A design method for rectangular hollow sections in bending

Local deformation of individual cross-sectional members is of great interest in the bending of aluminium alloy extrusions for automotive applications. The primary concern is the impact of such distortions on the manufacturability of components as well as the dimensional tolerances of the final build. This paper presents analytical models for the determination of local post-buckling and suck-in deformations in bending. The models are based on the deformation theory of plasticity combined with an energy method using appropriate shape functions. The analytical predictions are verified with experimental results. Based on the present findings, an approximate design method for evaluation of the bendability of sections in industrial forming operations is proposed. The results show that the slenderness ratio (b/t) and the width of the flange are the main parameters related to the bending radius at the onset of plastic buckling and the magnitude of local deformations, respectively. Material parameters have proven to be relatively more important to buckling radius than to deformation of individual cross-sectional members. Although there is some discrepancy between the experimental and theoretical results at tight nominal bend radii, the overall correlation is surprisingly good. It is, therefore, concluded that the present approach provides an efficient method for the evaluation of the bendability of rectangular hollow sections.