Numerical analysis on the local mechanical fields in polycrystalline 316LN stainless steel under cyclic fatigue loading: Comparison with experimental results

The present paper is devoted to the study of the parameters responsible for the initiation and/or propagation of transgranular microcracks in polycrystalline materials. The investigation is carried out on an aggregate made of 316LN stainless steel which 3D grain shape and orientation were reconstructed using 2D serial Electron BackScattered Diffraction scans. The evaluation and the analysis of the local mechanical fields at the free surface of the polycrystalline aggregate subjected to cycling loading are performed using Finite Element Crystal Plasticity. Two crystal plasticity models are used and compared through Finite Element computations: quasi-physical or phenomenological models. The local parameters which possibly drive crack initiation are analysed and then compared to the experimental observations. A new criterion predicting whether a specific grain is likely to present a fatigue crack initiation is finally proposed.