Hydrostatic stress

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

In Situ Structural Evolution of Steel-Based MMC by High Energy X-Ray Diffraction and Comparison with Micromechanical Approach

Abstract: In situ high energy X-ray diffraction synchrotron was used to provide direct analysis of the transformation sequences in steel-based matrix composite (MMC) reinforced with TiC particles. Evolution of the phase fractions of the matrix and TiC particles as well as the mean cell parameters of each phase were determined by Rietveld refinement from high energy X-ray diffraction (ID15B, ESRF, Grenoble, France). In addition, some peaks were further analysed in order to obtain the X-ray strain during the cooling step. Non-linear strain evolutions of each phase are evidenced, which are either associated with differences in the coefficient of thermal expansion (CTE) between matrix and TiC particle or to the occurrence of phase transformation. Micromechanical calculations were performed through the finite element method to estimate the stress state in each phase and outline the effects of differences in CTE and of volume change associated with the matrix phase transformation. The calculated results led to a final compressive hydrostatic stress in the TiC reinforcement and tensile hydrostatic stress in the matrix area around the TiC particles. Besides, the tendencies measured from in situ synchrotron diffraction (mean cell parameters) matched with the numerical estimates.

Simulation of deformation behavior of porous Titanium using Modified Gurson yield function

Abstract: In this research the stress-strain curve of porous Titanium, as a common material for biomedical application, was predicted using the mechanical properties of fully solid Titanium experimental data. Modified Gurson model (Gurson-Tvergaard-Needleman (GTN) model) was used to predict the plastic response of porous Titanium in compaction. Different values of GTN parameters were used for different initial porosity. It was recognized that volume constancy assumption during plastic deformation of porous media cannot be satisfied due to both of changes in porosity and hydrostatic stress contribution on yielding. It was found that consideration of porosity variation is necessary during deformation for accurate modeling. Also, porous samples represented the same lateral expansion under less axial displacement relative to fully solid sample regarding the GTN model. The stress distribution of porous samples was different from solid sample considering the GTN model and this was predicted different shear banding. Evolution of porosity during deformation leads to linear like stress response in the plastic deformation regime.

組合せ引張り-ねじり状態における結晶性高分子pom材の繰返し応力・ひずみ関係

Abstract: In order to construct a constitutive equation for polymeric solids, cyclic combined tension-torsion tests were performed using polyoximethylene (POM) at strain paths such as proportional, cruciform, rhombus and circular ones to investigate the effect of strain history on the stress-strain curve. It was shown that : (1) cyclic softening occurs for all strain paths tested here, (2) stress response for all strain paths is influenced by the hydrostatic stress component, (3) stress softening for the circular strain path greatly depends on the previous strain path and (4) stress relaxation after several stroain cycles strongly depends on the direction of the present strain.

Effect of hydrostatic pressure on the strength properties of polymer materials

Abstract: On the assumption that the strength characteristics of homogeneous polymer materials depend on the specific volume, equations are derived for the dependence of the strength or high-elastic limit on the hydrostatic component of the stress tensor and temperature. The ultimate strengths in simple tension, compression and shear are considered in relation to brittle and plastic fracture.