Issue 49

D. Oshmarin et alii, Frattura ed Integrità Strutturale, 49 (2019) 800-813; DOI: 10.3221/IGF-ESIS.49.13 807 1). However, when compared to other frequencies (see Tab. 2), the damping indices for these pairs of modes appear to be sufficiently higher. а b c d Figure 3 : Relationship surfaces of damping indices depending on R and L parameters and projections of the lines of their coincidence for 4th and 5th frequencies (a, b) and 12th and 15th frequencies (c, d). Continuing the analysis of relationship surfaces presented in Fig. 2, one might see that in the R-L parameters space there are points where imaginary parts of complex eigenfrequencies coincide for more than two frequencies. Fig. 4 shows the projections of all possible lines of Im  coincidence for which such points were found. These points correspond to shunt circuit parameters at which it is possible to damp vibrations on three frequencies. These points are labelled with roman numbers: I – 4th, 5th and 12th modes; II – 5th, 12th and 15th modes; III – 1st, 12th and 15th modes; IV – 4th, 5th and 15th modes. According to the results that correspond to the point III on fig.4 and presented in Tab. 3, the efficiency of damping of vibrations with the aid of one and the same technical devices for 1st, 12th and 15th frequencies is quite low. This is