AE sources characterization by electromagnetic and acoustic emission

AE sources characterization by electromagnetic and acoustic emission

Paper in proceedings (conference paper)

Generation of crack is accompanied by generation of electric charges on the crack walls. This charge can be measured by a capacitance antenna. When a micro-crack is generated in a solid the faces of the crack make up plates of an elementary capacitor and the charges located on them constitute an electric dipole or quadrupole. The magnitude of the electric charge configuration depends on the time. Experimentally we have observed two different type of signals like damped harmonic motion with: (i) exponentially time dependent transient value and (ii) constant average value. we suppose that first one is generated by dipole structure and second one is generated by quadrupole. Using Shockley-Ramo theorem, the differential equation for induced voltage is derived. We found that voltage on measuring capacitor is directly proportional to the electric charge distribution. The recorded electric signal is superposition of crack walls "self" vibration given by crack length and vibration due to an ultrasonic wave given by sample dimensions. The electromagnetic signal precedes the acoustic emission response and time delay corresponds to the difference of propagation velocities of sound and electromagnetic field in the sample. Electromagnetic phenomena which are generated in stressed solids can be used to indicate cracks creation kinetics in solids.

Generation of crack is accompanied by generation of electric charges on the crack walls. This charge can be measured by a capacitance antenna. When a micro-crack is generated in a solid the faces of the crack make up plates of an elementary capacitor and the charges located on them constitute an electric dipole or quadrupole. The magnitude of the electric charge configuration depends on the time. Experimentally we have observed two different type of signals like damped harmonic motion with: (i) exponentially time dependent transient value and (ii) constant average value. we suppose that first one is generated by dipole structure and second one is generated by quadrupole. Using Shockley-Ramo theorem, the differential equation for induced voltage is derived. We found that voltage on measuring capacitor is directly proportional to the electric charge distribution. The recorded electric signal is superposition of crack walls "self" vibration given by crack length and vibration due to an ultrasonic wave given by sample dimensions. The electromagnetic signal precedes the acoustic emission response and time delay corresponds to the difference of propagation velocities of sound and electromagnetic field in the sample. Electromagnetic phenomena which are generated in stressed solids can be used to indicate cracks creation kinetics in solids.

non-destructive testing, ultrasonic methods, non-linear ultrasonic spectroscopy, acoustic emission, electromagnetic emission, crack, granite

non-destructive testing, ultrasonic methods, non-linear ultrasonic spectroscopy, acoustic emission, electromagnetic emission, crack, granite

KOKTAVÝ, P.; ŠIKULA, J.; KOKTAVÝ, B.; LOKAJÍČEK, T.

15.11.2007

Z. Novotný, Ing., CSc.

Brno

978-80-7355-078-3

New trends in physics

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