| Particle Reinforced Metal Matrix Composites(PRMMCs)have excellent properties such as high thermal conductivity,high elastic modulus and high hardness,and are widely used in military and aerospace fields.However,the traditional machining method is difficult to process,and the machining efficiency is low,electrical discharge machining(EDM)is not limited by the strength and hardness of the material,it has a good advantage in the processing of PRMMCs.But,processing PRMMCs in EDM has the problem of low material erosion rate,and the erosion mechanisms for the current study is less.so in this paper,through the simulation of the melting erosion and removal process of PRMMCs material in single pulse discharge EDM,and the simulation results were verified by EDM experiments.Material erosion of PRMMCs in EDM was explored.It will play a guiding role to improve material erosion rate.(1)Study on the melting erosion process of materials in single pulse EDM.Based on the multi-phase material properties of PRMMCs and the theory of heat transfer,the discharge heat source was analyzed and the properties of the two phase materials were distinguished.A twodimensional model of single pulse discharge material melting erosion with reinforced particles uniformly distributed was established.The Solidification/ Melting model of FLUENT software was used to simulate the melting erosion process of materials under the heat source.Through the simulation results,the effects of pulse width and peak current on the temperature field,the shape of molten pool and the number of reinforced particles in the molten pool in the process of material melting erosion are studied.(2)Study on the materials removal and solidification process Based on the simulation results of material melting erosion,considering the fluid-solid coupling environment formed by molten material and solid particles,the VOF model was used to distinguish the interactions between different phase states,and the hydrodynamic model of material removal under the impact of discharge channel and gasification explosive force was established.The geometry model of discharge channel and solid particle motion is established by combining Overset mesh with SIX-DOF moving mesh.The process of material removal and solidification was simulated,and the effects of open circuit voltage and peak current on the removal of molten material and solid particles were studied.(3)Verification of simulation model.The EDM experiment of PRMMCs was carried out,compared with the simulation results,the depth of the simulated molten pool was slightly greater than that of the experimental crater,and the simulation model was relatively accurate within the allowable error range.By analyzing the surface morphology and composition of the crater,it is shown that the crater has the same characteristics as those of the simulation results.Meanwhile,reinforced particles were detected in the debris,it was proved that the molten materials could carry particles and removal them out in the interstitial medium.In summary,this paper mainly starts from the material erosion mechanism of PRMMCs in EDM,analyzes the material erosion process through simulation,and studies the influence of discharge parameters on the material erosion,the simulation results were verified by experiments.It provides a reference for further exploring efficient erosion of materials. |
PDF Full Text Request