Statistical scaling of durability life for independent multi-detail structures

To assess the fatigue life for aircraft structure, the specimen used for the durability test is often designed as multi-details(MD) to simulate the structural configuration and load transfer. Once one detail fails, the fatigue testing is ended, and the fatigue life of single detail(SD) must be deduced statistically based on the incomplete life of MD specimen. Based on the series failure model of the same multi-detail structures, the statistical scaling approach was proposed to determine the life distribution of the single detail. Assuming the fatigue life of MD follows the log-normal distribution, Monte Carlo sampling and stimulating results show that the fatigue life of single detail follows the same distribution approximately; the expressions between the distribution parameters of MD and SD are deduced. The expectation and variation of MD are higher than those of SD. Assuming the fatigue life of MD follows the two-parameter Weibull distribution, the SD's fatigue life follows the same distribution whose slope is unchanged, but location parameter is larger than that of MD. Finally, an example for analyzing MD fatigue test result from American durability test program is given.