Effect of non-spherical bearing geometry on transient elastohydrodynamic lubrication in metal-on-metal hip joint implants
Effect of non-spherical bearing geometry on transient elastohydrodynamic lubrication in metal-on-metal hip joint implants
复制标题
非球形轴承几何形状对金属对金属髋关节植入物瞬态弹流动力润滑的影响
DOI：
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发表时间：
2007
期刊：
影响因子：
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通讯作者：
Z. Jin
中科院分区：
文献类型：
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作者：
F. C. Wang;Z. Jin
摘要建立了步行条件下人工髋关节植入物非球形支承面的瞬态弹流润滑模型。在本研究中，采用标称球窝配置来代表球形股骨头和非球形髋臼杯之间的关节。轴承几何形状的非球形度由相对于标称球面的三个椭球半轴长度变化的椭球来描述。为了便于数值模拟，选取了合适的球坐标系和网格.采用等效离散球面卷积模型和相应的球面快速傅里叶变换技术来计算球头和非球面杯表面的弹性变形。随后采用瞬态润滑模型研究了椭圆杯的非球形度对典型金属对金属髋关节植入物瞬态弹流润滑的影响。结果发现，非球形度可以有一个很大的影响，预测的膜厚和最大压力分别高达43%和17%，在这项研究中考虑的条件，这取决于非球形杯相对于屈曲-伸展方向的方向。此外，还讨论了与润滑相关的髋臼杯支承表面的非球形度，这种非球形度可能由制造中的形状公差或临床应用中的磨损引起。
Abstract A transient elastohydrodynamic lubrication model for non-spherical bearing surfaces of artificial hip joint implants under walking conditions has been developed. A nominal ball-in-socket configuration was employed to represent the articulation between a spherical femoral head and a non-spherical acetabular cup in this study. The non-sphericity of the bearing geometry was described by an ellipsoid with the variation of three ellipsoidal semi-axis lengths relative to the nominal spherical surface. An appropriate spherical coordinate system and mesh grids were selected to facilitate the numerical simulation. Both the equivalent discrete spherical convolution model and the corresponding spherical fast Fourier transform technique were used to evaluate the elastic deformation of both the spherical head and non-spherical cup surfaces. The transient lubrication model was subsequently adopted to investigate the effect of nonsphericity of an ellipsoidal cup on the transient elastohydrodynamic lubrication in a typical metal-on-metal hip joint implant. It was found that the non-sphericity could have a large effect on the predicted film thickness and the maximum pressure by as much as ∼43 and 17 per cent respectively, for the conditions considered in this study, depending on the orientation of the non-spherical cup relative to the flexion-extension direction. Furthermore, the non-sphericity of the cup bearing surface, which can be caused by shape tolerance in manufacturing or wear in clinical application, was discussed, in relation to the lubrication.