• Search Research Projects
  • Search Researchers
  • How to Use
  1. Back to project page

2004 Fiscal Year Final Research Report Summary

The Effect of Vacuum on the Defect Size Dependence of Fatigue Crack Growth Limit (Aiming at Clarifying the Very High Cycle Fatigue Mechanism of High Strength Materials)

Research Project

Project/Area Number 15560056
Research Category

Grant-in-Aid for Scientific Research (C)

Allocation TypeSingle-year Grants
Section一般
Research Field Materials/Mechanics of materials
Research InstitutionHOKKAIDO UNIVERSITY

Principal Investigator

NAKAMURA Takashi  Hokkaido University, Graduate School of Engineering, Associate Professor, 大学院・工学研究科, 助教授 (30237408)

Project Period (FY) 2003 – 2004
KeywordsInterior Originating fracture / Surface Originating Fracture / Very High Cycle Fatigue / Fatigue Limit / High Vacuum / Small Crack / Fractography / Small Defect
Research Abstract

With respect to fatigue of high strength materials as high strength steel and Ti-alloy, in the very high cycle region over 10^7 to 10^8 cycles, fatigue fractures occur from the interior of the materials. Through our research till now, the research leader indicated that this phenomenon can be explained by assuming that the environment around interior-originating crack tip is similar to a high vacuum environment. To verify this assumption, in this research we conducted fatigue tests of micro-defective materials both in the air and in a vacuum using a vacuum rotating bending machine newly developed by the research leader for the purpose of (1)investigating fatigue behaviors originating from micro defects in a vacuum and clarifying an effectt of vacuum pressure on ΔK_<th>, and (2)investigating environmental effects around interior cracks by comparing initial fracture surface in a vacuum with that of interior cracks.
Testing involved fatigue tests under 10^<-3> -10^<-4> Pa vacuum pressure us … More ing high strength steel specimens with artificial defects of 30μm in diameter and 30μm in depth. The result showed the fatigue life in a vacuum showed approximately 3-4 times longer than those in the air. On the other hand, fatigue limit in a vacuum lowered approximately 50MPa compared with that in the air. In such case as the cracks originating from the very small defects, ΔK_<th> in a vacuum was revealed to be lowered compared with that in the air.
The initial fracture surfaces around micro-defects were analyzed by SEM. It has been known that around origins of interior cracks there are special surface areas consisting of concavo-convex pattern smaller than structure unit ; nevertheless, the surface of high strength steel under vacuum pressure of 10^<-3> -10^<-4> Pa did not show such special fracture surfaces. On the contrary, the experiment under 2x10^<-5>Pa vacuum pressure conducted showed such special fracture surface clearly particularly with Ti-alloy.
From the above, our assumption (underlined sentence described above) can explain the phenomena that interior fractures occur in low stress in the long life region, and at the same time, we assume environmental effects of interior originating cracks over initial crack propagation fracture surfaces, vacuum pressure in particular ; seem to be different based on materials. Less

  • Research Products

    (12 results)

All 2004 2003 Other

All Journal Article (12 results)

  • [Journal Article] The effects of stress ratios on very high cycle fatigue properties of Ti-6Al-4V2004

    • Author(s)
      H.Oguma, T.Nakamura
    • Journal Title

      Key Engineering Materials Vol.261-263

      Pages: 1227-1232

    • Description
      「研究成果報告書概要(和文)」より
  • [Journal Article] The effect of defect sizes on initial crack propagations of Ti-6Al-4V in high vacuum environment2004

    • Author(s)
      T.Nakamura, T.Shiina, S.Yokoyama, T.Noguchi
    • Journal Title

      Proceedings of the 3rd International Conference on Very High Cycle Fatigue, VHCF-3

      Pages: 569-576

    • Description
      「研究成果報告書概要(和文)」より
  • [Journal Article] Charecteristics of initial fatigue crack propagation process of Ti-6Al-4V in very high cycle fatigue2004

