• 한국초전도ㆍ저온공학회논문지
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• 제16권4호
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• pp.7-16
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• 2014

Rare-earth barium copper oxide (REBCO) coated conductor (CC) tapes have already been commercialized but still possess some issues in terms of manufacturing cost, anisotropic in-field performance, $I_c$ response to mechanical loads such as delamination, homogeneity of current transport property, and production length. Development on improving its performance properties to meet the needs in practical device applications is underway and simplification of the tape's architecture and manufacturing process are also being considered to enhance the performance-cost ratio. As compared to low temperature superconductors (LTS), high temperature superconductor (HTS) REBCO CC tapes provide a much wider range of operating temperature and a higher critical current density at 4.2 K making it more attractive in magnet and coil applications. The superior properties of the REBCO CC tapes under magnetic field have led to the development of superconducting magnets capable of producing field way above 23.5 T. In order to achieve its optimum performance, the electromechanical properties under different deformation modes and magnetic field should be evaluated for practical device design. This paper gives an overview of the effects of mechanical stress/strain on $I_c$ in HTS CC tapes due to uniaxial tension, bending deformation, transverse load, and including the electrical performance of a CC tape joint which were performed by our group at ANU in the last decade.

• 한국초전도ㆍ저온공학회논문지
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• 제7권3호
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• pp.29-33
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• 2005

Critical current$(I_c)$ degradation of High $T_c$ Superconducting(HTS) tapes and AC loss under mechanical load is one of the hottest issues in HTS development and application. Mechanical load reduces the critical current of superconducting wire, and the $I_c$ degradation affects the AC loss of the wire. We measured the $I_c$ degradation and AC loss under tension and bending of Bi-2223 tapes made by 'Powder-in-Tube' technique at 77K with self-field. Also, we have studied the frequency characteristics on self-field AC loss in multi-filamentary Bi-2223/Ag tape at 77K. The measurement results and discussions on the relationship between $I_c$ degradation and AC loss are presented.

• 한국초전도ㆍ저온공학회논문지
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• 제11권4호
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• pp.12-15
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• 2009

The $I_c$ degradation behavior of critical current in differently processed YBCO and SmBCO CC tapes with IBAD template has been investigated. It has been known that the residual strain in the CC tape will influence the shape of the $I_c$-strain window; $I_c$ may show a peak value if there exist a residual strain induced in the tape during manufacturing. The difference of residual strain may be resulted from the adopted different deposition techniques. In this study, bending test of CC tapes has been done using the Goldacker bending test rig which can produce both compressive and tensile bending strain continuously or alternately to the sample. For SmBCO CC tapes, in continuous compressive bending test, $I_c$ showed a minimal increase and did not degrade up to the largest strain that can be applied using the bending rig equivalent to 1.15% based on the sample thickness. However, in the case of alternate application of compressive and tensile bending strain, $I_c$ showed a larger degradation and a lower reversible limit when compared with the case of continuous application of the bending strain. When $I_c$ started to degrade significantly at the tension side, the reversibility ended, also at the compression side which is resulted from the permanent deformation like delamination or cracks that was induced due to tensile bending strain.

• 한국초전도ㆍ저온공학회논문지
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• 제18권4호
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• pp.21-24
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• 2016

The mechanical properties of REBCO coated conductor (CC) wires under uniaxial tension are largely determined by the thick component layers in the architecture, namely, the substrate and the stabilizer or even the reinforcement layer. Depending on device applications of the CC tapes, it is necessary to reinforce thin metallic foils externally to one-side or both sides of the CC tapes. Due to the external reinforcement of brass foils, it was found that this could increase the reversible strain limit from the Cu-stabilized CC tapes. In this study, the effects of differently hardened brass foil laminate on the electromechanical property of CC tapes were investigated under uniaxial tension loading. The tensile strain dependence of the critical current ($I_c$) was measured at 77 K and self-field. Depending on whether the $I_c$ of CC tapes were measured during loading or after unloading, a reversible strain (or stress) limit could be determined, respectively. The both-sides of the Cu-stabilized CC tapes were laminated with brass foils with different hardness, namely 1/4H, 1H and EH. From the obtained results, it showed that the yield strength of the brass laminated CC tapes with EH brass foil laminate was comparable to the one of the Cu-stabilized CC tape due to its large yield strength even though its large volume fraction. It was found that the brass foil with different hardness was mainly sensitive on the stress dependence of $I_c$, but not on the strain sensitivity due to the residual strain induced in the laminated CC tapes during unloading.

• 한국전기전자재료학회논문지
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• 제14권1호
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• pp.69-73
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• 2001

In this study, we fabricated Bi-2223/Ag high temperature superconducting tapes using PIT(Powder-In-Tube) process to apply the superconducting magnet, cable and etc. It is inevitable to deform the superconducting taps with axial strain for application. Therefore, for the characterization of the strain sensitivity of the superconducting properties, the degradation of Bi-2223/Ag tapes due to axial strain were investigated by measuring the critical current as a function of applied tension strain and external magnetic field. The critical current of Bi-2223/Ag tapes were decreased slightly up to 0.3∼0.4% applied strain but, drastically decreased more than these strains. Superconducting filament cores consisted of brittle ceramic fibers were broken easily by the large strain and current path were decreased simultaneously.

