Interaction effect of adjacent small defects on the fatigue limit of a medium carbon steel

M. Åman*, S. Okazaki, H. Matsunaga, G. B. Marquis, H. Remes

*Corresponding author for this work

Research output: Contribution to journalArticleScientificpeer-review

21 Citations (Scopus)
208 Downloads (Pure)


Structural steels contain various material irregularities and natural defects which cause local stress concentrations from which fatigue cracks tend to initiate. Two defects in close proximity to each other may affect local stress distributions, and thus, begin to interact. In this paper, the effect of interacting small cracks on the fatigue limit is systematically investigated in a medium carbon steel. The growth of interacting cracks, as well as the characteristics of non-propagating cracks and microstructural aspects, was closely examined via the plastic replica method. It was found that although the fatigue limit is essentially controlled by the mechanics of interacting cracks, based on their configuration, the local microstructure comprised ferrite and pearlite has a statistical scatter effect on the behaviour of interacting cracks and non-propagating thresholds. With respect to the fatigue limit, when two defects were in close proximity, they behaved as a larger single defect. However, with greater spacing between defects, rather than mechanical factors, it is the local microstructure which determines the location and characteristics of non-propagating cracks.

Original languageEnglish
Pages (from-to)130-144
Number of pages15
JournalFatigue and Fracture of Engineering Materials and Structures
Issue number1
Early online date2016
Publication statusPublished - 2017
MoE publication typeA1 Journal article-refereed


  • Fatigue limit
  • Interacting cracks
  • Interaction effect
  • Medium carbon steel
  • Non-propagating crack
  • Small crack


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