G ustav Hultgren

KTH Royal Institute of Technology Department of Engineering Mechanics, Stockholm, Sweden

Gustav Hultgren works as a Ph.D. candidate within the Weld and Composite Mechanics Group at the Royal Institute of Technology KTH, Sweden. He holds a B.Sc. in Mechanical Engineering (2017) and an M.Sc. in Engineering Mechanics (2019). His research focuses on the fatigue and fracture strength of welded joints in ultra-high-strength steel. The research combines experimental testing for fatigue of welded joints and fracture strength in sub-zero temperatures with simulation work, namely probabilistic modelling methods.


The local weld geometry and its variability can significantly affect the fatigue strength of structures, especially for non-load-carrying welds. The local stress-raising effects at the weld toe are for these joint configurations governed by standardised definitions such as sharp transition radii or adverse undercuts. Nowadays, digitalised tools for weld quality assurance accurately determine these standardised geometrical definitions with a high resolution, making it possible to study how the variability in geometry affects the fatigue strength further.

Perfect weld transitions with constant radii and smooth surfaces, which make the standardised geometrical definitions easily definable are, however, seldom seen in real welds. Actual weld sections can instead have multiple transition radii, undercuts, and ripple lines which introduce some uncertainty in the geometry estimations. Numerical simulations of the actual weld geometry, with all its variations, in combination with probabilistic evaluations, have shown great potential for studying the influence of competing notches in the weld. In this study, the probabilistic evaluation of simulated welds is used to analyse the relationship between the local weld stress, derived from the weakest link theory, and the standardised geometrical definitions determined by a commercial digital quality assurance system. The results show that the interactions of geometrical definitions greatly impact the local fatigue strength properties, with some features, such as the weld toe radius, which has a stronger influence.


Room 7Thursday 30th November14:00-14:30Gustav Hultgren
S08-5 Fatigue and manufacturing process
46 - Effect of local weld geometry and its variability on the local weld stress
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