Cruciform shape benefits for experimental and numerical evaluation of sheet metal formability

The optimization of sheet metal forming processes requires accurate evaluations of material forming abilities. This paper presents an original technique based on the use of a cruciform shape for experimental characterization and numerical prediction of forming limit curves. The whole forming limit diagram is covered with a unique geometry by controlling displacements in the two main directions of the cruciform shape. The test is frictionless and the influence of linear and non-linear strain paths can be easily studied. The modelling of the cruciform shape with the finite element method permits to plot forming limit curves without any calibration step, essential for the classical Marciniak–Kuczynski (M–K) model. Experimental and numerical results are presented for an aluminium alloy 5086. These results are respectively compared with the ones from classical techniques: Marciniak test and numerical M–K model.