Of Structural Dimensions And Material Composition Of The Band Width Of The Transducer

With more and more application of broadband sandwich transducer in power ultrasonic,the technology of widening the frequency band has become an imortant trend of the development in piezoelectric transducer.Arounding the question of frequency band, researchers adopt different methods to realizes the broad band, many of which are started from increaseing vibration mode and stimulation means,but have not brougt up a law to select material and structure size for the optimum design of broadband transducer.The sandwich transducer has been reaseerched and applied widely in power ultrasonic for the merit such as small volume,firm structure,well temperature stability,higher frequency responses and so on.The function of transducer is in close relationship with the material selection and manufacture technics, among which the bandwidth of transducer is decided by mechanical quality factor Qm. Usually, lower mechanical quality factor are hoped to widen the frequency band,by adjusting the material and structure size of ahead or back blind flange with the transducer could effectively reduce the mechanical quality factor.This paper under the the one dimension longitudinal vibration theory completely make a study of the influence on frequency band by changing the material and structure size founded on sandwich vtransducer.With the different conditions, reasonably selecting the material, length, diameter and taper of ahead or back blind flange can realize the broadband optimization.The main aspects are as follows:1. Derivate the resonance frequency equation according to the electro-mechanical equivalent circuit of sandwich transducer.Use the interface between back blind flange and piezoelectric ceramics as a referenceplane,the equivalent mass, the equivalent mechanical resistance,the mechanical quality factor at the lumped parameter system are derivated,and also calculate the frequency bandwidth.2. Only regulate the length or diameter of the back blind flange, the frequency bandwidth will change with the ratio between the back blind flange's diameter and length. The frequency bandwidth increases first and then decreases while the dimension ratio of the back blind flange increases, the bandwidth obtains optimal value just as the dimension ratio achieves at about 1. The frequency bandwidth of short and thick back blind flange is also wider than long and thin back blind flange's.3. Regulate the length and diameter of the back blind flange,the frequency bandwidth will change with the ratio between the back blind flange's diameter and length. The frequency bandwidth increases while the dimension ratio of the back blind flange increases,and the frequency bandwidth of short and thick back blind flange is also wider than long and thin back blind flange's.4. Only regulate the diameter of ahead blind flange's big or small surface, the frequency bandwidth will change with the taper, the bandwidth increases first and then decreases while the taper increases, the bandwidth obtains optimal value just as the taper achieves at 1;5. Only regulate the length of the ahead blind flange, the frequency bandwidth will change. The bandwidth increases first and then decreases, corresponds to some length,there is a best one.6. Comparing the influence of changed size in the back and ahead blind flange on the frequency bandwidth. Change in the size of ahead blind flange has a great influence on the bandwidth,and the effect on widened the bandwidth is more clearly.7. The frequency bandwidth will change with the material variation by selecting different material of ahead or back blind flange. t the frequency bandwidth is better when the ahead blind flange chooses material of hard aluminium and the back blind flange chooses material of brass.