点接触润滑粗糙表面滑动摩擦力的预测研究

Prediction of Sliding Friction Force of Rough Surfaces in Lubricated Point Contacts

在整个润滑区域内基于统一Reynolds方程的混合润滑模型,根据流变模型计算流体摩擦力,根据边界膜极限剪应力模型计算微突体接触摩擦力,二者相加得到混合润滑摩擦力.分析了粗糙度幅值和纹理对摩擦系数的影响以及非牛顿流变模型对流体摩擦系数的影响.模拟跨越整个润滑区,即弹流润滑、混合润滑和边界润滑,得到完整的Stribeck曲线.结果表明,表面越粗糙,混合润滑的摩擦系数越大,弹流润滑和边界润滑时粗糙度幅值影响很小.交叉斜纹的润滑效果优于横向纹理.不同极限剪应力流变模型计算的摩擦系数相差不大.

A mixed lubrication model, based on an unified Reynolds equation in all lubrication regimes including elastohydrodynamic, mixed and boundary lubrication, for prediction of the sliding friction between rough surfaces in point contacts, was developed. In the calculation, the fluid traction in the lubrication region was determined in terms of rheology model for the lubricant, while the friction from asperity contact was calculated by limiting shear stress model of boundary film. Thus the total friction was obtained by summing up the two components. Then, the effects of roughn ess amplitude and texture on friction coefficient were investigated. The magnitude of fluid friction coefficient from the different non-Newtonian fluid models with limiting shear show that a rougher surface would give rise to higher friction coefficient in stress was also compared. The results mixed lubrication regime, and higher critical speed of transition from full-film elastohydrodynamic to mixed lubrication. But roughness amplitude has less effect in hydrodynamic and boundary lubrication. Cross texture is more beneficial to lubrication than the transverse if the operating conditions are the same. Different rheology models with limiting shear strength have little effect on prediction of fluid traction under the same operating conditions.