Hysteretic behavior and recoverability research on the shape memory effect of SMA bars under cyclic loading

To utilize the special shape memory effect of shape memory alloy (SMA) to develop energy dissipation devices with a good energy dissipation effect and easy recovery of residual deformation after an earthquake, six SMA bars with a diameter of 14 mm were tested under multiple loading schemes in this paper. Hysteretic performance indicators, such as the hysteresis loop, energy dissipation capacity, secant stiffness, equivalent damping ratio and deformation recovery rate, were analyzed. The results illustrated that all specimens exhibited the desired full and stable hysteresis loops and a high residual deformation recovery rate achieved by water-bath heating and cooling after being subjected to 6.0% tensile strain. Due to the characteristics of SMA material, excessive compressive strain caused the stress value to soar, and hysteresis loops contributed to the phenomenon of tension-compression stress imbalance and affected the deformation recovery rate. No significant differences were observed in the bearing capacity and energy dissipation capacity of the same specimen with a strain amplitude of 6.0% after repeated loadings, indicating that martensitic shape memory alloys (SMAs) have stable mechanical characteristics and favorable recycling performance. The tensile cyclic constitutive model and tension-compression cyclic constitutive model of the martensite shape memory effect were proposed. Based on MATLAB/Simulink software, numerical simulations were carried out. The simulation results and fitted the experimental results, which proved the theoretical support for utilizing the shape memory effect of martensite SMA.