Fatigue failure prediction method and constant amplitude equivalence strategy of adhesive interface under variable amplitude loading

Abstract

The existing commercial software can only predict the fatigue life of homogeneous materials/structures under constant amplitude loading. This work developed a software tool that could predict the fatigue life of the adhesive interface under variable amplitude loading by embedding a modified fatigue cohesive zone model and amplitude variation function. Central to this innovation is the load sequence effect factor (γ), designed to consider nuanced influences like the shock effect of stepped amplitude changes on the fatigue properties. The effects of the block loading sequence on the fatigue life and crack growth rate of the adhesive interface were investigated numerically, and the influence of stepped amplitude on the evolution of a damage zone ahead of the main crack front was observed. It was found that the loading sequence from Low to High (L-H) accelerated the crack growth rate and reduced the fatigue life, and vice versa. Under the same fatigue life, a constant amplitude fatigue equivalence (CAFE) strategy is proposed, which could convert a variable amplitude road spectrum into a constant amplitude load more suitable for the testing bench. The proposed tool and method are also suitable for bi-material interface failure prediction under variable amplitude fatigue loading.