FE Analysis on Deformation Mechanism of Strain-Rate-Sensitive Materials in Cylindrical Deep-Drawing with Combination Punch Speed and Blank Holder Control

In the sheet stamping of strain-rate-sensitive materials, the forming limit is governed by punch speed (SPD) as well as blank holding force (BHF). In previous research, a combination control algorithm for simultaneously varying SPD and BHF was proposed to achieve high-speed deep-drawing. In this study, finite element (FE) simulation is conducted for circular-cup deep-drawing with combination SPD/BHF control in order to reveal the deformation mechanism of the improvement of deep-drawability. The numerical results demonstrate that even though the blank material has a low strain-rate dependence at room temperature, the drawability and production rate can be improved by properly varying SPD/BHF. It is found, from the simulation results, that a relatively low SPD with a low BHF in the early forming stage causes less thickness reduction at the punch shoulder. In the middle-to-last stage, therefore, the remaining blank can be successfully drawn into the die cavity with SPD and BHF higher than the critical constant SPD and BHF.