On the influence of crack front curvature on the fracture behavior of nanoscale cracks

Atomic-scale fracture processes are traditionally investigated in quasi-2D models of straight, infinite cracks. This approach neglects crack front curvature effects, which might be particularly important for nanoscale crack nuclei in semi-brittle materials. Here we use 3D atomistic simulations to study penny-shaped cracks in body-centered cubic metals. Our results show extensive crack tip plasticity initiated by deformation twinning and followed by emission of screw dislocations which cross-slip along the crack front. Together with the interactions of dislocations and/or twins that are nucleated at differently oriented parts of the crack, these processes determine the fracture behavior of highly curved nanoscale cracks.