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1988 Fiscal Year Final Research Report Summary

Development of Environment Adjusting Device for Fatigue Testing Apparatus Installed to Field Emission Type Scanning Electron Microscope and Study on Crack Closure Mechanism

Research Project

Project/Area Number 62850019
Research Category

Grant-in-Aid for Developmental Scientific Research

Allocation TypeSingle-year Grants
Research Field 機械材料工学
Research InstitutionOsaka University

Principal Investigator

JONO Masahiro  Faculty of Engineering, Osaka University, Professor, 工学部, 教授 (20029094)

Co-Investigator(Kenkyū-buntansha) YASUI Kazuo  Faculty of Engineering, Osaka University, Research Assistant, 工学部, 助手 (50029047)
SUGETA Atsushi  Faculty of Engineering, Osaka University, Research Assistant, 工学部, 助手 (60162913)
Project Period (FY) 1987 – 1988
KeywordsField Emission Type Scanning Electron Microscope / Direct Observation / Fatigue Crack / Environment Adjusting Device / Crack Closure / Vacuum Environment / Unloading Elastic Compliance Method / コンピュータ制御
Research Abstract

Since the fatigue phenomenon is considered to be intrinsically localized in a very small portion of material,microscopic study becomes useful to identify the detailed mechanism of it, and attempts such as direct observations of grow-ing fatigue crack have been made by using a specially designed fatigue testing apparatus which can operate in the specimen chamber of the scanning electron microscope(SEM). however, it is feared that the vacuum environment of specimen chamber of the SEM can affect the observed fatigue crack growth and closure behaviors. From this point of view, in this study, an environment adjusting device which can supply desirable gases to the near portion of fatigue crack tip in the specimen chamber has been developed, and direct observations of fatigue crack both in air and vacuum environments were made with the aid of micro-com-puter control.
Fatigue crack opening point was found higher in vacuum than in air for Mode I crack of grain oriented silicon iron, suggesting t … More hat the rewelding of crack tip in vacuum is related to crack closure and oxide induced crack closure is not dominant for Mode I crack. Through the test on randomly oriented silicon iron,it was found that grain orientation and grain boundary strongly affect fatigue crack growth direction and crack closure in the relatively low growth rate regime. However, the effect of grain orientation seemed to disappear in the high growth rate region.
In addition, the effects of air and vacuum environments and microstructure of the materials on fatigue crack closure behaviors were investigated on four kinds of P/M aluminum alloys and Ni-Cr steel based on the fracture mechanics and fractographical studies. Crack opening points in air were found to depend on the roughness of fracture surfaces, indicating the importance of roughness induced crack closure at the low groth rate regime in air. On the other hand, those in vacuum were found almost constant irrespective of surface roughness. Cyclic softening characteristics of the material was found to affect crack closure. Less

  • Research Products

    (11 results)

All Other

All Publications (11 results)

  • [Publications] 城野政弘: 日本機械学会論文集(A編). 53. 1993-1998 (1987)

    • Description
      「研究成果報告書概要(和文)」より
  • [Publications] Masahiro Jono: Proc.6th Int. Congr.on Experimental Mechanics. 2. 801-806 (1988)

    • Description
      「研究成果報告書概要(和文)」より
  • [Publications] 城野政弘: 材料. 37. 1204-1208 (1988)

    • Description
      「研究成果報告書概要(和文)」より
  • [Publications] 楊徳統: 材料. (1989)

    • Description
      「研究成果報告書概要(和文)」より
  • [Publications] 城野政弘: 日本材料学会第48回破壊力学部門委員会. (1988)

    • Description
      「研究成果報告書概要(和文)」より
  • [Publications] 城野政弘: 日本機械学会関西支部第64期定時総会講演概要集. (1989)

    • Description
      「研究成果報告書概要(和文)」より
  • [Publications] Masahiro,Jono: "Fatigue Crack Growth and Crack Closure of P/M Aluminum Alloys" Trnas. of The Japan Society of Mechanical Engineers. 53(A). 1993-1998 (1987)

    • Description
      「研究成果報告書概要(欧文)」より
  • [Publications] Masahiro,Jono: "In-situ Observations of Growing Fatigue Crack by Field Emission Type Scanning Electron Microscope" Proc. of 6th International Congress on Experimental Mechanics. 2. 801-806 (1988)

    • Description
      「研究成果報告書概要(欧文)」より
  • [Publications] Masahiro,Jono: "Direct, Real Time Observation of Fatigue Crack Growth Using a Field Emission Type SEM (Effects of Grain Orientation and Grain Boundary on Fatigue Crack Growth)" Journal of The Society of Materials Science, Japan. 37. 1204-1208 (1988)

    • Description
      「研究成果報告書概要(欧文)」より
  • [Publications] Masahiro,Jono: "Direct Observation and Growth Mechanism of Fatigue Crack" Committee Material of Fracture Mechanics, 48th, JSMS. (1988)

    • Description
      「研究成果報告書概要(欧文)」より
  • [Publications] Masahiro,Jono: "Direct Observation of Fatigue Crack Using SEM and Development of Image Processing Technique" Preprint of The Japan Society of Mechanical Engineers, 64th Kansai District Meeting. (1989)

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

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Published: 1990-12-19  

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