Torsional Properties of TiNi Shape-Memory Alloy Tape for Rotary Actoator

In order to develop the novel rotary actuator with an SMA tape, the torsional deformation and fatigue properties of a TiNi SMA tape and rotary actuator models were investigated. The results obtained are summarized as follows. (1) In the SMA tape subjected to torsion, the martensitic transformation appears along the edge of the tape due to elongation of the edge the tape and grows to the central part. (2) The number of cycles to failure decreases with an increase in the maximum angle of twist in the torsion fatigue test. The fatigue life in pulsating torsion is longer than that in alternating torsion by five times. The torsional fatigue limit exists in a certain value of dissipated work of the tape in each cycle. (3) The two-way rotary actuator models by using two kinds of SMA tapes were demonstrated. The two-way rotary driving element or actuator with a small and simple mechanism can be developed by using torsion of the SMA tapes.