Tensile fatigue behavior and crack growth in GdBa2Cu3O7−x /stainless-steel coated conductor grown via reactive co-evaporation

Rogers, Samuel; Schwartz, J.

doi:10.1088/1361-6668/aa604e

Cited by 29 publications

(17 citation statements)

References 18 publications

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“…The sudden collapse of the CORC ® wire I c with stress cycling at, or above σ irr , is very similar to what has been reported earlier on single REBCO tapes [28][29][30]. On the other hand, the decrease in I c with axial stress cycling is much more sudden, compared to the much more gradual decrease in I c under transverse compressive stress cycling [31].…”

Section: Effect Of Cyclic Axial Tensile Stress On the Performance Of supporting

confidence: 86%

Effect of monotonic and cyclic axial tensile stress on the performance of superconducting CORC^® wires

Laan

McRae

Weiss

2019

Supercond. Sci. Technol.

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High-current superconducting CORC ® wires, wound from RE-Ba 2 Cu 3 O 7−δ (REBCO) coated conductors, are being developed for use in high-field magnets that would allow operation at magnetic fields exceeding 20 T. The combination of high engineering current densities and high magnetic fields results in large Lorentz forces acting on the CORC ® wire that could cause irreversible degradation to its performance. The effect of axial tensile stress on the critical current of CORC ® wires containing annealed solid copper formers has been measured in liquid nitrogen to determine the irreversible stress limit at which irreversible degradation occurs. The results show no significant change in critical current before the irreversible stress limit is reached, after which the critical current decreases irreversibly with applied stress. The irreversible stress limit as high as 177 MPa depends on the yield strength of the former, the number of superconducting tapes wound into the CORC ® wire and the angle at which the tapes are wound. Although the irreversible stress limit of CORC ® wires is lower than a rudimentary rule of mixtures estimation would suggest, the irreversible strain limit, as high as 0.85%, exceeds that of single REBCO tapes. Both effects are likely the result of the helical fashion in which the REBCO tapes are wound into CORC ® wires. The performance of CORC ® wires was also measured as a function of axial tensile stress fatigue cycling in liquid nitrogen. No significant performance degradation was measured up to 100 000 cycles as long as the peak stress remained below the irreversible stress limit. Only once the peak stress was increased significantly above the irreversible stress limit would the critical current suddenly decrease with stress cycles. The results indicate that CORC ® wires have matured into extremely robust high-current magnet conductors capable of withstanding high levels of axial tensile stress and strain. The irreversible stress limit of CORC ® wires could be increased further by using stronger formers and winding the REBCO tapes at comparable angles, while the irreversible strain limit could potentially be increased by tailoring the winding angle of the REBCO tapes, making CORC ® wires one of the strongest and most elastic high-current superconducting magnet conductors available.

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Section: Effect Of Cyclic Axial Tensile Stress On the Performance Of supporting

confidence: 86%

Effect of monotonic and cyclic axial tensile stress on the performance of superconducting CORC^® wires

Laan

McRae

Weiss

2019

Supercond. Sci. Technol.

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“…Cracks that form in the REBCO layer when the irreversible strain limit under axial compression is exceeded only grow at a relatively low rate with load cycles. The degradation is much less severe with compressive load cycles compared to single REBCO tapes [35,36] and CORC ® wires [37] under axial tensile load cycling, suggesting that the crack growth rates are very different between the two modes of stress cycling.…”

Section: Discussionmentioning

confidence: 98%

Effect of transverse compressive monotonic and cyclic loading on the performance of superconducting CORC^® cables and wires

Laan

McRae

Weiss

2018

Supercond. Sci. Technol.

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Superconducting CORC ® cables and wires have become practical conductors for use in high-field magnets for fusion machines and particle accelerators by demonstrating their ability to carry very high currents in background magnetic fields of up to 20 T. The high mechanical stresses that develop on the CORC ® conductor during such operation could result in permanent degradation of the conductor critical current. Transverse compressive stress is one of the predominant mechanical stresses when CORC ® cables or wires are bundled into CICCs that allow fusion and detector magnets to operate at currents as high as 100 kA. The effect of transverse compressive load on the critical current of CORC ® cables and wires has been investigated at 76 K to determine their irreversible load limit under monotonic loading and load cycling up to 100 000 cycles. The results show a clear effect of the CORC ® conductor layout with respect to gap spacing between tapes, thickness of the copper plating surrounding the tapes and thickness of the former onto which the tapes are wound. CORC ® cables and wires have demonstrated a remarkable resilience to transverse compressive load cycling where their critical current decreased by no more than a few percent after 100 000 load cycles at peak loads that resulted in an initial decrease in critical current of less than 5%. The results indicate that no significant degradation of CORC ® cable and wire performance due to transverse compressive load is expected in large magnets after 100 000 load cycles, as long as the peak load on the conductor does not exceed the irreversible load limit defined at 95% retention in critical current. The irreversible load limit of CORC ® conductors could be increased further by increasing the size or hardness of the former that makes up the conductor's core.

