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Research Papers

An Experimental Study on Nonisothermal Deep Drawing Process Using Aluminum and Magnesium Alloys

[+] Author and Article Information
Serhat Kaya

Engineering Research Center for Net Shape Manufacturing (ERC/NSM), The Ohio State University, Columbus, OH 43210kaya.8@osu.edu

Giovanni Spampinato, Taylan Altan

Engineering Research Center for Net Shape Manufacturing (ERC/NSM), The Ohio State University, Columbus, OH 43210

J. Manuf. Sci. Eng 130(6), 061001 (Oct 09, 2008) (11 pages) doi:10.1115/1.2975228 History: Received February 15, 2007; Revised June 21, 2008; Published October 09, 2008

Weight reduction is one of the major goals in the automotive, appliance, and electronics industries. One way of achieving this goal is to use lightweight alloys such as aluminum and magnesium that have high strength to weight ratios. However, due to their limited formability at room temperature, forming needs to take place at elevated temperatures and mostly under nonisothermal conditions. In this study, nonisothermal deep drawing process using aluminum and magnesium alloys was investigated using a servo motor driven press and a heated tool set. Using the flexibility of the servo press kinematics, blanks were heated in the tool set prior to forming. Temperature-time measurements were made at various blank holder interface pressures in order to determine the required dwell time to heat the blank to the forming temperature. Several lubricants for elevated temperature forming were evaluated using the deep draw test, and a PTFE based film was found to be the best performing lubricant. Deep drawing tests were conducted to determine the process window (maximum punch velocity as functions of blank size and temperature) for Al 5754-O and Mg AZ31-O. Maximum punch velocities of 35 mm/s and 300 mm/s were obtained for the Al and Mg alloys, respectively. Comparisons for the Mg alloy sheets from two different suppliers were made and significant differences in formability were found. Experiments were conducted in order to understand the effect of constant and variable punch velocity and the temperature on the mechanics of deformation. Variable punch velocity is found to improve the thickness distribution of the formed part.

Copyright © 2008 by American Society of Mechanical Engineers
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References

Figures

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Figure 1

Schematic of the servo motor drive system (courtesy of Aida-America Corp.)

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Figure 2

Slide motion of the servo press in warm forming (top dead center (TDC) and bottom dead center (BDS))

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Figure 3

Schematic and the dimensions of the tool

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Figure 4

Warm forming process sequence

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Figure 5

Warm forming tooling (open condition)

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Figure 6

Fixture for dwell time measurements

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Figure 7

Interfaces affected from heat transfer and pressure

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Figure 8

Temperature-time curves obtained with the test fixture for different interface (blank holder) pressures (tool temperature=300°C)

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Figure 9

Effect of interface (blank holder) pressure upon temperature change in heating Al and Mg blanks

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Figure 10

Variations of cup wall thickness obtained with different lubricants (blank material Al 5754-O)

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Figure 11

Drawn cup with Lube A

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Figure 12

Variation of LDR with punch velocity (Mg AZ31-O, T=250°C)

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Figure 13

Variation of LDR with punch velocity (Mg AZ31-O, T=275°C)

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Figure 14

Variation of LDR with punch velocity (Mg AZ31-O, T=300°C)

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Figure 15

Process window for the Mg AZ31-O alloy

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Figure 16

Process window for the Al 5754-O alloy

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Figure 17

Punch and knockout pin temperatures at set temperatures of 250°C, 275°C, and 300°C

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Figure 18

Effect of temperature on thickness distribution (15 mm/s and draw ratio of 2.5)

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Figure 19

Effects of blank temperature and punch velocity on wall thinning at the bottom corner of the drawn cup for the Al 5754-O alloy

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Figure 20

Effect of temperature on thickness distribution (15 mm/s and DR of 2.5)

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Figure 21

Effects of blank temperature and punch velocity on thinning at the bottom corner of the drawn cup for the Mg AZ31-O alloy

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Figure 22

Change in cup bottom temperature at various constant punch velocities for Al

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Figure 23

Formed cups from Al5754-O (left) and MgAZ31-O (right)

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Figure 24

Fractured cups (from left to right Mg (at room temperature), Al, and Mg at elevated temperature

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Figure 25

Schematic of the “Critical Stroke” concept

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Figure 26

Effect of variable forming speed on the thickness distribution of Al cups

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Figure 27

Effect of variable forming speed on the thickness distribution of Mg cups

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