PSI - Issue 75

Georg Veile et al. / Procedia Structural Integrity 75 (2025) 184–192 Georg Veile / Structural Integrity Procedia (2025) =( ∙ ∆ 2 + ∆2 ∆2 ) =( 1+ 1 ∗ ) ∙ ∆ 2 + (1 +1 ∗ ) ∆2 ∆2

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An alternative approach to using the idealized weld geometry is the implementation of scanned weld topologies. Fatigue life prediction of scanned weld geometries can be less accurate than prediction using an idealized weld radius (Veile et al. 2025; Ladinek et al. 2018). A direct comparison was made in (Veile et al. 2025) and is illustrated in Fig. 1. The process of fatigue life assessment is described in (Veile et al. 2025) in detail. The accuracy can be improved by adjusting the material model retrospectively (Niederwanger et al. 2020; Niederwanger et al. 2019; Hultgren et al. 2021). However, this cannot be applied to fatigue life prediction in industry (Veile et al. 2025). As alternative, additional factors that consider stress, strain or shear gradients and geometric factors, can be introduced.

Fig. 1. Comparison of the experimental and predicted fatigue life with an idealised fictive radius of 1 mm (left) and scanned weld surfaces (right) from (Veile et al. 2025).

In this work, the current state of the endeavour to improve fatigue lifetime prediction of scanned weld topologies is presented. Scanned weld topologies show radii of up to 0.1 mm in the critical areas. These radii can be smaller than the grain size of the base metal. Since prediction using an idealised weld radius shows higher precision, the effect of local radii of the scanned topology are of interest. For this reason, the effects of smoothening the scanned weld topology is investigated. In (Veile et al. 2025) a high sensitivity of FDP FFS and FDP RM to scanned weld topologies was observed. These FDP are gradient-based and show an increase in non-conservatism. Different approaches to assess the shear- and strain gradients are common. Hence why, the effects of different gradient assessments were investigated in (Veile 2025) and also presented in this work. 2. Methodology The investigated specimens in this work resemble nuclear grade weld joints of reactor internals. These components are subject to environmentally assisted fatigue. For this reason, austenitic stainless steels (AISI 347 and 304 L) as well as the nuclear grade weld metal ER 347 were used to manufacture component like specimen. For more info, reference is made to (Veile et al. 2025) regarding the experimental setup, FEA, material models, as well as (Rudolph et al. 2024; Veile et al. 2024; Smaga et al. 2024) regarding the load state of reactor internals. Here one can find a detailed description of the experimental setup for the displacement-controlled fatigue tests with a displacement ratio of -1. As failure a force drop of 25% was set to stop the experiments.