Dresden 2009 – scientific programme
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MM: Fachverband Metall- und Materialphysik
MM 4: Mechanical Properties II
MM 4.1: Talk
Monday, March 23, 2009, 11:45–12:00, IFW B
Crystal plasticity finite element study on small scale plasticity of micropillars — •D. Ma1, D. Raabe1, F. Roters1, R. Maass2, and H. Van Swygenhoven2 — 1Max-Planck-Institut für Eisenforschung GmbH, Max-Planck-Strasse 1, 402 37, Düsseldorf, Germany — 2Paul Scherrer Institute, CH-5232 Villigen, Switzerland
Experimental studies on micro-compression testing on single crystals reveal that these samples are stronger than the respective bulk material. The onset of plasticity is hard to determine from the stress-strain curves, however, it can be associated with changes in in-situ taken Laue patterns. This method allows one to identify the true start of plastic yielding of such single crystals which is referred to as "Laue-yield". By applying this concept, recent experimental work discovered that the trend of smaller is stronger is considerably reduced (Van Swygenhoven et al., in press). In these experiments it has been observed that unexpected slip systems non-Schmid planes are activated prior to the geometrically predicted ones on Schmid planes. We use a crystal plasticity finite element method for investigating the details of the slip system activation under different boundary conditions, such as minor orientation and shape deviations of the crystals used, different contact conditions between sample and compression tools, and possible misalignments of the compression tools. In this study, we show how those boundary conditions influence the micro-compression test, the active slip system, and even the measured stresses. The results reveal that under certain small tool misalignments (ca. 2o) the activation of unexpected slip systems with small Schmid factors can be explained.