Study On The Development Of Three-dimensional Weld Pool Surface Of Gas Tungsten Arc Weld Based On Structured Laser

During welding process, the TIG weld pool includes sufficient infromation with the characterization of the welding quality, such as weld penetration status. Thus, in order to achieve controlling desired weld integrity in the welding process, a series of research work on the relationship between the convex and concave of weld pool surface, the dynamic development process of weld pool surface and weld penetration and so on, were analyzed. In this paper, researches on weld pool surface were carried out based on dots laser and grid laser vision sensing, which based on the weld pool surface mirror-reflection characteristics and the difference between weld pool surface and the workpiece surface was put forward by Professor Zhang Yuming.Firstly, the patterns of weld pool surface reflection imaging were analyzed based on grid structured. The patterns of weld pool surface reflection imaging of concave and convex surfaces were analyzed with setting artificial obstacles. The results show that, when the obstacles set at the left side of the convex surface and close to the laser generator, the blind imaging area appeared on the left and top of the imaging screen. Thus, the convex reflection imaging in the horizontal direction is sequential pattern, but in the vertical direction is the inverted sequence. And for concave, when the obstacles set at the right side of the concave and close to the position of the imaging screen, the imaging blind area is positioned near the on the left and top of the imaging screen. Thus, the concave reflection imaging in the horizontal direction is the inverted sequence, but in the vertical direction is sequential pattern.Secondly, the single imaging screen experimental system of imaging screen was establisged, which imaging screen vertical to workpiece surface. The standard of concave and convex laser reflection imaging pattern are analyzed, and the concave and convex laser reflection imaging pattern from a theoretical point of view was verified. The experimental system was put forward based on the angle between imaging plane and the horizontal plane is 60 degree. The three-dimensional size of the weld pool was calculated. Based on that, the experimental system was mainly comprised of two imaging plane, which are perpendicular to the horizontal plane, to reconstruct the three-dimensional weld pool surface. And then the preliminary experiment research and error analysis were carried out.Thirdly, the convex and concave and penetration state of the weld pool surface was explored at the different welding current. The pattern of reflected structured laser can represent the degree of weld joint penetration in real time during the welding process. Conbining the simulation method and the experimental point of view were be employed to analyze the dynaminc development of the stationary TIG weld pool surface, at the same time, the welding current influences on the width and depth of weld joint of stationary TIG were analyzed. The results show that when the welding current of 70 A, simulation and the experimental results show that the weld pool surface changed from convex to concave, and structrued laser was also garther together slowly. During the stationary TIG welding process, the weld pool surface is dynamic development. When the welding current of 50 A, the weld pool surface was always convex during welding process. And with the increasing of welding current, the weld pool surface is convex at the beginning of the welding. With the welding continue, the weld pool surface pattern begin changing from convex to concave and the complete penetration was eventaully established. The experimental and simulation results show that the relationship between the concave and convex of weld pool surface, the dynamic development process of weld pool surface and weld penetration can be represented by the laser imaging modality which is reflected by weld pool surface.Lastly, the changing law and oscillation law of the pulsed TIG weld pool surface were discussed. The MATLAB was employed to analyze the oscilation evolution process of the pulsed TIG weld pool surface. And three-dimensional surface oscilation mode of pulsed TIG welding pool was studied based on the shape variation characteristics of grid laser. The results show that the ocsilation mode of the pulsed TIG welding pool was subjected to the Bessel’s equation.