Hysteresis modeling of two-way shape memory effect in NiTi alloys

In the present study the two-way shape memory effect (TWSME) of a Ni-51 at.% Ti alloy was investigated and a numerical model, able to simulate its hysteretic behaviour in the strain-temperature response, is proposed. In particular, the TWSME was induced through a proper thermo-mechanical training, carried out at increasing number of training cycles and for two values of training deformation, and the thermal hysteretic behaviour, between Mf (Martensite finish temperature) and Af (Austenite finish temperature), was recorded. The experimental measurements were used to develop a phenomenological model, based on the Prandtl-Ishlinksii hysteresis operator, which was implemented in a Matlab® function and a Simulink® model. A systematic comparison between experimental results and numerical predictions is illustrated and a satisfactory accuracy and efficiency has been observed, therefore the method looks suitable for real-time control of NiTi based actuators.