The Research Of Correlational Problem In SQUID NDE

superconducting quantum interference devices (SQUIDs) as magnetic field sensors for NDET(Non-destructive electromagnetic testing) have revealed their advantages in very high field sensitivity, wide bandwidth, broad dynamic range and excellent linearity. Especially, it has been recognized that their extremely high sensitivity makes them very suitable for the detection of deep flaws. In recent years, research on SQUID NDE (Non-destructive evaluation) has made rapid progress, which is the foundation of this method used in industryIn this paper,The correlative problems of SQUID NDE are studied, include analyzing step-edge junction Josephson effect, constructing emulational model of metal defect, discussing correlative factors of spatial resolution, improving program of Fourier filter.the physics model of step-edge junction is constructed and its Josephson effect is analysed . The relation between zero-voltage current and coupling coefficient is given, in the meantime by numerical calculation, the phase difference relations between two weak links are also briefly discussed.the emulational model of crack on metal surface is constructed by ANSYS. The information of defect, such as length, depth and width, is analyzed by combining magnetism-current inversion with alternating current field measurement method. And then, the interrelated factor of spatial resolution are discussed briefly. the inverse results are compared with that of emulational model of crack in metal at last. By analyzing the simulation of alternating current field measurement to crack on metal surface, it is found that the result is more precise in showing the length of the crack on metal surface by magnetic field and distribution of current.We improve and figure every step of electromagnetic inversion, and complete a good user interface. The improved procedures adding digital filter function can filtering the designated cutoff frequency , and we validate the result briefly.