R. Hecker et P. Leistner, MEASUREMENTS OF THE PIEZOELECTRIC EFFECT OF IMPACT LOADED ROCK BARS, Materialwissenschaft und Werkstofftechnik, 25(11), 1994, pp. 425-430
The piezoelectric effect, which causes electric charge at the surface
of impact loaded rock bars, is shown by measurements using electrodes.
Moreover, electric field of this charge leads to measuring with anten
na. The one-dimensional theory of elastic waves in bars is the theoret
ical basis of computation. The comparison of all the experimentally an
d numerically determined data has proven a good agreement of typical f
eatures of mechanical waves measured by used methods. The electric cha
rge and the antenna signal are measurable on the front surface and on
the lateral surfaces of samples. For using latter measuring points nee
ds a certain relation between wave length and sensor length. With resp
ect to material of used granite samples the essential requirements are
piezoelectrically active rocks. These properties don't depend on quar
tz content alone. So the piezoelectric effect enables to measure mecha
nical stress waves by transducer (antenna) which is not physically in
contact with the appropriated rock sample.