Optimization of the blankholder force distribution with application to the stamping of a car front door panel (Numisheet'99)

New materials such as dual phase steel or aluminium and complex geometries of industrial parts increase the difficulties to obtain a defect free part by stamping. One way of solution is a better regulation of the blankholder pressures. Our work is based on an original idea of Siegert, Haeussermann and Haller. The goal is to control the movement of the blank under the blankholder. Thanks to a deformable flexible blankholder, it is possible to create some independent zones. In each zone, a blankholder force can be applied on the sheet, so that a strong force can hold the blank in a zone, and a smaller one can let it move in another zone. The methodology is presented as well as some results dealing with the optimization of the blankholder force considering the drawing of a front door panel (Numisheet'99 benchmark test). The numerical simulations are performed using ABAQUS Explicit. The parameters of the finite element model (mesh density, speed of punch) are set to achieve a good prediction with a minimum simulation time. The objective function is defined to minimize the work of the punch. Three inequality constraints functions were defined to avoid necking and wrinkling. To avoid necking, the major stress of the blank is limited to a value, which is determined by using the modified maximum force criterion (MMFC). To avoid wrinkling, under the blankholder, the angle between the blankholder surface and an element of the blank is limited to a value set by the user, as proposed by Gelin and Labergere. However, in the useful part of the workpiece, the major stress is limited to a value, which was proposed by Brunet, Batoz and Bouabdallah. For the localization of the optimum, we use a response surface method computed with a diffuse approximation and coupled with an adaptative strategy to update the research space