Analysis And Mechanism Study Of Discharge Channel In Ultrasonic Vibration And Magnetic Field Complex Assisted WEDM-LS

Low speed wire electrical discharge machining(WEDM-LS)is widely used in the processing of conductive materials with high hardness and melting point due to its advantages of no macro cutting force and high precision.In order to improve the efficiency,instability and surface quality of traditional WEDM-LS,the ultrasonic vibration and magnetic field are complex assisted with WEDM-LS,and study the influence through theoretical analysis and experiments.However,there is unified theoretical explanation for the processing of WEDM-LS because the complexity and randomness of liquid phase discharge.To this end,this paper takes the discharge channel of WEDM-LS as the research object,and attempts to analyze the machining process from the perspective of plasma flow and heat transfer.According to the particle orbital theory,the motion equation and electromagnetic constraint equation of electrons in discharge channel under the action of magnetic field are established.In order to describe the motion characteristics of charged particles in discharge channel accurately,the Mentecar model is introduced to modify the multi-electron motion model.The study of the parameters of discharge channel plasma shows that additional magnetic field can change the spatial shape,increase the distortion in space and the path length.And it is deduced that magnetic field can increase the total current of discharge channel.The motion of electron beam in the discharge channel is analyzed by COMSOL.The simulation results show that,compared with traditional WEDM-LS,the time from cathode to anode is increased by 15.38% and the diffusion of electrons is reduced by 5%.And the electron distribution on anode surface is more uniform at the end of discharge.In this paper,the magnetization of workpiece and working fluid,the effect of ultrasonic vibration on electrode wire and the trajectory equation of debris are analyzed.It is found that additional magnetic field causes a sudden increase in the magnetic induction intensity at cutting point of workpiece,changing the stress state of the debris.Ultrasonic vibration increase the disturbance of electrode wire to working fluid in machining gap,and improves the circulation speed of working fluid.From the analysis of the trajectory of debris,additional magnetic field increase the deflection angle,ultrasonic speed up debris removal and improve the machining state.According to the conclusion of discharge channel characteristics,combined with the temperature model of traditional WEDM-LS,the heat source model under the magnetic field is established,and the temperature field distribution of single pluse discharge on the surface of workpiece is simulated by COMSOL software.Comparing the simulation results,it is found that the crater under the action of magnetic field are large and shallow,and the volume is 1.5 times than traditional WEDM-LS.By the established material removal model and surface roughness model,it is concluded that magnetic field improve the material removal rate and obtain higher surface quality.Finally,the experiments of different working conditions are carried out.The experiments results show that ultrasonic vibration and magnetic field complex assisted WEDM-LS is superior to other three working conditions in material removal rate and surface quality.And additional magnetic field increase the current value of discharge channel,the material removal rate is 1.42 times of traditional WEDM-LS,and the error of the material removal rate prediction model is 5.3%,which verifies the correctness of the theoretical analysis.