Stress gradient effects in surface initiated rolling contact fatigue of rails and wheels

Paper in proceeding, 2015

The paper investigates gradient effects, which relates to how highly stressed regions should be dealt with in fatigue design analyses. In particular stress gradients in rolling contact are investigated with a focus on differences in response between full or partial slip conditions. To this end the multiaxial state of stress beneath a wheel–rail contact featuring full or partial slip is quantified using a mulitaxial equivalent stress criterion. A comparative study shows that the significant differences in peak interfacial shear stress magnitudes between full and partial slip conditions are significantly reduced when translated to equivalent stress magnitudes. In addition, stress gradients beneath a frictional contact are compared to stress gradients outside a uniaxially loaded small hole in a plate and was found to correspond to hole radii in the order of 0.5– 0.7 millimetres for the cases studied. The study concludes that the use of local magnitudes of interfacial shear stress in the analysis of surface initiated rolling contact fatigue is conservative. The analysis framework established in the current study can be used to estimate the level of conservativeness.