Effect of cutting method on the fatigue strength of high strength sheet steels

摘要

In steel sheet structures, fatigue cracks can initiate at several different locations such as at joints, sharp press radii and at cut edges. The present paper focuses on fatigue properties associated with crack initiation at cut edges. The fatigue properties of steel sheet are investigated after cutting either laser cutting or conventional mechanical punching. Three grades of steel sheet were included in the study; one deep drawing steel and two high strength steels of which one was a dual phase steel. Specimens manufactured through punching and laser cutting were fatigue tested at constant stress amplitudes. The experiments showed that the fatigue properties were improved through laser cutting as compared to the mechanical cutting methods. The difference was larger for the dual phase steel than for the two lower strength steels. A model to predict the fatigue properties was proposed using cut edge defect distribution measurements combined with linear elastic fracture mechanics. The model could in a reasonable way reproduce the experimentally determined fatigue strength levels