PSI - Issue 48

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G. Gusev et al. / Procedia Structural Integrity 48 (2023) 176–182 Gusev et al / StructuralIntegrity Procedia 00 (2019) 000 – 000

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Fig. 6 Fourier spectra for the signal at A7z in the time interval of 1 - 5 mS.

The results of numerical simulation allow us to estimate the spectrum energy in the frequency ranges of 4-5 kHz and 5-7 kHz for all variants of the vibration response. The analysis showed that the maximum value of the spectrum energy in the frequency range of 4-5 kHz is revealed for the case of the structure without a defect. Let's take, conditionally, its value as a unit and the values of the spectral energy for this frequency range in the case of the defect will be normalized relative to this value. It can be seen that as the crack depth increases up to a value equal to 100 mm, the energy decreases and its value is 76% of the maximum value (spectrum energy for the case without a defect in the frequency range of 4-5 kHz). A similar picture is observed for the frequency range of 5-7 kHz. For the case without defect, the spectrum energy was 91.6%, and for the maximum defect depth it was 77%. This can be clearly seen in Figure 6 with the Fourier images. In general, it is revealed that as the defect increases, the spectrum energy decreases significantly with respect to the baseline (defect-free) vibro-portrait. A similar picture of the evolution of the vibration response in the case of defect growth for point A7 is clearly visible in the wavelet images.

Fig. 7 Wavelet images of the vibration response signal for a structure with a crack of different depth Picture in pt. А7. The accele ration component along the OZ axis.