Interpretation of material hardness, stress ratio, and crack size effects on the ΔKth of small cracks based on crack closure measurement

Y. Kondo, C. Sakae, Masanobu Kubota, M. Kashiwagi

Research output: Contribution to journalArticle

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Abstract

Fatigue tests were performed on materials containing small cracks to investigate the effects of material hardness, mean stress, and crack size on the threshold stress intensity factor of small cracks. The crack closure measurement on a very small crack was done. Although most of those effects could be explained by the characteristic behavior of crack closure in small cracks, it was also shown that (ΔKeff)th was also affected by crack size. The combination of (ΔKeff) th and the crack closure behaviors caused the peculiar characteristics of ΔKth in small cracks. At an extremely high R region, an unusual decrease in ΔKth was found to occur. The large reduction occurred under the conjunction of three factors: extremely high stress ratio higher than 0.8, shallow crack less than a few tenths of a millimeter, and hard material whose HV is higher than 300. The near-threshold fatigue crack propagation rate could be uniquely evaluated even in such a short crack regime using the effective stress intensity factor with the following modification {ΔKeff - (ΔKeff)th,a}. This expression could be applicable in the short crack regime. ΔK eff still plays a role as the governing parameter for fatigue crack propagation of short crack as short as 0.04 mm.

Original languageEnglish
Pages (from-to)69-83
Number of pages15
JournalJournal of ASTM International
Volume2
Issue number4
DOIs
Publication statusPublished - Apr 1 2005

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Crack closure
Hardness
Fatigue
Cracks
Fatigue crack propagation
Stress intensity factors
Fatigue of materials

All Science Journal Classification (ASJC) codes

  • Environmental Engineering
  • Materials Science(all)
  • Nuclear Energy and Engineering
  • Engineering(all)
  • Public Health, Environmental and Occupational Health

Cite this

Interpretation of material hardness, stress ratio, and crack size effects on the ΔKth of small cracks based on crack closure measurement. / Kondo, Y.; Sakae, C.; Kubota, Masanobu; Kashiwagi, M.

In: Journal of ASTM International, Vol. 2, No. 4, 01.04.2005, p. 69-83.

Research output: Contribution to journalArticle

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