A 64-kHz sandwich transducer fabricated using pseudo 1-3 magnetostrictive composite

A 64-kHz sandwich transducer employing a tube-shaped Terfenol-D/epoxy pseudo 1-3 magnetostrictive composite with 0.61 Terfenol-D volume fraction was developed to alleviate the intrinsic eddy-current losses in magnetostrictive alloy-based transducers. The transducer was designed to operate as a half-wave, longitudinal, mass-spring-mass, linear vibrator. It had a length of 15.7 mm and consisted of a magnetic circuit and a prestress mechanism. The magnetic circuit was composed of the composite tube, a pair of ring-shaped NdFeB permanent magnets, a drive solenoid, and a Ni-based magnetic flux guide. The distributions of the dc magnetic flux lines and magnetic field strength of the transducer were determined using an ANSYS finite-element model. The dynamic performance of the transducer was evaluated by measuring its electrical and vibrational characteristics. The results revealed that the transducer resonates at a frequency of 64.3 kHz with a strain coefficient of 39.2 nm/A, a mechanical quality factor of 39.6, and an effective coupling coefficient of 0.21. Eddy-current losses in the transducer were insignificant in the measured frequency range of 40 Hz-100 kHz. The good transducer performance indicated that Terfenol-D/epoxy pseudo 1-3 composites would be a promising magnetostrictive material for ultrasonic applications.