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Proceedings Paper

Thermomechanical behavior of shape memory alloys
Author(s): Dirk Helm; Peter Haupt
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Paper Abstract

Tension and torsion as well as combined tension-torsion tests on NiTi Tubes are presented in this article. Two different specimens are used in the experiments: one is austenitic and the other is martensitic at room temperature. The experiments are performed at nearly isothermal conditions. However, non-isothermal effects occur as well because of the self-heating of the material during the phase transitions and the detwinning of the martensite. These effects can be excluded applying very small deformation rates. In contrast to this, the influence of the self- heating on the material behavior is investigated in other experiments, where temperature fields are measured by means of infrared thermography. This allows detailed observations of the temperature field on the surface of the specimen and leads to additional insight into the thermomechanical behavior of shape memory alloys. In simple tension and pure torsion experiments the various effects of the material behavior can be decoupled. In particular, relaxation and creep processes are observed as a result of self-heating, but also as a consequence of the viscosity of the material. The combined tension-torsion experiments make it possible to analyze coupling effects of the biaxial behavior. In this context, a proportional and non-proportional deformation path is carried out.

Paper Details

Date Published: 11 July 2001
PDF: 12 pages
Proc. SPIE 4333, Smart Structures and Materials 2001: Active Materials: Behavior and Mechanics, (11 July 2001); doi: 10.1117/12.432769
Show Author Affiliations
Dirk Helm, Univ. Gesamthochschule Kassel (Germany)
Peter Haupt, Univ. Gesamthochschule Kassel (Germany)

Published in SPIE Proceedings Vol. 4333:
Smart Structures and Materials 2001: Active Materials: Behavior and Mechanics
Christopher S. Lynch, Editor(s)

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