Experimental Study on Fatigue Life of Wide Bolted Lap Joint

Abstract

Due to the complexity of the geometrical configuration and loading conditions, especially for multiple site damage(MSD). In this paper, four fatigue tests of wide bolted lap joint with MSD inserted along the upper row were carried out under two different constant amplitude loading with marker band. The simultaneous propagation of multiple cracks in the test was monitored continuously by aid of a specially developed image analysis technique. Through fractographic examination, MSD initiation characteristic, crack front shape, and growth course were determined. The results show that the crack initiation stage and early crack growth (up to visible cracks) cover the major part of the fatigue life. When crack grows beyond the bolt heads, the residual lives only have 15%~30% of total fatigue life. The greater the stress level is, the smaller the relative residual life will be. When the crack was linked up for the first time, the residual lives are only 0.7%~2.1%. After the second linked up, fatigue lives are only remaining 0.01%~0.03%.