Computer simulation of strain accumulation and hardening for pearlitic rail steel undergoing repeated contact

This paper presents a validated model of plastic strain accumulation in railway rail steel under repeated wheel-rail contact. Such contacts subject the rails to severe stresses, taking the material local to the contact beyond yield, and leading to the incremental accumulation of plastic deformation (ratheting) as wheels pass. This process is at the root of several rail wear and rolling contact fatigue crack growth mechanisms. Existing plasticity models are inadequate for modelling the strain accumulation taking place in this material, which is under high hydrostatic compression (of the order of 1 GPa) and is severely anisotropic. The model described here is based on a ratcheting law derived from small-scale twin-disc rolling-sliding contact experiments and simulates tens of thousands of ratcheting cycles and the corresponding strain hardening in a few minutes on a personal computer. Results indicate that, to model these processes successfully, and to represent correctly the high levels of ductility seen in rail steels under compressive load, stress-strain data generated under high hydrostatic compression are required.