Novel Ultrasonic Transducer And The Radiator

There has been great development in ultrasonics in recent decades. At present, power ultrasound is widely used in many different fields such as industry, agriculture, national defense, energy, electronics, biotechnology, environmental protection, medicine, ultrasonic motor, health care ultrasonic levitation, ultrasonic chemistry, etc.The study of ultrasonic transducer is key to the application of high power ultrasound (HPU), which involves many subjects such as mathematics, mechanics, materials science, digital information processing, electronics, etc. However, with the development of science and technology, the applications of high power ultrasound become more and more wide, transducers with high efficiency; high frequency and large output power are required to meet the needs of ultrasonic applications. In order to increase the ultrasonic power and the radiation area of a single ultrasonic vibration system, some ultrasonic vibration systems of coupled vibration mode and mode conversion are designed. In this paper, based on the concept of coupled vibration, some new types of HPU vibration systems are developed and the mainly contents are outlined as follows:1. A sandwich piezoelectric ceramic ultrasonic transducer in thickness vibration is studied. The transducer consists of front and back metal masses, and coaxially segmented, thickness polarized piezoelectric ceramic thin rings. In this paper, the thickness vibration of the piezoelectric ceramic stack consisting of a number of identical piezoelectric ceramic thin rings is analyzed and its electro-mechanical equivalent circuit is obtained. The resonance frequency equation for the sandwich piezoelectric ceramic ultrasonic transducer in thickness vibration is derived. Based on the frequency equation, several sandwich piezoelectric ceramic ultrasonic transducers are designed and manufactured, and their resonance frequencies are measured. It is shown that the measured resonance frequencies are in good agreement with the theoretical results. This kind of sandwich piezoelectric ultrasonic transducer is expected to be used in megasonic ultrasonic cleaning and sonochemistry where high power and high frequency ultrasound is needed.2. A new type of high power ultrasonic radiator used in liquid is studied. The proposed ultrasonic radiator is a metal cylinder with comparative radial and longitudinal geometrical dimensions, which is mechanically excited by a longitudinal sandwich ultrasonic transducer. The equivalent circuit for the coupled vibration of the cylinder radiator is derived, and the resonance frequency equations are obtained. The coupled vibration modes of the metal cylinder radiator are analyzed and the optimum condition for the intense simultaneous resonance of the longitudinal and radial vibrations is acquired. The resonance frequency, the admittance-frequency curve, the vibration displacement distribution and the radiated acoustic field are numerically simulated and experimentally measured. It is experimentally shown that the measured results are in agreement with the analytic and numerical results, and the cylinder radiator with large geometrical dimensions can be excited into both longitudinal and radial vibration. By properly choosing its geometrical dimension, the cylinder radiator can be designed to resonate at longitudinal and radial vibration simultaneously. Therefore, it is expected to be used as high power ultrasonic radiators in ultrasonic cleaning, ultrasonic processing and ultrasonic sonochemistry.3. The vibration characteristics of rectangular plates are analyzed in theory and experiment, respectively. The resonance frequency equation for the plate with simply supported boundary is deduced, and the resonance frequency equation of thin plate in flexural vibration is given by the apparent elasticity method. The results show that the resonance frequencies of the rectangular plate are rich. Because the flexural and coupled vibration of rectangular plate is very complicated, the vibration mode and displacement distribution are analyzed by using finite element method.4. A new type of multi-frequency transducer is analyzed. The multi-frequency transducer is made of front metal mass (rectangular thick plate), back metal mass (cylinder), and piezoelectric ceramic thin rings. First, the fundamental modes of the rectangular thick plate are analyzed, and the resonance frequency equations in the radial directions are reduced using the apparent elasticity method without considering flexural and shear vibration. Second, the resonance frequency equation in longitudinal direction is derived by using the one dimensional longitudinal vibration theory. Based on the frequency equation, the transducer is designed and manufactured, and its resonance frequencies are measured. The vibration modal shapes, admittance-frequency curve, displacement distribution and harmonic response are analyzed by finite element method and experimental measurement. The results show that the new type of multi-frequency transducer has many resonance frequencies.5. The composite vibration systems with rectangular plate and longitudinal transducer are designed in this paper. Because the longitudinal vibration of transducers and flexural vibration of plate is coupled, the composite vibration system has many resonance frequencies and is designed and manufactured. Because flexural and coupled vibration of the composite vibration system is very complicated, the modal shapes, displacement distribution and harmonic response are analyzed by finite element method and experimental measurement. Theoretical simulation and experimental results are in good agreement with each other.6. The composite vibration system consisting of a transducer and rectangular thin plate with flexural vibration are multi-frequency and broadband system. Therefore, it is suitable to use the composite systems as the radiation source of cleaning tank. The modal shapes and acoustic field distribution of the two cleaning tanks are analyzed by using finite element method, and corresponding experiments are performed to validate the analysis results. The experimental results are basically in agreement with the simulation results. The composite vibration system improves the uniformity of acoustic field distribution, avoid local cavitation corrosion, increase the radiation area, etc.