The sectional analysis of the forming processes for aluminium-alloy sheet metals was performed. The 2-dimensional rigid-viscoplastic FEM formulation based on the bending-augmented membrane theory as well as the anisotropic yield criteria was introduced. For modeling the anomalous behavior of aluminum alloy sheet metals, Barlat's strain rate potential and Hill's non-quadratic yield theory with an isotropic hardening rule were employed. Furthermore, the new method to determine anisotropic coefficients of Barlat's strain rate potential was introduced. For evaluating bending effects in the forming process of aluminum-alloy sheet metals, the bending equivalent forces were calculated in terms of the changes in the interior angle of two linear finite elements and were augmented to the membrane stretch forces. In order to verify the validity of FEM formulation, the forming processes of a square cup and a rear seat back upper bracket of passenger car were simulated.
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