NiTiHf is a high temperature and high strength shape memory alloy with transformation temperatures above 100oC. A constitutive model based on Gibbs free energy is developed to predict the behavior of this material. Two different irrecoverable strains including transformation induced plastic strain (TRIP) and viscoplastic strain (VP) are considered when using high temperature shape memory alloys (HTSMAs). The first one happens during transformation at high levels of stress and the second one is related to the creep which is rate-dependent. The developed model is implemented for NiTiHf under uniaxial loading. Finite difference method is utilized to solve the proposed equations. The material parameters in the equations are calibrated from experimental data. Simulation results are captured to investigate the superelastic behavior of NiTiHf. The extracted results are compared with experimental tests of isobaric heating and cooling at different levels of stress and also superelastic tests at different levels of temperature. More results are generated to investigate the capability of the proposed model in the prediction of the irrecoverable strain after full transformation in HTSMAs.

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Published in Proceedings of SPIE, v. 10596, Behavior and Mechanics of Multifunctional Materials and Composites XII, article 1059613, p. 1-6.

© 2018 SPIE. One print or electronic copy may be made for personal use only. Systematic reproduction and distribution, duplication of any material in this paper for a fee or for commercial purposes, or modification of the content of the paper are prohibited.

Nazanin Farjam, Reza Mehrabi, Haluk Karaca, Reza Mirzaeifar, and Mohammad Elahinia, "Modeling of NiTiHf using finite difference method," Proc. SPIE 10596, Behavior and Mechanics of Multifunctional Materials and Composites XII, 1059613 (March 27, 2018). DOI: https://doi.org/10.1117/12.2300857

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