Interface crack growth rate and fatigue life of multilayer-coated conductor tapes

Abstract

Rare-earth barium copper oxide (REBCO) coated conductor (CC) tapes in high-field magnet applications usually experience fatigue due to a variety of cyclic mechanical and thermal loads. Therefore, estimation of the fatigue life of a particular REBCO CC is vital for the successful development and applications of high-field magnets devices, which are crucial components for aerospace, automotive, and maglev train transportation. For these needs, the authors evaluated the interfaces fatigue crack growth rate, and fatigue life of multilayered yttrium barium copper oxide (YBCO) coated conductor (CC) tape at room temperature via a displacement-energy model (DEM) approach. The DEM approach can measure the damage initiation and propagation rate in specific interfaces of a multi-layer film structure simultaneously. It assumed transverse intrinsic tensile/compressive cyclic loading and adopted the linear-elastic damage law with the maximum normal stress failure criterion to characterize the degradation in the tape. With an initial Eigenfunction (W0) (a parameter equivalent to the stress loading amplitude range) set as 2.30 × 10-12 m, the computed results show a strain (ε) range from 0.35 to 0.46 % and fatigue ratio range from 0.002 to 0.07 in the interfaces of the tape. Under the given parameters, it was found out that the tape has a critical interface fatigue crack growth rate of 2.54 pm/cycle corresponding to fatigue life of 3.9372 × 105 cycles. According to our previous studies, the results on the DEM approach has good agreement with those on the Finite Element Method (FEM) counterpart model, closed-form solution (CFS) model, and X-ray diffraction method (XRD). This technique can help to avoid enormous resources usually spent experimentally on the calculation of fatigue life of REBCO CC tapes.