Abstract
YBCO-coated conductor tape is a composite material that consists of two or more layers. The superconducting layer is generally a thin film. In this study, the YBCO consisted of columnar aggregates of orthorhombic crystals with a texture whose axis was 001 to the film surface. Due to the difficulty of obtaining such a thin film for mechanical testing, the mechanical elastic constant is unknown. The elastic constant of the thin film can be obtained only via analysis. In this study, finite element models of bi-textured thin films were constructed. Through the analysis, the uniaxial mechanical elastic constant and in-plane Poisson's ratio were obtained. The strain dependence of the elastic properties of the YBCO-coated conductor with surrounding Cu stabilized were investigated precisely using white X-ray diffraction. The diffraction elastic constants estimated from (0k0) were larger than those estimated from (h00), and this tendency corresponded to the FEM analysis. Using X-ray diffraction, the obtained diffraction strain was smaller than the macroscopic strain. The diffraction strain - macroscopic strain slope theoretically become one. Strain relaxation will result if the slope does not become one. Our observations strongly suggest that strain relaxation is caused in the interface of twin crystals. The effective mechanical elastic constant was predicted by correcting the calculated mechanical elastic constant.
