3-DIMENSIONAL FINITE-ELEMENT METHOD SIMULATIONS OF STAMPING PROCESSESFOR PLANAR ANISOTROPIC SHEET METALS

A three-dimensional finite-element method (FEM) was developed-to simul ate forming processes with arbitrarily shaped tools for planar anisotr opic sheet metals. An implicit, updated Lagrangian formulation based o n an incremental deformation theory was employed along with a rigid-vi scoplastic constitutive equation. Contact and friction were considered using the mesh-normal scheme which compatibly describes arbitrary too l surfaces and FEM meshes without depending on the explicit spatial de rivatives of tool surfaces. The consistent full set of governing relat ionships, which includes the equilibrium equation and mesh-normal geom etric constraints, was appropriately linearized. Based on membrane app roximation, linear triangular elements were used to describe formed sh eets. The non-quadratic strain-rate potential previously developed by Barlat et al. was employed to account for the in-plane, anisotropic pr operties of sheets. Numerical simulations were performed for the deep drawing of a cylindrical cup and the stamping of an automotive front f ender panel to test the planar anisotropic finite element code. In the cup-drawing analysis of a 2090-T3 aluminium alloy sheet sample, the p redicted earing profile and cup height were compared with experiments. The predicted and experimental thickness strains were in relatively g ood agreement, even though thinning trends between rolling and transve rse directions were reversed. In the fender stamping analyses of both the aluminum alloys and a mild steel sheet, the numerical stability, a ccuracy, and usefulness of the formulation were confirmed for automoti ve applications. In-plane, anisotropic effects on the forming limit cu rves are also discussed. (C) 1997 Elsevier Science Ltd.