Analysis of Contact and Bending Fatigue for Double-Helical Planetary Gear Train Based on Efficient Critical Plane Methods

Contact and bending fatigue are the main failure modes in gears. In this study, we propose a finite element model to investigate the fatigue behavior of a double-helical planetary gearbox based on the critical plane methods with a search algorithm to improve calculation efficiency. The finite element mesh is generated along the direction of the contact line to accurately capture contact stress. The time-varying coefficient of friction between contact surfaces and the residual stress in the hardened layer are considered in the developed model. The effectiveness of the model is demonstrated by comparing the predicted fatigue life with measured data from experiments for a spur gear planetary train. It is concluded that the ability of the planet gear to resist contact fatigue dominates the service duration with fatigue cracks initiating nearly parallel to the surface. The surface hardness gradient is recommended to ensure reliable operation throughout its designed life.