Research On Array Eddy Current Testing Technique Based On Field-circuit Coupling

Array eddy current testing technology rises rapidly in the end of the20th century.The advantages of other nondestructive testing technologies are blended into array eddycurrent testing technology to make it become the unique nondestructive testingtechnology. It is famous for its advantages such as detecting quickly large sheet metal andadapting to complex testing conditions. In most researches of array eddy currenttechnology, the problems such as coils mutual inductance have a great influence on testingresults. Based on coils mutual indectance and centring on quantification of crack defect,matrix array eddy current sensor is studied in this paper.Combining with the actual detecting conditions, eddy current field-circuit couplingtheory is blended into the study of array eddy current probe. The control equations andboundary conditions in midfield source area and vortex area of3D eddy current problemare inferred with the indirect anslysis A, A of finite analysis. Combining withKirchhoff’s law, the circuit equations that the coupling windingin coils meets in coilsdetection circuit are given. The field-circuit direct coupling model is established andprovides the theoretical support for the research of mutual inductance between coils.With the support of theories above, the double coils field-circuit coupling modelwithout crack defect is established in this paper. The influences on coils mutualinductance are studied by means of coil parameters and the inherent law between coilparameter and coils mutual inductance is revealed.Centring on quantification of crack defect, the optimized design research on matrixarray eddy current probe is proceeded. On basis of the research, the quantification ofdifferent directional cracks are proceeded by using different testing models. Paralleltesting model is sensitive to transverse crack, the method of assessing crack’s length anddepth is proposed by means of differential processing of the testing coil induced voltageand the method of assessing crack’s location is proposed by means of “”feature.Vertical testing model is sensitive to longitudinal crack. The information of crack lengthis not obvious and difficult to quantity, but a certain crack depth information is contained.Vertical testing model can be used as the crack quantitative auxiliary testing model. Studies show that field-circuit model can be adaptively used for research of coilsmutual inductance and colis mutual inductance can be used to proceed crack quantifitivetesting. The crack effective information such as length, depth and location can beextracted and assessed through data processing.