University of Oulu

Schönbauer, BM, Ghosh, S, Karr, U, et al. Mean-stress sensitivity of an ultrahigh-strength steel under uniaxial and torsional high and very high cycle fatigue loading. Fatigue Fract Eng Mater Struct. 2022; 45( 11): 3361- 3377. doi:10.1111/ffe.13767

Mean-stress sensitivity of an ultrahigh-strength steel under uniaxial and torsional high and very high cycle fatigue loading

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Author: Schönbauer, Bernd M.1,2; Ghosh, Sumit2; Karr, Ulrike1;
Organizations: 1Institute of Physics and Materials Science, University of Natural Resources and Life Sciences, Vienna (BOKU), 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, 58.8 MB)
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Language: English
Published: John Wiley & Sons, 2022
Publish Date: 2022-09-16


The influence of load ratio on the high and very high cycle fatigue (VHCF) strength of Ck45M steel processed by thermomechanical rolling integrated direct quenching was investigated. Ultrasonic fatigue tests were performed under uniaxial and torsional loading at load ratios of R = −1, 0.05, 0.3, and 0.5 with smooth specimens and specimens containing artificially introduced defects. Up to 2 × 10⁵ cycles, failure originated from surface aluminate inclusions and pits under both loading conditions. The prevailing fracture mechanisms in the VHCF regime were interior crack initiation under uniaxial loading and surface shear crack initiation under torsional loading. The mean-stress sensitivity and the fatigue strength were evaluated using fracture mechanics approaches. Equal fatigue limits for uniaxial and torsional loading were determined considering the size of crack initiating defects and the appropriate threshold condition for Mode-I crack growth. Furthermore, the mean-stress sensitivity is independent of loading condition and can be expressed by \( {\sigma}_{\mathrm{w}}(R)={\left.{\sigma}_{\mathrm{w}}\right|}_{R=-1}\cdotp {\left(\frac{1-R}{2}\right)}^{0.63} \) and \( {\tau}_{\mathrm{w}}(R)={\left.{\tau}_{\mathrm{w}}\right|}_{R=-1}\cdotp {\left(\frac{1-R}{2}\right)}^{0.63} \).

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Series: Fatigue & fracture of engineering materials & structures
ISSN: 8756-758X
ISSN-E: 1460-2695
ISSN-L: 8756-758X
Volume: 45
Issue: 11
Pages: 3361 - 3377
DOI: 10.1111/ffe.13767
Type of Publication: A1 Journal article – refereed
Field of Science: 216 Materials engineering
116 Chemical sciences
Funding: The authors would like to express their gratitude to late Mr. Seppo Järvenpää for his valuable assistance during this research. 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: © 2022 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.