Study On The New Technology And Mechanism Of Ultrasonic Vibration Aided Electrical Discharge Machining In Gas

In this dissertation, the charge forming and moving process in the gas media EDM is analyzed on the basis of Tangseng theory. The theory that ions collision in gas media between the electrodes will change to bright light is introduced. The characteristics of the disruption of gas medium in high pressure are analyzed. The conductance and disruption of gas medium are analyzed systematically in uniform electric field and non-uniform electric field. The process of disruption for gas medium between a tip electrode and a plate electrode is studied experimentally, especially the non-uniform electric field. The difference of the disruption of the gas in different voltage and different shape of the tool electrode is observed. The voltage to disrupt the gas increased with the increase of the radii of the tool electrode tip. The experimental results show that the disruptive discharge gap is related to the shape of the electrode if the voltage is definite.The results of theoretical analysis and experiment show that the ultrasonic vibration can enhance the material removal rate (MRR). And the ultrasonic vibration can improve the quality of the workpiece surface. The results from the experiment show that the recast layer of the surface of the workpiece machined by the way of UEDM in gas is smoother than by the way of traditional EDM. And the recast layer is thin than that of the surface machined by traditional EDM. The results observed through the SEM show that the dent machined by UEDM in gas is smaller than that machined by traditional EDM. The recast layer is thin and displays less micro cracks on the workpiece surface with ultrasonic vibration aided electrical discharge machining compared with conventional electrical discharge machining.The heat conduction process is analyzed in paper. The mathematic model and expression of the heat conduction process with the changing of the parameters and the phase change is constructed. The problem of the phase change is solved by the method of equivalent specific heatThe temperature fields of one pulse machining are simulated. The changes of the temperature fields and the shapes of the dents with the changing of the power density and the time are simulated. The results show that the ratio of the depth to the diameter of the dent becomes larger with the extending of the discharge time. But it changes little with the increase of the power density with the discharge time. So with the enhancement of the power density and the extending of discharge time, the machining becomes more efficient. If we want to get fine surface, we should shorten the discharge time. These results can give beneficial direction in our practice.The effect of machining parameters on material removal rate is studied experimentally. Experimental results show that the material removal rate increases with the increase of dischargecurrent, discharge voltage and pulse duration time, and decreases with the increase of discharge pulse interval. The experimental results are similar with the theoretical formula and the simulation results. The surface roughness increases with the increase of discharge current, discharge voltage and pulse duration time.