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David P. Pope Distinguished Lecture: “Supersonic Collisions of Microparticles on Metal: In-Situ Studies at the Nanosecond and Micrometer Scales”
November 7 at 10:30 AM - 12:00 PM
There are many situations in which small particles impact metals at high speeds, even above the speed of sound. Sometimes these are unintentional (as for foreign object damage or micrometeorite strikes), and sometimes they occur by design (as for surface treatment processes like abrasive spray, peening, or spray coatings). The fundamental physics behind supersonic impacts, however, remain mysterious; the impacts are extremely fast and involve microscopic particles, so that they are challenging to resolve. This talk will review a new line of research aimed at understanding the unit process of particle impacts at velocities into the supersonic range—we study individual ~5-50 µm particles and record their approach and impact with a substrate using an all-optical single-particle test method with nanosecond time resolution. For hard particles, this method leads to quantitative measures of plasticity at extreme rates (>107 s -1). In this range, conventional plasticity gives way to ballistic dislocation motion, with counterintuitive “anti-thermal” behavior in which hotter metals are stronger. For metallic particles, our approach quantitatively reveals the changes in plasticity that occur as particles approach the threshold velocity for bonding, as well as other deleterious transitions such as impact-induced melting and erosion.
Christopher A. Schuh
Dean, Robert R. McCormick School of Engineering and Applied Science John G. Searle Professor of Materials Science and Engineering, Northwestern University
Christopher A. Schuh is the dean of the Robert R. McCormick School of Engineering and Applied Sciences at Northwestern University where he holds the title of John G. Searle Professor of Materials Science and Engineering.
Schuh, who began his tenure as dean of Northwestern Engineering on August 1, 2023, was previously POSCO Professor of Materials Science and Engineering at the Massachusetts Institute of Technology (MIT), where he served as Head of the Department of Materials Science and Engineering from 2011 to 2020. As Department Head, Schuh oversaw the development and implementation of a sweeping strategic plan resulting in growth and increased diversity among faculty ranks, an increase in research expenditures, an expansion of the department’s space profile, the completion of successful fundraising campaigns, endowed fellowship support for all incoming graduate students, new programming in entrepreneurship and innovation, and the roll out of online materials science courses offered to learners around the world.
Prior to joining MIT in 2002, Schuh held the Ernest O. Lawrence postdoctoral fellowship at Lawrence Livermore National Laboratory.
Schuh’s research is focused on structural materials including metals and ceramics, in which he seeks to control disorder in material microstructures for the purpose of optimizing mechanical properties. His research group uses experiments, analytical theory, and computer simulations to explore the processing-structure-property relationships in structural metals and materials. His more than 250 research articles have been published in academic journals such as Physical Review Letters, Science, and Acta Materialia, where he also serves as coordinating editor.