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首页> 外文会议>Leeds-Lyon Symposium on Tribology; 19990914-17; Leeds(GB) >Elastohydrodynamic lubrication analysis of UHMWPE hip joint replacements
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Elastohydrodynamic lubrication analysis of UHMWPE hip joint replacements

机译：超高分子量聚乙烯髋关节置换物的弹性流体动力润滑分析

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摘要

A simple ball-in-socket configuration was considered in this analysis of the lubrication of a typical artificial hip joint replacement, consisting of an UHMWPE acetabular cup and a metallic or ceramic femoral head. The cup was assumed to be stationary whilst the ball was assumed to rotate at a steady angular velocity under a constant load. The Reynolds equation was solved in spherical coordinates, simultaneously in conjunction with the corresponding elasticity equation based upon the constrained column model, using the Newton-Raphson method. The prediction of the film thickness and pressure distribution has been performed for a typical example of UHMWPE total hip joint replacements under average kinetic conditions during walking. An equivalent ballon-plane model using an effective radius was also used to predict the minimum film thickness and make comparisons with the ball-in-socket model for this particular example. The numerical method has been found to be quite successful under realistic conditions experienced in current ultra high molecular weight polyethylene (UHMWPE) total hip joint replacements. The predicted minimum film thickness for the example chosen is about 15% smaller than that based upon the corresponding ball-on-plane model, due to the higher-pressure distribution around the cup in order to balance the applied load and consequently the smaller film thickness for the ball-in-socket model. The results obtained in this study show that a significant increase in the minimum film thickness is achieved along with a corresponding fall in pressure when the elastic deformation of the UHMWPE bearing surface is considered. However, the predicted lubricant film thickness is not greater than the surface roughness of the UHMWPE bearing surface and hence asperity contact, though reduced by an improved fluid film, will still exist.
机译：在对典型的人工髋关节置换物（包括UHMWPE髋臼杯和金属或陶瓷股骨头）进行润滑的分析中，考虑了一种简单的球窝结构。假设杯子是固定的，而假设球在恒定负载下以稳定的角速度旋转。雷诺方程是在球坐标系中求解的，同时使用牛顿-拉夫森方法与基于约束柱模型的相应弹性方程同时求解。对于膜厚和压力分布的预测，是在行走过程中在平均动力学条件下对UHMWPE全髋关节置换术的典型例子进行的。使用此有效半径的等效球形平面模型还用于预测最小膜厚，并与该特定示例的插口式球形模型进行比较。在目前的超高分子量聚乙烯（UHMWPE）全髋关节置换术中遇到的实际条件下，已经发现数值方法是非常成功的。对于所选示例，预测的最小薄膜厚度比基于相应的平面模型的薄膜的最小薄膜厚度小约15％，这是由于杯周围较高的压力分布以平衡施加的载荷，因此薄膜厚度较小用于球插式模型。在这项研究中获得的结果表明，当考虑到UHMWPE轴承表面的弹性变形时，最小膜厚的显着增加以及相应的压力下降。然而，预测的润滑剂膜厚度不大于UHMWPE轴承表面的表面粗糙度，因此，尽管被改善的流体膜减少了，但粗糙接触仍然会存在。

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