Abstract

Defence Research Establishment Atlantic (DREA) is developing a flextensional barrel-stave projector which utilizes a magnetostrictive Terfenol-D driver. Our attention has focussed on three critical aspects of the design of the projector: (1) reduction of eddy currents, (2) incorporation of permanent magnets to bias the Terfenol and (3) a low reluctance magnetic flux return path. Here we describe a projector design which deals with these three aspects. The Terfenol rod is sectioned radially in order to reduce eddy current losses. Co-Sm permanent magnets are used to provide the magnetic bias field to the Terfenol. The magnetic flux return path is comprised of ferrite disks at the ends of the drive rod and a high permeability cylinder constructed of Metglas 2605TCA. The total projector mass is 3.85 kg. In water the resonance occurs at approximately 1.0 kHz and the bandwidth is 310 Hz. At resonance the distortion limited source level was measured to be 197.7 dB re 1μPa@ 1m and the efficiency was 32.3%.

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