Dynamic reflection behaviors of weld pool surface in pulsed GTAW

In this paper, a method was studied to determine the weld pool penetration based on the dynamic behaviors of the weld pool surface. To this end, relative works were performed to observe, measure, and analyze the development of a weld pool through the imaged laser matrix dots and correlate the changes in the imaged dots to the weld pool penetration. It was found that during partial joint penetration, the imaged dot matrix on the weld pool was clear and bright, but became fuzzier and dimmer when critical/complete joint penetration was reached. Results showed this was related to the root damping force in partial penetration, which obstructed the oscillation of the weld pool and made the surface relatively still for imaging. When critical/complete joint penetration was reached, the root damping force was diminished, and thus the pool surface oscillation was stronger, which led to dimmer and fuzzier images. By quantifying the relation between the image grayness variations with the penetration stages, a method was found for the automated control of the welding process.