Sectional finite element analysis of forming processes for aluminum-alloy sheet metals

The sectional finite element analysis of the forming processes for the alum inum-alloy sheet metal known to be planar anisotropic was performed. The tw o-dimensional rigid-viscoplastic FEM formulation based on the bending augme nted membrane theory as well as the anisotropic yield criteria was introduc ed. For modeling the anomalous behavior of aluminum-alloy sheet metals, Bar lat's strain-rate potential and Hill's (Journal of the Mechanics and Physic s of Solids 1990;38:405-17) non-quadratic yield theory with an isotropic ha rdening rule were employed. Furthermore, a new method to determine anisotro pic coefficients of Barlat's strain rate potential was proposed. For evalua ting bending effects in the forming process of aluminum-alloy sheet metals, the bending equivalent forces were calculated in terms of the changes in t he interior angle at a node between two linear finite elements and were aug mented to the membrane stretch forces. In order to verify the validity of s ectional finite element formulation based on the bending augmented membrane theory, the plane strain stretch/draw forming processes of a square cup te st were simulated and simulation results are compared with experimental mea surements. Friction coefficient was obtained from drawbead friction test. T he properties of selected material were obtained from uniaxial tensile test s. Simulation shows good agreement with measurements. For the application o f the sectional finite element formulation introduced in this research, the drawing process of a rear seat back upper bracket of passenger cars is sim ulated assuming plane strain condition. The thinning distribution of the si mulation agreed well with that of the measurement, so that the sectional an alysis is acceptable in the design and analysis of aluminum-alloy sheet sta mping dies. (C) 2000 Elsevier Science Ltd. All rights reserved.