Contact, Adhesion and Friction: From Atomic Interactions to Macroscopic Behavior

接触、粘附和摩擦：从原子相互作用到宏观行为

• 批准号: 1411144
• 负责人: Mark Robbins
• 金额: $ 52万
• 依托单位: Johns Hopkins University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2014
• 资助国家: 美国
• 起止时间: 2014-09-01 至 2019-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1411144&HistoricalAwards=false
• 关键词: Contact; Adhesion; Friction; Atomic; Interactions

Nontechnical SummaryFriction and adhesion affect almost all aspects of technology and everyday life. Despite their importance, our fundamental understanding of their origins and our ability to predict them in practical applications has remained limited. In large part, this is because of the wide range of length scales that are important. Adhesion and friction forces between surfaces result from interactions in regions where atoms are separated by less than a nanometer, but the geometry of these contact regions and the forces within them are determined by subsurface deformations on micrometer and longer scales. Over the last decade, advances in computational algorithms and hardware have begun to allow us to capture all of these length scales for the first time. The results have revealed qualitative shortcomings of traditional engineering models and resulted in simple equations that predict the area and stiffness of the contacts between rough surfaces. The proposed research will extend these studies to calculate friction and adhesive forces. The goal is to provide new understanding of fundamental processes that will allow predictive models for the relation between surface roughness and macroscopic friction and adhesion to be developed. New computational tools will be developed and shared as open source software. Technical SummaryContact, adhesion and friction are complex problems that involve a wide range of length scales. Atomic-scale interfacial interactions determine adhesive and frictional forces, but the area where these forces operate is determined by surface roughness and substrate deformation on nanometer to micrometer or longer scales. Traditional models of contact, adhesion and friction are based on macroscopic continuum equations with phenomenological constitutive relations for the interfacial interactions and macroscopic deformations. By their very nature, continuum equations do not include effects associated with discrete atoms, but most of the adhesive energy comes from changes in separation by a few angstroms and lateral frictional forces on a crystal are periodic with displacements by a lattice constant. The proposed research will address fundamental questions associated with the gaps between atomistic and continuum descriptions. These include the relation between atomic structure and detachment forces, the origins of friction and its connection to roughness, plasticity and disorder, and the extent of correlations in the dynamics at the interface. The goal is to provide new understanding of the physical processes at different scales and develop macroscopic models that incorporate atomic level processes.Efficient multiscale methods that retain atomistic detail at the interface and capture the long-range response of the substrate will be extended, ported to open source simulation packages, and used to simulate contact and friction. The simulations will examine contact of planes and spheres with self-affine or experimentally measured surface roughness. The response of crystals, polymer glasses and elastomers will be studied in elastic and plastic limits with different atomic-scale roughness and adhesive interactions. Studies of contact and adhesion will determine how the contact area and detachment force are related to interfacial interactions, material properties and surface roughness. Studies of friction will address how interactions within these contacts lead to static and kinetic friction, how roughness and plasticity contribute to friction, and examine precursors to steady sliding where only part of the surface slips forward.

摩擦和附着力影响着技术和日常生活的几乎所有方面。尽管它们很重要，但我们对其起源的基本了解以及我们在实际应用中预测它们的能力仍然有限。在很大程度上，这是因为重要的长度尺度范围很广。表面之间的粘附力和摩擦力是由原子间隔小于一纳米的区域中的相互作用引起的，但是这些接触区域的几何形状和它们内部的力由微米和更长尺度上的亚表面变形决定。在过去的十年里，计算算法和硬件的进步已经开始让我们第一次捕捉到所有这些长度尺度。结果揭示了传统的工程模型的定性缺陷，并导致简单的方程，预测粗糙表面之间的接触面积和刚度。拟议的研究将扩展这些研究，以计算摩擦力和粘附力。 我们的目标是提供新的理解的基本过程，将允许预测模型的表面粗糙度和宏观摩擦和粘附力之间的关系被开发。新的计算工具将作为开放源码软件开发和共享。技术总结接触、粘附和摩擦是涉及各种长度尺度的复杂问题。原子尺度的界面相互作用决定了粘附力和摩擦力，但这些力作用的区域由纳米至微米或更长尺度上的表面粗糙度和基底变形决定。传统的接触、粘附和摩擦模型是基于宏观连续方程，其界面相互作用和宏观变形具有唯象的本构关系。就其本质而言，连续体方程不包括与离散原子相关的效应，但大部分粘附能来自几埃的分离变化，晶体上的横向摩擦力是周期性的，位移为晶格常数。拟议的研究将解决与原子论和连续描述之间的差距相关的基本问题。这些包括原子结构和分离力之间的关系，摩擦的起源及其与粗糙度，可塑性和无序的联系，以及界面处动力学的相关程度。我们的目标是提供在不同尺度上的物理过程的新的理解和发展宏观模型，包括原子水平的processes.Efficient多尺度的方法，保留在界面处的原子细节和捕获的远程响应的基板将被扩展，移植到开源的仿真软件包，并用于模拟接触和摩擦。模拟将检查接触的平面和球体与自仿射或实验测量的表面粗糙度。晶体，聚合物玻璃和弹性体的响应将在弹性和塑性极限与不同的原子尺度粗糙度和粘合剂的相互作用进行研究。接触和粘附力的研究将确定接触面积和分离力与界面相互作用、材料特性和表面粗糙度的关系。摩擦的研究将解决这些接触内的相互作用如何导致静摩擦和动摩擦，粗糙度和塑性如何对摩擦做出贡献，并检查只有部分表面向前滑动的稳定滑动的前体。