3:00pm via Zoom: https://wse.zoom.us/j/348258728
“Mechanics of Granular Materials at “Micro” Length and Time Scales from in-situ X-ray Measurements”
Presented by Professor Ryan Hurley
Department of Mechanical Engineering, Johns Hopkins University
Granular materials are ubiquitous in nature and technology. They include the soils we build structures on, the raw materials we compress and sinter into a vast number of solid products, the foods we love (rice and coffee), and the powders we use in pharmaceuticals and beauty products. Despite their ubiquity, granular materials exhibit very complex behavior that eludes our mechanical models. They size-segregate during flow, exhibit complicated creep behavior when not flowing, demonstrate long-range correlated behavior when compressed, and dissipate an enormous amount of energy due to friction. How can a granular material containing particles that only interact mechanically with their contacting neighbors exhibit such complexity?
In this talk, I will first highlight some interesting behaviors of granular materials with both academic and real-world applications. I will then motivate a need to better experimentally understand granular material behavior: to study their internal structure and response to mechanical loading. I will then describe the portion of my research program that aims to quantitatively measure the behavior of granular materials down to a “microscopic” length scale (the scale of individual particles and their contacts with neighboring particles) and “microscopic” time scales (nanoseconds during dynamic impact). Central to this research program is the use of multiple in-situ X-ray techniques, including X-ray computed tomography (XRCT), 3D X-ray diffraction (3DXRD), and dynamic X-ray phase contrast imaging and radiography. I will describe how we use these techniques and analysis to study how opaque, 3D granular materials develop spatially-correlated inter-particle forces, dissipate energy due to slipping and fracturing, transport wave energy, and dynamically compress due to shock. I will discuss some of our exciting ongoing and future research directions.
Ryan Hurley is an Assistant Professor in the Department of Mechanical Engineering and a Fellow of the Hopkins Extreme Materials Institute, with a Secondary Appointment in the Department of Civil and Systems Engineering, at the Johns Hopkins University (JHU). He received his B.S. in Civil Engineering from the University of Maryland, College Park (2011) and his M.S. (2012) and Ph.D. (2015) in Applied Mechanics from the California Institute of Technology. From 2015 – 2017, Ryan was a postdoctoral researcher in the Computational Geosciences Group at Lawrence Livermore National Laboratory in Livermore, California and an Assistant Research Professor at JHU. He joined JHU full-time as an Assistant Professor in January 2018. He is the recipient of a 2017 Secretary’s Appreciation Award from the U.S. Department of Energy and a 2019 CAREER Award from the U.S. National Science Foundation. In his research, Ryan seeks to see, understand, and predict the mechanical behavior governing a variety of geologic, structural, and composite materials using advanced experimental and numerical techniques.