Thermal-Fluid Coupling Simulation And Experiment Of Single Pulse Discharge Process

Electrical discharge machining(EDM)uses the instantaneous ultra-high thermal erosion between bipolar electrodes to make the workpiece materials melt and vaporize,and then form discharge crater.In the process of material removal,the processed material that is heated to melt or vaporize or re-solidify involves hydrodynamic problems,which will affect the temperature of the discharge area to further change crater growth.Therefore,the thermal-fluid coupling simulation and monopulse discharge experiment are applied to study the discharge crater of single discharge,and the characteristics of the corresponding temperature field and fluid field distribution as well as the formation process of the discharge crater are further analyzed.Firstly,the thermal fluid coupling model of spark single pulse discharge process is established,and the level set method is used to track the formation of discharge crater and the growth process of crater morphology.The distribution and variation of temperature field and fluid field in the crater area are studied and the growth rule of the crater is gained.The results show that the molten material will first form a smooth depression at the center of discharge area,and then be pushed to the outsides and etched away continuously,at the same time,flanging bulges appear around the crater.Secondly,the distribution of temperature field and flow field in the discharge crater area under different discharge conditions were simulated.The effects of different discharge current,pulse width and their comprehensive effects,as well as different tool electrodes and workpiece electrodes on the discharge crater were analyzed.The results show that the difference of crater morphology under different discharge conditions is related to the difference of surface temperature distribution caused by the influence of the thermophysical properties of electrode materials and discharge energy.Finally,the central composite experiment is carried out to study the process parameters such as discharge current,pulse width and open circuit voltage,which affects the discharge crater morphology characteristics.The second-order response model of processing parameters to crater radius is obtained.The consistency of the morphology and size between the experimental crater and the simulation crater and the fitting effect of different discharge crater models are compared to verify the rationality of heat fluid coupling.