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Investigation of the Propagation of Stress Wave in Nickel-Titanium Shape Memory Alloys

1
College of Architecture and Environment, Sichuan University, Chengdu 610065, China
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Laboratory of Computational Physics, Institute of Applied Physics and Computational Mathematics, Beijing 100088, China
3
Center for Applied Physics and Technology, Peking University, Beijing 100071, China
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Faculty of Materials and Energy, Southwest University, Chongqing 400715, China
*
Authors to whom correspondence should be addressed.
Materials 2018, 11(7), 1215; https://doi.org/10.3390/ma11071215
Received: 7 June 2018 / Revised: 10 July 2018 / Accepted: 11 July 2018 / Published: 15 July 2018
Based on irreversible thermodynamic theory, a new constitutive model incorporating two internal variables was proposed to investigate the phase transformation and plasticity behavior in nickel-titanium (NiTi) shape memory alloys (SMAs), by taking into account four deformation stages, namely austenite elastic phase, phase transition, martensitic elastic phase, and plastic phase. The model using the material point method (MPM) was implemented by the FORTRAN code to investigate the stress wave and its propagation in a NiTi rod. The results showed that its wave propagation exhibited martensitic and austenitic elastic wave, phase transition wave, and plastic wave. However, a double-wave structure including the martensitic and austenitic elastic wave and plastic wave occurred when the martensitic elastic wave reached the phase transformation wave. Thus, the reflection wave at a fixed boundary exhibited a different behavior compared with the elastic one, which was attributed to the phase transition during the process of reflection. It was found that the stress increment was proportional to the velocity of phase transition wave after the stress wave reflection. In addition, the influences of loading direction and strain rate on the wave propagation were examined as well. It was found that the phase transition wave velocity increased as the strain rate increased. The elastic wave velocity of martensite under compressive conditions was larger than that under tensile loading. In contrast, the plastic wave velocity under compression was less than that subjected to the tensile load. View Full-Text
Keywords: constitutive model; NiTi alloys; stress wave propagation; material point method constitutive model; NiTi alloys; stress wave propagation; material point method
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Cui, Y.; Zeng, X.; Chen, H.; Chen, J.; Wang, F. Investigation of the Propagation of Stress Wave in Nickel-Titanium Shape Memory Alloys. Materials 2018, 11, 1215.

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