||The manufacture of superconductor, in the last years, has obtained a great successful and it has turned in a technology with hopeful future. The fabrication process is composed with a big quantity of operations. First the ceramic loose powder in the 2212 phase is filled into a latex tube and cold isostatically compressed to form a bar which is packed in a silver tube. Then the silver tube and the powder are reduced by drawing operations getting a single-filament. After that, the single-filaments are packed in a new silver tube forming a multi-filament which is subsequently again by drawing. The multi-filament wire is flat rolled to form a thin tape of approximately 0,2 mm thick by 3 mm wide. After the mechanical deformation the tapes are heat-treated at approximately 835aC and pressed. The heat treatment converts the powder by phase transformation from BSCCO-2212 to BSCCO-2223 and grain growth into superconducting.
This work has been carried out in collaboration with the industrial company Nordic Superconductors Technologies A/S. The aim of the project is to characterize the plastic properties of BSCCO powder taking into account the effect that the rolling process produce in the powder, in order to obtain the yield surface for three relative densities: 65, 75 and 85%. For that, four different tests: Diametric Compression Test, Uniaxial Compression Test, Die Compaction Test and Powder in Flexible Die Test have been used to find different yield points as a function of the hydrostatic pressure. With the first two tests, two points in the failure line are found, and with the other two tests points with different pressure and strain are found. All together describe the powder in the pressure range where the rolling process works.
The results obtained have provided a much better description of yield surface in the rolling zone. And a mathematical model that is capable to represent the yield surface has been found.