Two-way shape memory coil springs: design, actuation and stability

摘要

In industrial applications, shape memory alloys (SMAs) are very often used as two-way actuators, in the form of coil springs, which capitalize on the capacity of small shear to produce large displacement. One way to achieve the two-way actuators is using a one-way shape memory effect SMAs spring with a bias spring, the other way is two-way shape memory effect (TWSME) SMAs spring. However, the TWSME is not inherent property of SMAs, suitable thermo-mechanical training is required to develop this effect. In this work, methods of developing TWSME are designed for SMAs and factors which affect the TWSME are investigated. Two types of TWSME spring are obtained using the designed methods. One type is extension spring, which can extend upon heating and contract upon cooling and this other type is contraction spring, which can contract upon heating and extend upon cooling. The actuation behaviors of these two types TWSME are investigated. And the stability of TWSME was also studied with working cycles and annealing.