Molecular dynamics simulation of material removal process and crystal structure evolution in EDM with discharge on different crystal planes

Abstract

The extensive application of electrical discharge machining (EDM) in the manufacturing industry and the advancement of EDM towards the micro-nano fields make the incompleteness and imperfection of fundamental theory in EDM a more acute problem and even become a huge bottleneck, hindering its further application and development. In this paper, single-pulse discharges on the {100}, {110}, and {111} planes were simulated to study the material removal process, crystal structure evolution, and influence of crystal plane. The research results show that during the discharge process, there generated high pressure inside the melting area, which makes the melting material expand outward and the swell was formed (forming process of swell). When the pressure inside the melting area overcame the bonding force among atoms, the swell broke open and the material started to depart from the electrode surface (blasting process of swell). In addition, it was found that after the end of discharge, there existed the stacking faults, dislocations, and vacancies or interstitial defects inside the electrode. The crystal defects mainly existing in the denatured layer had direct relation with the formation of cracks on the discharge surface. It was also found that the crystal plane had influence on the material removal process. Specifically, the volume of the discharge crater and bulge, the depth of crater, and the occurring moment of the material ablation on the {111} > {110} > {100} plane indicated that the machining on the {111} plane was the easiest while on the {100} plane was the hardest. However, the crystal plane had hardly any influence on the melting and solidifying process of material, and the occurring moment of material ablation was not equal to the melting moment of material, but later than the melting moment.