| Project/Area Number |
16360229
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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 |
Structural engineering/Earthquake engineering/Maintenance management engineering
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| Research Institution | Nagoya University |
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Principal Investigator |
TATEISHI Kazuo Nagoya University, EcoTopia Science Institute, Professor, エコトピア科学研究所, 教授 (80227107)
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| Co-Investigator(Kenkyū-buntansha) |
YAMADA Kentaro Nagoya University, Graduate School of Environmental Studies, Professor, 大学院・環境学研究科, 教授 (50109310)
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| Project Period (FY) |
2004 – 2005
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| Project Status |
Completed (Fiscal Year 2005)
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| Budget Amount *help |
¥12,200,000 (Direct Cost: ¥12,200,000)
Fiscal Year 2005: ¥2,600,000 (Direct Cost: ¥2,600,000)
Fiscal Year 2004: ¥9,600,000 (Direct Cost: ¥9,600,000)
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| Keywords | Low cycle fatigue strength / Image technique / Welded joints / Heat affected zone / Damage mechanics / Local strain / TIG dressing / 低サイクル疲労 / 溶接継手 / 鋼製橋脚 / 熱影響部 / 変動ひずみ |
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| Research Abstract |
A new low cycle fatigue testing system has been developed, in which strains of the specimen are measured by image technique. The low cycle fatigue tests of steel plain material and welded portion under constant and variable strain amplitude, particularly the fatigue life less than ten cycles, was conducted by using the newly developed testing system. The test results indicated that the fatigue life of welded portion, such as deposit metal and heat affected zone (HAZ), was much shorter than that of plain material. Particularly, HAZ was the weakest spot, of which fatigue life was about 30% of the plain material. And fatigue strength curves for the plain material, the deposited metal and the HAZ were proposed, individually.
As an estimation method of low cycle fatigue strength of "welded joint", peak strain based fatigue assessment method was verified. T-shape welded joints were employed for the verification test. The specimen was analyzed by elasto-plastic finite element method in order to quantify the local strain field around welded portion and the peak strain at the cracked point. On the other hand, fatigue life of the specimen was experimentally obtained by low cycle fatigue tests. The relationship between the peak strain and the fatigue life was consistent with the fatigue strength curve for the deposited metal. Consequently, it was demonstrated that the fatigue assessment method by peak strain approach was available even in low cycle fatigue region. And the improvement of fatigue strength of welded joints by TIG dressing was investigated. T-shape welded joint specimens of which weld toes were finished by TIG dressing were tested. The fatigue test results were compared with that of as-welded specimens tested in the same conditions. The test results indicated that TIG dressing could substantially increase the low cycle fatigue strength of welded joints.
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