Abstract:

A reliability analysis methodology based on the probability fracture mechanics is developed for the wing with main and subordinate components under conisdering several factors, such as crack detection probability, inspection interval, initial flaw distribution, crack growth,residual strength,etc.. The initial fatigue quality(IFQ)of a structural components is represented by an equivalent initial flaw size (EIFS). It is assumed that the equivalent initial crack growth curve conincides with the actual crack growth curve in the crack length region larger than 0.5mm. In this paper, the following crack size-time realtionship is used: a(t) =a(0)exp(at) in which the EIFS a(0) is a lognormal random variable. The correlation between the main and subordinate components in fatigue properties is considered. Several equations to compute the failure rate and the failure probability of structures in any service interval are derived. A calculation example for the wings of some fighter is given in this paper. The results show that the fatigue life of the subordinate component has much effect on the probability of failure of the main component.

Key words: initial flaw, residual stength, fatigue life, reliability