Wang Jian-hua

Analysis of the localization of damage and the complete stress-strain relation for mesoscopic heterogeneous brittle rock subjected to compressive loads

A micromechanics-based model is established. The model takes the interaction among sliding cracks into account, and it is able to quantify the effect of various parameters on the localization condition of damage and deformation for brittle rock subjected to compressive loads. The closed-form explicit expression for the complete stress-strain relation of rock containing microcracks subjected to compressive loads was obtained. It is showed that the complete stress-strain relation includes linear elasticity, nonlinear hardening, rapid stress drop and strain softening. The behavior of rapid stress drop and strain softening is due to localization of deformation and damage. Theoretical predictions have shown to be consistent with the experimental results.

Analysis of the Localization of Damage and the Complete Stress-Strain Relation for Mesoscopic Heterogeneous Rock Under Uniaxial Tensile Loading

The mechanical behavior of rock under uniaxial tensile loading is different from that of rock under compressive loads. A micromechanics-based model was proposed for mesoscopic heterogeneous brittle rock undergoing irreversible changes of their microscopic structures due to microcrack growth. The complete stress-strain relation including linear elasticity, nonlinear hardening, rapid stress drop and strain softening was obtained. The influence of all microcracks with different sizes and orientations were introduced into the constitutive relation by using the probability density function describing the distribution of orientations and the probability density function describing the distribution of sizes. The influence of Weibull distribution describing the distribution of orientations and Rayleigh function describing the distribution of sizes on the constitutive relation were researched. Theoretical predictions have shown to be consistent with the experimental results.

Solution of a rigid disk on saturated soil considering consolidation and rheology

The problem of a rigid disk acting with normal force on saturated soil was studied using Biot consolidation theory and integral equation method and the Merchant model to describe the saturated soil rheology. Using integral transform techniques, general solutions of Biot consolidation functions and the dual integral equations of a rigid disk on saturated soil were established based on the boundary conditions. These equations can be simplified using Laplace-Hankel and Abel transform methods. The numerical solutions of the integral equations, and the corresponding inversion transform were used to obtain the settlement and contact stresses of the rigid disk. Numerical examples showed that the soil settlement is small if only consolidation is considered, so the soil rheology must be taken into account to calculate the soil settlement. Numerical solution of Hankel inverse transform is also given in this paper.

STUDIES ON CHARACTERISTICS OF WELDING RESIDUAL STRESSES AND STRAINS IN THICK PLATE

ABSTRACT Of those features which influence the formation of welding cracks and the strength of pressure vessels, welding residual stresses and strains are very important. However the distribution characteristics of these factors have not been defined fully and clearly. In this paper welding residual stresses and strains are analysed for three types of weld on thick plate: a surface weld, a multi-repair weld, and a multi-pass weld. A thermal elastic-plastic technique is used under conditions of plane deformation. The results show that the triaxial residual stresses and plastic strains can accumulate to give relatively high values just below the surface and a short distance away from the weld area. As a consequence cold cracking may occur causing the fracture toughness to decrease. More attention must be paid to this aspect in the manufacturing of thick walled pressure vessels.