Thermomechanical behavior of shape memory alloys

Dirk Helm; Peter Haupt

doi:10.1117/12.432769

11 July 2001 Thermomechanical behavior of shape memory alloys

Dirk Helm, Peter Haupt

Proceedings Volume 4333, Smart Structures and Materials 2001: Active Materials: Behavior and Mechanics; (2001) https://doi.org/10.1117/12.432769
Event: SPIE's 8th Annual International Symposium on Smart Structures and Materials, 2001, Newport Beach, CA, United States

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.

Citation Download Citation

Dirk Helm and Peter Haupt "Thermomechanical behavior of shape memory alloys", Proc. SPIE 4333, Smart Structures and Materials 2001: Active Materials: Behavior and Mechanics, (11 July 2001); https://doi.org/10.1117/12.432769

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