Research On Tribological Properties Of Textured UHMWPE

As artificial joint material, ultrahigh molecular weight polyethylene(UHMWPE) has been applied in Clinical Medicine for 40 years. UHMWPE has several excellent properties, including bio-compatibility, chemical stability, low friction coefficient and effective impact load damping, but with the increase of using time, it still has several prombles on friction and wear. Firstly, compared with the natural joint, the friction of the artificial joint consisted with UHMWPE is much higher than the natural joint which friction coefficient is 0.005. Secondly, osteolysis and aseptic loosening which are caused by UHMWPE wear debris are the main factors leading to the failure of joint replacement. So it becomes important to improve the tribological properties of UHMWPE.In this thesis, patterns of micro-dimples were created on UHMWPE surfaces using the micro-fabrication technique. 72 kinds of Surface Texture had been machining with different dimple ratio, dimple depth and dimple diameter. The mechanical properties of UHMWPE, such as water absorption, contact angle and hardness were also measured. At last, the tribological experiments were carried out using MMW-1A friction and wear tester to investigate the tribological properties of textured UHMWPE with different geometric parameters. This thesis mainly analysized the effect of the experiments with different geometric parameters and optimized the geometric parameters of surface texture. Lubrication mechanism and wear mechanism of textured UHMWPE has also been discussed. The main researches and results are showed as follows:Firstly, the influence of UHMWPE preparation process on its mechanical properties was researched, and the wettability of textured surfaces with different geometrical parameters was also analyzed.Secondly, compared with untextured surface, the tribological properties of textured UHMWPE surfaces were researched. The geometric parameters of surface texture had been optimized. The experimental results show that textured surface has superior tribological properties. The pattern with micro-pits of diameter 50μm, depth of 10μm and ratioof 22.9%, has an obvious friction reduction at the load of 100N - the friction coefficient is 72.8%~85.7% lower than the untextured one's friction coefficient under four different rotational speed. The pattern with micro-pits of diameter 50μm, depth of 15μm and ratioof 29.9%, has an obvious friction reduction at the load of 700N - the friction coefficient is 66.7%~80.3% lower than the untextured one's friction coefficient under four different rotational speed.Thirdly, the pattern with micro-pits of diameter 50μm, depth of 15μm and ratioof 29.9%, has an obvious wear reduction - the wear volume is 64.5% lower than the untextured one's. The wear mechanism of untextured UHMWPE is mainly abrasive wear, adhesive wear and fatigue wear. The wear mechanism of textured UHMWPE with the pattern of dimple ratio 29.9%, dimple depth 15μm, dimple diameter 50μm is mianly abrasive wear.