Page 142 - eBook_Proceedings of the International Conference on Digital Manufacturing V2

Proceedings of the International Conference on Digital Manufacturing –
Volume 2

Figure 57: Tap test evaluation of the Rochelle salt-based
piezoelectric device

Impact Hammer Method for Piezoelectric Characterisation

To evaluate how our piezoelectric device responds to forces, we
used the Impact Hammer Method—a widely used technique in
vibration analysis. It works by striking the device with a calibrated
hammer to deliver a controlled mechanical impulse. In the current
arrangement, every strike of a hammer generated a significant
voltage spike, which was observed on a digital oscilloscope. The
output of the device peaked at around 460 millivolts (mV), and
after each hit, we observed a sort of series of oscillations that
decay in the wave form (see Figure 58). Such patterns speak a lot
about the behaviour of the material in terms of its natural
resonance and how quickly it damps out vibrations, which are very
important indicators for piezoelectric performance.

The closest thing to real vibrational forces wouldn't be
available at the facility that uses this very effective technique. Our
sensor, made with Rochelle salt and using inexpensive conductive
materials, such as aluminium tape, made a very simple, cost-
effective condition. So, although it is quite simple, the device
detected impact events and transformed mechanical energy to
measure electrical signals, with a maximum output of 460 mV.

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