Comparison between experimental results, analytical predictions, and finite element simulations (Fig. 3.11) shows good agreement for SH-PWAS orientation-2 that generates SH deformation in the structure. It is noticed that the impedance peaks are multiples of 30 kHz. The third peak of 95 kHz shows the best match between experiments and simulations. Also the experimental measurement at 145 kHz shows agreement with 3-D FEM, however this peak is not captured by the analytical prediction. Referring to modeshapes (Fig. 3.10d), it is noticed that the 5th mode of vibration is more or less local mode and it drives the beam into some sort of torsional vibration. The 4th mode starts not to be uniform SH deformation; it may contain coupled modes of vibration. Fig. 3.9 Modeshapes of vibrations of 3-mm thick steel beams with bonded SH-PWAS in orientation-1 (axial–flexural orientation), at excitation frequency: (a) 48 kHz, (b) 137 kHz, and (c) 145 kHz Fig. 3.10 Modeshapes of vibrations of 3-mm thick steel beam with bonded SH-PWAS in orientation-2 (SH orientation) at excitation frequency: (a) 30 kHz, (b) 60 kHz, (c) 90 kHz, (d) 123 kHz, and (e) 146 kHz Fig. 3.11 Comparison between experimental results, analytical predictions, and finite element simulations for E/M impedance of SH-PWAS bonded on 3-mm thick steel beam (orientation-2) 3 Characterization of Shear Horizontal-Piezoelectric Wafer Active Sensor (SH-PWAS) 25
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