Mechanism And Temperature Field Simulation Of Ultrasonic Vibration Assisted EDM

Efficient machining of micro holes has always been one of the problems to be solved in the field of machining.The EDM technology has obvious advantages in micro hole processing,mainly because in the processing,the tool and workpiece do not directly contact,will not produce force.But there are also some limitations,such as unstable discharge state,difficult chip removal and so on.Ultrasonic assisted EDM technology can effectively solve some problems of EDM.In EDM,the surface roughness is related to the peak current and pulse width.In order to obtain higher surface quality,the peak current and pulse width must be reduced,that is,the discharge energy of single pulse must be reduced.Accordingly,the material removal rate will also decrease,that is,the material removal rate and surface roughness are a pair of contradictions.In EDM,effective deionization is needed.In order to improve the material removal rate,reduce the surface roughness and deionize in time,the mechanism and temperature field of ultrasonic vibration assisted EDM are studied.Firstly,the mechanism of ultrasonic vibration assisted EDM is studied.Ultrasonic vibration can improve the state of inter electrode discharge gap and make the discharge channel easier to form;Based on the free collision theory,on the one hand,ultrasonic vibration causes molecules in the discharge channel to collide with each other,on the other hand,it causes secondary electron avalanche process,forming self-sustaining discharge;Ultrasonic vibration can enhance the explosive force of spark discharge;Ultrasonic vibration can also accelerate the movement speed of the corrosion products between electrodes,promote them to discharge from the discharge channel,and improve the circulation and deionization state of the coolant.The temperature field distribution of the workpiece during ultrasonic EDM is also studied.In order to explore the mechanism of material erosion in ultrasonic vibration assisted EDM(ultrasonic vibration assisted EDM),the influence of discharge parameters on the amount of electrode material erosion is studied based on the heat conduction theory.The temperature field distribution of workpiece material is analyzed under different pulse width and peak current by using finite element method,and the temperature field distribution of workpiece under Gaussian heat source is obtained.In the process of simulation,the relationship between material thermal physical parameters,discharge channel radius and electrical parameters,anode energy distribution coefficient,phase transition and heat flux load are fully considered,and the corresponding relationship between the radius,depth,depth diameter ratio and material etching volume of the pit and single pulse width,peak current is obtained.The simulation results show that when the pulse width increases,the radius and depth of the pit will increase steadily,but the growth trend will gradually slow down,and the depth growth rate is smaller than the radius growth rate,which also leads to the slow down of the growth rate of the deep diameter ratio.When the peak current increases,the pit radius shows a smooth growth trend,while the pit depth increases obviously in the initial stage,and then slows down slightly.Compared with the volume of material removal,it can be seen that the peak current has a greater impact on the removal of materials.The results show that the material removal rate increases with the increase of current,and the removal rate of the material with ultrasonic vibration is 2.1 times higher than that of the single EDM.To sum up,this paper analyzes the mechanism of ultrasonic vibration assisted EDM,and studies the distribution of workpiece temperature field under single pulse by numerical simulation,which can provide theoretical support for precise control of energy,setting of electrical parameters and process improvement of ultrasonic EDM.