Hot metal gas forming is a modern metal forming process which is generally utilized to manufacture automotive parts with complex shape and light-weight materials such as aluminum-magnesium alloys. One of the critical parameters in this approach is controlling the internal pressure of the tube during the hot forming process. The improvement of formability in tube hydroforming by utilizing pulsating pressure paths has been confirmed in the last few years. In this paper, the effect of the pulsating pressure on the hot tube gas bulging process has been investigated by experimental and numerical methods. In addition, an oscillating heating mechanism was used to provide a uniform temperature distribution along the tube. A novel, simple pneumatic system was designed and used to provide pressure paths. Moreover, the finite element simulation of hot tube gas bulging was carried out to investigate the effect of different parameters of pulsating pressure on tube formability and thickness distribution. The simulation and experimental results showed that the proposed pulsating pressure path improved formability and thickness distribution along the tube in the hot metal tube gas bulging process. It was also concluded that the axial feeding intensifies the effect of pulsating pressure on formability and it should be applied right after the start of the plastic deformation of the tube.

Experimental and numerical investigation of the influence of pulsating pressure on hot tube gas forming using oscillating heating

Magnesium alloys have been known as the next generation material for lightweight body structures. Pulsating hydroforming is an effective method to improve magnesium alloy sheet forming performance,...

Investigation on deformation behavior of magnesium alloy sheet AZ31B in pulsating hydroforming

Pulsating hydroforming is a novel forming technique that applies pulsating hydraulic pressure to deform tubular materials. Larger expansions and more uniform wall thicknesses in tubes have reported...

Describing tube formability during pulsating hydroforming using forming limit diagrams

Tube hydroforming (THF) is one of metal forming technologies which has been widely used to manufacture complex hollow workpeices. In THF, a variety of failures may occur and one of them is wrinkling. But recent researches show that wrinkling may be used as a preforming process to improve the formability of tubes. In this paper, a new geometry-based wrinkling indicator is proposed to evaluate the wrinkling level in THF and the wrinkle evolution diagram (WED) based on the shape change of the wrinkles is presented to display the four-stage evolution of the useful wrinkles. The wrinkling levels in THF with axial feeding under various loading paths are predicted respectively via finite element simulation, the influence of loading paths on the wrinkling behavior is investigated, and the evolving stages of the useful wrinkles is revealed via the proposed WED. The results indicate that the proposed wrinkle indicator can distinctly evaluate the wrinkling level, the wrinkling level under pulsating loading path is higher than that under polygonal linear one and four-stage evolution of the useful wrinkles could be evidently demonstrated via the WED. Notation

Research on Wrinkling Behavior in Tube Hydroforming with Axial Feeding

In the present study, the mechanical model of section element in tube bulging area was established through the stress conditions of hydraulic bulging. Based on the mechanical model, the equivalent stress and equivalent strain equations of the section element in the bulging area were derived, respectively. Combined with the experimental data, the equivalent stress and strain of the section element in the bulging area were fitted by polynomial, and the plastic hardening model of thin-walled tube under pulsating loading was obtained. In order to verify the model precision, the plastic hardening models obtained from pulsating hydroforming and non-pulsating hydroforming were taken as the material model by finite element simulation respectively. The experimental results were compared with the simulation results which showed that as a pulsating hydraulic loading material parameters, the model established in this paper had higher precision.

Investigation of the plastic hardening of metal thin-walled tube under pulsating hydraulic loading condition

M. LOH-MOUSAVI, M. BAKHSHI, K. MORI, T. MAENO, M. FARZIN AND S.J. HOSSEINIPOUR Dept. of Mechanical Engineering, Islamic Azad University (Khomeinishahr Branch), I. R. of Iran Email: loh-mousavi@iaukhsh.ac.ir Dept. of Mechanical Engineering, Mazandaran University, I. R. of Iran Dept. of Production Systems Engineering, Toyohashi University of Technology, Japan Dept. of Mechanical Engineering, Isfahan University of Technology, Isfahan, I. R. of Iran

S J Hosseinipour

Papers

3-D finite element simulation of pulsating free bulge hydroforming of tubes