The Damping Capacity Of TiNi Shape Memory Alloy And Its Ring Dampers

In order to fabricate novel dampers with outstanding performances by sufficiently exerting the high damping capacity of shape memory alloy (SMA), the influences of heat-treatment, loading condition and pre-strain on the hysteretic characteristics of TiNi SMA and the relationships between its hysteretic properties and its vibration characteristics were investigated in this paper. Base on above studies, two types of TiNi SMA ring dampers named as single-direction damper and double-direction damper were designed, and their damping capacities were investigated.The heat-treatment technics optimized by the experimental investigations can make Ni-rich SMA (Ti-50.9at%Ni) possess an ideal hysteresis loop. By the cycle loading test and the theoretic analysis of the vibration characteristics of SMA in the single degree of freedom (SDOF) vibration system consisting of SMA wire, load and accessional spring, it was found that the high damping capacity of SMA can be sufficiently utilized if the strain amplitude and the pre-strain were chosen properly, and the hysteresis loop shape of SMA in the damper was optimized, but it was restrained by the accessional spring.Under the cycle loading, the TiNi SMA rings without restriction can hardly dissipate the energy, and its damping capacity and load-bearing ability are low. However, when the TiNi SMA rings are used in the single-direction damper, the damper possessed a good damping capacity, load-bearing ability and an ability to withstand overloading because the restriction of the baffle could change the magnitude and distribution of the internal stress in the SMA rings.The static damping capacity of the single-direction TiNi SMA ring damper was extraordinarily related to the number of SMA rings, the horizontal pre-deformation and the displacement amplitude. With increasing the number of the rings, its load-bearing ability and energy loss under cycle loading were increased, but its damping capacity was not improved. A proper horizontal pre-deformation can increase the damping capacity of the damper with single SMA ring at small displacement, but as the number of rings and the displacement increasing, the horizontal pre-deformation would decrease its damping capacity. With the displacement amplitude increasing, not only the damping capacity was improved, but also the shape of hysteresis loop was changed. When the displacement amplitude was large enough, the hysteresis loop was changed into the triangle shape, which can sufficiently exert the high damping capacity of SMA in the single-direction TiNi SMA ring damper.Finally, based on optimizing the configuration of the single-direction ring damper, a double-direction TiNi SMA ring damper was designed, and its vibration characteristics was investigated. The results indicated that the vibration characteristics of the double-direction...