The influence of mechanical and laser cutting on the fatigue strengths of carbon and stainless sheet steels

Abstract

The present study investigates the influence of laser cutting as compared to conventional mechanical cutting on the fatigue properties of steel sheet. 6 grades of steel sheet were included in the study; 1 deep drawing steel, 2 high strength steels of which 1 dual phase steel, 2 variants of austenitic and 1 of duplex stainless steels. Specimens manufactured through mechanical and laser cutting were fatigue tested both at constant stress amplitudes and at variable stress amplitudes using a truncated Gaussean spectrum. Defect distributions on the cut edges were measured quantitatively. The fatigue tests showed that the fatigue strength was higher after laser cutting than after mechanical cutting. The relative difference was larger for the higher strength steels than for the lower strength steels. A model to predict the fatigue strength was developed using defect distribution measurements on the cut edges combined with linear elastic fracture mechanics. The model could in a reasonable way describe the differences in fatigue strengths of specimens manufactured with the different cutting processes.