Design And Experimental Study Of Non-contact Ultrasonic Longitudinal-torsional Vibration Polishing System For Sapphire

Sapphire material has been widely used in semiconductor,electronics,medical,aerospace and other fields due to its excellent properties such as wear resistance,corrosion resistance and good optical performance,and the global market scale is rapidly increasing.However,sapphire materials are hard and brittle materials that are difficult to be machined,and the traditional polishing process is gradually difficult to meet the demand of its market application.Ultrasonic processing has been proved to have unique advantages in the processing of hard and brittle materials,but at present ultrasonic processing is mainly driven by simple one-dimensional ultrasonic vibration.The ultrasonic vibration system used in ultrasonic processing needs to be further studied,and the processing technology needs to be optimized and improved.In order to solve the above problems,a two-dimensional piezoelectric ultrasonic longitudinal torsional vibration system with the integrated design of the horn and the tool head is studied and designed,and the non-contact ultrasonic polishing experiment of sapphire material is carried out.The main research contents are as follows:(1)Based on the physical properties of piezoelectric materials,the vibration mode principle of piezoelectric ultrasonic vibration system with spiral groove structure is studied,which can transform one-dimensional longitudinal vibration into two-dimensional longitudinal torsional vibration,providing theoretical basis for the design of piezoelectric ultrasonic longitudinal torsional vibration system.The material removal mechanism of non-contact ultrasonic longitudinal torsional vibration polishing is analyzed.(2)The components of the piezoelectric ultrasonic longitudinal torsional vibration system are theoretically calculated and analyzed,and the structural dimensions and material parameters of each component are obtained,so as to determine the basic structural model of the system.(3)The basic model of piezoelectric ultrasonic longitudinal torsional vibration system is established by 3D modeling software,and the finite element analysis software COMSOL multiphysics is introduced to simulate the characteristic frequency and frequency domain.The resonant frequency of the system,the amplitude of longitudinal torsional vibration output from the working face under 300 V excitation signal and the node position of the system are determined.After the simulation analysis,the complete structural model of the piezoelectric ultrasonic longitudinal torsional vibration system is determined,and then the performance of the system is tested after machining and assembling.Test the impedance characteristics of the system to determine its resonant frequency.The output amplitude of longitudinal torsional vibration of working face under 300 V voltage is measured,and the relationship between amplitude and voltage is studied.The vibration amplitude of the clamping structure at the node position is tested.The reasons for the errors are analyzed and the rationality of the errors is evaluated by comparing the test results with the corresponding simulation results.(4)The experimental materials and equipment of non-contact ultrasonic longitudinal torsional vibration polishing were prepared.The experimental platform was built and the experimental process was designed.The influences of non-contact distance,rotation speed and abrasive particle size on experimental results were studied.(5)The effects of non-contact ultrasonic longitudinal torsional vibration polishing on reducing the surface roughness,improving the surface morphology and improving the material removal rate of sapphire were studied,and the comparative experiments of one-dimensional ultrasonic longitudinal vibration driving and non-ultrasonic driving under non-contact experimental conditions were established.The experimental results show that the non-contact ultrasonic longitudinal torsional vibration polishing can effectively reduce the surface roughness of sapphire materials,improve the surface morphology and improve the Material removal rate.