Shape Memory Alloy(SMA) has been used in many sngineering fields because of it's good characteristics of actuator. For example, SMA wire can be embedded easily in the polymer composite laminate and then be used as actuator for structural control. Since the actuation force and strain have a significant influence on the electrical resistance of SMA wire, it is possible to use the SMA wire as a sensor of such a physical quantities. In this study, the possibility for the application of Ni-Ti SMA wire as sensor is investigated.
Tensile tests are conducted with Ni-Ti SMA wire specimens under the constant temperature. For this test a simple material tester is developed. Through these tests the deformation behavior of Ni-Ti SMA wire and electrical resistance variations are observed. Based on the martensite-austenite phase transformation model, electrical resistance variations of specimen are simulated. Constrained heating tests are also conducted with a same specimens. Through these tests the relationship between electrical resistance and actuation force are obtained.
From the experimental results of Ni-Ti SMA wire specimens, the following results are obtained.
Ni-Ti SMA wire showed good linearity in relationship between the strain and electrical resistance within the pseudo-elastic range. During R-phase transformation the electrical resistance is linearly decreased with increasing actuation force.
Ni-Ti SMA wire sensor is applied to Glass Fiber Reinforced Plastic(GRP) composite beam to sense strain and actuation force. Differential operation of electrical resistance is applied to remove the influences of temperature change when used as a strain sensor.
As a results we find out the possibility of Ni-Ti SMA wire as a dual-mode sensor for strain and actuation force.