PSI - Issue 76

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ScienceDirect

Procedia Structural Integrity 76 (2026) 27–34

© 2025 The Authors. Published by ELSEVIER B.V. This is an open access article under the CC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0) Rectangular notches with a defined width and depth were manufactured in flat samples of a low-alloyed steel with two different heat treatments using an engraving laser. This method allows a rapid production of very sharp notches without plastic deformation and with only a slight thermal influence on the surrounding material. The samples prepared in this way were fatigued with block wise increasing loads until failure. Cracks are detected by means of a Direct Current Potential Drop method. The length of the loading block (number of cycles) is determined by the measured potential drop. This procedure enables a reliable and precise determination of the limit stress for the respective notch size with low experimental effort and time consumption. The tests have shown that in case of the normalized steel none of the models describes the determined values for the fatigue limit. For the hardened steel, the plot of the fatigue limit as a function of the Murakami parameter √ in combination with the El Haddad model allows a satisfactory description of the measured values. 5th International Symposium on Fatigue Design and Material Defects FDMD 2025 Determination of the Kitagawa-Takahashi Diagram using DC Potential Drop Measurements Jürgen Bär a *, Naveen K. Kanna a , Larissa Duarte b , Mauro Madia b a University of the Bundeswehr Munich, Institute for Materials Science, D-85577 Neubiberg, Germany b Bundesanstalt für Materialforschung und -prüfung (BAM), D-12205 Berlin, Germany Abstract The Kitagawa-Takahashi Diagram is an important tool for describing the fatigue limit of components containing defects. The models used for its description differ, particularly in the transition region corresponding to the short crack regime. Therefore, for a reliable statement about the fatigue limit in this area, an experimental validation of the models is necessary. However, the standardized staircase method requires a large number of samples and has a long test duration. In this work, a method is presented that allows a simpler and faster validation of the Kitagawa-Takahashi Diagram in the region of short cracks.

Peer-review under responsibility of the scientific committee of the FDMD 2025 chairpersons Keywords: fatigue limit; material defects; Kitagawa-Takahashi Diagram; Potential Drop

* Corresponding author. Tel.: +49 89 6004 2561; fax: +49 89 6004 2561. E-mail address: juergen.baer@unibw.de

2452-3216 © 2025 The Authors. Published by ELSEVIER B.V. This is an open access article under the CC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0) Peer-review under responsibility of the scientific committee of the FDMD 2025 chairpersons 10.1016/j.prostr.2025.12.283