Effects Of Interfacial Continuity On The Fracture Behavior In Superconductor-substrate Structure Based On VCCT

With the rapid development and application of technology and products of thin film coatings,the mechanical properties of high-temperature superconducting thin film materials have drawn wide attention.The strength and service life of the superconductor-substrate composite structure generally depend on the interfacial behavior.The fracture failure mechanism at the interface directly affects the final behavior of the overall system under electromagnetic force.Therefore,it is of great significance to study the influence of interfacial continuity on superconductor-substrate structure for farbrication of high-performance superconducting thin films.In this paper,we will study the fracture behavior of the interfacial cracks of the inhomogenous high-temperature superconductor-substrate structure with different continuous interfaces in the process of field cooling and zero field cooling based on the virtual crack closure method(VCCT)in detail.The main works are following:1.For functionally graded materials,we have solved some classical problems of fracture based on VCCT.First,we calculated the influence of the inhomogeneity of material on the stress intensity factors of the two-dimensional plate with the boundary cracks and slanted central cracks.Second,we studied the influence of the inhomogeneity of elastic modulus on the stress intensity factors of bimaterial plate with the interface cracks and the internal cracks.In the end,we analyzed the problem of three-dimensional functionally graded plates with cracks and solved the distribution of stress intensity factors at the crack fronts.The numerical results show that the VCCT is simple,efficient and accurate in solving two-dimensional cracks and three-dimensional cracks;The inhomogeneity of the material has a great influence on the stress intensity factor of cracks,and the greater the inhomogeneity of coefficient,the greater the stress intensity factor is.2.Based on the Bean model,we have established magnetic-mechanical coupled model for inhomogenous high-temperature superconductor-substrate structure.Based on the continuity of the elastic modulus and its derivative at the interface,we introduced several different continuous interfaces.In the process of field cooling and zero field cooling,We studied the influence of the continuity of the interface and the inhomogeneity of coefficient of material on the stress intensity factor and crack opening displacement(COD)of the interface crack based on VCCT.The results show that the better the continuity of the superconductor-substrate structure,the smaller the stress intensity factor and the COD of the interface crack is,the stronger the ability to resist cracking is;The smaller the inhomogeneity of the coefficient of the superconductor-substrate structure material,the smaller the stress intensity factor of the interface cracks is,the greater the COD is.In this paper,we have studied the interface continuity problem of the inhomogenous high-temperature superconductor-substrate structure based on VCCT,which provides a theoretical basis and method for the study of interface cracks in inhomogenous high-temperature superconductors.It is of great significance to guide the farbrication of high-performance superconductor-substrate structure,and provides an important way to study the interfacial continuity of composite materials.