PSI - Issue 31

Vera Friederici et al. / Procedia Structural Integrity 31 (2021) 8–14 V. Friederici et al. / Structural Integrity Procedia 00 (2019) 000–000

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The information of the slope of the linear region for a stress ratio of -1, the initial crack size and the load are later used as input parameters for the FE simulation. Number of cycles until failure for a rotation bending specimen will be calculated and compared with the experimental results. This approach will finally give an estimation for the cycles needed for crack initiation, which is difficult to determine empirically. The S-N-curves from rotating bending tests of samples with axial and tangential orientation are shown in Fig. 6. For core material the orientation has no significant influence on the fatigue strength. The hardened material has a significant higher fatigue strength. On the fractured sur faces of the rotating bending specimen the initiation site was evaluated using scanning electron microscope (SEM). In most of the cases the surface was determined as initiation site (see Fig. 1a). 3. Conclusion The measured crack propagation curves correspond well with literature data. In order to predict the cycles needed for crack initiation inside a rotating bending specimen, first the crack propagation curves for different stress ratios (R > 0) need to be transposed to a R ratio of -1. For this the linear region of the crack propagation curves were fitted using the Paris equation. The resulting predicted propagation curve for R = -1 seems to be a good assumption. Outlook: In order to predict structural failure on real parts, these results regarding crack initiation, crack propagation and fatigue strength are integrated into a crack propagation simulation developed especially for this purpose on segments of a realistic slewing bearing model. Acknowledgements The project is funded by the German Ministry of Economic Affairs and Energy (BMWi), based on a decision by the German Bundestag (Grant number: 0324303E). References Babić, M., Verić, O., Božić, Ž., Sušić, A., 2019. Fracture Analysis of a Total Hip Prosthesis based on Reverse Engineering. Engineering Fracture Mechanics 215, 261–271. Blaue, C.: Wie sicher sind Windkraftanlagen. Rhein-Neckar-Zeitung, 12.12.2018, https://www.rnz.de/nachrichten/metropolregion_artikel,-unfall in-gau-bickelheim-wie-sicher-sind-windkraftanlagen-_arid,406503.html (10.03.2020). Božić, Ž., Schmauder, S., Mlikota, M., Hummel, M., 2014. Multiscale Fatigue Crack Growth Modelling for Welded Stiffened Panels. Fatigue and Fracture of Engineering Materials and Structures 37(9), 1043–1054. Božić Ž., Schmauder S., Wolf, H., 2018. The effect of residual stresses on fatigue crack propagation in welded stiffened panels. Engineering Failure Analysis 84, 346–357. Caithness Windfarm Information Forum: Summary of Wind Turbine Accident data to 30 September 2020. 07.10.2020, http://www.caithnesswindfarms.co.uk/AccidentStatistics.htm (27.11.2020). Combrade, P., 2019. 1 - Environmentally Assisted Cracking: Some Critical Aspects. Editor(s): Christine Blanc, Isabelle Aubert, Mechanics - Microstructure - Corrosion Coupling: Concepts, Experiments, Modeling and Cases, Elsevier Science Ltd (Oxford), 1-22. DOI: 10.1016/B978 1-78548-309-7.50001-6 Dinda, S., Kujawski, D., 2004. Correlation and prediction of fatigue crack growth for different R-ratios using Kmax and Δ K+ parameters. Engineering Fracture Mechanics 71, 1779-1790. DOI: 10.1016/j.engfracmech.2003.06.001 GMN: Bearing Calculation, https://www.gmn.de/en/ball-bearings/engineering/bearing-calculation/ (27.11.2020). Murakami, Y. (Ed.), 2002. Metal Fatigue: Effects of small defects and nonmetallic inclusions, Elsevier Science Ltd (Oxford). ISBN-13: 978 0128138762 Göncz, P., Potočnik, R., Glodež, S., 2010. Fatigue behaviour of 42CrMo4 steel under contact loading. Procedia Engineering 2, 1991–1999. Kheder, A.R.I., Jubeh, N.M., Tahah, E.M., 2011. Fatigue Properties under Constant Stress/Variable Stress Amplitude and Coaxing Effect of Acicular Ductile Iron and 42 CrMo4 Steel. Jordan Journal of Mechanical and Industrial Engineering 5(4), 301-306. ISSN 1995-6665 Kujawski, D., 2001. A fatigue crack driving force parameter with load ratio effects. International Journal of Fatigue 23, 239-246. Lesiuk, G., Duda, M.M., Correia, J., Jesus, A., Calçada, R., 2018. Fatigue crack growth of 42CrMo4 and 41Cr4 steels under different heat treatment conditions. Structural Integrity 9(3), 326-336. DOI 10.1108/IJSI-01-2018-003 Lukács, J., 2019. Fatigue crack propagation limit curves for high strength steels based on two-stage relationship. Engineering Failure Analysis 103, 431-442. Schott, G. (Hg.), 1997. Werkstoffermüdung – Ermüdungsfestigkeit, Deutscher Verlag für Grundstoffindustrie (Stuttgart), 4. Auflage. ISBN 3-342 00511-4 Solob, A., Grbović, A., Božić, Ž., Sedmak, S.A. 2020. XFEM based analysis of fatigue crack growth in damaged wing-fuselage attachment lug. Engineering Failure Analysis 112, 104516.