Four Ways to Assess a Weld — and When Each Fits
Verifying a weld by calculation is not a question of right or wrong but of the appropriate method. Several established concepts exist, and they differ considerably in effort, level of detail and the modelling they require. Choose the most expensive where a simple one suffices and you waste time — choose the coarse one where accuracy is needed and you risk the result.
The Methods at a Glance
Nominal stress concept. The simplest approach: you refer to the nominal stress in the component and assign the weld to a standardised weld class. Fast and robust — as long as the geometry matches the cases stored in the code.
Structural stress concept. Here the stress at the weld toe is determined, usually by extrapolation from the FEA model. It captures geometric influences the nominal stress concept cannot see, without having to model the weld in detail.
Notch stress concept. The most involved method: the weld is modelled with a defined reference radius to capture the local notch stress directly. Accurate, but with high modelling effort.
Added to these are code-specific approaches such as the R1 concept and tools such as FEMFAT Weld that put these concepts into practice.
Which One When?
The choice follows from geometry, code and required accuracy: standard weld with a matching class → nominal stress. Complex geometry but no detailed modelling possible → structural stress. Highest accuracy at the critical weld → notch stress.
Conclusion
There is no single correct method, only the one that fits the task. The skill lies in applying effort where it genuinely improves the result.
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