Numerical simulation of transient 3-D surface deformation of a completely penetrated GTA weld

By establishing the correlation between transient behavior of a weld pool surface deformation and workpiece penetration, and quantitatively analyzing the surface deformation at the top and bottom surfaces at the moment the pool penetrates and their dynamic responses to welding process parameters will provide basic data for the development of topside vision-based penetration control in gas tungsten arc welding (GTAW). A transient numerical model was developed to investigate the dynamic behavior of a completely penetrated GTAW joint. A complete and comprehensive scheme was used in which many factors, such as moving arc, 3-D fluid and heat flow fields, transient state, completely penetrated weld, and surface deformation at both the top and bottom surfaces were considered. The transient development of 3-D surface deformation and shape of a weld pool during the period from partial penetration to complete penetration is predicted. The simulated results showed that the ratio curves of the maximum depression to the length and width at the top surface of the weld pool at different times clearly indicated basic information on penetration. Therefore, the relation of the ratios vs. time can be used as an indicator to judge whether the joint is penetrated.