It was recalled that a strain-gradient theory for crystal plasticity had recently been proposed in which the gradient effect originated from a defect energy that characterized the energy storage due to the presence of a net Burgers vector. Here, a number of different possibilities for this energy were considered. In particular, working within a simple 2-dimensional framework, the predictions of the theory were compared with the results of discrete-dislocation simulations of stress relaxation in thin films. The objective was to investigate which specific defect energies were capable of capturing the size-dependent response of such systems for different crystal orientations.

Effect of Defect Energy on Strain-Gradient Predictions of Confined Single-Crystal Plasticity. L.Nicola, E.Van der Giessen, M.E.Gurtin: Journal of the Mechanics and Physics of Solids, 2005, 53[6], 1280-94