Fleet economic life prediction: A probabilistic approach including load spectrum variation and structural property variation

A probabilistic approach for predicting the economic life of an aircraft fleet is proposed with variation in load spectrum and structural property taken into account. Specimens of TA15M titanium alloy were fatigue tested under three individual load spectra of different damage severities. By using the fatigue test results, a generic equivalent-initial-flaw-size distribution was obtained, and a stochastic crack growth model was developed including the load spectrum variation and the material crack resistant variation. With the number of cracks exceeding the economic repair limit as the economic life criteria, a simple expression was derived for the probability of crack exceedance.