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RESEARCH PAPERS: Melting and Solidification

Thermal Behavior and Geometry Model of Melt Pool in Laser Material Process

[+] Author and Article Information
Lijun Han, Srinivas Musti

Department of Mechanical and Aerospace Engineering, University of Missouri-Rolla, Rolla, MO 65409, USA

Frank W. Liou1

Department of Mechanical and Aerospace Engineering, University of Missouri-Rolla, Rolla, MO 65409, USA

1

Corresponding author; E-mail address: liou@umr.edu

J. Heat Transfer 127(9), 1005-1014 (Apr 25, 2005) (10 pages) doi:10.1115/1.2005275 History: Received September 01, 2004; Revised April 25, 2005

Melt pool geometry and thermal behavior control are essential in obtaining consistent building performances, such as geometrical accuracy, microstructure, and residual stress. In this paper, a three dimensional model is developed to predict the thermal behavior and geometry of the melt pool in the laser material interaction process. The evolution of the melt pool and effects of the process parameters are investigated through the simulations with stationary and moving laser beam cases. The roles of the convection and surface deformation on the heat dissipation and melt pool geometry are revealed by dimensionless analysis. The melt pool shape and fluid flow are considerably affected by interfacial forces such as thermocapillary force, surface tension, and recoil vapor pressure. Quantitative comparison of interfacial forces indicates that recoil vapor pressure is dominant under the melt pool center while thermocapillary force and surface tension are more important at the periphery of the melt pool. For verification purposes, the complementary metal oxide semiconductor camera has been utilized to acquire the melt pool image online and the melt pool geometries are measured by cross sectioning the samples obtained at various process conditions. Comparison of the experimental data and model prediction shows a good agreement.

Copyright © 2005 by American Society of Mechanical Engineers
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References

Figures

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Figure 1

Experimental apparatus and setup

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Figure 2

Melt pool shape comparison between experimental data and simulation result with stationary laser beam

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Figure 3

Melt pool shape comparison between simulation and experiment with moving laser beam

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Figure 4

Cross section image of the fusion zone for different laser power levels at 300, 500, 750, and 1000 W

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Figure 5

Cross section image of the fusion zone for different process speeds at 10, 20, 30, and 40 ipm

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Figure 6

Melt pool velocity field and temperature distribution from the top view

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Figure 7

Melt pool velocity field and temperature distribution at cross section

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Figure 8

Comparison of melt pool geometry between simulation and experiment for different power levels at 300, 500, 750, and 1000 W

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Figure 9

Comparison of melt pool geometry between simulation and experiment for different process speeds at 10, 20, 30, and 40 ipm

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Figure 10

Surface temperature evolution with stationary laser beam

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Figure 11

Melt pool interfaces evolution with stationary laser beam

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Figure 12

Peclet number comparison at different laser power levels

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Figure 13

Melt pool ratio comparison between deformed surface case and flat surface case

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Figure 14

Force ratio of recoil vapor pressure to thermocapillary force at different times for 1250 W laser power level

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Figure 15

Force ratio of recoil vapor pressure to thermocapillary force at different laser power levels

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Figure 16

Force ratio of thermocapillary force to surface tension at laser power level 750 W

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