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Ochiai, Shojiro; Sawada, T.; Nishino, Sayaka; Sekino, Hideo; Hojo, Masaki; Yamada, Yuichi; Hayashi, Kazuhiko; Ayai, N.; Koganeya, M.; Ono, Masayoshi

doi:10.1023/a:1006618619566

Cited by 9 publications

(13 citation statements)

References 5 publications

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“…It is needed to understand the stress-induced damage evolution and its influence on superconductivity towards the fusion uses. The tensile fracture strain of the Bi2223 filaments has been reported to be around 0.1% [2][3][4], being several to ten times lower than that of other superconducting filaments such as Nb 3 Sn (0.5-1.2%) [5,6] and Nb 3 Al (0.6-1.0%) for fusion uses [7]. Thus, under the applied strain, the critical current of Bi2223 composite is reduced severely [1][2][3][8][9][10][11][12][13][14][15][16].…”

Section: Introductionmentioning

confidence: 96%

Damage evolution under bending and tensile stress and its influence on critical current of Bi2223/Ag superconducting composite tape

Ochiai

Miyazaki

Doko

et al. 2004

Journal of Nuclear Materials

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Section: Introductionmentioning

confidence: 96%

Damage evolution under bending and tensile stress and its influence on critical current of Bi2223/Ag superconducting composite tape

Ochiai

Miyazaki

Doko

et al. 2004

Journal of Nuclear Materials

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“…When a Bi2223 composite superconductor is applied to a magnet, it is subjected to mechanical and electromagnetic stresses [1]. The Bi2223 filament is, however, very brittle; the fracture strain in short samples is around 0.1% [2][3][4][5], which is far lower than that of other superconducting filaments such as Nb 3 Sn (0.5-1.2%) [6][7][8], Nb 3 Al (0.6-1.0%) [9] and Nb-Ti (2%) [10]. Thus, the critical current of the Bi2223 composite tends to be reduced more than that of Nb 3 Sn, Nb 3 Al and Nb-Ti composites when stress is applied.…”

Section: Introductionmentioning

confidence: 99%

“…The scatter increases with decreasing m. For instance, the values m = 3, 5 and 10 correspond to the coefficient of variation (= standard deviation/average) 0.36, 0.23 and 0.12, respectively. The m values estimated in our previous work for Bi2223, Nb 3 Sn and Nb 3 Al were 4.7 [18], 7-12 (depending on heat-treatment temperature and time) [7,8] and 6-7 [9,19,20], respectively. This means that the strengths of the filaments are different from each other and also the strength of a given filament is different from position to position.…”

Section: Introductionmentioning

confidence: 99%

Tensile damage and its influence on the critical current of Bi2223/Ag superconducting composite tape

Ochiai

Nagai

Okuda

et al. 2003

Supercond. Sci. Technol.

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We have studied the tensile behaviour of Bi2223 superconducting composite tapes at room temperature, and the influence of the tensile damages introduced at room temperature on the critical current Ic and the n values at 77 K. In the measurement of the Ic and n values, the overall composite with a gauge length 60 mm was divided into six elements with a gauge length of 10 mm in order to find the correlation of the Ic and n values of the overall composite to those of the local elements which constitute the composite. From the measured stress–strain curve of the composite and the calculated residual strain of the Bi2223 filaments, the intrinsic fracture strain of Bi2223 filaments was estimated to be 0.09–0.12%. When the applied strain was lower than the onset strain of the filament damage, the original Ic and n values were retained both in the overall composite and the elements. In this situation, while the overall voltage at the transition from superconductivity to normal conductivity of the composite was the sum of the voltages of the constituent elements, among all elements the overall voltage was affected more by the element with the lower Ic (higher voltage). The damage of the filaments arose first locally, resulting in a reduction of the Ic and n values in the corresponding local element, even though the other elements retained the original Ic and n values. In this situation, the voltage of the overall composite stemmed dominantly from that of the firstly damaged weakest element, and the overall Ic and n values were almost determined by the values of such an element. After the local element was fully damaged, the damage arose also in other elements, resulting in segmentation of the filaments. Thus, the Ic and n values were reduced in all elements. The correlation of Ic between the overall composite and the elements could be described comprehensively for non-damaged and damaged states from the voltage–current relation.

