Simulation of simplified zigzag crack paths emerging during fatigue crack growth

When subjected to fatigue loading, microstructurally short cracks form zigzag shapes in single shear mechanisms due to nucleation, glide and annihilation of dislocations. Such crack progression is geometrically complicated and computationally expensive to model. This paper investigates the possibilities of efficiently modelling such growth behaviour by geometrical simplifications of the zigzag path. The crack path and the emerging plasticity was modelled by two different dislocation formulations and it was found that, irrespective of dislocation modelling technique, a valid geometrical approximation was to disregard the surface roughness except for the zigzag section closest to the crack tip.