OPTIMIZATION OF THE BLANKHOLDER FORCE WITH APPLICATION TO NUMISHEET'99 FRONT DOOR PANEL

The difficulties to achieve defect free parts in sheet metal stamping are highlighted by new materials such as dual phase steel or aluminium. Numerical simulations of the process can efficiently help to predict the behavior of the sheet by detecting defects like failure and wrinkling. A satisfactory part could be obtained by controlling the material flow during the forming phase : in some areas the sheet should be almost fixed, in others it should be let free. That control can be achieved through the blankholder pressure or the restraining forces of the drawbeads. Siegert, Haussermann and Haller [1, 2, 3] proposed the design of a deformable flexible blankholder. The aim of this work is to use numerical simulations to optimize different blankholder forces defined on different areas of the blankholder surface. The simulations are performed using Abaqus Explicit. The software is linked with an optimization algorithm based on a response surface method computed with diffuse approximations and coupled with an adaptative strategy to update the research space. The objective function is to minimize the work of the punch. Three inequality constraints functions are defined to avoid necking and wrinkling. This procedure is applied to the front door panel proposed as benchmark in the Numisheet'99 conference.