Basic Study of Lubrication in Artificial Joints with Compliant Materials

用针盘式摩擦测试装置测量了柔顺材料（硅橡胶、聚脲烷和聚乙烯醇水凝胶）与坚硬光滑材料（不锈钢、氧化铝陶瓷和石英玻璃）的摩擦和润滑。结果表明：疏水材料的启动摩擦大于亲水材料的启动摩擦；启动后，与柔性材料的摩擦很小，并测量了表面粗糙度对摩擦的影响。起动摩擦依赖于载荷和滑液成分作为润滑剂的静止时间。在行走润滑髋关节模拟器的流体压力测量中，足跟冲击载荷的大部分由流体压力支撑。从测量的摩擦力矩来看，在行走周期中，疏水材料的套筒产生的摩擦力一般高于亲水材料的套筒。由于髋关节的挤压膜效应，在高载荷下摩擦系数较低。高含水量聚乙烯醇-水凝胶套筒在高接触压力下，由于配合面之间的黏附作用，摩擦系数高，摩擦系数随接触压力的降低而减小。当这种材料用于人工关节时，必须长期保持良好的润滑条件。

Friction and lubrication of compliant materials (Siliconrubber, Poly-urehtane and Polyvinylalcohol-hydrogel) versus hard and smooth mateials (Stainless steel, Alumina ceramic and Quartz glass) were measured with a pin-on disk friction testing apparatus. The results shows that start up friction with hydrophobic materials were higher than that with hydrophilic materials. After start up, friction with compliant materials was low and the effect of surface roughness on friction was measured. The start up friction was dependent on standstill time with load and constituents of synovial fluid as lubricant.In the measurement of fluid pressure with a hip joint simulator for lubrication in walking, most of impusive load at heel strike was supported by the fluid pressure. According to the measured frictional torque, sockets of hydrophobic materials result higher friction than the socket of hydrophilic materials in general through the walking cycles. Frictional coefficient was low at high loading due to squeeze film effect in hip joints.Socket of high water content Polyvinylalcohol-Hydrogel resulted high frictional coefficient under high contact pressure due to adhesion between the mating surfaces, and friction decreased with a decrease of contact pressure. When such material is used for an artificial joint, good lubrication condition must be maintained for long term application.