Abstract: The uncertainty of the initial strength was described by a random variable， and the evolution process of the strength degradation was regarded as the Gamma process. Then the perturbation method， the fourth moment and Edgeworth series method were used to solve the problem of reliability calculation with random parameters of arbitrary distributions. Matrix differentialbased formulas for calculating the reliability sensitivity with respect to the mean and the variance of the random variables was derived based on the matrix differential method. The reliability analysis of the bolts was taken as an example to verify the proposed method. The results showed that the method can effectively solve the problem of the reliability sensitivity of mechanical parts with strength degradation.

Key words: reliability sensitivity, Gamma random process, strength degradation, the fourth moment method, Edgeworth series