Simulation of Ratcheting Behavior and Prediction of the Fatigue Life of HRB400 Steel Based on Crystal Plasticity Analysis

In this study, the ratcheting behavior of HRB400 steel throughout its entire life cycle was investigated through experimental tests and crystal plasticity numerical simulations. The relationship between fatigue life and the evolution of grain–level deformation inhomogeneity was explored. The results demonstrate that strain/stress amplitude, mean stress, peak stress, and yield strength significantly influence the cyclic hardening/softening characteristics and ratcheting behavior during the initial loading stage. These effects were quantified using a back stress evolution function that incorporates both peak stress and stress amplitude. Furthermore, the statistical standard deviation of strain, serving as an indicator of deformation inhomogeneity, was established as a fatigue indicator parameter (FIP). Subsequently, the method for predicting the lives of the material corresponding to different types of fatigue failures was developed. This method was successfully applied to low–cycle fatigue (LCF) life prediction for specimens subjected to controlled strain/stress loading cycles, with its validity confirmed through experimental measurements.