A theoretical study on external inversion process of a thin-walled tube over a circular die

The investigation of the inversion process of a thin-walled circular tube over a circular die is helpful for their applications in metal forming and energy absorption fields. Based on the geometric model with continuously changing curvature in the deformation area and an energy method, a new theory model was proposed to describe the inversion process. The expressions of forming radius, critical displacement and steady inversion force were obtained, and the effect of friction was considered. The critical displacement was first proposed to describe the inversion process. The analysis results show that the theoretical results obtained by the theoretical model are in agreement with the numerical and experimental results. The relative errors between theoretical results and numerical results of forming radius, critical displacement and steady inversion force are all less than 5% . The friction coefficient has negligible effect on the forming radius and critical displacement, but has great effect on the steady inversion force. © 2022 Chinese Vibration Engineering Society. All rights reserved.