The breakdown of continuum models for mechanical contacts
The breakdown of continuum models for mechanical contacts
复制标题
DOI：
10.1038/nature03700
复制
发表时间：
2005-06-16
期刊：
影响因子：
64.8
通讯作者：
Robbins, MO
中科院分区：
文献类型：
--
作者：
Luan, BQ;Robbins, MO
作用在表面之间原子接触区域内的力在摩擦和粘附中起着核心作用。这种力传统上使用连续接触力学（1）计算，已知当接触半径接近原子尺寸时，连续接触力学会分解。然而，接触力学正在以更小的长度应用，这是由于人们对将设备缩小到纳米尺度的兴趣（2，3），创造具有优化机械性能的纳米结构材料（3，4），以及理解宏观摩擦和粘附的分子起源（5，6）。在这里，我们使用分子模拟来测试理想条件下接触力学的极限。我们的研究结果表明，在大部分的固体中的原子离散性没有显着的影响，但原子尺度的表面粗糙度，总是由离散原子产生的连续理论导致显着的偏差。接触面积和应力可以改变两倍，而摩擦和横向接触刚度改变一个数量级。这些变化可能会影响许多宏观粗糙表面的连续预测，其中研究（7，8）表明，总接触面积被分解为许多具有非常小的平均半径的独立区域。
Forces acting within the area of atomic contact between surfaces play a central role in friction and adhesion. Such forces are traditionally calculated using continuum contact mechanics(1), which is known to break down as the contact radius approaches atomic dimensions. Yet contact mechanics is being applied at ever smaller lengths, driven by interest in shrinking devices to nano-metre scales(2,3), creating nanostructured materials with optimized mechanical properties(3,4), and understanding the molecular origins of macroscopic friction and adhesion(5,6). Here we use molecular simulations to test the limits of contact mechanics under ideal conditions. Our findings indicate that atomic discreteness within the bulk of the solids does not have a significant effect, but that the atomic-scale surface roughness that is always produced by discrete atoms leads to dramatic deviations from continuum theory. Contact areas and stresses may be changed by a factor of two, whereas friction and lateral contact stiffness change by an order of magnitude. These variations are likely to affect continuum predictions for many macroscopic rough surfaces, where studies(7,8) show that the total contact area is broken up into many separate regions with very small mean radius.