Modeling for cyclic plasticity and rate dependence of metal materials with a new non-unified viscoplasticity model

Abstract

The classic unified viscoplasticity model has achieved great success in areas such as cyclic plasticity, time-dependent behavior, and creep–fatigue interaction. However, the unified viscoplasticity model may be inadequate to describe inelastic strain rate with static recovery term. Our previous study [Chen, Kitamura, Feng (Int J Fatigue 112:70–77, 2018)] of 316L stainless steel has shown that adding a static recovery term predicts an accelerating creep strain rate in the creep–relaxation interaction tests, which is inconsistent with the experimental test results. In this study, a modified non-unified viscoplasticity (NUV) model is proposed based on the mechanism of viscous glide. The parameter determination process and the role of different parts of the model are illustrated using experimental data drawn from Al 5083; then, the proposed model is verified by simulating the test of 316L stainless steel. The modeling results show that the proposed NUV model accurately predicts the strain rate evolution during the creep–relaxation interaction tests and other behaviors, i.e., cyclic plasticity and loading rate sensitivity. As with fewer parameters and more concise equations, the proposed NUV model is a good choice for engineering applications.