Optimum design of the tooth root profile for improving bending capacity

Gear transmission is a major form of power transmission, of which the reliability greatly affects the life of many mechanical devices. Gears have two main failure modes, namely tooth surface pitting and tooth root fracture. Tooth surface pitting is mainly due to excessive contact stress and tooth root fracture is mainly due to excessive bending stress. In this paper, we focus on increasing the tooth root strength of spur gears by optimizing the hob tip contour. A hobbing simulation model is developed to generate the tooth root profile from its corresponding hob tip contour. The hob tip contour is defined by introducing a Bezier curve of five points. An optimization process based on genetic algorithm and FEM analysis is designed to find the optimal tooth root profile with larger bending load capacity. The optimal tooth root profile and its corresponding hob tip contour can be obtained for engineering application. This work provides a theoretical basis for spur gear design with a high bending load capacity.