PGI-1, FZ Jülich, Germany.
Soft Matter. 2017 Sep 27;13(37):6349-6362. doi: 10.1039/c7sm00753a.
We study a simple contact mechanics model of the vertebrate cartilage, which includes (bulk) osmotic effects. The surface roughness power spectrum of a pig cartilage is obtained from the measured surface topography. Using the Reynolds equations with fluid flow factors, calculated using the Persson contact mechanics theory and the Bruggeman effective medium theory, we show how the area of contact and the average interfacial separation change with time. We found that in most cases the contact area percolates, resulting in islands of confined fluid which carry most of the external load. Most importantly, we find that the pressure in the area of real contact is nearly independent of the external load, and well below 1 MPa. This allows the surfaces in the area of "real contact", to be separated (at nanometer range separation distance) by osmotic repulsion, resulting in a very small (breakloose) friction force observed even after a long time of stationary contact.
我们研究了一种简单的脊椎动物软骨接触力学模型，其中包括（体相）渗透效应。猪软骨的表面粗糙度功率谱是从测量的表面形貌中获得的。利用包含流体流动因素的雷诺方程，根据佩尔逊接触力学理论和布鲁格曼有效介质理论进行计算，我们展示了接触面积和平均界面分离随时间的变化。我们发现，在大多数情况下，接触面积会发生渗流，从而形成承载大部分外部负载的受限流体岛。最重要的是，我们发现实际接触区域的压力几乎与外部负载无关，远低于 1 MPa。这使得“实际接触”区域中的表面可以通过渗透斥力分离（在纳米级分离距离），从而导致即使在长时间的静止接触后，也会观察到非常小的（断裂）摩擦力。
