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

The present study investigates the influence of laser cutting as compared t o 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 austeniti c and 1 of duplex stainless steels. Specimens manufactured through mechanic al and laser cutting were fatigue tested both at constant stress amplitudes and at variable stress amplitudes using a truncated Gaussean spectrum. Def ect distributions on the cut edges were measured quantitatively. The fatigu e tests showed that the fatigue strength was higher after laser cutting tha n after mechanical cutting. The relative difference was larger for the high er strength steels than for the lower strength steels. A model to predict t he fatigue strength was developed using defect distribution measurements on the cut edges combined with linear elastic fracture mechanics. The model c ould in a reasonable way describe the differences in fatigue strengths of s pecimens manufactured with the different cutting processes.