Theoretical Study And Numerical Simulation Of Mixed Lubrication In Point Contact

In engineering practice,the mixed lubrication occurs in a lot of mechanical friction pairs,it is a lubrication region where hydrodynamic actions and asperity contacts co-exist.Under the condition of low speed or high loads,the lubricant film can be extremely thin with the same order of magnitude as that of surface roughness,or even thinner.It always results into a direct contact for the interactive surfaces,and the applied load is then shared by both hydrodynamic lubricant film and contacted asperities.This paper is devoted to numerically simulating the mixed lubrication,then analyzing the effects of lubricating oil,contact materials and surface topography characteristics on the performance of mixed lubrication.The primary coverage includes:(1)The numerical model of mixed lubrication in point contact is developed based on a unified Reynolds equation,and explained the numerical algorithm used in solving this model,such as the semi-system method to ensure the numerical stability;a discrete convolution and fast Fourier transform(DC-FFT)method to speed up the calculate surface deformation.the progressive mesh densification(PMD)method to accelerate the iterative convergence speed.(2)A non-Newtonian fluid mixed lubrication model is established in order to consider the non-Newtonian properties,a friction coefficient model is built based on the appropriate rheological model.Then analyze the effects of lubricating oil ambience viscosity and reference shear stress on the performance of mixed lubrication.(3)The mixed lubrication involves contact materials for direct contact,so select four kinds of different materials are selected as the research objects in this paper,and the influence of elastic mechanical properties of the material on mixed lubrication is analyzed.(4)Surface topography has important effects on the mixed lubrication,a computer simulation method is developed to generate the Gaussian and non-Gaussian random surfaces in this paper,then analyze the effects of surface topography parameters(RMS,auto-correlation lengths,skewness,kurtosis)on the performance of mixed lubrication.