Electromagnetic and acoustic emission generated by the cracks creation in solids

Characterization of acoustic and electromagnetic emission sources

“…Both EME and AE signals are correlated and their amplitudes increase just before the sample rupture. This phenomenon was observed also by Mori et al [5] and in other experiments [6,7].…”

“…In our case, while using EME signals, the crack creation time can be determined accurately, provided that the EME signal to noise ratio is sufficiently high. This condition is not met for the EME signal given in figure 2, but as was shown in [4], all electric signals start at the same time in an ultra low noise measuring set-up. This time corresponds to the real crack creation moment.…”

“…The voltage V (t) is induced on electrodes or plates of capacitor sensors due to charged wall motion, and it is proportional to the product of the electric charge and its velocity. The induced voltage V (t) is described [4] by…”

“…The resultant EME signal is determined by the product of the exponential decay and the eigenfunctions of the crack wall vibration. According to the model presented in [4], the values of the amplitudes u i are inversely proportional to the frequency ω i . The quantity V a describes the crack dipole moment and its value increases when the crack width is growing.…”

“…Our model of EME generation, derived in [4], is based on the movement of charged crack faces. On the faces of a newly created crack, the electric charges constitute an electric dipole system and due to the crack wall vibration, an EME signal is detected with a frequency corresponding to the crack length.…”