Stage-II fatigue crack growth model from 3D dislocation dynamics simulations.

Stage-II fatigue crack propagation in FCC metals is investigated using 3D discrete dislocation dynamics (DD) simulations. The calculations show that dislocation/grain–boundary interaction affects slip dispersion everywhere in the grain, including in the crack tip region. The results are analysed and drawn in the form of simple, quantitative mathematical expressions, depending on a set of physical variables. This approach helps in developing a comprehensive crack propagation model, where the crack growth rate da/dN depends on both the crack tip opening displacements and the tip-related nucleation of nano-cavities. It is shown that the modelled crack response is compatible with the well-known Paris expression, which we further interpreted as a ratio between the energy stored in the tip region over the energy spent extending the crack surfaces. The model validity is finally evaluated by a comparison with relevant experimental evidence. [ABSTRACT FROM AUTHOR]