Modeling fatigue life of structural materials under block-type nonsymmetrical loading

Abstract

In the framework of mechanics of damaged media (MDM), a mathematical model describing processes of thermo-plastic deformation and fatigue damage accumulation under low-cycle loading is developed. The MDM model consists of three interconnected parts: relations defining cyclic thermoplastic behavior of the material included for its dependence on the failure process; equations describing damage accumulation kinetics; a strength criterion of the damaged material.To assess the reliability and the scope of applicability of the defining relations of MDM, processes of plastic deformation and damage accumulation in a number of structural steels in low-cycle tests have been numerically analyzed, and the obtained results have been compared with the data from full-scale experiments. It is shown that the proposed MDM model qualitatively and, accurately enough for engineering purposes, quantitatively describes the main effects of the processes of plastic deformation and fatigue damage accumulation in structural alloys under block-type nonstationary nonsymmetrical low-cycle loading.