"FAILURE CRITERIA FOR DRAWING AND EXTRUSION OF TRIMETAL SUPERCONDUCTING COMPOSITE WIRE"

MANY FAILURE MODES ARE ENCOUNTERED IN THE FABRICATION OF THE NBTI SUPERCONDUCTING WIRE FOR THE SSC. ONE DISTINCT MODE OF FAILURE INITIATES WITH THE BREAKING OF INDIVIDUAL FILAMENTS AND PROPAGATES THROUGH THE MULTIFILAMENTARY REGION. THE CAUSE FOR THIS FAILURE CAN BE TRACED TO THE STRENGTH DIFFERENCES BETWEEN THE COMPONENTS OF THE COMPOSITE, THE GEOMETRY OF THE ASSEMBLY AND THE PROCESSING CONDITIONS. FOR LESS COMPLEX ASSEMBLIES, THAT CAN BE APPROXIMATED AS A BIMETAL COMPOSITE OF CORE AND SLEEVE, WE PRESENTLY HAVE AN ANALYSIS (SEE REFS. 2-7). THIS ANALYSIS PROVIDES RELIABLE CRITERIA FOR THE SELECTION OF THE PROCESSING PARAMETERS FOR THE PREVENTION OF FRACTURE IN BIMETAL WIRE. THIS ANALYSIS IS BASED ON TREATING A SPECIAL TOROIDAL VELOCITY FIELD. THE PRESENT PROJECT WILL BE ELEVATED TO DERIVE SIMILAR CRITERIA FOR THE PREVENTION OF FAILURE IN MORE COMPLEX SUPERCONDUCTOR STRUCTURES. THE DERIVATION WILL CONSIDER A COMPOSITE OF TRIPLE LAYERS. EACH LAYER WILL BE TREATED BY THE TOROIDAL, AS WELL AS BY THE SIMPLER, MORE SUITABLE, TRIANGULAR AND TRAPEZOIDAL FIELDS. THE GOAL OF PHASE I IS TO DETERMINE THE BEST REPRESENTATION FOR THE FLOW PATTERNS AND TO DERIVE AN EXPRESSION FOR THE POWER CONSUMPTION DURING PROCESSING. IN PHASE II THE EXPRESSION OF A CRITERIA FOR THE PREVENTION OF THIS FAILURE MODE WILL BE DERIVED AND PROGRAMMED FOR PRACTICAL USE. PHASE III WILL BRING THE SOFTWARE, AS A PRODUCT, TO THE USER, AS A FULLY DOCUMENTED AND SUPPORTED USER-FRIENDLY PACKAGE, ON A COMMERCIAL BASIS.