Mathematical modelling of gas tungsten arc welding (GTAW) and gas metal arc welding (GMAW) processes

grantor: University of TorontoGTAW process. Models for the GTAW arc and the weld pool were developed. In the arc model, the shape of the electrode tip was addressed and the effect of the electrode tip angle in the range of 10 to 150 degrees on the arc properties, especially on the anode current density, the heat flux and the gas shear stress over the weld pool, was studied. It was found that by increasing the electrode tip angle, the anode spot at the weld pool surface tended to be more localized. This led to higher maximum heat flux and anode current density. On the other hand, the gas shear stress increased with decreasing electrode tip angle. The variation in the anode current density, the heat flux and the gas shear stress with the electrode tip angle has significant effect on the weld pool properties. By developing a model for the weld pool the variation in the weld pool due to variation in the electrode tip angle was studied. In the weld pool model, by considering the four flow driving forces into the weld pool, it was found that, in determining the flow pattern into the weld pool and hence its shape, the gas shear stress and surface tension are dominant forces. GMAW process. A model for GMAW arc is developed. In this model a cathode spot defined such that the electrons with a constant current density emit from the cathode surface. It was found that the radius of the cathode spot is a function of applied current, and length, electrode diameter and shielding gas. This model can successfully predict the arc properties, such as temperature, gas velocity and gas pressure at the surface of the cathode in both argon and helium for 2-10 mm arc of applied currents from 100 to 250 A.Ph.D