Timescale competition dictates thermo-mechanical responses of NiTi shape memory alloy bars

INTERNATIONAL JOURNAL OF SOLIDS AND STRUCTURES

卷:193

Article

Zhuo, Mingzhao^1,2 

[1] Hong Kong Univ Sci & Technol, Dept Mech & Aerosp Engn, Clear Water Bay, Hong Kong, Peoples R China

[2] Delft Univ Technol, Fac Civil Engn & Geosci, Delft, Netherlands

关键词: Thermo-mechanical coupling;    Shape memory alloy;    Phase transition;    Thermodynamic driving force;    Loading-rate effect;    Timescale ratio;   

DOI  :  10.1016/j.ijsolstr.2020.02.021

来源: Elsevier

【 摘 要 】

NiTi shape memory alloys (SMAs) exhibit distinct thermo-mechanical behaviors affected by the loading frequency, ambient conditions, and the specimen geometry. The effects of these factors are essentially due to the competition of different timescales in phase transitions of NiTi SMAs. However, quantifying the timescale competition still remains a challenge for SMAs subjected to force- or displacement-controlled cyclic loadings. Here we present a thermo-mechanically coupled model for one-dimensional SMA bars to address the effects of timescale competition on the thermo-mechanical responses. Scaling the model gives a dimensionless number lambda indicating the ratio of the loading time to the characteristic time of heat transfer (affected by ambient conditions and the specimen geometry). The model shows that it is the timescale ratio lambda that dictates the thermo-mechanical responses. Comparison of simulation results with experimental data validates the coupled model and the effects of the timescale ratio lambda on the thermo-mechanical responses. The coupled model can predict the responses of SMAs under different combinations of external loadings and ambient conditions and thus provide guidelines for experimental design. (C) 2020 The Author(s). Published by Elsevier Ltd.

【 授权许可】

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