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Research Papers

Investigations on Deformation Behavior of AA5754 Sheet Alloy Under Warm Hydroforming Conditions

[+] Author and Article Information
S. Mahabunphachai

National Metal and Materials Technology Center (MTEC), Pathumthani, Thailand 12120; NSF I/UCR Center for Precision Forming,  Virginia Commonwealth University, VA 23284

M. Koc1

Department of Industrial Engineering, Istanbul Sehir University, Uskudar, Istanbul 34662, Turkey; NSF I/UCR Center for Precision Forming,  Virginia Commonwealth University, VA 23284koc.muammer@gmail.com

J. E. Carsley

 General Motors Research & Development Center, Warren, MI 48090

1

Corresponding author.

J. Manuf. Sci. Eng 133(5), 051007 (Oct 12, 2011) (10 pages) doi:10.1115/1.4004924 History: Received October 28, 2010; Revised July 16, 2011; Published October 12, 2011; Online October 12, 2011

Material behavior of AA5754 was investigated under different forming process conditions, including two loading conditions (uniaxial tensile and biaxial bulge), several strain rates (constant strain rates at 0.0013 and 0.013/s, and variable strain rate profiles: increasing and decreasing profiles), and several temperature levels (ambient up to 260 °C). Additional warm hydroforming experiments were conducted using a closed-die set up to understand the forming limits of AA5754. The results from tensile and hydraulic bulge tests as well as closed-die hydroforming experiments suggested that, in general, formability of AA5754 can be significantly improved with slow forming rates (<0.02/s), high forming temperature (>200 °C), and biaxial loading (hydroforming) that can delay strain localization (necking). However, the effect of forming rate did not reveal any significant gain in formability for temperatures below 200 °C. The effect of variable strain rate control was found to be significant only at elevated temperatures (>200 °C), where increasing strain rate resulted in lower formability and decreasing strain rate improved the maximum attainable dome height at temperatures above 200 °C. Finally, the material flow curves obtained from the tensile and bulge tests were shown to provide reasonably accurate predictions for cavity filling ratios (∼ 3–15% error) in finite element analyses.

Copyright © 2011 by American Society of Mechanical Engineers
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References

Figures

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Figure 1

Flow stress curves obtained from tensile tests of AA5754 at 0 deg, 45 deg, and 90 deg to the rolling direction of the sheet

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Figure 2

Samples of bulged specimens

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Figure 3

Flow stress curves obtained from bulge tests of AA5754

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Figure 4

Comparison of flow stress curves obtained from tensile and bulge tests at (a) strain rate of 0.0013/s, and (b) strain rate of 0.013/s

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Figure 5

(a) Increasing strain rate and (b) decreasing strain rate profiles used in the bulge tests with varying strain rate conditions

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Figure 6

Comparisons of maximum attainable dome height under different strain rate schemes

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Figure 7

Biaxial flow curves with variable strain rates at (a) 23 °C, (b) 150 °C, and (c) 200 °C

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Figure 8

Geometries of nonaxisymmetric dies (dimensions in mm)

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Figure 9

Hydroformed specimens at different temperatures and pressures

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Figure 10

Typical 2D profiles A and B of hydroformed specimens

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Figure 11

Cavity filling ratios of closed-die hydroformed parts under different P and T conditions

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Figure 12

Cut specimens and measurement locations

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Figure 13

Thickness distribution of hydroformed specimens at different conditions

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Figure 14

Hydroformed specimens at different pressurization rates. Top parts are with a PR of 0.22 MPa/s while bottom parts are with a PR of 0.022 MPa/s where sharper corners and features are more visible.

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Figure 15

Effect of pressurization rate on CFR

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Figure 16

Effect of pressurization rate on thickness distribution

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Figure 17

Finite element model

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Figure 18

Total equivalent plastic strain distribution at (left) 150 °C–20 MPa, and (right) 260 °C–30 MPa based on bulge flow curve

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Figure 19

Comparisons of profile A at different test conditions

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