Reliability evaluation procedure of electromechanical properties in GdBCO CC tapes obtained by uniaxial tension and fatigue tests at 77 K

In the design of 2G superconducting magnets and coils, both the yield strength and the irreversible stress limit for critical current ( I c ) degradation of coated conductor (CC) tapes under various environmental conditions have been investigated. Equally important and yet often discounted are the reliability tests to evaluate the I c degradation induced by the fatigue loading expected during operation. Because I c degradation at the stress level below the reversible stress limit of the CC tapes is possible (e.g., under a static fatigue load), in this study, the procedures for evaluating the reliability of 2G CC tapes using characteristic limit values obtained through a series of electromechanical properties evaluations are introduced. I c behaviors were obtained at 77 K through specified loading against the elapsed time in a static fatigue test, while electromechanical fatigue limits of CC tapes were determined at a stress ratio (R) of 0.1 in a high-cycle fatigue test. The determination of electromechanical properties through uniaxial tensile and fatigue tests was established, and its long-term reliability was examined.