Berlin 2012 – wissenschaftliches Programm
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MA: Fachverband Magnetismus
MA 45: Joint Session "Magnetic Shape Memory Alloys II" (jointly with DS, MM)
MA 45.1: Vortrag
Donnerstag, 29. März 2012, 15:00–15:15, H 0112
Stress accomodation in polytwinned NiTi nanograins studied with the phase-field method — •Christian Mennerich1, Frank Wendler1, Marcus Jainta1, Anna Weißhaar1, and Britta Nestler1,2 — 1Karlsruhe University of Applied Sciences — 2Karlsruhe Institute of Technology
During the martensitic transformation in NiTi shape memory alloys, grains of a critical radius below about 50 nm do not transform into martensite. A multi-phase field model of Allen-Cahn type is used to analyse the accomodation of a spherical nanograin inclusion embedded in the austenite phase at room temperature. The model is based on a Helmholtz free energy density formulation and includes elastic and eigenstrain energy contributions. The model is implemented using finite differences, assuming staggered grids for the components of the elastic displacements. We present the techniques used to describe the time-spatial evolution of the system oppose this to the simulation of a mechanical equilibrium. The model is successfully applied to Eshelby's inclusion problem to verify the correctness of the implementation. With this model, we study the stress accomodation of polytwinned spherical NiTi nanograins that are embedded in an austenite matrix. The results are compared to analytical solutions and numerical results from the literature.