Cyclic ratchetting and failure of a pearlitic rail steel

Abstract

Two-dimensional elastic-plastic finite element (FE) simulations of a rolling contact problem are presented. The objective was to evaluate three elastic-plastic material models, all of them able to simulate decay in ratchetting rate, by studying the cyclic ratchetting material response and failure of a pearlitic rail steel. The FE simulations, which were performed for different magnitudes of contact pressure and traction forces in the rolling contact, provided cyclic ratchetting material responses. The results showed a large accumulation of shear deformation of the surface at the rolling contact. The critical plane (crack plane) for crack initiation was found by using a multiaxial fatigue damage model. The life to crack initiation on the crack plane was calculated using this model, as well as an empirical model for failure by ratchetting, for comparison. The results from the evaluation of the three material models show that the material model which could best mimic the stress-strain cycles and ratchetting rate, from cyclic uniaxial experiments, was also able to resolve the stress and strain field correctly in the FE simulations and to give reliable results. Low-cycle fatigue governed fatigue crack initiation, and the angles calculated for the crack plane showed good agreement with observations from experiments.