PSI - Issue 64

Emanuele Gandelli et al. / Procedia Structural Integrity 64 (2024) 685–692 Emanuele Gandelli / Structural Integrity Procedia 00 (2019) 000 – 000

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(a) first singular value lines (SVL1)

(b) virgin beam – fund. mode ( f 1 =32.01 Hz )

(c) damaged beam – fund. mode ( f 1,D =31.93 Hz )

Fig. 6. Results of ambient vibration records on beam-2 processed through FDD: (a) first singular value line (SVL1) in both virgin and damaged conditions; (b) detected mode shape in virgin condition at f 1 =32.01 Hz; (c) detected mode shape in the damaged condition at f 1,D =31.93 Hz.

Fig. 7. Hammer tests carried out on beam- 2: (a) accelerometers’ longitudinal arrangement; (b, c, d) Fourier spectra of beam -2 obtained at three different levels of precompression. 5. Conclusions In this paper, the Frequency Domain Decomposition (FDD) technique has been employed to detect, through ambient vibrations ’ analysis , early warning signs (such a variations in natural frequencies and/or mode shapes) related to the onset of structural damages in PCBs. Compared to previous similar studies, the novelty consisted in the