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A Probabilistic Approach to the Fatigue Crack Propagation under Non-stationary Random Loading

Research Project

Project/Area Number 60460146
Research Category

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

Allocation TypeSingle-year Grants
Research Field 船舶構造・建造
Research InstitutionUniversity of Tokyo

Principal Investigator

MACHIDA Susumu  Univ.of Okyo, Faculty of Eng. , Professor, 工学部, 教授 (70010692)

Co-Investigator(Kenkyū-buntansha) KANEDA Shigehiro  Univ. of Tokyo, Faculty of Eng . , Associate, 工学部, 助手 (90010892)
NIIMURA Yutaka  Univ. of Tokyo , Faculty of Eng . , Associate, 工学部, 助手 (40010889)
YOSHINARI Hitoshi  Univ. of Tokyo , Faculty of Eng. , Associate Professor, 工学部, 助教授 (20167737)
NOMOTO Toshiharu  Univ. of Tokyo, Faculty of Eng. , Professor, 工学部, 教授 (80011170)
Project Period (FY) 1985 – 1987
Project Status Completed (Fiscal Year 1987)
Budget Amount *help
¥7,100,000 (Direct Cost: ¥7,100,000)
Fiscal Year 1987: ¥700,000 (Direct Cost: ¥700,000)
Fiscal Year 1986: ¥1,000,000 (Direct Cost: ¥1,000,000)
Fiscal Year 1985: ¥5,400,000 (Direct Cost: ¥5,400,000)
KeywordsFatigue crack propagation / Random loading / き裂開口応力
Research Abstract

Crack extention by fatigue may sometimes cause a catastrophic failure of structure. For the safety assessment of structure, it is indispensable to estimate fatigue crack growth under service loading. In most cases actual service load are random, and the estimating methor for fatigue crack growth under random loading must be setablished.
For practical use, it is very preferable that the prediction of fatigue behavior in real structures under random loading could be made using the data obtained by constant amplitude loading test which is simple and routine test. Many investigations have been carried out in order to clarify the releationship between fatigue behaviors under random loading and constant amplitude loading, recently based on the concept of "crack closure" proposed by Elber. In these investigations, however, pure random load has not been applied because of its complexity, and the relationship nas not been clarified yet.
In this study, fatigue crack propagation tests under random loading are carried out as well as constant amplitude loading tests for comparison. Crack closure phenomna of the specimens are automatically recorded over a long period of fatigue cycles aided by micro-computer system. It is shown that consideration of crack closure is essential for examination of fatigue crack growth and fatigue behavior under random loading may be predicted from constant amplitude test. Furthermore, fatigue tests are carried out under the condition of the same constant stress amplitude on many specimens. The results are analyzed using Bogdanoff's probabilistic model (B model) based on Markov chain concept. It is shown that the B model has the possibility for proveding a useful tool for examining the statistical properties of fatigus crack growth.

Report

(2 results)
  • 1987 Final Research Report Summary
  • 1986 Annual Research Report
  • Research Products

    (5 results)

All Other

All Publications (5 results)

  • [Publications] 町田進: 日本造船学会論文集. 160. 486-494 (1986)

    • Description
      「研究成果報告書概要(和文)」より
    • Related Report
      1987 Final Research Report Summary
  • [Publications] 町田進: 日本造船学会論文集. 162. 467-473 (1987)

    • Description
      「研究成果報告書概要(和文)」より
    • Related Report
      1987 Final Research Report Summary
  • [Publications] Susumu Machida: "Fatigue Crack Propagation under Service Loading (The 2nd Report) -Examination of Fatigue Crack Propagation under Narrow Band Random Loading based on Crack Closure Concept-" Journal of The Society of Naval Architects of Japan. 160. 486-494 (1986)

    • Description
      「研究成果報告書概要(欧文)」より
    • Related Report
      1987 Final Research Report Summary
  • [Publications] Susumu Machida: "Fatigue Crack Propagation under Service Lading (The 3er Report) -Estimatng Method for Fatigue Crack Growth under Narrow Band Random Loading-" Journal of The Society of Naval Architects of Japan. 162. 467-473 (1987)

    • Description
      「研究成果報告書概要(欧文)」より
    • Related Report
      1987 Final Research Report Summary
  • [Publications] 町田進,吉成仁志外: 日本造船学会論文集. 160号巻. 486-494 (1986)

    • Related Report
      1986 Annual Research Report

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

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