On The Traction Of Lubrication Film In Point Contacts

Mechanical elements play a role in power transmission,the traction in the non-conformal contacts is caused by the shear of highly pressurized thin lubrication films.In the view of the power loss suppression,advanced surface design and lubricant development are required.The application effects of the surface and lubricant are evaluated through traction measurement and analysis.In this thesis,experimental and theoretical studies on the film traction were conducted to explore the relations between the traction behaviour and the parameters.The main work can be summarized as:(1)Design and manufacture of tribometers for film traction measurement.Two types of film traction tribometers were developed respectively to measure the simple sliding Stribeck curve,and the lubricant film rheology under different sliding rolling ratio(SRR)conditions.The later type tribometers are able to measure the film thickness and traction simultaneously.(2)Experimental studies on Stribeck curves under simple sliding conditions.Using the simple sliding tribometer,the influences of velocity,viscosity,load,surface roughness and lubrication process on the Stribeck curve were analyzed,based on which different lubrication regimes were recognized.(3)Experimental studies on lubricant film rheology with SRR.Using the later type tribometer,the friction and lubricating film thickness were measured simultaneously.The friction and film thickness curves with SRR were obtained.The effects of SRR,load,viscosity,entrainment speed and roughness on the traction curve were analyzed.The rheology behaviours of lubricants were evaluated according to the experimental results.(4)Numerical simulations of traction under simple sliding conditions.A numerical model was build considering the thermal and non-newtonian effects,and the complete numerical solutions with high precision were obtained.The influences of thermal effect,non-newtonian effect and size effect on the simple sliding thermal elastohydrodynamic lubrication are analyzed.Comparisons between numerical predictions and experimental measurements were conducted.The good agreements indicated the feasibility of the tribometers and validity of the numerical model.