斜齿轮弹流润滑下的接触疲劳寿命计算

经典齿轮接触疲劳强度理论是基于光滑表面赫兹干接触理论,而实际齿面具有粗糙度,且啮合轮齿多数处于混合润滑状态.本文基于齿轮润滑接触分析建立了渐开线斜齿轮的接触疲劳寿命计算模型.模型由齿轮润滑接触分析模型和基于次表面应力分布的疲劳寿命模型组成.首先将斜齿圆柱齿轮一对齿的瞬时啮合等效为两反向圆锥的接触问题,建立了齿轮的有限长弹流润滑计算模型,考虑了齿轮啮合周期内瞬时载荷、接触线长、卷吸速度等因素的影响,基于统一雷诺方程方法求得啮合齿对间的润滑压力和油膜厚度分布;在此基础上,计算轮齿接触区次表面的米歇斯应力分布,根据Zaretsky接触疲劳寿命计算模型,对齿轮组的接触疲劳寿命进行模拟预测.针对不同工况参数下接触疲劳寿命计算表明:润滑油黏度、轮齿表面粗糙度等因素对齿面接触疲劳寿命均有显著的影响.

A contact Fatigue Model of Helical Gear under Elastohydrodynamic Lubrication

The classical theory of gear contact fatigue strength is based on the Hertz contact theory with the assumptions that teeth surfaces are ideally smooth without lubrication. However, the gear pairs often operated in mixed lubrication and the teeth surfaces were rough actually. This paper aims to establish a contact fatigue model for involute helical gear, which was based on the analysis of the gear contact under mixed lubrication. The model consisted of two submodels. Firstly, finite line contact elastohydrodynamic lubrication (EHL) model of the involute helical gears was developed by assuming each meshing instant as the contact between two tapered rollers in opposite orientation. The influences of the load distribution along the line of action, the length of the line of contact and the entrainment velocity on the lubrication were taken into account. The pressure distribution and the oil film thickness in the entire computational domain were obtained based on a unified Reynolds equation system approach. Secondly, the subsurface von Mises stress field was calculated with the pressure distribution from the mixed-EHL analysis, and then the contact fatigue life of the gear pairs was predicted by using the fatigue life model developed by Zaretsky. Finally, the developed model was applied to study the effect of gear surface roughness and lubricant viscosity on gear fatigue life. The results show that both of them had a significant influence on the contact fatigue life of gear.