Crackling noise during failure of alumina under compression: effect of porosity

TL;DR

This study investigates acoustic emission during the failure of porous alumina under compression, revealing power-law energy distributions indicative of critical failure behavior across various porosities.

Contribution

It provides new insights into the statistical properties of acoustic emissions in porous alumina, highlighting the influence of porosity on failure dynamics and energy distribution.

Findings

Energy distributions follow a power law with an exponent around 1.8.

Broad energy distribution with a fat tail suggests critical failure behavior.

Power-law behavior observed over two decades in energy for certain porosities.

Abstract

We study the acoustic emission avalanches during the failure process of porous alumina samples (Al2O3) under compression. Specimens with different porosities ranging from 30% to 59% have been synthetized from a mixture of fine-grained alumina and graphite. The compressive strength as well as the characteristics of the acoustic activity have been determined. The statistical analysis of the recorded acoustic emission pulses reveals, for all porosities, a broad distribution of energies with a fat tail, compatible with the existence of an underlying critical point. In the region of 35%-55% porosity, the energy distributions of the acoustic emission signals are compatible with a power law behavior over two decades in energy with an exponent \epsilon = 1.8+/-0.1.