Fatigue design of mild and high-strength steel cruciform joints in as-welded and HFMI-treated condition by nominal and effective notch stress approach

Peter Brunnhofer*, Christian Buzzi, Tobias Pertoll, Martin Rieger, Martin Leitner

*Corresponding author for this work

Research output: Chapter in Book/Report/Conference proceedingConference paperpeer-review


According to the Recommendations for Fatigue Design of Welded Joints and Components by the International Institute of Welding (IIW), the fatigue strength of welded steel joints is in general independent of the base material strength. Post-treatment methods, such as the High Frequency Mechanical Impact (HFMI) treatment, can significantly increase the fatigue performance of welded joints especially in case of high-strength steel applications, which is already considered within the IIW Recommendations for the HFMI Treatment. This paper firstly investigates the effect of the base material strength on the fatigue resistance of welded and HFMI-treated steel joints. Therefore, mild steel S355 and high-strength steel S700 cruciform joints are cyclically tested in both conditions and the statistically evaluated S/N-curves are compared. The results reveal an increase of the high-cycle fatigue strength by the HFMI-treatment by a factor of 1.35 in case of the S355, and of 1.59 for the S700 specimens. Secondly, the test results are assessed by the fatigue design curves of the corresponding structural detail within the IIW-recommendations using the nominal stress concept. Moreover, the applicability of the procedure applying the effective notch approach is analyzed. In order to numerically evaluate the effective notch stress, the geometry of the cruciform joint is modelled according to the given guidelines within the recommendations applying a reference radius of 1 mm at the weld toe for both conditions. On the basis of the numerically computed effective notch stress, a local fatigue design is performed for all test series, which reveals sound accordance between the recommended design curves and the statistically evaluated fatigue test S/N-curves.

Original languageEnglish
Title of host publicationFatigue Design 2021, International Conference Proceedings
EditorsFabien Lefebvre, Pascal Souquet
Number of pages13
Publication statusPublished - 2021
EventFatigue Design 2021: 9th Edition of the International Conference on Fatigue Design - Senlis, France
Duration: 17 Nov 202119 Nov 2021

Publication series

NameProcedia Structural Integrity


ConferenceFatigue Design 2021
Internet address


  • Effective notch stress approach
  • Fatigue design
  • HFMI-treatment
  • High-strength steel
  • Welded joints

ASJC Scopus subject areas

  • General Engineering
  • Mechanics of Materials
  • Mechanical Engineering
  • Materials Science(all)
  • Civil and Structural Engineering

Fields of Expertise

  • Mobility & Production


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