Abstract

Welding-induced residual stresses play a critical role in crack initiation and reduced reliability of shell-and-tube heat exchangers, particularly in tube-to-tubesheet joints. Despite extensive numerical investigations in this field, the combined effect of tube spacing and welding sequence in triangular tube layouts has not yet been systematically examined. In this study, a three-dimensional numerical model based on a coupled thermo-mechanical analysis is developed to predict the residual stress distribution in tube-to-tubesheet joints. The gas tungsten arc welding (GTAW) process is modeled considering a single-pass circumferential fillet weld, and the arc heat input is applied as a time-dependent Gaussian heat flux via a dedicated user subroutine implemented in ABAQUS. The primary novelty of the proposed model lies in its ability to accurately reproduce various welding sequences and to evaluate the resulting thermo-mechanical superposition effects on the final residual stress field. Numerical results indicate that modifying the welding sequence alone, without applying any stress-relief treatment or altering process parameters, can lead to a significant redistribution of stresses and a reduction of tensile residual stresses by up to 97% in the triangular tube arrangement. For validation purposes, the transient temperature field during welding is measured using infrared thermography, while residual stresses are experimentally determined by X-ray diffraction. A good agreement is observed between the numerical predictions and experimental measurements. The developed numerical framework provides an effective tool for optimizing welding sequences and enhancing the service life of industrial heat exchangers.