On The Thin Film Lubrication Of Soft Contacts And Artificial Synovial Fluids

This thesis focuses on the lubrication film measurement in soft materials contacts and lubrication properties of an artifical joint synovial fluid was studied. Completed work includes:1) A test system for lubrication film thickness in conformal contacts has been extended to the measurement of soft materials contact by development of some specific experiment techniques. Using ion sputtering of Au, the reflectivity of the PMMA surface can be significantly improved and used for optical interferometry. The inclination was proposed to be set under zero loading as a base for the film thickness measurement of soft contact. Some error analyses was given based on the interference fringes swing occurring frequently in the measurement, and it is suggested that the dead postion be used as the test point with a minimum errors. By the above techniques developed, the system can accurately get thickness of the lubricant film between a soft PMMA slider and the glass disc under different angles, different speeds and different loads, the operation conditons of the test rig was enlarged.2) The lubrication film thickness was measured for a PMMA plane slider and a PMMA cylindrical slider, respectively. The influences of speeds, inclination angles and loads were investigated. For a PMMA plane slider, the film thickness increases and the surface deformation recovers with increasing speeds; increase in inclination generates high film thickness, and so the decease in loads. Compared to the steel slider, the PMMA slider can produces high film thickness, which can be attributed to the elastic deformation of soft materials. Cylindrical slider have similar conclusions.3) Using the film thickness measuring system for conformal contacts, the hydrodynamic lubrication behaviours of artificial joint synovial fluids have been studied. Experiments show that adsorption layer can be formed on the surface of the steel slider and is corrosive to the slider. More interesting finding is that adsorption film formation and hence corrosion show considerable positional selectivity in position, that is mostly at the inlet side. In the meaning time, it was also found that the interference fringes changes with time, and some explainations were presented.4) Numerical analyses have been carried out for the PMMA cylincrical slider lubrication, and the influences of speeds and loads on the film thickness and pressure distributions were given. The numerical results were compared with experiments, and the difference between them was analyzed.