PSI - Issue 20

R.S. Akhmetkhanov / Procedia Structural Integrity 20 (2019) 218–221

221

4

R. S. Akhmetkhanov / Structural Integrity Procedia 00 (2019) 000 – 000

The most informative images on the standard deviation are the components fig.2c (StdDev = 38.6) and fig.3b (StdDev = 28.03). Fig. 3 presents the resulting thermogram image components. Areas with closed contours show local zones with an elevated temperature. They also show the size and orientation of these local areas.

Fig.3. The isolines (a-d) of the images of the components obtained by a multiple-scale wavelet decomposition of the main image of the thermogram.

The selected zones required additional studies of the composite material by the acoustic method of defectoscopy in order to identify defects at these sites. For this, the low-frequency acoustic defectoscope AD-701 was used, which is intended for the diagnosis of composite materials by the methods of acoustic diagnostics. The setting of the device AD-701 was carried out in the area where the structure of the thermogram was homogeneous. The studies carried out in these zones by the acoustic impedance method showed that at points 1 and 2 (Fig. 3c) and at point 3 (Fig. 3b) there is a heterogeneity of the material structure. The maximum amplitude values of the acoustic signal (impedance) showed that at these points they were increased 2-3 times as compared with the defect free areas. The heterogeneity of the thermal field in these places could arise due to the heterogeneity of the matrix and / or filler of the composite material. In other zones with local temperature irregularities, the amplitude of the diagnostic signal was slightly increased, but within the selected thresholds when tuning the acoustic flaw detector. The results obtained using a multiple-scale wavelet transform for images of thermal fields with active thermal control of a sample of a composite material allowed us to detect, in addition to material defects and heterogeneity of the composite material, that were tested using a low-frequency acoustic diagnostic method. Thus, the use of multiple-scale wavelet transform in the analysis of thermograms allows for better non destructive testing of composite materials. References GOST R 56511-2015, 2015. Nondestructive control. METHODS OF THERMAL SPECIES. General requirements. Standardinform, Moscow, pp. 9. (in Russian) GOST 536983-2009, 2010. Nondestructive control. Thermal methods. Terms and Definitions. Standardinform, Moscow, pp. 7. (in Russian)