INFLUENCE OF INITIAL BACK STRESS ON THE EARING PREDICTION OF DRAWN CUPS FOR PLANAR ANISOTROPIC ALUMINUM SHEETS

Anisotropy is closely related to the formability of sheet metal and sh ould be considered carefully for more realistic analysis of actual she et metal forming operations. In order to better describe anisotropic p lastic properties of aluminum alloy sheets, a planar anisotropic yield function which accounts for the anisotropy of uniaxial yield stresses and strain rate ratios simultaneously was proposed recently. This yie ld function was used in the finite element simulations of cup drawing tests for an aluminum alloy 2008-T4. Isotropic hardening with a fixed initial back stress based on experimental tensile and compressive test results was assumed in the simulation. The computation results were i n very good agreement with the experimental results. It was shown that the initial back stress as well as the yield surface shape have a lar ge influence on the prediction of the cup height profile. (C) 1998 Els evier Science S.A. All rights reserved.