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“…The experimental data of Nb 3 Al composite, fabricated by the jelly-roll method at Sumitomo Electric Industries, with an overall diameter of 0.8 mm and copper ratio 1.55, containing 241 filaments with an average diameter of 34 µm are referred from [9][10][11][12] for comparison. In this Nb 3 Al composite, the filament was composed mainly of Nb 3 Al compound, with a minor amount of niobium and copper in the central part.…”

Section: Methodsmentioning

confidence: 99%

“…Recently the present authors [9][10][11] have studied the damage accumulation process during fatigue at room temperature and its influence on critical current at 4.2 K and residual strength at room temperature of an Nb 3 Al composite wire. In the present work, the fatigue behaviour, critical current and residual strength of Ti-Nb composite wire were studied in a similar manner, and the results were compared with the results for Nb 3 Al one to reveal the differences and similarities between them.…”

Section: Introductionmentioning

confidence: 99%

Differences and similarities in fatigue behaviour and its influences on critical current and residual strength between Ti-Nb and Nb₃Al superconducting composite wires

Ochiai¹,

Oki²,

Sekino³

et al. 2000

Supercond. Sci. Technol.

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The influences of fatigue damage introduced at room temperature on critical current at 4.2 K and residual strength at room temperature of Ti-Nb superconducting composite wire with a low copper ratio (1.04) were studied. The experimental results were compared with those of Nb3 Al composite. The following differences between the composites were found: the fracture surface of the Ti-Nb filaments in the composite varies from a ductile pattern under static loading to a brittle one under cyclic loading, while the Nb3 Al compound always shows a brittle pattern under both loadings; the fracture strength of the Ti-Nb composite is given by the net stress criterion but that of Nb3 Al by the stress intensity factor criterion; in the Ti-Nb composite the critical current Ic decreases with increasing number of stress cycles simultaneously with the residual strength c ,r , while in the Nb3 Al composite Ic decreases later than c ,r . On the other hand, both composites have the following similarities: the filaments are fractured due to the propagation of the fatigue crack nucleated in the copper; with increasing number of stress cycles, the damage progresses in the order of stage I (formation of cracks in the clad copper), stage II (stable propagation of the fatigue crack into the inner core) and stage III (overall fracture), among which stage II occurs in the late stage beyond 85 to 90% of the fatigue life; at intermediate maximum stress, many large cracks grow into the core portion at different cross sections but not at high and low maximum stresses; accordingly, the critical current and residual strength of the portion apart from the main crack are low for the intermediate maximum stress but not for low and high maximum stresses.

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Cited by 9 publications

References 5 publications

Damage evolution under bending and tensile stress and its influence on critical current of Bi2223/Ag superconducting composite tape

Damage evolution under bending and tensile stress and its influence on critical current of Bi2223/Ag superconducting composite tape

Tensile damage and its influence on the critical current of Bi2223/Ag superconducting composite tape

Differences and similarities in fatigue behaviour and its influences on critical current and residual strength between Ti-Nb and Nb₃Al superconducting composite wires

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Untitled

Cited by 9 publications

References 5 publications

Damage evolution under bending and tensile stress and its influence on critical current of Bi2223/Ag superconducting composite tape

Damage evolution under bending and tensile stress and its influence on critical current of Bi2223/Ag superconducting composite tape

Tensile damage and its influence on the critical current of Bi2223/Ag superconducting composite tape

Differences and similarities in fatigue behaviour and its influences on critical current and residual strength between Ti-Nb and Nb3Al superconducting composite wires

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Product

Resources

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Differences and similarities in fatigue behaviour and its influences on critical current and residual strength between Ti-Nb and Nb₃Al superconducting composite wires