Multishot Analysis of a 65-T Pulsed Magnet Considering Different Failure Modes ofCu-Nb Conductor

Abstract

Recently, a 65-T pulsed magnet encountered fatigue failure after 2124 shots in total at the Wuhan National High Magnetic Field Center. Multishot simulation is thus carried out by ANSYS according to the working history of the magnet. A constitutive model is applied considering different failure modes of a Cu-Nb conductor so that the mechanical performance and the fatigue life of the magnet can be examined and predicted. It is found that there is a permanent increase in the hoop strain of the conductors, which raises the stress of the reinforcement while reduces that of the conductors. The magnet failure is caused by large axial pressure with the fault origin located at the inner boundary of the sixth layer of the conductors. The 583 shots above 60 T have largely promoted the strain increase in the conductor and induced a rapid reduction in the mechanical performance of the magnet. By comparison, the failure mechanism is different below 60 T, which enables the magnet to operate under more reliable conditions. These results indicate that the practical field of a future pulsed magnet had better not exceed 92% of the maximum value as long as the same conductor is used.