Fatigue crack initiation and propagation in a PM-gear tooth root

A computational model for the determination of the fatigue life of sintered gears is presented in this study. The total fatigue life of sintered gear, N, is divided into the crack initiation life, Ni, and crack propagation life, Np. The number of cycles for crack initiation in a gear tooth root, Ni, is determined by using the strain-life approach and the low-cycle fatigue parameters of the sintered gear material available in the literature. The number of cycles for crack propagation, Np, to a critical length is obtained by using the simple Paris law and the material parameters taken from the authors' previous work. The comprehensive computational analyses in the framework of the Ansys-software were performed to obtain the strain-stress field in a gear tooth root, and to determine the stress intensity factor at the crack tip. The numerical results were compared with the experimental data available in the literature.