The squaring process to shape a circular tube into a symmetric square clad tube is examined by a three-dimensional incremental elastic-plastic finite-element method based on an updated Lagrangian formulation. The effects of various parameters, such as geometric ratio R/t, strain hardening exponent n, friction coefficient μ, and the length of tube L, on the occurrence of collapse in the squaring process are discussed and interpreted in a theoretical manner. The findings show that geometric ratio is the major factor in the process of squaring circular tubes. When R/t=25, serious collapse is likely to appear. Aiming at circular tubes with geometric ratio R/t=25, this study proposes six analysis configurations for clad tubes to discuss the possibility of clad tubes avoiding collapse. The findings showed that clad tubes could effectively reduce the collapse ratio.
