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2001 Fiscal Year Final Research Report Summary

Supposition of the Interior Originating Fatigue Fracture Mechanism of Titanium Alloy Based on the Surface Small Crack Growth Properties in High Vacuum

Research Project

Project/Area Number 12650066
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 Univ., Grad. School of Eng., Asso. Prof., 大学院・工学研究科, 助教授 (30237408)

Co-Investigator(Kenkyū-buntansha) NOGUCHI Toru  Hokkaido Univ., Grad. School of Eng., Prof., 大学院・工学研究科, 教授 (80001220)
Project Period (FY) 2000 – 2001
KeywordsInterior Originating Fracture / Surface Originating Fracture / Very High Cycle Fatigue / Fatigue Limit / High Vacuum / Ti-6A1-4V / Small Crack / Fractography
Research Abstract

Recently, some researchers reported that fatigue fracture in Ti alloy occurred from interior of the material in very high cycle over 10^7-10^8. The reason of this phenomenon has not been clarified. This study focused on the environment of the material where crack surface is not exposed to ambient air, and carried out fatigue experiments in high vacuum using specimens with small artificial defect. We investigated the mechanism of interior fatigue fracture by comparing crack propagation processes in air, vacuum and inside environment of the material. As a result, the following were obtained :
1. A high vacuum environment improved the fatigue life drastically.
2. The threshold of crack propagation was determined by the initiation of the crack in air whereas by the arrest of the crack in vacuum. The latter phenomenon coincided with the dominant factor of fatigue limit of interior fracture.
3. Transitional stress intensity factor from stage 2a to stage 2b process decreased in high vacuum as compared with in air. This could be explained by the decrease of the local yield stress at crack tip. The longer fatigue life in high vacuum was considered to result from the lower efficiency of the adsorbed film, which facilitated the plastic deformation at crack tip.
4. The tendency of longer fatigue life of interior originating fracture coincided with that in high vacuum. However, fatigue life in high vacuum was much longer than interior fracture. Fracture surfaces of interior fracture were more similar to those of surface fracture in high vacuum than in air, but they did not completely correspond to those in high vacuum. It seemed that the interior environment of material was not equal to high vacuum, and that the amount of gaseous molecule which affected crack propagation, was larger in the interior of the material than in high vacuum.

  • Research Products

    (12 results)

All Other

All Publications (12 results)

  • [Publications] 中村 孝: "超高サイクル疲労と試験技術"材料試験技術. 46巻・1号. 15-25 (2001)

    • Description
      「研究成果報告書概要(和文)」より
  • [Publications] 小熊博幸, 中村 孝, 杉野淳一, 野口 徹: "Ti-6Al-4V合金の高サイクル疲労特性と応力比の相関"日本機械学会材料力学部門講演会講演論文集. No.01-16. 247-248 (2001)

    • Description
      「研究成果報告書概要(和文)」より
  • [Publications] 小熊博幸, 中村 孝, 野口 徹: "Ti-6Al-4V合金の疲労寿命分布特性と破壊形態"材料. 50巻・10号. 1074-1079 (2001)

    • Description
      「研究成果報告書概要(和文)」より
  • [Publications] T.Nakamura: "The Effect of High Vacuum Environment on Ultra-Long-Life Fatigue of Titanium Alloy"Taiwan-Japan Joint Workshop on Aerospace Engineering Mechanics. 58-58 (2001)

    • Description
      「研究成果報告書概要(和文)」より
  • [Publications] T.Nakamura, Toru Noguchi: "Very High Cycle Fatigue Properties of Ti-6Al-4V Focused on Interior Environment of Material"Proceedings of the 3^<rd> International Joint Symposium of Hokkaido University and Chungnam National University. 27-32 (2001)

    • Description
      「研究成果報告書概要(和文)」より
  • [Publications] T.Nakamura, T.Noguchi, H.Oguma: "Gigacycle Fatigue Properties of Ti-6Al-4V under Uniaxial Tension"Proceedings of the 8th International Fatigue Congress, FATIGUE'02, decided to be issued. (2002)

    • Description
      「研究成果報告書概要(和文)」より
  • [Publications] Takashi NAKAMURA: "Very High Cycle Fatigue and its Testing Technology"Journal of Material Testing Research Association of Japan. Vol.46, No.1. 15-25 (2001)

    • Description
      「研究成果報告書概要(欧文)」より
  • [Publications] Hiroyuki OGUMA, Takashi NAKAMURA, Junichi SUGINO, Toru NOGUCHI: "The Relation between High-cycle Fatigue Characteristics and Stress Ratio of Ti-6A1-4V Alloy"Proceedings of the 2001 Annual Meeting of JSME/MMD. No.01-16. 247-248 (2001)

    • Description
      「研究成果報告書概要(欧文)」より
  • [Publications] Hiroyuki OGUMA, Takashi NAKAMURA, Toru NOGUCHI: "Fatigue Life Distribution and Fracture Types of T1-6A1-4V Alloy"Journal of the Society of Material Science Japan. Vol. 50, No. 10. 1074-1079 (2001)

    • Description
      「研究成果報告書概要(欧文)」より
  • [Publications] Takashi NAKAMURA: "The Effect of High Vacuum Environment on Ultra-Long-Life Fatigue of Titanium Alloy"Taiwan-Japan Joint Workshop on Aerospace Engineering Mechanics. 58 (2001)

    • Description
      「研究成果報告書概要(欧文)」より
  • [Publications] Takashi NAKAMURA, Toru NOGUCHI: "Very High Cycle Fatigue Properties of Ti-6A1-4V Focused on Interior Environment of Material"Proceedings of the 3rd International Joint Symposium of Hokkaido University and Chungnam National University. 27-32 (2001)

    • Description
      「研究成果報告書概要(欧文)」より
  • [Publications] Takashi NAKAMURA, Hiroyuki OGUMA, Toru NOGUCHI: "Gigacycle Fatigue Properties of Ti-6A1-4V under Uniaxial Tension"Proceedings of the 8th International Fatigue Congress, FATIGUE '02, (June, 2002, @Stockholm, Sweden). (decided to be issued).

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

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Published: 2003-09-17  

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