PSI - Issue 68

Lucia Morales-Rivas et al. / Procedia Structural Integrity 68 (2025) 493–499 Lucia Morales-Rivas, Eberhard Kerscher / Structural Integrity Procedia 00 (2025) 000–000 ∆ ( values from eqs. 2,8, listed in Table 4, are close to those from eqs. 6,7 (Table 4), and the trends are also consistent. From Fig. 4.b, it can be confirmed that by using eq. 8, the fatigue limit of sharp-notched specimens is coincident with the threshold for the propagation of short cracks (eqs. 1,2). Moreover, for high stress concentration values, the fatigue limit of sharp-notched specimens tends to the threshold for the propagation of long cracks, which makes this 499 7

formulation more conservative. 4. Conclusions and prospects

V-shaped notches exert a volume effect on the fatigue response of advanced bainitic steels that should not be neglected, responsible for the observed notch fatigue-strengthening trend. The use of formulations for the determination of 1 taking advantage of more than one specimen geometry per microstructure and results from crack growth experiments have led to consistent theoretical fatigue limit values. However, inferring the defect-scale fatigue behaviour from experimental results of notch-scale fatigue may disregard physical mechanisms responsible for such phenomena. In this sense, the presence of critical microstructural features and the steel cleanliness are relevant, and the subject of complementary research in progress. Acknowledgements LMR acknowledges the funding from the German Research Foundation (DFG): Research Grants program, project number 411091845. References El Haddad, M.H., Topper, T.H. and Smith, K.N., 1979. Prediction of non propagating cracks. Engineering Fracture Mechanics 11, 3, 573-584. Miller and O’donnell, 1999. The fatigue limit and its elimination. Fatigue & Fracture of Engineering Materials & Structures 22, 7, 545-557. Atzori, B. and Lazzarin, P., 2002. A three-dimensional graphical aid to analyze fatigue crack nucleation and propagation phases under fatigue limit conditions. International Journal of Fracture 118, 3, 271-284. Ciavarella, M. and Meneghetti, G., 2004. On fatigue limit in the presence of notches: classical vs. recent unified formulations. International Journal of Fatigue 26, 3, 289-298. Atzori, B., Lazzarin, P. and Meneghetti, G., 2005. A unified treatment of the mode I fatigue limit of components containing notches or defects. International Journal of Fracture 133, 1, 61-87. Atzori, B., Lazzarin, P. and Meneghetti, G., 2003. Fracture mechanics and notch sensitivity. Fatigue & Fracture of Engineering Materials & Structures 26, 3, 257-267. Heywood, R.B., 1962. Designing Against Fatigue. Chapman and Hall. London, United Kingdom. Neuber, H., 1961. Theory of Stress Concentration for Shear-Strained Prismatical Bodies With Arbitrary Nonlinear Stress-Strain Law. Journal of Applied Mechanics 28, 4, 544-550. Ince, A. and Bang, D., 2017. Deviatoric Neuber method for stress and strain analysis at notches under multiaxial loadings. International Journal of Fatigue 102, 229-240. Visvanatha, S.K., 1998. Master thesis: A study on the use of Neuber's rule in fatigue crack initiation predictions. In Department of Mechanical and Aerospace Engineering, the Ottawa-Carleton Institute for Mechanical and Aerospace Engineering, Carleton University, Ottawa, Ontario, Canada. Sourmail, T., Galtier, A., Sanz, R.P., Janisch, R., Sampath, S., Müller, I., Kerscher, E., Rementeria, R., Garcia-Mateo, C., Caballero, F.G., Morales Rivas, L., Kuntz, M. and Danoix, F., 2017. Understanding basic mechanism to optimize and predict in service properties of nanobainitic steels (MECBAIN). European Commission: Directorate-General for Research and Innovation. Publications Office. Caballero, F.G. and Bhadeshia, H.K.D.H., 2004. Very strong bainite. Current Opinion in Solid State and Materials Science 8, 3, 251-257. Bhadeshia, H.K.D.H., 2010. Nanostructured bainite. Proceedings of the Royal Society A 466, 3-18. Garcia-Mateo, C., Jimenez, J.A., Yen, H.W., Miller, M.K., Morales-Rivas, L., Kuntz, M., Ringer, S.P., Yang, J.R. and Caballero, F.G., 2015. Low temperature bainitic ferrite: Evidence of carbon super-saturation and tetragonality. Acta Materialia 91, 162-173. Mueller, I., Rementeria, R., Caballero, F.G., Kuntz, M., Sourmail, T. and Kerscher, E., 2016. A Constitutive Relationship between Fatigue Limit and Microstructure in Nanostructured Bainitic Steels. Materials 9, 10, pp. 831. Morales-Rivas, L., Azadi, A. and Kerscher, E., 2022. Fatigue behavior of nanostructured bainite: A morphological study of crack path. Procedia Structural Integrity 39, 515-527. Morales-Rivas, L., Azadi, A. and Kerscher, E., 2023. Short fatigue crack growth in an artificial-defect-containing nanostructured bainitic steel. International Journal of Fatigue 166, pp. 107219. Kitagawa, H. and Takahashi, S., 1976. Applicability of Fracture Mechanics to Very Small Cracks or the Cracks in the Early Stage. In: Proceedings International Conference on Mechanical Behavior of Materials 2nd 760816, 2, 627-631.