Residual Strength Predictions for Riveted Lap Joints in Fuselage Structures
In general, aircraft fuselages experience fatigue crack growth. At the upward part of the very last cycle, however, crack propagation involves a considerable amount of stable tearing followed by fast final failure. The term residual strength corresponds to the applied load level at which unstable crack growth occurs. As already said in Chap. 8, the increasing usage of aging aircraft triggered the attention to the problem of MSD. A host of experimental works on simple specimens and complicated fuselage structure panels with riveted joints have demonstrated that, compared to the case of a single lead crack only, the crack arrest capability and residual strength is degraded when the same lead crack is accompanied by smaller collinear MSD cracks (cf. Sect. 8.2.6). In parallel, an extensive research effort has been dedicated to quantifying the reduction of residual strength due to MSD. Analytical predictions of residual strength require the application of appropriate criteria to determine crack link-up and final failure. A number of various methodologies for predicting residual strength in the presence of MSD, some of them employing very sophisticated analysis tools, have evolved. In this chapter, however, only approaches most thoroughly confronted with experimental results and claimed to be most suitable for aircraft fuselage panels are considered. Next, selected from the literature comparisons between predicted and observed results on residual strength of flat and curved panels with riveted lap joints containing either a single crack or a lead crack and MSD cracks are presented.