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Research Papers

Effect of Geometrical Modeling on the Prediction of Laser-Induced Heat Transfer in Metal Foam

[+] Author and Article Information
Tizian Bucher

Mem. ASME
Advanced Manufacturing Laboratory,
Department of Mechanical Engineering,
Columbia University,
New York, NY 10027
e-mail: tb2430@columbia.edu

Christopher Bolger

Advanced Manufacturing Laboratory,
Department of Mechanical Engineering,
Columbia University,
New York, NY 10027
e-mail: cdb2156@columbia.edu

Min Zhang

Mem. ASME
Laser Processing Research Center,
School of Mechanical and
Electrical Engineering,
Soochow University,
Suzhou, Jiangsu 215021, China
e-mail: mzhang@aliyun.com

Chang Jun Chen

Mem. ASME
Laser Processing Research Center,
School of Mechanical and
Electrical Engineering,
Soochow University,
Suzhou, Jiangsu 215021, China
e-mail: chjchen2001@aliyun.com

Y. Lawrence Yao

Fellow ASME
Advanced Manufacturing Laboratory,
Department of Mechanical Engineering,
Columbia University,
New York, NY 10027
e-mail: yly1@columbia.edu

1Corresponding author.

Manuscript received December 3, 2015; final manuscript received June 1, 2016; published online July 27, 2016. Assoc. Editor: Y. B. Guo.

J. Manuf. Sci. Eng 138(12), 121008 (Jul 27, 2016) (11 pages) Paper No: MANU-15-1637; doi: 10.1115/1.4033927 History: Received December 03, 2015; Revised June 01, 2016

Over the past several decades, aluminum foam (Al-foam) has found increasing popularity in industrial applications due to its unique material properties. Unfortunately, till date Al-foam can only be affordably manufactured in flat panels, and it becomes necessary to bend the foam to the final shape that is required in engineering applications. Past studies have shown that thin cell walls crack and collapse when conventional mechanical bending methods are used. Laser forming, on the other hand, was shown to be able to bend the material without causing fractures and cell collapse. This study was focused on the thermal aspects of laser forming of closed-cell Al-foam. An infrared camera was used to measure the transient temperature response of Al-foam to stationary and moving laser sources. Moreover, three different numerical models were developed to determine how much geometrical accuracy is needed to obtain a good agreement with experimental data. Different levels of geometrical complexity were used, including a simple solid geometry, a Kelvin-cell based geometry, and a highly accurate porous geometry that was based on an X-ray computed tomography (CT) scan. The numerical results were validated with the experimental data, and the performances of the numerical models were compared.

Copyright © 2016 by ASME
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References

Figures

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Fig. 1

Closed-cell Al-foam specimen after laser forming

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Fig. 2

(a) Equivalent model, (b) Kelvin-cell model, and (c) voxel model

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Fig. 3

Determining the equivalent thermal conductivity using the visual method by calculating the cross-sectional areas and the angular orientations of the cell walls

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Fig. 4

Experimental setup

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Fig. 5

Experimental and numerical temperature history response during steel sheet laser forming at 800 W—50 mm/s (high) and 400 W—25 mm/s (low)

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Fig. 6

(a) and (c) The experimental top and bottom temperature distributions, respectively, and (b) and (d) the numerical (Kelvin-cell) top and bottom temperature distributions, respectively, after a 2 s exposure to a 30 W laser with a 6 mm radius

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Fig. 7

(a) Experimental and (b) numerical (Kelvin-cell) temperature distribution from the laser center to the edge of the laser source after a 30 W laser exposure with a 6 mm radius. The experimental data are averaged over 15 specimens, and standard errors are shown.

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Fig. 8

(a) Experimental and (b) numerical (Kelvin-cell) temperature history plots during a 2 s exposure to a 30 W defocused laser beam with a 6 mm radius. The experimental data are averaged over 15 specimens, and standard errors are shown.

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Fig. 9

(a) and (c) The experimental top and bottom temperature history plots, and (b) and (d) the numerical (Kelvin-cell) top and bottom temperature history plots at scanning speeds 2.5 mm/s, 3.33 mm/s, and 5 mm/s, respectively. The laser power was 50 W with a beam radius of 6 mm. The experimental results were averaged over 20 test runs, and standard errors are shown.

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Fig. 10

Experimental and numerical (Kelvin-cell) maximum temperature gradients during 50 W scans with a 6 mm beam radius at 2.5 mm/s, 3.33 mm/s, and 5 mm/s, respectively. Standard errors are shown for the experimental data.

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Fig. 11

Typical color contours of the (a) equivalent model, (b) Kelvin-cell model, and (c) voxel model during a laser scan. Legends are omitted since the color contours are used for a qualitative comparison.

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Fig. 12

Heat flux vectors in cross sections of the (a) equivalent model, (b) Kelvin-cell model, and (c) voxel model during laser irradiation. Legends are omitted since the plots are used for a qualitative comparison.

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Fig. 13

Experimental and numerical (equivalent, Kelvin-cell, and voxel model) top and bottom surface temperature history plots during a 2 s laser pulse at 30 W with a defocused beam radius of 6 mm

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Fig. 14

Experimental and numerical (equivalent, Kelvin-cell, and voxel model) top temperature history plots during a 50 W scan at 5 mm/s with a defocused beam radius of 6 mm

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Fig. 15

Experimental and numerical (equivalent, Kelvin-cell, and voxel model) maximum top surface temperatures during 50 W laser scans at 2.5 mm/s, 3.33 mm/s, and 5 mm/s, respectively. Standard errors are shown for the experimental data.

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