| Project/Area Number |
07455056
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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 |
Materials/Mechanics of materials
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| Research Institution | KEIO University |
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Principal Investigator |
YAMADA Kunihiro KEIO Univ., Dep.of Mechanical Engineering, Professor, 理工学部, 教授 (40051742)
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| Project Period (FY) |
1995 – 1996
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| Project Status |
Completed (Fiscal Year 1996)
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| Budget Amount *help |
¥3,900,000 (Direct Cost: ¥3,900,000)
Fiscal Year 1996: ¥700,000 (Direct Cost: ¥700,000)
Fiscal Year 1995: ¥3,200,000 (Direct Cost: ¥3,200,000)
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| Keywords | High Strength Steel / Delayd Fracture / Intergranular Crack / Quasi-Cleavage Crack / Hydrogen Environment / AE Analysis |
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| Research Abstract |
To obtain the integrity of structures under aggressive environment i.e., to prevent a premature fracture is one of the critical issue of high strength steel under hydrogen or corrosive environment. We have been studying essential nature of fructure in delayd fracture employing an unnotched specimen as a substitute for a notched specimen. In the notched specimen the intergranular crack (IG) starts from the root of notch and then propagates rapidly as is known, but in unnotched specimens the quasi-cleavage crack (QC) can trigger the IG crack and the IG crack rapidly propagates to a final crack growth though a formation of IG crack is still a major mode of crack propagation in both smooth and notched specimens. The subsurface crack propagation along with the lapse of time was examined by Acoustic Emission (AE) investigation in this year and the results of AE analysis have been compared with those of fractographic analysis that was examined in the preceding year. As a result of the analysis, AE signal pattern could well estimate the change of the fracture mode. Then the mechanism of hydrogen induced fracture in high strength steel was evaluated more clearly from the combination of the AE and fractographic analyzes, consequently, the target materials which would have higher resistance for delayd fracture have to posses the resistance to transgranular craking propagation that is formed from a defect in metallugical structure such as non-metallugical inclusions, as well as the intergranular cracking.
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