Tunable Load Adjustment Mechanism by SMA-Actuated Bistable Beam

A novel SMA-actuated bistable beam was fabricated and investigated to fulfill load adjustment in this study. The SMA curved beam actuator was connected with the compliant beam, implementing both load bearing and self-actuating. The prototype and the fabrication process of the bistable mechanism were also developed. Considering multiple inflection points in the deflection curve, the bistable snap-back mechanism was modeled and analyzed through large deflection theory. Moreover, the moment–angle curve, the evolution of deflection modes, and the energy landscape were presented. The key characteristic of the studied bistable system was the capability of horizontal load adjustment during snap-back, which was employed to design the fully compliant mechanisms with variable ranges of load adjustment. Experiments were conducted to test the performance of load adjustment. It was found that the decrease of horizontal load could be reached. The adjustment range of horizontal load could be controlled through the geometric parameters of compliant beam and SMA curved beam actuator. Moreover, the bistable beam could be reset by applying a concentrated force and cycling actuation test was conducted to confirm that point. The proposed bistable mechanism is compact, self-actuating, and fully compliant, implying the potential application in programmable structures and metamaterials.