Loading Metal Nanostructures Under Extreme Conditions Using Stress Waves with Rarefaction Shock Profiles

这项研究项目结合了实验和多尺度建模工作，以研究在极高的应力和应变率下金属中发生的新的变形机制。在这项研究中，纳米结构的样品将受到亚纳秒上升时间的激光产生的应力波。结果，这种材料在1纳秒内经历了50千兆帕斯卡或更高的应力。这种材料对这种动态条件的反应以前还没有详细探讨过。激光冲击实验将结合相同样品变形前后的电子显微镜表征和多尺度建模。这种方法使得演化的结构与压力和应变率的实验参数之间能够直接关联。此外，样本几何形状可用于建模，从而允许直接比较。这些研究将为实验观察和/或模拟预测的新变形机制建立科学基础，并提供对极端环境下材料稳定性的原子尺度的理解。这项工作应该有助于替代能源系统和先进装甲的设计。先进的纳米制造和显微镜、复杂的光学和机械测试以及最先进的建模策略相结合，为研究生和本科生提供了出色的跨学科培训。为了提高对研究理念的认识：将为洛杉矶联合学区的高中生提供研究机会；研究成果将被纳入工程课程；将鼓励代表不足的群体和本科生参与研究活动。

This research project combines experimental and multi-scale modeling efforts to investigate novel deformation mechanisms occurring in metals during extremely high rates of stress and strain. In this study, nanostructured samples will be subjected to laser-generated stress waves of sub-nanosecond rise times. As a result, the material experiences 50 GigaPascals or higher stresses within 1 nanosecond. The material's response to such dynamic conditions has not been explored in detail before. The laser shock experiments will be combined with electron microscopic characterization of the same samples before and after deformation and multi-scale modeling. This approach enables direct correlation between the evolved structures and experimental parameters of pressure and strain rate. Additionally, the sample geometries are amenable to modeling and thereby allowing for a direct comparison. These studies will establish scientific underpinning for the experimentally-observed and/or simulation-predicted new deformation mechanisms and provide an atomic-scale understanding of the material stability in extreme environments. The work should help in the design of alternate energy systems and advanced armors. The combination of advanced nanofabrication and microscopy, sophisticated optics and mechanical testing, and state-of-the-art modeling strategies provides excellent interdisciplinary training for graduate students and undergraduates. To promote awareness of the research ideas: the Los Angeles Unified School District high-school students will be provided with research opportunities; research results will be integrated into the engineering curriculum; and, underrepresented groups and undergraduates will be encouraged to participate in the research activities.