Shape memory alloy (SMA) dampers frequently experience cyclic loading over a broad spectrum of strain rates and ambient temperatures, resulting in a significant thermo-mechanical coupling effect during cyclic deformation. Nevertheless, the impact of this coupling effect on the functional degradation of SMAs has not been thoroughly examined, particularly in scenarios involving severe deformation. In this study, a series of strain-controlled cyclic loading–unloading tests were conducted on NiTi SMA wires utilizing various combinations of strain rates ranging from 5 × 10−4 to 6 × 10−2/s and different ambient temperatures (313–393 K). The functional degradation was exacerbated by increasing ambient temperature and loading rate due to the complex interactions among the inelastic deformation mechanisms and thermo-mechanical coupling effects. Furthermore, although the cyclic deformation behavior of NiTi SMA wires varied with the loading rate, this rate dependence diminished with increasing ambient temperature. The synergistic effect of elevated strain rates and high temperatures markedly accelerated the fatigue failure of NiTi SMA wires and substantially altered the underlying microstructural morphology. These findings can provide valuable support for evaluating the service performance of NiTi SMA dampers under various engineering conditions and contribute to developing a cyclic constitutive model for NiTi SMAs.

中文翻译：

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NiTi 形状记忆合金丝在宽应变率和环境温度范围内的循环功能降解


形状记忆合金 （SMA） 阻尼器在广泛的应变率和环境温度下经常承受循环载荷，从而在循环变形过程中产生显著的热机械耦合效应。然而，这种耦合效应对 SMA 功能降解的影响尚未得到彻底研究，尤其是在涉及严重变形的情况下。在这项研究中，利用从 5 × 10-4 到 6 × 10-2/s 和不同环境温度 （313-393 K） 的各种应变率组合，对 NiTi SMA 线进行了一系列应变控制的循环加载-卸载测试。由于非弹性变形机制和热机械耦合效应之间的复杂相互作用，环境温度和加载速率的增加加剧了功能退化。此外，尽管 NiTi SMA 线的循环变形行为随负载速率而变化，但这种速率依赖性随着环境温度的升高而减弱。应变速率升高和高温的协同作用显著加速了 NiTi SMA 线材的疲劳失效，并显着改变了底层微观结构形态。这些发现可以为评估 NiTi SMA 阻尼器在各种工程条件下的服务性能提供有价值的支持，并有助于开发 NiTi SMA 的循环本构模型。