Berlin 2008 – wissenschaftliches Programm
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SYMS: Symposium Modern developments in multiphysics materials simulations
SYMS 1: Modern developments in multiphysics materials simulations I
SYMS 1.2: Hauptvortrag
Donnerstag, 28. Februar 2008, 14:30–15:00, A 151
Modelling Fracture Processes: Macroscopic Consequences of Atomistic Details — P. Gumbsch1,2, J.R. Kermode3, T. Albaret4, D. Sherman5, N. Bernstein6, M.C. Payne3, G. Csányi7, and •A. De Vita8 — 1IZBS, Universität Karlsruhe (TH), 76131 Karlsruhe, Germany — 2Fraunhofer-Institut für Werkstoffmechanik IWM, 79108 Freiburg, Germany — 3Cavendish Laboratory, Cambridge, CB3 0HE, United Kingdom — 4Université Claude Bernard, Lyon 1, France — 5Technion-Israel Institute of Technology, Haifa, 32000, Israel — 6Naval Research Laboratory, Washington, DC 20375-5343, USA — 7Department of Engineering, Cambridge, CB2 1PZ, United Kingdom — 8King’s College London, Strand, London WC2R 2LS, United Kingdom
The catastrophic failure of a brittle material is a complex, multiscale process. The applied stress at the macroscopic scale is concentrated by the sharp geometry of the crack tip. However, the way the solid fails in response to the stress concentration is determined by subtle lattice trapping and propagation instability effects which are controlled by atomic-scale chemical processes. We have investigated stability of cracks and dynamic, low speed, propagation instabilities in silicon using quantum mechanical hybrid multi-scale modelling and single-crystal fracture experiments. Our simulations reveal a tip reconstruction mechanism for a crack propagating on the (111) cleavage plane, causing a low speed instability which we observe experimentally. Conversely, propagation on the (110) plane is only stable up to a maximum speed, above which dynamical processes deflect the crack onto (111) planes as observed in experiments. So it looks as if cracks in silicon can "sink" and "stumble" as they propagate.