Prediction of fatigue crack initiation for rolling contact fatigue

In finite element (FE) simulations of a twin disc test of a wheel/rail contact, fatigue crack initiation criteria for elastic shakedown, plastic shakedown and ratchetting material responses were evaluated for a pearlitic rail steel BS11 normal grade. The Chaboche material model for nonlinear isotropic and kinematic hardening was used in the FE simulations. The ratchetting material response results were compared with a constitutive ratchetting model, and there was good agreement with respect to the number of cycles to crack initiation and shear strain distribution below the contact surface. In addition, angles for critical planes for crack initiation were calculated for both plastic shakedown and ratchetting material responses. Results from simulations with the ratchetting model at constant contact pressures and varying friction coefficient showed asymptotic values of the friction coefficient at which crack initiation due to ratchetting will not occur.