| With the development of ultrasonic technology, the ultrasonic vibration system with single vibrational mode can not meet some specific ultrasonic application fields. In the fields of large volume ultrasonic cleaning, ultrasonic liquid processing, sonochemistry, ultrasonic wielding and Chinese herbal medicine extraction, etc., the high power ultrasonic (HPU) vibration systems with large radiation areas are needed urgently. However, in some practical applications concerning very large ultrasonic power, it is difficult to realize the allaround ultrasonic radiation by using the one dimension longitudinal ultrasonic vibrating system. In order to improve the ultrasonic power, increase the radiation area of the single ultrasonic vibration system, and adapt to different ultrasonic preceding objects, some coupling vibration mode and mode conversion ultrasonic vibration systems are needed. For the mode conversion ultrasonic vibration system, two or more than two vibration modes are designed as its operation mode. So the design theories, analysis methods, and vibrational characteristics of the mode conversion ultrasonic vibration system are more complex than that of the single ultrasonic vibration system. Therefore, it is very useful to establish the corresponding design theories for the different mode conversion ultrasonic vibration systems in the practical engineering applications. However, in order to improve its vibration characteristics, based on the design theories, the optimization design for the geometric dimensions of the mode conversion ultrasonic vibration systems are also needed. In this paper, based on the concept of vibration conversion, some new types of HPU vibration systems are developed and the mainly contents are outlined as follows:(1)The parametric optimization design techniques of the finite element analysis package ANSYS are applied to optimize the structure dimension of the ultrasonic vibration system. The procedures for optimizing the geometric dimensions of the ultrasonic vibration system by using ANSYS are introduced. The parametric optimization design method for the ultrasonic vibration system by using ANSYS is very helpful to improve the vibration characteristics of the HPU vibration systems related in this paper.(2)Based on the concept of the vibration mode conversion, a new hollow cylinder type ultrasonic vibration system with large diameter for ultrasonic plastics welding is presented. By taking use of the conversion between the different vibration modes, the hollow cylinder type ultrasonic vibration system with large diameter can be vibrated at a higher frequency in the longitudinal-flexural-longitudinal vibration mode. The resonance frequency equations of the ultrasonic vibration system are deduced by using the theories of flexural vibration and coupled vibration. The vibration characteristics of the vibration system are investigated by the numerical method and experiment, respectively. It is confirmed that the longitudinal-flexural-longitudinal vibration is obvious and the displacement distributions of the output surface for the hollow cylinder type ultrasonic vibration system are uniform. The new hollow cylinder type ultrasonic vibration system should have good potential to be applied in ultrasonic plastics welding and the results from this paper will provide assumptions for the design of ultrasonic welding system having large diameter when the higher resonance frequency is needed.(3) A new HPU circular ring radiator is presented, which consists of a transducer, an ultrasonic horn, and a metal circular ring. Both the transducer and horn in longitudinal vibrations are used to drive a metal circular ring in a radial-axial coupled vibration. This coupled vibration can not only generate ultrasound in both the radial and axial directions, but also focus the ultrasound inside the circular ring. Based on the coupled vibration theories, the electro-mechanical equivalent circuit of the HPU circular ring radiator is deduced, followed by the calculation of the resonance frequencies for each part of the radiator by using the equivalent circuit method. Then, in order to get the best vibration and sound radiation characteristics of the radiator, the optimized geometrical dimensions of the circular ring were obtained by means of parametric optimization design techniques of the finite element package ANSYS, and the resonance characteristics and radiated pressure field of the HPU radiator were also simulated. In addition, through model analysis, except for the radial-axial coupled vibration mode, the third longitudinal harmonic vibration mode for the HPU circular ring radiator is also detected, which can be used as another operation mode due to its relative large displacement amplitude. The new HPU circular ring radiator with these two vibration modes should have good potential to be applied in liquid processing, such as sonochemistry, ultrasonic cleaning, Chinese herbal medicine extraction, etc..