Ultrasonic Field Analysis Of Polishing Based On Two-dimension Vibrating Liquid And Experimental Research

With the development of microelectronics and optics, the requirements for surface precision of materials are increasingly stricter, including low surface roughness (up to nanometer level) and low residual stress. Polishing based on two-dimensional vibrations of liquid (PTDVL) is a novel surface polishing method that is proposed on the basis of these requirements. PTDVL uses fluid to serve as polishing pad and insert two-dimensional high-frequency ultrasonic to supply polishing energy. In the polishing process, the workpiece is immerged in polishing liquid and moved in planetary motion, at the same time, particles suspending in the liquid will brush the workpiece continuously, then materials of the workpiece will be removed by the operation of sound pressure which brought by ultrasonic vibration.In this paper, based on the existing experimental device and theory, the effect of ultrasonic physics on polishing performance are researched. First of all, the output characteristics of ultrasonic transducers are tested, hydrophone and staining method are also employed to analysis the sound intensity distribution in polishing vessel. The results show that ultrasonic is well coupled when input voltage varied from 150V to 200V, furthermore, sound intensity is distributed evenly and power enough to polishing in the very range. Velocity of particles and that of micro jet caused by cavitation are also calculated in terms of the test results.Sound pressure simulation is performed by MATLAB to get more detailed information of the whole sound field. From the simulation results it could be found that since the uneven distribution of sound pressure, the existing device is just suitable for polishing workpiece with small acreage.Optimum design of the experimental device is carried out to satisfy the polishing requirement of large-acreage workpiece. Both the locations of transducers and workpiece-clamping fixture are redesigned for the purpose of eliminating standing wave and enhancing the uniformity of sound pressure distribution. Experimental researches, including single element experiments and orthogonal experiments are performed on glass and silicon. From the single element experiments it could be found that better experimental results obtained when input voltage is 180V and the concentration of polishing liquid is 10%; the best polishing time is 180min for glass and that is 360min for silicon; moreover, for silicon polishing, alkali solution could be added in the liquid to enhance polishing efficiency.Orthogonal experiments is carried out on silicon for the purpose of studying the combinative effect of different elements to polishing performance, as the result, the optimum team is obtained, these are 200V (input voltage); 10% (concentration of polishing liquid); 360min (polishing time), which is nearly like the single element experiment result.