Study on fracture mechanics analysis of residual strength of structure with multiple site damage

The residual life will be reduced because of multiple site damage(MSD) in ageing aircraft. For the fuselage structure with longitudinal riveted joints, a method of computing residual strength of structure with MSD was presented. Basing on two models of cracks growth, one parameter and three parameters models, the way of analyzing the stage of initiation and stable tearing was discussed in details. Irwin and Dugdale models were used to calculate crack tip opening displacement (CTOD). Swift criterion was used to describe the stage of crack link-up. Combining with those fundamental fracture mechanics theories, an integrated method to analyze MSD structures' residual strength for all stages of crack propagation under increasing loading was expounded. To verify the method, the model of typical fuselage butt-joint was analyzed by the presented method. The result shows that the method can well cope with the several stages of crack propagation, and the computed results agree well with the experimental ones.