A Study on Acoustic Emission due to Nucleation and Coalescence of a Microcrack in the Proximity of a Macrocrack
Naoki IKEDA, Noboru TAKANO, Ken-ichi HIRASHIMA@and Yukio HIROSE
Abstract:Accoustic emission (AE) due to microcracking process in the proximity of a macrocrack is theoretically studied. On the basis of some approximations,the Aewave from a crack-opening event is directly related to crack-opening volume as a function of time. It is assumed that two-dimensional cracks open spontaneously under a tensile stress applied at infinity, and that the crack volumes grow to the values of the static solution by a constant rate.The sources are approximated as points located at the center of the cracks. The two-dimensional Green's function for an unbounded medium is utilized in the analysis. It is shown that the interaction between a macrocrack and a microcrack generates additional crack-opening volume for both cracks, whose signals tend to be much larger than those that would emanate from nucleating a solitary microcrack, and the waveforms due to other models. Key Words:Acoustic Emission, Macrocrack with Microcrack, Model I Defomation, Green function