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Correlation analysis among multiple images of plasma induced during fiber laser–arc hybrid welding

In this study, the multiple imaging morphological features of plasma have been observed by using the multiple-imaging technique during the fiber laser–tungsten insert gas (TIG) arc hybrid welding. Four images of the plasma can be simultaneously obtained in a picture. From the first image to the fourth image, there is a gradual decrease in area and a gradual increase in light intensity. The first three images have approximately consistent time-dependent area changes. This consistency and the stability of the first three images increase with the increase in the arc current or with the decrease in the heat source spacing or laser power. The third image has a higher area fluctuation frequency than the first image. The metal vapor and the shielding gas are not fully mixed, and the fluctuation of the metal plasma is the main cause of the hybrid welding plasma fluctuation.