From cut to crack: Modeling the shear-affected zone and its role in edge cracking of dual-phase steels

Sheet metal forming, particularly blanking, is essential in automotive manufacturing, shaping flat sheets into precise geometries using tools and dies. Accurate process modeling is critical to ensure defect-free production. While localized necking is commonly assessed using the forming limit curve (FLC), its application to Dual-Phase (DP) steels is limited due to edge cracking: at shear-cut edges failure occurs below the FLC and compromises part integrity. Although alternative cutting methods like laser cutting can mitigate edge cracking, shear cutting remains the most cost-effective and widely adopted method. This study investigates edge ductility in DP800 using a novel in-plane bending test on shear-cut specimens. Scanning electron microscopy and microhardness mapping reveal that blanking induces an inhomogeneous void distribution through the thickness. Crack initiation during bending occurs at the burr region, driven by high roughness, plastic deformation, and void concentration. To simulate this two-stage process; blanking followed by edge stretching; the Lou damage model is implemented in Abaqus. Remeshing and element deletion techniques are used to capture large deformation and crack evolution. The simulation reproduces key features of the fracture surface, including rollover and burnish zones, though some discrepancies remain in zone size. The 3D material edge with measured roughness was modeled. Then, state variables from the 2D blanking model are mapped to a 3D model, with Gaussian scatter added to the damage field. The model predicts fracture strain consistent with experiments, though crack initiation and propagation remain challenging to replicate precisely.