Analysis of prospective SIF and shielding effect for cylindrical rough surfaces obtained by L-PBF

Fatigue properties of parts built by Additive Manufacturing (AM) are strictly related to process-induced defects and complex surface morphology. Several studies have proved that surface valleys act as crack initiation sites, similarly to surface micro-notches. However, different roughness parameters have been considered in literature for the depth of the surface notches, together with the adoption of a shielding factor. The aim of this study is to understand how the surface complexity of L-PBF (Laser-Powder Bed Fusion) AlSi10Mg cylindrical specimens in as-built condition can affect the fatigue behaviour. In detail, CT (Computer Tomography) scans were adopted to characterize the surface quality and 2D FE (Finite Element) analyses were used to calculate the local stress intensity factor at the most critical valleys in the surface. The results of the FE analyses were compared with a shielding factor determined for regularly spaced notches. In spite of the significant scatter, the average geometric factor value for surface notches in L-PBF surfaces is correctly predicted by the traditional shielding factor.