Retardation of cracks emanating from fastener holes

Abstract A limited number of cold expansion and interference fit fastener systems were evaluated to determine their capability to retard the growth of cracks emanating from fastener holes. The fastener systems were applied to specimens fabricated from 7075-T6 aluminum. In all cases the fastener holes had fatigue cracks emanating from them before the fastener system was applied. Some samples that were used as baseline were fitted with non-interference fit fasteners. All samples were tested in constant amplitude fatigue at an R ratio of 0.5 at maximum stresses of 20 or 30 ksi. The results show that a cold expansion or properly installed interference fit fastener system significantly retards the growth of preexisting cracks emanating from fastener holes irrespective of the amount of load transfer through the joint.