Two-way behavior of a Nitinol torsion bar

In this paper, the experimental study of a NiTi shape memory alloy bar with nominal diameter of 6.5 mm is presented. First, some torsion experiments, including torsion cycling at constant temperature and thermal cycling under constant torque, were carried out. In these test, the torque was applied in both positive and negative directions. Two-way memory behavior and some unique phenomena, such as kink and easy-training, were found and hence, a series of uniaxial tension test was performed in order to understand the observations. After presenting the experimental work, the reason behind these phenomena is discussed.