| Résumé | This paper presents the results of IAR/NRC research on developing risk assessment methodologies and tools for aircraft structures containing multiple site fatigue damage (MSD) / multiple element damage (MED) to support the structural life cycle management for Canadian Forces air fleet. The lower surface panel of the CC-130 centre wing structure was used as a case study to demonstrate the methodologies and tools developed by NRC. At first, a crack growth analysis program was developed to simultaneously grow the MSD cracks, considering the effects of crack interaction and adjacent structure failure (MED). A beta correction library for MSD/MED cracks was developed and verified with p-version finite element (FE) analysis (StressCheck) and other closed-form solutions. The residual strength of the MSD/MED structures was analyzed using a global-local FE modelling technique, which was developed to quantify the load redistribution among the cracked panel and adjacent components. For the quantitative risk analysis, an efficient Monte Carlo Simulation technique was developed and used in NRC's crack growth program. The Monte Carlo simulated crack size distribution was then used in NRC's in-house risk analysis code, ProDTA, to calculate the probability of failure (PoF) for the MSD/MED structures. The results of the case study showed that the presence of MSD/MED significantly increases the PoF. Therefore, the maintenance actions should be adjusted according to the MSD/MED risk analysis, crack growth, and residual strength analysis results. |
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