Experimental Study On Adsorption Characteristics In Lubrication By Protein Aqueous Solution

Every year more than 1 million people receive the hip replacement surgery,which can greatly improve the life quality of those suffering from joint disease.For better performance of artificial joints,work is needed to study their bio-lubrication,where the lubrication mechanism of synovial fluids is a very important subject.The lubrication status of joints in a gait cycle is affected by some mechanical parameters such as loads and speeds.The present thesis focus on the lubrication,adsorption and corrosion of protein aqueous solutions as lubricants under different mechanical conditions.The main work completed includes:1.The existing optical EHL test rig was revised in such a way that a cyclic loading-unloading unit was added to simulate the impact of the joints.The impact period could be precisely controlled by a servo-motor,and the measurement of lubricating films generated has been achieved under different cycles and impact loads.2.Albumin and ?-globulin are the main proteins contained in the synovial fluids.In the present study,bovine serum albumin(BSA)and bovine serum ?-globulin(BGG)were used to simulate those proteins in synovial fluids.Comparison revealed that BGG presents more adsorption than BSA,and thus BGG plays an important role in wear reduction and joint protection.3.In order to investigate the effect of impacts on the protein films adsorbed on solid surfaces,thickness of adsorption films of BSA aqueous solution under dynamic impact and static conditions was measured.The results show that the impact will promote the adsorption of proteins,which can produce effective lubrication films to separate the two bounding surfaces.Under static conditions protein aqueous solution also shows slight adsorption,which is too weak to effectively protect the two surfaces.4.The influence of hydrophilic/hydrophobic property was studied on the protein adsorption with glass discs of different hydrophobicity.It was experimentally found that the adsorption of the protein on the hydrophobic surface was higher than that of the hydrophilic surface due to hydrophobic interaction.At the same time,the adsorption of proteins was also studied with the bearing steel and silicon nitride.It was found that the adsorption of bearing steel was higher than that of silicon nitride.5.With a slider bearing test rig the adsorption characteristics of protein aqueous solution were studied under conformal contact.An electrochemical workstation was used to detect the electrochemical signal under conditions of full film lubrication in conformal contact.The surface of the slider was analyzed by scanning electron microscopy,metallographic microscope and surface profiler.It was found that the adsorption of protein first occurs at the entrance of the slider and gradually extends to the exit zone along with some corrosion.Experiments showed that speed,inclination,load can affect the adsorption of protein.