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

Shojiro Ochiai, Yuichiro Oki, Fumiaki Sekino, Hiroaki Ohno, Masaki Hojo, Hidezumi Moriai, Shuji Sakai, Masanobu Koganeya, Kazuhiko Hayashi, Yuichi Yamada, Naoki Ayai, Kazuo Watanabe

Research output: Contribution to journalArticlepeer-review

2 Citations (Scopus)

Abstract

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 Nb3Al 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 Nb3Al 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 Nb3Al 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 σc,r, while in the Nb3Al composite Ic decreases later than σc,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.

Original languageEnglish
Pages (from-to)396-404
Number of pages9
JournalSuperconductor Science and Technology
Volume13
Issue number4
DOIs
Publication statusPublished - 2000 Apr 1

ASJC Scopus subject areas

  • Ceramics and Composites
  • Condensed Matter Physics
  • Metals and Alloys
  • Electrical and Electronic Engineering
  • Materials Chemistry

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