Study On Ultrasonic Vibration-assisted Micro Abrasive Waterjet Cutting

Micro abrasive waterjet machining is a new nontraditional machining technology. It is widely used in many fields. However, micro abrasive waterjet cutting has some shortcomings, such as the lack of processing capacity. To solve the problems, the introduction of ultrasonic vibration as an additional power source was proposed. In this thesis, the erosion mechanism of ultrasonic vibration-assisted micro abrasive waterjet machining was studied; the effects of various experimental parameters on the material removal rate, the cutting depth and kerf width of the workpiece under the condition of ultrasonic vibration were analyzed; an ultrasonic vibration workbench was developed.The effects of various erosion parameters on the material removal rate of monocrystalline silicon (single crystal hard-brittle materials) and Al2O3, AIN ceramics (polycrystalline hard-brittle materials) were investigated. It was shown that the introduction of ultrasonic vibration can improve the material removal rate of micro abrasive waterjet erosion of hard-brittle materials. With an increase in the average abrasive particle diameter, jet impact angle, abrasive mass flow rate and jet pressure, the material removal rate of three hard-brittle materials increases. For the materials to be processed, an optimal standoff distance and an ultrasonic vibration power exists. According to their significances on the material removal rate, the experimental parameters can be ranked in a descending order as:the average abrasive particle diameter, the abrasive mass flow rate, jet pressure, jet impact angle, ultrasonic vibration power and standoff distance.The effects of the ultrasonic vibration on the micro abrasive waterjet erosion of single crystal and polycrystalline materials were discussed. The material removal rate is improved by the introduction of ultrasonic vibration. The removal of materials*Supported by National Natural Science Foundation of China (51075238). is achieved by the intersection of cracks in surface/subsurface. The cracks have small lengths and distribute densely. Ultrasonic vibration can make the hardness and fracture toughness of the materials have dynamic characteristics, and improve the material removal rate through the interference of waves, promoting of the pressure release, promoting of the cavitation erosion, weakening of the stagnant layer. In addition, for polycrystalline materials, ultrasonic vibration can promote the materials removal by enhancing the effect of intergranular fracture to improve the material removal rate. The orthogonal experiments of ultrasonic vibration-assisted micro abrasive waterjet erosion of monocrystalline silicon, Al2O3and AIN ceramics materials were conducted and the results were analyzed. Mathematical models of ultrasonic vibration-assisted micro abrasive waterjet erosion were established based on the material removal rate respectively.Problems in selections of components of ultrasonic vibration workbench were analyzed. The design process of ultrasonic horn was mainly discussed, the index-shaped ultrasonic horn of the transitional ladder was chosen. The amplification ratio, the shape factor, the resonance length and the length of each slender rod of the index-shaped ultrasonic horn of the transitional ladder were obtained by solving the wave equation. Modal analysis and harmonic response analysis of the index-shaped ultrasonic horn of the transitional ladder were conducted. Then, the multi sectional compound ultrasonic horn was developed by using the transfer matrix method. It can be found that the multi sectional compound ultrasonic horn was more suitable for the practical processing. Due to the size of the workpiece to be processed was5X5mm, the conventional clamping mode is difficult to fix the workpiece in the ultrasonic vibration condition, therefore, the vacuum clamping mechanism of ultrasonic horn was developed. The ultrasonic vibration workbench was successfully manufactured, each performance of the workbench basically meets the design requirements.Ultrasonic vibration-assisted micro abrasive waterjet cutting experiments were conducted, the effects of various process parameters on the cutting depth and kerf width of monocrystalline silicon were studied. When the average abrasive particle diameter is large, the cutting speed is small, the jet pressure is large and ultrasonic vibration power is the optimal value, large cutting depth and kerf width can be obtained. The larger the standoff distance, the larger kerf width can be obtained. But for the cutting depth, an optimal standoff distance exists.The orthogonal experiments of ultrasonic vibration-assisted micro abrasive waterjet cutting of Al2O3ceramics were conducted and the results were analyzed. According to their significances, the process parameters can be ranked in a descending order as:the average abrasive particle diameter, cutting speed, jet pressure, ultrasonic vibration power and standoff distance. Mathematical models of ultrasonic vibration-assisted micro abrasive waterjet cutting of Al2O3ceramics were established based on the cutting depth. The effects of ultrasonic vibration on micro abrasive waterjet cutting of monocrystalline silicon and Al2O3, AIN ceramics materials were studied. It was shown that the introduction of ultrasonic vibration can improve the cutting depth and kerf width and reduce cone angle of the kerf.