Effects of Using Flexible Die Instead of Flexible Punch in Rubber Pad Forming Process

Flexible forming with rubber pad is a forming technique that is commonly used in the aeronautic and automotive industries to produce parts with complex shapes from thin sheet metal. The purpose of this chapter is to compare between using flexible punch or flexible die in sheet metal forming with rubber pad. A finite element simulation is carried out to predict the behavior of the flexible stamping process of aluminum sheet metal with the two techniques of forming. For the sheet metal, an elastoplastic constitutive model is adopted and implemented in ABAQUS/Standard software via UMAT subroutine. However, a Mooney–Rivlin hyperelastic model is adopted for the rubber pad. Results predicted numerically consist of comparing the variation of some key parameters process using two deformation styles in order to produce safety parts without localized severe deformation. It was found that using rubber as flexible die may reduce the thinning rate and values of equivalent plastic strain in the formed part. Also, based on the Forming Limit Diagram (FLD) analysis, using flexible die instead of flexible punch may successfully form part without necking and micro crack and without localized severe deformation that can lead to fracture.