Impact of fatigue loading on the critical current of Bi-2223 tapes under background magnetic field

In practical applications, such as superconducting magnetic energy storage (SMES) magnets or alternate current applications of superconducting power cables, high temperature superconducting (HTS) tapes are subject to cyclical loads caused by repeated thermal cycles and periodic electromagnetic forces. These repeated loads will affect electromechanical properties of the tapes. Previous electromechanical properties studies have provided useful information on the performance of multifilament Bi-2223 tapes under different forms of fatigue loading. The impact of axial tensile fatigue loading on the critical current (Ic) under external magnetic field, however, has not been reported. In this work, we studied the variation of Ic of the Bi-2223 tapes with the background magnetic field after different cycles of fatigue at 77 K. It was found that the effect of stress amplitude on the degradation of Ic for Bi-2223 tapes was more significant than the maximum stress. When the maximum fatigue stress approached the irreversible stress limit, the copper alloy reinforced Bi-2223 tapes still had good current-carrying properties after 105 fatigue loadings. Ic became less sensitive to the external magnetic field with the increase of the number of fatigue cycle.