Lubrication analysis and wear mechanism of heavily loaded herringbone gears with profile modifications in full film and mixed lubrication point contacts.

The transient non-Newtonian thermal micro-elastohydrodynamic lubrication point contact model and the adhesive wear model in mixed lubrication point contact are applied to a heavy-loaded modified herringbone gear drive respectively in steady running phase and start-stop phase. The fundamental parameters of both elastohydrodynamic point contact and wear model are derived from the meshing characteristic and kinematics analysis of herringbone gears. The effects of pinion torque, rotational speed and surface roughness on the maximum pressure and temperature rise and the minimum film thickness are discussed in gear steady running condition for full film lubrication contact. Meantime, the asperity load ratio, contact flash temperature and tooth wear depth are investigated in gear start-stop phase for mixed lubrication point contact. The results show that the lubrication performance of herringbone gear is deteriorated by substantially increased pressure and temperature rise resulting from a larger tooth surface roughness and rotational speed. The tooth wear depth of herringbone gear in start-stop phase is likely greatly reduced with a larger start-stop acceleration. Moreover, the lubrication and wear performances for the complete running cycle of herringbone gear drive from start-up to stop indicate that large tooth surface roughness rather than high load are more prone to herringbone gear thermo-mechanical and wear failures. • A Non-Newtonian thermal transient point contact EHL model is applied to modified herringbone gears. • A mixed EHL point contact wear model is developed for herringbone gears. • Gear thermo-mechanical failure can occur at pitch point due to large tooth roughness. • Tooth wear in start-stop phase can be greatly reduced with large start-stop acceleration. [ABSTRACT FROM AUTHOR]