A Model for an Electromagnetic Emission Signal Generated by Crack Creation

A Model for an Electromagnetic Emission Signal Generated by Crack Creation

Paper in proceedings (conference paper)

When a stress is applied to the solids (rocks or tiles) cracks creation can be detected by signals of an acoustic and electromagnetic emission. The experimental study has been performed on rock samples. Two metallic layers have covered the tested devices to create metal-insulator-metal structure. During the process of the crack generation the electric charges appeared at the faces of the cracks. The electric dipole system is a source of voltage induced on metal electrodes. Using Shockley-Ramo theorem, the differential equation for induced voltage is derived. We found that voltage on measuring capacitor is directly proportional to the dipole width and its active area. 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 radiation in the sample. The simultaneous investigation of acoustic and electromagnetic emission signals enable us to localise the crack position in solids.

When a stress is applied to the solids (rocks or tiles) cracks creation can be detected by signals of an acoustic and electromagnetic emission. The experimental study has been performed on rock samples. Two metallic layers have covered the tested devices to create metal-insulator-metal structure. During the process of the crack generation the electric charges appeared at the faces of the cracks. The electric dipole system is a source of voltage induced on metal electrodes. Using Shockley-Ramo theorem, the differential equation for induced voltage is derived. We found that voltage on measuring capacitor is directly proportional to the dipole width and its active area. 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 radiation in the sample. The simultaneous investigation of acoustic and electromagnetic emission signals enable us to localise the crack position in solids.

MIM system, Crack, Electromagnetic emission, Acoustic emission

KOKTAVÝ, P., ŠIKULA, J., KOKTAVÝ, B.

20.06.2001

Czech Society for Non-Destructive Testing, German Society for Non-Destructive Testing

Praha

80-238-7263-X

Proceedings of NDT in Progress

283

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