Mark Tschopp's blog

Multiple PhD positions are available for the fall 2012/winter 2013 semesters in microstructure-mechanics relationships for structural materials at high temperatures in the Center for Advanced Vehicular Systems (http://www.cavs.msstate.edu) at Mississippi State University.  The project is funded through Air Force Office for Scientific Research (AFOSR) and will involve multiscale materials characterization, in situ SEM experiments, and high temperature mechanical testing for turbine blade structural materials (nickel-based superalloys). 

Abstract. This letter addresses the dependence of homogeneous dislocation nucleation on the crystallographic orientation of pure copper under uniaxial tension and compression.  Molecular dynamics simulation results with an embedded-atom method potential show that the stress required for homogeneous dislocation nucleation is highly dependent on the crystallographic orientation and the uniaxial loading conditions; certain orientations require a higher stress in compression (e.g., <110> and <111>) and other orientations require a higher stress in tension (<100>).  Furthermore, the resolved shear stress in the slip direction is unable to completely capture the dependence of homogeneous dislocation nucleation on crystal orientation and uniaxial loading conditions.