Numerical Investigation on the Thermo-Mechanical Behavior of HTS Tapes and Experimental Testing on Their Critical Current

This work extends to second generation Rare-Earth Barium-Copper-Oxide ((Re)BCO) tapes an experimental procedure previously developed to analyze the impact of double bending at room temperature on the performance of Bismuth-Strontium-Calcium-Copper-Oxide (BSCCO) tapes. The modified procedure is applied to measure the critical current of a commercial (Re)BCO tape subjected to bending around a cylindrical mandrel first on one side, then on the other side, followed by the cooldown to cryogenic temperature. In the bending phase, mandrels of decreasing diameter are used to identify the minimum curvature leading to a significant reduction of the tape critical current. Furthermore, a novel finite element model is developed to complement the experimental results. The model simulates the double bending at room temperature, the following straightening of the sample, and its cooldown to cryogenic conditions. The coupled thermo-mechanical numerical model together with the temperature-dependent mechanical properties allow investigating the combination of thermal contraction effects and bending loads in the whole domain of the problem. The experimental and numerical results obtained help to give a better insight in the distribution of the strain and stress components inside the (Re)BCO tape and to evaluate their impact on the conductor electrical performance in relevant operating conditions.