The Fatigue Behavior of Fastener Joints

The fatigue behavior of Hilok fastener joints under constant amplitude loading has been investigated experimentally. The effects of load transfer in an unbalanced joint configuration was characterized in terms of a stress severity factor relative to the open-hole configuration. The experimental data indicates that the clamp-up forces dominate the performance of fastener joints with the open-hole fatigue life being the lower bound at the stress levels investigated. The failure modes were observed to transition from a net-section type failure across the minimum section to a fretting induced failure at some distance from the hole. The experimental data has been used to develop stress severity factors to be used as a measure of the fatigue quality of the fastener joints.