Hydrostatic stress

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

A fracture mechanics investigation on crack growth in massive forming

Abstract: To understand the crack growth in massive forming and to consequentially avoid crack growth in workpieces, it is necessary to investigate its dependence on the crack depth and thus on the state of hydrostatic stress. Prior work shows that the crack opening displacement (COD) for shallow cracked tension specimens with low stress triaxiality is twice as high as for deep cracked specimens with high stress triaxiality. This work examines the crack growth in compression specimens with pre-cracked cylindrical upsetting samples. The compression samples were cut in the stress symmetry plane in order to observe crack initiation and crack growth by a single specimen technique. In this way it is possible to observe blunting, crack initiation and crack growth inside the upsetting specimens. The resulting COD does not differ significantly from the values achieved in tension samples with short surface cracks.

An Analysis of Phase Transformations for Porous Shape Memory Alloy Considering Hydrostatic Stress

Abstract: According to micromechanics, consider the porous shape memory alloy (SMA) as a composite-sphere model. Isolate a constant thickness spherical shell which is composed of SMA, and is traction free on its inner surface and subjected to the uniform hydrostatic pressure and the deviatoric stress on its external surface. Then, a constitutive model for porous SMA considering hydrostatic stress is proposed by elasticity solution. The stress distribution of the spherical shell was calculated. Corresponding to different applied stresses, the spherical shell is divided into different regions of pure austenite, pure martenite, and austenite/martensite mixture under isothermal circumstances. The martensite volume fraction is then obtained. The predicted results have been compared with the obtained experimental data by Zhao and Sia Nemat-Nasser. It shows that the modeling results are in good agreement with the experiments and the initial phase transition point for porous SMA is lower than the dense SMA.

3-Dimensional elastic-plastic finite element analysis of stress-induced voiding in Cu damascene interconnects of ultra-large-scale integrated circuits

Abstract: In order to discuss stress-induced voiding (SIV) of Cu damascene interconnect structures in ultra-large-scale integrated circuits (ULSls), 3-D elastic-plastic finite element analysis (FEA) was carried out based on stress-temperature behavior of constituent thin films measured by a wafer curvature method. Two types of Cu interconnect geometries with either D-SiN cap/p-SiON etch-stop layers or D-SiCN : H cap/p-SiC : H etch-stop layers were analyzed. The effect of the Cu line width was also investigated. It was found from the FEA results that, regardless of the geometry, the hydrostatic tensile stress of Cu in the structure with D-SiCN : H/p-SiC : H layers was generally lower than that with p-SiN/p-SiON layers. It was also expected that, for the structure with p-SiN/p-SiON layers, SIV is most likely to occur near the via center while for the structure with p-SiCN : H/p-SiC : H layers, it is most likely to occur near the via bottom. In the structure with D-SiCN : H/p-SiC : H layers, it was considered that a larger line width is susceptible to voiding in the via due to a high hydrostatic stress gradient in the via and a high magnitude of equivalent plastic strain in the line.

A dynamical approach to study the time dependent behavior ofthe Kuhbanan fault zone (Kerman – Iran)

Abstract: . In this research a proposed methodology is improved to identify how the stresses increase between two Earthquakes in Kuhbanan fault zone (Iran). Using the Mohr circles of the Earthquake we could calculate the main stress (σ1), hydrostatic stress, normal and shear stresses and the initial and final Coulomb stresses for all individual Earthquakes. For the relation of the whole fault we need the initial and the final Coulomb stress as well as the time during which the stress reaches from initial value to the final Coulomb failure value. The initial Coulomb stress is chosen as the least value, to be 30 megapascal. For the final Coulomb stress we used the average final Coulomb stress of all Earthquakes and for the time between this two initial and final stress we use the average time between Earthquake that is 3377 days. Using the Coulomb stresses at selected times, one can see how the stress increase with time between Earthquakes. The best fit of points of stress versus time is a polynomial relation. The model will help to estimate the stress accumulation with time until the next event, this means one can estimate the approaching time to the next main shock.

Finite element analysis on near-tip fields under mixed mode conditions

Abstract: A large deformation finite element analysis has been performed to study the stress and strain fields near the crack-tip under mixed mode conditions. The effects of microvoids on plastic flow are taken into account by using the continuum constitutive model introduced by Gurson. Influence of hydrostatic stress and strain hardening exponent on the near-tip field is examined.