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Bending Strain Dependence of the Transport Property in Jointed BSCCO Tapes
Dedicatoria, Marlon J.,Shin, Hyung-Seop The Korean Society of Superconductivity and Cryoge 2010 한국초전도저온공학회논문지 Vol.12 No.2
In this study, the effect of bending strain on the transport property and critical current of lap and butt-jointed (non-laminated) BSCCO tapes has been investigated. The samples were joined using a mechanically controlled jointing procedure. To achieve a uniform thickness at the joint a single point loading contact has been devised. GFRP mandrels with different bending radii which support the sample during bending have been used. $I_c$ have been measured at 77 K and self field. In the case of easy bending test for jointed BSCCO tapes, sudden degradation of $I_c$ is caused by the local strain concentration due to non uniform deformation at the edge parts of the joint. In the case of hard bending test of jointed BSCCO tapes transverse macroscopic crack at specific subsection caused a large $I_c$ degradation. The transport property of jointed BSCCO tapes in each bending mode was discussed with the damage morphology occurred.
Dedicatoria, Marlon J.,Bautista, Zhierwinjay,Shin, Hyung-Seop,Sim, Kideok American Institute of Physics 2015 Review of scientific instruments Vol.86 No.8
<P>In this note, the effectiveness of voltage tap clipping technique was assessed in evaluating the electromechanical properties of high temperature superconductor (HTS) tapes in the aspect of practical device applications. In the four-probe transport I-c measurement, instead of directly soldering the voltage lead wires onto the HTS samples, they were tapped to the sample by either just clipping or soldering them to the clips. This technique facilitated the simultaneous and repeated retained I-c measurement test for multiple samples. Finally, the critical double bending diameter of HTS tapes and the electrical properties of jointed and striated coated conductor tapes could be easily determined. (C) 2015 AIP Publishing LLC.</P>
Influence of Edge Geometry on the Delamination Strength of REBCO CC Tapes Using Anvil Test Method
Gorospe, Alking,Dedicatoria, Marlon James,Hyung-Seop Shin Institute of Electrical and Electronics Engineers 2016 IEEE transactions on applied superconductivity Vol.26 No.4
<P>In wet-wound epoxy impregnated coils, the whole coated conductor (CC) tape structure experiences radial/ transverse tensile stress due to large Lorentz force, which might induce delamination damage and in turn affects its transport performance during operation. The characterization of the delamination strength of CC tapes is therefore necessary for such practical applications. The anvil testing method was done to characterize the mechanical properties of REBCO CC tapes considering the possible transverse tensile stress condition in CC tape windings in coil applications. The delamination strength of three different CC tape samples slit from a 12-mm-wide one was determined using two different sized upper Cu anvils. It was observed that the slitting process has resulted to different CC tape edge geometries such as burrs and filleted corners of the substrate layer. As a result, significantly lower mechanical delamination strength was exhibited by the CC tapes when their whole width was covered by the upper anvil. Using the wide upper anvil, the edge geometry such as burrs and thick stabilizing layer played an important role on the delamination damage of the CC tape. Using a statistical method, the intrinsic strength of the CC tapes was distinguished from those that were affected by poor soldering, misalignment, and other external factors during the tests. Delamination sites mainly occurred within the REBCO film and on the buffer/REBCO interface. Finally, delamination schematics were drawn based on the delaminated CC tape's morphology.</P>
Delamination Characteristics in Wide REBCO Coated Conductor Tapes Under Transverse Loading
Gorospe, Alking,Dedicatoria, Marlon J.,Hyung-Seop Shin Institute of Electrical and Electronics Engineers 2015 IEEE transactions on applied superconductivity Vol.25 No.3
<P>Superior characteristics and great potential of coated conductor (CC) tapes are some of the promises in pursuit of energy efficient application in electrical field. However, in electric device applications, the coefficient of thermal expansion (CTE) mismatch of each constituent layer, screening current, excessive radial tensile stresses during operation, and other coil fabrication related reasons might cause delamination damage in CC tapes. It was reported that the delamination among its constituent layers resulted to the degradation of its electromechanical properties on coil application. Therefore, the investigation on its delamination behavior is necessary for device application design. In this study, using the anvil test method, the delamination behaviors in 12-mm-wide Cu stabilized and brass laminated GdBa<SUB>2</SUB>Cu<SUB>3</SUB>Oy CC tapes with stainless steel substrate were investigated. The mechanical delamination strength of the CC tapes for differently assembled upper anvil and CC tape configurations about widthwise direction was investigated by using a 4 mm × 8 mm size upper anvil. Mechanical delamination strength of the CC tape was not enhanced by the addition of brass laminate and showed no significant difference depending on the superconducting side or the substrate side. Furthermore, both CC tapes exhibited similar delamination mechanisms and sites but showed different fracture morphologies.</P>
Hyung-Seop Shin,Dedicatoria, Marlon J IEEE 2010 IEEE transactions on applied superconductivity Vol.20 No.3
<P>Although long-length superconducting wires are now being developed and manufactured, there is still a need for jointing in coil manufacturing and power cables for power distribution which requires miles in length. Therefore, it is important to develop an easy and practical jointing that has an acceptable electrical and mechanical integrity. Depending upon the applications, jointed coated conductor (CC) tapes will experience different stresses and strains during manufacturing and operation that could affect its transport property. Bending strain characterization is necessary since CC tapes are being wound into coils for magnet applications and other electrical devices. In this study, two joint types soldered by mechanical controlled jointing with uniform pressure application have been adopted. Critical currents of the jointed tapes have been measured at 77 K and self field. In the case of easy bending test, a new test procedure has been adopted considering the non-uniform flexural stiffness between jointed and unjointed parts of the sample. Relationship between the critical current and bending strain in easy bending mode has been investigated.</P>
Shin, Hyung-Seop,Dedicatoria, Marlon J.,Gorospe, Alking,Lee, Sang-Heon American Institute of Physics 2015 Review of scientific instruments Vol.86 No.3
<P>The continued development in the design technology of practical superconducting devices adopting high temperature superconductors tapes has led to a deeper understanding of their electromechanical behaviors. Rare-earth-barium-copper-oxide coated conductor (CC) tapes exhibit anisotropy of transport property (I-c) under magnetic field and its intrinsic strain effect is much significant depending on the orientation to the tape surface and the magnetic field intensity applied. Different experimental systems have already been developed to measure the relation of I-c with mechanical strain epsilon, magnetic field intensity B, and its angle of orientation, theta. However, few systems and instruments can measure these relationships simultaneously; either I-c-B-theta or I-c-epsilon-B is usually measured. In this study, a device which can measure these influences simultaneously based on a pair of permanent magnet systems was constructed and the characteristic responses of critical current I-c with strain, magnetic field, and its orientation with respect to the CC tape surface were investigated. The angular dependence of I-c with strain at 77 K in reactive co-evaporation by deposition and reaction GdBCO CC tapes has been measured using the permanent magnet system. The orientation angle of magnetic field with respect to the tape's surface was varied by rotating the rig fixture that holds a pair of permanent magnets. The strain sensitivity of I-c at different angles under low magnetic field was evaluated. As a result, a characteristic surface I-c (epsilon, theta, B) has been constructed as the characteristic response of I-c with strain and varying orientation under magnetic field. (C) 2015 AIP Publishing LLC.</P>