Flat to slant ductile fracture transition: Tomography examination and simulations using shear-controlled void nucleation

Tomography examination of arrested cracks at crack initiation, flat to slant transition and slant propagation indicates a clear change in micromechanisms from high-stress triaxiality void growth to shear-dominated coalescence in the slant regime. A Gurson-type model is used and a shear void nucleation term based on the Lode parameter for strain rate is suggested for simulation of a fully meshed sample, which achieves flat to slant crack transition at loads close to experimental results for aluminium.