Exploring Deformation Mechanisms in Metallic Nanostructures Under Extreme Conditions of Temperature and Strain Rate

探索极端温度和应变率条件下金属纳米结构的变形机制

• 批准号: 1710736
• 负责人: Vijay Gupta
• 金额: $ 50万
• 依托单位: University of California-Los Angeles
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2017
• 资助国家: 美国
• 起止时间: 2017-09-01 至 2021-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1710736&HistoricalAwards=false
• 关键词: Exploring; Deformation; Mechanisms; Metallic; Nanostructures; Exploring; Deformation; Mechanisms; Metallic; Nanostructures

Non-Technical Description:Understanding the mechanical behavior of nano-crystalline metallic solids under extreme conditions of pressure and low temperatures is of great interest to engineering applications involving fusion reactors (for alternative energy), blast loadings and armors (national defense), and asteroid impacts (progress of science), among others. Under such loading a typical engineering material, notably a metal, fails in a brittle glass-like manner even though at ambient conditions it fails in a plastic fashion by absorbing substantial energy. The mechanical behavior of metals is dependent upon the size of the grains that collectively form its structure. By simulating individual grains by isolated nanopillars we will study if these pillars (and eventually individual grains) will deform in a ductile fashion even when they are subjected to aforesaid extreme conditions. If they retain the same ductility as under ambient conditions then this research would have taken the first major step to develop new metallic materials that could revolutionize the design of energy-absorbing blast resistant civil, nuclear, and defense structures, including personal protective equipment (helmet and body armors) for reducing traumatic brain injuries. This research should also lead to fundamental scientific advances in the area of high energy materials physics. The work proposed here is a true collaboration between material scientists employing advanced nano-fabrication and microscopy techniques; physicists using state of the art multi-scale modeling strategies that encompass basic principles which govern the inter-atomic structures and forces; and mechanical engineers employing the most sophisticated optics and experimental techniques for characterizing the mechanical behavior of engineering solids. As such, it provides excellent training for graduate students and undergraduates in the area of interdisciplinary science and technology. As these students go into the work force, they will be more able than their peers to cross boundaries and combine basic science and high level engineering. To bring the research ideas and results more broadly to the community, graduate students funded under this grant will also participate in the High School Summer Research Program at UCLA. This project will thus support the societal needs of encouraging and training young talents into the fields of science and engineering. Technical Description: This project will develop understanding the mechanical behavior of nano-structured metallic solids under extreme conditions of pressure, high rates of loading (blasts and explosions), and low temperature (below freezing). The above goal will be accomplished by carrying out a series of novel experiments, backed by multiscale modeling and transmission electron microscopy (TEM) analysis, by loading TEM-ready single crystal nanopillar samples of fcc (Cu) and bcc (Mo) metals of varying lengths (50 nm to 100 nm) and aspect ratios (50 nm to 100 nm in diameter) by laser-generated stress waves of sub-nanosecond rise times, under extreme conditions of stress (greater than 20 GPa), strain rate (higher than 108s-1), and temperature (cryogenic). A new method is proposed to load the nanopillars directly under uniform tension. This should eliminate the lattice friction and local pressure effects present under compression. When combined with cryogenic testing, loading under uniform tension should substantially increase the internal stress in the material. This should result in newer dislocation nucleation and mobility mechanisms and provide further insights into the present dynamic performance limits of these metals. Because of very high internal stress, this study is likely to provide the first ever experimental evidence for dislocation-free plasticity in shocked solids. To bring the research ideas and results more broadly to the community, graduate students funded under this grant will also participate in the High School Summer Research Program at UCLA. This project will thus support the societal needs of encouraging and training young talents into the fields of science and engineering.

非技术描述：在极端的压力和低温条件下，了解纳米晶体金属固体的机械行为对涉及融合反应堆（用于替代能源），爆炸载荷和装甲（国防）以及小行星影响（科学进步）的工程应用非常感兴趣。 在这种装载典型的工程材料（特别是金属）下，即使在环境条件下，它通过吸收大量能量而以塑料方式失败，但以脆性的方式失败。金属的机械行为取决于谷物的大小共同形成其结构。通过模拟单个晶粒，我们将研究这些支柱（以及最终的单个晶粒）是否会以延展性方式变形，即使它们遭受上述极端条件。 如果他们在环境条件下保留相同的延展性，那么这项研究将迈出第一步，开发新的金属材料，这些材料可能会彻底改变能源吸收的抗爆炸性抗爆炸，核和防御结构，包括个人保护设备（头盔和身体装甲），以减少创伤性脑损伤。这项研究还应导致高能材料物理学领域的基本科学进步。 这里提出的工作是采用先进的纳米制作和显微镜技术的物质科学家之间的真正合作。物理学家使用艺术状态多尺度建模策略，这些策略包括管理原子间结构和力的基本原理；以及使用最复杂的光学和实验技术来表征工程固体机械行为的机械工程师。 因此，它为跨学科科学和技术领域的研究生和本科生提供了出色的培训。 随着这些学生进入劳动力，他们将比同行跨越边界并结合基础科学和高级工程的能力。为了将研究思想和结果更广泛地带给社区，根据这笔赠款资助的研究生也将参加UCLA的高中夏季研究计划。因此，该项目将支持鼓励和培训年轻才能进入科学和工程领域的社会需求。 技术描述：该项目将在极端的压力，高负载率（爆炸和爆炸）和低温（低于冰点）的极端条件下，了解纳米结构金属固体的机械行为。 The above goal will be accomplished by carrying out a series of novel experiments, backed by multiscale modeling and transmission electron microscopy (TEM) analysis, by loading TEM-ready single crystal nanopillar samples of fcc (Cu) and bcc (Mo) metals of varying lengths (50 nm to 100 nm) and aspect ratios (50 nm to 100 nm in diameter) by laser-generated stress waves of在压力的极端条件下（大于20 GPA），应变率（高于108S-1）和温度（低温），亚纳秒升高时间。提出了一种新方法，将纳米柱直接在均匀张力下加载。 这应该消除压缩下存在的晶格摩擦和局部压力效应。 当与低温测试结合使用时，在均匀张力下的负载应大大增加材料中的内部应力。 这应该导致较新的位错成核和迁移率机制，并为这些金属的当前动态性能限制提供进一步的见解。 由于内部压力很高，这项研究可能会提供有史以来第一个实验证据，证明震惊的固体中无位错可塑性。为了将研究思想和结果更广泛地带给社区，根据这笔赠款资助的研究生也将参加UCLA的高中夏季研究计划。因此，该项目将支持鼓励和培训年轻才能进入科学和工程领域的社会需求。