Influence of drawbead geometry and blank holder force on the dual phase steel formability

Mostly, stamping industries, especially the automobile, uses a single machine to manufacture several parts. As a result, a time to try out stamping tools to start a new production cycle is often necessary. To reach the expected degree of satisfaction for the product, the tryout involves: choosing a material with better formability, adjustments in the design of punches, dies, and components that assemble the tooling. For this, the development of laboratory tests, which allows a better understanding of material stamp-ability and the influence of tooling parameters, become essential for smooth preparation for production and the development of more accurate computational models. Given these challenges, the present work studies the influence of the drawbead geometry and the blank holder force (BHF) on the stampability of DP780 steel. For this, an interchangeable drawbead system was developed for a Nakazima test tool. The four drawbead geometries were used: flat (without salience projection), circular, triangular, and square. In addition, three-level of BHF were used. For each set of drawbead geometry and BHF, the forming limit curve (FLC) of DP780 steel was obtained and analyzed. From the results, it was possible to observe the best configuration of drawbead and BHF. Furthermore, the results showed clear gains in formability and the influence of drawbead geometry and BHF on the DP780 stamping.