Integration of Weld Pool Dynamics in the Numerical Investigation of Residual Stresses in a Gas Tungsten Arc Welded Joint

Residual stresses due to welding can significantly impair the performance and reliability of welded structures. As a result, there has been a recent increase in the prediction of residual stresses using numerical modeling of welding processes [1, 2]. Determination of that critical residual stress that initiates a crack during welding has been of considerable interest for some time [3]. Existing research has used finite element models to generate the thermal profile in the workpiece under a moving arc heat source. These models have considered only the conduction mode of heat transfer in the workpiece. Hence, effects of convection under driving forces like surface tension gradient, electromagnetic force, buoyancy, etc. was not considered in the prediction of the temperature profile in the welded structure. Research on weld pool dynamics has established that weld pool depth/width and heat affected zone (HAZ) are significantly altered by these driving forces [4, 5]. Hence, it is absolutely necessary to incorporate the effects of these driving forces for a more accurate estimation of the thermal pattern in the welded structure and thereby result in better prediction and analysis of thermally induced residual stresses in a welded structure.

In the present investigation, CFD simulation of weld pool dynamics under Gas Tungsten Arc (GTA) welding is conducted. The thermal profile of the welded joint, including the driving forces, is then imported into a finite element (FE) solver to simulate the thermally-induced residual stresses. Using this methodology, we have successfully simulated the thermal stresses that arise during GTA welding [6, 7]. The present study aims to provide detailed insight into the significance of welding parameters, like welding speed, welding current, surfactant activity, etc., on the residual stresses in the welded joint. Such an analysis will aid in the better prediction of welded structure distortion and failure under operational loads.