Research On Major Axis Lengthened Rare Earth Flextensional Transducer

In the last few decades, to further realize a low-frequency, broadband and high power underwater transducer has become a focus key point, which meets the demands of marine monitoring technology,anti submarine technology and underwater remote communications based on acoustic. Typical class IV flextensional transducer is a common low frequency sound source with the characteristics of low frequency, high power and smart size. While its working frequency range is usually not wide. Multi-mode-coupling method is one of the main methods to realize broadband underwater acoustic transducer. Rare earth giant magnetostrictive materials has the characteristics of the low velocity, high energy density and high electromechanical coupling coefficient. It is a main active material following the piezoelectric material, and is easier to realize low frequency and power. In this paper, a major axis lengthened class IV flextensional transducer is designed which achieves broadband characteristics by coupling the first flexural vibration mode and membrane mode. The use of giant magnetostrictive material, Terfenol-D, as driven material, has reduced the membrane mode frequency and improved the transmission power.This paper introduced the development of the rare earth flextensional transducers, and the characteristics of giant magnetostrictive material first. A magnetic - piezoelectric analogy method was obtained by comparison of pressure equation of magnetic and piezoelectric equation and applied to realize the simulation of rare-earth transducer with finite element software ANSYS.Then the finite element model of a major axis lengthened class IV flextensional transducer in air and water was established by the finite element software ANSYS. The acoustic radiation characteristics of vibration mode, current response were analyed to optimize the basic structure dimensions of the transducer. Reference to magnetic circuit analysis in the field of speaker, the magnetic field strength in Terfenol-D was obtained through theoretical calculation and verified by ANSYS electromagnetic analysis. The transducer was designed to have a bandwidth of 1.3kHz?2.7kHz and the maximum transmitting current response level 179dB referenced to 1uPa/A.Finally, the prestressed analysis was adopted, and fabricated and processed the elements of major axis lengthened class IV flextensional transducer. The transducer was measured in anechoic tank. It has a working frequency range, 1.05kHz?2.2kHz,and the maximum transmitting current response level is 180dB, which is approximately accord with the simulation of ANSYS finite element software.The results show that the major axis lengthened design can reduce the the membrane mode frequency of class IV flextensional transducer and achieve the broadband working of rare earth class ? flextensional transducer.