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TECHNICAL PAPERS

Determination of Proper Temperature Distribution for Warm Forming of Aluminum Sheet Materials

[+] Author and Article Information
Hong Seok Kim, Jun Ni

S. M. Wu Manufacturing Research Center, College of Engineering, University of Michigan, 2250 G. G. Brown Building, 2350 Hayward Street, Ann Arbor, MI 48109

Muammer Koc1

S. M. Wu Manufacturing Research Center, College of Engineering, University of Michigan, 2250 G. G. Brown Building, 2350 Hayward Street, Ann Arbor, MI 48109mkoc@umich.edu

1

To whom correspondence should be addressed.

J. Manuf. Sci. Eng 128(3), 622-633 (Nov 09, 2005) (12 pages) doi:10.1115/1.2162913 History: Received December 16, 2004; Revised November 09, 2005

In warm forming of aluminum sheet materials, determination, realization, and maintenance of optimal temperature gradient is a key process parameter for increased formability. In this study, a two-phase procedure for efficient and accurate determination of proper temperature condition for warm forming of aluminum sheet metal blanks is presented using a hybrid 3D isothermal/non-isothermal finite element analysis (FEA) and design of experiments (DOE) approach. First, the relative trend, priority and overall temperature ranges of aluminum sheet metal blank regions are obtained using isothermal FE modeling and DOE techniques to reduce the analysis time significantly. In this phase, different temperature levels were assigned onto different regions of the deforming blank material (i.e., holding region, corner region, etc.). Heat transfer with the tooling and environment during the deformation process is ignored in order to achieve rapid predictions. Second, few additional non-isothermal FEAs, taking heat transfer into account, are conducted to validate and to refine the warm forming conditions based on the results from the isothermal FEA/DOE analysis. The proposed hybrid methodology offers rapid and relatively accurate design of warm forming process, especially for large parts that require 3D FE analysis. In addition, effects of forming speed (v), friction (μ), and blank holder pressure on formability are investigated. Increasing part formability is observed with decreasing punch speed and blank holder pressure while an optimal process window is found in case of varying friction coefficients.

Copyright © 2006 by American Society of Mechanical Engineers
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Figures

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Figure 1

Isothermal and non-isothermal FEA models and design variables for warm forming of rectangular cups (a) isothermal FEA, (b) Non-isothermal FEA

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Figure 2

Response surface plots for the part depth values (mm) (a) T2 versus T4 (T6=350, T7=350°C), (b) T2 versus T6 (T4=25, T7=350°C), (c) T2 versus T7 (T4=25, T6=350°C), (d) T4 versus T6 (T2=25, T7=350°C), (e) T4 versus T7 (T2=25, T6=350°C), (f) T6 versus T7 (T2=25, T4=25°C)

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Figure 3

Part depth values from isothermal FEA and response surface at recommended and room temperatures

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Figure 4

Two mapping schemes from isothermal FEA to non-isothermal FEA, (a) recommended temperature distribution, (b) alternative temperature distribution

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Figure 5

Non-isothermal FEA results at recommended and alternative temperatures (refer to Fig. 4 for the detailed temperature condition of each case)

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Figure 6

Thickness strain distribution at two different mapping conditions of the tooling corner regions (μ=0.06; BHP=1.1MPa; v=10mm∕s), (a) CASE 1 in Fig. 4, (b) CASE 2 in Fig. 4

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Figure 7

Temperature distribution at two different mapping conditions of the tooling corner regions (μ=0.06; BHP=1.1MPa; v=10mm∕s), (a) CASE 1 in Fig. 4, (b) CASE 2 in Fig. 4

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Figure 8

Thickness strain and temperature distribution at alternative heating condition (heating condition=CASE 3 in Fig. 4; BHP=1.1MPa; v=10mm∕s), (a) thickness strain distribution, (b) temperature distribution

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Figure 9

Effect of punch speed (v) on formability at room and warm temperature conditions (μ=0.06; BHP=1.1MPa)

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Figure 10

Thickness strain distribution at two different punch speeds (μ=0.06; BHP=1.1MPa; heating condition=CASE 2 in Table 3), (a) v=5mm∕s, (b) v=20mm∕s

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Figure 11

Effect of blank holder pressure on formability at room and warm temperature conditions (μ=0.06; v=10mm∕s)

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Figure 12

Thickness strain distribution at two different BHPs (μ=0.06; v=10mm∕s; heating condition=CASE 1 in Table 3), (a) BHP=2.4MPa, (b) BHP=6MPa

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Figure 13

Effect of friction coefficient (μ) on formability at room and warm temperature conditions (BHP=1.1MPa; v=10mm∕s)

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Figure 14

Thickness strain distribution at two different friction coefficients (v=10mm∕s; BHP=1.1MPa; heating condition=CASE 2 in Table 3), (a) friction coefficient=0.1, (b) friction coefficient=0.5

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Figure 15

Effect of friction coefficient (μ) between punch and blank on formability at room and warm temperature conditions (friction coefficient between die and blank=0.06; BHP=1.1MPa; v=10mm∕s)

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Figure 16

Thickness strain distribution at two different friction coefficients between punch and blank (friction coefficient between die and blank=0.06; v=10mm∕s; BHP=1.1MPa; heating condition=CASE 2 in Table 3), (a) friction coefficient between punch and blank=0.1, (b) friction coefficient between punch and blank=0.2

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