Research On Widespread Fatigue Damage Detectable Crack Based On Reliability Statistic Theory

In recent years, with the rapid development of domestic civil aviation, the number of aging aircraft in-Service is continually increasing. A lot of problems have been brought by the aging trend of fleet size, such as fatigue crack, corrosion, aging system and equipment and so on. Among them, the widespread fatigue damage(WFD) caused by fatigue and corrosion seriously affects the structural integrity of aging aircraft. There are also many potential safety hazards and incidents of aging aircraft related to widespread fatigue damage at home and abroad. How to evaluate the safety of structure that is sensitive to widespread fatigue more effectively, and to ensure the continued airworthiness and operation safety of aging aircraft, is an important topic of aging aircraft safety management, and also a vital problem to be solved.Based on research status of WFD theory both in China and overseas, which is integrated with damage or maintenance data and engineering experience of domestic aging aircraft,quantitative evaluation on crack inspection probability of typical structure that contains multiple cracks is conducted. Firstly, a reliability model of multiple site damage(MSD) crack initiation on the basis of “voting system” is provided, the probability equation of MSD crack initiation is inferred, and the accuracy of model is verified by an example. Then, an improved Weibull distribution model is proposed on the basic of existing crack inspection probability model, and its applicability is proved through theoretical deduction and experimental analysis.Then, a detectable crack probability model of MSD combined with the reliability model of MSD crack initiation and crack inspection probability model is raised. And numerical analysis is carried out through Monte Carlo method, to simulate the variation trend of MSD crack inspection caused by the number of structural details. Finally, based on object-oriented programming and the research results of this paper, an analysis software used for widespread fatigue damage detectable crack is developed for engineering application.The preliminary safety evaluation of structure that is sensitive to widespread fatigue can be achieved by the analysis of the MSD detectable cracks, and also has laid the foundation for the engineering application.