DEVELOPMENT OF A WELDING MONITORING SYSTEM FOR IN-PROCESS QUALITY CONTROL OF THICK WALLED PIPE

The authors have developed a systematized in-process quality control system for arc welding of thick walled pipe utilizing visual sensors and computers. This system consisted of four main subsystems that monitor the welding conditions, monitor the weld pool shape, visualize the weld bead shape, and visualize inner defects, respectively. The welding condition monitoring system detects abnormal welding conditions using an electric signal. The weld pool shape monitoring system assesses the position among weld pool, the electrode, wire, and groove using a charge coupled device (CCD) camera and filters. The weld bead shape visualization system detects abnormal bead surface conditions using a three-dimensional (3D) visual technique. The inner defect visualization system was achieved using a laser-ultrasonic in-process testing (LUT) technique and synthesis aperture focus technique (SAFT). Each subsystem informs workers of unsuitable welding conditions to allow them to reestablish the suitable conditions. Furthermore, the in-process quality control system was applied to thick walled pipe welding to verify the practicality of this system for improving the quality and efficiency of welding operations.