Laser-GMA hybrid welding: Process monitoring and thermal modeling

Laser-Gas Metal Arc (GMA) hybrid welding is an increasingly accepted technology for a variety of commercial applications, from industries as diverse as shipbuilding to automobile manufacture. As applications become more widespread, there is a growing need to understand the relationship between the numerous process parameters and the process results, including weld quality and distortion. To build upon the body of knowledge supporting this, two separate experiments are performed. In the first, hybrid welds are performed with a 2.6kW Nd:YAG laser and sensors are used to monitor GMA voltage and current, as well as the arc-plasma electromagnetic emissions in both the ultraviolet and infrared regions. Process perturbations, such as fluctuations in GMAW voltage and wire speed, laser angle of incidence, and laser/GMAW torch head separation distance, are introduced to study their effect on sensor output. Finally, thermal finite element models are developed and used to quantify the varying heat input per unit length when compared with conventional GMAW and laser welding processes, particularly as applied to joining of thin steel structures. The onset of buckling during weld fabrication has been shown to be strongly dependent upon the heat input used to produce the weld. A thermal model of the laser-GMA hybrid welding process is developed to serve as a representation of this complex process.