Issue 38

G. S. Serovaev et alii, Frattura ed Integrità Strutturale, 38 (2016) 392-398; DOI: 10.3221/IGF-ESIS.38.48 397 m o F t Sin f t Sin f t ( ) (2 ) (2 )    where o m f f n 2  – modulation frequency, o f – central frequency. On the time interval T = 0.4 s. mode superposition transient analysis is performed. The result of this analysis is the component of acceleration a z registered at the node at the specified time period (step II). The received signal includes a set of steady-state oscillations of different frequencies, which is obtained by decomposition of the signal using the Fourier Transform (step III). Figure 6 : Algorithm of transient analysis Resonance peaks on the resulting graph correspond to the eigenfrequencies. Internal dissipation was not considered in the current study, therefore, the analysis of the amplitudes of the resonance peaks was not performed. By implementing this algorithm, and increasing the size of the defect at each step, it is possible to monitor changes in natural frequencies. Figure 7 : Shifts of natural frequencies in the contact model of delamination. The general nature of the frequency response to an increase of the damage size is similar to the models described above. We can see the lack of influence of damage on low frequencies and high frequency sensitivity to the defect of a small size.