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Research Papers

Temperature-Controlled Forming of 7075-T6 Aluminum Using Linearly Decaying Direct Electric Current

[+] Author and Article Information
Brandt J. Ruszkiewicz

Clemson’s International Center for
Automotive Research,
Greenville, SC 29607

Laine Mears

Clemson’s International Center for
Automotive Research,
Greenville, SC 29607
e-mail: mears@clemson.edu

Manuscript received November 29, 2015; final manuscript received June 9, 2016; published online August 3, 2016. Assoc. Editor: Rajiv Malhotra.

J. Manuf. Sci. Eng 138(9), 091009 (Aug 03, 2016) (9 pages) Paper No: MANU-15-1615; doi: 10.1115/1.4033902 History: Received November 29, 2015; Revised June 09, 2016

7075-T6 aluminum suffers from limited elongation during tensile forming; electrically assisted forming (EAF), which uses direct current to improve formability, is a viable candidate process to improve this effect. In past electrical tension testing by various authors, two types of waveforms have been examined: continuous current and square waveforms. For tension, it was shown that the applying current using square waveforms was able to extend formability beyond what continuous current could do, due to reducing the overheating in the necking region. The goal of this paper is to model the temperature and flow stress effects of saw tooth waves by modifying an existing square wave temperature prediction model and combining it with a theoretical flow stress model. Nondecaying and linearly globally decaying saw tooth waveforms are used in an attempt to control the temperature of the necking zone to allow for increased strain at fracture. Comparisons between saw tooth waveforms and square waveforms are exhibited, and it is found that the saw tooth waveforms are inferior to square waves for increasing strain at fracture for 7075-T6.

Copyright © 2016 by ASME
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References

Figures

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Fig. 1

Square wave true stress/true strain plot

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Fig. 2

Nodal configuration for electrically assisted temperature model from Ref. [25]

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Fig. 3

Testing setup for electrically assisted tension

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Fig. 4

Waveform parameters

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Fig. 5

Example of globally linear decaying and normal saw tooth waveforms

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Fig. 6

Square wave and baseline maximum temperature profiles

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Fig. 7

Square wave test specimens from top to bottom: baseline, SQ1D60P, and SQ3D60P

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Fig. 8

Saw tooth wave true stress/true strain plot

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Fig. 9

Saw tooth wave maximum temperature profiles

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Fig. 10

Saw tooth wave specimens, from top to bottom: baseline, ST5D60P, ST7.5D60P, and ST5D45P

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Fig. 11

Globally linear decaying saw tooth wave true stress/true strain plot

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Fig. 12

Globally linear decaying saw tooth wave maximum temperature profiles

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Fig. 13

Globally linear decaying saw tooth waveform specimens, from top to bottom: baseline, STG5D60P, STG7.5D60P, and STG5D45P

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Fig. 14

Square wave versus saw tooth waves true stress/true strain plot

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Fig. 15

Square wave versus saw tooth wave maximum temperature profiles

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Fig. 16

Waveform comparison specimens, from top to bottom: baseline, SQ3D60P, ST5D45P, and STG5D45P

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Fig. 17

Thermal model compared to experimental data for, from top to bottom, SQ3D60P, ST5D60P, and STG5D45P

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Fig. 18

Model and experimental data comparison for, from top to bottom, baseline, SQ3D60P, ST5D60P, and STG5D45P

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