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。使用过程中的材料损失可能会导致部件性能降低，甚至导致设备的灾难性故障。纳米结构金属的内部结构尺寸在纳米范围内，由于其极高的硬度和强度，有望成为耐磨涂层和工程部件的材料。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了磨损损伤。该奖项支持对此类纳米结构金属材料的磨损和损伤进行系统研究。这项研究将机械工程与材料科学和物理学结合起来，同时也利用了尖端实验和计算技术的组合。特别感兴趣的是确定运行条件对磨损损伤累积的影响。因此，该项目将通过设计更好的耐磨材料来延长产品寿命并限制磨损故障，从而使美国经济受益。此外，该奖项还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，以揭示纳米晶金属磨损过程中结构演变和损伤的机制，并了解这些变化如何影响后续的机械响应。分子动力学模拟将首先被用来探索磨料滑动如何驱动晶界迁移、晶界生长和晶界松弛。特别令人感兴趣的是应力场的连续预测、局部原子应力分布和结构演化之间的联系。并对合金化学和晶界能的影响进行了探讨。这些模拟将用于指导磨损实验和提供现场特定结构表征的信息，以便研究近表面微观结构随晶粒度、磨损周期、外加载荷和滑动速度的变化。这些数据将被用来创建“结构演化图”，以提高该领域对纳米晶体材料如何响应复杂变形条件的理解，并有助于未来抗损伤纳米结构材料的设计。这项研究还将量化近表面材料的机械性能如何随着磨损损伤的演变。

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.