MSD in Fuselage Lap Joints: Requirements for Inspection Intervals for Typical Fuselage Lap Joint Panels with Multiple Site Damage

摘要

Inspection of failed aircraft structures and fractography on fatigue specimens have shown that after a high number of flights, cracks can appear simultaneously in riveted lap joints. When these crack tips approach each other, a mutual interaction causes an unexpected fast crack growth and next coalescence of cracks (unzipping effect). The term 'Multiple site damage' (MSD) is used when the mutual interaction of two or more damages (cracks) is noticeable. The report provides a model to predict the fatigue life of a riveted lap joint and the minimum necessary inspection interval for safe aircraft operation. A program (MSDSIM) has been developed to simulate the fatigue process and aircraft inspection. Input for this analysis are scatter data for initiation, the stress distribution between frames and the geometry of the structure.