MEASUREMENTS OF THE PIEZOELECTRIC EFFECT OF IMPACT LOADED ROCK BARS

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.