Numerical study of the influence of the reverse martensitic transformation completion degree on the cyclic stability of a shape memory alloy-based actuator

Despite all the advantages of shape memory alloy-based actuators, their widespread adoption is hampered by a significant drawback: a gradual decline in performance with repeated actuation. The ways to overcome this drawback are explored. Based on microstructural modeling, the influence of the degree of completion of the reverse martensitic transformation on the operational stability of a torsion actuator with a working body made of a TiNi alloy was investigated. The existence of a critical transformation threshold (~ 75%) has been identified: exceeding it leads to significant loss of work output, while limiting the transformation to this level ensures practical stabilization of the working cycle parameters. A compromise in the influence of the transformation degree was revealed: reducing it improves the stability of the actuator parameters but reduces the work output per cycle. Based on the obtained results, criteria for selection of an optimal operating mode for actuators intended for long-term cyclic operation were formulated.