Derivation of a Fatigue Life Model for Gears

Abstract : A load-life model is developed for calculating the fatigue life and reliability of a spur gear mesh. The dynamic capacity of a gear mesh is defined as the tangential load which can be transmitted for one million pinion revolutions with a 90% probability of survival. The model is an extension of the currently accepted Lundberg-Palmgren Rolling Element Bearing Life Model. Limited rolling contact testing of cylindrical samples with and without traction in the contact was accomplished. At a low coefficient of traction (below 0.1), no statistically significant effect on fatigue life was noted. Scanning electron microscopy studies were performed of all test samples. One rolling test sample was SEM examined periodically during testing to observe initiation and progression of failure. Numerical examples are presented for the calculation of the dynamic capacity of a standard contact ratio and a high contact ratio spur gear mesh.