Study on the transient impact energy of metal droplet transfer in P-MIG welding based on acoustic emission signals analysis

According to the structure-borne acoustic emission (AE) signals detected in pulsed metal inert gas (P-MIG) welding on aluminum alloy, the energy gradient and total energy of AE signals were used to describe the rate of impact energy and total impact energy coming from metal droplet transferred into molten pool. The results showed that there were three types of energy gradient curves according to three modes of metal droplet transfer (MDT). The characteristics of energy gradient curves had a close relation to the transient impact energy of MDT. The energy gradient of MDT decreased with the rise of pulse frequency during the impact process of not only one metal droplet but also several metal droplets within 0.04 s. So, the variation rate of impact energy was lowered with the raise of transfer frequency on the premise of one droplet per pulse mode. Total energy of AE signals coming from not only one metal droplet but also several metal droplets within 0.04 s also demonstrated a downward trend. On the premise of one droplet per pulse mode, the variation of the transient impact energy accorded with an exponential attenuation model. (C) 2015 Elsevier Ltd. All rights reserved.