Characteristics Of Sandwich Longitudinal-flexural Vibrating Transducers And Its Finite Element Analysis

Multimode coupled vibration research of ultrasonic transducer has become a hot topic in recent years. Because coupled vibration has both disadvantages in transducer output characteristics and advantages in transducer designation. Recently, many people have done a lot of work on multimode coupled vibration research, such as longitudinal-radial coupling and longitudinal-flexural coupling of cylinder and multidimensional coupled vibration of big size pendulum. The author has done studies on two kinds of vibration coupling of muti-pendulum and analyzed its vibration characteristics.The author loaded a thin disk on the front of longitudinal vibration transducer. Longitudinal vibration made the disk flexural vibrate. Then the longitudinal-flexural coupling vibration transducer has been designed.(1) At first, the frequency equation of disk' s flexural vibration was deduced under the theory of thin board's flexural vibration. Rn has been calculated when the material is aluminum. Then using frequency equation, the author calculated various frequencies of longitudinal-flexural vibration disk which has certain size. The result shows that the frequencies of various stages are quite different. In this research, equivalent mass and equivalent elastic constant were deduced, and the equivalent circuit diagram was drawn as well.(2) Longitudinal vibration transducer was analyzed. Using the equivalent diagram, the author designed longitudinal vibration transducer which had the same frequency as the fundamental frequency of disk's flexural vibration. The high stages' frequencies were also calculated under frequency equation. The result shows that various frequencies have very large differences.(3) Using the theory of sandwich transducer, the author analyzed the combination coupling vibration of longitudinal vibration transducer and thin disk. The equivalent circuit diagram of this coupled transducer was drawn. The equivalent elastic constant was deduced and then the resonant frequency equation of coupled transducer was deduced. Resonant frequencies of the transducer which has the mentioned size were calculated by computer. This resonant frequencies' difference was compared with that of single pendulum. The result shows that the frequencies differences of this transducer are much less.(4) The thesis introduced transducer imitation designation by ANSYS. When the radium of the front disk was enlarged or the thickness of the disk was reduced, the simulated data shows that the differences between fundamental frequency and high stage frequencies were further reduced.The result shows that longitudinal-flexural coupled vibration can diminish the differences between fundamental frequency and high stage frequencies. When the size of radiation head is changed, multi-frequency can be realized and the bandwidth may even be enlarged. The author hopes this thesis may have some help to the designation of multi-frequency or broadband transducer.