Crack detection in upsetting of aluminum alloy using acoustic emission monitoring technology

Acoustic emission technology relies on detecting and converting elastic (acoustic) waves from solids undergoing internal structural irreversible changes into electrical signals. This technique represents a non-destructive testing method used in industrial fields such as weld monitoring, proof testing, and flaw detection of pressure vessels. In this study, the applicability of acoustic emission technology for detecting and monitoring defects in a workpiece during a metal forming process was studied. A notch shape was designed using the finite element method to induce a premature crack on the surface of aluminum alloy cylindrical specimens by compressing them using a pair of flat dies. During the upsetting tests, acoustic emission signals and images of the notched specimen were recorded in real time. The obtained acoustic emission signals were analyzed through various parameters such as amplitude, energy, and RMS to determine the crack occurrence. Moreover, the signal results were compared with those from images obtained simultaneously to confirm the crack detection. The experimental results showed that acoustic emission technology could successfully detect crack occurrence in aluminum materials during the upsetting tests. These results imply an opportunity to detect material defects during various metal forming processes using acoustic emission technology.