Forming limit diagrams for anisotropic metal sheets with different yield criteria

For thin metal sheets subject to stretching under various in-plane tensile stress histories, localized necking is analyzed by using the M-K-model appr oach, and forming limit diagrams are drawn based on the critical strains fo r localization. The analyses account for plastic anisotropy, and prediction s are shown based on four different anisotropic plasticity models, which ha ve all been fitted to agree with the same set of experimental data. Situati ons where the tensile axis is along one of the orthotropic axes of the anis otropy are studied, as well as situations where the tensile axis is incline d to the orthotropic axes. Furthermore, the effect of allowing for nonzero shear strains outside the necking band is considered. In all analyses the r otation of the orthotropic axes is accounted for, and a few studies are use d to evaluate the effect of assuming the development of a plastic spin. (C) 2000 Elsevier Science Ltd. Ail rights reserved.