Fatigue crack growth in wheel-rail rolling-sliding contact: A perspective of elastic-plastic fracture mechanics criterion

The presence of fatigue crack is a common damage pattern in railway wheel-rail system, which will reduce service life and increase the maintenance costs of railway transportation. In this study, a two-stage simulation strategy was proposed to investigate the elastic-plastic fatigue crack growth behaviour of the wheel and rail, where a three-dimensional wheel-rail rolling contact finite element model was first built to solve the elastic-plastic wheel-rail contact pressure and tangential traction modification, and then a simplified three-dimensional finite element model of the wheel and rail inserted with vertical cracks under the equivalent moving load was built to explore the fatigue crack growth. Taking the J-integral at the crack tip as an elastic-plastic crack growth parameter, the influences of crack face friction, crack depth and traction coefficient on the crack growth were elucidated. Meanwhile, the competing mechanisms of wheel/rail wear and fatigue crack growth under rolling-sliding contact condition was illuminated based on the Archard wear model. The simulation results indicate that two critical locations for crack growth appear during the contact load approaching and departing from the crack. The Mises stress near the deepest crack tip exceeds the yield stress, causing a small plastic zone with the greatest crack growth rate. The reduction in the crack face friction, and/or the increase in crack depth and traction coefficient will accelerate the propagation of fatigue crack. In the case of only normal contact load or rolling-sliding contact (μ ≤ 0.375), the crack growth on the wheel and rail is dominant compared to wear and crack will continue to grow.