基于形状记忆合金的结构刚度控制研究
Research on Stiffness Control of Structure Based on Shape Memory Alloys

以超声速飞行器结构气动热软化现象为背景，提出了基于形状记忆合金(shape memory alloys，简称SMA)的结构刚度控制方法。设计了实验模型和全铝对照模型，对模型进行频响测试，研究模型刚度控制效果。利用温控箱调节模型的整体温度，研究模型的一阶固有频率与温度的关系。提出了将SMA条带作为加强筋的舵面结构,研究了结构刚度随环境温度升高的变化趋势。考虑到在环境温度作用下SMA不一定能完全相变，搭建了结构刚度主动控制系统。结果表明：结构刚度随着环境温度的增加先是逐渐减小，而后慢慢变大慢慢减小，其在SMA奥氏体相变结束温度处的刚度最大；结构控制后的一阶固有频率与控制前相比增幅可达10%；利用大电容的瞬时放电驱动SMA，使其完全相变，响应时间可达15ms。
A new method based on SMA is studied to control the stiffness of structure in the context of aerodynamic heating of supersonic aircraft. The variable-stiffness rudder structure of strengthening rib replaced by SMA strips is proposed. The results show that the stiffness of the structure can be passively controlled by making use of the feature that the elastic modulus of austenitic phase is higher than that of martensitic phase under a high temperature. Besides, the first order natural frequency of the structure can increase by 10% after the control system works. Furthermore, the changing of stiffness of the structure with the environmental temperature increasing is also studied. An active control system is established because the phase transition of SMA could not be fully completed under the environmental temperature.The experimental results indicate that the instantaneous discharge of large capacitors is used to drive SMA in order to complete the phase transition. The response time of SMA can reach 15ms. In addition, as the temperature increases, the stiffness of structure decreases initially, and then increases gradually. When the temperature is equal to the austenitic finish temperature at zero stress, the stiffness achieves maximum value. After that, it decreases slowly.