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Development of a method for significantly improving the fatigue life of welded joints by the laser processing

Research Project

Project/Area Number 20H02372
Research Category

Grant-in-Aid for Scientific Research (B)

Allocation TypeSingle-year Grants
Section一般
Review Section Basic Section 24020:Marine engineering-related
Research InstitutionKyushu University

Principal Investigator

Gotoh Koji  九州大学, 工学研究院, 教授 (60274487)

Project Period (FY) 2020-04-01 – 2023-03-31
Project Status Completed (Fiscal Year 2022)
Budget Amount *help
¥17,940,000 (Direct Cost: ¥13,800,000、Indirect Cost: ¥4,140,000)
Fiscal Year 2022: ¥3,380,000 (Direct Cost: ¥2,600,000、Indirect Cost: ¥780,000)
Fiscal Year 2021: ¥4,810,000 (Direct Cost: ¥3,700,000、Indirect Cost: ¥1,110,000)
Fiscal Year 2020: ¥9,750,000 (Direct Cost: ¥7,500,000、Indirect Cost: ¥2,250,000)
Keywords疲労 / 特殊加工 / 溶接 / 構造・材料 / 維持管理工学
Outline of Research at the Start

本研究の目的は「建造コスト増加を極力抑えつつ,メンテナンスフリーでも大幅に優れた耐疲労特性を有する溶接構造物建造手法の構築」である.従来の疲労性能改善手法では,長期供用後の処理部の経年変化の影響が十分に考慮されていない.本研究では建造直後の疲労性能改善を「溶接止端部へ炭素含有塗料塗布後にレーザ照射を行い,溶接止端半径の緩和と局部的高強度化」「レーザ・アークハイブリッド溶接の溶接変形低減効果による誘起二次応力の低減」により担保し,経年変化対策として「腐食代より深い部分の結晶粒微細化を建造段階で付与」することで,建造直後から長期供用後までの疲労強度改善効果を,建造段階で一括導入する手法を構築する.

Outline of Final Research Achievements

Topics (1) to (3) that could be introduced during the construction stage to improve the fatigue performance of large welded structures such as ships, offshore structures, bridges and steel structures of high-rise buildings were studied.
(1) Suppression of crack propagation by localised laser irradiation to refine the base metal grains; (2) Suppression of fatigue crack initiation by hardening the crack initiation surface area by carburization; and (3) Expansion of the range of application (welding position) of laser-arc hybrid welding that can achieve secondary stress suppression due to weld deformation.

Academic Significance and Societal Importance of the Research Achievements

溶接構造物の高サイクル疲労強度への主な影響因子は亀裂発生領域近傍の応力集中であるが,溶接により構造体を製作する以上これを回避することは難しい.本研究は建造本来の道具として導入する大出力レーザを,溶接止端部近傍の硬化や結晶粒微細化という疲労寿命改善効果が期待される複数の対策に活用することを考えた結果,応力集中場の生成が避けられなくとも大幅な寿命改善を達成した点が学術的かつ社会的に高い意義を有している.また,本研究で基礎知見を得た手法を用いれば,社会インフラである大型溶接構造体の寿命を大きく改善できるため,これに要する費用の削減が可能となる.

Report

(4 results)
  • 2022 Annual Research Report   Final Research Report ( PDF )
  • 2021 Annual Research Report
  • 2020 Annual Research Report
  • Research Products

    (6 results)

All 2022 2021

All Journal Article (3 results) (of which Peer Reviewed: 1 results) Presentation (3 results) (of which Int'l Joint Research: 1 results)

  • [Journal Article] 溶接継手の疲労強度改善のためのレーザ照射による局部浸炭処理に関する基礎検討2022

    • Author(s)
      田門 岳大,後藤 浩二,森園 靖浩
    • Journal Title

      日本船舶海洋工学会講演会論文集

      Volume: 34 Pages: 467-472

    • Related Report
      2022 Annual Research Report
  • [Journal Article] 疲労強度改善のためのレーザ照射による結晶粒微細化に関する基礎検討2022

    • Author(s)
      寺辻 和陸,内村 友哉,松田 和貴,後藤 浩二
    • Journal Title

      溶接学会九州支部講演論文集

      Volume: 19 Pages: 37-40

    • Related Report
      2022 Annual Research Report
  • [Journal Article] A Study on Practical Fabrication Method in Tee Type Full Penetrated Welded Joint under Long Distance Welding Fabricated by the Laser-Arc Hybrid Welding2021

    • Author(s)
      Uemura Takamori、Uchimura Tomoya、Gotoh Koji
    • Journal Title

      Journal of the Japan Society of Naval Architects and Ocean Engineers

      Volume: 34 Issue: 0 Pages: 197-207

    • DOI

      10.2534/jjasnaoe.34.197

    • NAID

      130008164962

    • ISSN
      1880-3717, 1881-1760
    • Related Report
      2021 Annual Research Report
    • Peer Reviewed
  • [Presentation] 溶接継手の疲労強度改善のためのレーザ照射による局部浸炭処理に関する基礎検討2022

    • Author(s)
      田門 岳大,後藤 浩二,森園 靖浩
    • Organizer
      日本船舶海洋工学会 令和4年春季講演会
    • Related Report
      2022 Annual Research Report
  • [Presentation] 疲労強度改善のためのレーザ照射による結晶粒微細化に関する基礎検討2022

    • Author(s)
      寺辻 和陸,内村 友哉,松田 和貴,後藤 浩二
    • Organizer
      溶接学会九州支部研究発表会
    • Related Report
      2022 Annual Research Report
  • [Presentation] A Study on Working Conditions for Improving Fatigue Strength of Welded Joints by Localized Carburizing Treatment Using Laser Irradiation2021

    • Author(s)
      Takehiro Tamon and Koji Gotoh
    • Organizer
      34th Asian-Pacific Technical Exchange and Advisory Meeting on Marine Structures (TEAM 2020/21)
    • Related Report
      2021 Annual Research Report
    • Int'l Joint Research

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Published: 2020-04-28   Modified: 2024-01-30  

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