Development Of FEM Numerical Sinulation System And Its Application In 3-D Sheet Forming Process

In this paper, the principal theory on sheet forming and elastic-plastic finite deformation is studied firstly, and then some key techniques of static-implicit elastic-plastic FEM in sheet forming process, such as the selection of element model, the treatment of dynamic boundary conditions and oblique constraint are also discussed . On the basis above, a set of static-implicit elastic-plastic FEM system SHEET3D is developed. In this system the die surfaces are scattered into numbers of triangles, as a result, the dynamic intersection between workpiece and dies is transformed to that of line and planes, and the simulations for 3-D sheet forming process is successfully achieved. To investigate the veracity of the system developed, the drawing process of a square cup, one of the NUMISHEET'93 benchmarks, is simulated by SHEET3D. The simulation results show good agreement with the experiment and are almost the same as that of other famous software, such as LS-DYNA3D and PAM-STAMP. On the basis of its veracity investigated, SHEET3D is employed to simulate the drawing processes of cylinder and semicircle box to investigate the influence of blank size on the forming results. Then various information during the forming processes is obtained, which indicates that blanks of too large size will result in the bulging of metal at the round corner and the bottom of punch and fracture will be occurred there. Obviously, the forming results obtained through numerical simulation can be a good guidance for die design and process optimization.