Integrated thermo-mechanical FE model for weldability assessment of remote laser welded CR420LA-GI low alloy steel under variable process parameters

Laser beam welding (LBW) is increasingly used for joining high-strength steels; however, its performance depends on coupled phenomena such as heat transfer, melting/solidification, phase transformation, and residual stress development, making process optimisation challenging. Although Computational Fluid Dynamics (CFD)-based approaches can capture these effects with high fidelity, they are often computationally expensive for industrial applications. This study presents a unified thermo-mechanical framework for remote LBW by combining a double conical-Gaussian volumetric heat source (DCVHS), adaptive thermal-to-mechanical coupling, and plasticity-based constitutive modelling. Unlike conventional thermo-mechanical welding models requiring manual definition of fusion-zone (FZ) and heat-affected zone (HAZ) domains, the proposed framework automatically identifies BM, HAZ, and FZ regions directly from the transient thermal field using temperature-based segmentation. These domains are subsequently used for automatic weld-joint generation through multi-point constraints (MPCs) and for zone-specific material properties assignment, enabling adaptive weld modelling under varying process parameters. A semi-empirical sigmoid regression model further enables prediction welding parameters such as laser power, welding speed, and penetration depth. Mechanical behaviour is evaluated using a plasticity model to predict tensile, lap-shear, and cross-tension performance of the joints. Validation through bead-on-plate and overlap welding experiments, metallography, microhardness mapping, and mechanical testing demonstrates good agreement between simulations and experiments, confirming the framework’s predictive capability and computational efficiency for weldability assessment and welding process optimisation.