Speaker: Dr. Brad L. Boyce
Staff Scientist, CINT
Sandia National Laboratories
Date: 19th August 2023
Venue: Online
Abstract:
In-situ TEM high-cycle fatigue experiments on electron transparent thin films of nano-crystalline Ni and Cu have revealed not only microstructural-sensitive crack propagation, but also unexpected microstructural-scale crack healing. Based on the experimental observations, atomistic modeling, and continuum-scale microstructural modeling, the mechanism appears to be crack flank cold welding facilitated by local compressive microstructural stresses and/or grain boundary migration. While these observations are specific to pure nano-crystalline metal thin films under a high-vacuum environment, there are potentially much broader ramifications. The existing observations can be used to help rationalize suppressed fatigue crack propagation rates in vacuum, subsurface, or under contact-inducing mixed-mode stresses; and even the precipitous decline in propagation rates near the fatigue threshold.
Bio-data of speaker:
Dr. Boyce is a Distinguished Member of the Technical Staff at Sandia National Laboratories. Dr. Boyce received the B.S. degree from Michigan Tech in Metallurgical Engineering and the M.S. and Ph.D. degrees from the University of California at Berkeley. Dr. Boyce joined the technical staff at Sandia in 2001 where his research interests lie in micro-mechanisms of deformation and failure. He has published over 160 peer reviewed articles on topics such as microsystems reliability, nano-indentation, fracture in structural alloys, weld metallurgy, and fatigue mechanisms. Dr. Boyce is a recipient of the Hertz fellowship and the J. Keith Brimacombe Medal. He is also currently the president of TMS, The Minerals, Metals, and Materials Society.
Sandia National Laboratories is a multimission laboratory managed and operated by National Technology and Engineering Solutions of Sandia, LLC., a wholly owned subsidiary of Honeywell International, Inc., for the U.S. Department of Energy’s National Nuclear Security Administration under contract DE-NA-0003525
Organized by:
InSIS and Center for Structural Integrity of Safety Critical Systems, IIT Madras
