A Procedure for Wheel and Rail Steels Characterization in Rolling Contact

A procedure for wheels and rails material characterization is still an open task in railway industry. Common standardized procedures, both for calculations and experimental characterization of materials and components, are usually founded on empirical models, or on simple and controlled damage phenomena, such as wear, unidirectional or bidirectional strain. In this study, a procedure for characterizing wheel and rail materials, considering the complex interaction between different failure mechanisms that can occur at the loaded regions of wheels and rails, is proposed. Rolling contact tests were carried out by a bi-disk machine on couples of specimens of wheel and rail materials (ER8 EN13262 and UIC 900A, respectively), in various conditions of contact pressure and sliding ratio. In general, the main damage phenomenon was crack formation due to unidirectional plastic flow (ratcheting); a role of non-metallic inclusions (sulphides) as preferential crack nucleation site was observed; wear partially mitigated this phenomenon by removing layers of severely strained material from the surface. A calculation procedure for elaborating the experimental data is proposed: it allows considering the interaction of inclusions, ratcheting and wear, obtaining the characterization of materials for wheels and rails.