PSI - Issue 77

L.M. Sauer et al. / Procedia Structural Integrity 77 (2026) 34–40 Author name / Structural Integrity Procedia 00 (2026) 000–000

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contacting method through the extensometer edges, the measurement of the electrical resistance and the strain were combined, which allows a local measurement in the test area and a direct transfer of the measured strain to the length change of the electrical resistance measurement. As a result, the decrease of the electrical resistance during fatigue was correlated with geometrical changes since the determined electrical resistivity stays in the same range. The influence of geometry and temperature on the electrical resistance were compensated by the determination of the temperature-independent electrical resistivity on which the development of microstructural damage was evaluated. In addition, the individual electrical resistance changes through geometry and temperature were calculated and compared with the measured electrical resistance change. For the first 75% of the lifetime only minor changes in the microstructure were determined, while after 75% significant changes were observed, followed by higher changes at the end of the test. Future research will concentrate on the characterization and separation of the influences of microstructure on electrical resistance. The objective of this study is to quantify the individual influence of voids, dislocations, and microcracks during fatigue testing. The influence of voids will be determined using simulations, whereby the voids will be characterized using AI-based image segmentation on SEM images. Acknowledgements Funded by the German Research Foundation (Deutsche Forschungsgemeinschaft, DFG) within the Collaborative Research Center CRC/Transregio 188 “Damage-controlled forming processes”– project no. 278868966. References Luecker, L., Lingnau, L.A., Walther, F., 2022. Non-destructive direct current potential drop assessment of forming-induced pre-damage in AISI 5115 steel. Procedia Structural Integrity 42, 368–373. https://doi.org/10.1016/j.prostr.2022.12.046 Lingnau, L.A., Heermant, J., Otto, J.L., Donnerbauer, K., Sauer, L.M., Luecker, L., Macias Barrientos, M., Walther, F., 2024. Separation of damage mechanisms in full forward rod extruded case-hardening steel 16MnCrS5 using 3D image segmentation. Materials 17, 3023. https://doi.org/10.3390/ma17123023 Langenfeld, K., Lingnau, L.A., Gerlach, J., Kurzeja, P., Gitschel, R., Walther, F., Kaiser, T., Clausmeyer, T., 2023. Low cycle fatigue of components manufactured by rod extrusion: Experiments and modeling. Advances in Industrial and Manufacturing Engineering 7, 100130. https://doi.org/10.1016/j.aime.2023.100130 Matthiessen, A., 1865. On the specific resistance of the metals in terms of the B. A. unit (1864) of electric resistance, together with some remarks on the so-called mercury unit. The London, Edinburgh, and Dublin Philosophical Magazine and Journal of Science 29, 361–370. https://doi.org/10.1080/14786446508643887 Nagata, T., Kohei, T., Adachi, H., Ishikawa, K., Miyajima, Y., 2022. A comparison study of electrical resistivity, Vickers hardness, and microstructures of alloy 625 prior and posterior to rolling. Materials Transactions 63, 278-285. https://doi.org/10.2320/matertrans.MT-M2021204 Nobile R., Saponaro A., 2021. Real-time monitoring of fatigue damage by electrical resistance change method. International Journal of Fatigue 151, 106404. doi.org/10.1016/j.ijfatigue.2021.106404 Omari, M. A., Sevostianov, I., 2013. Evaluation of the growth of dislocation density in fatigue loading process via electrical resistance measurements. International Journal of Fracture 179, 229–235. https://doi.org/10.1007/s10704-012-9780-5 Singh, Y., 2013. Electrical resistivity measurements: a review. International Journal of Modern Physics 22, 745–756. https://doi.org/10.1142/S2010194513010970 Sauer, L. M., Otto, J. L., Ziman, J. A., Starke, P., Walther, F., 2024. Electrical resistance-based fatigue damage assessment of steels. Procedia Structural Integrity 68, 432–438. https://doi.org/10.1016/j.prostr.2025.06.078 Sauer, L. M., Otto, J. L., Lingnau, L. A., Ziman, J. A., Starke, P., Walther, F., 2025. Test setup for analyzing the electrical resistance during fatigue loading for metastable austenite AISI 304L and its diffusion-brazed joints. International Journal of Material Research and Technology 35, 535– 544. https://doi.org/10.1016/j.jmrt.2025.01.052 Tekkaya, A.E., Bouchard, P.-O., Bruschi, S., Tasan, C.C., 2020. Damage in metal forming. CIRP Ann. 69, 600–623. https://doi.org/10.1016/j.cirp.2020.05.005