Numerical simulation of liquid bridge breakup in short-circuit transfer process

The dynamic characteristics of the short-circuit transfer mode are investigated using a numerical model based on the volume-of-fluid method. The stability problem in an electromagnetic fluid cylinder is simulated, of which the result demonstrates good agreement with the exact analytical solutions of the pinch instability theory. The integration of numerical simulation with theoretical analysis clarifies the dominant factors in liquid bridge breakup: surface elongation and axial flow. During short-circuit transfer process, the control parameters (welding current waveform and wire retraction speed) directly affect the two abovementioned factors, which can be evaluated by tracking only the pinch radius instead of the entire surface profile. The pulse current temporarily concentrates pressure on the neck of the liquid bridge, thereby accelerating the axial flow. By contrast, wire retraction changes the surface profile and reduces capillary retention. In conclusion, an appropriate control guide for short-circuit transfer process is considered.