Viscoplastic Ratcheting Response of Materials under Step-Loading Conditions at Various Cyclic Stress Levels

Abstract

The present study intends to assess ratcheting response of rate-dependent SS316L, SS316L(N), and 63Sn37Pb alloys under various step-loading conditions at room temperature through use of the Ahmadzadeh-Varvani (A-V) model developed based on a viscoplastic flow rule. The choice of viscoplastic description enabled the model to control plastic strain increments over loading progress at various stress rates. Predicted ratcheting over asymmetric loading cycles and multi-step cycles was influenced by cyclic stress levels, stress rates, and sequence of loading steps. Predicted ratcheting in steel samples SS316L and SS316L(N) over the second loading step in Low-High and High-Low loading sequences was primarily influenced with the stress amplitude in the second step. Multi-step-loading sequences High-Low-High and Low-High-Low in solder samples revealed how noticeable the impact of mean stress on ratcheting is. Predicted ratcheting values by means of the A-V model closely agreed with experimental data of alloys examined in this study.