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Numerical simulation of bead formation by an elasto-plastic finite element method (탄소성 유한요소법을 이용한 비드 성형의 수치해석)
Bead formation is a process prior to the sheet metal forming process to control the amount of draw-in in panel press forming. This process undergoes bending and geometrical non-linearity, and affects the state of binderwrap with different amount of stretching. This analysis, therefore, involves complicated stress distribution, contact phenomena and large rotation. To simulate the bead formation process, an elasto-plastic finite element formulation is derived from the equilibrium equation and related boundary conditions considering the proper contact conditions. The developed finite element program is applied to the axisymmetric stretching process, the plane strain bead formation, and the drawbead process. The validity of the present finite element program with a contact scheme is demonstrated by solving the axisymmetric stretching problem and comparing the numerical results with the reported experimental ones. The simulation of bead formation, as the 1st action state of sheet metal forming, consists of the distribution of stress and elongation with respect to various cavity dimension of the sheet. The simulation of a drawbead process, as the 2nd action state of sheet metal forming, calculates the restraining draw force from the blankholder. The numerical results provides the fundamental information to simply analyze the complex binderwrap phenomena and panel press forming.