形状记忆合金弹簧变形速度的研究

形状记忆合金 (SMA)弹簧具有形状记忆功能 ,电热驱动时的相变过程中有回复力输出。这种弹簧的回复变形速度先随回复位移的增加而逐渐增加 ,当回复位移接近中间位置时速度达到最大值 ,并在一段位移内保持最大速度不变。此后 ,随回复位移的增加而减小 ,达到记忆长度时速度为零。通过控制电流可控制SMA弹簧的回复变形速度 ,但不能选择过高或过低的电流 ,否则会破坏其记忆功能。在使用SMA弹簧时应选择合适的载荷和拉伸变形长度 ,过大的载荷不仅使其回复变形速度变得很慢 ,而且还会使弹簧产生不完全回复变形 ,从而降低SMA弹簧的循环工作寿命。过大的拉伸变形长度 ,同样也会降低其循环工作寿命。

Deformation Velocity of Shape Memory Alloy Spring

The restoring velocity characteristics of shape memory alloy (SMA) spring under the condition of electrothermal driving is studied experimentally. The results show that the restoring velocity of SMA spring gradually creeps up with increase of restoring displacement and reaches a maximum value as the restoring displacement approaches the halfway of the position. The maximum velocity keeps unchangeable at a length of intermediate displacement first, then the velocity gradually decreases with increase of restoring displacement. Under the action of altering current, the restoring velocity can be controlled easily. The current should not be too high or too low as it would destroy the memory function of SMA spring. Not only the too high load but also the too big tensile deformation length can slow the restoring velocity and result in incomplete restoring deformation and then curtail the repeating work life of SMA spring.