Study on barrelling behavior of variable-diameter tubes in axial hydro-forging sequence

Abstract

Axial hydro-forging sequence is an emerging approach in forming the variable-diameter tubes without thinning. However, after the batch production, a barrelling defect occurs at the end of the maximum diameter zone during the process. To investigate the barrelling behavior of the tube in axial hydro-forging sequence, experiments and finite element simulation were carried out in the present work. It could be concluded that the barrelling formation is attribute to the non-uniform stress distribution and the geometric feature of the tube. Subsequently, the effect of expansion ratio, friction coefficient and transition form on barrelling behavior was investigated. It was found that the degree of the barrelling increased with increasing the expansion ratio, but decreased with reducing the friction coefficient. Moreover, the transition form had a significant effect on the barrelling degree, and the barrelling defect can be eliminated when the transition form with circular arc was employed.