In the present study, the effects of both the microstructure and defects on the high cycle fatigue behavior of the 316L austenitic stainless steel are investigated thanks to finite element simulations of polycrystalline aggregates. The numerical analysis relies on a metallurgical and mechanical characterization. To complete the experimental study, load-controlled fatigue tests are also carried out to determine the fatigue limits at 2.106 cycles under uniaxial and multiaxial loading conditions using both smooth specimens and specimens containing an artificial hemispherical surface defect. In the finite element models, where the grain morphologies are explicitly modeled, the anisotropic behavior of each crystal is described by the generalized Hooke's law and by a single crystal visco-plastic model. From the simulations carried out with different defect sizes and orientation sets, statistical informations regarding mesoscopic mechanical fields are analyzed. Then, using the FE results, the ability of a probabilistic fatigue criterion to predict the influence of defects and biaxiality on the average fatigue limits is evaluated thanks to a comparison with the experimental data.< Leer menos