Curran Sarah, Hoskin Tom, Williams Sarah, Scholes Susan C, Kinbrum Amy, Unsworth Anthony
School of Engineering and Computing Sciences, Durham University, Durham, UK.
Proc Inst Mech Eng H. 2013 Aug;227(8):847-58. doi: 10.1177/0954411913488508. Epub 2013 May 3.
The role of surface tension in the lubrication of metal-on-metal (CoCrMo alloy) hip resurfacings has been investigated to try to explain why all metal joints fail to be lubricated with simple water-based lubricants (sodium carboxymethyl cellulose), which have similar rheology to synovial fluid, but are lubricated with the same fluid with the addition of a proportion of bovine serum. As part of this study, surfactants, in the form of detergents, when added to carboxymethyl cellulose, have been shown to produce a predominantly fluid-film lubrication mechanism with friction even lower than the biological lubricant containing serum. Friction factors were reduced by 80% when a detergent was added to the lubricant. It is considered that the failure of the water-based fluids to generate fluid-film lubrication is due to the fact that 'boundary slip' takes place where the fluid does not fully attach to the bounding solid surfaces as assumed in Reynolds' equation, thereby drawing in less lubricant than predicted from hydrodynamic theory. The addition of surfactants either in the form of natural materials such as serum or in the form of detergent reduces surface tension and helps the water-based lubricant to attach more fully to the bounding surfaces resulting in more fluid entrainment and thicker fluid-film formation. This was confirmed by up to 70% lower wear being found when these joints were lubricated in a detergent solution rather than 25% bovine serum.
研究了表面张力在金属对金属（钴铬钼合金）髋关节表面置换润滑中的作用，以试图解释为何所有金属关节都无法用与滑液具有相似流变学特性的简单水基润滑剂（羧甲基纤维素钠）进行润滑，却能在添加一定比例牛血清的相同液体中实现润滑。作为该研究的一部分，已表明以洗涤剂形式存在的表面活性剂添加到羧甲基纤维素中时，会产生以流体膜润滑为主的机制，其摩擦力甚至低于含血清的生物润滑剂。向润滑剂中添加洗涤剂后，摩擦系数降低了80%。据认为，水基流体无法产生流体膜润滑是因为在流体未如雷诺方程所假设的那样完全附着于边界固体表面的地方发生了“边界滑移”，从而吸入的润滑剂比流体动力学理论预测的要少。添加天然材料（如血清）形式或洗涤剂形式的表面活性剂会降低表面张力，并有助于水基润滑剂更充分地附着于边界表面，从而导致更多的流体夹带和更厚的流体膜形成。当这些关节在洗涤剂溶液中而非25%牛血清中润滑时，磨损降低了多达70%，这证实了上述观点。
