Fatigue life of cold expanded fastener holes at short edge margins

Abstract

The fatigue life of cold-expanded fastener holes with short edge margins was studied on aluminum 7075-T6 specimens with straight open holes. The study was done in two parts: experimentally and through finite element analysis. The experiments measured the total fatigue life and crack growth, and the results from the finite element analysis consisted of tangential residual stress profiles. The experiments showed that, at all edge distances, the fatigue life increased with the level of cold expansion. The edge distance, on the other hand, only had a significant effect at the highest level of cold expansion, with fatigue life decreasing at low edge distances. The finite element results were used to make fatigue life predictions that corresponded reasonably well with the experimental results. Strain-life was used for non-cold expanded holes, but crack growth had to be taken into account for cold-expanded holes.