Numerical analysis and experimental investigation of residual stress and properties of T-joint by a novel in-situ laser shock forging and arc welding

A novel technique, referred to as Weld-LSF, has been proposed for the low-stress manufacturing of T-joints through in-situ synchronous assisted arc welding, employing laser shock forging. This innovative process introduces plastic deformation in the deposited weld seam at elevated temperatures, effectively reducing the tensile residual stresses (TRS) associated with welding. The thermal-mechanical coupling finite element model for Weld-LSF has been established, combining the classical bar-frame model and the inherent strain theory. The mechanism behind achieving low-stress welding of T-joints through in-situ LSF has been analyzed. Subsequently, experimental investigations were conducted using Q345 base metal and ER60-5 welding wire to study the influence of in-situ LSF on the microstructure and mechanical properties of the specimens. The results demonstrate that by introducing in-situ LSF at higher temperatures in the weld seam, tensile residual stresses are transformed from high to low levels, with the average TRS reduced from 342 MPa to 185 MPa, representing a significant reduction of 45.9 %. In-situ LSF forms a hardened layer with a depth of approximately 0.5 mm on the surface of the weld seam, albeit with certain depth limitations. Furthermore, the in-situ LSF treatment addresses the issue of poor ductility caused by stress concentration at the weld toe of T-joints, achieving a desirable combination of strength and ductility. The feasibility of in-situ LSF technology in welding fabrication has been established. In comparison to traditional welding techniques, the in-situ LSF treatment offers promising prospects for achieving low-stress welding, thereby enhancing the mechanical performance and fatigue life of the welding process.