Measurement and mechanisms of elastic deformation in amorphous solids

非技术概述无定形固体是其中原子或分子不以规则重复模式排列的材料。普通的窗户玻璃和许多塑料都是非晶的，但也有一些更奇特的例子，如金属玻璃。我们感兴趣的是了解无定形材料的结构如何变化时，他们被放置在机械应力变形。在这个程序中，我们使用计算机模型来研究当材料变形时，无定形材料中的原子和分子是如何重新排列的。 将模型的结果与实验进行比较，在实验中，我们研究了X射线和中子在材料变形时如何被散射，提供了有关原子和分子结构如何演变的信息。一个目标是将这些散射技术发展成可靠的常规工具，用于测量变形，然后可以由对广泛应用感兴趣的研究人员使用，包括玻璃中的残余应力和复杂材料（如骨）的机械行为的研究。经过验证的工具，用于评估学生在核心本科材料结构课程中的学习情况。这些工具将分发给其他教师使用，并为如何为本科材料科学课程开发类似的评估工具提供模板，技术概述最近的实验和计算结果清楚地表明，名义上的弹性，无定形固体中的（可恢复的）变形比简单的键要复杂得多，用来描述结晶固体弹性变形的拉伸图。该计划的第一个目标是了解在无定形固体中使用金属玻璃和线性无定形均聚物作为模型系统的弹性变形的基本机制。这将使用分子动力学模拟进行研究，特别注意不均匀，非仿射原子和分子重排，现在被认为是负责名义上的弹性加载过程中观察到的几个不寻常的现象。第二个目标是将X射线和中子散射发展成为非晶态固体弹性应变定量、非破坏性测量的可靠工具。这将为研究人员提供一种强大的新能力，以探索具有非晶成分的各种复杂材料的力学行为。潜在的应用包括内部残余应力的调查，由于氧化物和聚合物玻璃加工和原位研究的聚合物基复合材料和硬生物材料，如bone.The主要的教育目标是开发严格的，有效的工具来评估学生学习的核心本科材料结构课程。这些工具将分发给其他教师使用，并为如何为本科材料科学课程和更广泛的工程课程开发类似的评估工具提供模板。

Non-technical summaryAmorphous solids are materials in which the atoms or molecules are not arranged in a regularly repeating pattern. Ordinary window glass and many plastics are amorphous, but there are more exotic examples such as metallic glasses. Our interest is in understanding how the structure of amorphous materials change when they are deformed by being placed under mechanical stress. In this program we use computer models to study how the atoms and molecules in an amorphous material rearrange themselves when the material is deformed. The results from the models are compared with experiments in which we examine how x-rays and neutrons are scattered by the material as it is deformed, providing information about the how the atomic and molecular structure evolves. One goal is to develop these scattering techniques into reliable routine tools for measuring the deformation which could then be used by researchers interested in a wide range of applications, including studies of residual stresses in glasses and the mechanical behavior of complex materials such as bone.The primary educational objective of this program is to develop rigorous, validated tools for assessing student learning in a core undergraduate Structure of Materials course. These tools will be disseminated for use by other instructors and provide a template for how to develop similar assessment instruments for undergraduate materials science courses, and engineering courses more generally.Technical summaryRecent experimental and computational results clearly demonstrate that nominally elastic (recoverable) deformation in amorphous solids is considerably more complex that the simple bond-stretching picture invoked in describing elastic deformation of crystalline solids. The first objective of this program is to understand fundamental mechanisms of elastic deformation in amorphous solids using metallic glasses and linear amorphous homopolymers as model systems. This will be investigated using molecular dynamics simulations, paying particular attention to inhomogeneous, non-affine atomic and molecular rearrangements now believed to be responsible for several unusual phenomena observed during nominally elastic loading. The second objective is develop x-ray and neutron scattering into reliable tools for quantitative, non-destructive measurement of elastic strains from non-crystalline solids. This will give researchers a powerful new ability to explore the mechanical behavior of a wide range of complex materials with amorphous constituents. Potential applications include investigation of internal residual stresses due to processing of oxide and polymer glasses and in situ studies of load transfer in polymer matrix composites and hard biological materials such as bone.The primary educational objective of this program is to develop rigorous, validated tools for assessing student learning in a core undergraduate Structure of Materials course. These tools will be disseminated for use by other instructors and provide a template for how to develop similar assessment instruments for undergraduate materials science courses, and engineering courses more generally.