A number of advanced magnetic materials, structure and stability of the fracture mechanical properties of the theory

　　Title: A number of advanced magnetic materials, structure and stability of the fracture mechanical properties of the theory
　　Author: Yong East
　　Degree-granting units: Lanzhou University
　　Keywords: power - electricity - more than the magnetic coupling material;; high-temperature superconducting material;; Bean model;; Kim model;; crack;; magnetostriction;; mixed;; electric field activated polymer;; balloon;; stability ;; perturbation Rare earth magnets method;; viscoelastic;; electromagnetic elastic material;; FGM
　　Abstract:
　　Power - electricity - more than the magnetic coupling of magnetic materials due to its special nature of the broad background of potential applied to engineering, fracture and stability of its mechanical characteristics such as magnetic materials have become concerned about the application design, the basic issue. This dissertation focused on superconducting materials, electric field activated polymer, pressure and function of voltage gradient magnetic materials, advanced magnetic materials of current interest, considering its power - electric - magnetic coupling, based on the theoretical study of the application of these materials interest in the stability of the fracture and mechanical properties.
　　First, the analysis of the superconducting material of the stress and magnetostriction, and crack. According to elasticity theory, discussed the flux pinning in superconductors resulting in stress and non-superconducting state of superconductors inclusion problem, discussed the stress distribution within the superconductor and the elastic modulus and volume fraction of the magnetostriction of superconducting composites impact. In addition, a small crack model based on simple, ignoring the crack of the shielding currents and magnetic field disturbance and impact. The use of non-ideal superconductors in the first class Ⅱ and Kim Bean critical state model, and by solving methods in fracture mechanics, are discussed in rectangular and cylindrical superconductors crack problem. Analysis of the field cooling and zero field cooling magnetization process of two kinds of superconductors, the crack tip stress intensity factor variation. Decline in the course of the different magnetic fields, stress intensity factor changes with the magnetic field is different. The Bean model the change in stress intensity factor and Kim model, there are also differences.
　　Second, activation of the electric field in the stability of the polymer and viscoelastic problems. Maxwell stress, using a simple model to discuss the electric field-activated polymer balloon expansion by the electric field arising in the course of stability problems. Balloon failure modes and material properties and the way the electric field of the load. Perturbation method based on analysis of the electric field under small disturbance in the stability of activated polymer obtained under different electric field values ​​of the critical stretch. Electric field in the electromechanical activation of the http://www.chinamagnets.biz/  polymer is not the same parameters, material changes of stability are different. Meanwhile, based on tensor analysis and finite element method, discussed under the electric field in the viscoelastic polymer behavior, the numerical results obtained consistent with the theoretical solution. The results given in a constant electric field of the creep behavior and periodic electric field of the deformation.
　　Finally, we discuss the elastic functionally graded materials and electromagnetic materials in the crack problem. Through the Fourier transform method, functionally graded materials has been static crack problem of singular integral equations, and numerical solution. Analysis of non-uniform constants, geometry and thickness ratio of Ⅲ crack stress intensity factor. For the electromagnetic elastic material in the dynamic crack problem, the use of Laplace transform and inversion, was impermeable crack problem of singular integral equations. The results are given relative load parameters κD and κB and crack configuration in the cracks of the electromagnetic elastic dynamic behavior. For an impermeable crack, the impact of electric and magnetic fields for dynamic stress intensity factor and dynamic energy release rate has important implications.
　　Degree Year: 2010