The effect of gear module on bending fatigue failure location in carburized and shot-peened spur gears

Shot-peening is an emerging method used to improve the bending fatigue resistance of carburized gears. However, even though this method improves the bending fatigue resistance at the surface, bending fatigue crack initiation often shifts below the surface, making it harder to detect during regular service intervals. In this paper, an experimentally validated computational model based on the finite element analysis and the multilayer method is used to investigate the effect of gear geometry, specifically its module, on the probability of subsurface bending fatigue failure. The main goal is to reduce the chance of subsurface bending fatigue failure while retaining the beneficial effects of shot-peening. Four optimal gear modules are chosen for the investigation with respect to bending fatigue while maintaining constant fatigue properties and residual stress profiles. The results demonstrate that choosing a lower module decreases the probability of subsurface bending fatigue crack initiation in carburized and shot-peened gears. Lastly, it is also suggested that optimizing carburization parameters may enhance the beneficial compressive residual stresses below the surface, lowering the probability of subsurface bending fatigue crack initiation.