Magnetostrictive behaviors of type-II superconducting cylinders and rings with finite thickness

This paper presents an investigation of the magnetostrictive behaviors of type-II superconducting cylinders and rings with finite thickness in the presence of a uniform applied field directed along the axis by means of the minimization of magnetic energy and the finite element method. The dependence of the magnetostriction and mechanical response upon the geometry of the superconductors is systematically studied in terms of Bean's critical state model with consideration of the demagnetizing effects. The results show that the magnetostriction curves for different geometric shapes of cylinders and rings have different features. The magnetostriction curve has a larger vertical width for a finite cylinder with a smaller aspect ratio, however it shows reversal behaviour for a ring with specific shapes. Flux-pinning-induced displacement and stress distributions are also presented. Simultaneously, the spatial distributions of the radial, hoop and axial stress components in a whole superconductor are shown during field rise from the virgin state, and subsequent field descent. It seems that the mechanical response of a finite sample is similar to that of an infinitely long or a thin superconductor, but it also has a difference due to the boundary and demagnetization effects.