| SiC has many excellent physical and chemical properties,its optical properties can be compared with optical glass,and it has become an ideal material for manufacturing optical elements,but SiC is also a kind of hard brittle material,and it is difficult to process.Ultrasonic vibration assisted abrasive flow polishing technology is one of the most effective methods for machining SiC materials.However,in the past research,due to the small gap between the polishing tool and the polished surface,the abrasive distribution is relatively scattered during polishing,and the area of single polishing is large,so it is impossible to Polish the complex irregular surface or the workpiece surface that needs small area polishing.In order to improve the polishing efficiency and quality of this kind of workpiece surface,based on the characteristics of concave spherical surface self focusing,this paper designs a set of ultrasonic vibration focused abrasive jet polishing system,which can focus the polishing fluid for erosion,and the polishing gap is large,and uses the system to carry out polishing experiments on SiC workpiece,analyzes the influence of several main process parameters on the polishing effect.Through the calculation and measurement of the acoustic field of the focused ultrasonic transducer,it can be seen that the acoustic field has remarkable focusing characteristics,and the acoustic focal length is 90 mm,which is equal to the geometric focal length.Then,based on this,the removal mechanism of the workpiece material in the polishing process is analyzed,and the principle of abrasive polishing is analyzed by the model of single abrasive impacting the workpiece surface.The analysis results show that: when the transducer When the resonance frequency and polishing target distance are fixed,the amplitude of the output end can be controlled by controlling the input voltage of the transducer,and then the movement speed of the abrasive particles can be controlled,so that the removal mode of the workpiece surface material is in the stage of plastic deformation,so as to obtain better polishing effect and surface quality.The impedance of the focused ultrasonic transducer with the installation structure is measured,and the results show that the output impedance of the focused ultrasonic transducer with the installation structure is still matched with that of the ultrasonic power source.The polishing experiment of SiC workpiece was carried out by using the designed ultrasonic vibration focused abrasive jet polishing device.The influence offour technological parameters on the polishing effect was analyzed by means of the control variable method.The results showed that the four factors all had the best technological parameters: the moving speed was 3mm/min,the target distance was90 mm,and the abrasive concentration was 20g/L,the spray angle is 45°.Under the optimal process parameters,the polished workpiece surface is more flat and smooth,the surface roughness profile curve becomes more stable,and the surface roughness value is reduced by about 70%.Therefore,the ultrasonic vibration focused abrasive jet polishing technology,a new processing method proposed in this paper,is not only feasible for polishing SiC materials,but also can effectively improve the polishing efficiency and surface quality through reasonable design of process parameters.In addition,due to the large polishing target distance and small single polishing area,there is a gap between the polishing tool and the machined surface Large gap makes it easy to polish the complex and narrow workpiece surface,which provides a new way to achieve high efficiency and precision polishing. |
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