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

High-field superconducting magnets play a very important role in many large-scale physics experiments, particularly particle colliders and fusion confinement devices such as Large Hadron Collider (LHC) and International Thermonuclear Experimental Reactor (ITER). The two most common superconductors used in these applications are NbTi and Nb₃Sn. Nb₃Sn wires are favored because of their significantly higher J_c (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 develop detailed 2-D and 3-D finite-element models containing wire 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 stress and strain response of a Nb₃Sn wire under the Lorentz force. This paper improves our understanding of the effect voids have on the Nb₃Sn wire's mechanical properties, and in so, the connection between the distribution of voids and performance degradation such as the correlation between irreversible strain limit and the void-induced local stress concentrations.