弹簧指数对镍钛合金弹簧缓冲吸能能力的影响

形状记忆合金(SMAs)弹簧具有大应变可逆变形能力，在吸能缓冲和振动控制等领域具有重要应用潜力。本工作研究了弹簧结构设计对镍钛SMAs性能的影响规律。采用冷拉拔和退火相结合的方法制备直径1.2mm的Ti-52.5at%Ni合金丝，并通过室温下芯轴绕制成型和高温退火相结合的方式制备弹簧指数C分别为6.0、7.7和9.3的弹簧，通过测试合金丝和弹簧的超弹性曲线研究弹簧结构的吸能性能。研究表明，基于弹簧的超弹性变形过程，室温(298K)下3类弹簧在120 mm的最大位移幅值下单位体积吸能分别为4618、2225和1143 kJ/m³，弹簧指数C为6.0的弹簧吸能能力最优。318K下，弹簧处于完全奥氏体态，弹簧指数C为6.0的弹簧单位体积吸能(6662kJ/m³)是同等载荷(47 N)条件下合金丝(34.7 kJ/m³)的192倍。同等条件下，弹簧结构具有比合金丝优异的吸能能力。因此，超弹性SMAs弹簧在缓冲减振结构上具有良好的应用前景。

Effect of spring index on the energy absorption capacity of Nitinol springs

Shape memory alloy (SMAs) springs have the ability to perform giant reversible strain, which is of great importance to the energy absorption buffer and vibration control applications. In this paper, the influence of structure design on the performance of NiTi SMAs springs is studied. Ti-52.5at.%Ni alloy wires with diameters of 1.2mm were prepared by cold drawing and subsequent annealing, and springs with spring index C of 6.0, 7.7, and 9.3 were prepared by mandrel wound molding and subsequent high temperature annealing, respectively. The energy absorption performances of the springs were studied by testing the superelastic curves of the alloy wires and springs. The results show that, based on the superelastic processes, the energy absorption capacity per unit volume of the three types of springs at room temperature (298K) is 4618, 2225 and 1143kJ/m3 at a maximum displacement amplitude of 120mm, respectively, where the spring with spring index C of 6.0 has the best energy absorption capacity. Furthermore, the energy absorption per unit volume of spring with spring index C of 6.0 reaches 6662kJ/m3 at 318K due to its full austenite state, which is 192 times higher than that of the alloy wire (34.7kJ/m3) under the same load (47N), meaning that under same condition, the spring structure has better energy absorption capacity than that of the alloy wire. Therefore, superelastic SMAs springs may show great potential in the future application of damping structures.