Acoustic emission diagnostics of faulty fusion in welding

A brief analysis of faulty fusion in welding is presented. A physical model revealing the mechanism of generation of elastic mechanical waves which occur at the moment of metal structure formation in faulty fusion is suggested. As a result the phenomenon of inception of acoustic emission was determined for the first time ever, the information-bearing parameters characterizing real-time initiation of faulty fusion amid existing disturbances were determined. It was found out that in pulse argon arc welding of austenitic steel with intense cooling of heat-affected zone, short compressing and pulling stresses in metal during its crystallization take place. This stresses are added to the stresses taking place in a faulty fusion mouth and lead to rupture of interatomic bonds and emission of elastic mechanical waves interpreted as acoustic emission where acoustic emission signals are distributed by an amplitude attribute. Besides it was determined that acoustic emission signals originated by the processes of faulty fusion initiation and development and the process of crack formation registered in the same amplitude analyzer channel are distributed by the number of acoustic emission impulses.