SMA bending bars as self-centering and damping devices

This study proposed a new type of the shape memory alloy (SMA) bending bars with a new clamping machine and investigated their bending and cyclic behavior subjected to pushing and pulling actions through experimental works. The aim was to characterize the self-centering and damping capacity of the SMA bending bars to develop self-centering and damping devices and evaluate their efficiency in seismic and dynamic applications. For this aim, two types of SMAs were considered: (1) superelastic SMA (SE SMA) and (2) martensite SMA (MA SMA). First, the bending tests were performed on single SE SMA and MA SMA bars and their corresponding bending behaviors were illustrated in the form of force-displacement curves. Results showed that the MA SMA bar provided higher energy dissipation capacity while the SE SMA could provide a better displacement recovery. Thereafter, the bending behaviors of multiple bars with various combinations of SMA bars, namely, double SE SMA (SS), SE SMA-MA SMA-SE SMA (SMS), and MA-SE-MA (MSM) were investigated. Results showed that MSM provided the highest energy dissipation capacity among all while the SMS showed a better structural performance considering a combination of damping and self-centering capacities. Then, to enhance the displacement recovery and energy dissipation capacity of SMA bars, the single SE SMA bar, and SMS were annealed. Results showed that the annealing enhanced the structural performance, but no perfect displacement recovery was still obtained.