Stress intensity factor correction for asymmetric through-thickness fatigue cracks at holes

Abstract

This study concerns the growth of fatigue cracks from fastener holes. Cracks growing from fastener holes may evolve a complex eccentric shape, which makes calculation of the stress intensity factor problematic. This is particularly true for cases such as cold expanded holes, where there can be a through-thickness variation in the residual stress field. A methodology for the empirical derivation of corrections to the stress intensity factors, on account of crack asymmetry, is presented for the case of cracks emanating from holes in remotely loaded finite width strips. The proposed methodology may be useful for any other practical application for which an eccentricity correction is not available from analytical or numerical solutions. A comparison with stress intensity factor solutions developed for asymmetric cracks in finite width strips without holes, shows that the effect of a hole is to give a greater increase in the stress intensity factor with increasing eccentricity compared with a similar geometry without a hole.