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Gorospe, A.,Nisay, A.,Shin, H.S. North-Holland 2014 Physica. C, Superconductivity Vol.504 No.-
Laminated HTS coated conductor (CC) tapes having a unique multi-layer structure made them vulnerable when exposed to transverse loading. Electromechanical transport properties of these CC tapes can be affected by excessive transverse stresses. Due to the coefficient of thermal expansion (CTE) mismatch and incompatibility among constituent materials used in coil applications, delamination among layers occurs and causes critical current, I<SUB>c</SUB> degradation in the CC tapes. In this study, the delamination behaviors in copper (Cu) solder-laminated CC tapes by soldering and surround Cu-stabilized ones by electroplating under transverse tension loading were investigated. Similarly to the surround Cu-stabilized CC tapes in our previous reports, the Cu solder-laminated CC tapes also showed an abrupt and gradual I<SUB>c</SUB> degradation behavior. However, the Cu solder-laminated CC tapes showed different delamination morphologies as compared to the surround Cu-stabilized CC tapes; the superconducting side and the substrate side of the Cu solder laminated CC tapes were totally separated by delamination. On the other hand, the brass laminate did not show any significant effect on the delamination strength when it is added upon the surround Cu-stabilized CC tapes.
Delamination behaviour of GdBCO coated conductor tapes under transverse tension
Gorospe, A.,Nisay, A.,Dizon, J.R.,Shin, H.S. North-Holland 2013 Physica. C, Superconductivity Vol.494 No.-
The electromechanical property behaviour of 2G coated conductor (CC) tapes fabricated by multi-layer deposition process both in the in-plane and transverse direction should be understood. The CC tapes are used in the fabrication of epoxy resin-impregnated coils. In such case, the Lorentz force due to the high magnetic field applied as well as the thermal stress due to the difference in coefficient of thermal expansion (CTE) among constituent layers during cooling to cryogenic temperature will induce transversely applied load to the surface of CC tapes in coils. Hence, the CC tape should have a good mechanical property in the transverse direction in order to maintain its superior performance under magnetic field. In this study, a test frame which gives precisely aligned transverse load was devised. Using the fixture, the delamination behaviours including the delamination strength of the GdBCO CC tapes under transverse tensile loading were investigated. Large variation on the delamination strength of the CC tapes was recorded and might have resulted from the slit edge effect and the inhomogeneity of the CC tapes. The I<SUB>c</SUB> degradation behaviour under transverse load was related to the location where delamination occurred in the sample.
Shin, Hyung-Seop,Nisay, Arman,Dedicatoria, Marlon,Sim, KiDeok The Korea Institute of Applied Superconductivity a 2014 한국초전도저온공학회논문지 Vol.16 No.2
The critical current, $I_c$ of HTS superconducting tapes can be measured by transport or contactless method. Practically, the transport method using the four-probe method is the most common. In this study, a simple test procedure by clipping the voltage lead taps have been introduced instead of soldering which reduces time and effort and thereby achieving a much faster measurement of $I_c$. When using a pair of iron clips, $I_c$ value decreased as compared with the measured one by standard method using soldered voltage taps and varies with the width of the clipped specimen part. However, when using a pure Cu clip, both by clipping and by soldering voltage taps give a comparable result and $I_c$ measured are equal and close to the samples specification. As a result, material to be used as voltage clip should be considered and should not influence the potential voltage between the leads during $I_c$ measurement. Furthermore, the simulation result of magnetic flux during $I_c$ measurement test showed that the decrease of $I_c$ observed in the experiment is due to the magnetic flux density, $B_y$ produced at the clipped part of the sample by the operating current with iron clips attached to the sample.
Joining of REBCO Coated Conductor Tapes Using Ultrasonic Welding Method
Hyung-Seop Shin,Nisay, Arman,de Leon, Michael B.,Dedicatoria, Marlon J. Institute of Electrical and Electronics Engineers 2015 IEEE transactions on applied superconductivity Vol.25 No.3
<P>In coil manufacturing for magnets and other electrical device applications that require long lengths of tapes, the joining of coated conductor (CC) tapes is still necessary. The joint is a critical part that may affect the performance of a particular device during its operation. Thus, a practical joint method which has a strong adhesion and low contact resistance without critical current I<SUB>c</SUB> degradation should be developed to meet both purposes of electrical and mechanical connections. In this study, a new joint method using ultrasonic welding (UW) was introduced and the parametric tests were performed to produce a good quality of UW joint. The mechanical-controlled solder joint method was also adopted for comparison. The electrical properties such as I<SUB>c</SUB> and specific joint resistance R<SUB>sj</SUB> were measured at 77 K and the results were compared for each method.</P>
Analysis of Thermal Residual Stress/Strain in REBCO Coated Conductor Tapes
Dizon, John Ryan C.,Nisay, Arman Ray N.,Dedicatoria, Marlon James A.,Munoz, Rodrigo C.,Hyung-Seop Shin,Sang-Soo Oh Institute of Electrical and Electronics Engineers 2014 IEEE transactions on applied superconductivity Vol.24 No.3
<P>2G HTS coated conductor (CC) tapes are now used for electric device applications. The residual stress/strain induced in HTS coating films in CC tapes during cool down influences the critical current, Ic, and should be investigated. In this study, the thermal residual stress/strain induced in the REBCO coating film was calculated from deposition temperature (1073 K) to 77 K by thermo-mechanical analysis and numerical simulation. Additionally, the improvement in irreversible strain limit, εirr., with copper electroplating has been investigated.</P>