2007 Fiscal Year Final Research Report Summary
Establishing Strength Evaluation Method of Very Thin Ductile Cast Iron and the Way of Improving Reliability of Thin Wall Castings.
| Project/Area Number |
18560708
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Metal making engineering
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| Research Institution | Hokkaido University |
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Principal Investigator |
NOGUCHI Toru Hokkaido University, Professor Emeritus (80001220)
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| Co-Investigator(Kenkyū-buntansha) |
NAKAMURA Takashi Hokkaido University, Grad. school of Eng., Professor (30237408)
HORIKAWA Noritaka Hokkaido University, Grad. School of Eng., Assistant Prof. (80344480)
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| Project Period (FY) |
2006 – 2007
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| Keywords | Casting / Ductile cast iron / Thin wall / Strength evaluation / Tensile strength / Elongation / Toughness / Nondestructive evaluation |
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| Research Abstract |
The purpose of this research is to establish the way of strength evaluation of very thin (less than 2 mm) ductile cast iron by small test pieces and to find the way to improve reliability of thin wall castings. Tensile properties, toughness, fatigue properties and nondestructive evaluation were discussed.
1) Tensile test: A small test piece 4.5 mm wide and 2 mm thick with 12 mm gauge length was proposed, with which, tensile strength and elongation equivalent to the ones from a 14 mm diameter standard test piece are obtained. Elongation should be determined from the load-elongation curve measured.
2) Toughness test: Small punch test (SP test) by 10×10×0.5 (mm) test piece was applied. Crack initiation deflection δ^* is determined by the measured load deflection curve, and equivalent fracture strain ε_<qf> is estimated, from which, fracture toughness J_<Ic> is determined. J_<Ic> can be also estimated from HRB hardness.
3) Fatigue test: It was concluded that fatigue tests with stress ratio, R= -1.0, by thin plate test pieces should be carried. Special jigs for the test were developed. Fatigue crack initiation from the cast surface and the process of primary and steady crack propagation will be observed. Casting method to get sound thin plate specimens with ordinary melt treatment was also developed.
4) Nondestructive evaluation: Eddy current test was applied to estimate the hardness and the microstructure. Improving the measurement accuracy and new standards different from the thick specimens may enable the estimation.
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