Fatigue crack propagation analysis considering the dynamic crack-load coupling effect

Gear fillet crack is one of the most common defects of the gear transmission system, and the study of gear fillet crack propagation and life prediction has attracted much attention in the literature. The existence of the crack will alter the dynamic load applied on the cracked tooth via the localized reduction of time-varying gear mesh stiffness, which in turn affects the crack propagation speed and direction. Previous work mostly neglects this dynamic "crack-load" interaction that may lead to an unreliable simulation of the fatigue crack propagation path. In this paper, an integrated finite element method-dynamic model of a cracked gear pair is established to simulate the crack propagation path considering the coupling effect between the fillet crack excitation and the dynamic load. The dynamic model of a cracked gear pair is first built to obtain the dynamic load in the current state, and the rainflow counting method is utilized to obtain the load spectrum, which is used as the load input of the finite element (FE) model of the cracked gear to realize the simulation of the crack propagation increment and angle in the next state. The simulation cycle continues until the full propagation path is modeled. The proposed gear fillet crack modeling method can provide a more reliable simulation of the crack propagation, which is beneficiary to the fatigue life prediction of a cracked gear system.