An acoustic emission digital data acquisition workstation

A digital acoustic emission (AE) data acquisition system has been used to record the acoustic emissions generated by individual crack initiation sites during fracture. The purpose of this research is to analyze the dynamics of crack growth and to discriminate among fracture mechanisms through pattern analysis of the received signals. Preliminary experiments were performed using a laser as an AE source for calibration, and data were collected from a tensile test of an aluminum surface-cracked specimen. During the laser calibration experiments the AE from a focused Nd-YAG laser spot, which was translated 2.0 mm across a sample in 0.1 mm steps, was recorded and used to locate the origin of the AE. The results showed the basic capability of the system to discriminate between initiation sites less than 100 ..mu..m apart. The aluminum fracture experiment showed the capability of an enhanced system to record real events with a response time of less than 12 ms between events. The dynamics of the initiation site evolution show the progression of the crack growth across the pre-crack tip. Research is now being pursued to both validate these preliminary results and utilize the information on the dynamics of the fracture event.