On Through Cracks at Interference Fit Fasteners

Abstract

Approximate stress intensity factors (SIF’s) are derived for through-the-thickness cracks originating at an interference fit fastener- (IFF-) filled hole in a uniaxially loaded plate. SIF’s are determined using a previously formulated procedure of deriving approximate SIF’s from the normal stress distribution at the location of the crack in an uncracked plate. An approximate elastic-plastic solution for the normal stress distribution is derived for a uniaxially loaded plate containing an IFF-filled hole. Stress distributions obtained from the approximate solution compare well with those obtained from elastic-plastic finite element analyses for various loading conditions, interference levels and fastener plate material combinations. SIF’s for through cracks at IFF’s are presented graphically for various ratios of crack length to hole radius and diametral interference to hole diameter, applied uniaxial stresses and the plate-fastener material combinations. Finally, these SIF’s are used to predict residual cyclic lives of test specimens containing through cracks at IFF’s. Agreement between the calculated and actual lives is very good.