Strain-Induced failure prediction in HTS Roebel strands and cables: a finite element study based on critical strain criterion

The mechanical reliability of high-temperature superconducting (HTS) Roebel cables is critical for cryogenic power applications. This study presents a finite element framework to predict the onset of mechanical failure in the ReBCO superconducting layer, using a validated 0.45 % critical strain threshold. Simulations are performed at 77 K to evaluate the influence of axial and torsional loads on strain localization in both individual strands and full cable assemblies. The model identifies regions where external stress leads to microcrack initiation and irreversible critical current (I_c) degradation. A parametric study on strand number and transposition length reveals important design insights for improving the structural performance of HTS cables in superconducting machines and cryogenic magnet systems. The adopted methodology reliably predicts the onset of microcrack initiation and I_c degradation, providing a consistent criterion for assessing mechanical limits in HTS structures.