Laser Vision-Based Detection of Weld Penetration in GTAW An inspection method was proposed to monitor weld penetration for investigating the control of weld defects

In automatic gas tungsten arc welding (GTAW), incomplete joint weld penetration, excessive weld penetration, or weld pool collapse may occur due to changes in welding conditions or weld structures so that the required weld integrity cannot be assured. In order to real-time monitor the weld penetration to prevent these defects, an innovative method was proposed that detects the dynamic change of the reflection image area (RIA) for the laser pattern reflected by the specular weld pool surface. The dynamic change in the RIA was found to be determined by the weld pool surface, which was in turn determined by the weld penetration. Because of this physics mechanism, the RIA demonstrated two peaks that corresponded to the occurrences of the complete joint penetration and excessive penetration, respectively. This unique characteristic eases the determination of the weld penetration status based on a simple analysis of the one-dimensional RIA signal. Further, in comparison with the computation of the 3D surface of the weld pool, the RIA was computed simply by image binarization. The proposed method is not only innovative and physics based but also easy to implement online in real time. Experiments and comparative analyses from high-speed and back-side images, weld beads, and RIA signals verified the physics mechanism and the effectiveness of the proposed method.