PSI - Issue 44

Hasan Borke Birgin et al. / Procedia Structural Integrity 44 (2023) 1624–1631 Hasan Borke Birgin et al. / Structural Integrity Procedia 00 (2022) 000–000

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5. Results

Important results were obtained through the dynamic tests conducted on full-scale beams. Figure 4 presents the raw resistance readings and the time-frequency analysis of the recorded signals. The hammer hits, in this case, were consecutively placed in zones 1-2-3-4-5 (Fig. 3(a)), and the sequence was repeated four times, for a total of 20 hits. Inspecting the resistance readings, the hammer impacts are clearly visible and generate dynamic responses. The segments between electrodes 1-2 and 2-3 generated a better signal response, while the poor performance due to the high noise-to-signal ratio of the segment between electrodes 3-4 might be related to material non-uniformities or local conductivity issues. As expected, due to the use of DC Voltage, a polarization drift is visible in the outputs from segments shown in Figs. 4(a) and (b). The drift observed in Fig. 4(c) is not as significant as the others, since the polarization of other segments is stronger. Inspecting the frequency-time analysis, the beam vibration caused by hammer hits was around 65 Hz.

Fig. 4. Dynamic test results of the smart material beam with hammer hits located on different zones on the beam, raw reading, and frequency time analysis: (a) segment between the electrodes 1-2, (b) segment between the electrodes 2-3, (c) segment between the electrodes 3-4.