A Risk Analysis Based Methodology for Widespread Fatigue Damage Evaluation

摘要

The Widespread Fatigue Damage (WFD) phenomenon is recognized by the aviation industry as one of the biggest threats on structural integrity, especially for ageing aircraft. This type of damage involves simultaneous evolution of cracks at multiple structural locations that are of sufficient size and density such that the structure might no longer meet its required residual strength. This paper proposes a methodology for WFD assessment, based on probabilistic analysis. Our approach is flexible in choosing Inspection Starting Point (ISP), Structural Modification Point (SMP) and inspection intervals, as long as a desired overall probability of failure is maintained. Based on our proposed approach, the operator can choose, for each structural detail which is prone to WFD, whether to adjust the inspection intervals, inspection threshold or the structural detail Limit Of Validity (LOV), all while maintaining an equivalent probability of failure. Special attention is given to a lap-joint analysis, including validation to test results published in the literature.