A Risk Analysis Based Methodology for Widespread Fatigue Damage Assessment

摘要

The Widespread Fatigue Damage (WFD) phenomenon was recognizedby the aviation industry as one of the biggest threats on structuralintegrity, especially for aging aircraft. This type of damage involvessimultaneous evolution of cracks at multiple structural locations that areof sufficient size and density such that the structure might no longer meetits required residual strength. Several approaches were suggested over thepast three decades for WFD assessment and to establish maintenanceprogram, if applicable, to preclude WFD in fleet. In this study, a newapproach to set the Inspection Starting Point (ISP), StructuralModification Point (SMP) and the corresponding inspection intervals ispresented and validated with respect to experimental results found in theliterature. This approach allows more flexibility in choosing ISP, SMP andinspection intervals, as long as the desired overall probability of failure ismaintained. This is achieved by means of an iterative risk analysisprocedure. The paper studies the capabilities of the new approach throughWFD analysis applied on an example of a lap-joint structural element thathas been experimentally studied in the literature. The study presents anew approach of using Cumulative Probabilities Of Failure (CPOF) as aquantitative measure to enable optimization of the maintenance program.