Effect of Crack Closure on the Fatigue Limit of Material Containing Small Defect

Masahiro Kashiwagi, Takao Kudou, Masanobu Kubota, Chu Sakae, Yoshiyuki Kondo

Research output: Contribution to journalArticle

7 Citations (Scopus)


It has been recognized that the threshold stress intensity factor range Delta;Kth of short crack is dependent on many factors. Fatigue tests were performed on materials containing small defects under a wide range of mean stress for three grades of steels with different hardness. Strong dependencies of ΔKth on material hardness, mean stress and defect size were observed. Major tendencies such that softer material had lower ΔK th and smaller defect had lower ΔKth were obtained, which were quite different from those of long cracks. The causes of these effects were investigated based on the crack closure behavior of short crack. The crack closure measurement on a very shallow crack was done. Test results showed that softer material and shorter crack had lower crack closure stresses. It was shown that the threshold effective stress intensity factor range (ΔKeff)th was a unique value for defects deeper than 0.1mm. The crack closure was the major cause of the abovementioned effects of material hardness and mean stress for defects deeper than 0.1mm. On the contrary, (ΔKeff)th significantly decreased compared with that for long cracks when the defect was shallower than 0.1mm. This is another short crack effect which could not be explained only by the crack closure. It was shown that (ΔKeff)th was no more a unique value when the defect depth was shallower than 0.1mm.

Original languageEnglish
Pages (from-to)1345-1350
Number of pages6
JournalZairyo/Journal of the Society of Materials Science, Japan
Issue number11
Publication statusPublished - Nov 2003

All Science Journal Classification (ASJC) codes

  • Materials Science(all)
  • Condensed Matter Physics
  • Mechanics of Materials
  • Mechanical Engineering

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