Hydration-assisted Ultrasonic Abrasive Flow Polishing Technology On Sapphire Microcavity

Microcavity structures play an increasingly important role in chemical reactions,biological analysis,and medical testing.Sapphire has great application value due to its unique physical,chemical and optical properties.However,due to current technology,the inner surface quality of the processed sapphire microcavity structure cannot meet the practical application requirements,and can only be expected in other ultra-precision machining methods.In this paper,the surface quality of sapphire microcavity structure is improved.Considering the high hardness of sapphire material and small microstructure size,this paper proposes a hydration ultrasonic assisted abrasive flow polishing sapphire microcavity method.The processing principle of this method is based on The sapphire hydration property can reduce the surface hardness of the material,and the inner surface of the sapphire microcavity structure is polished by the abrasive particles driven by the high frequency ultrasonic wave.The details are as follows:Firstly,based on the sapphire hydration modification reaction principle,the hydrated modified layer was analyzed,the structural composition and hardness were Mohs hardness and thickness,and the optimal hydration modification parameters were determined.Combined with the theory of fracture mechanics,the material removal method of sapphire is plastic removal,and there is no brittle removal.At the same time,according to the establishment of the micro-body force model,the ultrasonic vibration flow field theory is analyzed,and the single abrasive grain material removal is first established by Herz theory.The mathematical model derives the material removal function of the abrasive flow and the abrasive flow material removal function under ultrasonic vibration conditions.Then,the 3D model of the micro-cavity structure was established by Pro/e software.The Gambit software was used to mesh the 3D model,and the boundary conditions were set.Then the FLUENT software was used to analyze the temperature distribution of water vapor in the optical micro-cavity: when the inlet velocity was 0.1m/s,when the external heating temperature is 200 degrees,the water vapor temperature in the micro-channel reaches 150 degrees or more,which meets the hydration reaction temperature requirement.Secondly,the velocity and pressure of the abrasive flow in the sapphire micro-cavity are analyzed by Fluent.Distribution law: When the abrasive flow rate in the micro-cavity channel is v=0.1m/s,the abrasive flow field in the micro-cavity channel is stable,the pressure difference at the corner is reduced,and the constant pressure region is reached,which can make the abrasive evenly Distributed in various areas of the cavity.According to the schematic diagram of hydration-assisted ultrasonic abrasive flow polishing,a test device was designed,in which a special composite horn was designed for the sapphire microcavity structure,and the modal analysis was carried out to determine the design.The three-factor four-level L16 orthogonal test platform was designed to carry out the polishing test to explore the influence of ultrasonic power,liquid abrasive particle size and processing time on the surface roughness of the sapphire microcavity.In the test,the roughness difference before and after processing was calculated as the expected target.The DOE module in MINITAB was used to analyze the signal-to-noise ratio response and the mean response of the experimental data.The two methods obtained consistent results: the polishing effect of each process parameter The improved contribution degree is: ultrasonic generator power,processing time,abrasive particle size;when the ultrasonic power is 600 w,the abrasive particle size is 1um,and the polishing time is 4 hours,the surface roughness of the sapphire microcavity can be realized before polishing.The change of 0.476 um is 0.282 um after polishing,which is reduced by 34%,and the influence of various process parameters on the polishing effect is obtained.The response surface analysis shows that the optimal surface can be realized by increasing the power of the ultrasonic generator and prolonging the processing time.