Superconducting MgB2 Wire Drawing Considering Anisotropic Hardening Behavior and Hydrostatic Effect

Abstract

Numerical modeling was conducted to investigate the deformation behavior of powder mixture during multi-pass drawing processes for multi-filamentary MgB 2 wire. A modified Drucker-Prager Cap (DPC) model with an elliptical cap surface using the new material characterization method was developed to capture the anisotropic hardening behavior and hydrostatic effect of the powder mixture. A number of uniaxial die compaction, cold isostatic pressing, diametrical compression, and uniaxial compression tests were conducted using different powder densities to characterize the modified DPC model. A commercial finite element software ABAQUS with a user subroutine was used to simulate the drawing of the MgB 2 wire. The density and area fraction of the powder mixture during the wire-drawing process were verified with experimental results. The difference in packing density at the inner and outer filaments of the MgB 2 wire was successfully captured by simulation. In addition, the effect of the initial packing density on the superconducting properties of MgB 2 wire was numerically studied. It is shown that the increase in the superconducting area, which results from a high initial packing density, should be more effective compared to the increase in the grain connectivity in enhancing the critical current properties for the MgB 2 wire when the final packing density is saturated after a number of drawing processes.

Density dependent constitutive model for Bi-2212 powder compression deformation

“…In DPC model, the yielding criteria for Bi-2212 powders is determined by both deviatoric stress and hydrostatic stress in the continuous models and have been reported to describe many powders include BSCCO powders [36], MgB 2 [38], and other non-superconductor powders [39,40]. However, both shear failure and Cap surface in DPC model are evolving according to density change.…”