Hydrostatic stress

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

Using infrared thermography to study hydrostatic stress networks in granular materials

Abstract: The macroscopic mechanical behaviour of granular materials is governed by microscopic features at the particle scale. Photoelasticimetry is a powerful method for measuring shear stresses in particles made from birefringent materials. As a complementary method, we here identify the hydrostatic stress networks through thermoelastic stress analysis using infrared thermographic measurements. Experiments are performed on two-dimensional cohesionless monodisperse granular materials composed of about 1200 cylinders comprising two constitutive materials. We show that the experimental hydrostatic stress distributions follow statistical laws which are in agreement with simulations performed using molecular dynamics, except in one case exhibiting piecewise periodic stacking. Polydisperse cases are then processed. The measurement of hydrostatic stress networks using this technique opens new prospects for the analysis of granular materials.

On phase transformation behavior of porous Shape Memory Alloys.

Abstract: This paper is concerned on the phase transformation mechanism of porous Shape Memory Alloys (SMAs). A unit-cell model is adopted to establish the constitutive relation for porous SMAs, the stress distributions, the phase distributions and the martensitic volume fractions for the model are then derived under both pure hydrostatic stress and uniaxial compression. Further, an example for the uniaxial response under compression for a porous Ni–Ti SMA material considering hydrostatic stress is supplied. Good agreement between the theoretical prediction of the proposed model and published experimental data is observed.

Calibration of Velocity-stress Relationships Under Hydrostatic Stress For Their Use Under Non-hydrostatic Stress Conditions

Abstract: We have computed stress sensitivity parameters for intrinsically transverse isotropic (TI) shales and sandstones under hydrostatic stress using literature data from Wang (2002b). We use the three-parameter non-linear model that relates the whole stiffness tensor and the whole stress tensor. We introduce physical and empirical constraints in the inversion of parameters c111, c112, c123 to compensate for the absence of non-hydrostatic stress data. The constraints c111 < c112 and c155 < c144 ensure respectively that P-waves are dominated by the stress in the polarization direction and S-waves by stresses in the polarization and propagation direction. We confirm the validation of the model for all 16 shale samples and 10 out of 20 sandstone samples (35 MPa stress range) when intrinsic anisotropy is present and greater than 4.5 %. Sand samples show higher stress sensitivity than shale samples. With this methodology, we suggest that velocity-stress relationships can be calibrated in the lab under hydrostatic stress and then used under non-hydrostatic stress conditions.

Pressure Dependence of Ferroelectric Properties in PbZrO3-PbTiO3 Solid State System under Hydrostatic Stress

Abstract: Pressure dependence of ferroelectric properties in PbZrO3-PbTiO3 solid state system (PZT) were calculated under hydrostatic stress and compared with experimental results. When the ratio of electrostrictive coefficients in PZT, Q11/Q12 was exactly equal to -2.000, the ferroelectric properties were not affected by the application of hydrostatic pressure; i.e. isotropic compressive stress. At ratios other than Q11/Q12=-2.000, the Curie points were decreased with increasing hydrostatic pressure, in particular near the morphotropic phase boundary (MPB). The piezoelectric charge and voltage coefficients, d ij and g ij, increased and decreased, respectively, near the MPB with increasing hydrostatic pressure, due to the pressure dependence of the dielectric constant and spontaneous polarization.