Finite Element Analysis of Transverse Compressive and
Thermal Loads on Nb3Sn Wires with Voids

Authors:   Y. Zhai, L. d Hauthuille, C. Barth and C. Senatore 


Abstract:  High field superconducting magnets play an important role in many large-scale physics experiments, particularly particle colliders and fusion confinement devices such as LHC and ITER. The two most common superconductors used in these applications are NbTi and Nb3Sn. Nb3Sn wires are favored because of their significantly higher Jc (critical current density) for higher field applications. The main disadvantage of Nb3Sn is that the superconducting performance of the wire is highly strain-sensitive and it is very brittle. This strain-sensitivity is strongly influenced by two factors: plasticity and cracked filaments. Cracks are induced by large stress concentrators that can be traced to the presence of voids in the wire. We study the correlation between irreversible strain limit and the void-induced local stress concentrations. We develop an accurate 2D and 3D finite element model containing filaments and different possible distributions of voids in a bronze-route Nb3Sn wire. We apply compressive transverse loads for various cases of void distributions to simulate the natural stress and strain response of a Nb3Sn wire under the Lorentz force. This study improves our understanding of the effect voids have on the wire's mechanical properties, and in so, the connection between the distribution of voids and performance degradation.
_________________________________________________________________________________________________

Presented at: 24th International Conference on Magnet Technology, COEX, Seoul, Korea, October 2015

Published in: IEEE Transactions on Applied Superconductivity
_________________________________________________________________________________________________

Download PPPL-5207 (pdf 2.3 MB 8pp)
_________________________________________________________________________________________________