Effects Of Elector-hydraulic Flutter On Metal Flow Lines Of Plastic Formed Parts In Cold Extrusion

Cold extrusion technology has been widely used in electronic communication, mechanical manufacturing and other fields because of its advantages of high-quality, high efficiency, low consumption and low cost. However, in the practices of production, cold extrusion processing technology gradually revealed some disadvantages: such as high resistance to metal material deformation, easiness of the mold to be worn, short life of mold, high requirements on cold extrusion equipments, etc. To counter these problems and further develop the cold extrusion process, this paper presents a new type of cold extrusion process which introduces vibration signal in the process of cold extrusion forming. The metal flows in a closed cavity in the extrusion process, and it’s difficult to monitor and control the flow of the material and the distribution of stress and strain field, therefore it’s a hard task to precisely understand the metal flow in cold extrusion process. But research has shown that the rationality of the distribution of metal flow lines is inextricably related to the life of mold and the quality of products, and reasonable metal flow lines can prolong the life of mold, reduce extrusion defects, etc. Therefore, it is necessary to further study the metal flow lines under the condition of vibration.This paper selects a kind of forward extrusion cup part as research object, and introduces the vibration signal in traditional cold extrusion process. Based on the theory of volume effect of vibration processing, the evolution of the metal flow lines and metal mesh flow lines are simulated under two kinds of extrusion processes: with and without applied flutter. And then the two-dimensional micrograph and three-dimensional microscopic images of the metal flow lines are observed and analyzed under the two kinds of extrusion processes through experimental research. The main research contents are as follows:1. The microscopic mechanism and shaping features of metal plastic forming, and characteristics of polycrystalline plastic deformation are introduced. The basic types of cold extrusion and the impact of the cold extrusion on metal structure are elaborated. The impact of the cold extrusion on metal structure with vibration is introduced, and the volume effect of cold extrusion processing with vibration is described. The basic equation of rigid-plastic finite element, boundary conditions and the variational principle are elaborated, laying a theoretical foundation for the subsequent study and analysis of simulation and experiment.2. The traditional extrusion process and the extrusion process with vibration are numerically simulated respectively using the finite element analysis software Deform-3D, and the three-dimensional metal flow evolution and two-dimensional metal flow of cross-section grid lines under these two kinds of extrusion processes are analyzed and compared.3. Based on the characteristics of hard forming of 20 Cr forward extrusion cup part, this paper uses a kind of electro-hydraulic vibration experiment system in cold extrusion processing, and elaborates the basic components of the system and the working principle on how to realize the axial vibration in cold extrusion process.4. The metal blank and the forming parts under the two kinds of cold extrusion processes are coarse-grinded, fine-grinded, polished and corroded. The metal flow lines of forming parts are observed with scanning electron microscope(SEM), and the experimental graphs are analyzed in combination with the simulation results. The three-dimensional images of the metal flow lines are obtained using Keyence super-depth three-dimensional microscopic system, and the above analysis results are further confirmed, with emphasis on the observation and analysis of the metal flow lines in the corners of the parts.