PSI - Issue 75

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ScienceDirect

Procedia Structural Integrity 75 (2025) 363–374 Structural Integrity Procedia 00 (2025) 000–000

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© 2025 The Authors. Published by ELSEVIER B.V. This is an open access article under the CC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0) Peer-review under the responsibility of Dr Fabien Lefebvre with at least 2 reviewers per paper Abstract Due to trends such as increasing tower heights, optimizing the design of wind turbine towers with regard to their fatigue strength is becoming increasingly important. For this reason, all available fatigue strength potentials must be used. To be able to make use of existing fatigue strength potentials of bolting assemblies used for example in the tower flanges, the new revision of Eurocode 3 part 1-9 (FprEN 1993-1-9 (2024-02)) considers more di ff erentiated detail categories, taking into account size e ff ects, the thread manu facturing process as well as the e ff ect of zinc coatings. However, incorporating positive or negative e ff ects on the fatigue strength beyond the scope of the specified detail categories is di ffi cult, since the underlying nominal stress concept requires additional tests for any additional influencing parameter. This is a particular challenge for large bolting assemblies of nominal diameter d > 36 mm, like those used in current tower designs, as the experimental investigation of individual influencing parameters is costly and time-consuming. Compared to this, the notch-strain approach allows for the consideration of individual parameters based on the analytical or numerical calculation of local stresses and strains as well as on small-scale base material tests. In theory, changes in the bolt material, thread manufacturing process, bolt geometry, preload level, loading scenario and surface layer can be considered in one or more subsystems of the concept without the need for tests on the full-scale bolting assembly. However, the accuracy of the notch-strain approach strongly depends on the accuracy of the base material characterization as well as on the selected mod elling approaches in the di ff erent subsystems of the concept and is still a subject of research. In this context, the ongoing public funded IGF research project No. 01IF22748N, Hinrichs et al. (2025), regarding the e ff ects on the fatigue strength of large bolting assemblies (d > 36 mm) delivers extensive test results and o ff ers a large database for the validation of corresponding calculations using the notch-strain approach. The methods for the implementation, the results of the validation as well as the conclusions for the further development of the notch-strain approach for application to large bolting assemblies are presented and discussed in this paper. © 2025 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http: // creativecommons.org / licenses / by-nc-nd / 4.0 / ) Peer-review under responsibility of the scientific committee of the Fatigue Design 2025 organizers. Keywords: bolting assembly; detail category; Eurocode 3; fatigue; notch-strain approach; ring-flange connections; size e ff ect; ff ff ff ff ffi ff ff ff // / / / / ff Fatigue Design 2025 (FatDes 2025) Fatigue strength assessment of large bolting assemblies using the notch-strain approach Fritz Wegener a, ∗ , Ralf Glienke a,b , Jonas Hinrichs a , Mathias Schwarz a , Wilko Flu¨gge a,c a Fraunhofer Institute for Large Structures in Production Engineering, Albert-Einstein-Straße 30, Rostock 18059, Germany b Hochschule Wismar – University of Applied Sciences, Ph.-Mu¨ller-Straße 14, Wismar 23966, Germany c University of Rostock, Faculty of Mechanical Engineering and Marine Technologies, Chair of Manufacturing Technology, Albert-Einstein-Straße 30, Rostock 18059, Germany c

∗ Corresponding author. Tel.: + 49 381 49682-386 ; fax: + 49 381 49682-12. E-mail address: fritz.wegener@igp.fraunhofer.de ∗

2452-3216 © 2025 The Authors. Published by ELSEVIER B.V. This is an open access article under the CC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0) Peer-review under the responsibility of Dr Fabien Lefebvre with at least 2 reviewers per paper 10.1016/j.prostr.2025.11.037 2210-7843 © 2025 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http: // creativecommons.org / licenses / by-nc-nd / 4.0 / ) Peer-review under responsibility of the scientific committee of the Fatigue Design 2025 organizers. // / / /

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