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Proceedings Paper

SMA single-crystal experiments and micromechanical modeling for complex thermomechanical loading
Author(s): Xiujie Gao; L. Catherine Brinson
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Paper Abstract

A simplified multivariant model for SMA single crystals is developed. Although the new model is a simplified version, removing explicit interaction energy calculations, it considers certain aspects of martensite transformation much better. Most significantly, martensite variants tend to rapidly form large plates most of which have an invariant plane interface with the austenite and/or reach the grain boundary. Hence the formulation of the previous Multivariant model in which every variant group is embedded in the austenite phase together with numerous other inclusions is inaccurate. In the simplified model, the energy contributed by the incompatibility of inclusion to the matrix is neglected. The prediction by the new model for different uniaxial tension directions on a single CuAlNi crystal agrees excellently with the experimental results. Furthermore, the counter-intuitive results for a polycrystalline CuZnAl SMA under triaxial loading are also well captured by the simplified model. Experimental result considering in situ loading in the MTS loading frame and SEM are shown illustrating the invariant plane in a single (gamma) '1 CuAlNi crystal under uniaxial loading. These results also necessitate further microstructure mapping for phase transition and detwinning and/or reorientation of correspondence variants in SMA with an internal twinned structures.

Paper Details

Date Published: 14 June 2000
PDF: 8 pages
Proc. SPIE 3992, Smart Structures and Materials 2000: Active Materials: Behavior and Mechanics, (14 June 2000); doi: 10.1117/12.388235
Show Author Affiliations
Xiujie Gao, Northwestern Univ. (United States)
L. Catherine Brinson, Northwestern Univ. (United States)

Published in SPIE Proceedings Vol. 3992:
Smart Structures and Materials 2000: Active Materials: Behavior and Mechanics
Christopher S. Lynch, Editor(s)

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