Stresses and strains in multi-filament HTS tapes

High temperature superconducting tapes are now commercially available for practical applications such as magnets and cables. However, still today the published data on strength and allowable deformation limits of these tapes are not altogether in agreement. Definitions and concepts with regards to the stresses and strains in HTS tapes under deformation are discussed in this paper and criterions for use by the industry are presented. When handling HTS tapes it is necessary to know the limiting values of loading, bending and twisting to avoid damage. Damage is commonly defined as degradation of the current carrying capabilities. Most serious is crack formation in the BSCCO material, this will take place when stress concentrations exceed a certain value. Values from 0.2% to 0.5% total tensile strain in the ceramic core is quoted as the deformation limit for HTS tapes where cracks are appearing. The stress/strain situation in a HTS tape with BSCCO cores in a metallic matrix is discussed and experimental results are presented. Damaging strains are found and compared with results from literature. Curves of the limiting values for bending, tension and torsion are shown as well as the influence of these deformations on I/sub c/ values.