摘 要

形状记忆合金(shape memory alloys,SMAs) 作为一种新型智能材料，具有良好的超弹性、形状记忆效应、高阻尼等特性，在航空航天领域、军工领域、医学临床和土木建筑等领域都有许多成功应用实例，如在实际工程中利用合金的超弹性性能和形状记忆效应能够有效改善结构抗震性能，可以作为结构震动控制的理想材料。本文拟对高性能柱状晶组织Cu-Al-Mn形状记忆合金扭转时的力学性能进行研究，以实测实验测定的Cu_71.5Al_18.5Mn₁₀ SMA相关性能参数为基础，基于Auricchio本构方程，利用ANSYS有限元软件对合金扭转力学性能进行模拟，并与合金在常温下扭转实验进行对照分析。本文主要研究工作和结果如下：

1. 使用定向凝固设备制备出了具有轴向高长径比晶粒的柱状晶Cu_71.5Al_18.5Mn₁₀ SMA，对合金的组织结构和力学性能进行了研究。结果表明：合金相变温度为：M_s=52.8℃，M_f=23.5℃，A_s=42.3℃，A_f=72.8℃，室温（lt;M_f）下为马氏体相，100℃以上（gt;A_f）为奥氏体相。铸态合金沿凝固方向在室温和120℃下拉伸的力学性能明显不同，室温下无超弹性，而在120℃时具有超弹性回复，具有大于25%的塑性和14%的超弹性应变。
2. 对柱状晶Cu_71.5Al_18.5Mn₁₀合金进行循环扭转实验，研究发现在加载初期切应力与切应变之间保持胡克定律，弹性阶段极限应力为479.70MPa，极限应变为0.3%。随着载荷增加，相同增量的载荷引发较大的形变量，当试样扭转到120°时，改变加载速率，继续扭转直至试样断裂，此时扭转角为156.02°，切应变为6.2%，切应力为744.00MPa，根据试样加载过程中的切应力-切应变数据计算可得材料的剪切模量为159.90GPa。根据试样循环扭转加载-卸载实验得到的切应力-切应变曲线可以看出，当试样扭转至30°，此时切应变为1.2%，切应力为669MPa，而后卸载至15N时，试样变形量有所恢复，但仍存在一定的残余应变。随后继续加载至切应变为1.2%，切应力为670MPa时，试样再次进入强化阶段，且实验曲线变化路径与卸载之前路径一致，说明材料在加载过程中具有良好的变形协调性和形状记忆效应。
3. 有限元模拟采用基于Auricchio模型的多线性简化本构模型利用拉伸应力-应变曲线数据得到模拟所需参数，并通过ANSYS有限元计算软件对合金扭转循环加载-卸载过程进行模拟研究。所得模拟结果与实验结果较好吻合，但仍存在一定误差需进一步改善。

关键词：形状记忆合金；Cu-Al-Mn合金；力学性能；扭转；ANSYS模拟

Abstract

Shape memory alloys as a new type of intelligent material, it has excellent shape memory effect, super elasticity, high damping and strong corrosion resistance. It has many successful application examples in the fields of aerospace, military industry, medicine, clinic and civil architecture. For example, the super elasticity and shape memory effect of alloy can effectively improve the seismic performance of structure in practical engineering A_s an ideal material for structural vibration control. In this paper, the mechanical properties of Cu al Mn shape memory alloy with high-performance columnar crystal structure in torsion are studied. Based on the measured parameters of Cu_71.5Al_18.5Mn₁₀ SMA, and based on the Aurichio constitutive equation, the torsional mechanical properties of the alloy are simulated by ANSYS finite element software, and compared with the torsion experiments of the alloy at room temperature. The main research work and results are as follows:

1. The columnar Cu_71.5Al_18.5Mn₁₀ SMA with axial high aspect ratio grain was prepared by directional solidification equipment. The microstructure and mechanical properties of the alloy were studied. The results show that the transformation temperature of the alloy is M_s = 52.8 ℃, M_f = 23.5 ℃, A_s = 42.3 ℃, A_f = 72.8 ℃, martensite at room temperature (lt; M_f), austenite above 100 ℃. The mechanical properties of the as cast alloy are obviously different at room temperature and 120 ℃ along the solidification direction. There is no hyperelasticity at room temperature, but it has hyperelasticity recovery at 120 ℃, with plasticity of more than 25% and hyperelastic strain of 14%.
2. The cyclic torsional loading unloading experiment of columnar Cu_71.5Al_18.5Mn₁₀ SMA was carried out. It was found that Hooke's law was maintained between the shear stress and the shear strain at the initial stage of loading. The ultimate stress and strain at the elastic stage were 479.70MPa and 0.3%, respectively. With the further increase of the load, the same increment of the load leads to larger deformation variables. When the specimen is twisted to 120 °, change the speed of the rack and continue to twist until the specimen breaks. At this time, the torsion angle is 156.02 °, the shear strain is 6.2%, and the shear stress is 744.00MPa. According to the shear stress-shear strain data during the loading process, the shear modulus of the material is 159.90GPa. According to the shear stress-shear strain curve obtained from the cyclic torsional loading unloading experiment, when the specimen is torsional to 30 °, the shear strain is 1.2%, the shear stress is 669MPa, and then unloaded to 15N, the deformation of the specimen recovers, but there is still a certain residual strain. When the shear strain is 1.2% and the shear stress is 670MPa, the specimen enters the strengthening stage again, and the change path of the experimental curve is the same as that before unloading, which shows that the material has good deformation coordination and shape memory effect in the loading process.
3. In the finite element simulation, the multi linear simplified constitutive model based on the aurichio model is used to obtain the parameters required by the simulation using the tensile stress-strain curve data, and the cyclic loading unloading process of alloy torsion is simulated by the ANSYS finite element calculation software. The simulation results are in good agreement with the experimental results, but there are still some errors to be further improved.

Key words: shape memory alloy; Cu-Al-Mn alloy; mechanical properties; torsion; ANSYS simulation

目录

第1章 绪论 7

1.1 形状记忆合金的基本特性 7

1.1.1 形状记忆效应 7

1.1.2 超弹性效应 8

1.2 形状记忆合金的种类和研究现状 9

1.3 Cu基形状记忆合金的特点与相关应用 10

1.4 课题来源 11

1.5 研究内容和技术路线 11

1.5.1 研究内容 11