Volume 7, Issue 3 (March 2010)
A Non Local Multiaxial Fatigue Approach to Account for Stress Gradient Effect Applied to Crack Initiation in Fretting
Although fatigue limits of smooth specimens under various complex loadings have been determined, few models have been proposed to predict well-known experimental results such as size effects and stress gradient effects. This paper addresses the stress gradient effect issue. A new non local multiaxial fatigue approach is proposed and applied to rotating bending and fretting experiments. The proposal takes as a starting point the rotating bending results and stress gradient analysis of a cylinder-plane contact in partial slip sliding regime. Both weight function and “process volume,” used to compute the mean value of the weight function, are introduced in a phenomenological way. The weight function reflects the experimental trend of fatigue limit under rotating bending whereas the connected process volume allows dealing with special stress gradient induced by cylinder-plane contact under partial slip. The proposal shows good capabilities to predict four-point rotating bending fatigue limit and crack initiation of a similar Inconel 718 cylinder/plane contact under partial slip regime.