Molecular dynamics simulation of single pulse discharge process: clarifying the function of pressure generated inside the melting area in EDM

Due to the unique and superior properties of using thermal energy to machine electrically conductive material regardless of its hardness, electrical discharge machining has been widely used and has become indispensable in the manufacturing industry. However, the incompleteness and imperfection of the fundamental theory behind it seriously hinders its further application and development. In this work, a single pulse discharge in deionised water was simulated to study the material removal motivity and mechanisms with molecular dynamics simulations. The results show that during the discharge process, there exists a decreasing pressure gradient along the depth direction towards the surface of the melting area. When the pressure gradient overcomes the atomic bonding forces, the melting material can be ablated from the electrode. Thus, it is not the case that the melting material cannot be removed during the discharge process; material removal occurs throughout the whole discharge process. In addition, it was found that the bulge is formed for two reasons: the main reason is the shearing flow of the melting material caused by the pressure gradient along the radial direction in the melting area, and the other is the accumulation of the spattering material from the opposite electrode.