Waveforms and frequency spectra of elastic emissions due to macrofractures in solids

Abstract

This paper investigates the waveforms and frequency spectra of elastic emissions (ELE), or quasi-rigid body vibration pulses, due to the formation of macrofractures in perfectly brittle, quasi-brittle and ductile materials subjected to uniaxial compression. Elastic emissions, differently from acoustic emissions, are detected in a low frequency range (i.e. below 15-10 kHz) and are characterized by high levels of released energy. Approaching to the large fractures and the final collapse of the material bursts of ELE are observed indicating the solid elastic-mechanical properties degradation and its irreversible plastic deformation. Through waveform and time-frequency analysis of the ELE spectra, measured by calibrated transducers, it is possible to provide quantitative information on the damage evolution and the strain energy released during each ELE event.