High cycle multiaxial fatigue crack initiation : experimental observations and microstructure simulations

Abstract

This study provides an analysis of high cycle multiaxial fatigue crack initiation modes based on SEM observations.The statistical study of crack initiation preferential sites shows that grains with multiple slip have a high probability of crack initiation. The application of Dang Van criterion at the grain scale using finite element analysis (cubic elasticity with / or without crystal plasticity) on 3D synthetic semi-periodic microstructures shows a strong heterogeneity of both the hydrostatic stress and shear. The evolution of this heterogeneity introduced by the material behavior is discussed. Finally, a method based on the extreme values statistics is proposed and applied to the fatigue indicative parameter associated to the Dang Van criterion. The effects of free surface and constitutive material model were analyzed.