Analytical model for residual stresses in press-braked stainless steel thin-walled sections

The manufacturing process of cold-formed thin-walled sections induces cold work in members and affects their structural behaviour. To assess the effect of cold work, residual stresses and equivalent plastic strains in cold-formed sections need to be quantified. Laboratory measurements of residual stresses in cold-formed sections are time-consuming, difficult and of limited accuracy. The experimental quantification of equivalent plastic strains is even more problematic. This paper presents an analytical model for the accurate prediction of residual stresses and equivalent plastic strains in press-braked stainless steel thin-walled sections, in which the effect of material anisotropy is duly considered. The analytical model comprises two separate analytical solutions for the two stages of the manufacturing process respectively: the coiling-uncoiling process and the cold bending of press-braking operations. The validity and accuracy of the model are demonstrated by comparing its predictions with those from a finite element-based simulation. This analytical model can be employed to define the initial state of such a section in a nonlinear finite element analysis of buckling behaviour.