急停问题的椭圆接触弹流润滑分析

将机械急停时滚动轴承、齿轮等的弹流润滑油膜的渐变过程简化为从稳恒状态突然转化为恒载荷纯挤压状态,然后随时间的推移挤压效应逐渐消失的过程,建立了椭圆接触瞬态弹流润滑模型。假设润滑油为牛顿流体,在等温条件下用多重网格技术进行了动态数值求解,讨论了急停前卷吸速度分别沿椭圆接触区的长轴和短轴方向时,不同参数条件下的残留弹流润滑膜的压力和膜厚随时间的变化规律。数值计算结果表明,急停后润滑油会逐渐被挤出接触区,因此残留油膜只能保持很短的时间;较高的Hertz接触压力会通过增加润滑油粘度而延长残余油膜的维持时间,但不能根本上改变上述变化趋势,卷吸速度的方向也不能改变上述变化趋势。

Analysis on the Elastohydrodynamic Lubrication in Elliptical Contacts for a Sudden Stop Process

The sudden stop process of the elastohydrodynamic lubrication (EHL) of machine elements such as rolling bearings and meshing gears was simplified into a constant-loaded purely squeezing process which was suddenly transferred from a steady EHL state and during this process the EHL film was vanished gradually due to squeezing action.A mathematical model was established to describe the transient process based on Newtonian lubricant and isothermal assumptions.Transient numerical solution was obtained by solving the model with multi-grid techniques.Cases for the entrainment speed before the stop along the major or the minor axis of the contact ellipse were solved with different operating parameters, and the variations in the pressure and film thickness versus time were discussed.The numerical results show that, after a sudden stop,the lubricant in the remained film will gradually be squeezed out from the conjunction,and the residual film can maintain itself in only a very short period.A higher Hertzian contact pressure can prolong the life of residual film through the increase in the lubricant viscosity, but the general changing rule of residual film cannot be changed fundamentally by adding Hertzian contact pressure,or by changing the direction of entrainment speed.