低温工学
Online ISSN : 1880-0408
Print ISSN : 0389-2441
ISSN-L : 0389-2441
化合物超電導線のストレス効果
田中 靖三橋本 康男
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1978 年 13 巻 3 号 p. 130-141

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A review of the stress effects in superconducting compound wires is summarized in the following.
(1) A stress level of 0.7-2×108Pa and a strain level of 0.1-0.2% represents a threshold of significant critical current degradation.
(2) The peak effects in critical current and critical temperature of superconducting composite wires appear to be associated with the intrinsic strain (compression) of 0.2-0.3%.
(3) The decrease in critical current is almost recoverable up to strains of about 1% upon load removal. But the first 20% decrease in critical current is reversible only at strains within about 0.5%.
(4) In the reversible strain region and the strain amplitude within about 0.15%, no additional degradation in critical current happens owing to fatigue. In the irreversible region, however, a damage due to fatigue occurs, and most of the additional Ic degradation occurs in the first 10 cycles.
(5) At high strains where the degradation is irreversible, the effect is well accounted for by cracks of over 100mm observed in the compound layer. At the reversible region, the effect may be probably explained either by a change in the intrinsic critical temperature and field, or by an alternation of the vortex-pinning structure.
(6) The effect of stress on the type A-15 superconducting compound is considered similar to that on the other compounds of type B-1 or C-15 etc.
(7) In design conditions at high loads, operating currents of magnet should be determined using a stress-dependent set of Ic-H characteristics rather than the usual zero-stress Ic-H characteristics.

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