Atomic Scale Friction: What can be Deduced from the Response to a Harmonic Drive?
Atomic Scale Friction: What can be Deduced from the Response to a Harmonic Drive?
复制标题
原子级摩擦：从谐波驱动的响应中可以推断出什么？
DOI：
10.1103/physrevlett.81.1227
复制
发表时间：
1998
影响因子：
8.6
通讯作者：
J. Klafter
中科院分区：
文献类型：
--
作者：
V. Zaloj;M. Urbakh;J. Klafter
人们越来越多地试图了解摩擦力和纳米系统微观性质之间的关系。最近关于摩擦的研究[1-9]揭示了广泛的现象和新的行为，这些现象和新行为有助于阐明一些已经被视为教科书材料的“旧”概念。其中包括静摩擦力和动摩擦力、向滑动的转变和变薄，这些都已被广泛讨论，但其微观意义仍然缺乏。通常，有两种方法用于研究受限液体的剪切力：流变学(振荡外驱动)和摩擦学(恒定驱动速度)。总的来说，这两种方法得出了相似的结果，但对纳米级受限系统中流变学和摩擦学之间的关系知之甚少。建立这些方法之间的关系对于建立对剪切响应的统一描述以及相关领域的进一步进展至关重要。在这封信中，我们主要关注这个问题的流变学方面及其与摩擦学的关系。我们提出的预测可以通过同时分析弹簧力和剪切模数的时间序列来进行实验验证。我们建议对观测到的有效粘度的显著增加[3，6]和薄约束系统中的剪切稀化效应[3，10-12]提出解释。为了模仿常用的实验构型[13]，我们引入了嵌入在两个板之间的链的模型，其中一个是外部驱动的，如图1a所示。质量为M的顶板连接到弹簧常数K1的弹簧和作为响应弹簧的弹簧K2，所述弹簧常数K1被谐波驱动。这条链由N个相同的粒子组成，每个粒子的质量都是m0，它们相互作用是谐和的。系统(链1板块)的动力学行为遵循运动方程：
There has been a growing number of attempts to understand the relationship between frictional forces and the microscopic properties of nanosystems. Recent studies on friction [1‐ 9] have exposed a broad range of phenomena and new behaviors which help shed light on some “old” concepts which are already considered textbook material. These include the static and kinetic friction forces, transition to sliding, and thinning, which have been widely discussed but whose microscopic meaning is still lacking. There have been, generally, two approaches used to investigate shear forces of confined liquids: rheological (oscillatory external drive) and tribological (constant driving velocity). In the bulk the two approaches lead to similar results, but less is known about the relationship between rheology and tribology in nanoscale confined systems. Establishing a relationship between these approaches is essential for creating a unifying description of the response to shear and for further progress of related fields. In this Letter we concentrate on the rheological side of the problem and its relationship to tribology. Our proposed predictions can be tested experimentally by simultaneously analyzing the time series of the spring forces and the shear moduli. We suggest an interpretation to the observed dramatic enhancement in the effective viscosity [3,6] and to the effect of shear thinning in thin confined systems [3,10‐ 12]. In order to mimic the commonly used experimental configuration [13] we introduce a model of a chain embedded between two plates, one of which is externally driven, as depicted in Fig. 1a. The top plate of mass M is connected to a spring, of spring constant K1, which is harmonically driven, and to a spring K2, which is a response spring. The chain consists of N identical particles each of mass m0, which interact harmonically. The dynamical behavior of the system (chain 1 plates) follows the equations of motion: