A shape memory alloy actuated release device using non-self-locking thread

This paper proposes a novel non-explosive and resettable release device driven by shape memory alloy (SMA), which can replace the commonly used pyrotechnic device. In the scheme, a flywheel nut with bidirectional thread is connected with two screws through the non-self-locking thread, and the target adapters are fixed with the two screws and then locked into a hole by the flywheel nut. When unlocking, the offset SMA actuator releases the flywheel nut by triggering the pulley assembly and multi-level levers. Under the pulling force of the pre-tightening load of the screws, the flywheel nut rotates at high speed to unlock the screws, thus releasing the target adapters. After separation, the device can be quickly reset with the reset tool without replacing any parts. The prototype of the release device is fabricated and tested; according to the performance test results, the device can bear the maximum bi-directional preload of 10 kN and the average unlocking force is 9.73 N. The unlocking time decreases with the increase in driving voltage, and the average unlocking response time is 342 ms under 9 V voltage. Furthermore, the actuator can function well with a lifetime of more than 50 cycles. It is concluded that this scheme has potential advantages to replace the traditional non-reusable explosive driving device.