The apparatus we used includes: an SGI Indy multimedia
workstation (1) with dual-channel audio sampling
capability; a Tektronics 2232 dual-channel digital sampling
oscilloscope (2); a small hammer with various material
and head weights, inside each of which we can mount
a Kristler 811AD accelerometer (3); microphones (5); and
Kynar piezoelectric film (4) (Atochem North America’s
PVDF) for detecting vibrations transmitted through the
sample material surface.
The Tektronics 2232 dual-channel oscilloscope has the
capability of simultaneously storing and displaying signals
with proper single-sweep trigger control. We mainly used
this feature to study force-time history curve profile shape
variations.
Trying to better understand different aspects of the
coin-tap process, we experimentally compared steel versus
plastic hammers’ behaviors, as well as piezoelectric film
and accelerometer data. The scope of this paper is
restricted to results using a plastic hammer (30 gram) to
tap on an airplane skin.