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1988 Fiscal Year Final Research Report Summary

Study on the safety design of welded structure with respect to unstable fracture

Research Project

Project/Area Number 61302050
Research Category

Grant-in-Aid for Co-operative Research (A)

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

Principal Investigator

MACHIDA Susumu  Univ. of Tokyo, Fac. of Eng. Professor, 工学部, 教授 (70010692)

Co-Investigator(Kenkyū-buntansha) KANEDA Sigehiro  Univ. of Tokyo, Fac. of Eng. Assistant, 工学部, 助手 (90010892)
NIIMURA Yutaka  Univ. of Tokyo, Fac. of Eng. Assistant, 工学部, 助手 (40010889)
TERAMOTO Tokuro  Univ. of Tukuba, Institute of Eng. Mech. Assistant Professor, 構造工学系, 講師 (00134213)
YOSINARI Hitoshi  Univ. of Tokyo, Fac. of Eng. Assistant Professor, 工学部, 助教授 (20167737)
ITAGAKI Hiroshi  Yokohama National Univ., Fac. of Eng. Professor, 工学部, 教授 (10017882)
Project Period (FY) 1986 – 1988
KeywordsUnstable ductile fracture / CTOA / Fracture toughness / Fracture probability / Fatigue strength / Fatigue crack propagation / Crack opening stress / Strain rate / き裂開口応力 / 歪速度 / 液体ヘリウム温度
Research Abstract

The final purpose of this study is to establish the design philosophy of welded structures to prevent unstable fructure. The following basic experimental studies are carried out.
1) Unstable dectile fracture based on CTOA R-curve in investigated. The experimental results show that CTOA-based instability criterion can predict instability point favorably.
2) Statistical investigation on the significance of defects in offshore structures is carried out. Fracture probability for a specific structural member is calculated and the influence of the variations in the parameter ( e.g. datectability of defect, fatigue crack growth rate, scatter of the toughness etc.) is also examined. It is found that the most significant parameter is the retectability of defect.
3) Fatigue Strength of the weldment of offshore structure is experimentally analyzed using T-joint type bending specimens. The effect of thickness can be described using elastic stress concentration factor at weld teo.
4) Fatigue crack propagation tests under wide band random loading are carried out and the relationship between fatigue behaviors under randam loading and constant amplitude loading is discussed. The significance of crack closure for understanding crack growth under variable amplitude loading is emphasized and an estimating method for fatigue crack behavior under randam loading is proposed.
5) The effect of strain rate on fracture toughness of sttuctural stainless steel is experimentally investigated. The material tested is 20 mm thick SUS304 steel and the tests are carried out at liguid Helium temperature (4K). It is found that the effect of strain rate is significant and the effect of martensitic transformation is also important.

  • Research Products

    (10 results)

All Other

All Publications (10 results)

  • [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
  • [Publications] Machida,Susumu: Int.Conf.Fract.and Fract.Mech.,Shanghai.

    • Description
      「研究成果報告書概要(和文)」より
  • [Publications] Itagaki,Hiroshi: Advanced Experimental Mechanics (ICAEM),(1988).

    • Description
      「研究成果報告書概要(和文)」より
  • [Publications] Itagaki,Hiroshi: INALCO'88 Organizing Committee,Tokyo,(1988).

    • Description
      「研究成果報告書概要(和文)」より
  • [Publications] Teramoto,Tokuro: Proc.of 31st Jpn.Cong.on Mat.Res., Soc.of Mat.Sci.Jpn.,(1988).

    • Description
      「研究成果報告書概要(和文)」より
  • [Publications] Machida Susumu.: "Fatigue Crack Propagation under Service Loading (The 3rd Report) - Estimating 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
  • [Publications] Machida Susumu.: "A ststistical Investigation of the Significant of Defects in Offshore Structures" Int. Conf. Fract. and Frack. Mech., Shanghai (1987).

    • Description
      「研究成果報告書概要(欧文)」より
  • [Publications] Itagaki, Hiroshi.: "Effect of the Length of Smulated Random Process on Fatigue Crack Growth" Advanced Experimental Mechanics (ICAEM), (1988).

    • Description
      「研究成果報告書概要(欧文)」より
  • [Publications] Itagaki, Hiroshi.: "STATISTICAL BEHAVIOR OF CRACK GROWTH IN AN ALMINUM ALLOY" INALCO'88 Organizing Committee, Tokyo, (1988).

    • Description
      「研究成果報告書概要(欧文)」より
  • [Publications] Teramoto, Tokuro.: "Fracture Toughness for SUS304 and Weld Joint at LHe Temperature" Proc. of 3lst Jpn. Cong. on Mat. Res., Soc. of Mat. Sci. Jpn., (1988).

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

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Published: 1990-03-20  

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