STUDY ON GEAR BENDING FATIGUE-STRENGTH DESIGN BASED ON RELIABILITY ENGINEERING (PREDICTION OF CRACK-PROPAGATION AND FATIGUE LIFE OF MAC14 SUPERCARBURIZED STEEL GEAR)

Carburized steel gears are increasingly used because of their high-strength. However, high-strength materials usually exhibit large scatter of fatigue life and fatigue strength. The fatigue failure life of a gear mainly consists of two stages: crack initiation life and crack propagation life. In this study, a model to predict crack propagation and fatigue life of a carburized steel gear was developed based on crack initiation on carbide precipitation and crack propagation life at tooth case by using the Monte Carlo simulation method. The model was applied to simulate crack propagation and fatigue life of MAC14 supercarburized steel gear. The result obtained shows that the fatigue life distribution of MAC14 supercarburized steel gear obtained from simulation and experiment is well represented by a three-parameter Weibull distribution. The crack propagation life calculation combined with the Monte Carlo simulation method was in good agreement with experimental results. The model can be implemented as an alternative procedure on the ordinary method to predict crack propagation and bending fatigue failure life of a carburized steel gear for practical design application.