Fracture analysis by use of acoustic emission

Abstract

This report contains results of acoustic emission studies on flawed and unflawed specimens of aluminum and beryllium. Acoustic emission from the flawed specimens is found to begin at stress levels far below the general yield stress. A theoretical model given here indicates that the total number of acoustic emission signals from a specimen containing a crack should be proportional to the fourth power of the stress intensity factor obtained from a sharp-crack fracture mechanics analysis. This is in disagreement with experimental data from single-edge-notched fracture toughness specimens of the two materials, which indicate that acoustic emission varies more like the sixth to eighth power of the stress intensity factor. An example is given to show how the acoustic emission data obtained on fracture toughness specimens can be used to nondestruetively test the fracture strength of an engineering structure.