A Comparison of Two Methods Modeling High-Temperature Fatigue Crack Initiation in Ferrite-Pearlite Steel

Abstract

High-temperature fatigue tests are carried out to investigate the fatigue crack initiation behavior of ferrite-pearlite steel. Two approaches to modeling fatigue crack initiation under high temperatures in ferrite-pearlite steel are developed and compared in this study. In the first approach, basal energy is introduced as the criterion for crack initiation. Various initial basal energy values are assigned to each potential location. The increments in basal energy after each cycle can be calculated. In the second approach, a crystal plasticity model is developed, combined with the cyclic hardening/softening effect and three fatigue indicator parameters (two of them are adopted from previous works and one is developed in this work). Results indicate that both approaches are capable of predicting the fatigue crack initiation location and the corresponding life. The first approach requires a lower computational cost but has many limitations, and the second approach is suitable for calculating mesoscale stress and strain distributions but with a higher computational cost.