Influence of Shear Stress on Current Carrying Capabilities of High Temperature Superconductor Tapes

To achieve high currents single HTSC tapes or Roeble strands must be combined into a cable. Many concepts like Rutherford cable, coated cable in conduit or full size cable model of Roebel strands require twisting of the HTSC tapes. Twisting or torsion exerts longitudinal and shear stress on the tapes which degrade the current carrying capabilities. Finite element analysis was done to explain this behavior. However, the influence of longitudinal stress in HTSC tapes on critical current is well documented, but there is no experimental data for pure shear stress available. To verify the finite element analysis shear stress experiments are of significant interest. With a three point bending method shear stress can be applied to a single HTSC tape. Critical current measurements with varying shear stress are conducted for several HTSC tapes. With the experimental results and the longitudinal stress dependence a correlation between torsion experiments and finite element analysis is possible.