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“…For example, the Little Big Coil (LBC) at the National High Magnetic Field Laboratory (NHMFL) has seen a post quench critical current degradation and it is suspected that this degradation is caused by defects introduced during slitting [19], an effect exacerbated by the screening current-induced stress in REBCO tape [20]. Tensile fatigue testing has shown that cracks in the REBCO and buffer layers due to slitting are the main cause of fatigue failure and they will grow as the number of cycles (N) increases [21]. In contrast, compressive fatigue testing showed no crack growth in the REBCO and buffer layers as N increased [22].…”

Section: Introductionmentioning

confidence: 99%

Characterization of edge damage induced on REBCO superconducting tape by mechanical slitting

et al. 2021

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Rare-earth barium-copper-oxide (REBCO) superconductors are high-field superconductors fabricated in a tape geometry that can be utilized in magnet applications well in excess of 20 T. Due to the multilayer architecture of the tape, delamination is one cause of mechanical failure in REBCO tapes. During a mechanical slitting step in the manufacturing process, edge cracks can be introduced into the tape. These cracks are thought to be potential initiation sites for crack propagation in the tapes when subjected to stresses in the fabrication and operation of magnet systems. We sought to understand which layers were the mechanically weakest by locating the crack initiation layer and identifying the geometrical conditions of the slitter that promoted or suppressed crack formation. The described cracking was investigated by selectively etching and characterizing each layer with scanning electron microscopy, laser confocal microscopy, and digital image analysis. Our analysis showed that the average crack lengths in the REBCO, LaMnO3 (LMO) and Al2O3 layers were 34 μm, 28 μm, and 15 μm, respectively. The total number of cracks measured in 30 mm of wire length was between 3000 and 5700 depending on the layer and their crack densities were 102 cracks mm−1 for REBCO, 108 cracks mm−1 for LMO, and 183 cracks mm−1 for Al2O3. These results indicated that there are separate crack initiation mechanisms for the REBCO and the LMO layers, as detailed in the paper. With a better understanding of the crack growth behavior exhibited by REBCO tapes, the fabrication process can be improved to provide a more mechanically stable and cost-effective superconductor.

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Tensile fatigue behavior and crack growth in GdBa₂Cu₃O_7−x/stainless-steel coated conductor grown via reactive co-evaporation

Cited by 29 publications

References 18 publications

Effect of monotonic and cyclic axial tensile stress on the performance of superconducting CORC^® wires

Effect of monotonic and cyclic axial tensile stress on the performance of superconducting CORC^® wires

Effect of transverse compressive monotonic and cyclic loading on the performance of superconducting CORC^® cables and wires

Characterization of edge damage induced on REBCO superconducting tape by mechanical slitting

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Tensile fatigue behavior and crack growth in GdBa2Cu3O7−x /stainless-steel coated conductor grown via reactive co-evaporation

Cited by 29 publications

References 18 publications

Effect of monotonic and cyclic axial tensile stress on the performance of superconducting CORC® wires

Effect of monotonic and cyclic axial tensile stress on the performance of superconducting CORC® wires

Effect of transverse compressive monotonic and cyclic loading on the performance of superconducting CORC® cables and wires

Characterization of edge damage induced on REBCO superconducting tape by mechanical slitting

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Product

Resources

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Tensile fatigue behavior and crack growth in GdBa₂Cu₃O_7−x/stainless-steel coated conductor grown via reactive co-evaporation

Effect of monotonic and cyclic axial tensile stress on the performance of superconducting CORC^® wires

Effect of monotonic and cyclic axial tensile stress on the performance of superconducting CORC^® wires

Effect of transverse compressive monotonic and cyclic loading on the performance of superconducting CORC^® cables and wires