Evaluation of in-plane edge stretchability under severe contact condition for third-generation advanced high-strength steel

This paper newly proposes a practical example to evaluate the edge stretchability of third-generation advanced high-strength steel and conventional GPa-grade steels under an in-plane edge stretching when blanking holding force is applied. Edge stretchability of third-generation advanced high-strength steel was evaluated by a sheared edge tension test in terms of a strain at failure, work hardening, and fracture morphology. An edge stretching mechanism in B-pillar was examined by the numerical simulation, which is applied to design the practical example. To maximize the edge stretching without an undesired fracture excluding the sheared edge, new design concept for the draw-beads was systematically implemented in a proposed practical example for effectively controlling the material inflow. Experimental validations of the practical example were carried out under three different sheared edge conditions produced through flat blanking, humped bottom blanking, and waterjet cutting. These were verified by comparing the sheared edge tension tests with utilizing a digital image correlation technique in terms of strain at the failure.