Study On The Biotribology Of Contact Interface Between Materials Of Artificial Knee Joint

Co Cr Mo alloys and Ultra-high molecular weight polyethylene(UHMWPE) are the most widely used materials for knee implants due to their excellent mechanical properties, good wear resistance and outstanding corrosion resistance. For combined artificial knee joint, there are different motion forms of friction and wear on the mating surface between femur and tibia under the cyclic loading of body movement, which may induce implant failure and even endanger human health due to long-term effects. Therefore, it is of great significance to performing the research on the tribological property of interface between prosthesis femur and tibia of artificial knee joint.Friction and wear tests for Co Cr Mo/UHMWPE contact simulated the contact mode between prosthesis femur and tibia were carried out in different motion forms and different loading forms, respectively. Combined with a variety of analysis means, the tribological property and damage mechanism between Co Cr Mo and UHMWPE in different conditions were revealed. The main conclusions are as follows:Firstly, the results of swing friction tests under dynamic loading revealed that friction coefficient curves could be divided into the decline stage, rising stage and stable stage. The stable value of friction coefficient increases with the increase of the axial peak load and swing angle amplitude. The results of torsional friction tests under dynamic loading revealed that friction torque curves could be divided into the decline stage, rising stage and stable stage.Secondly, the results of swing and torsional friction tests under static loading revealed that friction coefficient and torsional friction torque curves could be divided into rising stage and stable stage. The stable values of swing friction coefficient and torsional friction torque under static loading are more than the stable values under dynamic loading. The results of friction tests with composite motion revealed that the stable values of swing friction coefficient and torsional friction torque under composite motion are smaller than the stable values under single motion. Therefore, the components of swing and torsion are mutually sharing role in composite motion.Thirdly, the analysis of UHMWPE wear loss revealed that the generated UHMWPE wear loss under dynamic loading is more than it under static loading. On the other hand, the generated UHMWPE wear loss under composite motion is more than it under single motion. Moreover, there is obvious reducing effect on friction and wear for Co Cr Mo/UHMWPE contact when uninstall and setting.Fourth, the friction tests for Co Cr Mo/UHMWPE contact revealed that the surface roughness of UHMWPE decreased after friction because the sample of Co Cr Mo has a “polishing” effect on UHMWPE. At the same time, the surface roughness of Co Cr Mo increased after friction. Wear scars appeared along the swing direction on the surface of Co Cr Mo and UHMWPE in the swing friction experiments. In torsional friction tests, circular arc shaped scratches and ploughs appeared on the edge of samples. However, obvious damage didn’t appeare in the center region of UHMWPE because of small relative motion with Co Cr Mo in static torsional tests. Meanwhile, concave and ridge appeared in the center region of UHMWPE because of sustained alternating stress from Co Cr Mo in dynamic torsional tests. In firction tests with composite motion, only wear scars along the swing direction appeared on surface of samples, so it found that composite motion is mainly controlled by the component of swing. For the Co Cr Mo/UHMWPE counter-pair, the wear was controlled by abrasive mechanism which generated the ploughs on Co Cr Mo while the wear was controlled by abrasive mechanism and fatigue wear mechanism on UHMWPE.