There will be a mini-symposium entitled "Defects and Microstructure at the Nanoscale and Beyond," at the USNCCM-10 conference in Columbus, OH, July 16 -19, 2009.  This topic is of keen interest to the I-Mechanica community and we hope many of you will join us there. Our goal is to bring together researchers from the mechanics, materials, and physics communities to cross-fertilize research on defect-mediated processes in microstructural evolution, with a focus on both hard and soft materials. 

An EPSRC-funded PhD Studentship is available in the Mechanics of Materials Group, Department of Mechanical Engineering at Imperial College London in the general area of theoretical/computational solid mechanics. Funding comes in the form of an EPSRC award (DTA scheme), and as such there is much flexibility in the project scope. A few tentative possibilities are: discrete dislocation modeling of high-temperature creep in dispersion-strengthened superalloys, crack nucleation criteria for functionally graded materials, fracture and post-operative remodeling of trabecular bone (jointly with the biomechanics group).

This is a paper we recently published in JMPS on a study of the mechanical properties on thin films comparing experimental results with discrete dislocation simulations. It provides insight in the strengthening that occurs in thin metal films when surface or interface effects become important.

The abstract is below; the full paper can be downloaded from here

Abstract - Experimental measurements and computational results for the evolution of plastic deformation in freestanding thin films are compared. In the experiments, the stress–strain response of two sets of Cu films is determined in the plane-strain bulge test. One set of samples consists of electroplated Cu films, while the other set is sputter-deposited. Unpassivated films, films passivated on one side and films passivated on both sides are considered. The calculations are carried out within a two-dimensional plane strain framework with the dislocations modeled as line singularities in an isotropic elastic solid. The film is modeled by a unit cell consisting of eight grains, each of which has three slip systems. The film is initially free of dislocations which then nucleate from a specified distribution of Frank–Read sources. The grain boundaries and any film-passivation layer interfaces are taken to be impenetrable to dislocations. Both the experiments and the computations show: (i) a flow strength for the passivated films that is greater than for the unpassivated films and (ii) hysteresis and a Bauschinger effect that increases with increasing pre-strain for passivated films, while for unpassivated films hysteresis and a Bauschinger effect are small or absent. Furthermore, the experimental measurements and computational results for the 0.2% offset yield strength stress, and the evolution of hysteresis and of the Bauschinger effect are in good quantitative agreement.