction is clearly enhanced, mainly in regard to hydrostatic stress.