Cracks Detection by Electromagnetic Emission

Cracks Detection by Electromagnetic Emission

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The phenomenon of electromagnetic emission (EME) from solids is based on the generation of electromagnetic field resulting from mechanical excitation of the solid in question. This phenomenon may be induced by external pressure, bending or shear stress, knock, friction, etc. When mechanical stress is applied to a solid, there arise cracks and a redistribution of electric charge takes place. The crack faces are charged with opposite charges thus forming a time variable electric dipole or an electric double-layer. Hence they become sources of an electromagnetic field, which may be detected in the vicinity of the solid in question by means of appropriate sensors. 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 (AE) response and time delay corresponds to the difference of propagation velocities of sound and electromagnetic radiation in the sample. The practical application of this phenomenon is in the diagnostics of non-conducting materials and structures under mechanical stress, and, particularly, for registering the generation and evolution of micro-cracks and other defects in materials and their

The phenomenon of electromagnetic emission (EME) from solids is based on the generation of electromagnetic field resulting from mechanical excitation of the solid in question. This phenomenon may be induced by external pressure, bending or shear stress, knock, friction, etc. When mechanical stress is applied to a solid, there arise cracks and a redistribution of electric charge takes place. The crack faces are charged with opposite charges thus forming a time variable electric dipole or an electric double-layer. Hence they become sources of an electromagnetic field, which may be detected in the vicinity of the solid in question by means of appropriate sensors. 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 (AE) response and time delay corresponds to the difference of propagation velocities of sound and electromagnetic radiation in the sample. The practical application of this phenomenon is in the diagnostics of non-conducting materials and structures under mechanical stress, and, particularly, for registering the generation and evolution of micro-cracks and other defects in materials and their

Crack, electric charge, electromagnetic emission, acoustic emission

Crack, electric charge, electromagnetic emission, acoustic emission

KOKTAVÝ, P., PAVELKA, J.

01.01.2002

Ing. Zdeněk Novotný, CSc.

Brno

80-214-2180-0

Electronic Devices and Systems 02 - Proceedings, Experimental Methods in Acoustic and Electromagnetic Emission

82

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