Continuum modeling and experiments for phase transitioning materials: from metastable steels to rate stiffening soft polymers
Prof. Vikas Srivastava
Tuesday, March 28, 2023
GTMI Building, Room Auditorium
Coupled mechanics driven phase transitions are critical for a wide range of materials ranging from corrosion resistant alloys to impact resistant structures. I will discuss our theoretical framework and continuum-scale finite deformation models for two distinct materials that show phase/state transformation. I will first present our fully coupled thermo-mechanical finite deformation model for phase transitioning austenitic steels for room to cryogenic temperatures. Stainless steels like 316L are metastable and show coupled temperature and plastic strain-driven transformation from FCC austenite to BCC martensite below ambient temperatures. The mechanical properties of such metastable austenitic steels make them desirable for applications ranging from automobiles to liquefied natural gas transport. Our coupled model and its simulation capability allow accurate modeling and prediction of metastable steels that have undergone a variety of thermo-mechanical forming histories. Next, I will present a theoretical framework and a constitutive model to describe the rate-dependent stiffening and material state transformation response of soft entangled polymers that can shield structures from high-velocity collisions, projectile impact, and explosion shock loads. These entangled soft polymers change from viscous-fluid-like to rubbery and glassy-solid states during high-rate deformations due to reversible dynamic crosslinks. We have experimentally characterized the nonlinear large deformation response of a soft polymer over a strain rate range of 10^-4 to 10^3 /s. The polymer stiffness changes by 5 orders of magnitudes over this strain rate range. We have developed a physics motivated continuum model that can predict the large deformation highly rate-dependent response of such polymers and provides insight into dynamic reversible crosslinking mechanisms. I will end the talk with a brief note about our recent work on neural networks for structural mechanics problems.
Dr. Srivastava is the Howard M. Reisman Assistant Professor of Engineering at Brown University. Dr. Srivastava received his Ph.D. in Mechanical Engineering from M.I.T. in 2010. Before this, he earned his M.S. in Mechanical Engineering and Applied Mechanics from the University of Rhode Island and his B.Tech. in Mechanical Engineering from the Indian Institute of Technology, Kanpur. Following his Ph.D., he worked at ExxonMobil Research organizations in various roles, including Senior Technical Professional Advisor in Mechanics, Mechanics and Marine Team Lead, and Worldwide Deepwater Drilling Coordinator. Dr. Srivastava joined Brown University in the fall of 2018. Dr. Srivastavaâ€™s research focuses on developing and applying continuum-scale solid mechanics theories, models, and experiments for engineering materials, structures, and biomedical systems.