Structural analysis of pulsed magnets considering interface characteristics.

Abstract

The aim of traditional designs of pulsed magnets is to keep the von-Mises stress on the midplane less than the ultimate tensile strength of materials. However, recently failed high-field experiments showed that some short circuits occurred at the magnet end, which is most possibly caused by the axial displacement of wires. This indicates that the former design is inadequate and accurate axial mechanical analysis of magnets is necessary. In this paper, a finite element model of pulsed magnets considering interface characteristics is proposed. Both the contact status and interfacial friction between the conductor layers and reinforcements can be accounted for Simulations are conducted with a failed 95 T dual-coil prototype, which was originally designed with the self-developed Pulsed Magnet Design Software (PMDS) software. The simulation results show that all the originally expected separations calculated by the PMDS software disappear due to the compression. This makes the calculated maximal von-Mises stress of the inner four reinforcement layers about 600 MPa less than the former designs. The influence of the interfacial friction is also presented. Besides, the simulations show that the maximum axial displacement at the magnet end is up to 8 mm at the designed peak field, which is deadly to the insulations. Hence, we suggest that the axial displacement at the magnet end should also be one design objective of pulsed magnets. At last, the factors affecting the axial displacement are analyzed.