Deep drawing of square pieces with variable tribological conditions on the flange

Abstract

The research results of blank holding force (BHF) influence on the process of plastic forming are presented in this paper. BHF is the normal force and very important factor of friction on the flange. BHF control enables friction control and in that way significant influence on the forming process. Geometry of the work piece is prismatic with square cross section. Material is standard deep drawing thin sheet (0.8 mm thickness). BHF has constant intensity, on one side (based on common recommendations and performed optimization) and, on other side, regime of decreased intensity with constant specific contact pressure. Coefficient of friction is dictated by application of: dry surfaces, oil for deep drawing and polyethylene foil with oil. The following properties are monitored: main surface strains distributions and their relationship to forming limit diagram, thickness strain distribution, change of final deep drawing depth and change of forming forces. If there is final drawing depth (without any defects) as main criteria for successful forming process this research clearly shows significant possibilities of BHF influence on improvement of square pieces deep drawing process results.