(4)In order to improve the ultrasonic radiation power and increase the ultrasonic radiation area for ultrasonic vibration system, a barbell horn and tubular HPU radiator is proposed and designed. The barbell horn and tubular HPU radiator is excited by a sandwiched piezoelectric transducer, then the output displacement and output area of the transducer are amplified by a barbell horn, so the tube can receive more larger excited displacement than that of output end of the transducer and the radial dimension of the tube can be designed more larger than the radial dimension of the transducer. The transducer and the barbell horn are operated to supply longitudinal vibration from the end to the tubular radiator in which the longitudinal vibration is effectively transformed into transverse radial vibration due to the Poisson's effect so that the ultrasonic energy is emitted from the tubular radiator radially. Base on the theory of coupled vibration and the transmission line theory, the electro-mechanical equivalent circuit of the barbell horn and tubular HPU radiator in longitudinal-radial coupled vibration is deduced and the resonance frequency equation is obtained. Then, in order to get the best vibration and sound radiation characteristics of the barbell horn and tubular HPU radiator, the optimized geometrical dimensions of the vibration system were obtained by means of parametric optimization design techniques of the finite element package ANSYS. Meanwhile, the vibration mode, the electro-mechanical impedance characteristics and the sound field characteristics are analyzed by using finite element, and corresponding experiments are performed to test the validity of analysis results. Due to the barbell horn and tubular HPU radiator producing and radiating ultrasonic wave by means of coupled vibration of longitudinal and radial of a tubular radiator, on the one hand, the radiator can be used as a continuous-flow ultrasonic treatment equipment which the ultrasound focused inside the tube, and on the other hand, the HPU radiator can also be used as a immersed ultrasonic treatment equipment which the ultrasonic energy is emitted from tubular radiator radially and longitudinally. The new-style barbell horn and tubular HPU radiator with large ultrasonic radiation areas should have good potential to be applied in ultrasonic sewage treatment, large volume liquid processing, ultrasonic continuous production of biodiesel and sonochemistry, etc..The main contributions of this thesis are as follows:(1)The parametric optimization design techniques of the finite element analysis package ANSYS are applied to optimize the structure dimension of the ultrasonic vibration system, and they are very helpful to improve the vibration characteristics of the HPU vibration systems related.(2) Based on the concept of the vibration mode conversion, a new hollow cylinder type ultrasonic vibration system with large diameter for ultrasonic plastics welding is presented. By taking use of the conversion between the different vibration modes, the hollow cylinder type ultrasonic vibration system with large diameter can be vibrated at a higher frequency in the longitudinal-flexural-longitudinal vibration mode. So it can overcome the big noise produced by a hollow cylinder tool with large diameter when it operated at lower frequency.(3) A new HPU circular ring radiator is presented. Based on the coupled vibration theories, the electro-mechanical equivalent circuit of the HPU circular ring radiator in radial-longitudinal coupled vibration is deduced, and its vibration mode and radiation sound field are investigated by using finite element method and experiment, respectively. It is conclude that the HPU circular ring radiator with two vibration mode can be used as a dual-frequency ultrasonic vibration system, so it can overcome the disadvantages of the single frequency ultrasound appearing standing waves in the liquid.(4)In order to improve the ultrasonic radiation power and increase the ultrasonic radiation area for ultrasonic vibration system, a barbell horn and tubular HPU radiator is proposed and designed. The barbell horn and tubular HPU radiator is excited by a sandwiched piezoelectric transducer, then the output displacement and output area of the transducer are amplified by a barbell horn, so the tube can receive more larger excited displacement than that of output end of the transducer and the radial dimension of the tube can be designed more larger than the radial dimension of the transducer. Base on the theory of coupled vibration and the transmission line theory, the electro-mechanical equivalent circuit of the barbell horn and tubular HPU radiator in longitudinal-radial coupled vibration is deduced and the resonance frequency equation is obtained. Then, the vibration mode, the electro-mechanical impedance characteristics and the sound field characteristics are analyzed by using finite element, and corresponding experiments are performed to test the validity of analysis results. Due to the barbell horn and tubular HPU radiator producing and radiating ultrasonic wave by means of coupled vibration of longitudinal and radial of a tubular radiator, on the one hand, the radiator can be used as a continuous-flow ultrasonic treatment equipment which the ultrasound focused inside the tube, and on the other hand, the HPU radiator can also be used as a immersed ultrasonic treatment equipment which the ultrasonic energy is emitted from tubular radiator radially and longitudinally.
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