Finite element analyses of rail head cracks: Influence of load characteristics on direction and rate of rolling contact fatigue crack growth

Abstract

The influence of operational loads on predicted rolling contact fatigue crack growth rates and directions in a rail head is studied. A 3D finite element based numerical framework is adopted featuring a 60E1 rail with an inclined surface-breaking, semi-circular gauge corner crack. The influence of magnitude and position of (normal) contact load, wheel–rail tractive forces, thermal loads, and rail bending under different support conditions is investigated. An accumulative vector crack tip displacement criterion is employed to predict crack growth direction, whereas growth rates are estimated using Paris-type relations. Results are assessed along the crack front for different crack radii. It is found that the crack growth rate is primarily influenced by the contact load magnitude and position. Additional rail bending and thermal loading will somewhat increase predicted growth rates, especially for larger cracks. Crack growth direction under combined loading generally depends on the ratio between the contact load and the bending/thermal load in that poor track support conditions and/or an increased thermal loading (cooling) promote downward growth. Results are useful for rail maintenance planning as illustrated in the study by quantifying the effects of loading conditions on estimated rail life.