Probability Density Function of Dislocation Free Path Length: Experimental Determination through GND Measurements

位错自由路径长度的概率密度函数：通过 GND 测量进行实验确定

• 批准号: 1310503
• 负责人: Jeffrey Kysar
• 金额: $ 37.03万
• 依托单位: Columbia University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2013
• 资助国家: 美国
• 起止时间: 2013-09-01 至 2017-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1310503&HistoricalAwards=false
• 关键词: Probability; Density; Function; Dislocation; Free

TECHNICAL SUMMARY:The dislocation mean free path length is a unifying concept in understanding plastic deformation across all pertinent length scales. Plasticity formulations that account directly for the motion of dislocations are stochastic processes because of the non-deterministic behavior of dislocations combined with the otherwise deterministic equations of solid mechanics. The mean free path length (MFPL) succeeds only partially in quantifying the dislocation free path length. It is also necessary to quantify the probability density function (PDF) of the dislocation free path length. The overall research objective of this proposal is to measure experimentally the MFPL and the PDF of dislocation free path length and relate them experimentally to the deformation quantity of plastic shear strain in individual crystallographic slip systems. The concept of making such measurements has existed for several decades, but the capabilities to perform such experiments have not existed until now. This program will develop and use the methods and procedures to make these experimental measurements. In that context, the overall educational objective of this proposal is to promulgate not only the results from the research objective, but also the underlying mechanics concepts as well as experimental methods and procedures necessary to perform research of this type to the larger research community.NON-TECHNICAL SUMMARY:The safety and reliability of the nation's infrastructure and transportation systems depend upon the ability of scientists and engineers to predict the behavior of materials, especially metals, used to build that infrastructure. Metals experience mechanical failure due to the presence of defects called dislocations that cause permanent deformation as they move throughout the interior of the metal. The goal of this project is to measure the average distance and the variation in distances that dislocations travel as metals are deformed permanently and to relate these quantities to the amount of deformation that occurred. These quantities are very important for the development and validation of theories that predict the failure of metals. New fundamental understanding of the motion of defects in metals has the potential to lead to better theories that predict the behavior of materials in the nation's infrastructure with greater fidelity. The main educational goal of this project is to introduce the novel concepts and methods necessary to make the measurements to engineers and scientists through technical articles as well as teaching seminars at scientific conferences. A Ph.D. student will be supported in this project, thus enhancing the nation's human resources.

技术摘要：位错平均自由路径长度是在所有相关长度范围内理解塑性变形的统一概念。直接解释位错运动的塑性公式是随机过程，因为位错的非确定性行为与固体力学的其他确定性方程相结合。平均自由光程长度(MFPL)在量化位错自由光程长度方面只取得了部分成功。还需要量化无位错路径长度的概率密度函数(PDF)。这一建议的总体研究目标是实验测量位错自由路径长度的MFPL和PDF，并将它们与各个晶体滑移系统中的塑性剪切应变的变形量进行实验关联。进行这种测量的概念已经存在了几十年，但进行这种实验的能力直到现在才存在。这个项目将开发和使用进行这些实验测量的方法和程序。在这种背景下，这项建议的总体教育目标不仅是公布研究目标的结果，还包括基本的力学概念以及进行此类研究所需的实验方法和程序。非技术摘要：国家基础设施和交通系统的安全和可靠性取决于科学家和工程师预测用于建造基础设施的材料，特别是金属的性能的能力。金属由于存在称为位错的缺陷而经历机械故障，当它们在金属内部移动时，这些缺陷会导致永久变形。这个项目的目标是测量金属永久变形时位错移动的平均距离和距离变化，并将这些量与发生的变形量联系起来。这些量对于发展和验证预测金属失效的理论是非常重要的。对金属中缺陷运动的新的基本理解有可能导致更好的理论，以更准确地预测国家基础设施中材料的行为。该项目的主要教育目标是通过科学会议上的技术文章和教学研讨会向工程师和科学家介绍进行测量所需的新概念和方法。一名博士生将在这个项目中得到支持，从而增强国家的人力资源。