Levich Institute Seminar – Tuesday, 10/25/2022

Tuesday, 10/25/2022
2:00 PM
Steinman Hall #1M-22 (Levich Institute Conference Room)

Professor Nathan Keim
Penn State University, Physics Department

“Revealing and Erasing History in a Soft Jammed Solid”

Zoom Link:  https://ccny.zoom.us/j/81411291039



When a disordered jammed solid is sheared for many cycles at constant strain amplitude, it can relax until the same particle rearrangements repeat in each cycle. I discuss two ways this simple form of mechanical annealing helps illuminate these materials’ complexity. First, experiments with a 2D colloidal solid show how annealing forms a memory of strain amplitude, and how disordered solids exemplify a generic behavior called return-point memory. This prompts the question of whether an annealed sample could instead be free of memories. Paradoxically, this can be done by storing as many memories as possible—which we can understand by measuring the population of rearranging regions within a sample. Second, I discuss another possible outcome of annealing: an orbit in which the period of particle motions is a multiple of the period of driving. Unlike return-point memory, this behavior can arise from frustrated interactions among the rearranging regions, and it suggests a way to reveal these elusive interactions in experiments.


B.S. in Physics, Haverford College, 2004
Ph.D. in Physics, University of Chicago, 2010
Postdoc at University of Pennsylvania, Mechanical Engineering & Applied Mechanics, 2011-2014
Assistant Professor of Physics, Cal Poly San Luis Obispo, 2014–2021
Associate Professor of Physics, Cal Poly San Luis Obispo, 2021
Associate Research Professor of Physics, Penn State, 2020–present

Memory phenomena in soft and glassy matter
Plasticity and yielding in amorphous solids
Liquid contact line dynamics
Rheometry of interfacial materials and freely suspended films
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