Elastoplastic contact behavior of multi-stage superconducting cables under tension

Abstract

The superconductor cable with multi-stage twisted strands is a key component in the International Thermonuclear Experimental Reactor. These superconducting strands are composite materials with a complex microstructure. In the study, an elastoplastic constitutive model incorporating both isotropic and kinematic hardening is established to investigate the mechanical properties of the strands. The model is implemented as a user-defined material subroutine (UMAT) in the commercial finite element code ABAQUS using the fully implicit backward Euler method. Based on the analysis of the elastoplastic properties of the strands, a numerical contact model is developed to predict the contact characteristics of the multi-stage superconducting cable. The influence of helical pitch on the contact characteristics is examined by integrating the elastoplastic constitutive relations of the strands with their hierarchical helical structures. Numerical results demonstrate that the proposed model accurately describes the contact characteristics of the multi-stage superconducting cable. It is noteworthy that the elastoplastic contact force is found to be smaller than the elastic contact force. This elastoplastic contact model can be effectively used to predict the degradation of critical current in the multi-stage superconducting cable due to tensile loads.