Effects of room-temperature tensile fatigue on critical current andn-value of IBAD–MOCVD YBa₂Cu₃O_7−x/Hastelloy coated conductor

Abstract

Vapor Deposition (IBAD-MOCVD) REBCO conductors on Hastelloy substrates is reported for axial tensile strains up to 0.5% and up to 100,000 cycles. Failure mechanisms are investigated via microstructural studies. Results show that REBCO conductors retain electrical performance for 10,000 cycles at ε=0.35% and ε=0.45% strain, and ε=0.5% for 100 cycles. The main cause of fatigue degradation in REBCO conductors is crack propagation that initiates at the slitting defects that result from the manufacturing process.

Stress, strain and electromechanical analyses of (RE)Ba2Cu3Oxconductors using three-dimensional/two-dimensional mixed-dimensional modeling: fabrication, cooling and tensile behavior

“…In practical applications, internal mechanical loads occur among the constituent layers inside a REBCO conductor during and after the conductor and coil fabrication processes and under Lorentz forces during magnet operation. Experimental results and theoretical analyses showed that the critical current (I c ) of a REBCO conductor was influenced by intrinsic strains induced by external forces or deformations [8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25]. The strain effect on I c can be divided into two regions: reversible and irreversible degradation regions.…”

“…For example, experimental data showed that I c of a typical REBCO conductor started to decline rapidly at around 0.7% tensile strain and the normalized I c degraded 50% at a tensile strain of about 0.8% [8]. Scanning electron microscopy (SEM) showed that transverse crack arrays were generated in yielded samples [18] and edge and 'shattered' cracks were detected in the REBCO layers when severe I c reduction occurred [19]. Furthermore, micro-cracks in the REBCO layer were detected through magneto-optical (MO) images for applied strains larger than e irr [17].…”

Research on damage characteristics and microscopic appearance of ReBCO tapes after DC overcurrent

“…However, some scholars have conducted studies on the failure mode of ReBCO tapes under mechanical stress. It was found that the fatigue failure of ReBCO tapes under mechanical stresses originates from crack extension [18,19] and provides a potential direction for improving the mechanical quality of these tapes [20]. To summarize, the present studies primarily concentrate on two forms of current, namely AC and DC, with ReBCO tapes serving as the fundamental object of study.…”

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.…”

“…Mitsui et al constructed a crack propagation model developed by the fatigue stresses [15], where the crack length will be increased by the repeated stresses. Rogers et al concluded that the main sources of fatigue failure were the defects from the manufacturing process leading to crack propagation [16,17]. Researchers mainly focused on edge cracks under fatigue tensile stress, and believed that egde cracks act as stress concentrators and grow during fatigue.…”