The Effects of AHSS Shear Edge Conditions on Edge Fracture

Abstract

Edge cracking is one of the major issues for stamping Advanced High Strength Steel (AHSS). This type of cracking is influenced by three major factors: the material property, the die condition and the shearing/blanking process. The current shearing/blanking process has been applied to traditional mild steels for years and has not been modified for shearing AHSS. Other than the high energy laser cutting process, the traditional die cutting process would generate a rough edge (burr) with micro cracks in shearing/blanking edges for AHSS, which could serve as the crack initiation during forming. This study is to investigate the effects of shear edge conditions on edge cracking for AHSS. A special hole shearing process has been developed on a laboratory hydraulic press. Different shearing parameters, including die clearance, cutting angle and material orientations, were investigated in terms of shear edge conditions. The hole expansion test was conducted to evaluate the effects of shear edge conditions on the material edge stretchability. Results showed that an optimal selection of die clearance and shearing angle can greatly increase the edge stretchability for AHSS.