University of Oulu

Schönbauer, BM, Ghosh, S, Kömi, J, Frondelius, T, Mayer, H. Influence of small defects and nonmetallic inclusions on the high and very high cycle fatigue strength of an ultrahigh-strength steel. Fatigue Fract Eng Mater Struct. 2021; 44( 11): 2990- 3007.

Influence of small defects and nonmetallic inclusions on the high and very high cycle fatigue strength of an ultrahigh-strength steel

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Author: Schönbauer, Bernd M.1; Ghosh, Sumit2; Kömi, Jukka2;
Organizations: 1Institute of Physics and Materials Science, University of Natural Resources and Life Sciences (BOKU), Vienna, Austria
2Materials and Mechanical Engineering, Centre for Advanced Steels Research, University of Oulu, Oulu, Finland
3R&D and Engineering, Wärtsilä, Vaasa, Finland
Format: article
Version: published version
Access: open
Online Access: PDF Full Text (PDF, 32.7 MB)
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Language: English
Published: John Wiley & Sons, 2021
Publish Date: 2021-08-13


The high and very high cycle fatigue (VHCF) properties of ultrahigh-strength Ck45M steel processed by thermomechanical rolling integrated direct quenching were investigated. SN tests with smooth and small drilled holes containing specimens as well as near-threshold fatigue crack growth measurements were performed up to 2 × 10¹⁰ cycles using ultrasonic-fatigue testing technique. The fatigue strength of smooth specimens is mainly determined by the size of nonmetallic inclusions. For surface defects larger than 80 μm, the fatigue limit can be correlated with a constant threshold-stress intensity factor. The \(\sqrt{area}\)-parameter model adequately predicts the fatigue limit for internal defects and for surface defects with sizes between 30 and 80 μm. VHCF failures from smaller surface defects occur at stress amplitudes below the predicted fatigue limit. The long-crack threshold in ambient air is close to the effective threshold stress intensity factor. In optically dark areas at interior inclusions, cracks grow at mean propagation rates of 10⁻¹⁵ m/cycles.

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Series: Fatigue & fracture of engineering materials & structures
ISSN: 8756-758X
ISSN-E: 1460-2695
ISSN-L: 8756-758X
Volume: 44
Issue: 11
Pages: 2990 - 3007
DOI: 10.1111/ffe.13534
Type of Publication: A1 Journal article – refereed
Field of Science: 216 Materials engineering
Funding: The financial support of the Austrian Science Fund (FWF) under project number P 29985-N36 and the Academy of Finland under the auspices Genome of Steel (Profi3) project #311934 is acknowledged.
Copyright information: © 2021 The Authors. Fatigue & Fracture of Engineering Materials & Structures published by John Wiley & Sons Ltd. This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.