• 한국초전도저온공학회:학술대회논문집
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• 한국초전도저온공학회 2003년도 추계학술대회 논문집
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• pp.63-66
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• 2003

1 km length of Bi-2223/Ag superconducting wires were fabricated by stacking, drawing process with advanced heat-treatment schedules. Intermediate annealing was carried out to increase the homogeneity and uniformity of the superconducting filaments embedded in the silver matrix. Phase modification from tetragonal to orthorhombic Bi-2212 by pre heat treatment(PHT) was executed to improve the texture and phase transformation of Bi-2223. Drawing stress was measured to Predict the sausaging and stress limit, Rolling parameters such as thickness, width and winding tension were investigated to roll the tape with uniformity. Critical current of 1 km length of superconducting tapes was measured about 50 A continuously after final sintering.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2000년도 하계학술대회 논문집
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• pp.810-813
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• 2000

In this study, we fabricated Bi-2223/Ag high temperature superconducting tapes using PIT (Powder-In-Tube) process to apply the superconducting magnet, cable and etc. It's inevitable to deform the superconducting tapes with axial strain for application. Therefore, for the characterization of the strain sensitivity of the superconducting properties, the degradation of Bi-2223/Ag tapes due to axial strain were investigated by measuring the critical current as a function of applied tension strain and external magnetic field. The critical current of Bi-2223/Ag tapes were decreased slightly up to 0.3∼0.4% applied strain but, drastically decreased more than these strains. Superconducting filament cores consisted of brittle ceramic fibers were broken easily by the large strain and current path were decreased simultaneously.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2003년도 하계학술대회 논문집 B
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• pp.903-905
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• 2003

High temperature superconductor (HTS) tapes are now commercially available for practical applications to apply various purposes. However HTS tapes show different electrical and mechanical characteristics, according to the manufacturers who are trying to apply various fabrication processes and treatments. From the viewpoint of an application it is very important to investigate the properties of HTS tapes under mechanical stress because the tapes will be wound with twisting and tension in applications such as magnets and cables. Thus, we studied characteristics of HTS tapes and measure critical current under bending, considering of a mechanical conditions. A description of some typical results will be presented with discussions.

• Composites Research
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• 제24권2호
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• pp.22-29
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• 2011

높은 내압을 받는 장축후육실린더의 성능향상을 위해 최근 그 길이가 길어짐에 따라 무게 또한 무시할 수 없는 변수로 떠오르게 되었다. 따라서 본 논문은 이러한 현상에 대처하기위한 대안으로 장축후육실린더의 무게를 줄이고 대신 복합재 테이프를 감아 무게감소와 더불어 벤딩 (bending)현상을 줄이기 위한 목적으로 복합재가 AISI4340 후육실린더에 미치는 영향을 살펴보았다. 우선 크기가 감소된 AISI4340 후육실린더에 높은 내압을 받는 압력용기 등에 주로 사용되는 자긴가공(autofrettage) 공법을 모사한 후 T300/S208, IM7/PETI5, IM7/8552 테이프를 적용하여 각각의 복합재가 AISI4340 후육실린더에 감을 때 발생되는 응력분포를 살펴봄으로써 탄성계수 및 적층각에 따른 영향을 고찰하였다. 또한 복합재IAISI4340 이중구조 후육실린더의 적층각 도출을 위한 다양한 적층각 조합용 통해 적층각 도출을 위한 전초를 마련하였다. 본 논문을 위한 해석에는 MSC.Nastran/Patran v.2005가 사용되었다.

• E2M - 전기 전자와 첨단 소재
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• 제8권3호
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• pp.316-323
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• 1995

A vital step in magnetic tape manufacturing is the surface modification of polymer substrate prior to ink application. A critical element for good adhesion of magnetic ink on polymeric substrate is the ability to join ink in cost-effective manner. Corona discharging is one of the effective methods of modifying polymer surface to improve adhesion while maintaining the desirable properties of the film itself. Surface treatment by corona which is exposure of film surface to electron or ion bombardment, rather than mere exposure to active species, like atomic oxygen or ozone, can enhance adhesion by removing contaminant, electret, roughening surface, and/or introducing reactive chemical groups. Reactive neutrals, ions, electron and photons generated during the corona treatment interact simultaneously with polymers to alter surface chemical composition, wettability, and thus film adhesion. However, it is highly recommended that extensive chains scission be avoided because it can lead to side-effect by forming sticky matter, resulting in dropouts. This paper reviews principles of surface preparation of polymer substrate by corona discharging. In addition, the experimental section provides a description of parameter optimization on corona discharging treatment and its side-effect. Experimental results are discussed in terms of surface wetting as determined by contact angle measurements.