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Research Papers

Tube Hydroforming of Magnesium Alloys at Elevated Temperatures

[+] Author and Article Information
Yeong-Maw Hwang1

Department of Mechanical and Electro-Mechanical Engineering, National Sun Yat-Sen University, Kaohsiung 804, Taiwanymhwang@mail.nsysu.edu.tw

Yan-Huang Su, Bing-Jian Chen

Department of Mechanical and Electro-Mechanical Engineering, National Sun Yat-Sen University, Kaohsiung 804, Taiwan

1

Corresponding author.

J. Eng. Mater. Technol 132(3), 031012 (Jun 24, 2010) (11 pages) doi:10.1115/1.4001833 History: Received September 02, 2008; Revised April 29, 2010; Published June 24, 2010; Online June 24, 2010

In this paper, a hydraulic forming machine with the functions of axial feeding, counter punch, and internal pressurization is designed and developed. This self-designed forming machine has a capacity of 50 tons for axial feeding and counter punch, 70 MPa for internal pressurization, and 300°C for forming temperature. Using this testing machine, experiments of T-shape protrusion of magnesium alloy AZ61 tubes at elevated temperatures are carried out. A commercial finite element code DEFORM 3D is used to simulate the plastic deformation of the tube within the die during the T-shape protrusion process. Different kinds of loading paths for the pressurization profile and the strokes of the axial feeding and the counterpunch are scheduled for analyses and experiments of protrusion processes at 150°C and 250°C. The numerical thickness distributions and the flow line configurations of the formed product are compared with the experimental results to validate this finite element modeling. The thickness distribution of the formed product or the flowability of AZ61 tubes at 150°C and 250°C is discussed. The effects of the forming rate on tube flowability at 250°C are also investigated. Through the observation of the flow line configurations of the tube material, adequate backward speeds of the counter punch relative to the axial feeding for preventing the material from accumulating at the die entrance region are verified. Finally, a sound product with a protrusion height of 49 mm is obtained.

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Copyright © 2010 by American Society of Mechanical Engineers
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Figures

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Figure 2

Relationship between the tube and punches

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Figure 3

Appearance of the warm hydraulic test machine

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Figure 4

Flow stresses used in the finite element simulations. (a) Stress-strain curves from tensile tests. (b) Actual flow stress input in the FEA.

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Figure 5

Mesh configurations of the tube before and after protrusion: (a) before forming and (b) after forming

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Figure 6

Loading path 1 and the formed product at 150°C: (a) loading path 1 and (b) appearance of the product

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Figure 7

Loading path 2 and the formed product at 150°C: (a) loading path 2 and (b) appearance of the product

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Figure 8

Thickness distribution of the product using loading path 2 at 150°C. (a) Thickness distribution at the upper portion. (b) Thickness distribution at the lower portion. (c) Longitudinal section view of the product.

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Figure 9

Loading paths used in T-shape protrusion experiments at 250°C: (a) loading path 1 and (b) loading path 2

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Figure 10

Experimental results of T-shape protrusion at 250°C. (a) Appearance of the products. (b) Thickness distributions of the products.

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Figure 11

Numerical and experimental results of T-shape protrusion at 250°C. (a) Thickness distribution at the upper portion. (b) Thickness distribution at the lower portion. (c) Longitudinal section view of the product.

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Figure 12

Loading path 3 and the formed product at 250°C. (a) Loading path 3. (b) Thickness distribution at the upper portion. (c) Thickness distribution at the lower portion. (d) Longitudinal section view of the product.

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Figure 13

Loading path 4 and the formed product at 250°C. (a) Loading path 4. (b) Appearance of the formed product.

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Figure 14

Flow line configurations of the tube material at different instances at 250°C using loading path 4. (a) When the counterpunch is ready to move. (b) When the counterpunch moved back 20 mm. (c) Completion of the forming process.

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Figure 1

Schematic diagram of the platform and the tooling set: (a) top view and (b) front view

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