Regensburg 2007 – wissenschaftliches Programm

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MM: Fachverband Metall- und Materialphysik

MM 14: SYM Micro- and Nanomechanics II

MM 14.5: Vortrag

Dienstag, 27. März 2007, 11:45–12:00, H16

Mechanical properties of micro bending-beams: a comparison between discrete dislocation dynamic simulations and experiments — •Christian Motz, Daniel Weygand, and Peter Gumbsch — IZBS, Universität Karlsruhe, D-76133 Karlsruhe

Due to size-effects the mechanical properties in small dimensions may be different from the macroscopic ones and the knowledge of the related mechanisms is essential for a successful design at these small length scales. In complex systems usually stress and strain gradients arises during mechanical loading, and therefore the influence of these gradients on the mechanical properties is important, too. To investigate this influence 3D discrete dislocation dynamic simulations and experiments were performed on micron-sized bending beams. For the simulations the beam thickness varied between 500 nm and 1500 nm with a thickness to length ratio of 1:3. The deformation behaviour was studied in dependence of beam thickness, initial dislocation density and crystal orientation. All configurations showed a pronounced size dependence, i.e. the resistance to plastic deformation increases with decreasing beam thickness, which seems to be mainly caused by a strong dislocation pile-up in the bending beam that is usually not found in the absence of stress gradients (e.g. in compression tests). A comparison with experimental results shows a good agreement in terms of deformation behaviour and possible dislocation structure. A simple analytical pile-up model is developed, which can reproduce the size effect quite well. Finally, the importance of special dislocation structures on the mechanical properties in small dimensions is discussed.