Fatigue assessment of laserbeam welded PM steel components by the notch stress approach

The local fatigue strength of a laserbeam weld of a complex engine component, which joins a PM with a formed sheet component, was assessed by the notch stress concept with the fictitious reference radius of r(ref) = 0.05 mm. First, simplified specimens, following the main geometric dimensions of the parts, were manufactured. On these specimens the fatigue strength was identified by tests and the notch stresses calculated by finite element analysis. Based on these results a design SN-curve was derived to assess the fatigue strength of the engine component. The numerical assessment of the welded joint was verified by proof tests with the component. The assessment could be improved by considering statistical and stress gradient dependent size effects according to the concept of the highly stressed volume.