PSI - Issue 75

Okan Yılmaz et al. / Procedia Structural Integrity 75 (2025) 435 –441

441

O. Yılmaz and D. Van Hoecke / Structural Integrity Procedia 00 (2025) 000–000

7

Smoother fatigue crack

Fatigue crack surface

Rough patch shows initial defect propagating in first cycles

1 mm

1 mm

Crack propagation direction

Fig. 6. Fracture surfaces of defective (left) and smooth (right) bending surfaces. For the defective bended surface, initial defects propagate in the first cycles creating a rough patch.

obtained. Currently, fatigue life calculation does not take into account the residual stresses that the forming induces, which is shown to be critical especially in the fatigue crack propagation phase by Yamaguchi et al. (2023). Future e ff orts will focus on the inclusion of residual stresses into the calculation routine as proposed by Yadegari et al. (2024).

References

Bracke, L., De Knijf, D., Gerritsen, C., Hojjati Talemi, R., Diaz Gonzalez, E., 2017. Development of direct quenched hot rolled martensitic strip steels. Metals 7, 326. EN10149-2, 2013. Hot rolled flat products made of high yield strength steels for cold forming, Part 2: Technical Delivery Conditions for Thermo mechanically Rolled Steels, European Committee for Standardization. Fiedler, M., Vormwald, M., 2018. Introduction to the new fkm guideline which considers nonlinear material behaviour, in: MATEC Web of Conferences, EDP Sciences. p. 10014. Fiedler, M., Wa¨chter, M., Varfolomeev, I., Vormwald, M., Esderts, A., 2019. Richtlinie Nichtlinear: Rechnerischer Festigkeitsnachweis unter expliziter Erfassung nichtlinearen Werksto ff verformungsverhaltens: fu¨r Bauteile aus Stahl, Stahlguss und Aluminiumknetlegierungen. VDMA Verlag GmbH. Geers, T., Ho ff meister, B., Heinemeyer, C., 2021. Investigations on the influence of cold-forming and associated residual stresses on the fatigue strength of thin-walled details. ce / papers 4, 505–510. Gothivarekar, S., Coppieters, S., Talemi, R., Debruyne, D., 2020. The influence of post-necking strain hardening behaviour on fatigue lifetime prediction of cold-formed high strength steel. Procedia Manufacturing 47, 1250–1256. Gothivarekar, S., Coppieters, S., Talemi, R., Debruyne, D., 2021. E ff ect of bending process on the fatigue behaviour of high strength steel. Journal of Constructional Steel Research 182, 106662. Gothivarekar, S., Pen˜a, C.J., Coppieters, S., Talemi, R., Debruyne, D., 2019. Fatigue behaviour and lifetime prediction of cold-formed high strength steel, in: AIP Conference Proceedings, AIP Publishing. Neuber, H., 1961. Theory of stress concentration for shear-strained prismatical bodies with arbitrary nonlinear stress-strain law . Ramberg, W., Osgood, W.R., 1943. Description of stress-strain curves by three parameters. Technical Report NACA-TN-902. Smith, K.N., Watson, P., Topper, T.H., 1970. A stress-strain function for the fatigue of metals. Journal of Materials 5, 767–778. Talemi, R., Chhith, S., De Waele, W., 2017. Experimental and numerical study on e ff ect of forming process on low-cycle fatigue behaviour of high-strength steel. Fatigue & Fracture of Engineering Materials & Structures 40, 2050–2067. Yadegari, P., Beier, H.T., Vormwald, M., 2024. A two-point fatigue strength assessment for surface-hardened notched components under consider ation of residual stresses based on the local strain approach. International Journal of Fatigue 184, 108326. Yadegari, P., Fa¨llgren, C., Beier, H.T., Vormwald, M., Kleemann, A., 2023. Extension of methods for estimating the fatigue strength of components made of ultra-high strength steels. International Journal of Fatigue 167, 107325. Yamaguchi, N., Tokita, Y., Shiozaki, T., Tamai, Y., Ichikawa, Y., Ogawa, K., 2023. Fatigue crack propagating behavior from inner surface crack on bent sheet of ultra-high strength steel. International Journal of Fatigue 175, 107819.