Predicting Changes in Structure and Properties During Wear in Metallic Systems

磨损一般定义为材料在滑动接触过程中的损耗或位移，是一个具有重要实际意义的工程课题。 维修过程中的材料损失可能导致部件性能降低，甚至导致设备的灾难性故障。 纳米结构金属，其中内部结构特征具有纳米范围的尺寸，由于其极高的硬度和强度，是用于耐磨涂层和工程部件的有前途的材料。 然而，赋予优异强度的独特纳米结构也以独特的方式累积磨损损伤。 该奖项支持对这种纳米结构金属材料的磨损和损坏进行系统研究。 该研究将机械工程与材料科学和物理学相结合，同时还利用了尖端的实验和计算技术。 特别感兴趣的是识别的影响的操作条件上的磨损损伤的积累。 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，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性研究，旨在揭示纳米晶金属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后续的力学响应。 分子动力学模拟将首先用来探讨如何磨料滑动驱动晶界迁移，晶粒生长，晶界松弛。 特别感兴趣的是应力场，局部原子应力分布和结构演化的连续预测之间的联系。合金化学和晶界能的影响也将被探讨。 这些模拟将用于指导磨损实验，并告知现场特定的结构表征，以研究近表面微观结构的演变作为晶粒尺寸，磨损周期，施加的载荷和滑动速度的函数。 这些数据将用于创建“结构演化图”，以提高该领域对纳米晶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.