Simulation And Experiment Research On The Mechanism Of Piezoelectric Self-adaptive Pulsed Electrical Discharge Machining

In recent years, with the deeper research and continuous improvement on the mechanism and equipment of electrical discharge machining (EDM), the technology of EDM has developed rapidly. Piezoelectric self-adaptive pulsed EDM is a new EDM process proposed by our research group. In this new process, low voltage direct current power is used as power source. In order to realize the self-adaptive control of discharge gap along with the state of pulse discharge, the energy generator and the gap adjusting device are organic integrated together. The innovation point of piezoelectric self-adaptive pulsed EDM is adjusting discharge gap between tool electrode and workpiece electrode through adjusting length of tool electrode according to the state of pulse discharge based on the converse piezoelectric effect of piezoelectric ceramic, so as to improve discharge frequency and effective utilization of pulse discharge, and then, as a result, obtain higher machining efficiency of EDM.Our research group has designed and manufactured the equipment of piezoelectric self-adaptive pulsed EDM, and also has studied its machining system and process performance, but little research has been done on its mechanism. Therefore, based on the work mentioned above, the mechanism of piezoelectric self-adaptive EDM is studied through finite element method (FEM) and experiment in this paper. Particle flow in discharge channel, temperature field and stress field of piezoelectric self-adaptive pulsed EDM are researched by FEM. The predicted precision of FEM model is verified by the single pulse discharge experiment. Chief research contents are as follows.The research on motion characteristic of charged particle in discharge channel is an important part in EDM mechanism research. Particle-in-cell plus Monte Carlo collision method are used to set a electromagnetic model, and then the electromagnetic model is used to simulate the particle flow in discharge channel of piezoelectric self-adaptive pulsed EDM. The movement and distribution of charged particles in discharge channel are obtained. Density and kinetic energy of discharge particles on any cross section of discharge channel are both Gaussian distribution approximately.Heat flux density distribution formula of Gaussian heat source model on the electrode surface is derived based on calculating the energy of the electrode surface and discharge channel radius. Heat conduction equation in the cylindrical coordinate system is derived by analyzing the key problems of the heat source model.The temperature field and stress field of single pulse discharging in piezoelectric self-adaptive pulsed EDM are simulated by ABAQUS. The law of discharge voltage values and adjustable capacitor values influencing temperature field distribution of piezoelectric self-adaptive pulsed EDM is given; and the stress field distribution on the surface and the inner of workpiece are also obtained. The maximum stress is got on the border of adjacent discharge channels.Based on the piezoelectric self-adaptive pulsed EDM device which is constructed by this research group, single pulse discharging experiment is done under different discharge voltage and adjustable capacitor. The comparison between the results of simulation and experiment is done. The predicted precision of the finite element simulation (FES) model is verified by the experiment. Its predictive error is within15%, and meets practical engineering requirements.The result, which is obtained from the mechanism research of piezoelectric self-adaptive pulsed EDM, provides theoretical basis for the further research and development of the piezoelectric self-adaptive pulsed EDM process. The mechanism research in this paper is of benefit to popularization and application of the piezoelectric self-adaptive pulsed EDM process.