Department of Materials Science and Engineering, University of Wisconsin-Madison, Madison 53706-1595, USA.
Department of Microsystems Engineering, University of Freiburg, Georges-Köhler-Allee 103, 79110 Freiburg, Germany.
Phys Rev E. 2018 Aug;98(2-1):023001. doi: 10.1103/PhysRevE.98.023001.
It has been shown that contact aging due to chemical reactions in single asperity contacts can have a significant effect on friction. However, it is currently unknown how chemically induced contact aging of friction depends on roughness that is typically encountered in macroscopic rough contacts. Here we develop an approach that brings together a kinetic Monte Carlo model of chemical aging with a contact mechanics model of rough surfaces based on the boundary element method to determine the magnitude of chemical aging in silica-silica contacts with random roughness. Our multiscale model predicts that chemical aging for randomly rough contacts has a logarithmic dependence on time. It also shows that friction aging switches from a linear to a nonlinear dependence on the applied load as the load increase. We discover that surface roughness affects the aging behavior primarily by modifying the real contact area and the local contact pressure, whereas the effect of contact morphology is relatively small. Our results demonstrate how understanding of chemical aging can be translated from studies of single asperity contacts to macroscopic rough contacts.
已经表明，由于单峰接触中的化学反应引起的接触老化会对摩擦产生重大影响。然而，目前尚不清楚摩擦的化学诱导接触老化如何取决于通常在宏观粗糙接触中遇到的粗糙度。在这里，我们开发了一种方法，将化学老化的动力学蒙特卡罗模型与基于边界元法的粗糙表面接触力学模型结合在一起，以确定具有随机粗糙度的二氧化硅-二氧化硅接触中的化学老化程度。我们的多尺度模型预测，对于随机粗糙接触，化学老化随时间呈对数依赖性。它还表明，随着载荷的增加，摩擦老化从线性依赖转变为非线性依赖于所施加的载荷。我们发现，表面粗糙度主要通过改变实际接触面积和局部接触压力来影响老化行为，而接触形态的影响相对较小。我们的结果表明，如何将对单峰接触的化学老化的理解转化为对宏观粗糙接触的理解。
