PSI - Issue 75

Ralf Glienke et al. / Procedia Structural Integrity 75 (2025) 474–488

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Ralf Glienke et al. / Structural Integrity Procedia 00 (2019) 000 – 000

4. Discussion - For constructional details, whose fatigue strength benefits from blast-cleaning, improvement factors k Imp would be desirable. - Further welded details as well as steel grades and in particular the effect of compressive loads, should be part of systematic investigations in the future. - In case of butt-welded joints with post-treatment such as ground flush to surface or blast-cleaning, internal defects can become decisive for crack initiation. It would be necessary to derive maximum detail categories based on fracture mechanics for typical defects for the use of suitable NDT methods that reliably detect internal defects. - Lifting the design S-N curve for blast-cleaned butt-welded joints to a level above DC 125 appears to be possible without material removal by grinding. The weld toe is improved by the abrasive effect and cold forming, which induces work hardening and compressive residual stresses. Therefore, a reliable fabrication inspection is required to avoid internal defects, as described in Lotsberg (2025a). - Full description of the two-slope S-N curve for blast-cleaned butt-welded joints by variable amplitude fatigue testing is still pending. Alternatively, a derivation of S-N curves from fracture mechanics, see Lotsberg (2025b), would be conceivable. An experimental validation of this possibility should be carried out. - Thermally cut edges generally benefit from blast-cleaning treatment. However, for cut edges with higher surface roughness, the potential for improved fatigue strength increases. - For non-welded constructional details, the FKM approach provides better agreement with the test results in terms of higher fatigue strength, which is justified by the consideration of the steel grade alone. In contrast to the welded details and thermal cut edges, the fatigue strength of components with holes decreases by applying a blast-cleaning treatment. The reason for this is insufficient work hardening with a simultaneous increase in surface roughness of the hole. References Ahola, A.; Lipiäinen, K.; Risii, J.; Koskimäki, M.; Pyörret, J.; Björk, T. (2023): Fatigue strength of shot‑peened as‑welded joints and post‑weldtreated and subsequently clean‑blasted fillet weld joints. In: Welding in the World 67, S. 1559 – 1574. DOI: 10.1016/j.ijfatigue.2024.108711. IEC 61400-6/AMD1 ED1, 2024: Amendment 1 – Wind energy generation systems – Part 6: Tower and foundation design requirements. Bannister, A.; Skalidakis, M.; Pariser, A.; Langenberg, P.; Gutierrez-Solana Salcedo, F.; Sánchez, L. et al. (2006): Performance criteria for cold formed structural steels. Report EUR 22056 EN. European Commission - Directorate-General for Research. Bartsch, H.; Citarelli, S.; Feldmann, M. (2023): Generalisation of the effective notch stress concept for the fatigue assessment of arbitrary steel structures. In: Journal of Constructional Steel Research (201), S. 1 – 8. DOI: 10.1016/j.jcsr.2022.107715. Bartsch, H.; Seyfried, B.; Hofmann, G.; Feldmann, M.; Ummenhofer, T.; Kuhlmann, U. (2024): Bewertung wesentlicher Einflussgrößen auf die Ermüdungsfestigkeit typischer Kerbdetails - experimentelle Untersuchungen. In: Stahlbau 93 (5), S. 330 – 342. DOI: 10.1002/stab.202300079. Bignonnet, A.; Lieurade, H. P.; Picoute, L.; Castex, L. (Hg.) (1987): Shot peening on welded joints and residual stress relaxation during fatigue. International Conferences on Shot Peening. Garmisch-Partenkirchen. EN 13001-3-1, 2019: Cranes - General Design - Part 3-1: Limit States and proof competence of steel structure. ISO/TR 16060, 2014: Destructive tests on welds in metallic materials — Etchants for macroscopic and microscopic examination. ISO 17639, 2022: Destructive tests on welds in metallic materials - Macroscopic and microscopic examination of welds. Deutscher Ausschuss für Stahlbau (2019): DASt-Richtlinie 026. Ermüdungsbemessung bei Anwendung höhenfrequenter Hämmerverfahren: Stahlbau Verlags- und Service GmbH. Diekhoff, P.; Hensel, J.; Nitschke-Pagel, Th.; Dilger, K. (2020): Investigation on fatigue strength of cut edges produced by various cutting methods for high-strength steels. In: Welding in the World 64, S. 545 – 561. DOI: 10.1007/s40194-020-00853-y. ECCS (2018): Background information on fatigue design rules. Statistical evaluation. 2nd edition. Brussels (European Convention for Constructional Steelwork).