Fundamental Investigations of Fretting Fatigue : Part 3, Some Phenomena and Mechanisms of Surface Cracks

Abstract

It has been known that the fatigue strength related to fretting is significantly reduced and that non-propagating fatigue cracks are often observed in the superficial layer of fretted area. In order to clarify the causes of such phenomena, the initiation of fatigue cracks is investigated in relation to the contact stresses caused by fretting. The main results obtained are as follows. (1) The reduction of fatigue strength is mainly attributed to the stress concentration caused by the frictional force due to fretting. Fatigue cracks are located at the stress concentrated area. (2) The fatigue cracks show inclinations to the surface, and the direction can also be explained by the contact stresses.