Competition between wear and rolling contact fatigue at the wheel-rail interface: some experimental evidence on rail steel

Recent studies of the rail–wheel interface have shown that wear and rolling contact fatigue (RCF) are competitive phenomena.Wear, by removing the material from the contact surface, tends to limit the propagation of cracks formedby cyclic contact stresses. Several parameters influence these phenomena. This article studies the effects of various working conditions on the surface damage of railway steels. The competition betweenwear and RCF is particularly strong in dry rolling–sliding contacts, in which the damage severity of our test cases can be adequately predicted using the shakedown map. In wet contacts, RCF is prevalent: cracks rapidly propagate into the subsurface layer in response to hydraulic pressure penetration and then branch towards the surface causing severe damage (macroscopic pitting). The severity of this phenomenon depends strongly on the applied load and cannot be inhibited by wear due to the low friction. On the basis of these results, a general procedure is proposed to the structural integrity of rails.