PSI - Issue 5

Maria Paarmann et al. / Procedia Structural Integrity 5 (2017) 869–874 M. Paarmann et al / Structural Integrity Procedia 00 (2017) 000 – 000

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5. Conclusion

Because of the strong fluctuation of the energy supply, the fossil power plants are cyclically loaded. For assure a safe life, residual lifetime calculations must be performed. On the example of a ball-shaped part, numerical crack growth simulations were made using FRANC3D. Next to mechanical loading, pure thermal loading with different temperature gradients were applied. The results show a large dependency of the SIF from this gradient. Moreover, the thermal loading leads to stresses over the wall thickness, which results in a decreasing SIF over the crack depth. As opposed to this, the SIF of pure mechanical loading rises with crack propagation. The numerical results were also used for lifetime prediction. Therefore, experiments were made to determine temperature dependent crack growth parameters using the FORMAN/METTU equation. On the example of pure mechanical loading the influence of temperature was investigated by applying the parameters for different temperatures. Based on high threshold values, crack growth would not start until high crack lengths. Moreover, the results show a higher crack growth rate for high temperatures. Acknowledgements The authors thank the German Ministry for Economic Affairs and Energy for funding the joint project THERRI (English: Determination of characteristic values for estimating thermal fatigue crack growth in power plants, German: Ermittlung von Kennwerten zur Bewertung thermischen Ermüdungsrisswachstums in Kraftwerken) Further, the authors greatly acknowledge the support by the partners TÜV NORD SysTec GmbH & Co. KG, the chair of Technical Thermodynamics at the University of Rostock, the KNG power plant Rostock and the research institute Jülich. References Chen, Q., Kawagoishi, N. and Nisitani, H. (2000) ‘Evaluation of fati gue crack growth rate and life prediction of Inconel 718 at room and elevated temperatures’, Materials Science and Engineering: A , 277(1-2), pp. 250 – 257. doi: 10.1016/S0921-5093(99)00555-9 Mutschler, P. and Sander, M. (2016) ‘Investigation of fatigue crack growth in a power plant steel under elevated temperatures’, Procedia Structural Integrity , 2, pp. 801 – 808. doi: 10.1016/j.prostr.2016.06.103 Paarmann, M. and Sander, M. (2016) Numerische Untersuchungen zur Rissausbreitung in Kraftwerkskomponenten für betriebsnahe Belastungsszenarien . Petit, J., Henaff, G. and Sarrazin- Baudoux, C. (1999) ‘Mechanisms and Modeling of Near -Threshold Fatigue Crack Propagation’, Fatigue Crack Growth threshold, Endurance Limits, and Design, ASTM STP 1372 . Schulz, A. et al. (2014) Prüfkonzepte für ermüdungsführende Komponenten unter den Bedingungen eines flexiblen Kraftwerksbetriebes (SIC – Smart Inspection Concept), 46. Kraftwerkstechnisches Kolloquium 2014. Oktober 2014. Test Method for Measurement of Fatigue Crack Growth Rates (2015). West Conshohocken, PA: ASTM International. UEMATSU, Y. et al. (2008) ‘Effect of temperature on high cycle fatigue behaviour in 18Cr– 2Mo ferritic stainless steel’, International Journal of Fatigue , 30(4), pp. 642 – 648. doi: 10.1016/j.ijfatigue.2007.05.004