Study On The Sandwich Piezoelectric Transducer In Flexural And Longitudinal-flexural Composite Vibration

Because of its excellent performance,longitudinal vibration and flexural vibration sandwich piezoelectric ultrasonic transducer is widely used in ultrasonic processing,ultrasonic wire harness welding,ultrasonic scalpel,ultrasonic vibration cutting and ultrasonic motor.However,the traditional longitudinal and flexural piezoelectric transducers have some disadvantages,such as narrow acoustic radiation range,single vibration mode or vibration direction,which can’t meet the increasing needs of human beings.Therefore,a sandwich piezoelectric ultrasonic transducer with double flexural vibration head and two dimensional orthogonal structure is proposed,which realizes the structural innovation,vibration mode innovation and performance improvement of the transducer with flexural and flexural composite vibration.The main research contents include the following aspects:(1)Based on the flexural theory of Timoshenko beam,the transfer matrix theoretical model of double-excited stepped flexural vibration sandwich piezoelectric transducer is established.The first four order flexural vibration characteristics of the transducer are calculated and analyzed by using the transfer matrix theory model,finite element simulation software and experimental sample test.The results of the first four order flexural vibration modes from the theoretical calculation,finite element simulation and,experimental test are in good agreement with each other.The effective electromechanical coupling coefficient of the transducer is large in low order flexural vibration modes,and small in high order flexural vibration modes.The diameter ratio of the stepped front cover plate has a great influence on the first four order flexural resonance frequencies and the amplification coefficients of the transducer.The larger the diameter ratio is,the lower the flexural resonance frequencies and the larger the amplification coefficients are.The length ratio of the stepped front cover plate has little effect on the first four order flexural resonance frequencies and amplification coefficients.(2)Based on the theory of the side flexural,this paper proposes a double curved sandwich type piezoelectric ultrasonic transducer,and the corresponding calculation model with the transfer matrix theory,The results from the calculation model,the finite element simulation,and the experimental test are in good agreement.The frequency response curve of the transducer and the displacement curve are also analyzed.The proposed transducer increases the flexural radiation range of one-dimensional single-head flexural transducer to a certain extent.Stepped type horn is adopted to enlarge the radiation range of flexural to a greater extent.The results show that the flexural modes are different with the different polarization modes of the piezoelectric ceramics.Under the same polarization mode of the two groups of piezoelectric ceramics,the flexural modes of the transducer show a symmetric mode,and simultaneously contract or stretch upward or downward.Under the different polarization modes of the two piezoelectric ceramics,the flexural mode of the transducer exhibits an antisymmetric mode,with one end contracting and the other end stretching,presenting an inverted S-shape vibration.(3)The longitudinal and flexural composite sandwich piezoelectric transducer is proposed,and the theoretical model of the transducer is established on the basis of the previous two parts,and compared with the finite element simulation and experimental test,the results have a high coincidence rate.The vibration displacement of the transducer is monitored by three-dimensional transversal,and the vibration characteristics of the transducer are confirmed by experimental measurement of displacement amplitude.At the same time,the influence of height and material of transducer center block on vibration performance is studied.Different from the traditional transducer,the transducer transforms the flexural and longitudinal vibration through the central coupling block to realize the longitudinal and flexural composite vibration of the transducer,which not only expands the vibration mode of the transducer but also broadens the ultrasonic radiation space.Piezoelectric transducer is proposed in this paper can effectively solve the existing sandwich,there exist the ultrasonic radiation direction of a single ultrasonic transducer,ultrasonic radiation area is small,and problems such as too complex structure,implementation of the existing single excitation source,longitudinal and single flexural vibration of the single layer type ultrasonic transducer structure and the vibration mode of innovation and the improvement of the performance of the transducer vibration,It provides reference value for the research and application of multi-dimensional multi-mode transducer.