Papers by Keyword: n-Value

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Authors: D. Doko, N. Miyazaki, Shojiro Ochiai, Hiroshi Okuda, Sang Soo Oh, Masashi Tanaka, M. Hojo, Kozo Osamura
Abstract: Bending behavior of Bi2223/Ag superconducting composite tapes, and the influence of the bending damages on critical superconducting current Ic and n-value that is a measure for the sharpness of the transition from super- to normal conduction, were studied. Following damages, responsible to the reduction in critical current at high bending strains, were observed. (i) Transverse and (ii) longitudinal crackings of the filaments, (iii) interfacial debonding between filaments and silver, and (iv) buckling in compression side. The damage of the filaments arose first locally, resulting in a reduction of the Ic and n-value in the corresponding local portion. The overall Ic and n-values were determined by such a local portion. With increasing strain, the damage of the other portions arose successively, resulting in loss of superconductivity in all portions.
Authors: Masatoshi Sudo, Yoshiyuki Hattori, Takashi Endoh, Hiroomi Hiramitsu
Authors: Toshiya Suzuki, Kazuo Okamura, Yuya Ishimaru, Hiroshi Hamasaki, Fusahito Yoshida
Abstract: In this study, the effect of the material anisotropies of hot-rolled high-strength steel sheet on localized deformation behavior in hole expansion test has been investigated experimentally. First, the hole expansion test with the circular hole has been conducted to investigate the effect of anisotropies of material properties on the localized deformation behavior around the hole edge. Next, the hole expansion test with the oval hole has been conducted to investigate the effect of the major axis direction of the oval hole on the localized deformation behavior around the hole edge. As a result, it was clarified that the effect of anisotropies of r-value and n-value on the localized deformation behavior is strong, especially the anisotropy of n-value.
Authors: Jing Yuan Li, Jia Fei Wang, Dong Liang Zhang, Xin Kui Wang
Abstract: The microstructure, texture and basic stamping properties of AZ31 magnesium sheet are studied in this paper with optical microscopy (OM), scan electron microscopy (SEM), X-ray diffraction (XRD) and MTS universal tester. The results show that the basal texture (0002) is enhanced and the grain size decreases as the thickness of sheet decreases. However the texture depresses in the 0.52mm sheet due to the complete recrystallization under deep rolling reduction. The strength and elongation decreases and the strain hardening index (n value) increases as the thickness increases. The precipitation decreases and the basal texture depresses after annealing treatment. The peak value ratio of crystal plane (0002) of 1.3mm sheet reduces from 67% to 53% when annealing treated at 300°C for 2h. In addition, the strain hardening index (n) value reduces from 0.2535 to 0.2053 and the anisotropic index (r) value increases from 1.966 to 2.108 when the sheet is treated at the same condition.
Authors: M. Liang, Ping Xiang Zhang, X.D. Tang, J.S. Li, C.G. Li, K. Li, M. Yang, C.J. Xiao, Lian Zhou
Abstract: Nb3Sn superconductors are widely used in high magnetic field application. Internal tin processed Nb3Sn wires used for ITER coils (at 4.2K, 12T) were heated by two steps, local heat treatment and reaction heat treatments. The superconducting properties of Nb3Sn were investigated as a function of reaction heat treatment (HT) for strands during 625°C~665°C.To study the heat treatment effects on Jcn and n-value of Nb3Sn strands, different HT-parameters, i.e., annealing temperature and times, were applied on the Nb3Sn multifilament strands.
Authors: K. Watanabe, T. Inoue, S. Awaji
Abstract: We prepared Ag-sheathed Bi2Sr2CaCu2O8 (Bi2212) tapes heat-treated in high fields (in-field heat-treatment Bi2212) and heat-treated without magnetic fields (out-of-field heat-treatment Bi2212), in order to examine the magnetic field effect on the microstructure of Bi2212. The differential thermal analysis (DTA) was performed at 10 T using Bi2212 powders. The DTA suggests that the in-field heat-treatment changes the grain morphology of Bi2212. It was found that the critical current density Jc for the in-field heat-treatment Bi2212 tape is largely improved at 10 K in fields. In addition, the in-field heat-treatment Bi2212 tape has also a large n-value in the form of E=Ec(J/Jc)n, which is related to the microstructure change.
Authors: S. Ochiai, H. Okuda, Akihiro Toda, Shinji Nagano, M. Sugano, Kozo Osamua, Werner Prusseit
Abstract: Influences of cracking of the coated DyBa2Cu3Ȯ˽δ˰superconducting layer in composite superconductor under applied tensile strain on V(voltage)-I(current) curve, critical current and n-value were studied experimentally and analytically. The measured variations of V-I curve and critical current with increasing applied strain were described well by the modeling analysis. Also, the variations of shunting current with increasing imposed current and also with extension of cracks were revealed, from which the influences of shunting current on the variation of n-value with current were elucidated.
Authors: Shin Ichi Kinouchi, Hiroshi Sugimoto, Yoichiro Tarui, Kenichi Ohtsuka, Tetsuya Takami, Tatsuo Ozeki
Authors: Hidetoshi Somekawa, Masahide Kohzu, S. Tanabe, Kenji Higashi
Authors: K. Watanabe, T. Inoue, Satoshi Awaji, Gen Nishijima, Ken Ichiro Takahashi, V.R. Romanovskii
Abstract: The current-carrying properties beyond a critical current determined by a voltage criterion for Ag-sheathed Bi2Sr2CaCu2O8 (Ag/Bi2212) superconductors are examined at 10 K and 20 K in magnetic fields. We prepared the in-field heat-treated Ag/Bi2212 wires, in order to obtain the magnetic field alignment microstructure for Ag/Bi2212. The electric field and current density (E-J) properties were evaluated for Ag/Bi2212 wires with and without the in-field heat-treatment. We found that the E-J properties for the in-field heat-treated Ag/Bi2212 wires differ from those for the out-of-field heat-treated ones, and are analogous to the E-J dependence for Bi-system high temperature superconductors with the sintered-like grain morphology.
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