Simulation based design of hybrid laser welding processes

In this paper, development of innovative configurations of the hybrid laser + GMA welding process for fatigue-critical welds and high-speed welding are described. Fatigue strength, which is often of concern in fabricated steel structures, is strongly related to the final weld shape in the weld toe region. For fatigue critical welding, the hybrid laser beam focus spot was larger than normal (to prevent keyhole formation) and was located at one edge of the weld pool to allow the weld metal to spread laterally. Experimental results showed that the wider hybrid welds had increased fatigue strength compared to conventional welds. For high speed welding, a similar weld pool width increase decreased capillary instability in the GMA weld deposit, suppressing the tendency for hump formation until higher travel speeds. The humped and defect-free weld beads were also predicted by simulation. In narrow GMAW gap welding, lack of fusion defects must be prevented at the sidewalls. A laser-hybrid process that used laser heating at the sidewall was demonstrated experimentally and was also simulated. The simulation results were well-correlated to the experiments and were useful in determining process parameters for preventing lack of fusion.