In an attempt to better understand damage accumulation mechanisms in high-cycle fatigue, a 3-dimensional discrete dislocation simulation was used both to simulate the dynamic evolution of the dislocation microstructure and the topography of the free surface where the plastic deformation was localised. The numerical tool was validated by comparing the dislocation structure obtained in double slip configuration to transmission electronic microscopy observation performed in 316L austenitic stainless steel. In the case of single slip loading conditions, the stress level obtained by the dislocation simulations were found to be consistent with results from the literature. After this validation stage, results of the dislocation simulations were analysed and a mechanism for the formation of intense slip bands was deduced. Finally, the computation of the relief of the free surface showed that extrusions and intrusions develop inside the bands, which demonstrated that plastic shear alone could give raise to crack initiation.

Crack Initiation in Fatigue - Experiments and Three-Dimensional Dislocation Simulations. C.Déprés, C.F.Robertson, M.C.Fivel: Materials Science and Engineering A, 2004, 387-389, 288-291