| Project/Area Number |
61550052
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| Research Category |
Grant-in-Aid for General Scientific Research (C)
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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 | Kanazawa University |
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Principal Investigator |
HIROSE Yukio Professor Faculty of Education, Kanazawa University, 教育学部, 教授 (20019425)
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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 |
¥1,900,000 (Direct Cost: ¥1,900,000)
Fiscal Year 1987: ¥500,000 (Direct Cost: ¥500,000)
Fiscal Year 1986: ¥1,400,000 (Direct Cost: ¥1,400,000)
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| Keywords | An AC electrical potential system / Short crack / Notched specimen / Stress corrosion cracking / Fracture toughness / 破壊靭性値 / X線残留応力 / 有効応力拡大係数範囲 / 電位差法 / 限界亀裂長さ |
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| Research Abstract |
An AC electrical system with a lock-in amplifier was developed to measure the speciemen of crack in notched specimens of a high strength steel. This system was succesfully used to measure the crack length during SCC and fracture toughnesstests. Crack propagation tests were conducted both in air and in 3.5% NaCl solution. Resisual stress near the fracture surface were measured by X-Ray diffraction method. The results obtained are surmarized as follows;
(1) Although the growth rate of short cracks was higher than that predicted from the rate-<DELTA>K relation for long cracks, it was uniquely related to the effective stress intensity factor range and the relation was identical for long cracks.
(2) The residual stress measured on the fracture surface was tention both in air-fatigue and corrosion fatigue. The maximum depth of the plastic zone was evaluated on the basis of the residual stress distribution. The depth y is related to K _<max>by the following equation:alpha) ( K_<max>/<delta> y )^2
(omega) y = <alpha> (K_<max>/<delta> y) ^2
where <delta> y is the yield strength obtained in tension tests. <alpha> is 0.19 for air fatigue and 0.06 for corrosion fatigue. The small value of <alpha> in corrosion fatigue suggests the hardening of the material in the plastic zone due to the environmental effect.
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