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Research Papers

Prediction of Wrinkling and Determination of Minimum Blankholding Pressure in Multistage Deep Drawing

[+] Author and Article Information
Anupam Agrawal1 n2

Department of Mechanical Engineering,  Indian Institute of Technology Kanpur, Kanpur, 208 016, Indiaanupam@iitrpr.ac.in

N. Venkata Reddy

Department of Mechanical Engineering,  Indian Institute of Technology Kanpur, Kanpur, 208 016, Indianvr@iitk.ac.in

P. M. Dixit

Department of Mechanical Engineering,  Indian Institute of Technology Kanpur, Kanpur, 208 016, Indiapmd@iitk.ac.in

1

Present address: Assistant Professor, School of Mechanical, Materials and Energy Engineering, Indian Institute of Technology Ropar, Rupnagar Punjab, 140 001, India.

2

Corresponding author.

J. Manuf. Sci. Eng 133(6), 061023 (Dec 21, 2011) (8 pages) doi:10.1115/1.4004926 History: Received April 01, 2011; Revised August 19, 2011; Published December 21, 2011; Online December 21, 2011

Wrinkling in the flange region has been observed during redrawing operation by a few researchers. In the present work an analysis methodology, based on a combination of upper bound and energy approaches, is proposed for the prediction of number of wrinkles and minimum blankholding pressure necessary to avoid wrinkling in redrawing operation. Thickness variation predicted by the upper bound formulation is used as input for the wrinkling analysis by assuming a suitable waveform based on geometrical and process conditions. The flange is constrained at both ends, i.e., by the blank holder profile radius and at the die entry point (where the sheet enters into the die cavity). The waveform for present analysis is assumed such that it has zero displacement at both ends (since it is constrained) and the maximum amplitude of the wave at some point in between those ends. The wrinkling predicted by the present methodology seems to be reasonably accurate considering the geometrical and process constraints of the redraw.

Copyright © 2011 by American Society of Mechanical Engineers
Topics: Pressure , Thickness , Flanges
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References

Figures

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Figure 4

Assumed waveform and geometrical boundary conditions during redraw

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Figure 5

Variation of waveform in circumferential and radial directions during redraw

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Figure 15

Effect of initial sheet thickness (t0 ) on number of wrinkles

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Figure 16

Effect of initial sheet thickness (t0 ) on minimum blankholding pressure

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Figure 14

Effect of strain hardening exponent (n) on minimum blankholding pressure

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Figure 13

Effect of strain hardening exponent (n) on number of wrinkles

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Figure 12

Effect of normal anisotropy ratio (R¯) on minimum blankholding pressure

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Figure 11

Effect of normal anisotropy ratio (R¯) on number of wrinkles

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Figure 10

Minimum blankholding pressure predicted by present methodology to suppress wrinkles for the experimental tests conducted by Thiruvardchelvan and Travis [5] (AA1011H14, K = 180 MPa, n = 0.2, R¯=0.8, rp = 25 mm, rp1=22.5mm, ρp  = 5 mm, ρp1=3mm, ρd =5 mm, ρd1=3mm, t0  = 0.9 mm, R0  = 85.5 mm, and upunch  = 1 mm/s)

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Figure 9

Minimum blankholding pressure corresponding to different locations of r¯ of Fig. 6

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Figure 8

Minimum blankholding pressure required to suppress the wrinkles

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Figure 7

Number of wrinkles predicted by the present methodology

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Figure 6

Different locations of r¯

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Figure 3

Experimentally observed waveform during first draw

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Figure 2

Redraw cup shape with different zones marked

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Figure 1

Occurrence of wrinkling in flange region during redraw ([5])

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