Homogeneous Dislocation Nucleation

均质位错成核

• 批准号: 1100245
• 负责人: Craig Maloney
• 金额: $ 30万
• 依托单位: Carnegie-Mellon University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2011
• 资助国家: 美国
• 起止时间: 2011-09-01 至 2014-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1100245&HistoricalAwards=false
• 关键词: Homogeneous; Dislocation; Nucleation

This work will utilize meso-scale analysis techniques to study indentation driven nucleation of dislocations in perfect crystals. In particular, the linear mechanical response of mesoscale regions, intermediate between the atomic scale and full system size, will be probed in order to search for embryonic defects. Atomistic computer simulations will be performed using classical empirical potentials to study the process in a perfect thin-film under a smooth, nanometer-scale, indenter. Furthermore, the nucleation phenomenon will be studied within a continuum framework, field dislocation mechanics (FDM). Direct comparisons will be made with in-situ electron microscopy imaging during indentation of single-crystal Al. The ultimate goal is to construct a simple analytical framework which would be able to predict thermal activation barriers governing nucleation given a few simple material parameters and geometrical loading conditions as inputs.The current state-of-the-art for predicting plastic deformation in ductile metals remains largely empirical and phenomenological. A "first principles," bottom-up, quantitative understanding of plasticity would allow for the design of materials with optimal mechanical properties such as increased strength and toughness. The work will also involve secondary education outreach co-ordinated through the Pittsburgh Supercomputing Center and targeted at under-represented populations in the urban core of Pittsburgh.

这项工作将利用细观分析技术来研究压痕驱动的完美晶体中位错的形核。特别是，将探索介于原子尺度和整个系统尺寸之间的中尺度区域的线性机械响应，以寻找胚胎缺陷。原子计算机模拟将使用经典的经验势来研究在光滑的纳米尺度的压头下的完美薄膜的过程。此外，形核现象将在连续介质框架内进行研究，即场位错力学。在单晶Al的压痕过程中，将直接与原位电子显微镜成像进行比较。最终目标是构建一个简单的分析框架，能够在给定一些简单的材料参数和几何加载条件的情况下预测控制形核的热激活势垒。目前预测延性金属塑性变形的最新技术仍然主要是经验和现象学的。对塑性的“第一原理”、自下而上的定量理解将允许设计出具有最佳机械性能的材料，如增强的强度和韧性。这项工作还将涉及通过匹兹堡超级计算中心协调的中学教育推广，目标是匹兹堡市中心代表性不足的人口。