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Abstract: Degenerated shell element and membrane element have been widely applied in thin sheet metal forming analysis. However, for medium thick plate metal forming, especially in the case of typical double-sided contact problems such as local bulge forming or pure bending with a small radius, these two element models cannot accurately simulate normal extrusion deformation of the sheet metal. In this paper, a new finite element (FE) solver based on the solid-shell element dynamic explicit algorithm and implicit algorithm is developed for the simulation of medium thick plate metal forming and springback. The solid-shell element model considers bending effects with a thickness-direction multiple-point integration approach. The viscous damping hourglass control algorithm eliminates the spurious deformation modes activated by in-plane reduced integration (RI). The double sided contact analysis considering thickness variation describes the extrusion deformation in the thickness direction accurately. An improved plane-stress constitutive model in co-rotational configuration together with Hill''s quadratic anisotropic yield criterion is employed to update the stress field. The solid-shell element obtains both solid-like and shell-like behaviours to simulate large membrane deformation, shear deformation and rotation. To test the performance of the solid-shell element, some numerical examples are taken and compared with experiments. The comparison results demonstrate that the solid-shell element model is competitive enough in the simulation of medium thick plate metal forming and springback. [Copyright &y& Elsevier]

Abstract: The paper discusses the application of a finite strain model to predict springback in sheet forming. The concept combines both isotropic and kinematic hardening and utilizes a new algorithm based on the exponential map. A special focus is put on the simulation of the draw-bend test of DP600 dual phase steel sheets and the comparison of the numerical results with experimental data. Further, we investigate the sensitivity of the results with respect to geometry parameters as the tool radius and the sheet thickness as well as the ratio between isotropic and kinematic hardening. In addition, the model is applied to the S-rail benchmark problem and the thermoforming of thermoplastic blends, where large elastic strains occur. The simulation results match the experiments very well. [Copyright &y& Elsevier]

In this paper, an implicit simulation code which can simulate a general three-dimensional sheet-metal forming is presented. An 8-node degenerated shell element is employed to approximate the continuous updated Lagrangian formulation of the global mechanical problem. Emphasis is put on expressing the contact conditions and taking into account the geometrical non-linearity. The characteristics of the authors’ contact algorithm is that the contact conditions just act as the boundary conditions of the FEM equations and need not be introduced into the stiffness matrix. Finally, two numerical examples demonstrating the effectiveness of the present approach are given. [Copyright &y& Elsevier]