Finite element analysis of fracture mechanics and contact mechanics of wheel-rail

In this paper, wheel-rail contact problem in presence of rail surface crack is investigated. The reason for investigating this problem is significant effect of wheel-rail contact on stress intensity factors and also the effect of crack on contact pressure distribution. In this research by using finite element method and a commercial software, wheel-rail are modeled under partial slip rolling condition. Contact elements are used to model the interactions between the wheel-rail contact surfaces and the crack surfaces. Stress intensity factors are calculated through a numerical displacement extrapolation method. The effects of crack orientation, crack length and contact on the stress intensity factors and contact pressure are studied. The results indicate that KII has greater than KI, therefore, shear mode may dominate the tip behavior in this wheel-rail contact problem. as the wheel passes over, the complicated crack edge deformation changes the direction of interfacial shear stress and this causes variation in KII. Fluctuation in KII is the main factor of fatigue crack propagation in the wheel-rail contact problem. The contact pressure is singular when the crack is located in wheel-rail contact zone. Hence, the assumptions of Hertzian contact pressure may not be valid when investigating wheel-rail contacts in the vicinity of a crack.