Effects of rolled edges on the fatigue life of shot peened Inconel 718

Shot peening on part edges is a critical operation in aerospace manufacturing. Edges are plastically deformed by the shot peening media, which can create stress concentration features known as “rolled edges”. The detrimental impact of rolled edges on fatigue life has already been observed in the literature. However, the effects of the geometries of the unpeened edges on rolled edge formation and on the resulting fatigue life have never been published in the open literature. This study presents the effects of different shot peened edge geometries on the fatigue life of Inconel 718, in high and low cycle fatigue. Chamfered, sharp and rounded edges were prepared, shot peened, and fatigue tested. An analysis of crack initiation mechanisms and fatigue lives showed that shot peened sharp edges represent the worst configuration tested in terms of fatigue life and that shot peened rounded edges do not improve the fatigue life when compared to chamfered shot peened edges.