The squaring processes to shape the circular tube into a symmetric square-tube are examined by an incremental elasto-plastic finite-element method based on an updated Lagrangian formulation. The highly non-linear problems due to the geometric changes, the

This paper sought to render the simulation of metal forming process closer to the reality in order to better control the results of metal forming. The friction on the upsetting workpiece and die contact face has always been a subject of great concern. This study focused on the variation of the friction coefficient during the upsetting process and the concept of treating the solution of unknown parameters as an inverse problem. The inverse calculation of upsetting a cylindrical mild steel in this paper was based on the load values measured in the upsetting experiment to solve the variation of the friction coefficient during the upsetting process. By means of the inverse algorithm presented in this paper, physical phenomena that better approximated the reality could be obtained, which added to the completeness of the simulation of the entire upsetting forming process.