Predicting Changes in Structure and Properties During Wear in Metallic Systems

磨损通常被定义为材料在滑动接触过程中的损失或位移，是一个具有重要实际意义的工程课题。在使用过程中材料的丢失会导致组件性能下降，甚至导致设备的灾难性故障。纳米结构金属具有纳米级的内部结构特征，由于其极高的硬度和强度，在耐磨涂层和工程部件方面具有很大的应用前景。然而，独特的纳米结构赋予了优异的强度，也以独特的方式积累磨损损伤。该奖项支持对这种纳米结构金属材料的磨损和损伤进行系统的研究。该研究将机械工程与材料科学和物理学相结合，同时也利用了尖端实验和计算技术的结合。特别感兴趣的是确定操作条件对磨损损伤积累的影响。因此，该项目将使美国经济受益，因为它允许设计更好的耐磨材料，延长产品使用寿命，减少磨损故障。此外，将为来自不同背景的学生创造教育和研究机会，扩大对科学研究的参与。该奖项支持一项创新研究，以揭示纳米晶金属在磨损过程中的结构演变和损伤机制，并了解这些变化如何影响随后的机械响应。分子动力学模拟将首先用于探索磨料滑动如何驱动晶界迁移、晶粒生长和晶界松弛。特别感兴趣的将是应力场的连续统预测、局部原子应力分布和结构演化之间的联系。本文还探讨了合金化学和晶界能的影响。这些模拟将用于指导磨损实验，并为特定地点的结构表征提供信息，以研究近表面微观结构随晶粒尺寸、磨损周期、施加载荷和滑动速度的变化。这些数据将用于创建“结构演化图”，以提高该领域对纳米晶体材料如何应对复杂变形条件的理解，并有助于未来设计抗损伤纳米结构材料。该研究还将量化近表面材料的机械性能如何随磨损损伤而变化。

Wear is generically defined as the loss or displacement of material during sliding contact, and is an engineering topic of great practical importance. Material loss during service can result in reduced component performance or even catastrophic failure of a device. Nanostructured metals, where internal structural features have dimensions in the nanometer range, are promising materials for wear-resistant coatings and engineering components because of their extremely high hardness and strength. However, the unique nanostructure that imparts excellent strength also accumulates wear damage in unique ways. This award supports a systematic investigation of wear loss and damage in such nanostructured metallic materials. The research combines mechanical engineering with materials science and physics, while also utilizing a combination of cutting-edge experimental and computational techniques. Of specific interest is the identification of the effect of operating conditions on the accumulation of wear damage. Therefore, this project will benefit the U.S. economy by allowing for the design of better wear-resistant materials that extend product lifetime and limit wear failures. In addition, educational and research opportunities will be created for students from diverse backgrounds, broadening participation in scientific research.This award supports an innovative study to reveal the mechanisms of structural evolution and damage during wear of nanocrystalline metals, and to understand how these changes affect subsequent mechanical response. Molecular dynamics simulations will first be used to explore how abrasive sliding drives grain boundary migration, grain growth, and grain boundary relaxation. Of specific interest will be the connection between continuum predictions of stress fields, local atomic stress distributions, and structural evolution. The effects of alloy chemistry and grain boundary energy will also be probed. These simulations will be used to guide wear experiments and inform site-specific structural characterization, in order to study the evolution of near-surface microstructure as a function of grain size, wear cycle, applied load, and sliding speed. This data will be used to create "structural evolution maps," to improve the field's understanding of how nanocrystalline materials respond to complex deformation conditions and help in the future design of damage-resistant nanostructured materials. The study will also quantify how the mechanical properties of the near-surface material evolve with wear damage.