Shape Memory Alloy Cables

提出了一种结合实验和建模的程序来研究由NiTi形状记忆合金（SMA）丝制成的结构索的行为。多股SMA线提供了一种方便且具有成本效益的方法，可以将SMA线的优异性能扩展到更大的结构，但在公开文献中尚未研究其结构行为和缩放。与传统的钢索相比，SMA缆索将具有自适应特性，即在形状记忆模式下热活性，并且在超弹性模式下具有极强的弹性/耗散性。与整体SMA杆相比，SMA电缆具有其他优点，包括：（1）更大的弯曲/扭转柔性，这在某些应用中可导致改进的疲劳性能，（2）减小的热滞后，因为对于相同的材料质量，用于热传递的有效表面积将更大，以及（3）承载冗余，导致更优雅的失效模式，对缺陷和误操作的敏感性更低，可靠性更高。本文将对形状记忆合金缆索的热机械性能进行系统的研究。由NiTi金属丝制成的原型样品（螺旋线、股线和电缆）的层次结构将在一系列温度和载荷历史范围内进行一系列实验。将SMA索的响应与实心SMA杆和传统钢索的响应进行比较，以证明它们的优点和局限性。将开发一个数值模拟工具来研究电缆的几何参数和尺寸的行为的灵敏度。一个改进的可恢复的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。SMA电缆可能由于线/股之间的潜热“串扰”而表现出不寻常和有趣的物理现象。它们在冲击载荷和周期扰动下也应该表现出不寻常的动力学行为，这项工作为今后的动力学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，他将使用拟议的研究作为博士学位的基础。论文将通过暑期实习和独立研究项目，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、运输、生物医学、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.