Evaluation of delamination characteristics in GdBCO CC tapes under transverse load using anvil test methods for various anvil contact configurations at 77 K

Abstract

The performance characteristics of second-generation rare-earth barium copper oxide-coated conductor (CC) tapes are influenced by stress and strain induced during fabrication, cool-down, and operation. Electromechanical characteristics have been improved using several methods such as adding a stabilizer and external lamination. In multilayered structures such as CC tapes, structural delamination or ballooning phenomenon can occur in the interlayers. In particular, when CC tapes are applied to magnets or coils under a high field magnet, delamination is a critical damage. Therefore, it is important to examine the failure behaviors of CC tapes under transverse tension load and to evaluate the delamination characteristics. In this study, anvil test methods were used to mechanically and electromechanically investigate the delamination characteristics of CC tapes processed by reactive co-evaporation by deposition and reaction under transverse tension load at 77 K and a self-field. To check the effectiveness of the anvil test method in evaluating the delamination strength of the CC tapes, various upper anvil/specimen contact configurations were used. As results, damage at the edges of CC tape samples were found to significantly influence both mechanical and electromechanical delamination strength including Ic degradation behaviors. Finally, the fractographic morphologies of CC tape samples delaminated under transverse tension loads were microscopically observed, and these observations were used to explain variations in electromechanical delamination strength depending on the upper anvil/specimen contact configuration.

Numerical analysis of the mechanical and electrical properties of (RE)BCO tapes with multiple edge cracks

“…The irreversible degradation of the critical current of the tape occurs when the strain in the (RE)BCO exceeds the irreversible strain limit ε irr [20,[51][52][53][54][55][56]. The results of previous studies [13,14,20,[57][58][59][60][61][62][63] indicate that micro-crack initiation and propagation is one of the primary causes of critical current degradation. In this section, we evaluate the effects of the crack on the critical current degradation based on the critical tensile strain criterion.…”

National round robin test (RRT) for delamination strength testing YBCO HTS wires at room temperature (RT) and 77K

“…In these works, effects of the cutting edges of the CCs was found to reduce the measured values of MDS [17][18][19]. Anvil configurations [20,21], loading speeds [22] and thickness of the silver layer [23] on the MDS measurement had little influence. Since the CC delamination is intimately related to the fracture and damage of ceramic, the threeparameter Weibull distribution based on the weakest link model often provide a proper statistics analysis [24,25].…”

Evaluation of the effect of edge cracks on critical current degradation in REBCO tapes under tensile stress

“…Slitting the wide REBCO tape to the width required by the application can greatly reduce the cost of conductor manufacturing. However, edge cracks were observed because of the REBCO tapes slitting process by many groups [9][10][11][12][13][14][15][16][17][18][19]. Edge cracks due to the slitting process may cause the premature degradation when subjected to the tensile loading.…”