Evaluating and predicting the collapsing tendency of fully penetrated gas tungsten arc weld pools

In numerical modelling and simulation of fluid flow and heat transfer phenomena, it should be ensured that the output data have practical meaning, so that the models are capable of automatic judging and evaluation of functions to predict the collapsing tendency of a fully-penetrated weld pool for any input process parameters. In this study, a subprogram is combined with a comprehensive model for weld pool behaviours in gas tungsten arc welding (GTAW) to evaluate and predict the tendency or possibility of the weld pool collapsing so as to avoid over-penetration and/or burn-through. The forces acting on a weld pool are analysed in detail. A model of static force conditions for a fully-penetrated weld pool is developed, and a criterion is set up to judge and evaluate the tendency for occurrence of over-penetration and/or burn-through defects. The transient variations of the forces affecting surface deformation and collapse of the weld pool are computed, and the percentages of their influencing roles are obtained. For a specific material and workpiece thickness, the threshold values below which the burn-through phenomenon does not occur are determined, and compared to the experimental results.