Numerical prediction of the forming limit diagrams of thin sheet metal using SPIF tests

Sheet metal formability is usually limited by the occurrence of damages evolution, leading to a localized necking failure. The Forming Limit Diagram (FLD) is widely used for characterizing the formability of metal sheets. This paper aims to predict numerically the forming limit diagram using the 3D simulations of the micro-Marciniak tests with different width. A conventional Lemaitre ductile damage model with isotropic hardening is used to predict the strain hardening and the necking point. The identification of the ductile damage model is first performed from micro-single point incremental forming tests using inverse finite element method. Then, the micro-forming limit curves in terms of strain and stress are plotted in the major/minor strain space and major/minor stress space, respectively. Finally, the effect of the initial grain size on the forming limit curves is investigated. (C) 2017 Published by Elsevier Ltd.