Technology And Mechanism Of Rotary Ultrasonic Assisted EDM For Metal Matrix Composites

Metal matrix composites(MMCs)is a new type of materials with wide development prospect..High silicon aluminium alloy is a typical metal matrix composite material.Its silicon content is more than 17%.It has the advantages of low density,low thermal expansion coefficient,good thermal stability,high specific stiffness and strength,corrosion resistance and non-toxicity.It is widely used in automobile manufacturing and aerospace industry.However,when the silicon content of high silicon aluminium alloy increases continuously,its brittleness characteristics will increase accordingly,which will lead to a significant reduction in the machinability,and it is difficult to meet the processing requirements in general mechanical processing.Electrical discharge machining(EDM)is a non-contact process without obvious macro-force.It is suitable for processing high silicon aluminium alloy.Rotating ultrasonic vibration assisted EDM is a kind of composite machining technology.In this paper,the processing mechanism of rotary ultrasonic-EDM technology for high silicon aluminium alloy is studied.The traditional theory of EDM is deeply studied,which includes discharge channel,gap between electrodes,ejection of etch product and deionization of dielectrics between electrodes.At the same time,combined with the characteristics of ultrasonic vibration,the effects of rotating ultrasound on discharge channel,gap between electrodes,dielectric de-ionization and processing efficiency in EDM are studied.It is found that rotating ultrasound can significantly improve the discharge situation and the processing efficiency.Based on ANSYS simulation software,the temperature field in single pulse EDM process is simulated.The influence of interelectrode voltage,discharge current and pulse width on temperature field distribution in EDM of high silicon aluminium alloy was studied.The relationship between interelectrode voltage,discharge current and pulse width and the depth,radius and volume of dents in EDM was analyzed with the improved material removal rate formula.Through simulation and analysis,it is found that the interelectrode voltage,discharge current and pulse width are positively correlated with temperature rise,and the effect of current is more prominent.A rotary ultrasonic-EDM machine tool is developed,which integrates electrode rotation,ultrasonic vibration and EDM.The contrast experiment of high silicon aluminium alloy with and without rotating ultrasonic condition and the single factor experiment of the influence of peak current,discharge voltage and pulse width on pit removal volume under the two conditions were carried out on the compound machine tool.Comparing the experimental results,it is concluded that rotating ultrasound can improve the processing efficiency and surface quality of workpiece,improve the discharge gap and promote the removal of material etchants.The results of single factor experiments show that the volume of etching pit increases with the increase of discharge current,voltage and pulse width,and the increase trend is more significant with the assistance of ultrasonic vibration.With the increase of these three electrical parameters)the discharge energy of single pulse increases,so the volume of pit erosion increases.This trend is consistent with the simulation results,which verifies the reliability of the simulation results.