Research Papers

Numerical Analysis on the Feasibility of Laser Microwelding of Metals by Femtosecond Laser Pulses Using ABAQUS

[+] Author and Article Information
Dongkyun Lee

Department of Mechanical Engineering, The University of Michigan, Ann Arbor, MI 48105-2125dongkyun@umich.

Elijah Kannatey-Asibu

Department of Mechanical Engineering, The University of Michigan, Ann Arbor, MI 48105-2125asibu@umich.edu

J. Manuf. Sci. Eng 130(6), 061014 (Nov 19, 2008) (12 pages) doi:10.1115/1.3006321 History: Received October 03, 2007; Revised August 22, 2008; Published November 19, 2008

Ultrafast lasers of subpicosecond pulse duration have the potential for laser microwelding of micronscale fusion zone. Due to the extremely short pulse duration, laser-metal interaction involving ultrafast laser pulses should be analyzed using the two-temperature model. In this study, the two-temperature model is analyzed using ABAQUS to study the feasibility of laser microwelding with ultrafast laser. A material model is constructed using material properties and the subsurface boiling model. The model is validated using experimental results from the literature. Laser processing parameters of repetition rate, pulse duration, and focal radius are then investigated, in terms of molten pool generated in the material and requirements on those parameters for laser microwelding using ultrafast lasers are discussed.

Copyright © 2008 by American Society of Mechanical Engineers
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Figure 1

A dual domain configuration for the TTM in ABAQUS

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Figure 7

(a) Ablation threshold fluence with respect to pulse duration. Experimental data set “Exp” taken from Ref. 18. (b) Ablation histories at the top surface for select pulse durations with J=4J∕cm2.

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Figure 8

(a) Maximum molten pool thickness with respect to input fluence for select pulse durations. (b) Corresponding molten pool thickness and ablation depth with respect to pulse duration.

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Figure 9

Lattice temperature distributions at selected times with fluence of 8J∕cm2 for pulse duration of (a) 1ps, and (b) 100ps; horizontal dot-dashed line in both figures represents the melting point

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Figure 10

(a) Difference between maximum electron and lattice temperature for select fluences with respect to pulse duration and corresponding relative time delay between electron and lattice maximum temperatures; in the figure, “Te,max” and “Tl,max” represent Te,max and Tl,max, respectively. (b) Comparison of temperature histories at the top and bottom surface evaluated from the TTM and conventional heat conduction model (denoted as “OTM” in the legend) for tp=5ns, J=8J∕cm2; in the figure, Te and Tl represent Te and Tl, respectively.

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Figure 11

(a) Axisymmetric 3D dual domain configuration, and (b) ablated top surface (z=0) profile for select focal radii and fluences. Note that unit length scales are different for depth and radius coordinates.

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Figure 12

Molten pool edge and top surface profile developed by a beam radius of rf=0.5μm at select times for (a) J=800mJ∕cm2 and tp=0.5ps, and for (b) J=400mJ∕cm2 and tp=500ps; comparison of molten pool edges developed by select beam focal radii at the times of maximum depths for (c) select fluences and tp=0.5ps, and (d) select pulse durations and J=400mJ∕cm2

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Figure 2

Overall workflow of ABAQUS user subroutines for the TTM implementation: USD stands for USDFLD, UMTH for UMATHT, and UMM for UMESHMOTION

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Figure 3

(a) Chemical potentials evaluated for DOS with s and d electrons and s electron only configurations, (b) curve-fitted G(Te) and Ce(Te) with original values; Ce(Te) of linear model (Ce=γ⋅Te) is also plotted. For the Te axis, “[X 1000K],” indicates that the number on the axis should be multiplied by 1000 for the exact value of K, i.e., “40” in (a) should read 40,000K.

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Figure 4

1D dual domain configuration of TTM implementation for ABAQUS

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Figure 5

(a) Ablation depth with respect to input fluence. Data set “Exp” taken from Ref. 16, and “CB” from Ref. 42. (b) Maximum molten pool thickness and ablation depth with respect to input fluence.

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Figure 6

(a) Lattice temperature histories at the top surface for select pulse repetition rates. (b) Maximum relative molten pool and ablation thicknesses with respect to repetition rates. In the figure, pulse duration is 500fs.




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