Advanced high strength steels (AHSS) has an increasing use in industry, mainly in the automotive industry, as they allow getting lighter and more resistant vehicle structures, meeting demands for increased safety and reduced fuel consumption. However, these steels have additional difficulties with regard to formability. One of these difficulties is related to the prediction of “local” formability. This paper investigates the parameters that influence the hole expansion capacity of a martensitic steel sheet. The hole expansion ratio (HER) is found using two geometries of punches and a variety of blank pre-hole diameters. The results show that the HER depends greatly on the punch geometry, particularly for small diameter holes, wherein the ellipsoid punch provides the best results. The HER also depends strongly on the hole diameter. These results suggest that in projects where the material is subjected to local formability conditions, the blank and matrix designs must be carefully considered in order to achieve the maximum formability conditions.

hole expansion, stretch flangeability, AHSS forming, forming limits.