Jiang Yijie, Turner Kevin T
Department of Mechanical Engineering and Applied Mechanics, University of Pennsylvania, Philadelphia, Pennsylvania 19104, United States.
School of Aerospace and Mechanical Engineering, University of Oklahoma, Norman, Oklahoma 73019, United States.
ACS Appl Mater Interfaces. 2024 Sep 18;16(37):50004-50011. doi: 10.1021/acsami.4c11933. Epub 2024 Sep 4.
Wear is a ubiquitous phenomenon that limits the life of many engineered components with sliding interfaces through the gradual removal of material. The wear of polymers is crucial in many applications, ranging from bearings to orthopedic implants to nanolithography processes. The wear rate of polymers is strongly affected by the stress and temperature at the interface. The effects of temperature and stress are often described empirically since the wear process involves complex interactions between multiple asperities on rough surfaces over a range of length scales. Nanoscale tribology experiments at the single-asperity level have provided new insights into the underlying mechanisms of wear. Experiments on hard covalently bonded materials, including silicon and diamond, have demonstrated that wear is an atomic attrition wear process that can be modeled using stress-assisted transition state theory. Here, we examine the wear of a common polymer, polymethylmethacrylate (PMMA), at the nanoscale as a function of stress and temperature and show that the polymer wear is controlled by a combination of atomic attrition and viscoelastic relaxation. While the wear experiments are conducted at the nanoscale via atomic force microscopy, the results show that accounting for the local stress distribution at the contact interface is critical to understanding the wear behavior, an effect that was not considered in earlier studies on hard materials. Using a model that accounts for the stress distribution, we demonstrate the ability to predict the wear volume within 8%.
磨损是一种普遍存在的现象，它通过材料的逐渐去除限制了许多具有滑动界面的工程部件的寿命。聚合物的磨损在许多应用中至关重要，从轴承到骨科植入物再到纳米光刻工艺。聚合物的磨损率受界面处的应力和温度强烈影响。由于磨损过程涉及粗糙表面上多个微凸体在一定长度尺度范围内的复杂相互作用，温度和应力的影响通常是通过经验来描述的。单微凸体水平的纳米摩擦学实验为磨损的潜在机制提供了新的见解。对包括硅和金刚石在内的硬共价键合材料的实验表明，磨损是一个原子磨损过程，可以用应力辅助过渡态理论进行建模。在这里，我们研究了一种常见聚合物聚甲基丙烯酸甲酯（PMMA）在纳米尺度下作为应力和温度函数的磨损情况，并表明聚合物磨损是由原子磨损和粘弹性松弛共同控制的。虽然磨损实验是通过原子力显微镜在纳米尺度上进行的，但结果表明，考虑接触界面处的局部应力分布对于理解磨损行为至关重要，这一效应在早期对硬质材料的研究中并未被考虑。使用一个考虑应力分布的模型，我们证明了能够在8%的误差范围内预测磨损体积。
