Residual Stress Evaluation of AA2024-T3 Friction Stir Welded Joints

The main aim of this study was to evaluate the residual stress field in friction stir welded joints of 2024-T3 aluminum alloy plates using the slitting method. This is based on the fact that when a cut, simulating a growing crack, is incrementally introduced into a part, residual stresses are relieved on the slot surfaces created, causing the part to deform. Such deformation can be measured by strain gages attached to specific regions of the part and the residual stress profile that originally existed can be evaluated. Cuts were introduced by wire electro discharge machining (WEDM), in finishing mode, either perpendicularly or longitudinally to the weld nugget, in 3.2 × 60 × 120 mm³ rectangular testpieces. For the longitudinal testpieces, the slot was introduced in two different positions: on the center of the weld nugget and 5 mm distant from the weld center line, in order to sample the thermomechanically/heat affected zone. The residual stress intensity factor, K _r, was calculated using a fracture mechanics approach and the inverse weight function method was employed to obtain the initial residual stress profile. Residual stress redistribution profiles ahead of the slot tip could also be derived using the inverse weight function method. However, for cracked components subjected to compressive residual stress fields, when the crack faces are in contact, a non-linear problem arises and the zero displacement condition has to be taken into account in order to provide a more accurate solution of the residual stress field.