Characterization of Fretting Fatigue Process Volume Using Finite Element Analysis

Fretting fatigue damage is characterized by the nucleation of cracks very early in the life of a component along a critical plane at an oblique angle to the contact surface. The number of cycles to fretting fatigue crack nucleation as well as the orientation of the initial crack critical plane is strongly influenced by the large stress and strain gradients that occur within a small volume near the fretting contact. Therefore, it is necessary to average the stresses and strains along a critical plane within a fretting fatigue process volume (FFPV) to obtain more reliable crack nucleation predictions. An approach for computing damage in a FFPV using finite element analysis is presented. The life and crack angle prediction is consistent with experimental observations of fretting fatigue tests on PH 13-8 Mo stainless steel. This averaging method allows for the introduction of a length scale for crack nucleation prediction.