| With the rapid development of acoustic technology,piezoelectric composite material,which has low acoustic impedance,small plane electromechanical coupling coefficient and excellent flexible characteristics,is widely used in research and development of biomedical sensors,underwater transducer and array.These transducers and arrays are widely used in underwater acoustics,medical ultrasound and detection of acoustic field.1-3-2 type piezoelectric composite material,whose structure can be seen as 1-3 type piezoelectric composite materials and ceramic substrate connecting in series,is of modified 1-3 piezoelectric composites.1-3-2 type piezoelectric composite material,which is same as 1-3 type piezoelectric composite material,not only has the advantages of low density,wide band and high sensitivity,but also has stable mechanical properties and temperature characteristics.Based on the 1-3-2 type or its modified 1-3-2 piezoelectric composite materials,the 1-3-2 type piezoelectric composites underwater transducer and sandwich ultrasonic transducer are researched and designed in this paper.The main content includes the following sections:(1)Based on the series parallel and uniform field theory,the analysis method of 1-3-2 piezoelectric composite material equivalent parameter is introduced.The equivalent parameter expression of elastic constants,dielectric constants,piezoelectric constant and density of the 1-3-2 type piezoelectric composite material are given.Thickness vibration characteristics of the 1-3-2 type piezoelectric composite material are analyzed,and its thickness vibration frequency equation is given by applying the method of equivalent circuit calculation.The simplified theory of analyzing 1-3-2 type piezoelectric composites material and transducer by applying the finite element software ANSYS is introduced.The simplified finite element model of 1-3-2 type piezoelectric composite material is given,and the feasibility of the finite element model is verified.(2)The 1-3-2 type piezoelectric composite ceramic material is designed and manufactured by the method of cutting and filling the ceramic.The thickness vibration characterics of 1-3-2 type piezoelectric composite ceramic material is analyzed by finite element simulation and experiment.Using the 1-3-2 type piezoelectric composite ceramic materials with low impedance,low mechanical Q value,high mechanical and electrical conversion coefficient,easy way of making electrode,stable mechanical properties and temperature characteristics,the piezoelectric composite broadband underwater transducer is developed.The computational expressions of commonly used performance indicators and test methods of underwater transducer are expressed,and the underwater transducer is tested in the standard test pool.The effect of element with different size,different cutting depth and different cutting seam width on resonance frequency and transmiting performance of composite piezoelectric underwater transducer are discussed.The results show that the composite underwater transducer based on the 1-3-2 type piezoelectric composite material has the characteristic of pure mode,high transmitting voltage response and broad band in the working frequency range.(3)The high frequency phased array underwater transducer based on the modified 1-3-2 type piezoelectric composite material is studied.The structure and certain rule of 1-3-2 type piezoelectric composite material are used for designing phased array underwater transducer.The thin ceramic substrate of the modified 1-3-2 type piezoelectric composite material is used for distributing the elemnets on the certain location.The gap between the nearby elements is filled by decoupling polymer.The directivity of the phased array underwater transducer is calculated and the beamforming scheme is presented.The elements of the piezocomposite material are embattled in planar directions to form four wave beams.The transmitting and receiving wave beams are achieved by phase-shifted to restrain the main lobe and reserve the grating lobe.The high frequency phased array transducer is fabricated and the performance indicators of the phased array transducer are tested.The results show that this type of phase-array transducer has the advantages of better performance for transmitting and receiving sound wave,compact and steady structure,easy way of making elements and electrode.(4)An improved 1-3-2 type piezoelectric composite sandwich transducer is researched and designed.The apparent elasticity method is used to calculate the coupled vibration of large size structure,and the frequency equation of the vibration along longitudinal direction is given.By way of using the approximate model and vibration theory,the frequency characteristics of the modified 1-3-2 type piezoelectric composite material is analyzed and the frequency equation in the thickness direction is expressed.The modified 1-3-2 type piezoelectric composite material is produced by cutting the pure ceramic resonator.The sandwich ultrasonic transducer which contains the modified 1-3-2 type piezoelectric composite material is experimentally analyzed.The frequency response curve and displacement distribution of radiation end are measured,and the influence of cutting depth on the displacement distribution of radiation distribution is analyzed.It is shown that this type of sandwitched transducer has the characteristic of pure mode,broad band in the working frequency range and well-distributed displacement.It can be widely used in high-power ultrasonic transducer and high power underwater radiator.(5)The piezoelectric properties and acoustic characteristics of the 1-3-2 type curved piezoelectric composite ceramic are analyzed,and the calculated expressions of related parameter are given.The cutting process of the 1-3-2 type curved piezoelectric composite ceramic material is emphatically researched,and the cutting and filling method is used to facture 1-3-2 type curved piezoelectric composite ceramics.The performance parameters of the 1-3-2 type curved piezoelectric composite ceramic material are measured.The underwater transducer based on the 1-3-2 type curved piezoelectric composite ceramic material is produced,and the acoustic parameters of the underwater transducer are tested in the free-field water pool.Research has shown that this type of piezoelectric composite underwater transducer has the advantages of pure mode in the working frequency range,wide beamforming at high frequency,easy way of fabrication and steady structure. |
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