Damage and failure analysis of brittle materials by acoustic emission

Application of stress or changes in environmental conditions can cause a material such as concrete or rock to become damaged, thereby affecting the performance of the structure. Because damage processes produce microseismic events called acoustic emission (AE), the growth of damage and the onset of failure can be identified by monitoring AE. In particular, a probability density function of acoustic emission events was used to describe the development of damage. It was observed that more porous or cracked materials displayed a higher AE rate than less porous or cracked materials at the same percentage of the maximum stress prior to failure. This suggests that the AE technique may be applied to diagnose the level of damage in a brittle material and may be useful to select materials for certain applications. Also, the experimental results indicated that the average root-mean-square value from a number of AE signals could be used as a real-time monitoring tool to predict the onset of failure.