STUDY ON FATIGUE LIFE OF WIDE BOLTED LAP JOINT WITH MULTIPLE SITE DAMAGE

The fatigue tests of wide bolted lap joints with MSD were carried out under constant amplitude loading, and fracture surfaces were examinated. The fatigue lives of the specimens and, MSD initiation characteristic, crack front shape, and growth course were determined. The results show that the cracks of lap joints are not easy to be founded. The crack initiation stage and early crack growth (up to visible cracks) cover the major part of the fatigue life. When the crack was linked up for the first time, the residual lives are about 0.7%~9.4% of total fatigue life. Based on FRANC2D/L and AFGROW, a life predictive model for lap joints accounted for fastener load and, secondary bending, interference of cracks was developed to calculate the growth lives of MSD cracks. The results show that the results produced by using the life predictive model of lap joints with MSD have a close agreement with experimental results. The simulated results may be serving as a reference for damage tolerance design of the similar structures.