Lyapunov exponent analysis for the evaluation of hybrid laser double-arc welding process stability

Hybrid laser double-arc welding is a complicated process with many random and uncertain influencing factors because of the interactions of energy, forces, and fields. The wire spacing is one of the main factors affecting the coupling behavior of laser and arc plasma and the stability of welding process. However, it is difficult to establish a precise mathematical model for evaluation of welding stability. In this paper, the largest Lyapunov exponent (LLE) of characteristic currents during the welding process under different wire-wire distances were numerically evaluated by the phase space reconstruction technique. Synchronous high-speed photography was adopted to observe arc shape and droplet transfer. The experimental and calculated results indicate that hybrid laser double-pulsed arc welding is a complex process of chaos. The LLE can provide a criterion for welding stability and can agree well with the observation of electrical signal, arc shape, and droplet transfer. Research results are needed to understand the welding process and to guarantee a stable and safe joining.