The Analysis On The Coupling Of Mechanical And Superconducting Properties In Polycrystalline Nb₃Sn:From Micro-Scale To Meso-Scale

The Nb₃Sn superconducting material as the main components of Large Hadron Collider?LHC?,International Thermonuc lear Experimental Reactor?ITER?,High Energy Physics?HEP?and other superconducting magnet components has been widely studied.The strain-induced performance degradation of superconducting Nb₃Sn is a critical issue in the superconductivity?Critical temperature,Upper critical magnetic field,critical current density?engineering because of the significant role it plays in the Nb₃Sn materials application in the design and manufacture of magnets.The purpose of this paper is to start from the microscopical viewpoint of Nb₃Sn materials.On the basis of the Finite Element Analysis?FEA?,the tensor function representation theory,the Bhatt Model for the description of the density of states of Nb₃Sn and the critical temperature calculation model,The critical performance degradation model of Nb₃Sn and Finite element model of Nb₃Sn polycrystalline material was established.Study on the relationship with Nb₃Sn deformation and superconducting properties.The main research results of this paper are:?1?A unified model for characterizing the strain-induced modifications of the density of states at the Fermi surface as the Nb₃Sn single crystal undergoes diverse external loading modes is established.Based on the model and A semi-empirical model of upper critical magnetic field changing with strain obtained from WHH theory,an analysis model for the critical temperature of Nb₃Sn?Single crystal,polycrystal and composite superconductor?inc luding strain dependence is also presented,which can well describes the degradation characteristics of various testing load modes.?2?Polycrystalline structure of Nb₃Sn superconducting material is established by Neper?a software package for polycrystal generation and meshing?.Us ing Voronoi algorithm,generated a cube 3D model with 400 grains and the average grain s ize of the grain is 135nm.Us ing the Finite Element Analys is software ABAQUS to calculate the elastic response of grain interior and grain boundary in hydrostatic loading mode.Analyze the distribution of stress and strain under hydrostatic pressure.?3?Based on the coupled constitutive relation of the critical performance degradation and the finite element analysis of the elastic mechanical response of Nb₃Sn polycrystal under hydrostatic pressure.Using Python language to extract the result of FEA,and through the second-hand developments of the results,Analysis of the degradation rule of Nb₃Sn polycrystalline superconducting critical temperature under hydrostatic pressure.