JOPSS - Search Results

Journal Articles

Constraint effect on fracture mechanics evaluation for an under-clad crack in a reactor pressure vessel steel

Shimodaira, Masaki; Tobita, Toru; Takamizawa, Hisashi; Katsuyama, Jinya; Hanawa, Satoshi

Proceedings of ASME 2020 Pressure Vessels and Piping Conference (PVP 2020) (Internet), 7 Pages, 2020/08

https://doi.org/10.1115/PVP2020-21441

In JEAC 4206 which prescribes the methodology for assessing the structural integrity of reactor pressure vessels (RPVs), an under-clad crack (UCC) at the inner surface of RPV is postulated, and it is required that the fracture toughness of RPV steels is higher than stress intensity factor for at the crack tip during the pressurized thermal shock event. In the present study, to investigate the effect of cladding on the fracture toughness, we performed three-point bending fracture toughness tests and finite element analyses (FEAs) for an RPV steel containing an UCC or a surface crack, and the constraint effect for UCC was also discussed. As the result, we found that the fracture toughness for UCC was considerably higher than that for surface crack. On the other hand, the FEAs showed that the cladding decreased the constraint effect for UCC.

Journal Articles

Intergranular strains of plastically deformed austenitic stainless steel

Suzuki, Kenji*; Shobu, Takahisa

E-Journal of Advanced Maintenance (Internet), 10(4), p.9 - 17, 2019/02

In materials with an elastic anisotropy, a stress difference is generated between crystals when plastic deformation occurs, and it is known that this is deeply involved in material fracture. In this study, the residual stress for load direction in the plastically deformed material was investigated for each crystal orientation using the high-energy synchrotron radiation diffraction method. As a result, it was found that the residual stress is a tensile residual stress at an index with a high X-ray elastic constant (Young's modulus obtained for each diffraction surface) and a compressive residual stress at an index with a low X-ray elastic constant. We believe that this result will be useful for the technique of controlling the crystal orientation like the texture as improving the material strength.

Journal Articles

Post irradiation plastic properties of F82H derived from the instrumented tensile tests

Taguchi, Tomitsugu; Jitsukawa, Shiro; Sato, Michitaka*; Matsukawa, Shingo*; Wakai, Eiichi; Shiba, Kiyoyuki

Journal of Nuclear Materials, 335(3), p.457 - 461, 2004/12

https://doi.org/10.1016/j.jnucmat.2004.08.001

Times Cited Count：11 Percentile：58.46(Materials Science, Multidisciplinary)

F82H (Fe-8Cr-2W) and its variant doped with 2%Ni were irradiated up to 20 dpa at 300 $^{circ}$ C in the High Flux Isotope Reactor (HFIR) at Oak Ridge National Laboratory. Post irradiation tensile testing was performed at room temperature. During testing, the images of the specimens including the necked region were continuously recorded. Tests on cold worked material were also carried out for comparison. From the load-displacement curves and the strain distributions obtained from the images, flow stress levels and strain hardening behavior was evaluated. A preliminary constitutive equation for the plastic deformation of irradiated F82H is presented. The results suggest that the irradiation mainly causes defect-induced hardening while it did not strongly affect strain hardening at the same flow stress level for F82H irradiated at 300 $^{circ}$ C. The strain hardening of Ni doped specimens was, however, strongly affected by irradiation. Results provide basics to determine allowable stress levels at temperatures below 400 $^{circ}$ C.

Journal Articles

Elastic-plastic FEM analysis on low cycle fatigue behavior for alumina dispersion-strengthened copper/stainless steel joint

Nishi, Hiroshi

Journal of Nuclear Materials, 329-333(Part2), p.1567 - 1570, 2004/08

https://doi.org/10.1016/j.jnucmat.2004.04.169

Times Cited Count：9 Percentile：52.57(Materials Science, Multidisciplinary)

Elastic-plastic finite element analysis was performed for low cycle fatigue behavior of stainless steel/alumina-dispersion-strengthened copper (DS Cu) joint in order to investigate the fatigue life and the fracture behavior of the joint. As the results, a strain concentration was occurred near the interface of DS Cu for small strain range, however, in the DS Cu for large strain range. The fatigue life and fracture point were evaluated taking account for the strain concentration. The fatigue life and fracture point were consistent with those of the low cycle fatigue test.

Journal Articles

Effects of neutron irradiation on some superplastic characteristics of tetragonal zirconia polycrystals containing 3 mol% yttria

Shibata, Taiju; Ishihara, Masahiro; Motohashi, Yoshinobu*; Ito, Tsutomu*; Baba, Shinichi; Kikuchi, Makoto*

Materials Transactions, 45(8), p.2580 - 2583, 2004/08

https://doi.org/10.2320/matertrans.45.2580

Times Cited Count：3 Percentile：26.84(Materials Science, Multidisciplinary)

Fast neutrons (energy 1.610 $^{23}$ J) were irradiated to tetragonal zirconia polycrystals containing 3 mol% yttria (3Y-TZP) at the fluence levels of 2.510 $^{24}$ (Light irradiation) and 4.310 $^{24}$ (Heavy irradiation) m $^{-2}$ . The irradiation caused no significant swelling in the 3Y-TZP specimens. After the neutron irradiation, superplastic characteristics were examined by tensile tests at a temperature range from 1623 to 1773 K with initial strain rates ranging from 5.010 $^{-4}$ to 1.6710 $^{-2}$ s $^{-1}$ . It was found that the elongation to fracture of the irradiated specimens was quite small in comparison with the unirradiated ones. The apparent activation energy for the superplastic flow of the irradiated 3Y-TZP was fairly high, i.e., 781 and 693 kJ・mol $^{-1}$ for Light and Heavy irradiations, respectively. Atomic displacement damages and defects in the 3Y-TZP caused by the irradiation were thought to be main causes of these property changes.