Fatigue reliability predictions in vibrating structures under uncertainty

Abstract

This work addresses the problem of predicting the reliability due to fatigue of MDOF structures subjected to uncertain random loading. Uncertainties in loading characteristics as well as in structural and degradation models are taken into consideration. Degradation due to crack growth is considered based on Paris equation. The prediction of stress range which is involved in Paris equation is rationally approximated by statistical measures of the stress response such as second moments and probability density functions of the stress range of the response. The proposed fatigue prediction method is used in optimal design of structures formulated in a multi-objective context that allows the simultaneous minimization of the objectives related to the weight of the structure and the lifetime due to stochastic fatigue of the structure. The features of the proposed methodologies are illustrated using a multi-degree-of-freedom hierarchical system involving multidimensional degradation states and subjected to stationary random excitation.