Influence of a highly deformed surface layer on RCF predictions for rails in service

Rolling Contact Fatigue (RCF) cracks often initiate from the surface layer of rails, where large accumulated plastic deformations influence the mechanical and fatigue properties of the rail material. Additionally, changes in profile geometry due to both plasticity and wear result in alternating contact locations and conditions. The goal of this study is to investigate the importance of considering these effects when predicting surface RCF crack initiation in rails. We analyze their individual impact on stress and strain fields, as well as fatigue crack initiation, by finite element simulations of railheads subjected to a mixed traffic situation. To account for deformation-dependent material behavior, an anisotropic plasticity model is calibrated against experiments with different amounts of accumulated shear strains measured in field samples. Finally, a recently developed crack initiation criterion is employed that accounts for the influence of plastic deformations. Under extreme loading conditions, i.e., full slip with a traction coefficient of 0.4, it is shown that both deformed near-surface material and deformed geometry reduce the predicted RCF fatigue damage significantly, by factors of about 5 and 30, respectively. Furthermore, not accounting for the combined effect of deformed material state and geometry leads to approximately 150 times larger predictions of RCF damage. • A distribution of accumulated shear strains in a railhead is proposed. • A material model accounting for an anisotropic yield surface is adopted and calibrated. • Spatially varying material properties in a railhead cross-section are defined. • FE simulations of wheel passages for four rails under operational traffic are done. • Deformed material and geometry reduce fatigue damage accumulation rate.