Study On Novel Quadrilateral Flextensional Transducer

With the continuous improvement and progress of submarine vibration reduction and noise reduction technology in recent years,sonar detection mode is forced to undergo a major change.Low-frequency active sonar detection technology becomes particularly important,so low-frequency and high-power transmission transducers develop rapidly.Flextensional transducer is a typical transducer with the characteristics of low frequency and high power.Quadrilateral flextensional transducer is a novel structure of transducer,with the radiating larger area and higher active material utilization.These characteristics make it suitable for use as low frequency and high power underwater emission sound source and it contains multiple sets of vibrators and multiple sets of radiation surfaces,which also make this transducer has good ductility and great room for development.The main content of this paper is to design a quadrilateral flextensional transducer with working frequency band below 500 Hz,and study its low frequency,high power and wide band characteristics.Firstly,starting from the basic structure of the quadrilateral flextensional transducer,the structural characteristics,vibration modes and working principles of the quadrilateral flextensional transducer are introduced.At the same time,the characteristics of Terfenol-D,a giant magnetostrictive material,are also introduced.Secondly,the advantages and disadvantages of quadrilateral flextensional transducers are summarized by comparing with traditional flextensional transducers.For flextensional transducer,when the working frequency band below 500 Hz,its maximum size is more than 1m,which presents many difficulties in practical application and process implementation.This paper presents a small size as much as possible,to achieve low frequency working solution,using quadrilateral bending ductility of the transducer,respectively in four groups of the same arc outside added a same radiating surface.By adding radiation mass,the radiation reactance of the transducer is increased and the resonance frequency of the transducer is reduced.The radiation mass is connected with the maximum center displacement of the curved beam of the shell,in this way the displacement can be transferred to the outer surface of the radiating mass to increase the radiating area and improve the acoustic performance.At the same time,the rare earth Terfenol-D material with low sound velocity,low young’s modulus,high energy density and large strain is selected as the driving oscillator to further improve the acoustic radiation performance of the transducer in the low frequency band.Then,ANSYS finite element software is used to simulate the new quadrilateral flextensional transducer with radiating mass block,and its vibration characteristics in air and electroacoustic characteristics in water are obtained.According to the optimized design of the structural parameters,a prototype transducer was made.The size after filling was Φ640mm ×190mm and sealing was 150 kg in air.Its electro-acoustic performance was tested in the silencer tank,and it was found that the resonant frequency in the water was 307 Hz,the maximum sending current response was 179.5dB,and the response fluctuated 3dB in the working frequency band of 250Hz~370Hz.Finally,on the basis of the development of the new quadrilateral flextensional transducer,two schemes are proposed to further improve its bandwidth.First,by changing the structure of the radiated mass block,a new mode which can be coupled with the first bending vibration mode is created to form a broadband operation.Second,by means of mixed excitation,the intrinsic reactance complementarity of rare earth materials and piezoelectric materials is utilized to realize the energy conversion and distribution between electric energy storage elements and mechanical vibration,thus effectively expanding the working bandwidth.The simulation results show that both schemes can achieve the low-frequency,high-power and wide-band performance of the quadrilateral bending.