Small Power Bending Vibration Transducer Theoretical And Experimental Study

The main problems concerning the high power ultrasoncis generation and propagation in gases are the low acoustic impedance and the high absorption of the medium. As solid and gas falls far short of the acoustic impedance and therefore there are serious impedance mismatching. In order to obtain effective acoustic radiation, it is necessary to achieve a good impedance matching between the transducer and the gases. With the increasing of ultrasoncis frequency in the air,the ultrasonic absorption also increases, which lead to detect reaching of the ultrasoncis be affected. In order to obtain long-distance transmission, transducer must have high efficiency and directional. The general transducer for the realization of low-frequency sound often have to increase the size of the transducer. Bending vibration transducer can not increase the size of the transducer to get low-frequency. Bending vibration of a piezoelectric vibration of a large class , have been made use of piezoelectric vibrator bending vibration, with small in size, low frequency devices.One way of bending vibration is the use of piezoelectric ceramic plates or piezoelectric ceramic and metal components of the composite-double layers and three layers, including circular and rectangular structure. A piezoelectric ceramic transducer of bending vibration is composed by piezoelectric ceramic and metal, with low resonant impedance, it is easy to match the external circuit and put dampers, also have advantages of simple structure and stable performance. When working in low-frequency, the smaller size of its geometry,it is an ideal low-frequency resonant sound source, and also in the same geometry, it can generate lower resonance frequency than a vertical thickness and radial vibration. In order to make better acoustic matching with air impedance, the piezoelectric ceramic and metal be bonded together. Piezoelectric ceramic components as an incentive, when coupled with voltage, piezoelectric ceramics vibrate, that would make bending vibration of the composite circular plate and generate greater amplitude. Metal slice can also serve as protective film, protecting the piezoelectric ceramic electrodes and preventing from wear out and damage. It commonly is used for air ultrasound transducer and water acoustic transducer, such as sound pressure gradient hydrophone, acoustic emission sensors, ultrasound distance measure transducer and so on.In applications of the production and engineering technology, metal-piezoceramics bimorph flexural piezoelectric ceramic transducer has been widely used, its vibration mode, has been a corresponding mathematical models and theories, but very few people involved their specific components of the vibration mode and speed of measurement equivalent displacement observation. And at present, the study on piezoelectric ceramic and metal composition of the piezoelectric vibration, most have overlooked the piezoelectric ceramic and metal sheets between the coupling effect. In this paper, have considered mutual coupling of ceramic and metal films, from the piezoelectric equation and elasticity of the campaign equation, based on plate bending vibration theory, the theoretical research and experimental testing of bimorph flexural piezoelectric ceramic transducer be carried on. Mainly to do the following work:â‘ From the piezoelectricity equation and elasticity theorys equation of motion, the strict frequency equation of composite piezoelectric vibration under free, fixed-edge and simply supported boundary condition has been given, and the correctness has been verificated by experiment.â‘¡By useing the software programmethe relationship between the resonant frequency, the effective electromechanical coupling coefficient and thickness and radius of piezoelectric ceramics and metal are calculated, the optimum design of geometric parameters is obtained. the specific size with the highest effective electromechanical coupling coefficient under certain frequency also is obtained.â‘¢The finite element analysis of vibration mode of piezoelectric vibrator for different boundary conditions are carried on, then compare with model from the displacement of vibration and experiment.â‘£In accordance with theoretical analysis, several transducer have been processed, its frequency and amplitude has been tested, the displacement of the vibration has also been tested and analysed by laser-measuring instrument.