Integrated design and numerical simulation of stiffened panels including friction stir welding effects

Stiffened panels are lightweight structures with high resistance, composed by a base plate with stiffeners in one or more directions. The structural design, in most cases, focuses mainly on the longitudinal compressive loads that the panels are subjected to and can safely withstand. Welding processes used to build large stiffened structures, such as friction stir welding (FSW), are responsible for introducing geometrical imperfections, changing the material properties and adding residual stresses. These factors can therefore affect the panel's structural behaviour when subjected to compressive loads. In this work, the longitudinal residual stresses that arise from FSW processes were measured by means of the contour method. These residual stresses were then introduced into a numerical simulation model based on the finite element method (FEM), and their effect on the buckling collapse load was assessed. The sensitivity of the models to initial geometrical imperfections was also analysed. It could be inferred that the collapse loads showed no relevant sensitivity to the inclusion of the residual stresses in the tested model, being nevertheless affected by small variations of the initial geometrical imperfection magnitude.