    • Author(s)
      T.Nakamura, H.Oguma, S.Yokoyama, T.Noguchi
    • Journal Title

      Proceedings of the 3rd International Conference on Very High Cycle Fatigue, VHCF-3

      Pages: 201-208

    • Description
      「研究成果報告書概要(和文)」より
  • [Journal Article] The effects of stress ratios on very high cycle fatigue properties of Ti-6Al-4V2004

    • Author(s)
      Hiroyuki.OGUMA, Takashi NAKAMURA
    • Journal Title

      Key Engineering Materials Vol.261-263

      Pages: 1227-1232

    • Description
      「研究成果報告書概要(欧文)」より
  • [Journal Article] The effect of defect sizes on initial crack propagations of Ti-6Al-4V in high vacuum environment2004

    • Author(s)
      Takashi NAKAMURA, Takahiro SHIINA, Shuji YOKOYAMA, Toru NOGUCHI
    • Journal Title

      Proceedings of the 3rd International Conference on Very High Cycle Fatigue VHCF-3

      Pages: 569-576

    • Description
      「研究成果報告書概要(欧文)」より
  • [Journal Article] Charecteristics of initial fatigue crack propagation process of Ti-6Al-4V in very high cycle fatigue2004

    • Author(s)
      Takashi NAKAMURA, Hiroyuki OGUMA, Shuji YOKOYAMA, Toru NOGUCHI
    • Journal Title

      Proceedings of the 3rd International Conference on Very High Cycle Fatigue VHCF-3

      Pages: 201-208

    • Description
      「研究成果報告書概要(欧文)」より
  • [Journal Article] 高強度鋼の引張圧縮軸荷重下における超高サイクル疲労特性2003

    • Author(s)
      椎名貴弘, 中村 孝, 野口 徹
    • Journal Title

      日本機械学会2003年度年次大会講演論文集 I巻

      Pages: 171-172

    • Description
      「研究成果報告書概要(和文)」より
  • [Journal Article] Ti-6Al-4Vの内部起点型疲労特性に及ぼす応力比の影響2003

    • Author(s)
      中村 孝, 小熊博幸, 野口 徹, 園生義人
    • Journal Title

      日本機械学会2003年度年次大会講演論文集 I巻

      Pages: 173-174

    • Description
      「研究成果報告書概要(和文)」より
  • [Journal Article] Effects of high vacuum environment on high cycle fatigue properties of Ti-6Al-4V2003

    • Author(s)
      T.Shiina.T.Nakamura, T.Noguchi
    • Journal Title

      Proceedings of the International Conference on Advanced Technology in Experimental Mechanics, ATEM'03 (CD-ROM)

    • Description
      「研究成果報告書概要(和文)」より
  • [Journal Article] Very high cycle fatigue properties of high strength steel under uniaxial tension compression loading2003

    • Author(s)
      Takahiro SHIINA, Takashi NAKAMURA, Torn NOGUCHI
    • Journal Title

      Proceedings of the 2003 Annual Meeting of JSME Vol.1

      Pages: 171-172

    • Description
      「研究成果報告書概要(欧文)」より
  • [Journal Article] Effects of stress ratios on interior originating fatigue properties of Ti-6Al-4V2003

    • Author(s)
      Takashi NAKAMURA, Hiroyuki OGUMA, Toru NOGUCHI, Yoshito SONOU
    • Journal Title

      Proceedings of the 2003 Annual Meeting of JSME Vol.1

      Pages: 173-174

    • Description
      「研究成果報告書概要(欧文)」より
  • [Journal Article] Effects of high vacuum environment on high cycle fatigue properties of Ti-6Al-4V

    • Author(s)
      Takahiro SHIINA, Takashi NAKAMURA, Toru NOGUCHI
    • Journal Title

      Proceedings of the International Conference on Advanced Technology in Experimental Mechanics, ATEM'03 (CD-ROM)

    • Description
      「研究成果報告書概要(欧文)」より

URL: 

Published: 2006-07-11  

Information User Guide FAQ News Terms of Use Attribution of KAKENHI

Powered by NII kakenhi