Electromagnetic mechanical behavior of a superconducting coating for HTS tapes with local detachment

High temperature superconducting tapes has been widely investigated in the field of superconducting technology due to its outstanding advantages of high current carrying, low loss and high cost performance. However, the superconducting tape is a multi-layer structure consisting of the Hastelloy alloy substrate, the buffer layer, the YBCO superconducting layer and the protective layer. Its multi-layer structure characteristics including the difference in the properties of each material layer and the complex external field environment will cause local debonding. It is very easy to degrade the transmission performance and mechanical properties. In this paper, the mechanical response of locally detachment YBCO high-temperature superconducting tapes under the excitation of an external vertical magnetic field is studied. Based on the superconducting critical state Bean model and the elasticity plane strain method, the interface between the normal stress of the superconducting film and the substrate is given. The governing equations related to the shear stress, numerically calculated the normal stress in the superconducting film and the shear stress at the substrate interface with the external magnetic field. The results show that the normal stress in the superconducting film and the shear stress at the substrate film interface increase rapidly near the detachment region. At the same time, the maximum shear stress appears at the edge of the structure. The properties of the substrate material, especially the Young's modulus, has a significant effect on the stress in the structure. In the structure of soft substrate material, there is a large normal stress in the superconducting film, and when the Young's modulus of the substrate is larger, a larger shear stress appears at the substrate film interface. These factors will cause the degradation of mechanical and electrical properties of superconducting coating structure. The work may provide some theoretical guidance for fabricating the superconducting tapes and and suppression of layer debonding. © 2021, Chinese Journal of Theoretical and Applied Mechanics Press. All right reserved.