Bending strain effects on the critical current in Cu-stabilized IBAD/EDDC processed SmBCO coated conductor tape

The intrinsic strain effect on critical current, I c in Cu-stabilized GdBCO coated conductor (CC) tapes under bending and uniaxial tension has been investigated. The bending deformation tolerance of I c in GdBCO CC tapes, fabricated by reactive co-evaporation by deposition and reaction (RCE-DR) with substrate materials of Hastelloy and stainless steel and fabricated by the metal organic chemical vapour deposition (MOCVD) process was evaluated. The intrinsic strain response of I c under bending was found to be independent of the fabrication process, the substrate material and the geometry of the sample. For samples with a Hastelloy substrate, the intrinsic strain response of I c /I cmax under bending was well correlated with those under uniaxial tension. However, for samples with a stainless steel substrate, these had a large strain sensitivity for I c under uniaxial tension even though this showed a much higher irreversible strain limit up to 1.05%.

Section: Introductionmentioning

confidence: 99%

Intrinsic strain effect on critical current in Cu-stabilized GdBCO coated conductor tapes with different substrates

Shin¹,

Dedicatoria²

2013

“…One of these is bending stress during the winding of a coil. Therefore, the bending tolerance of YBCO coated conductor has been evaluated as one of the most fundamental mechanical properties by many groups [1][2][3][4][5][6][7][8][9] as well as the uniaxial strain dependence [10,11].…”

Section: Introductionmentioning

confidence: 99%

Bending strain analysis considering a shift of the neutral axis for YBCO coated conductors with and without a Cu stabilizing layer

Sugano

Machiya

Sato

et al. 2011

Bending tolerance is one of the most fundamental mechanical properties of YBCO coated conductors for application to a superconducting coil. In order to reveal the origin of the difference in critical current (Ic) with bending radius among various conductors, it is essential to estimate the bending strain at a superconducting layer. In this study, the bending strain was evaluated both experimentally and analytically for YBCO coated conductors with and without a Cu stabilizing layer. The internal tensile and bending strain of YBCO film in a composite conductor was directly evaluated from the shift of the Bragg peaks of a YBCO film using synchrotron radiation. We also present an analytical method to calculate the neutral axis position by considering its shift due to the progress of plastic deformation of the components such as Cu, Ag and Hastelloy. The validity of our strain analysis was confirmed by agreement of the measured and calculated internal bending strains. The calculation result shows that yielding of the Cu stabilizing layer has a strong influence on the position of the neutral axis and results in a weaker dependence of Ic. A comparison with tensile strain measurements shows that the effect of bending can be predicted from the tensile strain dependence.

“…As shown in figure 9(a), the CC tape exhibited no significant degradation under tension up to 100 cycles at 20 mm and 15 mm bending diameter. In the case of the thick single-side stabilized EDDC-SmBCO CC tape in our previous study [32], the thick 50 μm Cu stabilizer buckled and apparently delaminated when compressive bending was applied which resulted in significant irreversible I c degradation. Compared to the EDDC-SmBCO CC tapes, which showed an irreversible limit at 0.26%, the current thin-profile CC tape with thin surround Cu stabilizer showed robust I c behavior under monotonic and cyclic bending deformation both under tensile and compressive bending strain.…”

Section: Cyclic Bending Deformationmentioning

confidence: 84%

Evaluation of the electromechanical properties in GdBCO coated conductor tapes under low cyclic loading and bending

Shin¹,

Gorospe²,

Bautista³

et al. 2015

The effects of low cyclic loading on the critical current, Ic, under uniaxial and transverse loadings, and bending deformations in GdBCO coated conductor (CC) tapes were evaluated. Under monotonic continuous bending deformation, CC tapes exhibit a high tolerance of Ic up to the lowest bending diameter of 12 mm using the Goldacker bending test rig. However, when the CC tape was subjected to alternate tension–compression bending, a lower irreversible bending strain limit was measured. This was also observed when cyclic bending was applied to the CC tapes which showed a significant decrease in Ic just after 10 cycles of alternate tension–compression bending at 20 mm bending diameter. Such different Ic degradation behavior under different bending deformation procedures gave insight into the proper handling of CC tapes from manufacturing, coiling and up to operating conditions. In the case of uniaxial tension, when electromechanical properties of CC tape were evaluated by repeated loading based on a critical stress level obtained under monotonic loading, Ic also did not show significant change in its degradation behavior up to the irreversible stress limit. The GdBCO CC tape adopted can allow cyclic loading up to 100 cycles without significant irreversible degradation below the monotonic irreversible limit. In the case of the transverse cyclic test, with regard to the large scattering of data especially in the tensile direction, a different cyclic loading procedure was established. For 10 repeated loadings, the mechanical and electromechanical properties of the GdBCO CC tapes showed similar values within the reversible range under the monotonic loading. Ic degraded abruptly indicating that no delamination occurred at the REBCO film during the subcritical cyclic loading. Different fracture morphologies were observed under cyclic loading depicting branch-like patterns of the remaining REBCO layer on the substrate of the CC tape.