PSI - Issue 77

ScienceDirect Structural Integrity Procedia 00 (2026) 000–000 Structural Integrity Procedia 00 (2026) 000–000 Available online at www.sciencedirect.com Available online at www.sciencedirect.com ScienceDirect Available online at www.sciencedirect.com ScienceDirect

www.elsevier.com/locate/procedia www.elsevier.com/locate/procedia

Procedia Structural Integrity 77 (2026) 432–439

© 2026 The Authors. Published by ELSEVIER B.V. This is an open access article under the CC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0) Peer-review under responsibility of ICSI organizers Abstract The critical distance is a geometric parameter used to describe the effects of notches on failure conditions under static as well as fatigue loading. Under fatigue loading, the critical distance depends on the number of cycles to failure, and it is determined from experimental data measured on smooth and notched samples. The results of the critical distance are influenced by stress concentration level as well as surface quality. © 2026 The Authors. Published by ELSEVIER B.V. This is an open access article under the CC BY license (https://creativecommons.org/licenses/by/4.0) Peer-review under responsibility of ICSI organizers Keywords: Theory of critical distances; fatigue life predictions; very high cycle fatigue; high strength steels; surface quality; 1. Introduction The fatigue life predictions of notched components can be estimated e.g. by means of the theory of critical distances (Susmel, et al., 2007), (Susmel, 2008). According to the line method of the theory of critical distances, the average stress over the critical distance is the same for notches of different shapes and stress concentration factors. It has been demonstrated that the critical distance is dependent on the number of cycles to failure and can be determined from experimental data (Kozáková, et al., 2024). The critical distance can be determined based on S-N curves measured on smooth specimens and specimens with a model notch. It was shown that more reliable results of the fatigue life predictions are obtained when the critical distance is modified by the ratio of stress concentration factors of the model Abstract The critical distance is a geometric parameter used to describe the effects of notches on failure conditions under static as well as fatigue loading. Under fatigue loading, the critical distance depends on the number of cycles to failure, and it is determined from experimental data measured on smooth and notched samples. The results of the critical distance are influenced by stress concentration level as well as surface quality. © 2026 The Authors. Published by ELSEVIER B.V. This is an open access article under the CC BY license (https://creativecommons.org/licenses/by/4.0) Peer-review under responsibility of ICSI organizers Keywords: Theory of critical distances; fatigue life predictions; very high cycle fatigue; high strength steels; surface quality; 1. Introduction The fatigue life predictions of notched components can be estimated e.g. by means of the theory of critical distances (Susmel, et al., 2007), (Susmel, 2008). According to the line method of the theory of critical distances, the average stress over the critical distance is the same for notches of different shapes and stress concentration factors. It has been demonstrated that the critical distance is dependent on the number of cycles to failure and can be determined from experimental data (Kozáková, et al., 2024). The critical distance can be determined based on S-N curves measured on smooth specimens and specimens with a model notch. It was shown that more reliable results of the fatigue life predictions are obtained when the critical distance is modified by the ratio of stress concentration factors of the model International Conference on Structural Integrity Critical distances for fatigue life predictions of high-strength steels with notches with various stress concentrations Klusák Jan a *, Kozáková Kamila a , Seitl Stanislav a,b International Conference on Structural Integrity Critical distances for fatigue life predictions of high-strength steels with notches with various stress concentrations Klusák Jan a *, Kozáková Kamila a , Seitl Stanislav a,b a Institute of Physics of Materials, Czech Academy of Sciences, Zizkova 513/22, Brno, Czech Republic b Faculty of Civil Engineering, Brno University of Technology, Veveri 331, Brno, Czech Republic a Institute of Physics of Materials, Czech Academy of Sciences, Zizkova 513/22, Brno, Czech Republic b Faculty of Civil Engineering, Brno University of Technology, Veveri 331, Brno, Czech Republic

* Corresponding author. Tel.: +420 532290348. E-mail address: klusak@ipm.cz * Corresponding author. Tel.: +420 532290348. E-mail address: klusak@ipm.cz

2452-3216 © 2026 The Authors. Published by ELSEVIER B.V. This is an open access article under the CC BY license (https://creativecommons.org/licenses/by/4.0) Peer-review under responsibility of ICSI organizers 2452-3216 © 2026 The Authors. Published by ELSEVIER B.V. This is an open access article under the CC BY license (https://creativecommons.org/licenses/by/4.0) Peer-review under responsibility of ICSI organizers

2452-3216 © 2026 The Authors. Published by ELSEVIER B.V. This is an open access article under the CC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0) Peer-review under responsibility of ICSI organizers 10.1016/j.prostr.2026.01.055