熔池三维自由表面状态与TIG焊熔透的相关性研究

RESEARCH ON THE CORRELATION BETWEEN THE STATUS OF THREE-DIMENSIONAL WELD POOL SURFACE AND WELD PENETRATION IN TIG WELDING

基于激光视觉测量原理,采用2台同规格的CCD摄像机实时同步采集了钨极惰性气体保护电弧焊熔池自由表面和背面熔宽动态变化视频图像,利用熔池自由表面三维恢复算法获得熔池三维自由表面形貌,并对不同熔透状态的熔池三维自由表面高度变化与同步采集的背面熔宽变化间的相关性进行了定性分析实验.通过建立理想熔池自由表面,入、反射激光束光学变换及成像屏数学模型,逆向仿真研究了不同熔透状态的熔池表面对反射激光点阵形态的影响规律.结果表明,基于激光视觉法获得的熔池三维自由表面动态变化与焊缝熔透之间具有相关性,当焊缝由未熔透过渡到熔透时,熔池表面由凸形逐渐变为凹形,且塌陷量随背面熔宽的增加而缓慢增大,反射激光点阵行曲率变小,激光点逐渐聚为一点.当过熔透时,背面熔宽增加,熔池表面塌陷量迅速增加,反射激光点阵行曲率反而变大,聚集的激光点阵纵向逐渐被拉开.熔池表面逆向建模仿真结果与实际测量结果基本一致,利用反射激光点阵的形态变化可以表征熔透变化.

Measurement of the weld pool surface is a difficult but urgent task in the welding community. It plays an important role in developing the next generation intelligent welding machines, in particular, controlling the weld joint penetration in automatic welding. In this work, the images of front-side free surface and back-side width of the weld pool are synchronously captured with two CCD cameras in tungsten inert gas （TIG） arc welding process based on laser vision, and the three dimensional weld pool surface is reconstructed using designed algo- rithm. Then, the correlation between the weld pool surface under different weld joint penetration and its back-side width is analyzed qualitatively. The variation of reflected laser dots shape is reversely simulated under differentdepths of weld pool surface, which represents the different weld joint penetration, after established the standard model of weld pool, incident, reflected ray and imaging plan＇s mathematical model. It is found that the change of weld pool surface obtained by this method has an intimate immanent correlation with the weld joint penetration. When the weld joint penetration changes from partial penetration to complete joint penetration, the weld pool sur- face＇s shape changes from convexity to concave, and its depth is increasing with the increased back-side width. The row curvature of reflected laser dots is diminishing. When the penetration achieves excessive penetration, the depth of the weld pool surface is more rapidly increased, and the row curvature is also increased. The gathered laser dots is drawn back again at parallel direction. The simulated results associate with the measurement very well. The vari- ations of reflected laser dots shape can represent the degree of weld joint penetration. This research lays a good foundation for the control of weld joint penetration using the characteristics of weld pool surface.