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Hyung-Seop Shin,Dedicatoria, M. J.,Ho-Sup Kim Institute of Electrical and Electronics Engineers 2012 IEEE transactions on applied superconductivity Vol.22 No.1
<P>In this paper, in order to ensure its performance in practical applications, the mechanical and electromechanical properties of thick-film evaporation-in-dual chamber (EDDC)-SmBCO coated conductor (CC) tapes with high critical current have been investigated. The effect of CC tape architecture and film thickness on critical current <I>Ic</I> in EDDC-SmBCO CC tapes with thick film under uniaxial tension and bending deformation was measured and compared with the Cu-stabilized sample. By adopting a bridge pattern and by applying a magnetic field and some measures, the electromechanical property of thick-film CC tapes with high <I>Ic</I> could be evaluated, suppressing the burnout during deformation. As a result, increasing the SmBCO film thickness affects the irreversible strain limit and <I>Ic</I> degradation behaviors. In the case of a 5- μm-thick film, an acceptable bending strain tolerance 0.34% was measured and the uniaxial irreversible strain limit of 0.28% can be still improved by an additional Cu stabilizer.</P>
Electro-mechanical Property Evaluation of REBCO Coated Conductor Tape with Stainless Steel Substrate
Dedicatoria, M.J.,Shin, H.S.,Ha, H.S.,Oh, S.S.,Moon, S.H. The Korean Society of Superconductivity and Cryoge 2010 한국초전도저온공학회논문지 Vol.12 No.4
In this study, the electromechanical property of REBCO coated conductor (CC) tape adopting a stainless steel substrate has been investigated. Sample was subjected to uniaxial tension and measured its mechanical properties at RT and 77 K. $I_c-{\varepsilon}_t$ relations was also studied in which the strain and stress corresponding to the 95% $I_c$ retention and reversible strain limit were measured. In addition, these results were compared to the case of conventional REBCO CC tape adopting a Hastelloy substrate. As a result, by adopting a stainless steel substrate comparable strength and good electromechanical property to Hastelloy one could be achieved.
Dedicatoria, M. J.,Shin, H. S. IEEE 2013 IEEE transactions on applied superconductivity Vol.23 No.3
<P>Critical current, <I>I</I><SUB>c</SUB>, in REBCO coated conductor (CC) tapes may increase or decrease reversibly within the reversible region with stress/strain but degrade permanently beyond the irreversible limits due to cracking of the superconducting film. Analyzing quantitatively the stress/strain tolerances of <I>I</I><SUB>c</SUB> is of importance on the possibility to suppress the onset of cracking on the REBCO coating film. In this study, the stress/strain tolerance of GdBCO CC tapes was experimentally measured from <I>I</I><SUB>c</SUB> -strain measurement test at 77 K. The improvement in the irreversible strain limit in CC tapes was analyzed by calculating the pre-compression induced by additional layers. The increase of about 0.10%-0.15% in irreversible strain limit with additional Cu and brass laminate is much larger compared with the measured 0.03%-0.06% residual strain due to thermal contraction difference among constituent layers. This result showed that the improvement in the ε<SUB>irr</SUB> cannot be solely explained by the coefficient of thermal expansion difference among constituent layers.</P>
Shin, H.S.,Dedicatoria, M.J.,Lee, N.J.,Oh, S.S. The Korean Society of Superconductivity and Cryoge 2009 한국초전도저온공학회논문지 Vol.11 No.4
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.
H.S. Shin,M. J. Dedicatoria,N.J. Lee,S.S. Oh 한국초전도저온학회 (구 한국초전도저온공학회) 2009 한국초전도저온공학회논문지 Vol.11 No.4
The Ic 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 Ic-strain window; Ic 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, Ic 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, Ic showed a larger degradation and a lower reversible limit when compared with the case of continuous application of the bending strain. When Ic 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.
Bending strain characteristics of critical current in REBCO CC tapes in different modes
Shin, H.S.,Dedicatoria, M.J.,Dizon, J.R.C.,Ha, H.S.,Oh, S.S. North-Holland 2009 Physica. C, Superconductivity Vol.469 No.15
The influences of bending strain on the critical current, I<SUB>c</SUB> in stabilized YBa<SUB>2</SUB>Cu<SUB>3</SUB>O<SUB>7-δ</SUB>; (YBCO) and SmBCO coated conductor (CC) tapes in different modes of easy and hard bending were investigated at 77K and self-field. Under easy bending, the influences of the compressive and tensile bending strains on the I<SUB>c</SUB> in REBCO (rare earth element, Barium and Copper oxide) CC tapes were investigated. Under tensile bending strain, when the I<SUB>c</SUB> was plotted against the strain on the YBCO film layer, the 95% I<SUB>c</SUB> retention strain limit under bending was comparable to the value obtained in the axial-tension test. Under the hard bending of YBCO CC tape, I<SUB>c</SUB> started to degrade when the bending strain exceeded 0.6% and the recovery of I<SUB>c</SUB> did not occur when the bending strain applied was released. This might be a result of the generation of a new type of damage such as local buckling during hard bending which is different from the damage type experienced in Bi-2223 tapes. The n-value behavior showed a good agreement with the I<SUB>c</SUB> degradation behavior. On the other hand, the SmBCO CC tape showed a superior strain tolerance under hard bending resulted from its flexibility to in-plane deformation due to thin geometry compared to other copper stabilized YBCO CC tapes.
Shin, H. S.,Dedicatoria, M. J.,Gorospe, A.,Suwa, T.,Oguro, H.,Awaji, S. IEEE 2013 IEEE transactions on applied superconductivity Vol.23 No.3
<P>In this study, the reversible response of <I>I</I><SUB>c</SUB> with uniaxial strain in differently processed GdBCO coated conductor tapes with different substrates has been investigated under self field and magnetic field conditions at 77 K. Higher irreversible strain limit, ε<SUB>irr</SUB> was observed in those samples with stainless steel substrate. Additional brass lamination to the Cu-stabilized samples produced enhancement of both ε<SUB>irr</SUB> and endurable load limit. However, no significant widening of the <I>I</I><SUB>c</SUB>/<I>I</I><SUB>c0</SUB>-tensile strain window with brass addition was observed in the case of samples having stainless steel substrate. Furthermore, under magnetic field, the <I>I</I><SUB>c</SUB> degradation behavior was independent on the kind of substrate material, but varied with the kind of manufacturing process adopted. The GdBCO samples showed different <I>I</I><SUB>c</SUB> peak positions and degradation behavior depending on the level of magnetic field applied.</P>
Shin, H.S.,Dedicatoria, M.J. North-Holland 2010 Physica. C, Superconductivity Vol.470 No.20
In the case of 2G coated conductor (CC) tapes, it has been reported that thin-thick CC tapes with IBAD substrate showed a superior electromechanical property even at smaller bending radius compared with the cases of 1G BSCCO tapes. Considering the application of CC tapes it is significant to evaluate the transport property under operating environment, because CC tapes might experience a change in operating pressure that can affect its current carrying capacity due to temperature variation and deformation. This study was focused on the I<SUB>c</SUB> degradation behavior in bent CC tapes under pressurized liquid nitrogen. Differently processed YBCO and SmBCO CC tapes with IBAD substrate are used as samples. The bending strain characteristics at elevated pressure levels were evaluated by using the ρ-shaped sample holder which can induce different bending strain values at pressured state. Depressurization and thermal cycling were performed to check the reversibility of I<SUB>c</SUB> in CC tapes. Vacuuming tests were also carried out to investigate the characteristics of I<SUB>c</SUB> at different LN<SUB>2</SUB> temperature levels.