Phase Sensitive Thermography of Magnetostrictive Materials Under Periodic Excitations

Abstract

The use of giant magnetostrictive materials in actuator and sensor applications is still relatively new. Giant magnetostrictive materials, such as Terfenol-D, are unique in producing large deformation under a magnetic field. Applications of these materials in solid state actuators and transducers may require more knowledge on the interaction between geometry and material properties for a specific design. In order to gain more understanding of the magnetostriction mechanism, phase sensitive or lock-in thermography has been used to study Terfenol-D. Thermography is useful in that it allows for full field measurement of the surface of an object with a relatively simple setup. By applying phase sensitive detection and lock-in amplification, small surface temperature changes caused by the magnetostriction through periodic loading can be detected. Two forms of Terfenol-D materials, monolithic and epoxy composite, are the main focus in this studied. The increase in temperature for the monolithic material is in contrast to the decrease in temperature for the composite when they undergo magnetostriction. In addition, the presence of geometric features on monolithic Terfenol D can cause variations in strain distribution. It is also observed that the detection method is quite sensitive to perturbations in strain induced by modifications of the sample geometry.