This paper reports the results of experimental measurements and numerical studies of deformations and stresses arising in 2G REBCO CC (Second Generation Rare-Earth Barium Copper Oxide Coated Conductors) superconducting tapes, the use of which is proposed internationally for devices for electrical networks as Superconducting Fault Current Limiters (SFCLs) and superconducting cables. Such tapes are multilayer systems consisting of materials with different physical and mechanical properties. Brought to cryogenic temperatures in the test and use configurations, such tapes are subjected to thermomechanical stresses and deformations that, if they exceed certain limiting values, can cause irreversible degradation of both the electrical and mechanical performance of the tape such that it becomes unusable.
Experimental measurements were preliminarily carried out on AISI 301 stainless steel tapes and later on SuperPower and SuperOx superconducting tapes. On the AISI 301 tape, the optimal constraint conditions that minimize these stresses were determined; to date, such conditions are applicable only in the laboratory. On linear specimens of SuperPower tape, with conventional constraint, the stress is tensile and lower than the limit values mentioned above.

On SuperOx specimens featuring very complex architecture, the stresses could not be estimated due to their nonelastic behavior; nevertheless, the strains were measured. It is believed that the massive presence of the brazing alloy used to apply the additional steel foils may be largely responsible for this. However, the measured strains for both SuperPower and SuperOx are much lower than those considered to be the limit of irreversibility for commercial tapes. In addition to measurements on tape specimens placed on flat specimen holders, for both superconducting tapes measurements were also made by placing specimens on cylindrical holders, the latter of which were very laborious and difficult to interpret and need further investigation.
Numerical simulations of the thermoelastic behavior of AISI 301 steel tapes were performed using the commercial software COMSOL Multiphysics. Studies were developed to evaluate the most appropriate and realistic boundary conditions to be used in the simulations. The calculated stresses were found to be comparable with those determined from strain gage measurements – for now, only as an order of magnitude – but studies on boundary conditions, geometry, and physical model assumptions can be further expanded and deepened. Such development of the study, together with the incorporation of the actual structure of superconducting tapes into the geometry of the issue, will be the subject of the next year’s paper.
The studies conducted in the present Line of Activity have provided more information on the subject – which cannot be found to the authors’ knowledge in the scientific literature related to it.