Papers by Keyword: Recovery Force

Abstract: The feasibility of using shape memory alloy (SMA) as actuators to control the vibration of a double-decker cantilever beam is demonstrated in the paper. A new and reliable form of SMA actuator is proposed in this study that no debonding and softening occurs even the maximum shear is generated by recovery force of the SMA wires. The magnitude and stability of the recovery force are tested when the SMA wires with the prestrain are heated cyclically. According to the simulation results, the four vibrational modes (three bending and one torsional) of cantilever beam can be changed simultaneously. Finally the vibrational response excited by pulsing and sinusoidal signal is successfully suppressed by using the SMA actuators in the experiments.

Abstract: The effect of thermal cycling on the martensitic transformation and response characteristics has been studied in bias-SMA spring actuators aged at 350 °C ~ 500 °C. As the number of thermal cycling increases, the Ms temperature of the SMA spring showing only B2→B19' martensitic transformation by aging at 350 or 500 °C goes down. However, SMA spring in which B2→R→B19' martensitic transformation taken place by aging at 400 or 450 °C shows multi-step transformations i.e., M1 and M2 transformations with thermal cycling. The heat flow of M2 transformation increases while the transformation temperature difference between M1 and M2 transformations is enlarged as the number of cycling increases. The recovery displacement and force of bias-SMA spring actuator increase up to the 10th cycle and the extent of increase is the largest at aging temperature of 500 °C. However, both recovery properties decrease after the 10³ or 10⁴ cycles, while the decreasing tendency becomes larger with a rise in aging temperature. Such a change in recovery characteristics of bias-SMA spring actuator with thermal cycling is discussed in connection with training effect or lattice defects introduced during thermal cycling.

Abstract: The SMC belt composed of two kinds of SMAs and SMP was fabricated and the three-way movement and recovery force in bending were investigated. The results obtained can be summarized as follows. (1) The three-way bending movement was achived during heating and cooling based on the characteristics of the SMA tapes and the SMP sheet. (2) The recovery force increased during heating and decreased during cooling. The recovery force was evaluated by the proposed simple model.

Abstract: The shape memory composite (SMC) with shape memory alloy (SMA) and shape memory polymer (SMP) was fabricated, and the two-way bending deformation and recovery force were investigated. The results obtained can be summarized as follows. (1) Two kinds of SMA tapes which show the shape memory effect and superelasticity were heat-treated to memorize the round shape, respectively. The shape-memorized round SMA tapes were sandwiched between the SMP sheets, and the SMC belt was fabricated. (2) The two-way bending deformation with an angle of 56 degrees is observed during heating and cooling. (3) If the SMC belt is heated and cooled by keeping the form, recovery force increases during heating and decreases during cooling.

Abstract: The shape-memory composite belt with a TiNi-SMA wire fiber and a polyurethane-SMP sheet matrix was fabricated. The bending actuation characteristics of the belt were investigated by the thermomechanical tests. Residual deflection obtained by cooling under constant maximum deflection is close to the maximum deflection. The residual deflection disappears by heating under no load. Both the rates of shape fixity and shape recovery are close to 100%. Recovery force which appears by heating under constant residual deflection is 93-94% of the maximum force. The model of bending-spring constant of the shape-memory composite belt is proposed and evaluated based on the experimental data.