Technical Diagnostics and Non-Destructive Testing, 2022, №04



2022 №04 (03)

DOI of Article 10.37434/tdnk2022.04.04

2022 №04 (05)

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Technical Diagnostics and Non-Destructive Testing #4, 2022, pp. 27-32

Reducing the level of interference at thermal non-destructive testing considering the specific thermal physical and morphological characteristics of the object

V.O. Storozhenko, S.M. Meshkov, R.P. Orel, O.V. Miahkyi

RTC «Thermocontrol» of Kharkiv National University of Radio Electronics. 14 Nauky Ave., 61166, Kharkiv, Ukraine. E-mail: volodymyr.storozhenko@nure.ua

Interferences, characteristic for non-destructive thermal testing which reduce the reliability of the results obtained are described. A technique for their reduction is suggested which consists of two interrelated stages. The fi rst stage consists in calculating and analyzing the nature and level of the expected signal according to the developed thermophysical model against the background of the experimentally obtained noise level. According to the results of analysis of calculations using the thermophysical model for the selected samples, the most infl uential interference was the inhomogeneity of the emissivity of the sample surface. The second stage of processing the received data is devoted to reducing this noise. This stage consists in processing of thermograms of temperature fi elds and includes morphological analysis of the surface condition, fi ltering and reducing characteristic noise and interference. It consists of four practical procedures: analysis of the visual image and obtaining a map of zones with diff erent emissivity of the sample surface, analysis of the thermogram with an assessment of the level of discreteness of the thermogram and the position of fi ducial points on the image, smoothing the thermographic image and highlighting zones on the thermogram with diff erent emissivity of the controlled object surface, after which the noise is fi ltered. Since the results of thermal control are strongly infl uenced by the shape of the object, the possibilities and eff ectiveness of the suggested technique are illustrated on a cylindrical object. It has been experimentally confi rmed that for the selected sample, it was possible to reduce the noise level to that of confi dent separation of useful signal against the noise background. Ref. 10, Fig. 5.
Keywords: thermal non-destructive testing, useful signal level, structural noise, thermophysical model, image processing, morphological analysis

Received: 29.08.2022

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