In-Situ Observation and Modelling of Friction and Wear Processes at the Nanoscale

摩擦是一种普遍现象；据估计，摩擦占发达国家GDP的2%至6%，在乘用车中，三分之一的燃料能量用于克服发动机、变速器、轮胎和刹车中的摩擦。除了能量，摩擦和磨损对整形外科设备也很重要。各种各样的情况，尤其是骨关节炎，可能会导致患者需要髋关节和膝盖的假体植入。每年，随着婴儿潮一代的老龄化和患者寿命的延长和活跃度的提高，对髋关节置换的需求也在上升，预计到2030年，美国对髋关节置换的需求将比2005年增长174%，达到572,000人。该项目旨在了解在技术和生物医学应用中使用的材料的摩擦和磨损的一些基本过程。对这些过程的更好理解可能对设计商业应用中性能更好的系统以及更持久的植入设备至关重要。该项目还将通过讲习班和科学外展活动，帮助未被充分代表的群体接触研究，在高中开展外联活动，并加强研究和教育基础设施。该项目是一种联合实验和理论方法，旨在建立摩擦学中重要的弱界面和边缘层变形的一些基本材料科学。该实验部件利用原位夹持器，允许在与摩擦学相关的实验期间在透射电子显微镜中观察样品，实时监测纳米级结构和化学变化。对摩擦学过程的现场观察提供了关于正在发生的基本过程的独特信息，充其量只能从其他实验中推断出来。已经有一些案例表明，所发生的事情导致了人们对纳米级摩擦学过程的公认观点的修正，而且几乎可以肯定，这项工作将带来更多的变化。理论部分将把一些现有的材料科学模型应用于弱界面的情况，这些模型对强界面很好地工作，并从这一尝试中提取与实验协同的一般模型。该项目的全球战略是以自下而上的方法将滑动过程中发生的纳米级过程视为材料科学问题。这项工作的一些具体目标包括现场观察摩擦层的形成，了解延性和非延性材料边缘层中的变形，主要结合基于位错的连续介质模型对摩擦化学变化进行现场观察。

Friction is a pervasive phenomenon; by some estimates it represents between 2 and 6 percent of the GDP of developed countries, and in passenger cars, one-third of the fuel energy is used to overcome friction in the engine, transmission, tires, and brakes. Beyond energy, friction and wear are important for orthopedic devices. A variety of conditions, most notably osteoarthritis, may result in need of a patient for prosthetic joint implants of the hips and knees. Every year, as the baby boom generation ages and patients live longer and more active lives the demand for hip replacements rises and in the US is expected to grow 174 percent from 2005 to 572,000 by 2030. This project targets understanding some of the basic processes in friction and wear of materials used in both technological and biomedical applications. An improved understanding of these processes may be pivotal to design of better performing systems in commercial applications as well as longer lasting implant devices. This project will also assist in the exposure of underrepresented groups to research, outreach activities to high-schools and enhance the Infrastructure for Research and Education through workshops and science outreach.This project is a joint experimental and theoretical approach to establish some of the basic materials science of weak interfaces and selvedge layer deformation important in tribology. The experimental component exploits an in-situ holder which allows the observation of samples during tribologically relevant experiments in a transmission electron microscope, monitoring nanoscale structural and chemical changes in real time. In-situ observations of tribological processes provide unique information about the fundamental processes taking place which can at best only be inferred from other experiments. There already have been cases where what takes place has led to revision of accepted views of tribological processes at the nanoscale, and there almost certainly will be more from the work. The theoretical component will be to apply some of the existing materials science models which are known to work well for strong interfaces to the case of weak interfaces, and from this attempt to extract general models, synergistic with the experiments. The global strategy of this project is to look at the nanoscale processes taking place during sliding as a materials science problem in a bottom-up approach. Some of the specific targets of the work involve in-situ observations of the formation of tribolayers, understanding the deformation in the selvedge layer for ductile and non-ductile materials, in-situ observations of tribochemical changes coupled primarily with dislocation-based continuum modelling.