随机超载下疲劳裂纹扩展寿命的计算

针对在基本循环载荷上加入随机超载序列的疲劳裂纹扩展问题，应用裂纹闭合的概念考虑超载的迟滞效应，将延迟时间描述成纯离散型马尔可夫过程。对相应的柯尔莫哥洛夫－费勒微积分方程进行了分步求解，结合疲劳断裂分别出现在基本循环峰载作用时和超载作用时两种情况，计算出不同可靠度下裂纹的扩展寿命，并研究了超载大小和发生强度对扩展寿命的影响。

Estimation of Fatigue Crack Lifetime under Random Overloads

A stochastic model describing fatigue crack growth under random overload sequences, superimposed on a base line cyclic load, is presented. The crack closure concept is applied to account for the retardation effect associated with the overload peaks. The model consists in presentation of the delay time as a purely discontinuous Markov process. A numerical procedure based on the Kolmogorov Feller integro differential equation is developed. Incorporating the situations of fracture occurrence either under an overload or under the base line load, the fatigue crack lifetime is acquired with specific reliability requirement.