Greens function molecular dynamics simulation of sliding, adhesive contacts

这一提议是围绕这样一个问题提出的：固体之间的粘合何时会产生摩擦？从每天的经验来看，我们可能会期待这两个属性之间存在很大程度的相关性。然而，从微观角度来看，这很难理解，因为两种固体上的粗糙度(更精确的物理学术语：破碎的平移不变性)是产生摩擦的基本要求。然而，粗糙度抵消了附着力，每个表面都是微观粗糙的。这项建议的中心目标是为一大类表面确定简单的规则，使我们能够根据一些(主要但不完全是微观)参数来预测(宏观)表面是否以及有多强吸引，以及表面之间不可避免地产生多大的粘着引起的摩擦力。应使用计算机模拟来回答刚才提出的问题。它们允许人们精确地定义所有相关的量，例如表面形貌、固体的弹性性质以及它们之间的相互作用。由于几乎所有表面都具有多尺度粗糙度(事实上，它们可以被认为是几十年来的自相似或分形)，因此模拟也必须反映多个尺度，这反过来又需要有效的方法。由于最近取得的重大进展，可以确定标准，使人们能够用相对简单的规则来预测表面何时粘性。然而，为了解决“有多粘性？”的问题。以及粘着会产生多大的摩擦力？这些方法还需要进一步改进。同样，我们认为，提高我们对温度、等待时间(热老化)和固体厚度对粘附力的影响的了解对于该项目的成功实施至关重要。对刚才提出的问题进行纯粹的实验分析目前似乎不明智，因为从技术上讲，以所需的精度测量足够大的表面地形是不可能的，也是不合理的。此外，只有模拟才允许人们系统地和连续地改变所有相关参数。毫无疑问，为了验证模拟，实验仍然是必不可少的。这项提议的一个目标是应用新获得的见解和新开发的方法来优化具有技术相关性的粘合剂系统(拾音器)的几何形状。在这种情况下，可能值得一提的是，一旦所有功能都被编码起来，探索单个参数对设备性能的影响只需要一小时的人力加上一天的超级计算机时间。

This proposal evolves around the question: When does adhesion between solid bodies cause friction? From every day experience, we might be tempted to expect a large degree of correlation between these two properties. However, this is scarcely understandable from a microscopic view, since roughness (in the more precise jargon of physics: broken translational invariance) on both solids is a basic requirement for friction to occur. Roughness, however, counteracts adhesion and every surface is microscopically rough. The central goal of this proposal is to identify simple rules for a large class of surfaces that allow us to predict from a few (mainly, but not exclusively microscopic) parameters, if and how strongly (macroscopic) surfaces attract and what amount of adhesion-induced friction between the surfaces is unavoidable.Computer simulations shall be used to answer the just raised questions. They allow one to define all relevant quantities, such as the surface topographies, the elastic properties of the solids and their interactions, with mathematical precision. Since virtually all surfaces bear multi-scale roughness (in fact, they can be considered self-similar or fractal over several decades), the simulations must reflect a multitude of scales as well, which, in turn, necessitates efficient methods. Owing to significant progress in the recent past, criteria could be identified allowing one to predict with relatively simple rules when surfaces are sticky. However, in order to address the questions of 'how sticky?' and 'how much friction does adhesion induce?', the methods have to be much further advanced. Likewise, we see it as critical for a successful execution of the project to improve our understanding of the effect of temperature, waiting times (thermal aging), and the influence of the thickness of solid bodies on adhesion.A purely experimental analysis of the just raised question does not appear sensible at the moment, because it is technically not yet possible or unjustifiable expensive to measure sufficiently large surface topographies with the needed precision. In addition, only simulations allow one to vary all relevant parameters systematically and continuously. Experiments yet remain without any doubt indispensible for the validation of simulations. Colleagues outside the framework of this proposal agreed to conduct them.One goal of this proposal is to apply the newly gained insights and newly developed methods to optimize the geometry of adhesive systems (pick-up devices) of technological relevance. In this context, it might be worth mentioning that -- once all features are coded up -- exploring the effect of a single parameter on the device performance necessitates only one hour of manpower plus one day supercomputer time.