| Project/Area Number |
16360440
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| Research Category |
Grant-in-Aid for Scientific Research (B)
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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 | KYUSHU UNIVERCITY |
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Principal Investigator |
TOYOSADA Masahiro Kyushu University, Faculty of Engineering, Professor, 工学研究院, 教授 (30188817)
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| Co-Investigator(Kenkyū-buntansha) |
YOSHIKAWA Takao Kyushu University, Faculty of Engineering, Professor, 工学研究院, 教授 (50380572)
GOTOH Koji Kyushu University, Faculty of Engineering, Associate Professor, 工学研究院, 助教授 (60274487)
TSUTSUMI Seiichiro Kyushu University, Faculty of Engineering, Research Associate, 工学研究院, 助手 (70344702)
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| Project Period (FY) |
2004 – 2006
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| Project Status |
Completed (Fiscal Year 2006)
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| Budget Amount *help |
¥14,900,000 (Direct Cost: ¥14,900,000)
Fiscal Year 2006: ¥3,000,000 (Direct Cost: ¥3,000,000)
Fiscal Year 2005: ¥6,300,000 (Direct Cost: ¥6,300,000)
Fiscal Year 2004: ¥5,600,000 (Direct Cost: ¥5,600,000)
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| Keywords | Fatigue / Surface crack / Change of aspect ratio of a surface crak / Hull structural elements / Material softening / 下負荷面モデル / ビーチマーク / 応力比 / 大型溶接構造物 / 材料軟化 |
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| Research Abstract |
In order to evaluate the surface fatigue crack growth in stress concentration regions, authors defined the representative surface crack that enables to consider the existence of multiple surface cracks in the regions. Evolution rules of a representative surface crack and single surface crack under complex stress concentration regions investigated. Besides, the effect of material softening phenomena for fatigue crack initiation is also investigated. General aspects of the result of this project are listed below.
(1)Numerical data to give a representative surface crack are obtained by finite element analysis and the survey of literatures.
(2)It is confirmed by the measurements in fatigue test that evolution history of a representative surface crack is not affected by stress ratio.
(3)The shape of test piece in order to investigate the evolution history of fatigue surface crack under bi-axial stress gradient fields is fixed by the questionnaires about fatigue damages in hull structures, and the specimens are fabricated.
(4)Fatigue tests are performed by applying test pieces mentioned above.
(5)By referring above mentioned fatigue tests and developed theories in this research, evolution rules of a representative surface crack is updated. Simple and useful formula to estimate the aspect ratio of a representative surface crack is introduced.
(6)Elastic-Plastic finite element analyses with subsurface model as a constitutive equation of material are performed in order to investigate the effect of material softening phenomena for fatigue crack initiation. As a result of above mentioned analyses and experiments, it is confirmed plastic strain enables to accumulate if applied stress is lower than yield stress and upper than proportional ratio.
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