RESIDUAL STRESS EVALUATION OF AA2024-T3 FRICTION STIR WELDED JOINTS

Abstract. The main aim of this study was to evaluate the residual stress field in friction stir welded joints of 2024-T3 aluminium alloy using the crack (or cut) compliance method. It 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 gauges 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 a 3.2x60x120mm3 rectangular testpieces. For the longitudinal cut testpieces, the slot was introduced in two different positions: on the centre of the weld nugget and 5mm distant from the weld centre line, representing the thermomechanically/heat affected zone. The residual stress intensity factor, Kr, was calculated using a fracture mechanics approach and the inverse weight function method was employed to obtain the initial residual stress profile. Additionally, the residual stress redistribution profiles ahead of the slot were determined for several slot lengths, simulating the growth of a crack into the residua