Vibration measurements for contact topology assessment in a rolling contact fatigue bench

Rolling contact fatigue (RCF) plays a critical role in railway components, and the characterization of materials used, in terms of RCF life, is still an open task, made complex by the interactions of different phenomena, such as wear, cyclic contact, and ratcheting. The presented case study regards a bi-disk test bench, used to evaluate the RCF behaviour of wheel and rail steels. In the test, a wheel steel specimen rotates against a rail steel specimen, while pressed, the one against the other, by a constant force. A numerical simulation, based on a multiple source damage model and on parameters obtained from direct measurements during the test, is then used to determine properties of the material. The contact surface, in particular, plays a key role in determining the evolution of an RCF life test, since it has a direct impact on the pressure exerted and can change during the test, due to wear. The procedure proposed aims at using vibrations of a test bench during RCF-life tests to identify the contact topology, specifically understanding when damage phenomena cooperate to cause a quick flattening of the surface, and when this process is complete.