Bewertung der fertigungstechnologischen Einflussgrößen Laserstrahlschweißen und Sintern auf die Betriebsfestigkeit

Assessment of Manufacturing Technology Influencing Factors Laser Beam Welding and Sintering on the Fatigue Strength. The fatigue strength of a laser beam welded complex engine component was assessed by the notch stress concept applying the reference radius r(ref) = 0.05 mm. By laser beam welding a sintered part and a formed steel sheet were joint together. For the assessment of the fatigue strength of both the laser beam welded joint and the material combination, component-like specimens were manufactured with varying welding parameters and material combinations. Using the results of numerical and experimental investigations on these specimens, a reference SN-curve was derived with which the fatigue strength of the engine component was assessed. A comparison of numerically assessed and experimentally determined fatigue strengths showed a good agreement, which could further be improved by using the method of the highly stressed volume

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

In the presented investigation of a laserbeam welded engine part the fatigue design methodology is shown. The fatigue critical area of the joint component is the hidden weld root which can be evaluated only by a local assessment concept. 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 rref = 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 siz e effects according to the concept of the highly stressed volume