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The propagation of short fatigue cracks is simulated in the microstructure of an
austenitic-ferritic duplex steel by means of a mechanism-based model. Due to
strong interactions with microstructural features, such as grain and phase
boundaries the growth rate of these short cracks is substantially non-uniform. The
strength of these barriers has been quantified by a Hall-Petch analysis and the
findings have been implemented into a two-dimensional model for stage I crack
propagation, which considers the orientation of available slip systems and can
predict the crack growth in a real microstructure. The model allows the activation
of secondary slip systems at the crack tip resulting in a crack propagation on
multiple slip bands. To study the effect of a misorientation between two slip
planes on crack propagation the stress field at the tip of a surface crack is
calculated using a three dimensional extended crack model. Crack growth
simulations carried out with the model show good agreement with experimental
data.