Abstract: In order to study the mechanism of laser induced stabilization and compression of arc during laser-arc double-sided welding(LADSW) for aluminium alloy, the method of comparative study and the technique of infrared temperature-measuring and arc spectroscopic measurement are dedicated to investigate the physical essence of the laser effect on arc plasma. The results show that laser supplying arc with the anode spot which is caused by the high temperature gradient of laser is the ultimate reason for the laser induced stabilization and compression of arc when the keyhole is not fully penetrated, and the high energy density of laser and high thermal conductivity of aluminium alloy are indispensable. While the keyhole is fully penetrated, the arc spectral intensities of Ar lines during conventional arc welding are strongest, much weaker during LADSW for stainless steel and weakest during LADSW for aluminium alloy. It is indicated that the laser produces more laser plasma at the bottoms of the keyhole due to the higher saturated vapor pressure, which offers the easier electric channel for the arc. Therefore, the arc roots the laser induced plasma.

Key words: Compression of arc, Infrared temperature-measuring, Laser-arc double-sided welding, Spectroscopic diagnosis