Evaluation of mixed-mode crack growth direction criteria under rolling contact conditions

Fatigue crack growth direction criteria are evaluated towards a twin-disc experiment from the literature. The experiment is modelled numerically at different crack lengths accounting for the effect of crack-face friction. Based on numerically evaluated stresses, strains and displacements, a range of crack growth direction criteria from the literature are evaluated and compared to the experimentally found crack growth directions. In the considered experiment, the growth is found to be essentially shear driven. Of the evaluated criteria employed to linear elastic plane strain analyses, the Maximum Shear Stress Range (MSSR) and Vector Crack-Tip Displacement (VCTD) criteria are found to be able to capture the experimentally obtained crack growth direction throughout the fatigue life. Crack-face friction was found to impose a small effect on directions predicted by these criteria.