Stress-Strain Distribution Analysis in Bi2212 Subcable Based on Numerical Modeling and Experiment

There has been sustained interest in the development of the Bi2212/Ag round wire (RW) because of its unique potential for applications in high-field magnets (25 T or higher). The Bi2212 conductor is a round strand, which is a very favorable shape to produce multistage twisted cable-in-conduit conductors (CICCs) for the next fusion machine (DEMO). One drawback of Bi2212 is its fragile mechanical properties. The stress and strain accumulated during cabling, the thermal contraction during cooldown, and the electromagnetic load can have a severe impact on the transport properties of the Bi2212 RW. In order to investigate the strain distribution of Bi2212 in CICC, some research and development work was made at the Institute of Plasma Physics, Chinese Academy of Sciences (ASIPP). A simple cable wound with three Bi2212 RWs was manufactured and subjected to mechanical tests. A numerical model was proposed to analyze the stress-strain distribution of a wire inside a cable at cryogenic temperature. Comparisons were made between the model and experimental results. Based on the results and improved understanding of the mechanical behavior, an optimization could be implemented to reduce the Bi2212 cable degradation, in terms of conductor design, manufacture, and operation.