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Yamazaki, Yasuhiro*; Shinomiya, Keisuke*; Okumura, Tadaharu*; Suzuki, Kenji*; Shobu, Takahisa; Nakamura, Yuiga*
Quantum Beam Science (Internet), 7(2), p.14_1 - 14_12, 2023/05
Amemiya, Yutaro*; Nakada, Nobuo*; Morooka, Satoshi; Kosaka, Makoto*; Kato, Masaharu*
ISIJ International, 62(2), p.282 - 290, 2022/02
Times Cited Count：2 Percentile：32.54(Metallurgy & Metallurgical Engineering)Amemiya, Yutaro*; Nakada, Nobuo*; Morooka, Satoshi; Kosaka, Makoto*; Kato, Masaharu*
Tetsu To Hagane, 105(2), p.314 - 323, 2019/02
Times Cited Count：5 Percentile：29.02(Metallurgy & Metallurgical Engineering)For deeper understanding of a dynamic accommodation mechanism of internal stress in pearlite originated from the lattice misfit between ferrite and cementite phases, the lattice parameter ratios of cementite were locally analyzed in detail by using the electron backscatter diffraction (EBSD) technique. The EBSD analysis has revealed that lattice parameter ratios of cementite lamellae obviously differ from those of spheroidized cementite particles, which demonstrates that pearlite has a certain amount of internal stress as long as it maintains lamellar structure. The internal stress in pearlite gradually decreased during isothermal holding at 923 K after pearlitic transformation due to interfacial atomic diffusion of iron atoms. However, comparing with theoretical values under Pitsch-Petch orientation relationship, it was understood that large amount of internal stress had been already accommodated upon pearlitic transformation by introduction of misfit dislocations and structural ledges on ferrite/cementite lamellar interfaces. That is, the internal stress of pearlite is dynamically reduced by two different processes; built-in accommodation upon pearlitic transformation and additional time-dependent relaxation after pearlitic transformation. On the other hand, EBSD analysis and neutron diffraction technique gave remarkably different lattice parameters of cementite. From this result, it is concluded that various crystallographic orientation relationships between ferrite and cementite coexist in pearlite. Furthermore, elastic strain energy analysis suggests that the invariant-line criterion on ferrite/cementite interface plays an important role for the selection of orientation relationships in pearlite.
Shimizu, Kenichi*; Koike, Yuki*; Yamada, Taiki*; Oharada, Kazuya*; Tanaka, Keisuke*; Shobu, Takahisa
Zairyo, 65(9), p.657 - 664, 2016/09
The internal stress in crystalline thermoplastics, polyphenylene sulphide (PPS), reinforced by carbon fibers of 30 mass% was measured by the diffraction method using synchrotron with energy of 12.3 keV. The stress in the matrix was determined by the sin2psi method with side-inclination optics of transmitted X-ray diffractions. Using skin-layer strips cut parallel, perpendicular and 45 degree to the molding direction of the injection molded plates, the matrix stress was measured under the uniaxial applied stress. The experimental values were at least qualitatively agreed with the prediction derived based on micromechanics. The quantitative difference between experiment and prediction is mainly due to the neglect of the distribution of fiber orientations in the micromechanics prediction. These residual stresses were caused by the mismatch of the thermal expansion coefficient between matrix and fibers.
Tsukada, Takashi
Zairyo To Kankyo, 52(2), p.66 - 72, 2003/02
Irradiation assisted stress corrosion cracking (IASCC) is a potential failure mode suffered by the core-components of austenitic stainless steels in the aged light-water reactor (LWR), which is the intergranular type cracking caused by synergistic effects of neutron/gamma radiation and chemical environment. Effects of radiation on the materials and high-temperature water are discussed in this paper to understand IASCC phenomenon from a mechanistic viewpoint. It is essential to elucidate the radiation-induced microcompositional and microstructural changes in the alloy for mechanistic and predictive investigations of IASCC. Although grain boundary segregations of alloying and impurity elements are significant factors affecting IASCC, it has been considered that the radiation-induced microstructural and mechanical changes of materials play critical roles in IASCC. For mechanistic understanding of IASCC, further fundamental research works with experimental and theoretical approaches are needed. Efforts directed to the researches at the Japan Atomic Energy Research Institute are also described.
Kaji, Yoshiyuki; Kikuchi, Kenji; Penkalla, H. J.*
Proceedings of the 7th International Conference on Creep and Fatigue at Elevated Temperatures (CREEP7), p.179 - 183, 2001/06
A creep constitutive equation in Alloy800H was developed at 700, 800 and 850oC. In the equation, the inelastic strain rate is written in the form of a flow equation of the Norton-Bailey type and the hardening during deformation under various loads is induced by an internal stress which is subdivided into back stress and friction stress. The back stress represents a conservative part of the creep resistance while the friction stress includes all the dissipative parts in the internal structure such as grain boundary sliding, diffusion and interaction between dislocation and precipitation. Parameters were determined by the deformation properties for creep under constant stress conditions at each temperature. Deformation analyses show a good agreement between calculations and experimental results for creep tests at each temperature.
Tachibana, Yukio; E.Krempl*
Trans. ASME, Ser. H, 117, p.456 - 461, 1995/10
no abstracts in English
Morooka, Satoshi; Kawasaki, Takuro; Harjo, S.; Nakada, Nobuo*; Tsukada, Yuki*
no journal, ,
