Acoustic and electromagnetic emissions related to stress-induced cracks

The mechanical behaviour of concrete and rocks samples loaded up to their failure is analyzed by Acoustic Emission (AE) and Electromagnetic Emission (EME). All specimens were tested in compression at a constant displacement rate and monitored by piezoelectric (PZT) transducers for AE data acquisition. Simultaneous investigation of magnetic activity was performed by a measuring device calibrated according to metrological requirements. In all the considered cases, the presence of AE events has been always observed during the damage process, whereas it is very interesting to note that the magnetic signals were generally observed only in correspondence of sharp stress drops or the final collapse.