Fatigue Analysis for Axle Differential Cases 2006-01-0779

The recent trends of increasing driveline torque and use of traction control devices call for increasingly higher durability capacity from driveline components. Bench and vehicle durability tests are often used to validate designs, but they are not cost-effective and take months to complete. Traditional finite element analysis (FEA) procedures have been used effectively in the re-design of driveline components to reduce stress, and occasionally, to predict fatigue life. But in the case of certain rotating components, such as the Axle Differential Case, where the component sees large stress/strain fluctuations within the course of one complete rotation, even under constant input torque, historical fatigue analysis (when conducted) yields very conservative results. The axle differential case tends to be one of the weakest links in the rear axle assembly. Therefore, there is a crucial need for analytical methods to more accurately predict fatigue life to reduce testing time and cost. In this paper, a new CAE procedure for differential case fatigue life prediction is outlined. This analysis procedure takes into account the variation of stress within each revolution for a given input torque, as well as the variation in the input torque itself. The analytical result has been shown to correlate very closely with bench testing using a torsional Axle Inertia Impact Test.