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Research Papers

Transmission Welding of Glass by Femtosecond Laser: Mechanism and Fracture Strength

[+] Author and Article Information
Panjawat Kongsuwan

Department of Mechanical Engineering,  Columbia University, New York, NY 10027pk2261@columbia.edu

Gen Satoh

Department of Mechanical Engineering,  Columbia University, New York, NY 10027gs2358@columbia.edu

Y. Lawrence Yao

Manufacturing Research Laboratory, Department of Mechanical Engineering,  Columbia University, New York, NY 10027yly1@columbia.edu

J. Manuf. Sci. Eng 134(1), 011004 (Jan 11, 2012) (11 pages) doi:10.1115/1.4005306 History: Received April 01, 2011; Revised September 30, 2011; Published January 11, 2012; Online January 11, 2012

Femtosecond laser pulses were focused on the interface of two glass specimens. Proper use of optical and laser processing parameters enables transmission welding. The morphology of the weld cross section was studied using differential interference contrast optical microscopy. In addition, a numerical model was developed to predict the absorption volumes of femtosecond laser pulses inside a transparent material. The model takes into account the temporal and spatial characteristics and propagation properties of the laser beam, and the transmission welding widths were subsequently compared with the absorption widths predicted by the model. The model can lead to the achievement of a desirable weld shape through understanding the effects of laser pulse energy and numerical aperture on the shape of the absorption volume. The changes in mechanical properties of the weld seams were studied through spatially resolved nanoindentation, and indentation fracture analysis was used to investigate the strength of the weld seams.

Copyright © 2012 by American Society of Mechanical Engineers
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References

Figures

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Figure 1

Schematic illustration of experimental setup. The laser beam is focused onto the interface of two borosilicate glass plates, and the scanning direction is along the y-axis.

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Figure 2

Reflective DIC optical microscopy of cross section view (xz-plane) of a weld seam (laser pulse energy of 10 μJ, scanning speed of 0.02 mm/s, and repetition rate of 1 kHz)

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Figure 3

(a) 3D AFM topography on the cross section (xz-plane) of a weld seam (laser pulse energy of 10 μJ and scanning speed of 0.02 mm/s) and (b) AFM line profiles across glass interface near and on the weld seam

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Figure 4

Reflective DIC optical microscopy of cross section view (xz-plane) of a multiple-line weld seam (laser pulse energy of 10 μJ, scanning speed of 0.02 mm/s, and repetition rate of 1 kHz, 5 scanning lines with 6 μm spacing between lines)

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Figure 5

(a) Top view (xy-plane) and (c) cross section view (xz-plane) of weld seams performed at different processing conditions obtained through transmission DIC optical microscopy (laser scanning speed of 0.06 mm/s, 0.04 mm/s, 0.03 mm/s, and 0.02 mm/s, respectively, from the left) (b) Top view (xy-plane) and (d) cross section view (xz-plane) of a weld seam for 10 μJ and 0.02 mm/s condition

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Figure 6

Comparison of experimental weld width and simulated absorption width at different laser pulse energies. Error bars denote standard deviation.

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Figure 7

Schematic diagram of absorption volume modeling process

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Figure 8

(a) Cross section view (b) height, width, and height/width ratio of modeling absorption volume at different laser pulse energies (NA 0.6)

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Figure 9

(a) Cross section view (b) height, width, and height/width ratio of modeling absorption volume at different NAs (laser pulse energy of 20 μJ)

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Figure 10

Reflective DIC optical image of spatially resolved nanoindentation array (100 nm deep indents with 3 μm spacing) on the cross section (xz-plane) of a weld seam (laser pulse energy of 10 μJ and scanning speed of 0.02 mm/s)

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Figure 11

Spatially resolved determination of the ratio between Young’s modulus and hardness (E/H) on the cross section of (a) a welded region of two-piece specimen (b) a feature inside one-piece specimen using the same laser pulse energy of 10 μJ and scanning speed of 0.02 mm/s. The contour maps correspond to the array of 100 nm depth nanoindents with 3 μm spacing.

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Figure 12

The variation of E/H ratio (b) versus X-position along the horizontal lines (lines H1–H3) in Fig. 1 across the weld seam (b) versus Y-position along the line C1 in Fig. 1 across the weld seam and the line C2 in Fig. 1 across the feature inside one-piece specimen (laser pulse energy of 10 μJ, scanning speed of 0.02 mm/s)

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Figure 13

Reflective DIC optical microscopy of indentation fracture on cross section (xz-plane) of a weld seam (laser pulse energy of 30 μJ, scanning speed of 0.02 mm/s, repetition rate of 1 kHz)

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Figure 14

Fracture Toughness of the material in welded regions with different laser pulse energy levels (10 μJ–30 μJ) at fixed laser scanning speed of 0.02 mm/s and in a reference region from indentation fracture measurements at different loads. Error bars denote standard deviation.

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Figure 15

Fracture Strength as a function of crack size of the material in welded regions with different laser pulse energy levels (10 μJ–30 μJ) at fixed laser scanning speed of 0.02 mm/s and in a reference region

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