PSI - Issue 52

Carlos A. Galán Pinilla et al. / Procedia Structural Integrity 52 (2024) 20–27 Carlos A. Gala´n-Pinilla et al. / Structural Integrity Procedia 00 (2023) 000–000

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values, similar to the results reported by Mehrabi et al. (2022). Additionally, the fundamental mode S 0 has a cut-o ff frequency absent in the free plate case. Thus, the coating in the plate indistinctly increases the cut-o ff frequency for each mode with the exception of the A 0 mode. Fig 2(c) compares the group velocity for the coated plate (black line) and the free plate (green line), showing, for the case of coating, a tendency to reduce di ff erences in the group velocity among the di ff erent wave modes. This trend makes it di ffi cult to identify the di ff erent wave modes at the experimental level accurately. The behavior obtained for the group velocity in the present work agrees with the results reported experimentally by Mehrabi et al. (2022). In those measurements, the group velocity of the di ff erent modes was compared, finding a decrease in their values for a specific launching frequency due to the e ff ect of the coating. These results suggest that the coating absorbs Lamb wave energy and reduces the propagation velocity.

b )

a )

c )

d )

Fig. 2. Comparison of dispersion curves: a ) Wavenumber, b ) Phased velocity, c ) Group velocity, d ) Attenuation.

Fig. 2(d) shows the attenuation dispersion curve for the coated plate where the attenuation starts above 300 kHz , as reported by Hua and Rose (2010). For frequencies above the cuto ff frequency, a persistent decaying is observed with the exception of the S 0 mode with a maximum value of 2 . 5( dB / m ). With respect to the figure 2(b), the S 0 mode exhibits large frequency ranges without dispersion and no cut-o ff frequency. In the literature, Ono (2022), higher values of attenuation (in some cases of one order of magnitude) for the viscoelastic materials are reported compared to those obtained in the study case (coated plate). In addition to the above, in Fig 3, the amplitude of the displacement