The Critical Current Degradation of Bi-2223 Superconducting Tapes Due to Fatigue Cycles at Different Strain Range

The critical current (IC) of high temperature superconductors is an important parameter for practical application, such as magnets, cables and transformers. The degradation of ICunder the tensile strain is measured at 77 K as well as under the compressive strain. It is found that the properties of Bi-2223 tapes are superior in the compressive strain to that in the tensile strain. The fatigue degradation behaviors of Bi-2223 tapes are studied in the symmetrical strain cycles and the unidirectional strain cycles. Both of the tests are conducted at 77 K. It is observed that the ICafter thousands of cycles in the unidirectional strain cycles is much higher than that of the symmetrical strain cycles. Finally, a round bending test is employed to determine the degradation of ICwhen Bi-2223 tapes are wound around a mandrel. A critical radius of about 50 mm is found in the experiment.