Friction laws at the nanoscale
Friction laws at the nanoscale
复制标题
DOI：
10.1038/nature07748
复制
发表时间：
2009-02-26
期刊：
影响因子：
64.8
通讯作者：
Szlufarska, Izabela
中科院分区：
文献类型：
--
作者：
Mo, Yifei;Turner, Kevin T.;Szlufarska, Izabela
宏观摩擦定律通常不适用于纳米级接触。尽管连续介质力学模型被预测在纳米尺度上会崩溃(1)，但由于缺乏更好的理论，它们继续被应用。了解摩擦力如何依赖于这些尺度上的施加载荷和接触面积，对于设计具有最佳机械性能的小型化设备至关重要（2,3）。本文采用具有真实力场的大尺度分子动力学模拟来建立干燥纳米尺度接触中的摩擦规律。我们证明摩擦力线性地依赖于在接触面上化学相互作用的原子数量。通过将接触面积定义为与相互作用原子的数量成正比，我们表明宏观上观察到的摩擦力和接触面积之间的线性关系可以扩展到纳米尺度。我们的模型预测，随着接触面之间的附着力减少，摩擦力对负载的依赖从非线性转变为线性。这种转变与几个纳米级摩擦实验的结果一致（4-7）。我们证明了连续介质力学的破裂可以被理解为接触的粗糙（多粗糙度）性质的结果，并表明摩擦的粗糙度理论（8-10）可以应用于纳米尺度。
Macroscopic laws of friction do not generally apply to nanoscale contacts. Although continuum mechanics models have been predicted to break down at the nanoscale(1), they continue to be applied for lack of a better theory. An understanding of how friction force depends on applied load and contact area at these scales is essential for the design of miniaturized devices with optimal mechanical performance(2,3). Here we use large-scale molecular dynamics simulations with realistic force fields to establish friction laws in dry nanoscale contacts. We show that friction force depends linearly on the number of atoms that chemically interact across the contact. By defining the contact area as being proportional to this number of interacting atoms, we show that the macroscopically observed linear relationship between friction force and contact area can be extended to the nanoscale. Our model predicts that as the adhesion between the contacting surfaces is reduced, a transition takes place from nonlinear to linear dependence of friction force on load. This transition is consistent with the results of several nanoscale friction experiments(4-7). We demonstrate that the breakdown of continuum mechanics can be understood as a result of the rough (multi-asperity) nature of the contact, and show that roughness theories(8-10) of friction can be applied at the nanoscale.