Shakedown limit of 316L stainless steel manufactured by laser powder bed fusion based on crystal plasticity enhanced direct cyclic analysis

Fatigue modelling of metals is essential for accurate prediction of fatigue strength and fatigue life which ensures structural integrity and reliability. The fatigue performance of additively manufactured metals, such as laser powder bed fusion (PBF-LB/M) 316L stainless steel (SS), is highly dependent on the microstructure, making microstructural sensitive models crucial for the modelling. To overcome the expensive computation by traditional incremental analysis, crystal plasticity enhanced direct cyclic analysis was performed to efficiently predict the shakedown limit, i.e. fatigue limit, of PBF-LB/M 316L SS in this work. Statistically equivalent representative volume elements (SERVEs) of the two materials produced with different preheating platform temperatures were generated considering the features of grains and lack of fusion defects. The model parameters were determined and calibrated at microscopic and macroscopic levels. The effect of different dislocation cells on the critical resolved shear stress (CRSS) was incorporated in the model. The statistics of the shakedown limit of the SERVEs show that the defects and the surrounding complex grain interaction resulting from the differences in orientations, shapes, and CRSS comprehensively determine the shakedown limit. The shakedown limit of the two materials is compared with respect to the hierarchical microstructure. A preliminary correlation between the modelled fatigue limit, the CRSS, and the material porosity is proposed. This work advances microstructural sensitive fatigue modelling to improve the fatigue limit prediction for PBF-LB/M 316L SS in aerospace, transportation and medical applications.