Reliability Analysis Of Irreversible Tensile Strain And Shear Stress Intensity Of Bi-2223 Superconducting Tape

In the late 1980s,the phenomenon of superconductivity of copper oxide with a critical temperature of more than 77 K was found.This kind of superconducting material with a critical temperature of much more than Macmillan limit(40K)is called high temperature superconducting material.High temperature superconducting(HTS)materials have higher critical parameters than traditional low temperature superconducting materials,namely critical temperature,critical magnetic field and critical current density.Industrial superconducting wires made of high temperature superconducting materials have laid a foundation for the application of superconducting magnets,superconducting energy accumulators,superconducting motors and other fields of strong electricity,and have a very broad application prospect.At present,commercial high temperature superconducting wires are mainly Bi series superconducting tapes and REBCO superconducting tapes based on rare earth elements.First of all,superconducting tapes need to be wound into industrial magnetic coils or cables.Second,they usually serve in strong magnetic fields,low temperature environments,and need to transmit large engineering currents.Superconducting materials deform due to machining deformation,thermal stress and electromagnetic force.It has been found that the deformation of superconducting tape will cause the degradation of critical current.When the deformation exceeds a certain allowable limit,the material will be destroyed and the critical current will be permanently degenerated.This brings great security risks and mechanical challenges to the operation of power equipment based on high temperature superconducting strip.At present,in the force-electrical behavior research of Bi-2223 tape,the main focus is on the irreversible tensile strain limit,while the influence of cutting stress on the performance of superconducting tape is rarely studied.Secondly,since Bi-2223 is a brittle ceramic material,the measured irreversible tensile strain limit data are discrete,which is not convenient for engineering analysis and application.Based on the above two key scientific problems in this paper,the Bi-2223 superconducting tape in the axial tensile stress and shear stress under the action of critical current degradation behavior of the study,by means of characterization of pottery and porcelain rupture strength weibull distribution statistical analysis method is put forward three parameter weibull distribution function,and from the viewpoint of reliability function,through the adoption of reliability criterion to determine the same batch samples of irreversible tensile strain and irreversible shear strength,to provide a reference for the engineering design and application.The main work and achievements of this dissertation are as follows:Using laboratory to establish the platform of high temperature superconducting tape force-electric test tape for Bi-2223 to 77 k under tensile loading critical current test experiment,in order to obtain the critical current and the strain of each sample degradation curve,the critical current degradation of 5% as the criterion,it is concluded that the corresponding irreversible tensile strain,and then uses the three parameters of weibull distribution function of 32 groups of experimental data were statistically analyzed,by 99% reliability criterion for Bi-2223 tensile irreversible tensile strain of the statistical results,the results can be regarded as the effective value of engineering tensile irreversible strain of Bi-2223 tape in the same batch.Then,the in-plane shear test of Bi-2223 HTS tape was carried out by double notch tensile shear method.The critical current degradation behavior was found under shear action.The irreversible shear stress intensity was obtained by using 5% of critical current degradation as the criterion.On 26 groups of experimental data in irreversible shear stress intensity of normal distribution and statistical analysis of the three parameters of weibull distribution,by comparing the further determine the weibull distribution in shear stress intensity the applicability of the statistical analysis,and based on 99% reliability for irreversible shear stress value as irreversible shear stress intensity,the shear strength of the superconducting tape can be used as the same batch reference value of engineering application.