High frequency wideband underwater acoustic transducer for ring shaped composite material

A kind of circular ring high frequency wideband underwater acoustic transducer is developed by using the Low Q value and broadband characteristics of the piezoelectricity composite material,and the dual mode coupling is used to broaden the bandwidth of the transducer by double ring stacking along the axial direction.Through theoretical analysis and simulation calculation,the geometric dimensions of the sensitive components are determined.The piezoelectric composite rings are processed and then the stack sensitive element can be made by stacking two piezoelectric composite rings with the same outer diameter and different thickness in axial direction by cutting piezoelectric ceramicsfilling the flexible polymer-coating electrode.Finally,the transducer can be made by pouring waterproof sound-permeable layer.The performances of transducer have also been tested in the water and the test results show that the resonant frequency is 410 kHz,the maximum transmit voltage response is 150 dB,the-3 dB bandwidth can reaches 60 kHz,the horizontal directivity（-5 dB） is 360°,and the vertical directivity（-3 dB） is 20°.It is also shown that the bandwidth of the transducer can be enlarged remarkably by using the method of stacking two different thickness piezoelectric composite rings along the axial direction,and the horizontal omnidirectional emission of acoustic wave can be realized

A flextensional transducer and its algorithmic method of resonant frequency

A flextensional transducer with an Omega shape and its algorithmic method of the resonant frequency and the shape functions are suggested. The Omega transducer is separated into four parts treated respectively as a thin shell of revolution and the theories of thin shells of revolution and piezoelectricity are used to obtain the energy functional of each part so that the sum of the energy functionals of the four parts is the energy functional of the whole Omega transducer. By substituting the shape functions with undetermined coefi3cients and the geo- metrical boundary conditions into the energy functional of the Omega transducer, the resonant frequency of the Omega transducer is firstly determined with the Rayleigh-Ritz method. With the gotten resonant frequency, the constant coefficients of the shape functions are following solved through the Rayleigh-Ritz partial differential equations and the geometrical boundary condition equations. The solving method of the resonant frequency and the shape functions is also extended to the cymbal transducer. Such an analytical method is verified to be feasible by the results of the finite element analysis and experiments. The research indicates that （1） The radial vibration of the piezoelectric ceramic is in phase with the longitudinal vibration of the top of metal cap, and it cut down the reversed phase component in the sound field. The Omega transducer can be a low frequency transducer. （2） The determination method of the resonant frequency and the shape functions give a solution to the optimum designs of the Omega transducer and the cymbal transducer. （3） The determination method of the resonant fi＇equency and the shape functions can also be used in other flextensional transducers or other structures which are composed of thin shells of revolution, so it is universal.