This paper presents an improved damage model based on the construction technology of nonlinear partition virtual load spectrum by golden section method which is closer to the actual condition. In contrast to the Palmgren–Miner classical model, the result of fatigue life is more accurate. The improved damage model uses reliability instead of cumulative fatigue damage as the fatigue failure criterion. The objectives in this paper include verifying the convergence of the improved model and analyzing the influence of key parameters on fatigue life. The correction coefficient of the key parameters outperforms the traditional model which ignores the effect of stress sequence on fatigue. The fatigue life of several typical models and improved model is calculated and compared with the experimental results. It is shown that the improved model has higher accuracy and safety.
Aiming at the accuracy and efficiency of traditional reliability method for solving highly nonlinear problem, this paper proposes the regional equivalent conversion index (RECI) to compute reliability under arbitrary boundary and number of subdomains of limit state function. Firstly, we establish the model of RECI and the corresponding sampling method. Furthermore, the RECI of a series of parallel linear performance functions are computed by the proposed method. Besides the advanced first order and second moment method (AFOSM) are used to compute the reliability. Finally, the mapping relationship between RECI and reliability is established. Influence of sampling parameters on relative error is studied and optimal value is given. The parameters are optimized by analyzing the influence of the parameters on the precision. This method is also suitable for multiple failure modes without changing any process. Numerical examples are employed to demonstrate the feasibility of the proposed method for solving highly nonlinear problem in dimension 1–4.
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