Abstract:
Terfenol-D is a magnetostrictive rare-earth alloy having giant dynamic strain capabilities and low Young's modulus compared to PZT ceramics. Therefore, terfenol-D is a good candidate for realizing high-power, low-frequency projectors for oceanography or sonar. This paper presents two magnetostrictive projectors which have been recently designed and realized for the French Navy. The first one is a tonpilz transducer (TRIPODE) which uses three parallel terfenol-D rods as drivers. Magnetic dc bias and excitation are produced by coils. The drivers are surrounded by a cooling liquid continuously stirred by an electrical device. In water, the maximal acoustical power reaches 4 kW at 1.1 kHz. TRIPODE volume and mass are, respectively, 22 dm[sup 3] and 60 kg. The second one is an axisymmetrical double-ended longitudinal vibrator (JANUS) having a central terfenol-D rod. Permanent magnets provide magnetic dc bias. A specific thermal analysis has been performed to enable heat evacuation by natural convection. Models predict an acoustical power of 1.5 kW at 400 Hz. JANUS volume and mass are, respectively, 25 dm[sup 3] and 100 kg. For both transducers, various results obtained at the design stage during realization and experiments are provided.