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

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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.