In the flexible roll formed profiles, flange wrinkling and web warping are two major failure modes. Most of
previous studies focused on understanding the causes of web warping and proposing solutions to overcome it and
very few studies have been conducted on the analysis of the wrinkling in the flexible roll forming process. Groche
et al., (2010c) developed a one-step-model to design flexible roll formed U-profiles free of wrinkle. They
calculated critical stress by Euler formulation for buckling calculations of plates. A correction factor, k, was
obtained from FEM simulation and was added to Euler formulation.
Generally, wrinkling is an unstable deformation due to excessive longitudinal compression at the strip edge
(Kasaei et al., 2014). Wrinkling may be occurred at the constant cross section zone and also variable cross section
zone in the flexible roll formed profiles. Reasons of the longitudinal compression at the constant cross section zone
are similar to those in the conventional roll formed profile. Due to changing cross section, complex deformations
create at the variable cross section zone so that some portion of flange is compressed in the longitudinal direction.
The reason of the longitudinal compression is different from those at the constant cross section zone. Therefore, in
this paper, the flange wrinkling at the variable cross section zone is investigated