Papers by Keyword: SMA Coil Spring

Abstract: The present authors have invented a new method of changing coil orientation of a coil spring. The major merit of coil orientation change for SMA are reduction of space and control of two way shape memory effect. For instance, when a coil is heated above Af temperature with a load, the coil contracts. There is unrecovered strain which is attributed to elastic deformation by the load. The elastic strain can be eliminated by changing coil orientation. By removing elastic strain, the necessary space can be reduced. Besides generation and control of two way shape memory effect is presented using the reverse of coil orientation.

Abstract: A theoretical model of the displacement-heating response of the differential shape memory alloy (SMA) actuator was developed. The model was constructed by using the constitutive equation and considering the force equilibrium and the energy balance on the SMA. The output displacement was predicted as a function of the heating power by the model and the simulations of the output displacement and temperature of the SMA actuator were also obtained. To evaluate the model, a prototype actuator which was made up of two SMA coil springs placed opposite each other was briefly described and an experimental setup of the SMA actuator was developed to study the relations among the heating power, the temperature and the output displacement of the SMA actuator. The similarity between the simulated and experimental results verified the proposed model, which indicated that the proposed model could express the thermo-mechanical behavior of the differential Ni-Ti SMA actuators.