Research On The Longitudinal Piezoelectric Vibration System For Ultrasonic Grinding

With the increasing application of hard and brittle materials,such as sapphire,single crystal silicon and other materials with high hardness in nature,the traditional grinding and polishing technology has been unable to meet the requirements for the quality of the surface grinding and processing.Piezoelectric ultrasonic transducer is the core of piezoelectric ultrasonic vibration processing technology.The working principle is to realize the mutual conversion between electrical energy and mechanical energy by using the inverse piezoelectric effect of piezoelectric ceramics,it is also a key factor that determines the performance of ultrasonic vibration system.Due to the simple structure,convenient fabrication,high electromechanical coupling coefficient,and high electromechanical conversion efficiency,piezoelectric ultrasonic transducer is widely used in the fields of ultrasonic cleaning,ultrasonic detection and ultrasonic-assisted processing.Therefore,this thesis proposes to apply piezoelectric ultrasonic vibration to traditional grinding and polishing,and design a longitudinal resonance piezoelectric ultrasonic vibration system,which would improve the grinding and polishing efficiency and surface quality of hard and brittle materials.The research work of this thesis can be divided into the following parts:(1)The characteristics,application background and development status of ultrasonic vibration processing system at home and abroad are introduced.The application background and characteristics of piezoelectric ultrasonic grinding and polishing technology are introduced,and the development status of piezoelectric ultrasonic vibration system at home and abroad is summarized.The basic characteristics of piezoelectric materials and the precautions for their application are introduced.The piezoelectric equations and vibration modes are analyzed.(2)Based on the ultrasonic vibration equation and resonance design theory,the structural design and material selection of each part of the longitudinal resonance piezoelectric ultrasonic vibration system are carried out.Taking the longitudinal resonance piezoelectric ultrasonic vibration system as the research object,the mathematical model of the electromechanical coupling link is established,and the electromechanical coupling characteristics of the system are studied.The vibration frequency equation,impedance characteristic theory and electromechanical of the longitudinal resonance piezoelectric ultrasonic vibration system are mainly analyzed.The impedance can be used to calculate the electromechanical coupling coefficient of the transducer,which affects the working efficiency of the transducer.(3)Corrected the design of the stepped horn,and optimized the resonance characteristics of the longitudinal resonance piezoelectric ultrasonic vibration system.By establishing a threedimensional geometric model of the ultrasonic vibration system,the finite element software ANSYS Workbench 15.0 is used to perform modal analysis and harmonious response analysis of the theoretically designed longitudinal resonant ultrasonic vibration system.The vibration forms at different operating frequencies are analyzed.The ultrasonic resonance frequency of the transducer is 19.87 kHz and the longitudinal amplitude is 11.34?m,and the rationality of the design position of the horn node is verified.(4)For the real object of the above-designed longitudinal resonant piezoelectric ultrasonic vibration system,an impedance test is performed on the designed ultrasonic vibration system with a precision impedance tester.The test results are as follows: the longitudinal resonance frequency of the piezoelectric ultrasonic vibration system is 19.904 kHz,and the antiresonance frequency is 19.944 kHz.Compared with the theoretically designed longitudinal resonance frequency,the error is 0.48%.The electromechanical coupling coefficient is 0.06 and the dynamic resistance is 26.7?,what indicated that the conversion efficiency of the electrical energy and mechanical energy of the piezoelectric vibrator during the working process is relatively high.At the same time,the vibration characteristics of the end of the transducer in the resonance state of the transducer are tested using a laser vibrometer,and the results show that it is 10.85?m,and the error compared with the finite element simulation analysis is 4.6%,which could meet the design requirements.The ultrasonic vibration theory correctness of design and finite element simulation are verified by these parameters.Conducive to the establishment of ultrasonic vibration grinding platform and has a great significance for the engineering application of piezoelectric ultrasonic vibration grinding process.