步态条件下人工膝关节线接触弹流润滑分析

参照关节模拟试验机的运动和力学参数,利用多重网格技术对人工膝关节摩擦副进行了1个步态周期仿人体环境线接触弹流润滑仿真,关节支承表面的弹性变形按半无限体计算.同时,观察了几种参数对流体压力分布和膜厚形状的影响.结果表明:在1个步态周期内,中心压力与载荷变化基本相同,且等效曲率半径的变化会引起中心压力的跳跃.站立相时在卷吸和挤压膜效应的共同作用下,中心膜厚呈逐步减小并伴随着波动;摆动相时,载荷固定,膜厚的变化主要与卷吸速度有关.减小胫骨平台曲率半径有助于提高滑液膜厚度;延长步态周期的时间,会使滑液膜厚减小.

Analysis on the Elastohydrodynamic Lubrication of Knee Implant Using a Line Contact Model under Simulated Walking Conditions

In this paper, a time-dependent analysis on elastohydrodynamic lubrication (EHL) in the knee-joint pair was carried out using a line contact model. Both load and speed were considered as cyclic functions representative of normal walking. A numerical method was developed to solve the equations with a multi-grid solver, in which the bearing surface deformation was obtained from elastic equation of a semi-infinite plane. The variations in predicted pressure distribution and film thickness profile with time were observed under different conditions. The results showed that the variation in the predicted central pressure was similar to the variation of load in a gait cycle, and the change of equivalent radius can make a significant change in the predicted central pressure. In the stance phase, the film thickness gradually decreased with fluctuation because of the combined effects of the entrainment and squeezing film actions. In the swing phase, however, the variation in the film thickness was only related to entraining velocity for the constant load. Furthermore, it is pointed out that a reduction of the tibial radius was of benefit to the lubrication film thickness, while a gait cycle extension may be harmful to the film thickness.