Analysis of flat rolling of superconducting silver/ceramic composites

The flat rolling process from wire to tape is presumably the most crucial link in the chain of mechanical processes leading from loose powder and silver tubes to the final superconducting Ag/BSCCO tape. In order to improve the critical current density of the superconducting filaments, one must process these to the highest possible density without at the same time introducing failures as large cracks and macroscopic shear bands. In order to analyse and optimise the process, the interaction between the involved materials and their very different mechanical properties must be taken into account. The silver is considered an incompressible von Mises material, hardening as a function of equivalent strain. The powder on the other hand is a compressible friction material implying pressure dependent “flow stress”. In this paper particular attention is paid to stresses and strains and defects in the deformation zone. The evolution of density in the powder cores is analysed by the finite element method.