2018 Fiscal Year Final Research Report
Development of Fatigue Assessment Method for Welded Joints subject to Intermittently Hull Vibration Superimposed Wave Loadings
| Project/Area Number |
16H02432
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| Research Category |
Grant-in-Aid for Scientific Research (A)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Naval and maritime engineering
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| Research Institution | Osaka University |
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Principal Investigator |
OSAWA NAOKI 大阪大学, 工学研究科, 教授 (90252585)
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| Co-Investigator(Kenkyū-buntansha) |
飯島 一博 大阪大学, 工学研究科, 教授 (50302758)
堤 成一郎 大阪大学, 接合科学研究所, 准教授 (70344702)
田丸 人意 東京海洋大学, 学術研究院, 准教授 (00361808)
深澤 塔一 大阪府立大学, 工学(系)研究科(研究院), 教授 (80143171)
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| Research Collaborator |
Luis De Gracia
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| Project Period (FY) |
2016-04-01 – 2019-03-31
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| Keywords | 疲労 / 溶接継手 / 船体弾性振動 / 流力弾性解析 / 動電型疲労試験装置 / レインフロー法 / コンテナ船 |
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| Outline of Final Research Achievements |
From hydro-elasticity analysis results on slamming impact’s occurrence frequency and its peak stress range, the characteristics of whipping superimposed stress waveform experienced by a large container ship can be simplified as a) the slamming impact occurs once in every 4 to 5 Primary Wave (PW) cycles; b) the maximum stress range due to slamming impact can be comparable to the PW stress range; c) the waveform show approximately similar waveform regardless of significant wave height. The ‘reference whipping superimposed waveform’, which emulates the simplified waveform, has been proposed. The Electric Exciter (EE)-driven fatigue testing machine, which can apply this ‘reference waveform’ to welded joints at high speed, has been developed. It is found that the fatigue life of welded joints under constantly whipping superimposed loadings can be predicted by RainFlow Cycle Counting (RFCC) method, while RFCC led to conservative estimates for intermittently superimposed cases.
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| Free Research Field |
船舶海洋工学
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| Academic Significance and Societal Importance of the Research Achievements |
本研究により，今日一般的なウェザールーティングに従う大型コンテナ船が遭遇する弾性振動重畳応力波形の統計的性質が初めて明らかになった．さらに，この特性を再現できる標準ホイッピング重畳応力波形が定式化され，標準波形を高速・正確・低コストに溶接継手試験体に負荷できる動電型疲労試験装置も開発された．これにより，超大型コンテナ船の安全性評価で喫緊の課題となっている，船体弾性振動を考慮した疲労強度評価法を構築するための系統的疲労試験が初めて可能になった．本研究に引続いて，多様な応力波形での追加試験実施が望まれるが，その際は開発した動電型疲労試験装置の高速性・経済性が大いに役立つと期待される．
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