Numerical approach of cyclic behaviour of 316LN stainless steel based on a polycrystal modelling including strain gradients

• A numerical strain gradient modelling based on GNDs is proposed.
• Simulations are performed on a 316LN stainless steel 3D aggregate.
• Our non-local model can predict fatigue behaviour right from tensile curves data.
• For fatigue loading, GNDs decrease the local stresses within polycrystals.
• Simulations of grain size effect on monotonic and fatigue loadings are performed.

A non-local polycrystal approach, taking into account strain gradients, is proposed to simulate the 316LN stainless steel fatigue life curve in the hardening stage. Material parameters identification is performed on tensile curves corresponding to several 316LN polycrystals presenting different grain sizes. Applied to an actual 3D aggregate of 316LN stainless steel of 1200 grains, this model leads to an accurate prediction of cyclic curves. Geometrical Necessary Dislocation densities related to the computed strain gradient are added to the micro-plasticity laws. Compared to standard models, this model predicts a decrease of the local stresses as well as a grain size effect.