Research Article

Hot gas bulging of sealed aluminium alloy tube using resistance heating

Department of Mechanical Engineering, Toyohashi University of Technology, Toyohashi, Aichi 441-8580, Japan

^* e-mail: maeno@plast.me.tut.ac.jp

Received: 8 March 2014
Accepted: 25 April 2014

Abstract

A hot gas bulging process of a sealed aluminium alloy tube using resistance heating was developed to simplify a control scheme in gas forming. The tube is bulged by the decrease in flow stress of the tube and the increase in internal pressure of compressed air during resistance heating. Hot gas bulging of the sealed aluminium alloy tube without and with axial feeding was performed. The effects of the initial internal pressure and the current density on the expansion ratio of the tube were examined. The decrease in temperature around the contact with the electrode was prevented by inserting a stainless steel ring having low thermal conductivity and high heat generation between the copper electrode and tube, and thus the bulging length was increased. It was found that the amount of bulging can be controlled for the sealed tube by heating without control of internal pressure during forming.