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Study on Elastic-Plastic Fatigue Crack Growth under Service Loading Conditions

Research Project

Project/Area Number 60550054
Research Category

Grant-in-Aid for General Scientific Research (C)

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

Principal Investigator

MASAHIRO Jono  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 Atsusi  Faculty of Engineering, Osaka University, Research Assistant, 工学部, 助手 (60162913)
Project Period (FY) 1985 – 1986
Project Status Completed (Fiscal Year 1986)
Budget Amount *help
¥1,900,000 (Direct Cost: ¥1,900,000)
Fiscal Year 1986: ¥600,000 (Direct Cost: ¥600,000)
Fiscal Year 1985: ¥1,300,000 (Direct Cost: ¥1,300,000)
KeywordsElastic-Plastic Fatigue Crack / Varying Loading / Crack Growth Rate / Crack Closure / Cyclic Deformation / One-Directional Deformation / Effective Stress Intensity Factor / 繰返しJ積分
Research Abstract

Engineering structures are often subjected to large amplitude loads in service which exceed the yield conditions of materials. Therefore, it becomes important to know an estimation method of elastic-plastic fatigue crack growth rates under varying loading conditions, in order to secure the safety of structures in damage tolerant design. From this point of view, in this study, load controlled fatigue crack growth tests were carried out on several kinds of structural materials under constant and variable amplitude loads over a wide range from the linear elastic region to the post-yield one, and fracture mechanics parameters which governed the fatigue crack growth rates were investigated. Crack growth increment and crack closure behavior were monitored through fatigue tests by the minicomputer-aided unloading elastic compliance method.
The effective stress intensity range, <DELTA> Keff, was found to be a governing parameter of fatigue crack growth rate even in the large scale yielding region within the limit conditions as well as in the linear elastic region. In the post-yield region, however, cyclic plastic deformation and fatigue induced one-directional deformation took place remarkably depending on materials, specimen configurations and stress ratios, and affected crack growth behaviors. It was found that these effects could be explained by considering the cyclic J-integral, <DELTA> J, and the maximum J-integral, Jmax, and the elastic-plastic fatigue crack growth rate could be expressted by the power law of <DELTA> J/E(1-Jmax/C) irrespective of materials, specimen configurations and test conditions. From the test results with repeated two-step loadings simulating several kinds of service loadings, it was found that the elastic-plastic fatigue crack growth rate under varying loading conditions could be well estimated based on the linear accumulation law of crack growth using the above mentioned fracture mechanics parameter.

Report

(1 results)
  • 1986 Final Research Report Summary
  • Research Products

    (6 results)

All Other

All Publications (6 results)

  • [Publications] 城野政弘: 材料. 34. 561-567 (1985)

    • Description
      「研究成果報告書概要(和文)」より
    • Related Report
      1986 Final Research Report Summary
  • [Publications] 城野政弘: 日本機械学会論文集A編. 52. 1257-1263 (1986)

    • Description
      「研究成果報告書概要(和文)」より
    • Related Report
      1986 Final Research Report Summary
  • [Publications] M.Jono: Proceeding of Role of Fracture Mechanics in Modern Technology,Kyushu.1986. (1987)

    • Description
      「研究成果報告書概要(和文)」より
    • Related Report
      1986 Final Research Report Summary
  • [Publications] Masahiro JONO: "Elastic-Plastic Fatigue Crack Growth under Load Control (The Limit of Validity of Linear Fracture Mechanics Parameters and the Effect of Plasticity)" Journal of The Society of Materials Science, Japan. 34. 561-567 (1985)

    • Description
      「研究成果報告書概要(欧文)」より
    • Related Report
      1986 Final Research Report Summary
  • [Publications] Masahiro JONO: "Elastic-Plastic Fatigue Crack Growth Behavior under Repeated Two-Step Loading" Trans. of The Japan Society of Mechanical Engineers. 52. 1257-1263 (1986)

    • Description
      「研究成果報告書概要(欧文)」より
    • Related Report
      1986 Final Research Report Summary
  • [Publications] Masahiro JONO: "Elastic-Plastic Fatigue Crack Growth Behavior under Varying Loading Conditions" Proc. of Int. Conf. on Role of Fracture Mechanics in Modern Technology, Fukuoka, 1986. (1987)

    • Description
      「研究成果報告書概要(欧文)」より
    • Related Report
      1986 Final Research Report Summary

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Published: 1987-03-31   Modified: 2016-04-21  

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