Mathematical modeling of the dynamic behavior of gas tungsten arc weld pools

The dynamic behavior of stationary fully penetrated gas tungsten are weld p ools was investigated through numerical simulation. The effects of are pres sure, electromagnetic force, and surface tension gradients on surface depre ssion, convection, and temperature distribution were calculated. The top su rfaces of fully penetrated pools were easily depressed since they were only supported by surface tension. Circulatory convection patterns were generat ed by electromagnetic forces and surface tension gradients and were signifi cantly affected by the vertical velocity component produced by pool oscilla tion. The temperature distribution in and around the pool was influenced by pool convection. During pool formation and growth, the fully penetrated mo lten pool sagged dramatically when the bottom pool diameter approached the top diameter. The sagged pool oscillated with higher magnitude and lower fr equency than partially penetrated or fully penetrated pools before sagging occurred. The dynamic behavior and the amount of material lost during melt- through were affected by the pool size and the magnitude of are pressure.