Finite Element Simulation of Volume Forming of High-Temperature Superconducting MgB2 Wire: Construction Through Constitutive Models of Metals and Powders

Abstract:

Tensile mechanical tests at room temperature with varying strain rates (0.001, 0.01, and 0.07 s^-1) were conducted on Cu tubes (as-processed state), Nb tubes (soft state), and Mg rods (extruded state) used for internal magnesium diffusion (IMD)-MgB₂ single-core wires. Uniaxial unidirectional mechanical tests and cyclic compression mechanical tests at room temperature were performed on B powder to obtain the stress-strain curves. Based on the abovementioned analysis results, Johnson-Cook constitutive models for three metals at room temperature were established, as well as the function between the elastic modulus of B powder and its relative density. Furthermore, the bulk deformation of IMD-MgB₂ single-core wires during room-temperature rolling was simulated using the DEFORM finite element software, and the deformation behavior and stress distribution of materials were analyzed. Results demonstrate that the Johnson-Cook models established for three metals and the elastic modulus-relative density function of B powder accurately describe the flow behavior of Cu, Nb, and Mg in IMD-MgB₂ wires, as well as the elastic deformation of B powder. DEFORM finite element simulation results can also effectively reflect the deformation behavior of IMD-MgB₂ single-core wires. The overall deformation during the rolling process is uniform with a homogeneous stress distribution; however, the surface still has defects. This study provides a theoretical basis for optimizing the plastic forming process of IMD-MgB₂ superconducting wires.