The importance of eddy current measurements of specific electrical conductivity (SEC) of materials in non-destructive testing for solving problems of structuroscopy is discussed. In particular, their significant role is shown for estimation of the degree of changes in the mechanical characteristics of structural materials due to degradation processes in their structure. The influence of the temperature of metallic structural materials on the results of eddy current measuring of SEC has been studied. An analytical expression for the output signal of the SEC measuring channel of an electrical eddy current conductivity meter for real temperature of material is obtained. It depends on the value of the material SEC at a nominal temperature value (usually 20 C), temperature coefficient of electrical resistance of the material and the deviation of the material real temperature from the nominal value. It is shown that in order to tune out this effect and bring the measurement results to the nominal temperature, it is necessary to use eddy current meters with an additional channel for measuring the material temperature in the testing zone. The output signal of this channel is used to correct the SEC measurement results. This is carried out by multiplying the output signal of the SEC measurement channel and some auxiliary signal. This auxiliary signal is generated from the output signal of the temperature measurement channel by it scaling and summation with the signal of the direct current voltage reference source. A functional diagram of the eddy current SEC meter with temperature correction is proposed. A detailed description of it operation is given. In the absence of preliminary information about the grade of material and the value of its temperature coefficient of electrical resistance, is proposed to suppress the influence of temperature by test changes in the temperature of the material in the testing zone. At the same time, it is necessary to adjust the gain of the scale converter. This is done until the readings of the eddy current SEC meter do not depend on the material temperature in the testing zone.

1. Rummel, W.D. Characterization and evaluation of 2014 aluminum alloy by eddy current conductivity techniques. Materials Evaluation. 1966, 14(6), 322-326.

2. Dorofeev, A.L. Induction structuroscopy; Energiya: Moscow, 1973, 176. (in Russian)

3. Naumov, N.M.; Miklyaev, P.G. Resistivity-metering nondestructive testing of aluminium wrought alloys; Metallurgiya: Moscow, 1974. (in Russian) 4. Dorofeev, A.L.; Kazamanov, Yu.G. Electromagnetic flaw detection; Mashinostroenie: Moscow, 1980. (in Russian)

5. Dorofeev, A.L.; Ershov, R.E. Physical fundamentals of electromagnetic structuroscopy; Khlebopros, R.G., Ed.; Nauka. Sibirskoye otdeleniye: Novosibirsk, 1985. (in Russian)

6. Nondestructive testing handbook, 2nd ed. Vol. 4: Electromagnetic testing (Eddy current, flux leakage and microwave nondestructive testing), McMaster, R.C.; McIntire, P.; Mester M.L., Eds.; American Society for NDT: USA, 1986.

7. Bakunov, A.S. Evolution of equipment for eddy current structuroscopy of non-ferrous metals in Russia. Kontrol. Diagnostika. 2004, 4, 63-64. (in Russian)

8. Dobmann, G.; Boller, Ch.; Herrmann, H.-G.; Altpeter, I. Micromagnetic and electromagnetic NDT for lifetime management by monitoring ageing of structural materials. Int. J. Microstructure and Materials Properties. 2014, 9, 348-359. https://doi.org/10.1504/IJMMP.2014.066915

9. NDT methods for monitoring degradation. Proc. of the Joint EC-IAEA Specislists Meeting, Petten, The Netherlands, March 10-12, 1999; Estorff, U.; Davies, L.M.; Trampus, P., Eds.; Luxemburg, 1999.

10. Ostash Î.P.; Fedirko, V.M.; Uchanin, V.M.; Bychkov, S.A.; Molyar, O.H.; Semenets, O.I.; Kravets, V.S.; Derecha, V.Ya. Strength and durability of aircraft materials and structural elements. In Fracture Mechanics and Strength of Materials: A Handbook. Vol. 9; Panasyuk, V.V., Ed.; Spolom, Lviv, 2007.

11. Ostash, O.P.; Andreiko, I.M.; Holovatyuk, Y.V. Degradation of materials and fatigue durability of aircraft constructions after long-term operation. Materials Science. 2006, 42(4), 427-439. https://doi.org/10.1007/s11003-006-0098-1

12. Nesterenko, G.I.; Basov, V.N.; Nesterenko, B.G.; Petrusenko, V.G. The influence of long-term operation of aircraft on the properties of materials of their structures. Problemy mashinostroyeniya i nadezhnost' mashin. 2006, 4, 41-50. (in Russian)

13. Ostash, O.P.; Kiva, D.S.; Uchanin, V.M.; Semenets O.I.; Andreiko I.M.; Golovatyuk Yu.V. Diagnostics of technical condition of aircraft structures after longterm service. Tekhnicheskaya Diagnostika i Nerazrushayushchiy Kontrol'. 2013, 2, 15-22. (in Ukrainian)

14. Ostash, O.P.; Andreiko, I.M.; Markashova, L.I. et al. Influence of long-term operation on the structure and physicomechanical properties of D16- and V95-type aluminum alloys, Materials Science, 2013, 49(1), 13-24. https://doi.org/10.1007/s11003-013-9578-2

15. Ostash, O.; Uchanin, V.; Semenets, O.; Holovatyuk, Y.; Kovalchuk, L.; Derecha, V. Evaluation of aluminium alloys degradation in aging aircraft. Reseach in Nondestructive Evaluation. 2018, 29(3), 156-166. https://doi.org/10.1080/09349847.2017.1302622

16. Klyuev, V.V., Ed. Instruments for non-destructive testing of materials and products: A Handbook; Mashinostroenie: Moscow, 1986. (in Russian) 17. Gerasimov, V.G.; Pokrovskiy, A.D.; Sukhorukov, V.V. Electromagnetic testing: Practical manual; Sukhorukov, V.V., Ed.; Nondestructive Testing. In 5 books. Book 3; Vysshaya shkola: Moscow, 1992. (in Russian)

18. Uchanin, V.N.; Makarov, G.N. Suppression of lift-off influence in contactless measurement of specific electrical conductivity by eddy current method. Tekhnicheskaya Diagnostika i Nerazrushayushchiy Kontrol'. 1996, 4, 41-45. (in Russian)

19. Shvetskiy, B.I. Electronic digital devices; Tekhnika: Kyiv, 1991. (in Russian)

20. Kalashnikov, S.G. Electricity: Tutorial; Nauka: Moscow, 1985. (in Russian)

21. Bakunov, A.S.; Muzhitskiy, V.F.; Shubochkin, S.E. Eddy current structuroscope BE-26NP. In Metody i sredstva nerazrushayushchego kontrolya i tekhnicheskoy diagnostiki, Proceedings of the 1-st National Scientific and Technical Conference and Exhibition. October 21-24, 2003; Chisinau, Moldova, 2003, 109-110. (in Russian)