The Bending Vibration Of The Triassic-chip Transducer Performance And Size

There are serious acoustic impedance mismatching between the solid and gas medium, since the gase medium has the low acoustic impdedance while the solid's impedance is high. The main problem in getting high efficient acoustic radiation and long-distance transmission is to solve the serious impedance-mismatch between the ultrasonic transducer and gase medium, and the problem of high absorption of the medium. The general transducers often take the way of increasing the size of the transducer to obtain a good impedance matching, a long transmission,high efficiency and good directivity. As we know the higher the frequency of the ultrasonic the better the directivity will be. Bu the absorption will increase too, and the increasion of the absorption have a negative influence on the transmission distance.Flexural vibration transducer can get a well sound impedance-match with air without increasing the transducer size. One way to get flexural vibration is the plate flexural vibrate with a longitudinal sandwiched transducer as its actuator. A amplitude transfomer is needed between the metal plate and longitudinal transducer which may icrease the size of the vibration system, though they have the high power of the sandwiched transducer and low acoustic impedance. The other way to get flexural vibration is the use of composite-double layers or three layers transducer, which is composed of piezoelectric ceramic and metal layers, including circular and rectangular shape. The piezoelectric material is brittle, and easy broken, so that it must be composed with metal in the vibrate system.The piezoelectric ceramic plate as an incentive of this vibration system,when coupled with voltage, vibrate in the radial direction,and that will lead to flexural vibration of the composite circular plates transducer and generate greater amplitude. The piezoelectric ceramic transducer of bending vibration have the advantages of simple structure, stable performance and lower acoustic impedance, and it is easy to match the external circuit and put dampers. It can generate lower resonace frequendy than a vertical thickness and radial vibration in the same geometry size. It is an ideal low-frequency resounant acoustic source, and be widely used for air coupled ultrasound transducer and water acoustic transducer.The compound transducer made of piezoelectric ceramic and metal plate layers are widely used in the today's production and engineering technology. Its vibration mode has been discribed by corresponding mathematical theories and models, the exact resonance frequency equation and the approximate numerical solution of the compound transducer with certain geometry size can be given now.With the popularization of this kind of transducer, it is necessary to study on it in depth and find the way to optimize it.In this paper, study of the transducer composited of two piezoelectric and one metal layers, considered mutual coupling of ceramic and metal plates, from piezoelectric equation and elasticity, based on the flexural vibration theory of thin plates. The follown works are did mainly:(1) Deduced the parallel and series resonance frequencies of the composited transducer with three kinds of boundaries are given by analyse of the dynam and piezoelectric equations, based on the hypothesis theory of thin elastic plate.(2) Get the series and parallel resonance frequency changing image with geometry size of the transducer under differenct doundary, using the software programme. The geometry includes the thickness and rdius of piezoelectric and metal layers. The validity of the theory foundation is verified by compareing the resonance frequency theoretical values with the finite element analysis value.