Surface height and geometry parameters for describing shape of weld pool during pulsed GTAW

Weld penetration and fine formation are the major factors for consideration of weld bead quality. The geometry of weld pool contains abundant information about the weld penetration. The weld pool surface is depressed during full-penetration because of are impulse, and the weld pool surface may be convex during part-penetration or welding with filler. In this paper, we present the surface height and shape parameters for describing the three dimension of weld pool. During pulsed GTAW process, the weld pool image can be obtained through visual sensing system by the illumination of are light on weld pool. The inverted image of tungsten tip and are shape can be seen clearly from the weld pool image. The position of inverted tungsten tip varies with the surface height according to the principle of specula reflection. The point of tungsten tip is located to calculate the surface height. The shape of weld pool has been characterized with size and shape parameters, such as pool width, length and a series of rear angles, etc. A simple nonlinear formula with only four parameters is proposed for describing the pool shape, and the regression results are shown with high accuracy. Based on the surface height and geometry parameters of weld pool, the shape of weld pool can be strictly defined, which lays the foundation for further study on process model and weld penetration control.