PSI - Issue 5

H. Lopes et al. / Procedia Structural Integrity 5 (2017) 1205–1212 H. Lopes et al. / Structural Integrity Procedia 00 (2017) 000 – 000

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presented in the following figures are obtained by, respectively, computing the average of RMS and SNR of the three measurements in each group. Figure 6 shows the RMS of noise in the first four modal rotation fields as a function of the maximum vibration amplitude of the rotations. It is possible to observe a non-linear increase of the RMS of noise with the maximum amplitude of the rotations. If one considers the same maximum vibration amplitude of the rotations, we observe that the RMS of noise are higher for the first modal rotation field. On the other hand, the third modal rotation field presents the lowest RMS for values of the maximum vibration amplitude of the rotation greater than or equal 50.

Fig. 6. RMS of noise in the first four modal rotation fields as a function of the maximum vibration amplitude of the rotations.

The SNR of the first four modal rotations as a function of the maximum vibration amplitude of the rotations is presented in Figure 7. The plots in this figure show an almost linear relation for large values of the maximum vibration amplitude of the rotations. On the other hand, for small values one can observe a non-linear behavior. The best SNR, indicating a better relative accuracy, is obtained in the first modal rotation field.

Fig. 7. SNR of the first four modal rotation fields as a function of the maximum vibration amplitude of the rotations.