PSI - Issue 57

Gloria Hofmann et al. / Procedia Structural Integrity 57 (2024) 452–460 Hofmann, G.; Bartsch, H.; Kuhlmann, U.; Feldmann, M.

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Three conclusions can be drawn from this information. First, the fatigue strength with DC 100 is significantly higher than DC 80, as specified in the current and upcoming Eurocode (EN 1993-1-9, 2005), (prEN 1993-1-9, 2023). However, the low scatter should be taken into consideration. Furthermore, there is no difference in fatigue strength between the radii 150 and 80 mm. A reduction of the detail category of radii smaller 150 mm, therefore, has no experimental basis. The outliner has, though, also shown, how important it is to avoid a weld root failure, as this could otherwise cause a considerably earlier failure. 4. Investigation of influences of internal weld imperfection of cruciform joint and transverse stiffener Within the framework of the presented investigations, two entirely different details were examined: The load carrying cruciform joint and the non-load-carrying joint of the transverse stiffener. In the case of the cruciform joint, lack of penetration and lack of root fusion are particularly problematic, when these imperfections occur in joints that are planned fully penetrated as and can lead to unplanned root failure. Transverse stiffeners, on the other hand, tend to be made using fillet welds. With transverse stiffeners welded into beams, however, there tend to occur air gaps between the stiffener and the flange. This results from the fact that the stiffeners are often dimensioned too small in production to fit into the beam, which is subject to tolerances. The most important results of both studies are briefly presented below. For detailed explanations, please refer to (Bartsch & Feldmann, 2021) (Bartsch, Citarelli, & Feldmann, 2021) (Bartsch & Feldmann, 2022) (Bartsch & Feldmann, 2023 (under review)) To investigate the influence of the lack of penetration and root fusion on the cruciform joint, fatigue tests were carried out on joints with weld imperfections. Five series of cruciform joints with plate thicknesses of 15 mm and steel grade of S355 with different local weld details were performed for this purpose. The cruciform joint can potentially fail at two locations: at the weld toe and at the weld root. According to (EN 1993-1-9, 2005) and (prEN 1993-1-9, 2023), the DC at the weld toe are larger than those at the weld root: for distances of the weld toes of l smaller than 50 mm, DC 80 to DC 36* (EN 1993-1-9, 2005) and DC 71 to DC 40 (prEN 1993-1-9, 2023) respectively. Furthermore, failure from the root is particularly critical, because a crack that grows from the inside is more difficult to inspect. The aim of the tests described here was therefore to find out when the failure at the toe becomes decisive, so that the root is not even considered as a failure location. Fig. 5: Failure location of cruciform joint depending on gap size and weld size from numerical simulations using effective notch stress concept. Ͳ ͲǤʹͷ ͲǤͷ ͲǤ͹ͷ ͳ ͳǤʹͷ ͳǤͷ ͳǤ͹ͷ Ͳ ͲǤͳ ͲǤʹ ͲǤ͵ ͲǤͶ ͲǤͷ a / t CP [-] g / t CP [-] Failure from toe Failure from root 4.2. Investigation of cruciform joints with lack of penetration or root fusion 4.1. Overview