Application of Acoustic Emission Analysis for Inspection of Welds.

It is shown that the use of acoustic emission analysis (AEA) to control the welding process is limited by background noises. It is easy to detect cold cracking after welding and slag removal, but measurements during welding require additional methods to exclude noise. Crack detection is largely confined to cold cracks, i. e. to decohesions in the solid phase. Decohesions in the liquid phase cannot yet be detected. Measurements for process control are possible by utilizing a part of the sound sources, i. e. , those which are directly associated with the movement of the welding bath. In this way, relations showing relatively small variations can be established between specific causes of noise and the strength of welded joints.