Simple thermal actuator using R-phase transformation of Nitinol

Jayagopal Uchil; Kumara K. Ganesh; K.K. Mahesh

doi:10.1117/12.474680

15 July 2002 Simple thermal actuator using R-phase transformation of Nitinol

Jayagopal Uchil, Kumara K. Ganesh, K.K. Mahesh

Proceedings Volume 4701, Smart Structures and Materials 2002: Smart Structures and Integrated Systems; (2002) https://doi.org/10.1117/12.474680
Event: SPIE's 9th Annual International Symposium on Smart Structures and Materials, 2002, San Diego, California, United States

Abstract

R<-->A phase transformation in NiTi alloy is associated with a very small recoverable strain of the order of 0.5% compared to that of 6-8% recoverable strain of M<-->A transformation. The stability of R<-->A transformation against large number of thermal cycles is an attractive feature for an application of SMA. A spring of NiTi is designed and fabricated, using 40% prior cold worked nitinol wire of dia 1mm, with appropriate heat-treatment such that martensitic transformation takes place through two stage A-->R-->M. The transformation behaviors of this wire are studied using DSC and electrical resistivity measurements. Further, the spring has been subjected to thermo-mechanical treatment for getting a two-way memory, viz:, while heating the spring gets contracted and while cooling it gets elongated. This spring has been used as an thermal actuator and temperature variation is confined between 50-65 degree(s)C to utilize only R<-->A transformation. Linear stroke of 4cm by the spring is used to rotate a platform carrying a load of 2 kg. The efficiency and reliability of the spring is tested over a million thermal cycles.

Citation Download Citation

Jayagopal Uchil, Kumara K. Ganesh, and K.K. Mahesh "Simple thermal actuator using R-phase transformation of Nitinol", Proc. SPIE 4701, Smart Structures and Materials 2002: Smart Structures and Integrated Systems, (15 July 2002); https://doi.org/10.1117/12.474680

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