Experimental Study And Numerical Simulation Of Film Thickness To The Mixed Lubrication In Point Contacts

Mixed lubrication is an important research subject of tribology. In recent lubrication manufacture practice, the mixed lubrication occurs in a lot of precision mechanisms under the condition of low speed, high loads and low viscidity lubrication. It is a lubrication region where hydrodynamic actions and asperity contacts co-exist; involving micro-EHL, thin film lubrication and boundary lubrication. However, it is still lack of a comprehensive investigation of mixed lubrication due to the difficulties in experiment and modeling. This paper focuses on the experimental study and numerical simulation of film thickness to the mixed lubrication in point contacts. The main contributions of this dissertation include:The possibility of the errors to the nano-film thickness-measuring instrument according to the principle of relative optical interference intensity has been analyzed. And the relative experiment standard has been investigated. These standards guarantee the reliability of the latter experiments.The influence of the load, oil viscidity, and surface roughness to the film thickness in the mixed lubrication and point contacts has been investigated using the optical nano-film thickness-measuring instrument. The result shows: when the rolling speed is higher, the film thickness is consistent with the film thickness given by the Hamrock-Dowson formulary; when the rolling speed is lower, the film thickness is compositively influenced by the load, oil viscidity, and surface roughness; the load and surface roughness have the influence upon the transition point between the high speed area and the low speed area.The sample cases similar with the experiment condition have been got using the isothermal model of the mixed lubrication in point contacts. This paper gives the qualitative and quantitative analysis between the numerical simulation cases and the experiment results. The qualitative analysis shows that the numerical simulation cases are consistent with the experiment results in the departure to the H&D formulary and the movement of the transition point. The quantitative analysis shows that the numerical simulation cases are different from the experiment results in the place of the transition point,film thickness at low speed area and the zero point.