Fatigue Life Evaluation of Linear Structures with Uncertain-But-Bounded Parameters Under Stochastic Excitations

This study presents two hybrid methods, the full combination method and the simplified expression, for evaluating the fatigue life of linear structures with uncertain-but-bounded parameters subjected to stochastic excitations. First, approximate expressions of the spectral moments and spectral bandwidth parameters are derived based on the improved interval analysis via extra unitary interval and the interval Taylor expansion. Then, the lower and upper bounds of the interval expected fatigue damage rate and fatigue life are evaluated by fully or properly combining the two bounds of the spectral moments and spectral bandwidth parameters by the Tovo–Benasciutti method. Through the numerical study, the full combination method is recommended for the accurate assessment of the interval fatigue life, and the simplified expression is recommended for rapid evaluation of the two bounds of the interval fatigue life using the explicit expression. Finally, three numerical examples are adopted to illustrate the accuracy and efficiency of the proposed methods via comparison of the present results with the exact ones.