K alle Lipiäinen

LUT University, Lappeenranta, Finland

Kalle Lipiäinen works as a postdoctoral researcher in the Laboratory of Steel Structures, LUT University, Lappeenranta, Finland. His research has focused on performance of ultra-high-strength steels. The main interest on research is the effects of local quality and geometry on the fatigue performance. The research combines experimental testing and characterizing local properties, from various techniques incl. cutting, welding, post-treatments, surface coatings and additive manufacturing etc., to understand cyclic loaded component behavior.


Laser based powder bed fusion (L-PBF) manufactured components are typically used in weight-critical cyclically loaded applications. Building orientation and parameters have a substantial influence on the fatigue performance. A multiparametric method, namely the 4R method, was applied for evaluating the fatigue test data of high-strength L-PBF specimens, including a consideration of local quality. The analysis considering local quality with fractography identified and measured quality characteristics is demonstrated with unnotched and notched specimens with additional stress concentration factor (SCF). The results suggest that the local quality, influenced by the building characteristics, can be assessed when local stresses are obtained from finite element analysis considering the theory of critical distances (TCD). The fatigue strength assessment of notched components benefits from the consideration of local cyclic behavior with the 4R method by improving the accuracy of assessments. As a result of this study, a multiparametric method for fatigue strength assessment approach with a master FAT curve was proposed for additively manufactured components.


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