Large reduction in the (ΔKeff)th of short crack at extremely high stress ratio

Yoshiyuki Kondo, Chu Sakae, Masanobu Kubota, Takao Kudou

Research output: Contribution to journalArticle

1 Citation (Scopus)

Abstract

It has been recognized that the threshold stress intensity factor Delta;Kth of short crack is dependent on many factors. Dependencies of Delta;Kth on material hardness, mean stress and crack size could be successfully evaluated on the basis of crack closure phenomenon. As a consequence, the (Delta;Keff)th was almost constant for a wide range of conditions. In this study, however, extraordinary decrease in the (Delta;Keff)th was found to occur in some limited condition. It was shown that the reduction was caused by the conjunction of three conditions, namely, high stress ratio (R) larger than 0.8, short crack and hard material whose Vickers hardness was higher than 300. The lowest value of (Delta;Keff)th obtained in this study was 0.7MPam 1/2 for steel. The fracture surface morphology was trans-granular and no indication of environmental effect was found. The fatigue crack propagation rate near the threshold condition could be uniquely evaluated even in such a short crack regime using the effective stress intensity factor with the following modification {Delta;Keff - (Delta;Keff) th.a} Here, (Delta;Keff)th.a is the (Delta;Keff)th for crack length a. This evaluation could be applicable in short crack regime as short as 0.04mm. Delta;Keff still plays a role as the governing parameter for fatigue crack propagation of short crack.

Original languageEnglish
Pages (from-to)661-666
Number of pages6
JournalZairyo/Journal of the Society of Materials Science, Japan
Volume53
Issue number6
DOIs
Publication statusPublished - Jan 1 2004

Fingerprint

short cracks
stress ratio
Cracks
Fatigue crack propagation
Stress intensity factors
stress intensity factors
crack propagation
Crack closure
Vickers hardness
Steel
cracks
crack closure
Surface morphology
Environmental impact
conjunction
thresholds
Hardness
indication
hardness

All Science Journal Classification (ASJC) codes

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

Cite this

Large reduction in the (ΔKeff)th of short crack at extremely high stress ratio. / Kondo, Yoshiyuki; Sakae, Chu; Kubota, Masanobu; Kudou, Takao.

In: Zairyo/Journal of the Society of Materials Science, Japan, Vol. 53, No. 6, 01.01.2004, p. 661-666.

Research output: Contribution to journalArticle

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