Friday, 2E-17, -

Stress States and Electromechanical Behavior of YBCO Coated Conductor under Combined Tension and Torsion

Goran Majkic

Robert J. Mensah, Venkat Selvamanickam, Yi-Yuan Xie+ and Kamel Salama

Texas Center for Superconductivity, University of Houston, Houston, TX
+SuperPower Inc., Schenectady, NY
* Phone: 713-743-8270, Fax: 713-743-4503, Email: gmajkic@uh.edu

For many coated conductor applications, most notably various coil configurations, a combination of tensile and torsion strain is expected to be routinely present in the superconducting wire, which makes it of interest to study the electromechanical response of coated conductors, as well as to develop models for quantifying the stress/strain states under these loading conditions. We present experimental results on the electromechanical behavior of an IBAD/MOCVD YBCO coated conductor subjected to combined tensile and torsion strains, as well as analytical and numerical results of modeling the stress states in multilayered coated conductors, based on a continuum mechanics formulation. In pure torsion, the upper strain limit was found to be approx. 51.4°/cm where the critical current dropped significantly upon applying even minute tensile loads. In the mixed tensile/torsion regime, three distinct regions are identified: negligible effect of torsion up to 26o/cm, near-linear decrease of critical current between 26 and 47°/cm and sudden drop of critical current between 47 and 52°/cm. The model of the stress/strain states reveals the following features in a coordinate frame where x and y axes coincide with the long and short wire cross section directions, respectively. The xz stress is discontinuous across interfaces due to different elastic constants of the layers, and high uniformity of the xz stress is noted in the YBCO layer, approx. 475 MPa/(rad/cm). The yz shear stress, and the corresponding interface tractions are non-negligible only near the wire ends in the x direction. By neglecting the yz stresses, we present an approximate analytical solution for xz stresses and strains as a function of applied twist angle.

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