PSI - Issue 54

Jürgen Bär et al. / Procedia Structural Integrity 54 (2024) 188–195 Author name / Structural Integrity Procedia 00 (2019) 000–000

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 With the Tiedemann function better fit results compared to the Johnson equation are achieved.  With the Tiedemann function the crack size of both, short and long fatigue cracks can be determined.  The multiple potential drop measurement in combination with the geometrical model by Hartweg and Bär and the Tiedemann function allows the investigation of all three phases of the cyclic lifetime on notched round specimens. The differences in the potential curves of different samples may be caused by differences in the geometry of the crack front. Further analyses will therefore investigate whether conclusions can be drawn from the measurements about the geometry of the crack front. Furthermore, experiments are to be carried out on unnotched round samples in order to investigate the suitability of the method on this sample geometry as well. The transferability of the model to flat specimens and to additively manufactured specimens with incipient cracks in the specimen volume is also to be investigated in the future. References Bjørheim, Fredrik; Siriwardane, Sudath C.; Pavlou, Dimitrios, 2022. A review of fatigue damage detection and measurement techniques. In: International Journal of Fatigue 154, 106556. DOI: 10.1016/j.ijfatigue.2021.106556. Hartweg, M.; Bär, J., 2019. Analysis of the crack location in notched steel bars with a multiple DC potential drop measurement. In: Procedia Structural Integrity 17, 254. DOI: 10.1016/j.prostr.2019.08.034. Johnson, H. H., 1965. Calibrating the Electric Potential Method for Studying Slow Crack Growth. In: Materials Research and Standards 5 (9), 442. Nahbein, M.; Bär, J., 2022. Determination of Cracks using Multiple DC Potential Drop Measurements – Experimental Verification of an Advanced Model. In: Procedia Structural Integrity 42, 433. DOI: 10.1016/j.prostr.2022.12.055. Schijve, J., 2003. Fatigue of structures and materials in the 20th century and the state of the art. In: International Journal of Fatigue 25 (8), 679. DOI: 10.1016/S0142-1123(03)00051-3. Si, Y.; Rouse, J. P.; Hyde, C. J., 2020. Potential difference methods for measuring crack growth: A review. In: International Journal of Fatigue 136, 105624. DOI: 10.1016/j.ijfatigue.2020.105624. Tiedemann, D., 2016. Zweidimensionale Ausbreitung kurzer Risse unter Berücksichtigung bruchmechanischer und kontinuumsmechanischer Aspekte. Ein Beitrag zur Optimierung von Lebensdauervorhersagen an gekerbten Strukturen. PhD-Thesis. Universität der Bundeswehr München, Institute for Materials Science.