Fatigue behavior and its influence on the critical current of externally reinforced Bi-2223 superconducting tape

The endurance evaluation of HTS conductors for practical applications is necessary. The mechanical properties and the critical current, I_c, of multifilamentary Bi-2223 superconducting tapes, externally reinforced with stainless steel foils, subjected to high cycle fatigue loading in the longitudinal direction were investigated at 77 K. The relations between the applied stress amplitude and the fatigue life (S-N curves) were obtained using the externally reinforced Bi-2223 tapes, and its transport property was evaluated with the increase of repeated cycles at different stress amplitudes. The effect of the stress ratio, R, on the I_c degradation behavior under fatigue loading was also examined considering the practical application situation of HTS tapes. Microstructure observation was performed in order to understand the I_c degradation mechanism in fatigued Bi-2223 tapes.