Transient behaviors of friction, temperature and fatigue in different contact trajectories for spiral bevel gears

Abstract

Abstract The dramatic changes in contact geometry, load, entraining and sliding velocity vectors along contact trajectories of spiral bevel gears may cause significant squeezing action. It suggests that the steady-state analysis at each discrete engaging point cannot effectively describe the tribological behavior in spiral bevel gears. The present study aims to systematically study the transient friction, temperature and contact fatigue behaviors in different contact trajectories for spiral bevel gears based on a newly developed transient mixed EHL model. It shows that the obtained transient friction coefficient is much higher than the steady-state when the gears mesh in the first half of the engagement period. During the entire engagement period, the predicted transient fatigue life is significantly longer than the predicted steady-state fatigue life, which is of importance to the integrated and economical design of spiral bevel gears. The comparison with single half-sine waveform asperity demonstrated that the transient asperity contact pressure is much lower than that in quasi-steady state. The variation of flash temperature appears to be insignificant. Moreover, in different contact trajectories, the weakest point in one engagement period always occurs at a certain point when one teeth pair just finished the engaging-in and another pair of teeth completed engaging-out, and the toe contact exhibits the maximum frictional energy consumption and shortest fatigue life among them.