Finite Element Analysis of Torsion Experiments on HTSC Tapes

During the past years the application of 2G HTSC material is growing. However, to achieve high currents single HTSC tapes must assembled in a Roebel-cable geometry. Going to even larger cable concepts like Rutherford cables, twisting of HTSC tapes is required. To examine the influence of twisting or torsion on critical current of Coated Conductor tapes or Roebel strands, systematic experiments were carried out giving results for critical twisting lengths. The results have to be examined considering the different strain states within the tape under torsion. On one hand longitudinal strain plays a role, but on the other hand shear strain has to be addressed also. To understand these results theoretical assessment of the stress strain situation within the tape under torsion was performed. Together with finite element analysis the effect of longitudinal and shear strain was systematically examined to give an understanding of the critical current behavior under torsion.