Kinematic Identification of Internal Cracks by SiGMA Inversion Technique of Acoustic Emission

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Title: Kinematic Identification of Internal Cracks by SiGMA Inversion Technique of Acoustic Emission

Author(s): M. Ohtsu, M. Shigeishi, T. Okamoto, and S. Yuyama

Publication: Special Publication

Volume: 168

Issue:

Appears on pages(s): 95-110

Keywords: concretes; cracking (fracturing); nondestructive tests

Date: 4/1/1997

Abstract:
Acoustic emission (AE) has the potential to be an effective tool in evaluation of concrete structures under the action of loads causing cracking. In conventional testing, several AE parameters are investigated to elucidate microfracturing behavior in concrete. To identify internal cracks, the AE location technique is available, which is based on measuring arrival time differences. By employing multi-channel AE observations, the location of a crack responsible for an AE source can be determined. To obtain quantitative information on crack kinematics, the procedure is further studied and a technique for kinematic characteristics of internal cracks is developed. The AE source is mathematically represented by a moment tensor, by which the classification of cracks into tensile and shear cracks and the determination of crack directions can be made. To implement the procedure into a conventional AE system, software named SiGMA (Amplified Green’s function for moment tensor malysis) has been developed. The analysis is readily available on an AE waveform analyzer system consisting of a digital waveform-recorder and a microcomputer (controller). The procedure is applied to a uniaxial compression test of a plate specimen with a through-thickness slit and to a tensile test of a reinforced concrete rigid frame. The crack locations, the classification of crack types, and the determination of the directions of crack motion are in good agreement with experimental findings. The results show the procedure certainly provides a new technique for kinematic identification of internal cracks.