This study reveals the evolution rule of welding residual stress of aluminum–lithium alloy skin-stringer T–joint under service load. Firstly

the 3D thermal-structural finite element model of T–joint dual laser-beam doubleside synchronous welding process was established

and the reliability of the model was verified by experiments to obtain accurate welding residual stress. Subsequently

the welding residual stress

strain distribution and total equivalent plastic strain were taken as initial conditions

and the finite element numerical analysis was combined with the elastic-plastic structural model to study the residual stress redistribution of the T–joint under service load. The results show that after the end of the applied load

the longitudinal stress relaxation of the skin is obvious (especially at the weld)

and the longitudinal stress in the middle of the stringer is not sensitive to the service load.