Abstract: Due to the random factors such as material properties, geometrical characteristic of structural member, load history and environmental condition, the fatigue life of structure often deviates from the design life. To reduce the scatter of fatigue life, a robust optimization model of structural fatigue life is presented. The model combines structural optimization theory and stochastic finite element method. Under the condition of considering the effects of variance of design variables and other random variables on the structural fatigue life, the problem is formulated as a multi-criteria optimization problem, in which both the mean structural fatigue life and the standard deviation of structural fatigue life are to be minimized. The relationship between the mean structural fatigue life and the standard deviation of structural fatigue life can be balanced by a weight factor. The structural fatigue life is limited between the low fatigue life and high fatigue life in the constrain functions. Fatigue life of the structure optimized by the proposed method has a relative small fluctuation at the mean value and keeps far away from the ultimate fatigue life. A numerical example is performed for a planar 10-bar truss. The result shows that the proposed method is feasible and applicable.

Key words: Fatigue life, Randomness, Robust design, Stochastic finite element method, Structural optimization