Effect of contact path on the mixed lubrication performance, friction and contact fatigue in spiral bevel gears

The contact path in spiral bevel gears may have significant effect on the lubrication breakdown and surface failure. However, available study mainly focus on the influence of contact path on the contact stress distribution with the assumptions of dry contact and smooth surface. In reality, these gears are lubricated and the surfaces are quite rough with three-dimensional (3D) topography. The present study aims to systematically investigate the effect of contact path on the mixed lubrication characteristics, friction and contact fatigue in spiral bevel gears with the consideration of surface roughness. A comprehensive analysis for gearing geometry, kinematics, and contact load with different contact path affected by assembling parameters is executed based on the loaded tooth contact analysis (LTCA). The corresponding lubrication characteristics, friction coefficient and flash temperature, as well as the fatigue life are conducted in a wide range of operating condition based on a recently developed mixed EHL model for spiral bevel gears. Obtained results reveal that the contact path is vital to lubrication performance, efficiency improvements and fatigue prevention. In particular, the contact path nearby toe of gear flank appears to be a weak path due to the smaller film thickness, larger friction coefficient, higher flash temperature and lower relative fatigue life.