Ductile fracture characterization of DP1000 sheet steel: Benchmarking of specimen geometries

The experimental characterization of ductile fracture in Advanced High Strength Steels (AHSS) is influenced by the choice of specimen geometry used to represent specific stress states. In this work, a comparative experimental assessment of different specimen geometries designed to represent uniaxial tension and shear-dominated stress states in DP1000 is presented. A Smiley shear specimen and two mini-shear specimens with 0 mm (‘MiniShear0’) and −1 mm (‘MiniShear-1’) offsets were used to represent shear loading conditions. For uniaxial tension, conventional Dogbone specimens and Central Hole specimens manufactured through laser cutting and electro-discharge machining were tested. Digital Image Correlation (DIC) was employed to analyze strain-field evolution, strain-path stability, and deformation proportionality throughout loading up to the assumed fracture initiation point. The results highlight significant differences between specimen geometries in terms of stress-state stability. Among the uniaxial tension stress state, the Dogbone specimen exhibited the most stable and proportional strain-path evolution, closely approaching ideal uniaxial tension conditions. For shear-dominated loading, while all shear specimens converged toward low stress triaxiality, the mini-shear geometries showed the most homogeneous strain-field behavior.