16 April 2013 Acoustic emission signatures of damage modes in structural materials
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Abstract
The prediction of the remaining life of a structure can be assisted by the characterization of the current cracking mode. Usually tensile phenomena precede shear fracture. Due to the different movement of the crack sides according to the dominant mode, the emitted elastic energy possesses waveforms with different characteristics. These are captured by acoustic emission sensors and analyzed for their frequency content and waveform parameters. In this study fracture experiments on structural materials are conducted. The goal is to check the typical acoustic signals emitted by different modes as well as to estimate the effect of microstructure in the emitted wave as it propagates from the source to the receivers. The dominant fracture mode is controlled by modification of the setup and acoustic emission is monitored by two sensors at fixed locations. Signals belonging to tensile events acquire higher frequency and shorter duration than shear ones. The influence of heterogeneity is also obvious since waveforms of the same source event acquired at different distances exhibit shifted characteristics due to damping and scattering. The materials tested were cement mortar, as a material with microstructure, and granite as representative of more homogeneous materials. Results show that in most cases, AE leads to characterization of the dominant fracture mode using a simple analysis of few AE descriptors. This offers the potential for in-situ application provided that care is taken for the distortion of the signal, which increases with the propagation distance and can seriously mask the results in an actual case.
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D. G. Aggelis, A. C. Mpalaskas, T. E. Matikas, D. Van Hemelrijck, "Acoustic emission signatures of damage modes in structural materials", Proc. SPIE 8694, Nondestructive Characterization for Composite Materials, Aerospace Engineering, Civil Infrastructure, and Homeland Security 2013, 86940T (16 April 2013); doi: 10.1117/12.2008942; https://doi.org/10.1117/12.2008942
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