A stress-based model for general rolling contacts with surface and subsurface survival: Application to gears

Abstract

The paper describes a model for life prediction of general rolling/sliding contacts in machine elements considering surface and subsurface survival. This is a stress-based model which requires as input the contact stress distribution in time during the contact cycle. For the surface, the lubrication quality is required. The model is general enough to be applied to any heavily loaded lubricated contact but its application here is illustrated for the specific case of spur gears. In current design practices, life calculations for gear contacts require to satisfy a fatigue limit stress, which is further reduced using service penalty factors. In the proposed model the concept of L10 life associated to a 90% reliability for the gear population is applied. Comparison between published experimentally obtained gear endurances and L10 predicted life (using the present theory) indicates the ability of the model to account for the gear endurance and the contribution of the surface to the performance. This new approach is felt to be of advantage for future progress in gear design. Equally applicable in the case of rolling bearings and cam-follower systems.