Fatigue Tests of HTS Coils

This paper presents and discusses experimental results for mechanical performance of HTS coils with epoxy impregnation. Though mechanical characteristics of Ag-sheathed Bi2223 tape conductors have been investigated by various research organizations, there are few reports on those for HTS coils. Experiments on static hoop stress as well as experiments on repetitive hoop stress were performed. The critical static hoop stress obtained at 4.2 K was found to be 1.4 /spl sim/ 1.6 times higher than the critical tensile stress of the conductor. The coil did not deteriorate after 10/sup 4/ times loading of 70% of the critical hoop stress.