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SUBSURFACE CRACK INITIATION IN HIGH CYCLE FATIGUE AT CRYOGENIC TEMPERATURES.

[In Japanese. / En japonais.]

Author(s) : UMEZAWA O.

Type of article: Article

Summary

IN CRYOGENIC HIGH CYCLE FATIGUE FOR TITANIUM ALLOYS AND NITROGEN-STRENGTHENED AUSTENITIC STEELS, SUBSURFACE CRACK INITIATION APPARENTLY OCCURS WITHOUT THE EXISTENCE OF ANY DEFECTS LIKE INCLUSION AND PORE. MICROSTRUCTURAL ORIGIN OF SUBSURFACE CRACK INITIATION SITE AND DEFORMATION BEHAVIOUR FOR THOSE ALLOYS WERE INVESTIGATED, AND THE MECHANISM OF SUBSURFACE CRACK INITIATION IS DISCUSSED. SUBSURFACE CRACK INITIATION SITE CONSISTS OF FACETS WHICH ARE ASSIGNED THEIR MICROSTRUCTURE. SUBSURFACE CRACK INITIATION IS CAUSED BY A MICROCRACKING RELATED TO MICROSTRUCTURAL INHOMOGENEITY. A PRINCIPAL SLIP SYSTEM IS DOMINANT DEFORMATION MODE, AND DISLOCATION MOTION IS PLANAR. EVEN AT LOWER STRESS LEVEL, PILED-UP DISLOCATIONS OF SHORT RANGE ORDER ARE BLOCKED OR SHARPLY LOCALIZED AT GRAIN BOUNDARIES. NAMELY, THE STRESS CONCENTRATION AT GRAIN BOUNDARY OCCURS LOCALLY. THEN THE STRESS CONCENTRATION MIGHT PRODUCE THE MICROCRACKING. ON ON THE MAXIMUM STRESS RANGE. THEREFORE, ACCORDING TO THE SUBSURFACE CRACK INITIATION MECHANISM, A MICROCRACKING DUE TO LOCALIZED DEFORMATION WOULD GROW OR COALESCE UNTIL IT REACHES A CRITICAL CRACK SIZE AND IS CHOSEN FOR THE MAIN CRACK.

Details

  • Original title: [In Japanese. / En japonais.]
  • Record ID : 1992-0940
  • Languages: Japanese
  • Source: Cryogenics/ Cryog. Eng. - vol. 26 - n. 4
  • Publication date: 1991
  • Document available for consultation in the library of the IIR headquarters only.

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