Competition between Fatigue Crack Growth and Wear under Rolling – Sliding Contact Condition

Abstract

A numerical model was developed to simulate the competition between crack initiation and growth by rolling contact fatigue (RCF) and wear in a railhead. The simulation model assumes that the materials are polycrystalline ferrite and pearlite and that RCF crack initiation is determined by the total accumulated plastic shear strain. The growth of short cracks is calculated using the Hobson model and the Archard model is used to calculate wear. In order to validate the developed model, twin disc rolling-sliding contact fatigue tests were performed. In the tests, rail material and slip ratio were changed and the crack initiation, crack growth and wear trace on the contact surfaces were investigated by SEM, EPMA and shape measuring instrument. Under these test conditions, simulations were performed using the developed model and compared the results. It was confirmed that the crack occurred at the nonmetallic inclusion/ferrite and ferrite/pearlite boundary at almost the same locations, therefore, the assumption of the model for the initiation was validated. It was also found that cracks of almost the same length and the direction existed in the vicinity of the contact surface at the same rolling cycles. Regarding wear, it was found that accurate analyses can be performed by considering the change of the contact pressure distribution and selecting an appropriate wear coefficient.