Acoustic emission source characterization

TLDR: In this paper, the source function for glissile dislocation loops and microcracks has been modeled in terms of time dependent force dipoles and the acoustic emission waveforms, at the epicentre, evaluated for an isotropic elastic half-space.

Abstract: The source function for glissile dislocation loops and microcracks have been modeled in terms of time dependent force dipoles and the acoustic emission waveforms, at the epicentre, evaluated for an isotropic elastic half‐space. A specimen geometry has been designed that allows microcracking to occur under the influence of an applied stress but which also approximates to a half‐space for a short period of time after operation of an event. The epicentre waveforms of such a specimen have been measured, quantitatively, with a broad band capacitance transducer and the waveforms recorded by Biomation transient recorders and stored on computer disk. The inverse transfer function for the experimental configuration has been calculated and used to determine the source function of carefully characterized brittle cleavage and intergranular microcracking in mild steel and electrolytic iron at 77K. The microcrack lengths deduced from acoustic emission measurements were consistent with fractographic observations. The ve...