FE analysis of the residual stresses for the laser welded T-joint of Al-Li alloy under service loads

This paper attempts to reveal the evolution of welding residual stresses (WRS) in skin-stringer structure of Al-Li alloy exposed to service loads. 3D thermal-structural finite element (FE) formulation of the dual laser-beam bilateral synchronous welding process is first derived, and its accuracy is verified by experimental tests to acquire accurate WRS. FE numerical analyses incorporated with the elastic-plastic constitutive model, taking the WRS, strains distribution and total equivalent plastic strains as an initial condition, are next carried out to explore the residual stresses redistribution of the T-joint under service loads. The results unveil that longitudinal stress relaxation is pronounced (especially at the weld) in the skin after the end of the loads applying. However, the longitudinal stress in the middle of the stringer is not sensitive to the service loads. The extended high tensile stress concentration zone inside the joint in case 2 and case 4 maybe the potential failure location after the progressive loading of the skin-stringer welding structure. Additionally, the weld toe, which is the obvious stress sudden change zone in the service process, is a non-negligible position for the improved failure estimation of the aerospace skin-stringer structure.