Academics Research Our Dept Resources Academics Undergraduate Programs Graduate Programs Course Descriptions Mission and Objectives Research Department Faculty & Staff Graduate Students Open Faculty Positions News & Announcements Events Resources Webmail Career Services Engineering Student Services Intranet Home > Our Department > All Events > Materials Modeling Across Scales: Applications to Stress-Corrosion of Metals and the Mechanics of Graphene    Materials Modeling Across Scales: Applications to Stress-Corrosion of Metals and the Mechanics of Graphene   By Dr. Ashwin Ramashbramaniam Research Associate in Applied and Computational Mathematics Princeton University   Fri, Feb 27, 2009 9:00 AM   Location: Lopata Hall Room 103   A comprehensive description of materials requires first an understanding of individual processes at multiple scales and thereafter an accurate and consistent coupling of these phenomena across scales. I present two examples from recent work on incorporating microscopic physics within higher scale models.  First, I discuss work on extending time scales within atomistic simulations using hydrogen embrittlement of iron as an example. Long-range diffusion of hydrogen within the crystal is modeled using a novel off-lattice, on-the-fly kinetic Monte Carlo approach. Diffusion barriers and rates are ascertained from the local environments of hydrogen atoms using a combination of density functional theory and empirical interatomic potentials. Examples of bulk diffusion over extended time scales in defective crystals are presented and shown to be in good agreement with theory. Ongoing work and remaining challenges for development of a multiscale model of stress-corrosion cracking are discussed. Next, I present work on the mechanics of graphene with a view to understanding experimental observations of rippling, scrolling, and twisting of nanoribbons. From a combination of atomistic and continuum modeling, edge stresses are shown to play a key role in intrinsic rippling of freestanding graphene sheets independent of any thermal effects. Based on elasticity theory, scaling laws are identified for the amplitude and penetration depth of edge ripples as a function of wavelength. These results underscore the importance of accounting for edge stresses in thermal theories and electronic structure calculations for freestanding graphene sheets and nanoribbons.     Mechanical, Aerospace & Structural Engineering, Washington University in St. Louis One Brookings Drive, Box 1185, St. Louis, Missouri 63130 Office Location: 305 Jolley Hall, Phone: (314) 935-6047, Fax: (314) 935-4014   Home |  Academics | Research | Department | Resources © 2009 | Did you find it?