Shape Memory Alloy Cables

提出了一种实验与建模相结合的方法来研究由NiTi形状记忆合金（SMA）丝制成的结构电缆的性能。多股SMA钢丝为将SMA钢丝的优异性能扩展到更大的结构提供了一种方便且经济的方法，但其结构行为和缩放尚未在公开文献中进行研究。与传统钢丝电缆相比，SMA电缆具有自适应特性，即在形状记忆模式下具有热活性，在超弹性模式下具有极好的弹性/耗散性。与单片SMA棒相比，SMA电缆还有其他优点，包括：(1)更多的弯曲/扭转灵活性，这可以改善某些应用中的疲劳性能；(2)减少热滞后，因为相同材料质量的有效传热表面积会更大；(3)承载冗余，导致更优雅的失效模式，对缺陷和处理不当的敏感性更低，可靠性更高。对SMA电缆的热力学性能进行了系统的研究。由镍钛丝制成的一系列原型样品（螺旋线、股线和电缆）将在一系列温度和加载历史下进行一系列实验。将SMA电缆的响应与SMA实心棒和传统钢丝电缆的响应进行比较，以展示其优点和局限性。将开发一种数值模拟工具来研究电缆的几何参数和尺寸对其行为的敏感性。改进的可恢复应变响应在形状记忆和超弹性模式，以及改进的响应时间，由于减少热滞后将被证明。由于线/股之间的潜热“串扰”，SMA电缆可能会表现出不寻常和有趣的物理现象。它们在冲击载荷和循环扰动下也表现出不同寻常的动力行为，为今后的动力行为研究奠定了必要的基础。这笔资金将用于支持一名博士生，他将把拟议的研究作为博士论文的基础。通过暑期实习和独立学习项目，将继续努力让本科生参与拟议的工作。形状记忆合金电缆在民用、交通、生物医药、消费和能源领域具有广泛的潜在用途。特别是，PI与新成立的通用汽车/密歇根大学智能材料和结构合作研究实验室有联系，在那里，从基础研究到汽车应用的技术转移可以很容易地发生。

A combined experimental and modeling program is proposed to study the behavior of structural cables made from NiTi Shape Memory Alloy (SMA) wires. Multi-stranded SMA wires offer a convenient and cost-effective way to scale up the excellent properties of SMA wire to larger structures, but their structural behavior and scaling have not been studied in the open literature. Compared to conventional steel cable, SMA cable would have adaptive properties, i.e. thermally active in a shape memory mode and extremely resilient/dissipative in a superelastic mode. Compared to monolithic SMA bars, SMA cables would have other advantages, including: (1) more bending/torsion flexibility, which could lead to improved fatigue performance in some applications, (2) a reduced thermal lag, since the effective surface area for heat transfer would be larger for the same material mass, and (3) load carrying redundancy, leading to more graceful failure modes, less sensitivity to defects and mishandling, and better reliability. A systematic study of the thermo-mechanical behavior of SMA cables will be conducted. A hierarchy of prototype specimens (helical wires, strands, and cables) fabricated from NiTi wires will be subjected to a series of experiments over a range of temperatures and loading histories. The response of SMA cables will be compared to that of solid SMA bars and that of conventional steel cables to demonstrate their advantages and limitations. A numerical simulation tool will be developed to study the sensitivities of the behavior to geometric parameters and size of the cable. An improved recoverable strain response in shape memory and superelastic modes as well as improved response time due to reduced thermal lag will be demonstrated. SMA cables may exhibit unusual and interesting physical phenomena due to latent heat "cross-talk" between the wires/strands. They should also exhibit unusual dynamic behavior under impact loads and cyclic disturbances, and this work lays the necessary groundwork for future study of dynamical behavior. The funding will be used to support a doctoral student who will use the proposed research as the basis for a Ph.D. dissertation. A continuing effort will be made to involve undergraduates in the proposed work, via summer internships and independent study projects. Shape Memory Alloys cables have broad potential use in the civil, transportation, biomedical, consumer, and energy sectors. In particular, the PI is associated with a newly established General Motors/University of Michigan Collaborative Research Laboratory on Smart Materials and Structures, where technology transfer from basic research to automotive applications can occur readily.