A numerical model for total contact fatigue life prediction of carburized spur gears considering the surface integrity

Surface integrity has a significant influence on the tooth contact fatigue performance of carburized gears. This paper proposed a total contact fatigue life prediction model considering the hardness gradients, residual stress, and surface roughness. The contact pressure distributions are determined using the elastohydrodynamic lubrication numerical model. The crack initiation life and location are forecasted by the modified Brown-Miller fatigue criterion, considering the surface integrity, loading conditions, and lubrication state. The tooth surface of the spur gear is divided into layers through the thin slicing technique, and the fatigue performance parameters for each layer are determined using the multilayer approach. The crack propagation path and lifespan are predicted by the extended finite element method based on linear elastic fracture mechanics. Contact fatigue life testing is employed to verify the effectiveness of the proposed method for predicting total fatigue life. The damaged areas measured by image analysis are used to monitor crack initiation and determine fatigue failure. Fracture surface analysis conducted with SEM identifies the path of crack propagation. The predicted total contact fatigue life, crack initiation location, and crack extension path agree well with the experimental findings.