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Nonlinear surrogate synthesis of the surface circular eddy current probes DOI:10.15199/48.2019.09.15

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The eddy current probes are widely used in nondestructive testing of materials and products. They are used to search for defects in continuity of conductive products, testing of electrical properties, geometrical dimensions, and the like. The surface eddy current probes (SECP), which are characterized by high sensitivity, are used in the testing of flat products, and in some cases in products with a curved surface. The uneven eddy current density distribution (ECD) Jcoil in the volume of the testing object (TO), which depends on the geometric, electrophysical parameters and the relative position of its exciting coil concerning the testing surface, is inherent to classical surface eddy current probes (SECP). In SECP ECD is maximal in the surface layer of the conductive object and decreases when the excitations of the coil are removed from the coils along the surface (Fig. 1 a) and in deeper layers it decreases according to the exponential law. That is, in the case of such heterogeneous distribution ECD, the mutual arareament of SECP relative to the TO influences significantly on the method sensitivity. To ensure the defects detection and the determination of their geometric parameters by means of eddy current flaw detection, it is important to ensure a homogeneous ECD distribution in the testing zone (Fig. 1a). The problem of SECP creation with homogeneous sensitivity arises, and, consequently, a homogeneous distribution ECD Jreference in the zone of the testing object. This problem can be solved within the framework of optimal parametric synthesis by definition of non-classical excitation system of SECP with corresponding parameters providing the necessary distribution of ECD for non-axial probe. Such excitation system is a set of consistently connected concentric circular sections in the form of coils of arbitrary radii located at the same height above the TO and switched on counter or consensually “across the field[...]

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