原子尺度摩擦行为的分子动力学模拟

应用大规模分子动力学方法，模拟了具有原子级光滑和原子级粗糙形貌的刚性球形探头与弹性平面基体的干摩擦行为，研究了无/有粘附条件下的载荷与摩擦力、载荷与真实接触面积，以及摩擦力与真实接触面积之间的关系，对纳米尺度下的摩擦行为规律进行了分析。几种系统的真实接触面积－载荷关系都与相应的连续力学接触模型定性的一致，它们分别是Hertz光滑表面接触模型、Greenwood-Williamson粗糙表面接触模型和Maugis-Dugdale粘着接触模型。无论是由光滑表面还是粗糙表面构成的摩擦系统，在无粘附条件下摩擦力与载荷成正比，而摩擦力与真实接触面积之间没有一个简单的关系；在粘附条件下摩擦力与真实接触面积成正比，而摩擦力与载荷之间表现为Maugis-Dugdale模型预测的亚线性关系。我们的研究表明，当表面作用从无粘附到粘附时，控制摩擦力的决定因素从载荷转变为接触面积，摩擦行为从载荷控制摩擦转变为粘着控制摩擦。

Molecular dynamics simulations of atomic-scale friction behavior

The friction behaviors between rigid spherical tips with different atomic scale rough topography and the elastic flat substrate are simulated using large-scale molecular dynamics method .The relationship between friction and load, real contact area and load, friction and real contact area are analyzed for non-adhesion and adhesion to study the friction behavior laws on nanometer scale. The results show that the relations between real contact area and load of the studied systems are all agree with the corresponding continuum contact models, such as Hertz smooth contact model, Greenwood-Williamson rough contact model and Maugis-Dugdale adhesive contact model. For the non-adhesive contacts, the friction-load relations are linear for both smooth surface system and rough surface system, while there is no simple relationship between friction and real contact area. However, the relationships between friction and real contact area are linear for the adhesive contacts, while the friction-load relations are sublinear and agree with Maugis-Dugdale model prediction. Our research shows that when changed from non-adhesion to adhesion, the decisive factor of friction will transfer from load to contact area, and the friction behavior will transfer from load-controlled friction to adhesion-controlled friction.