| Project/Area Number |
61460083
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| Research Category |
Grant-in-Aid for General Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Research Field |
機械材料工学
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| Research Institution | Kyoto University |
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Principal Investigator |
KOMAI Kenjiro Faculty of Engineering, Kyoto University, Professor, 工学部, 教授 (70025948)
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| Co-Investigator(Kenkyū-buntansha) |
MINOSHIMA Kohji Faculty of Engineering, Kyoto University, Instructor, 工学部, 助手 (50174107)
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| Project Period (FY) |
1986 – 1987
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| Project Status |
Completed (Fiscal Year 1987)
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| Budget Amount *help |
¥8,200,000 (Direct Cost: ¥8,200,000)
Fiscal Year 1987: ¥900,000 (Direct Cost: ¥900,000)
Fiscal Year 1986: ¥7,300,000 (Direct Cost: ¥7,300,000)
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| Keywords | Cyclic Stress Corrosion Cracking / Crack Initiation / Combined Stress / Combined Tension and Torsion / Corrosion pit / Stress Intensity Factor / High-strength Steel / 高強度鋼 / HE型SCC / 応力腐食割れ / 組合せ・多軸応力 / 曲げ / ねじり / 繰返し応力腐食割れ |
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| Research Abstract |
Cyclic stress corrosion cracking (SCC) tests of smooth specimens were conducted on 4135 high-strength steels in 3.5% NaCl solution. Loading types were bendin (R = -1), torsion (R = -1), and combined in-phase tensio( (R = 0) and torsion (R = 0). The ratio of <tau>_<max> to <sigma>_<max> ranged from zero (tension) to infinity (torsion). In torsion at <tau>_<max> <greater than or equal> 780 MPa, specimens were fractured by transgranular cracking normal to the longitudinal direction. At 500 MPa <equal or less than> <tau>_<max> < 780MPa, a longitudinal creack by shear stresses, which is considered to be caused by dissolution, was initiated at the bottom of corrosion pit, and then intergranular cyclic SCC crack dominated by maximum proincipal stress was started at the tip of it. In torsion at <tau>_<max> < 500 MPa and in bending and combined tension and torsion loading, however, cyclic SCC crack dominated by maximum principal stress or maximum tensile stress range was initiated at the bottom of corrosion pits. Mechanical condition dominating crack initiation at the bottom of corrosion pit was determined by stress intensity factor range <DELTA>_<IFSCC>, which was obtained by assuming the corrosion pit as a sharp crack. Similarly, a longitudinal crack by dissolution was initiated when a K_<III> value of a pit exceeded the K_<IIIFSCC>.
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