Kang Liping, Qian Hui, Guo Yuancheng, Ye Chenyang, Li Zongao
School of Civil Engineering, Zhengzhou University, Zhengzhou 450001, China.
Materials (Basel). 2020 Aug 24;13(17):3729. doi: 10.3390/ma13173729.
Shape memory alloys (SMAs) are a class of functional materials that possess unique thermomechanical properties, such as shape memory effect (SME), superelasticity (SE), damping, and good fatigue and corrosion resistance, which enable them to become ideal materials for applications in earthquake engineering. Numerous studies have shown that the mechanical properties of superelastic SMAs mainly depend on the wire form, or the relationship between the microstructure and thermally induced phase transitions. However, extremely few studies have elucidated the effects of the heat-treatment strategy, size effect of large diameters, and cyclic loading. Herein, the mechanical properties of SMA bars, such as residual strain, energy dissipation, and equivalent damping ratio, were studied with different heat-treatment strategies, cyclic loadings, and strain amplitudes; this was achieved by conducting cyclic tensile tests on SMA bars with four different diameters. The results indicate that the maximum phase transformation stress was obtained with a 14 mm SMA bar subjected to heat treatment at 400 ℃ for 15 min. The mechanical properties were relatively stable after five loading-unloading cycles, which should be considered in engineering applications. The test results provide a mechanical basis for using large SMA bars in self-centering structures in seismic regions.
形状记忆合金（SMA）是一类具有独特热机械性能的功能材料，如形状记忆效应（SME）、超弹性（SE）、阻尼以及良好的疲劳和耐腐蚀性，这些特性使其成为地震工程应用中的理想材料。大量研究表明，超弹性形状记忆合金的力学性能主要取决于线材形式，即微观结构与热致相变之间的关系。然而，极少有研究阐明热处理策略、大直径尺寸效应和循环加载的影响。在此，通过对四种不同直径的形状记忆合金棒材进行循环拉伸试验，研究了不同热处理策略、循环加载和应变幅值对形状记忆合金棒材残余应变、能量耗散和等效阻尼比等力学性能的影响。结果表明，直径为14 mm的形状记忆合金棒材在400℃下热处理15分钟可获得最大相变应力。经过五次加载-卸载循环后，力学性能相对稳定，这在工程应用中应予以考虑。试验结果为在地震区域的自复位结构中使用大型形状记忆合金棒材提供了力学依据。
