Fatigue performance of fiber laser fusion cut edges on thick plates

Abstract

Fatigue performance of cut edges is an important factor in structural design, especially when geometrical stress concentration factors (SCFs) are present. High power laser cutting systems have enabled efficient and fast fusion cutting with nitrogen as an assistant gas. The fusion cutting induces recast layer, which features crack-like defects close to cut edge. In this study, plates with thickness 16 ≤ t ≤ 30 mm have been fatigue-tested. A 10 kW fiber laser cutting system was used to cut plates with nitrogen as an assistant gas. High strength steel (HSS) S690 specimens included unnotched coupon specimens and welded T-profile with longitudinal gusset in post-weld treated conditions, where laser cut edge was found critical. Fatigue performance of S690 cut edges were found close to 170 MPa m = 3 when SCFs of welded specimens were included on analysis. Local properties at the cut edge including hardness measurements and scanning electron microscope (SEM) fractography. Fractography obtained local quality use with theory of critical distances -based fatigue strength assessment was demonstrated.