Fatigue strength assessment of laser welded thin-walled joints made of mild and high strength steel

A database of fatigue tests taken from literature on thin-walled laser welded joints was created. Fatigue tests related to specimens made of different steel grades were considered, i.e. conventional and high strength steel, which is becoming of more concern in the automotive industry. For each specimen geometry in the database, the stress field in the notch ligament was obtained by means of finite element analysis, where the reference radius of ρf=0.05 mm was modelled. The fatigue assessment was performed by using three representative stresses: the maximum notch stress as well as the stress according to the critical distance and the stress averaging approach. For each assessment approach a regression S–N curve with a dedicated scatter band (Tσ) was obtained. The scatter was taken as measure of the assessment reliability. In addition to the assessment approach, also the effect of the base material on the fatigue strength is discussed.