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，它占发达国家国内生产总值的2%至6%，而在乘用车中，三分之一的燃料能源用于克服发动机、传动装置、轮胎和刹车中的摩擦。除了能量，摩擦和磨损对矫形设备也很重要。各种情况，最明显的骨关节炎，可能导致患者需要髋关节和膝关节的假体关节植入物。每年，随着婴儿潮一代的年龄增长，患者寿命延长，生活更加活跃，对髋关节置换术的需求也在增加，预计到2030年，美国髋关节置换术的需求将从2005年增长174%，达到57.2万人。该项目旨在了解技术和生物医学应用中使用的材料摩擦和磨损的一些基本过程。提高对这些过程的理解可能对设计更好的商业应用系统以及更持久的植入装置至关重要。该项目还将协助代表性不足的群体参与研究、向高中开展外联活动，并通过讲习班和科学外联加强研究和教育基础设施。本项目采用实验和理论相结合的方法，建立了摩擦学中重要的弱界面和边缘层变形的一些基础材料科学。实验组件利用了一个原位支架，可以在透射电子显微镜下观察摩擦学相关实验期间的样品，实时监测纳米级结构和化学变化。摩擦学过程的现场观察提供了关于发生的基本过程的独特信息，这些信息最多只能从其他实验中推断出来。已经有一些案例表明，所发生的事情已经导致了对纳米级摩擦学过程的公认观点的修订，而且几乎可以肯定的是，这项工作还会有更多的进展。理论部分将是将一些已知对强界面工作良好的现有材料科学模型应用于弱界面的情况，并从这种尝试中提取通用模型，与实验协同。该项目的全球战略是将滑动过程中发生的纳米级过程作为自下而上的材料科学问题来研究。这项工作的一些具体目标包括对摩擦层形成的现场观察，了解韧性和非韧性材料边缘层的变形，对摩擦化学变化的现场观察，主要与基于位错的连续体模型相结合。

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.