Modeling of Oscillations in Partially Penetrated Weld Pools

Several investigators have proposed controlling the size and shape of the weld pool based on the weld pool oscillations. This paper proposes two models that could be used to predict the weld pool geometry based on the natural frequency of the pool. The models, one a lumped parameter model and the other a distributed parameter model, included effects of liquid metal density and surface tension along with weld pool geometry. Weld pool oscillations were measured through signal processing of arc voltage and current for stationary gas-tungsten arc (GTA) welds. Welds were performed at different weld voltages and currents on different materials in order to vary width, depth, density, and surface tension. The models developed here were shown to have reasonable agreeement with experimentally measured weld pool resonant frequencies. Also, with geometric conditions similar to those commonly found in GTA weld pools, the different models tend to agree well with one another.