An innovative procedure for the experimental determination of the forming limit curves

Abstract

A new procedure for the experimental determination of the FLCs has been proposed. The procedure is based on the hydraulic bulging of two specimens. The upper blank has a pair of holes pierced in symmetric positions with respect to the center, while the lower blank acts both as a carrier and a deformable punch. By modifying the dimensions and reciprocal position of the holes, it is possible to investigate the formability in different strain combinations. The most important advantages of the method are the capability of investigating the entire deformation domain specific to sheet metal forming processes, simplicity of the equipment, and reduction of the parasitic effects induced by the friction, as well as the occurrence of the necking in the polar region. The comparison between the FLCs determined using the new procedure and the Nakazima test shows minor differences.