THERMO-MECHANICAL FINITE ELEMENT ANALYSIS OF COMPRESSIVE AXIAL PRESTRESS IN FRICTION STIR WELDING OF DISSIMILAR AA6061-T6 AND AA5083-H111 ALLOYS

Friction stir welding (FSW) of dissimilar aluminium alloys is accompanied by non-uniform thermal expansion and contraction that can generate significant residual stresses and influence joint response. This study numerically investigates the effect of externally applied compressive axial prestress on the thermo-mechanical behaviour of dissimilar AA6061-T6 and AA5083-H111 friction stir welded joints. A three-dimensional coupled thermo-mechanical finite element model was developed in ANSYS Workbench. The FSW process was represented using a moving heat source, and the resulting transient temperature field was transferred to the structural analysis to determine equivalent stress, longitudinal stress, equivalent elastic strain, and total deformation. Nine compressive prestress conditions from 0 to 40 kN were examined. Equivalent stress, longitudinal stress, and equivalent elastic strain decreased progressively up to 35 kN. At 35 kN, equivalent stress decreased from 213.01 to 168.02 MPa, longitudinal stress from 115.37 to 56.21 MPa, and equivalent elastic strain from 0.0030916 to 0.0024389. Total deformation increased only slightly with prestress. Among the investigated conditions, 35 kN provided the most favourable overall thermo-mechanical response. The results indicate that controlled compressive prestressing has potential as a strategy for reducing welding-induced stresses in dissimilar aluminium FSW joints, subject to future experimental validation.