2001 Fiscal Year Final Research Report Summary
A study of low cycle fatigue properties of low activation materials for fusion reactors
| Project/Area Number |
11480117
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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 |
Nuclear fusion studies
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| Research Institution | Natiomal Institute for Fusion Science |
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Principal Investigator |
MUROGA Takeo Natiomal Institute for Fusion Science Fusion Engineering Research Center, Professor, 炉工学研究センター, 教授 (60174322)
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| Co-Investigator(Kenkyū-buntansha) |
NAGASAKA Takuya Natiomal Institute for Fusion Science Fusion Engineering Research Center,Associate, 炉工学研究センター, 助手 (40311203)
NISHIMURA Arata Natiomal Institute for Fusion Science Department of Large Helical Device Project,Professor, 大型ヘリカル研究部, 教授 (60156099)
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| Project Period (FY) |
1999 – 2001
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| Keywords | low activation materials / ferritic steels / vanadium alloys / low cycle fatigue / mechanical properties |
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| Research Abstract |
To investigate fatigue property of a low activation ferritic steel (9Cr-2W steel, JLF-1), low cycle fatigue tests were performed in air at room temperature under an axial strain control of a complete push-pull condition. The strain rate was 0.4 %/s. Cyclic strain-hardening was observed within initial 20 cycles, and then cyclic strainsoftening occurred gradually until the final failure, though the plastic strain range did not change remarkably. Tensile peak stresses in hysteresis curves measured at around a half of number of cycles to failure depended on the total strain range, and the decrease of the peak stress by the cyclic strain-softening in the smaller total strain range was larger than that in the larger strain range. The regression curve of the total strain range against the fatigue life was formulated using Manson-Coffin's equation and the fatigue life ofJLF-1 steel was compared with that of 8Cr2W steel. It was shown that JLF-1 has a superior fatigue properties to those of a 8C
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r-2W steel (F82H). A high purity vanadium alloy, V-4Cr-4Ti, NIFS-HEAT-2, was produced using electron beam melting and vacuum arc re-melting process. The impurity was tried to reduce as little as possible and a 26 mm thick plate was fabricated successfully. The normal size specimens were machined out of the plate to investigate the mechanical properties. Tensile tests and fracture toughness tests were conducted in air and in vacuum (about 10〜4 Pa) environment at room temperature. The alloy showed high ductility and elongated over 80 %, and clear dimple fracture occurred in both environments. A ductile crack growth was not observed during the fracture toughness tests. The crack resistance curve went up straightly, and it was almost same as the blunting line of which slope was 2 x σflow The blunting continued over several hundreds of J value in MJ/m2. It means that the material is very tough and the valid J cannot be obtained at room temperature. The present results contributed to enhancing understanding on fatigue and fracture properties of the low activation candidate materials and on the size effects in the fatigue and the fracture toughness evaluation experiments. Less
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