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Interaction of non-metallic inclusions, microstructure, and fatigue loading with small crack growth in high-strength steels

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dc.contributor Aalto-yliopisto fi
dc.contributor Aalto University en
dc.contributor.advisor Marquis, Gary, Prof., Aalto University, Finland
dc.contributor.author Roiko, Andrew
dc.date.accessioned 2017-10-18T09:02:52Z
dc.date.available 2017-10-18T09:02:52Z
dc.date.issued 2017
dc.identifier.isbn 978-952-60-7648-5 (Aalto, electronic)
dc.identifier.isbn 978-952-60-7649-2 (Aalto, printed)
dc.identifier.isbn 978-951-38-8578-6 (VTT, electronic)
dc.identifier.isbn 978-951-38-8579-3 (VTT, printed)
dc.identifier.issn 1799-4942 (Aalto, electronic)
dc.identifier.issn 1799-4934 (Aalto, printed)
dc.identifier.issn 1799-4934 (Aalto, ISSN-L)
dc.identifier.issn 2242-1203 (VTT, electronic)
dc.identifier.issn 2242-119X (VTT, printed)
dc.identifier.issn 2242-119X (VTT, ISSN-L)
dc.identifier.uri https://aaltodoc.aalto.fi/handle/123456789/28398
dc.description.abstract The increased demand and requirements for high-strength steels drives the need to better understand and predict the fatigue endurance and crack growth challenges related to their use in critical machine components. Non-metallic inclusions or defects in the steel become increasingly important as the hardness or strength of the steel increases. The distribution and the ability to predict the largest inclusion that causes failure is crucial for the proper and successful design and production of the components.  The extreme value distribution is effective in predicting the maximum inclusion in a volume of steel. The proper prediction and use of inclusion data gathered from polished specimen as well as differences in anisotropy are important to consider when gathering data for use in design and prediction of fatigue life or failure. The difference in non-metallic inclusions and the forging direction affects the distribution of the size of the inclusions as well as the fatigue endurance limit and its scatter of the steel. The extreme value distributions combined with the Murakami-Endo model are used as a design approach for fatigue failure for components with ultra-long fatigue lives and step loading. This design approach uses the master curve for Optically Dark Area (ODA) growth obtained by Murakami et al. and combines it with the prediction of the largest non-metallic inclusion along with the estimate of the fatigue life of the component.  The initiation and growth of small cracks from inclusions as well as small Focused Ion Beam (FIB) notches behave in a similar manner and show a strong tendency to follow the local microstructure. The effect of the local microstructure on the small fatigue crack growth is studied using FIB milling to create cross-sections of the microstructure. This showed that the microstructure is also linked to the formation of ODA around non-metallic inclusions in ultra-long fatigue. The behaviour of a small crack growing from notches in high cycle fatigue is studied by using high-speed microscopy and Rumul fatigue testing machines. The test results show that small cracks initiate and grow quickly in the beginning of the fatigue life after which they propagate slowly at a stress intensity range lower than the large crack growth threshold until it is reached.  Comparing different data results for different R-ratios shows that the parameter ΔK+ works well to compare the crack growth rate of small cracks in the studied quenched and tempered steel. For crack arrest the ΔK+ or Kmax thresholds are lower for cracks with higher compressive loading. Also test results showed that increasing only the compressive portion of loading can reinitiate arrested small cracks. Finally, the ΔK+ or Kmax values for small cracks are lower for similar crack growth rates under larger compressive loads. en
dc.format.extent 90 + app. 68
dc.format.mimetype application/pdf en
dc.language.iso en en
dc.publisher Aalto University en
dc.publisher Aalto-yliopisto fi
dc.relation.ispartofseries Aalto University publication series DOCTORAL DISSERTATIONS en
dc.relation.ispartofseries 191/2017
dc.relation.ispartofseries VTT Science en
dc.relation.ispartofseries 166
dc.relation.haspart [Publication 1]: A. Roiko, H. Hänninen, H. Vuorikari, Anisotropic distribution of non-metallic inclusions in a forged steel roll and its influence on fatigue limit, International Journal of Fatigue, Volume 41, August 2012, Pages 158-167, ISSN 0142-1123. DOI: 10.1016/j.ijfatigue.2011.12.023
dc.relation.haspart [Publication 2]: A. Roiko, Y. Murakami, A design approach for components in ultralong fatigue life with step loading, International Journal of Fatigue, Volume 41, August 2012, Pages 140-149, ISSN 0142-1123. DOI: 10.1016/j.ijfatigue.2011.12.021
dc.relation.haspart [Publication 3]: A. Roiko, J. Solin, Measurement of small cracks initiating from inclusions, Focused Ion Beam notches and drilled holes, International Journal of Fatigue, Volume 62, May 2014, Pages 154-158, ISSN 0142-1123. DOI: 10.1016/j.ijfatigue.2013.03.010
dc.relation.haspart [Publication 4]: A. Roiko, J. Solin, T. Sarikka, H. Hänninen, The paths of small fatigue cracks in high-strength steels initiated from inclusions and small defects, Accepted at: Materials Performance and Characterization on 21.4.2017
dc.relation.haspart [Publication 5]: A. Roiko, J. Solin, H. Hänninen, Behavior of small cracks under negative stress ratio fatigue loading, International Journal of Fatigue, Volume 104, 2017, Pages 379-388, ISSN 0142-1123. DOI: 10.1016/j.ijfatigue.2017.07.006
dc.relation.haspart [Publication 6]: A. Cetin, A. Roiko, M. Lind, Towards proper sampling and statistical modelling of defects. Fatigue & Fracture of Engineering Materials & Structures, Volume 38, September 2015, Pages 1056-1065, ISSN 1460-2695. DOI: 10.1111/ffe.12317
dc.subject.other Materials science en
dc.subject.other Mechanical engineering en
dc.title Interaction of non-metallic inclusions, microstructure, and fatigue loading with small crack growth in high-strength steels en
dc.type G5 Artikkeliväitöskirja fi
dc.contributor.school Insinööritieteiden korkeakoulu fi
dc.contributor.school School of Engineering en
dc.contributor.department Konetekniikan laitos fi
dc.contributor.department Department of Mechanical Engineering en
dc.subject.keyword non-metallic inclusions en
dc.subject.keyword small crack growth en
dc.subject.keyword fatigue en
dc.identifier.urn URN:ISBN:978-952-60-7648-5
dc.type.dcmitype text en
dc.type.ontasot Doctoral dissertation (article-based) en
dc.type.ontasot Väitöskirja (artikkeli) fi
dc.contributor.supervisor Hänninen, Hannu, Prof., Aalto University, Department of Mechanical Engineering, Finland
dc.opn Glinka, Gregory, Prof., University of Waterloo, Canada
dc.opn Lehtovaara, Arto, Prof., Tampere University of Technology, Finland
dc.contributor.lab Engineering Materials en
dc.rev Lehtovaara, Arto, Prof., Tampere University of Technology, Finland
dc.rev Härkegård, Gunnar, Prof. Emeritus, Norwegian University of Science and Technology, Norway
dc.date.defence 2017-10-27
local.aalto.formfolder 2017_10_17_klo_13_33
local.aalto.archive yes

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