Investigations On Mechanical Behavior Of Superconducting Composites Based On Peridynamic Method

In the fields of energy,military,medical and scientific instruments,superconducting materials have a very broad application prospect.In the process of preparation and operation of superconducting materials,they undergo the prestress,electromagnetic force and thermal stress.Most superconducting materials are brittle materials,and they are easy to fracture under mechanical load,which can lead to the failure of superconducting composite wires.Thus,it is very important to study the fracture of filaments in superconducting composites.The peridynamic method is a meshless method based on spatial integral equation,which does not need to differentiate the displacement field,and has great advantages in solving discontinuous problems such as fracture.The peridynamic method is mostly used to study the fracture behavior of brittle materials,while superconducting composite wires consist of metal matrix and superconducting-filaments.The metal matrix has typical elastoplastic behavior.It is necessary to further extend peridynamic method to effectively analyze the complicated mechanical behaviors,such as elastoplastic deformation and filaments fracture.In this paper,the peridynamic model is used to characterize the plastic behavior,and simulate the crack propagation behavior of the superconducting composite wire under external load.Lastly,the peridynamic method is coupled with the finite element method to improve the computational efficiency.The main research contents are as follows:Firstly,this paper introduces the theory of peridynamic.And the material parameters for the peridynamic theory are obtained by comparing with the strain energy density of continuum mechanics.Two methods are introduced to solve the displacement,and peridynamic code is parallelized with Open MP.Secondly,the elastic-plastic behaviors of 2D and 3D structures are simulated by the ordinary state-based peridynamics.On the basis of deviatoric strain energy,the plane stress,plane strain and three-dimensional problems are also discussed respectively.The effect of strain along z-direction on the plane problem is mainly considered and the numerical results are compared with the finite element method.The simulated results of the Mises stresses and displacements obtained by peridynamics are in good agreement with the results of finite element method.By solving the plane strain and plane stress problems,the failure processes of high-temperature superconducting Bi2212 wire under compression and tension are also simulated.Finally,in order to improve the computational efficiency,the finite element method based on local theory is coupled with the peridynamic method based on nonlocal theory,which can eliminate the boundary effects caused by nonlocal effects and it is more convenient to impose the boundary conditions.The structure is divided to establish the finite element region,peridynamic region and coupling region.The dynamic relaxation method is used to solve the displacement,and the elastic-plastic analysis of the coupled method is realized.