Numerical simulation of crack surface contacting behavior with stress-induced martensitic phase transformation in very-high-cycle fatigue regime

• A modified stress-induced kinetic model to characterize martensitic phase transformation. • Constitutive relation considering phase transformation to describe cyclic stress–strain. • A new FEA model to simulate crack contact stress in FGA region. • Simulated contact stress distribution between crack surfaces for positive and negative stress ratios. • Numerical simulations in agreement with FGA formation mechanism by NCP model. A modified kinetic model for the status of stress-induced martensitic phase transformation is developed, and the reliability of the resultant constitutive governing equations is verified by the experimental data of stainless steel AISI 348. Then, a numerical simulation, based on the established constitutive governing equations with martensitic phase transformation, is performed to address the process of microstructure refinement and nanograin formation due to the contact actions at crack surfaces in fine-granular-area (FGA) region in very-high-cycle fatigue (VHCF) process of metallic materials. A correlation between the calculated maximum contact stresses from the numerical model and the observed FGA thickness in experiments is confirmed for the stress ratios of −1, −0.5, 0.1 and 0.3 for a high-strength steel. The simulation results conform well to the FGA formation mechanism of numerous cyclic pressing (NCP) between originated crack surfaces, which causes grain refinement at originated crack wake and therefore induces the formation of FGA in high-strength alloys.