Study On Collinear And Interfacial Cracks In High Temperature Superconducting Materials

High-temperature superconductors have high critical transition temperature,which can carry large current and high trapping field.Because of these characteristics,superconductors have been widely used in aerospace,medical instruments,wear-free bearings,communication technology and other advanced equipment with high precision.However,superconductors are brittle materials.Defects such as holes,cracks and inclusions are inevitable in the manufacturing and processing process and in the use of components.In the use of superconducting materials,it is found that the mechanical properties of superconducting materials have a great influence on their electromagnetic characteristics,and even directly affect the use of their components,so it is very necessary to study the mechanical properties of superconducting materials for the preparation and use of superconducting components.This paper studies the fracture of superconducting materials under the condition of multi-field coupling,and the details are as follows:Based on orthotropic and orthotropic HTS materials,collinear cracks and periodic cracks are studied.The cracks are tiny cracks,and the influence of temperature rise on magnetic flux density is studied by using Fourier transform method and singular integral equation.The stress intensity factor at the crack tip is influenced by crack length,plate thickness,orthotropic parameters,etc.The longer the crack length or the smaller the plate thickness,the greater the stress intensity factor,and it is safer than the temperature rise in the field cooling magnetization process of pulsed magnetic field.The interface crack model between functionally graded superconductors and functionally graded materials is established.Considering the blocking effect of cracks on heat flow,it is assumed that there is thermal conductivity and thermal resistance in the crack region.The variation of temperature and stress intensity factor under different conditions are studied.The variation curves of temperature and stress intensity factor on crack surface and its extension line are obtained by Fourier transform method,Laplace numerical inversion method and Gauss-Chebysheve integral formula.The effects of different heat conduction parameters,thermal expansion parameters,hardness parameters,thermal resistance and the ratio of plate thickness on the temperature distribution and stress intensity factor are analyzed.The numerical results show that the stress intensity factor at the crack tip can be reduced and the crack propagation can be slowed down by selecting appropriate material parameters.In addition,the changes of stress intensity factor during different magnetization processes are analyzed.