Abstract: The local, nonuniform heating and subsequent cooling during the welding processes causes complex thermal stress/strain fields to develop that finally leads to residual stresses, distortions, and their adverse consequences. Residual stresses are of prime concern to the industries producing weld-integrated structures around the globe because of their obvious potential to cause dimensional instability in welded structures, contribute to premature fracture/failure, along with the significant reduction in fatigue strength and in-service performance of the welded structures. Arc welding with single or multiple weld runs is an appropriate and cost effective joining method to produce high-strength structures in these industries. A multifield interaction in arc welding process makes it a complex manufacturing process. A number of geometric and process parameters are contributing to significant stress levels in arc-welded structures. In the present analysis, parametric studies are conducted for the effects of a critical geometric parameter, that is, tack weld on the corresponding residual stress fields in circumferentially welded thin-walled cylinders. Tack welds offer a considerable resistance to the shrinkage and the orientation, and size of tacks can alter altogether the stress patterns within the weldments. Hence, a critical analysis for the effects of tack weld orientation is desirable.

Abstract: The control of weld-induced imperfections like welding deformations and residual stresses is of critical importance in circumferentially welded thin-walled cylinders due to their wide utilization in high tech engineering applications in aerospace and aeronautical structures, pressure vessels and nuclear engineering fields. The paper presents a computational procedure for the analysis of temperature distributions and the subsequent residual stress fields during the course of arc welding of thin-walled cylinders of low carbon steel. Parametric studies based on numerical simulations are conducted to investigate the effects of critical welding process parameter on weld-induced residual stresses. Temperature-dependent thermo-mechanical behavior for low carbon steel, filler metal deposition along with double ellipsoidal heat source model is incorporated. The accuracy of the developed finite element simulation strategy is validated for transient temperature distributions and residual stress fields through full-scale shop floor welding experiments with proper instrumentation for data measurement. The aim is to present data to confirm the validity of in-process circumferential welding technology for thin-walled cylinders so that the in service failures of these structures due to process specific inherent stresses may be minimized.

Abstract: Arc fusion welding predominates in the welding industry as a reliable joining method and has been the subject of investigations by researchers for decades. To ensure in-service structural integrity, optimization of weld-induced imperfections such as welding deformations and residual stresses is critically desirable in circumferentially welded thin-walled cylinders owing to their wide applications in aerospace and aeronautical structures, pressure vessels, and nuclear engineering fields. In this research, computational methodologies for sequentially coupled non-linear transient thermomechanical analysis of the complex arc welding of thin-walled cylinders of stainless steel (AISI 304) are presented. Detailed three-dimensional finite element (FE) simulations with a single V butt-weld joint configuration of 150 mm outer diameter and 3 mm wall thickness cylinders are carried out to investigate the effects of varying structural boundary conditions (mechanical constraints) on weld-induced distortions and residual stress fields. Basic FE models are validated with carefully recorded and properly instrumented experimental data for temperature distribution, deformations, and residual stresses. Predicted and measured welding distortions and residual stresses are compared and discussed in detail. The results reveal that axial deformations are strongly dependent on the degree of restraints. Low-restraint structures exhibit high axial shrinkage, and vice versa. Diametral/radial shrinkage for different clamping conditions show no significant variation. Further, residual stresses show a weak dependence on the degree of restraints. Although the stress levels slightly vary in magnitude, a similar trend is observed for all the structural clamping conditions studied.

Abstract: The research work presents a computational methodology based on three-dimensional finite element model to simulate the gas tungsten arc welding (GTAW) of thin-walled cylinders. The aim was to study the effects of two basic welding parameters (welding speed and welding current) on weld induced residual stresses. The complex phenomenon of arc welding was numerically solved by sequentially coupled transient, non-linear thermo-mechanical analysis. The accuracy of the numerical model was validated through experiments for temperature distribution and residual stresses. The results reveals that the present simulation strategy can be used as a proper tool to get the optimized welding process parameters and minimize the in service failures of thin walled structures due to residual stresses.