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Welding Pool Oscillation Behaviors for Pulsed GTA Welding Based on Laser Dot Matrix Sensing

Pool oscillation is thought to have a direct relationship with weld joint penetration and appropriate oscillations help refine grains and reduce defect sensitivity. This paper uses a novel laser dot-matrix sensor to observe the pool oscillation three-dimensionally and use the 3D data as an enhanced ability to analyze oscillation behaviors. It was found that there exist three oscillation modes associated with partial, full, and critical penetration during the base time period. From the observed three dimensional dynamic evolution process, the periodical contraction and expansion at its natural frequency as excited by the pulsing current are observed/found. The amplitude of the oscillation is found to gradually decrease as the oscillation process proceeds and the liquid metal solidifies during the base current period. Furthermore, the amplitude is found to increase as the peak current increases. Because of the enhanced ability on three dimensional observation of the oscillation, this study enhanced the understanding on the pool oscillation and experimentally verified certain theoretical derivations about oscillation which have not been experimentally verified previously.