Modeling for Cyclic Plasticity of Gradient Nanostructured Metals and Fatigue Life Prediction

This paper proposes a theoretical model for the description of tension-compression cyclic plasticity of gradient nanostructured (GNS) metals. The gradient grain size effect is considered by introducing the Hall-Petch relation for local yield stress and strain hardening. With the experimentally measured grain size distribution profile, the average axial stress can be calculated for cylindrical GNS metal specimens. The model was verified using experimental data obtained from 316L stainless steel treated by surface mechanical rolling treatment (SMRT). Moreover, the corresponding strain energy for cyclic plasticity can be calculated from the constitutive equations, providing an energy-based approach to explain the fatigue life of gradient 316L stainless steel.