Modelling of short crack propagation – Transition from stage I to stage II

The propagation behaviour of short cracks under cyclic loading is simulated using a mechanism-based model for two-dimensional crack propagation in stage I. Experimental investigations on a duplex steel have been performed to characterise the different barrier effects of grain and phase boundaries, so that the crack propagation can be simulated in a real microstructure. The model allows the activation of additional slip systems resulting in a crack propagation on multiple slip bands, which is the preliminary step to stage II crack growth. By use of virtual microstructures based on Voronoi diagrams, it is possible to simulate the overall fatigue-crack propagation process starting from a microstructurally short crack in a single grain until the crack has crossed several (10–20) grains with just one model.