No abstract

The main physical laws of thermal-plastic deformation and fatigue damage accumulation processes in polycrystalline structural alloys under various regimes of cyclic thermal-mechanical loading are considered. Within the framework of mechanics of damaged media, a mathematical model is developed that describes thermal-plastic deformation and fatigue damage accumulation processes under low-cycle loading. The model consists of three interrelated parts: relations defining plastic behavior of the material, accounting for its dependence on the failure process; evolutionary equations describing damage accumulation kinetics; a strength criterion of the damaged material. The plasticity model based on the notion of yield surface and the principle of orthogonality of the plastic strain vector to the yield surface is used as defining relations. This version of defining equations of plasticity describes the main effects of the deformation process under monotone cyclic, proportional and nonproportional loading regimes. The version of kinetic equations of damage accumulation is based on introducing a scalar parameter of damage degree and energy principles, and account for the main effects of nucleation, growth and merging of microdefects under arbitrary regimes of low-cycle loading. The strength criterion of the damaged material is based on reaching a critical value of the damage degree. The results of numerically modeling cyclic thermal-plastic deformation and fatigue damage accumulation in heat-resistant alloys (Nimonic 80A, Haynes 188) under combined thermal-mechanical loading are presented. Special atten-Communicated by Andreas Öchsner.

A direct approach of the boundary element method for treating 3-D boundary-value problems of poroelastodynamics is considered. Biot’s material model with four unknown base functions is used. Computational results for the surface responses of displacements and pore pressures as functions of a force acting on a half-space weakened by a cavity are presented.

Processes of plastic deformation and damage accumulation in polycrystalline structural alloys are investigated under block-type, nonstationary, nonsymmetric cyclic loading. In the framework of damage mechanics, a mathematical model is proposed that effectively describes elastoplastic deformation and fatigue related damage accumulation processes under low-cycle loading. This model can be subsumed under three main parts: the relations defining elastoplastic behavior of the material; the equations describing damage accumulation kinetics; the strength criterion of the damaged material. For validating the model, we perform a numerical analysis and a comparison with the data from full-scale experiments. We demonstrate that the proposed model qualitatively and quantitatively describes the main effects of plastic deformation and damage accumulation processes in structural alloys under complex loading scenarios. Moreover, fatigue related lifetime of the structure is accurately captured by this model as well.

No abstract