Optimisation of the Explosive Compaction Process for Powder-In- Tube MgB2 Superconductors Using Numerical Simulations

Abstract

High quality, ex-situ powder-in-tube (PIT) MgB2 superconductors are fabricated using the explosive compaction technique. During the treatment, the precursor materials are densified under high strain-rates using PETN as the explosive medium. It has been found that the product quality depends on the porosity of the compact, which affects the critical current density of the superconductor by introducing changes in the interparticle bonding of the material, as well as the peak shockwave pressure which has an effect on the maximum tensile stress imposed to the specimen. This determines the crack formation in the consolidated powder and the uniformity of the product’s final shape. The explosive compaction process has been modeled using the LS-DYNA explicit finite element code where the compacted MgB2 powder is treated as a porous soil-like material with a customised yield surface. The results of the numerical simulation include the compact porosity, the pressure, the temperature and strain rate profiles as well as the dimensions of the final product, which are used as input data in order to assess the efficiency of the explosive compaction process. The process is non-parametrically optimised for the above mentioned quality factors, and the optimal dimensions of the explosive charge and container tube are determined.