Studies On Magnetostriction And Fracture Behavior Of Superconductors

Superconductors have many superior physical properties.Since the discovery of superconducting phenomena,great achievements have been made in both experimental and theoretical research.Based on the progress of superconducting technology,high temperature superconductors(HTS)has been widely used in various fields.In practical application,the mechanical properties of HTS often limit other superior properties,so the mechanical properties of HTS have always been the focus of scholars' attention.In this paper,the mechanical properties of HTS are studied from the following aspects.Firstly,the magnetoelastic behavior subjected to the electromagnetic body force induced by flux pinning is studied with Kim model for zero-field cooling(ZFC)magnetization process,in which the non-uniform parameter ? is considered for inclusion-superconducting matrix system.Based on the plane strain approach,the exponential distribution of critical-current density will lead to a larger trapped field and magnetostriction inside the inhomogeneous sample.Secondly,crack problem in a long cylindrical superconductor with viscous flux flow is studied by solving the Bean model and viscous flux flow equation simultaneously.Based on the plane strain approach and J-integral theory,the variation in the stress intensity factor was obtained.The results indicate that when with the crack lengths are compared,the effect of viscous flux flow on crack propagation is more significant.Finally,an analytical model of YBaCuO cylindrical superconductor with inclusions and central cracks is established.Based on the critical Kim model,the stress intensity factor at crack tip is solved by the finite element method.The influence of inclusions and cracks on shielding current is ignored.The numerical results show that,external magnetic field,Young's modulus of inclusion,inclusion-crack distance,the inclusion radius and the crack length have obvious effects on the crack of the cylindrical superconductor.