Reliability Modeling for Fatigue Life of Cutterhead of Tunnel Boring Machine

Traditional stress-strength interference model is suitable for reliability calculation of time-independent failure modes, but applying such interference analysis concept directly to time-dependent failure modes such as fatigue, wear, and corrosion still faces many challenges, even for structural fatigue reliability under constant amplitude loading with uncertainty in stress amplitude. In order to consider the impact of material performance uncertainty and loading uncertainty on the fatigue reliability of structural critical locations, the traditional stress-strength interference model is reinterpreted as a statistical average representing the probability that the strength is greater than the stress, and vice versa. Thus, the traditional similar-interference idea between stress and strength can be extended to the situation where two dissimilar dimensional random variables (such as stress and fatigue life) interfere. By adopting the stress-life dissimilar-dimension interference model, the fatigue reliability analysis of a complex structural system subjected to random loading can be achieved, as long as the life distribution can be expressed as a function of stress. This model fully takes into account the stress state of cutterhead structure of tunnel boring machine (TBM) under different working conditions and the statistical correlation between the fatigue lives of individual elements.