Shape Memory Alloy Cables

为研究NiTi形状记忆合金(SMA)线材结构拉索的力学性能，提出了一种实验与模拟相结合的方法。多股SMA丝提供了一种方便且经济的方法将SMA丝的优良性能放大到更大的结构中，但在开放文献中还没有对其结构行为和尺度进行研究。与传统钢索相比，形状记忆合金拉索具有自适应特性，即形状记忆模式下具有热活性，超弹性模式下具有极强的弹性/耗散性。与整体式形状记忆合金杆相比，形状记忆合金拉索还具有其他优点，包括：(1)更大的弯曲/扭转灵活性，在某些应用中可改善疲劳性能；(2)减少热滞后，因为相同材料质量的有效传热表面积更大；(3)承载冗余度，导致更优雅的失效模式，对缺陷和处理不当的敏感度更低，以及更好的可靠性。对形状记忆合金拉索的热力行为进行了系统的研究。由NiTi丝制成的一系列原型试件(螺旋线、绞线和电缆)将在一系列温度和加载历史上进行一系列实验。将SMA拉索的响应与实心SMA筋和常规钢索的响应进行比较，以说明它们的优点和局限性。将开发一种数值模拟工具来研究电缆的行为对几何参数和尺寸的敏感性。形状记忆和超弹性模式下的可恢复应变响应将得到改善，并且由于减少了热滞，响应时间也将缩短。由于导线/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。在冲击载荷和周期扰动下，它们还应该表现出异常的动力学行为，这项工作为以后的动力学行为的研究奠定了必要的基础。这笔资金将用于支持一名博士生，该博士生将把拟议的研究作为博士论文的基础。将继续努力，通过暑期实习和独立学习项目，让本科生参与拟议的工作。形状记忆合金电缆在民用、交通、生物医学、消费和能源等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关，在那里可以很容易地将技术从基础研究转移到汽车应用。

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.