Implementation of the forming limit stress diagram in FEM simulations

The purpose of the present work is the implementation of the forming limit diagrams determined by perturbation theory in FEM simulations. The computed strain distribution is compared directly with the theoretical forming limit diagrams and forming limit stress diagrams. An application of the theory is presented for sheet metal forming processes: an L-shape sheet forming process, the deep drawing of a square cup, and the deep drawing of axisymmetric cups. It has been found that the modification of the perturbation theory by a new stress–strain relationship and six-component Barlat yield criterion gives good prediction of the onset of necking. The performed experimental verification of this theory shown that the agreement between theory and experiment is good.