Crack Initiation, Propagation and Fatigue Life Prediction of Spur Gear Under a Moving Contact Load

ABSTRACT This study investigates the failure mechanisms of spur gears under bending fatigue loading, focusing on crack initiation, propagation paths, and stress field distribution. Finite element simulations are conducted to obtain linear elastic stress–strain data at the tooth root, which are then incorporated into the Smith‐Watson‐Topper (SWT) multi‐axial fatigue model to predict the crack initiation location. Subsequently, a moving contact load model with time‐dependent magnitude and direction is developed through the secondary implementation of an Abaqus DLOAD user subroutine using Fortran programming. During crack propagation analysis, variations in stress intensity factors (SIF), crack propagation paths, and stress field distribution are examined, whereas the NASGRO model is applied to estimate fatigue life under different operating conditions. The results indicate that the predicted fatigue life under moving contact load closely matches experimental values. During crack propagation, merging cracks lead to interactions and overlapping of stress fields, which ultimately reach a new equilibrium after merging. Furthermore, compared to loading at the highest position of single‐tooth contact (HPSTC), the dynamic effect of the moving contact load effectively alleviates stress concentration and reduces the crack propagation rate.