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Estimating inclusion content in high performance steels
Karlstads universitet, Avdelningen för maskin- och materialteknik. (Maskinteknik)ORCID iD: 0000-0003-1655-0392
2008 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

Non-metallic inclusions in steel pose a major problem for the fatigue resistance, especially regarding fatigue at very long lives corresponding to low cyclic stress levels, as well as being detrimental to material toughness and polishability.

The largest inclusions are quite rare, which makes conventional detection methods timeconsuming if reliable results are to be obtained. Based on surface scanning using light or electron microscopes, these methods provide results that have to be converted to reflect the statistical volume distribution of inclusions.

Very high cycle fatigue (in the order of 109 cycles or more) using ultrasonic fatigue at 20 kHz has been found efficient at finding the largest inclusions in volumes of about 300 mm3 per specimen. The inclusions found at the fatigue initiation site can then been used to estimate the distribution of large inclusions using extreme value statistics.

In this work, a new method for estimating the volume distribution of large inclusions is presented as well as a suggested ranking variable based on the volume distribution.

Results from fatigue fractography and area scanning methods are compared to the endurance limit at 109 cycles for a number of batches from two high performance steels.

In addition, the extreme value distributions of fatigue initiating inclusions in six high performace steels, produced by different routes, are presented. It is shown that all modes of the Generalized Extreme Values distribution can be found in different materials. This result shows that the assumption of mode I distribution, also known as Gumbel or Largest Extreme Value distribution, must be substantiated.

Place, publisher, year, edition, pages
Karlstad: Karlstad University , 2008. , p. 18
Series
Karlstad University Studies, ISSN 1403-8099 ; 2008:50
National Category
Materials Engineering
Research subject
Materials Engineering
Identifiers
URN: urn:nbn:se:oru:diva-39896ISBN: 978-91-7063-207-5 (print)OAI: oai:DiVA.org:oru-39896DiVA, id: diva2:773467
Presentation
2008-12-19, Ljungbergssalen, 21A 244, Karlstads universitet, 13:15 (Swedish)
Opponent
Supervisors
Available from: 2015-01-02 Created: 2014-12-19 Last updated: 2017-10-17Bibliographically approved
List of papers
1. Relating gigacycle fatigue to other methods in evaluating the inclusion distribution of a H13 tool steel
Open this publication in new window or tab >>Relating gigacycle fatigue to other methods in evaluating the inclusion distribution of a H13 tool steel
2007 (English)In: Fourth International Conference on Very High Cycle Fatigue (VHCF-4) / [ed] John E. Allison, J. Wayne Jones, James M. Larsen & Robert O. Ritchie, TMS (The Minerals, Metals & Materials Society) , 2007, p. 45-50Conference paper, Published paper (Refereed)
Abstract [en]

Inclusions play a crucial role for the fatigue properties of high strength steel, but to find the largest inclusions by microscopy measurements large areas have to be examined.In this study ultrasonic gigacycle staircase fatigue testing has been used to find large inclusions in an H13 tool steel. The inclusions have been examined in SEM and their size distribution modeled using methods from extreme value statistics. The inclusion distribution obtained from the fatigue crack surfaces is compared to distributions acquired by microscopy study of cross sections as well as ultrasound immersion tank measurements and to the corresponding staircase fatigue data via the Murakami √Area model.It is shown that the fatigue method more effectively finds large inclusions than the other methods. It is also shown that the correlation between predictions of inclusion sizes by the √Area model from stress levels and fatigue initiating inclusions is weak forthis material.

Place, publisher, year, edition, pages
TMS (The Minerals, Metals & Materials Society), 2007
Keywords
non-metallic inclusion, steel, gigacycle fatigue
National Category
Materials Engineering
Research subject
Materials Engineering
Identifiers
urn:nbn:se:oru:diva-39905 (URN)978-0-87339-704-9 (ISBN)
Conference
Fourth International Conference on Very High Cycle Fatigue (VHCF-4)
Available from: 2009-02-05 Created: 2014-12-19 Last updated: 2017-10-17Bibliographically approved
2. Detecting large inclusions in steels: evaluating methods
Open this publication in new window or tab >>Detecting large inclusions in steels: evaluating methods
(English)Manuscript (preprint) (Other academic)
National Category
Metallurgy and Metallic Materials
Identifiers
urn:nbn:se:oru:diva-40114 (URN)
Available from: 2015-01-02 Created: 2015-01-02 Last updated: 2017-10-17Bibliographically approved
3. Extreme value distributions of inclusions in six steels
Open this publication in new window or tab >>Extreme value distributions of inclusions in six steels
(English)Manuscript (preprint) (Other academic)
National Category
Metallurgy and Metallic Materials
Identifiers
urn:nbn:se:oru:diva-40117 (URN)
Available from: 2015-01-02 Created: 2015-01-02 Last updated: 2017-10-17Bibliographically approved
4. Finding non-metallic inclusions in clean steel
Open this publication in new window or tab >>Finding non-metallic inclusions in clean steel
2008 (English)Report (Other academic)
Place, publisher, year, edition, pages
Karlstad: Karlstads universitet, 2008
Series
Karlstad University Studies, ISSN 1403-8099 ; 2008:51
National Category
Materials Engineering
Research subject
Materials Engineering
Identifiers
urn:nbn:se:oru:diva-39895 (URN)978-91-7063-208-2 (ISBN)
Available from: 2009-02-05 Created: 2014-12-19 Last updated: 2017-10-17Bibliographically approved

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Ekengren, Jens

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Citation style
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  • harvard1
  • ieee
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