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Research Papers: Heat Transfer in Manufacturing

Comparison of Two-Dimensional and Three-Dimensional Thermal Models of the LENS® Process

[+] Author and Article Information
H. Yin

Mechanical Engineering Department, Mississippi State University, Mississippi State, MS 39762

L. Wang

Center for Advanced Vehicular Systems, Mississippi State University, Mississippi State, MS 39762

S. D. Felicelli

Mechanical Engineering Department, Mississippi State University, Mississippi State, MS 39762felicelli@me.msstate.edu

J. Heat Transfer 130(10), 102101 (Aug 08, 2008) (7 pages) doi:10.1115/1.2953236 History: Received May 24, 2007; Revised January 29, 2008; Published August 08, 2008

A new two-dimensional (2D) transient finite element model was developed to study the thermal behavior during the multilayer deposition by the laser engineered net shaping rapid fabrication process. The reliability of the 2D model was evaluated by comparing the results obtained from the 2D model with those computed by a previously developed three-dimensional (3D) model. It is found that the predicted temperature distributions and the cooling rates in the molten pool and its surrounding area agree well with the experiment data available in literature and with the previous results calculated with the 3D model. It is also concluded that, for the geometry analyzed in this study, the 2D model can be used with good accuracy, instead of the computationally much more expensive 3D model, if certain precautions are taken to compensate for the 3D effects of the substrate. In particular, a 2D model could be applied to an in situ calculation of the thermal behavior of the deposited part during the fabrication, allowing dynamic control of the process. The 2D model is also applied to study the effects of substrate size and idle time on the thermal field and size of the molten pool.

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Copyright © 2008 by American Society of Mechanical Engineers
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References

Figures

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Figure 1

(a) Sketch of the element activation to illustrate the laser powder deposition with multipasses, (b) schematic of the model showing the boundary conditions used for the temperature calculation, and (c) 3D model of Ref. 22

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Figure 2

Temperature distribution predicted (a) by the 2D model and (b) the 3D mode; molten pool is indicated by the 1450°C isotherm; (c) Comparison of calculated results by the 2D and 3D models and experimental data of Hofmeister (9)

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Figure 3

(a) Profiles of the A0 power coefficient of the 2D model and (b) temperature profiles calculated by the 2D and 3D models along the plate centerline for various scanning speeds of the laser beam

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Figure 4

Temperature distribution when the laser beam is at the center of layers 2, 4, 6, 8, and 10 calculated by the (a) 2D and (b) 3D models; the molten pool is indicated by the 1450°C isotherm. Temperature cycles at the midpoints of layers 1, 3, 5, and 10 as ten layers are deposited for the (c) 2D and (d) 3D models. V=7.62mm∕s. In (d), Ms is the martensite start temperature (350°C).

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Figure 5

Temperature distribution when the laser beam is at the center of the tenth layer as predicted by the (a) 2D model and (b) 3D model for V=2.50mm∕s. Temperature distribution when the laser beam is at the center of the tenth layer as predicted by the (c) 2D model and (d) 3D model for V=20.0mm∕s.

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Figure 6

(a) Temperature along the plate centerline for four different idle times after the tenth layer is deposited. (b) Temperature cycles at the midpoints of layers 1, 3, 5, and 10 calculated with the 2D model as ten layers are deposited. Idle time is 4.4s and travel speed V=2.5mm∕s.

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Figure 7

(a) Molten pool size and shape when the laser beam moves to the center of the part for layers 2, 4, 6, 8, and 10, with a substrate height of 2mm and (b) temperature along the plate centerline for four different substrate sizes

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