A non-collinear fretting-fatigue experiment to compare multiaxial fatigue criteria: critical shear plane strategy is better than invariant formulations

Fretting-fatigue crack nucleation is usually predicted from multiaxial fatigue criteria combined with non-local approaches to take account of fretting stress gradient. Conventional collinear fretting-fatigue loadings, being effectively uniaxial near the hotspot surface contact border, lead to similar predictions whatever the non-local approach and fatigue criterion. To differentiate between approaches, a new non-collinear fretting-fatigue set-up was developed applying fatigue stress at a β-angle to the fretting direction. Using this device, the crack nucleation condition of 35NiCrMo16 steel was investigated as a function of the β-angle. 3D elastic simulations enabled, for the first time, performance to be compared between critical plane versus invariant formulations. Experiments and modeling suggested that the McDiarmid criterion provides the best crack nucleation predictions.