Analysis Of The Plasma Oscillation And Erosion Mechanism In Electrical Discharge Channel

With the EDM-depth study, the mechanism of EDM is lagging behind to some extent restricted its further development of processing technology, not only because of the complexity and randomness of the discharge process, but also because of the insufficient understanding in motion characteristics of charged particles, electromagnetic and oscillation properties of the discharge channel.This article established the plasma channel dynamics expansion model based on the fluid mechanics motion equations of the discharge-channel expansion, combined with the other physical phenomena, such as discharge channel ionization, conductivity and radiation, solved the model and obtained the relationships between the electron density, pressure and the discharge time of discharge channel in the liquid nitrogen dielectric respectively.By the empirical formula of plasma channel configuration radius, analyzed the relationship between the electron density and the discharge time of discharge channel in the kerosene dielectric. Further, the plasma oscillation characteristics of discharge channel are analyzed: At the early stage, the plasma channel oscillation frequency decreased sharply as discharge time increases, and at the stable stage, the frequency almost keep stable; plasma channel oscillation frequency increased as the discharge voltage or discharge current increased, but decreased as the discharge gap expanded.The eigenfrequency of metal crystal lattice vibration was discovered in plasma oscillation spectrum of electrical discharge channel. The conception of atom crystal lattice resonance was put forward. At the early stage (the rising current stage), because the plasma oscillation spectrum included the frequency of metal crystal lattice vibration, the plasma resonated, or nearly resonated in the atoms on electrode surface and intensified the heat action generated by electrical discharge, which mean the atoms on electrode surface could be emitted easily. At the stable stage, the plasma frequency was below the frequency of metal crystal lattice vibration. Prerequisite for the atom resonance on electrode surface didn't exist. At the same time, the experimental results of short-pulse processing indirectly verified the electrode material surface lattice resonance intensified the heat action generated by electrical discharge, explained the early stage and a short pulse has a strong influence on electrode wear.