01-03-2017, 02:41 PM
As mentioned earlier, it has been suggested in the past
that single-mode tuning should be used for improving
the effectiveness of the time-reversal-based technique
for damage detection (Xu and Giurgiutiu, 2007b). In
order to study this aspect, we determined the sweet spot
frequencies of the actuator–plate–sensor system
(Figure 8) for exciting the S0 mode, and examined the
effect of the thickness and length of the PZT on the
same. The S0 mode is chosen as it has been found to be
more sensitive to transverse crack-like defects due to
the inplane motion (Ihn and Chang, 2008). From the
pin-force model solution described earlier, the sweet
spot frequencies f ss
for the S0 mode are obtained as
135.48 kHz and 414.95 kHz, for transducer lengths of
10 mm and 5 mm, respectively. However, this solution
does not account for the interaction between the actuator/
sensor and the plate, and hence is not affected by
the transducer thickness. The sweet spot frequency considering
this interaction is obtained from the FE analysis,
by plotting the ratio of the peak amplitudes of the
S0 and A0 modes as a function of the central excitation
frequency. The peak amplitudes of the S0 and A0 modes
have been obtained by forming an envelope of the sensor
output, using the Hilbert transform. Figure 10
i need Hilbert transform plot.please send me some link.i tried lot of codes.
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