Robust fatigue design and its relation to basic research

Real machine components must serve for 20 or 30 years under various conditions. The transferability of modern fatigue results obtained in the laboratory to industrial practices requires a thorough understanding of the underlying physics and stochastic processes yielding the observations. Of the modern fatigue theories, the cyclic R-curve has proven to be especially interesting, quantifying the crack closure development and non-propagating crack sizes. In this talk, the use of cyclic R-curve in the analysis of extensive experiments with artificial defects and non-propagating cracks is discussed.

Speaker: Joona Vaara, Wärtsilä (Helsinki, Finland)

Biosketch: Joona Vaara is a senior structural analyst working for Wärtsilä R&D since 2013.

Influence of defects on the high and very high cycle fatigue strength

With increasing strength, metallic materials become highly sensitive to defects under cyclic loading conditions. Even very small defects such as nonmetallic inclusion and microstructural inhomogeneities can lead to the initiation of fatigue cracks that may cause fracture after high and very high numbers of load cycles. A basic understanding of the influence of defect size and geometry is essential for a safe design of components and structures against fatigue failure. Based on comprehensive experimental results, an overview of the failure mechanisms of defect-induced fatigue failure is given, and prediction approaches based on fracture mechanics as well as notch-fatigue principles are discussed.

Speaker: Bernd M. Schönbauer, Institute of Physics and Materials Science, BOKU University (Vienna, Austria)

Biosketch: Bernd Schönbauer is senior scientist and lecturer at the Institute of Physics and Materials Science, BOKU University, Vienna, and the head of the Christian Doppler Laboratory for Defect Tolerance of Steels in the High and Very High Cycle Fatigue Regime. After receiving his PhD on the subject of corrosion-fatigue of steam turbine blade steels from TU Wien, Austria, in 2014, he was working as a postdoctoral research fellow at the Institute of Materials Science and Technology, Fukuoka University, Japan, in 2015-2016. Since 2018, he is Adjunct Professor at the Faculty of Technology, University of Oulu, Finland. His area of expertise is fatigue and fracture mechanics with focus on defect tolerance, loading condition and environmental effects in the high and very high cycle fatigue regime. Dr. Schönbauer´s research activities resulted in numerous publications in academic journals and conference proceedings as well as oral presentations at scientific conferences. He has been PI of several research projects funded by the European Union, national funding agencies and the private sector.