A Study Of Rigid-Viscoplastic Finite Element Simulation Of Chain Roller's Backword Extrusion Process

This thesis, combined with project "the precise forming technology and die design of chain roller", uses rigid-viscoplastic finite element method to numerically simulate the key process namely backward extrusion in roller forming, and systematic research has been done on some key questions during the process of numerical simulation.Directly focused on the character of viscoplastic material during practical forming process, based on Bingham's model, the constitutive equations of elastic-viscoplastic material and rigid-viscoplastic material have been established; an effective method has been proposed to get the viscous coefficient of different material under various conditions, and standard finite element calculating formula has been deduced through punishment function to make programming and calculation convenient. Therefore, the core question of rigid-viscoplastic finite element method has been solved.During the process of simulation, some critical questions have been effectively managed, such as acquiring the original velocity field > handling with singular point and judging convergence of iteration etc. Especially as to the problem of re-mesh, the writer does a detailed research, and handles the problem of re-mesh in roller backward extrusion with the aid of auto-mesh function of finite element software.Based on the results of simulation, analysis and research have been done to the metal flow law during backward extrusion, which offer basis to reasonable design of die and technological parameter. Predict the possible defects of production by simulation, and suggest an improved plan of the precise forming technology according to metal flow law during forming.Finally, in thesis, practical research has also been done, which demonstrate the feasibility in plan of the precise forming technology of chain roller and the reliability of numerical simulation.