Dresden 2009 – wissenschaftliches Programm

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MM: Fachverband Metall- und Materialphysik

MM 4: Mechanical Properties II

MM 4.4: Vortrag

Montag, 23. März 2009, 12:30–12:45, IFW B

Discrete dislocation dynamics study of the influence of boundary conditions in micro-samples — •Jochen Senger¹, Daniel Weygand¹, Oliver Kraft^1,2, and Peter Gumbsch^1,3 — ¹IZBS, Universität Karlsruhe (TH) — ²IMF II, Forschungszentrum Karlsruhe — ³IWM, Fraunhofer Institut für Werkstoffmechanik, Freiburg

Ongoing miniaturization in technical devices demands a better understanding of mechanical properties of metallic structures in micro-meter range. Compression and tension tests on single crystalline samples revealed a size-dependency of flow stress. With decreasing pillar diameter an increasing average flow stress and an increasing standard deviation. Experimental uncertainties in the control of the deformation, like misalignment between sample and loading device can occur, leading to more complex stress states than desired, e.g. superimposed torsion or bending moments. Three dimensional discrete dislocation dynamics simulations are performed to explore the effect of superimposed torsion moments on tensile experiments. Samples with variable diameters and aspect ratio are also loaded with uniaxial tensile stresses and different boundary conditions, different allowed displacements of the top surface of the micro pillars. Identical initial dislocation structure for different loading conditions shows clearly the impact of the boundary conditions on the observed plastic behavior and internal dislocation micro structure. Source activation and active glide planes are influenced by boundary conditions as torsion moments activate other sources than tensile stresses.