Formability limits due to local buckling in thin-walled square tubes

This article focuses on the identification and quantification of the formability limits due to local buckling in thin-walled square tubes subjected to axial compression. The methodology involves subjecting a series of thin-walled square tubular specimens of varying lengths to axial compression to detect sudden changes in the evolution of in-plane strains over time and determine the critical strain values at the onset of local buckling. Digital image correlation is employed to monitor the evolution of the thin-walled surfaces and the in-plane strains during axial compression. Finite element analysis is utilized to create digital twins of the thin-walled square tubes subjected to axial compression. The overall methodology is based on a previously developed technique that was successfully applied to thin-walled circular tubes and results validate its effectiveness in determining, for the first time, the formability limits of thin-walled square tubes due to local buckling in principal strain space.