An integrated model for competitive damage mechanisms assessment in railway wheel steels

A procedure for damage assessment in wheel-rail contact is still an open task: much work has been done for understanding failure mechanisms such as wear, cyclic plasticity and rolling contact fatigue, but only recently the competition between them has been taken into account. In this study, a numerical procedure for damage assessment of railway wheel steels, considering the complex interaction between various failure phenomena that can occur at the loaded region, is proposed. The procedure is based on various damage mechanism models, integrated into an overall simulation method able to take into account their reciprocal influence. The model was applied for characterizing a railway wheel steel (ER8 EN13262), through the elaboration of the results of rolling-sliding experiments, determining the plasticity and the wear model constants that can be used for damage assessment of real wheels. The experiments showed that the main damage phenomenon was surface crack formation due to unidirectional plastic flow (ratcheting); in presence of water these cracks propagated causing very severe damage. A role of manganese sulphides non-metallic inclusions as preferential site for subsurface crack nucleation was observed. A quantitative evaluation of these phenomena was provided.