A sequential investigation of the residual stresses and strains influence on the buckling of cold-formed thin-walled members

In this study, a specific formulation and its corresponding computational code are developed using: (i) an alternative 3D finite strain elastoplastic theory based on the multiplicative Flory decomposition, (ii) a node -surface contact algorithm to model sheet folding and (iii) a 3D prismatic solid-based finite element with high order approximation. Employing the developed code, a sequential analysis is presented that involves (i) folding an initially flat sheet in the dimensions of the studied thin-walled U-member, from which results the residual stresses of the manufacturing process, (ii) changing the boundary conditions to enable the application of linear basic loads that generate the buckling situation and (iii) solving the buckling of the cold-formed thin-walled U-member. We used literature benchmarks to show that the proposed 3D elastoplastic theory is sufficiently accurate to study the influence of residual stresses and geometric defects (residual deformations) - arising from the folding process - on the critical loads of the studied U-member.