Mechanism Analysis And Experimental Research On Ultrasonic Polishing Of Optical Microstructure Mould

With the development of science and technology,the application of microstructured surfaces in the field of optics is becoming more and more extensive.Among them,the compression molding process based on the replication technology can produce microstructured optical elements in large quantities and with high efficiency.In this process,the surface quality of microstructured optical components is closely related to the roughness and surface accuracy of the mold.Therefore,it is of great significance to study the polishing process of microstructure molds.In this paper,the mechanism of material removal in ultrasonic polishing was analyzed,and the distribution characteristics of pressure and cavitation under ultrasound were numerically simulated.The transducer and horn in the ultrasonic vibration system were designed and the vibration stability of the horn were analyzed,and then the ultrasonic vibration polishing experiment was carried out.The specific research contents were as follows:(1)Matlab was used to simulate the influence of different physical factors on the bubble wall motion law in the ultrasonic field;The VOF multiphase flow method based on Fluent simulated the collapse characteristics of the resonance radius cavitation under different states(different driving pressures,different cavitation-to-wall distances);The theoretical analysis of the impact of single abrasive on the wall was carried out.(2)Based on Fluent,the pressure and cavitation distribution in the processing watershed were simulated.UDF was used to simulate the ultrasonic field.The change rule of pressure and cavitation distribution in the watershed during a period was analyzed.The effects of different vibration frequency,amplitude and polishing gap on the variation law of static pressure and cavitation concentration in the V-groove flow field were compared.The pressure and void distribution in the processing basin of plane workpiece were analyzed.(3)The transducer and horn in the processing system were designed theoretically,and the modal analysis and harmonic response analysis of the horn were performed based on COMSOL,and the longitudinal resonance frequency and amplification factor of the horn were obtained.Numerical simulation and infrared thermographic measurement of the temperature rise in the vibration of the horn were carried out.The energy dissipation mechanism and temperature rise characteristics of the horn during the vibration were studied.The relationship between the temperature rise of the horn and the frequency drift were deduced.And compared with the results of the thermodynamic-modal coupling of the horn.Through numerical simulation and amplitude measurement,the influence law of temperature rise on amplitude was obtained,and suggestions for reducing the temperature rise of the horn were given.(4)H13 mold steel materials were polished by ultrasonic vibration polishing method,and the effects of abrasive grains with different particle sizes,polishing gap and polishing time on the surface roughness of the workpiece after polishing were analyzed.