PSI - Issue 77

L.A. Lingnau et al. / Procedia Structural Integrity 77 (2026) 26–33 Author name / Structural Integrity Procedia 00 (2026) 000–000

33

8

The results confirm previous findings that tension-tension loading conditions are particularly critical with respect to damage accumulation. Furthermore, the experiments validate that damage preferentially forms in and around manganese sulfides, which play a key role in damage initiation and propagation, particularly through the fracture of the manganese sulfides. Among the two main damage mechanisms associated with manganese sulfide fracture and decohesion at the manganese sulfide-matrix interface the fracture mechanism was observed to be predominant. The decohesion mechanism could only be detected to a minor extent, which is attributed to the fact that the present investigations were conducted on specimen surfaces, whereas decohesion occurs more frequently within the bulk material. Future work should therefore focus on damage characterization in the material volume. In addition, the evaluation methodology using AI-based image segmentation can be readily applied to further experiments of a similar design. For additional insights into forming-induced ductile damage, X-ray diffraction (XRD) could be employed, where analysis of the full width at half maximum (FWHM) of diffraction peaks may allow for the determination of dislocation densities and thus provide additional parameters for simulation models. 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. Funded by the DFG and the Ministry of Culture and Science of North Rhine-Westphalia (Ministerium fuer Kultur und Wissenschaft des Landes Nordrhein-Westfalen, NRW) within the Major Research Instrumentation Program for the “FIB-SEM”– project no. 386509496. References Beretta, S., Foletti, S., Valiullin, K., 2011. Fatigue strength for small shallow defects/cracks in torsion. Int. J. Fatigue 33, 287–299. https://doi.org/10.1016/j.ijfatigue.2010.08.014. Callaghan, M.D., Humphries, S.R., Law, M., Ho, M., Bendeich, P., Li, H., Yeung, W.Y., 2010. Energy-based approach for the evaluation of low cycle fatigue behaviour of 2.25Cr–1Mo steel at elevated temperature. Mater. Sci. Eng. A 527, 5619–5623. https://doi.org/10.1016/j.msea.2010.05.011. Ehle, L.C., Strunk, R., Borchers, F., Schwedt, A., Clausen, B., Mayer, J., 2020. Influence of process chains with thermal, mechanical and thermo mechanical impact on the surface modifications of a grind-strengthened 42CrMo4 steel. Procedia CIRP 87, 426–31. https://doi.org/10.1016/j.procir.2020.02.088. Gerin, B., Pessard, E., Morel, F., Verdu, C., Mary, A., 2016. Beneficial effect of prestrain due to cold extrusion on the multiaxial fatigue strength of a 27MnCr5 steel. International Journal of Fatigue 92, 345–359. https://doi.org/10.1016/j.ijfatigue.2016.07.012. Hering, O., Tekkaya, A.E., 2020. Damage-induced performance variations of cold forged parts. J. Mater. Process. Technol. 279, 116556. https://doi.org/10.1016/j.jmatprotec.2019.116556. Langenfeld, K., Lingnau, L., 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. Adv. Ind. Manuf. Eng. 7, 100130. https://doi.org/10.1016/j.aime.2023.100130. Lingnau, L.A., Walther, F., 2023. Characterization and separation of damage mechanisms of extruded case-hardening steel AISI 5115 under cyclic axial-torsional loading. Trans Tech Publications Ltd.: Bäch, Switzerland; ISBN 978-3-0364-1104-0. Lingnau, L.A., Heermant, J., Otto, J.L., Donnerbauer, K., Sauer, L.M., Lücker, L., Macias Barrientos, M., Walther, F., 2024a. 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 Lingnau, L. A., Heermant, J., Otto, J. L., Donnerbauer, K., Macias Barrientos, M., Walther, F., 2024b. Quantification of forming-induced damage in case-hardening steel AISI 5115 by advanced SEM methods. Practical Metallography 61 (9-10), 661-678. https://doi.org/10.1515/pm-2024-0061 Lingnau, L. A., Heermant, J., Sauer, L. M., Brakmann, C. H., Walther, F., 2025. Load path-dependent fatigue capability of forward rod extruded case hardening steel 16MnCrS5. Procedia Structural Integrity 68, 303-309. https://doi.org/10.1016/j.prostr.2025.06.058 Moehring, K., Walther, F., 2020. Performance-related characterization of forming-induced initial damage in 16MnCrS5 steel under a torsional forward-reverse loading path at LCF regime. Materials 13, 2463. https://doi.org/10.3390/ma13112463. Shankar, V., Mariappan, K., Sandhya, R., Laha, K., 2016. Understanding low cycle fatigue and creep–fatigue interaction behavior of 316 L(N) stainless steel weld joint. Int. J. Fatigue 82, 487–496. https://doi.org/10.1016/j.ijfatigue.2015.09.003. 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. Zapara, M., Augenstein, E., Helm, D., 2014. Prediction of damage in cold bulk forming processes. PAMM Proc. Appl. Math. Mech. 14, 1037– 1040. https://doi.org/10.1002/pamm.201410492.