脂润滑点接触副混合润滑模型研究

The Study on Grease Mixed-Lubrication Model of Point Contact Pair

考虑润滑脂非牛顿特性和粗糙表面微凸体接触几何,基于润滑脂Herschel-Bulkey流变模型和微凸体K-E弹塑性接触模型,确定了润滑介质弹流作用和微凸体接触作用的并行处理方案,并提出了一种流体动压区和微凸体接触区的压力边界条件假设,建立了脂润滑点接触副混合润滑的确定性模型。结合处理边界条件的虚压力替代法,构建了混合润滑模型的直接迭代法,研究了不同润滑脂和粗糙表面形貌特征下的点接触副混合润滑特征。结果表明,受表面粗糙形貌影响,二次压力峰和颈缩特征不再明显,脂膜压力分布出现多个压力峰值,且峰值随速度的减小和粗糙度的增大而增大。脂膜厚度与润滑脂稠度等级之间不存在单调关系。当膜厚比约小于4时摩擦副进入混合润滑状态。粗糙表面的偏态对混合润滑存在一定的影响。

Considering the non-Newtonian characteristics of the grease and the asperity geometry of the rough surface, and based on the Herschel-Bulkey rheological model and the K-E elastoplastic contact model, the parallel processing of the hydrodynamic action of the lubricant and the asperity contact was determined. Combined with the proposed assumption of the boundary condition between the elastodynamic contact zone and the asperity contact zone, a deterministic model of grease mixed-lubrication of the point contact is established. The iterative method of the mixed-lubrication model is constructed by combining the virtual pressure substitution method used to deal with the boundary condition, and then lubrication characteristics under different greases and rough surfaces are studied.The results show that the secondary pressure peak and the necking feature are no longer obvious due to the surface roughness, and multiple pressure peaks appear in the lubrication area, and the pressure peak increases with decreasing speed and increasing roughness.There is no monotonic relationship between the film thickness and the grease consistency grade. When the film thickness ratio is less than about 4, the contact enters the mixed-lubrication state. The skewness of the rough surface has a certain effect on the mixed-lubrication.