Prof. Kyung-Suk Kim
Hybrid Analysis of Nanostructural Evolution Near FCC Metal Surfaces and Interfaces
Abstract: In these days, high performance computing of atomistic simulations and nanoscale experiments are used to analyze nanostructural evolution of technologically viable material systems. However, critical understanding and control of such systems are often based on solid-mechanics of field characteristics. Therefore, hybridization of atomistic simulations, nanoscale experiments and field theoretical analysis is desirable for nano- and micro-mechanics of solids. Here, technically relevant examples of such hybridization are presented for nanostructural evolution of crystalline materials. One example is to analyze the evolution of surface stress and morphology of an FCC metal under low-energy noble-gas ion bombardment. In this example three new nano-plasticity mechanisms are uncovered. The first mechanism is the configurational motion of self-interstitials in subsonic scattering during ion bombardments. The second is the growth by gliding of prismatic dislocation loops in a highly stressed interstitial-rich zone. The third is the Burgers vector switching of a prismatic dislocation loop which leads to unstable eruption of adatom islands during ion bombardments of FCC metals. These mechanisms consistently clarify previously unexplainable experimental observations.
The other example is to study nanometer scale mechanical properties of grain boundaries in nanocrystalline FCC metals. For the study, interior and exterior nonlinear field projection methods have been developed to get field-projected subatomic-resolution traction distributions on various grain boundaries. The analyses show that the field projected traction produces periodic concentrated compression sites on the grain boundary, which act as crack trapping or dislocation nucleation sites. The field projection was also used to assess the nanometer scale failure processes of Cu grain boundaries doped with Pb. It was revealed that the Pb dopants prevented the emission of dislocations by grain boundary slip and embrittles the grain boundary.
Bio: Kyung-Suk Kim is currently a Professor of Engineering and a member of Solids and Structures Group at Brown University, directing the Nano and Micromechanics Laboratory. He received B.S. ('74) and M.S. ('76) degrees in Mechanical Engineering from Seoul National University, and Ph.D. ('80) degree in Solid Mechanics from Brown University. Then he was a faculty at the department of Theoretical and Applied Mechanics, University of Illinois, Urbana-Champaign ('80-'89). Since 1989 he has been Professor of Engineering at Brown University. He was also a visiting faculty at Harvard University ('87-'88 & ‘02), Cambridge University ('96), University of California, Santa Barbara ('97), and Distinguished Visiting Scientist at KIST (’08). He will receive Engineering Science Medal from the Society of Engineering Science in October, 2012.
Thursday, April 5, 2012
2145 Sheridan Road
9:00 AM - 10:00 AM