Finite element study on the effect of draw beads

Résumé

Draw beads are commonly used in deep drawing processes to control the flow of the blank into the die cavity during the forming operation. It works with the application of a restraining force and a frictional force. A complicated deformation process takes place as the sheet flows through the bead. Those cycles of deformation (bending/unbending) are accompanied by traction stress and bending moment of the sheet, effects who can be used to avoid different defects like wrinkles and sprigback. This paper presents a finite element study in order to identify the effects of the draw beads during deep drawing of complex parts and to establish a numerical instrument for: i). identification of the material behaviour; ii). optimisation of the effects of draw bead in order to assure the high quality of deep drawed pieces. The draw bead efficiency and effects depends on several elements: the bead penetration, the clearances between the bead and the shoulder, the shape of the bead, the radius of the bead and shoulder, the groove width, and the location of the draw bead. The presented numerical study is performed with finite element code MARC and takes account of all this parameters.