Search in the site by keyword

reports - Deliverable

Theoretical and Experimental Analysis of Mechanical Stresses Induced by Thermoelastic Phenomena in Superconducting Tapes for Electrical Grid Devices

reports - Deliverable

Theoretical and Experimental Analysis of Mechanical Stresses Induced by Thermoelastic Phenomena in Superconducting Tapes for Electrical Grid Devices

Superconducting materials, for their “zero resistance” operation, need to be cooled to cryogenic temperatures, which are typically achieved by immersion in cryogenic fluids within cryostats or through conduction via cryocoolers. Superconducting tapes can be used in devices for electrical networks, where they are assembled in complex configurations alongside many other materials with support, electrical insulation, reinforcement, and electrical connection functions. In these conditions, the superconducting tape is subjected to stresses and resulting thermoelastic deformations, which must be correctly anticipated and evaluated. If these stresses exceed predefined limits, they cause a significant and irreversible reduction in the tape’s critical current. These stresses and deformations must be assessed both theoretically, using numerical models, and experimentally. This report presents the results of the development of preliminary analytical modeling and the application of experimental methods based on strain gauge techniques.

High-Temperature Superconducting Tapes of second generation (2G SAT), based on barium, copper, and rare-earth oxides—commonly known as 2G ReBCO CC (Second Generation Rare-earth Barium Copper Oxide Coated Conductors)—have long been proposed for prototypes of Superconducting Fault Current Limiters (SFCL) for electrical networks. These tapes are multilayer systems composed of materials with different physical and mechanical properties. Once brought to the cryogenic temperatures required for their use, thermo-mechanical stresses and strains occur within the tapes. These stresses and strains are responsible for the degradation phenomena of the tapes, particularly delamination, which leads to the deterioration of their electrical performance. The theoretical calculation and experimental measurement of these stresses and strains in the field of applied superconductivity need further investigation compared to what is currently available in the literature. This study aims to determine these stresses and strains through theoretical models and preliminary experimental measurements using resistance strain gauges. The work is an organic approach to the study of the aforementioned issues. The goals achieved include validating: a) the models introduced and applied for determining thermo-mechanical stresses and strains on elementary geometries, and b) the strain gauge technique for their experimental measurement. The theoretical data obtained are, for now, qualitative and highlight the expected discontinuity of stress between the different materials present in superconducting tapes, as well as which materials are more subject to thermo-mechanical stresses. The model does not yet consider the presence of physical interfaces between the various layers. The experimental data obtained through strain gauge measurements are currently indicative. The correct experimental methodology needs to be identified to obtain more accurate and precise results. At a first approximation, the data provided by the numerical models developed are nonetheless comparable to those from strain gauge measurements. In the future, both approaches will be further developed to gain a better understanding of the thermo-mechanical phenomena occurring in superconducting tapes under operational conditions at cryogenic temperatures, and for a more precise determination of these stresses and strains.

Projects

Comments