2.5-kHz magnetostrictive Tonpilz sonar transducer design

Stephen C. Butler

doi:10.1117/12.475007

11 July 2002 2.5-kHz magnetostrictive Tonpilz sonar transducer design

Stephen C. Butler

Proceedings Volume 4699, Smart Structures and Materials 2002: Active Materials: Behavior and Mechanics; (2002) https://doi.org/10.1117/12.475007
Event: SPIE's 9th Annual International Symposium on Smart Structures and Materials, 2002, San Diego, California, United States

Abstract

Naval Undersea Warfare Center has fabricated and tested a 2.5 kHz magnetostrictive sonar transducer to validate various modeling techniques. The transducer selected is a longitudinal vibrator Tonpilz type consisting of Terfenol-D driver, tail mass, radiating head mass, and stress rod bolt with 21 MPa (3000 psi) prestress. The Terfenol-D drive rod is interlaced with three samarium cobalt magnets, one in the center and one on either end magnetically biasing the Terfenol to 60 kA/m (750 Oe). Both the Terfenol-D rods and magnets were laminated to reduce eddy currents. The magnetic circuit is comprised of pole piece discs on each end of the Terfenol-D magnet assembly and an external magnetic cylinder (return path) made of a high-permeability, high-resistivity, high-saturation powdered metal 'T2'. The transducer has a 25 cm (9.8in) diameter radiating face (piston), is 28 cm (11 in.) long, and weighs 15 kg (32 lb.) without the housing. It is 41 cm (16 in.) long and 25 kg (56 lb.) with the underwater housing. The measured results are compared to a finite element model using 'ATILA' and distributed plane wave element equivalent circuit model. The coupling coefficient, permeability and mechanical loss effects for different prestress loads were measured on a resonant Terfenol 'dumbbell' device. The in-water measured results indicate a mechanical Q of 2.5, an effective coupling coefficient of 0.36, an electro-acoustic efficiency of 60 percent, beam pattern directivity index of 6 dB, a maximum Source Level of 214.6 dB re 1uPa/m at 15 Amps AC drive and bandwidth of 2 kHz to 5.4 kHz +/- 1.5 dB.

Citation Download Citation

Stephen C. Butler "2.5-kHz magnetostrictive Tonpilz sonar transducer design", Proc. SPIE 4699, Smart Structures and Materials 2002: Active Materials: Behavior and Mechanics, (11 July 2002); https://doi.org/10.1117/12.475007

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