Molecular dynamics simulation of the material removal process and gap phenomenon of nano EDM in deionized water

Abstract

Nano electrical discharge machining (nano EDM) is a very promising technique to fabricate nanoscale structures on superhard and difficult-to-cut materials, however, the incompleteness and imperfection of the fundamental theory seriously hinders its further application and development. In this paper, a single pulse discharge with nano EDM in deionized water was simulated to study the material ablation process and the bubble dynamic behavior using molecular dynamics. The research results showed that it was not the case that the molten material could not be removed during the discharge duration, instead it was the case that material removal would occur all the time during the whole of the discharge duration, and even after the end of the discharge molten material could still be ablated for a period of time. In addition, it was found that in the early discharge stage, the bubble expansion was impeded by a dielectric liquid, causing an extremely high pressure inside the bubble. It was also found that the expanding bubble and flowing liquid had effects on the removing, carrying, cooling and blocking of the molten and removed material. As a result, the proportion of the removed debris in deionized water was far more than that in gas, while the proportions of spattering material, returning material and bulge material were lower than those in gas, and the range of the volume distribution for the removed debris in deionized water was larger, but the range of the velocity distribution of the removed debris was lower than that in gas. In addition, the bulge generated in gas was much larger and plumper compared to the fragmentary and small bulge generated in deionized water.