PREDICTION OF ELONGATION WITH RESPECT TO THE ROTARY DRAW BENDING

Abstract

Corresponding author: skrahiman501@yahoo.com

 

In this paper, difficulties during pipe bending by rotary draw method are addressed and focused on elongation of the pipe, its dependency on geometrical and material properties. During pipe bending process by rotary draw method a large number of variants come into picture. These include outer diameter of the pipe(D_o), thickness(t), material properties, bend angle (θ), relative bending ratio (R_n/D_o), friction between contact surfaces etc.,. The two major problems during pipe bending by rotary draw method are springback and axial elongation. This paper addresses the problem of axial elongation. The neutral axis in pipes after bending will shift down the central line axis and this is called neutral axis shift (NAS). The majority of the elongation occurs due to neutral axis shift (NAS). This shift is very much considerable in predicting the elongations particularly in large diameter pipes and with smaller relative bending ratio. A method to predict elongations analytically during pipe bending is given and compared with FEM results.