TIPS AND TRICKS FOR CHARACTERIZING SHAPE MEMORY ALLOY WIRE: PART 2-FUNDAMENTAL ISOTHERMAL RESPONSES
TIPS AND TRICKS FOR CHARACTERIZING SHAPE MEMORY ALLOY WIRE: PART 2-FUNDAMENTAL ISOTHERMAL RESPONSES
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DOI：
10.1111/j.1747-1567.2008.00460.x
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发表时间：
2009-01-01
影响因子：
1.6
通讯作者：
Iadicola, M. A.
中科院分区：
文献类型：
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作者：
Churchill, C. B.;Shaw, J. A.;Iadicola, M. A.
(SMA)钢丝。我们的目标是让不熟悉SMA测试的工程师熟悉SMA测试，并强调技术和解释测试结果方面的缺陷。在前一篇文章(第1部分)中，1介绍了两种商用镍钛合金的热机械实验：一种是奥氏体终温度Af高于室温的形状记忆(SM)丝，另一种是Af低于室温的超弹性(SE)丝。在不同的温度条件下，SM和SE都表现出各自的行为，并描述了导致这些异常行为的基本微观结构机制。提供了每种合金的差示扫描量热仪(DSC)热图，作为量化其相变温度、比热和相变潜热的第一步。在本文(第二部分)中，我们讨论了温度控制和应变测量的技术和良好的实践。通过一系列等温实验继续对相同的两种合金进行表征，以显示在跨越各自的无应力转变温度的温度窗口中拉伸响应的显著范围。特征相变应力和应变被映射以量化材料中的热机械敏感性。最后，讨论了材料不稳定性、应变局部化和传播相变前沿及其对测量响应的影响。
(SMA) wire. Our aims were to acquaint uninitiated engineers with SMA testing and to highlight pitfalls in technique and interpreting test results. In the previous article (Part 1), 1 thermomechanical experiments were presented on two commercial Nitinol alloys: a shape memory (SM) wire, having an austenite finish temperature, Af, above room temperature, and a superelastic (SE) wire, having an Af below room temperature. Both SM and SE behavior were demonstrated for each in different temperature regimes along with a description of the underlying microstructural mechanisms responsible for these unusual behaviors. Differential scanning calorimetry (DSC) thermograms were provided for each alloy as a first step to quantify their transformation temperatures, specific heats, and latent heats of transformation.In this article (Part 2), we discuss techniques and good practice for temperature control and strain measurement. The characterization of the same two alloys is continued through a series of isothermal experiments to show the dramatic range of tensile responses in a temperature window spanning the respective stress-free transformation temperatures. Characteristic transformation stresses and strains are mapped to quantify the thermomechanical sensitivities in the material. Last, material instabilities, strain localization, and propagating transformation fronts are discussed along with their implications on measured responses.