Formability of Advanced High Strength Steels Determined by Instrumented Hole Expansion Testing

摘要

The main challenges in implementing new materials for automotive applications such as advanced high strength steels (AHSS) are defined by forming, because an increase in strength is generally coupled with a decrease in material formability. One of the methods characterizing formability of sheet materials in multi-axial loading states is the hole expansion test. A parameter is proposed by a simple analytical approach in order to analyze the kinematic stabilizing effect present in hole expansion testing. Since the stabilizing effect is strongly dependent on the punch cone angle, punch cones with different angles were utilized to study experimentally the stabilizing effect on the hole expansion ratio. Specimens from industrially produced complex-phase and dual-phase steel grades were tested and analyzed. The experimental results are compared and discussed with respect to the stabilizing effect on the formability considering also the influence of the materials microstructure and mechanical properties.