Empty circular metal tubes in the splitting process – theoretical and experimental studies

Highlight
• This article investigates the splitting process of circular tubes by conical dies.
• The analysis is performed by theoretical and experimental methods.
• Instantaneous axial load of the circular metal tubes is derived, theoretically.
• Curl radius of circular metal tubes during the process is obtained, theoretically.
• Effects of geometrical characteristics of tube and die on axial load are studied.

This article derives some theoretical relations to predict the instantaneous axial force of the circular metal tubes during the splitting process under the axial compression by the theoretical and experimental methods. A new theoretical model of splitting deformation of the circular tube as a thin-walled structure subjected to the axial loading is introduced and based on the deformation model and using the energy method, some analytical formulas are derived to estimate the instantaneous axial load, maximum splitting load, steady force and curl radius of the tubes. To verify the present theory, some aluminum, mild steel and brazen tubes with the circular cross-section and different geometrical and material characteristics were prepared and axially compressed on conical dies with the different cone angles. Comparison of the theoretical predictions and the experimental measurements shows a good correlation and it affirms verity of the new theoretical deformation model and the present theory. Also, based on the experimental results, the effects of wall thickness and inner radius of the tubes and also, number and length of initial slits and semi-angle of conical die are studied on the axial load and maximum splitting load.