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Transformation-Induced Creep and Creep Recovery of Shape Memory Alloy
Department of Mechanical Engineering, Aichi Institute of Technology, 1247 Yachigusa, Yakusa-cho, Toyota 470-0392, Japan
Institute of Fundamental Technological Research, Polish Academy of Sciences, Pawinskiego 5B, Warsaw 02-106, Poland
* Author to whom correspondence should be addressed.
Received: 14 March 2012; in revised form: 9 May 2012 / Accepted: 11 May 2012 / Published: 22 May 2012
Abstract: If the shape memory alloy is subjected to the subloop loading under the stress-controlled condition, creep and creep recovery can appear based on the martensitic transformation. In the design of shape memory alloy elements, these deformation properties are important since the deflection of shape memory alloy elements can change under constant stress. The conditions for the progress of the martensitic transformation are discussed based on the kinetics of the martensitic transformation for the shape memory alloy. During loading under constant stress rate, temperature increases due to the stress-induced martensitic transformation. If stress is held constant during the martensitic transformation stage in the loading process, temperature decreases and the condition for the progress of the martensitic transformation is satisfied, resulting in the transformation-induced creep deformation. If stress is held constant during the reverse transformation stage in the unloading process, creep recovery appears due to the reverse transformation. The details for these thermomechanical properties are investigated experimentally for TiNi shape memory alloy, which is most widely used in practical applications. The volume fraction of the martensitic phase increases in proportion to an increase in creep strain.
Keywords: shape memory alloy; superelasticity; subloop; transformation band; creep; creep recovery; local deformation
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Takeda, K.; Tobushi, H.; Pieczyska, E.A. Transformation-Induced Creep and Creep Recovery of Shape Memory Alloy. Materials 2012, 5, 909-921.
Takeda K, Tobushi H, Pieczyska EA. Transformation-Induced Creep and Creep Recovery of Shape Memory Alloy. Materials. 2012; 5(5):909-921.
Takeda, Kohei; Tobushi, Hisaaki; Pieczyska, Elzbieta A. 2012. "Transformation-Induced Creep and Creep Recovery of Shape Memory Alloy." Materials 5, no. 5: 909-921.