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The possibility of copper ore quality testing for proportion of minerals containing copper in it by the eddy current method has been studied. Copper ore is presented as a low-conductivity heterogeneous medium consisting of two homogeneous ore constituents (enclosing rock and copper mineral). These constituents have significantly different specific electrical conductivity (SEC). For the analysis, the effective medium approximation is used. In this case a heterogeneous ore can be considered homogeneous with an effective SEC, which depends on the quantitative composition of its constituents. To solve this problem, the surface parametric eddy current probe (ECP) of a local type has been developed. Its design is optimized for operation at high frequencies (units – tens of MHz). ECP winding consists of 10 turns with a diameter of 11 mm, which wound up in one layer on a dielectric frame. The ECP signals in the complex plane from samples of copper ore with different content of copper mineral (chalcopyrite) in the resonant operation mode are studied using eddy current flaw detector of Eddycon C type. The operating frequencies are 5, 7 and 9 MHz. It has been established that with increasing frequency in the specified range, signals amplitude has a pronounced tendency to decrease. It is shown that as the frequency increases from 5 to 7 MHz, the phase sensitivity of the developed ECP to the content of chalcopyrite in the ore also decreases. Thus, the phase angle between signals from ore samples with low and high chalcopyrite content at the frequency of 5 MHz is 110°, and at the frequency of 7 MHz – 87.5°. With a further frequency increase to 9 MHz, the phase sensitivity remains practically unchanged, and the amplitude of the signals continues to decrease. This can be explained by a decrease of the ECP sensitivity to SEC changes with a transition to the over-extreme operating point of the complex plane by operating frequency increase. The fundamental possibility of using the eddy current method for the quantitative testing of chalcopyrite in copper ore has been confirmed. Prospects for further research related to the development of an integral-type ECP, in particular, screen ones, whose signals are determined by the content of chalcopyrite in copper ore samples as a whole, are formulated.

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Peculiarities of the coercive force (CF) measuring of inhomogeneous ferromagnetic materials, in particular layered ones, are considered. The concept of effective CF of layered ferromagnetic materials is introduced. The analysis of the magnetic fluxes distribution in a double layer ferro-magnetic material during its reversal magnetization by an attachable transducer with a U-shaped core made of soft magnetic material is carried out. An analytical expression of the effective CF for such class of materials for the case of the same layers’ thickness and linear approximation of their demagnetization curves is obtained. It was found that the effective CF of a double layer ferromagnetic material is determined not only by the CF of its individual layers, but also by the values of their residual induction. Experimental verification of the obtained results was performed on experimental samples, which were collected from steel 08kp (sample # 1) and steel St3 (sample # 2) plates. Each of the samples was a stack of 6 plates each measuring 87×50×1 mm. With tight compression of the plates and complete elimination of the gaps between them, these samples can be considered as single layer ferromagnetic structures with a thickness of 6 mm. To model a double layer ferromagnetic material with the same layer thickness, sample № 3 was used. Its the upper part consisted of the three steel 08kp plates and the lower part – of the three steel St3 plates. To measure the magnetic parameters of these samples the KRM-Ts-MA type magnetic analyzer was used. The device permit to measure the CF, residual induction and other parameters of the hysteresis loops of ferromagnetic materials in the closed magnetic circuit by attachable type transducers with U-shaped core. The transducer used with the magnetic analyzer during the experiments had poles with an area of 16×32 mm and the distance between the edges of the poles: inner – 32 mm, outer – 64 mm. It is shown that the discrepancy between the calculated value of the effective CF of the double layer ferromagnetic material (sample # 3) from steel 08kp and St3 according to the obtained expression and the measurement results is about 3%. This confirms the adequacy of the proposed model of reversal magnetization of double layer ferromagnetic material and the correctness of analytical calculations.