In small dimensions, the flow stress of metallic samples exhibited a size-dependence such that smaller was stronger, even in nominally strain gradient-free loading conditions. However, the role of the boundary conditions in miniaturised tension or compression tests on the mechanical response and dislocation structure has not been studied in detail. In simulations performed with a three-dimensional discrete dislocation dynamics tool, initial, well-defined dislocation microstructures were loaded in tension with different boundary conditions including superimposed torsion moments. The influence of the loading conditions on details of the evolving dislocation microstructure was investigated by using identical starting configuration. An additional torsion moment significantly influences the dislocation activity since forest-dislocations were generated, but size effect of the flow stress was found to be unchanged.

Evolution of Mechanical Response and Dislocation Microstructures in Small-Scale Specimens under Slightly Different Loading Conditions. J.Senger, D.Weygand, C.Motz, P.Gumbsch, O.Kraft: Philosophical Magazine, 2010, 90[5], 617-28