Propagation of sub-surface cracks in railway wheels for wear-induced conformal contacts

The ability to predict the criticality of internal cracks in railway wheels requires accurate knowledge of stress intensity factors KI, KII, KIII under contact loads. These factors depend both on the total load acting on the wheel and on how the load is transmitted through the wheel/rail interface, that is to say, they depends on the pressure distribution between wheel and rail. However, till today the solutions commonly used consider a theoretical (Hertzian) pressure distribution, even though the real contact patch may be far different for most of the lifespan of the wheel due to wear or to the dynamic conditions. In this paper an approach is developed with the aim of solving the case of an internally cracked wheel subjected to an arbitrary contact patch and pressure distribution. In particular, attention is focused on the case of hollow wear, which makes it possible to obtain very conformal contacts. The results are discussed and compared with the analytical solutions that consider Hertzian pressure distributions with the same total load.