These slides were presented at the NAFEMS World Congress 2025, held in Salzburg, Austria from May 19–22, 2025.

Abstract

In mechanically stressed components, weld seams are usually the weak points critical to failure, especially under alternating loads. The necessary strength verification is carried out according to rules such as the FKM guideline, the IIW recommendations or the Eurocode. The evaluation of weld seams is a challenge, even in modern simulation-driven product development. Due to the special properties of the weld seams (e.g. sharp and quite irregular notches), the stresses for the verification must be determined using one of the concepts developed for this purpose, for example as nominal, structural or notch stress. With the structural stress concept, the seam is represented in a simplified manner in the FE model and the stress for the verification is extrapolated from the stresses on the surface before the weld toe. The Hot-Spot concept from the IIW recommendations is widely used for this purpose and is also referenced in other guidelines. With the notch stress concept, a fictitious notch radius is introduced in the simulation model at the weld toe and in the weld root. The stress for the verification can then be determined directly in the notch radius. The notch stress concept therefore requires a comparatively high modeling effort but is also suitable for the verification of complex weld seam situations that cannot be evaluated using other methods. The areas of application of the different stress concepts are presented and advantages or disadvantages of the individual concepts are discussed. A practical challenge in the verification of weld seams is also the selection of the critical point, especially when the component is subject to multiple alternating loads. This can be alleviated by an automated calculation of all verification points along a weld seam. For this purpose, approaches to automating the stress determination according to the structural or notch stress concept are presented, which were implemented by ihf. It is shown how the stress components depending on the local weld seam direction can be determined according to the requirements of the different guidelines.