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Research Papers

Thermomechanical Modeling of Additive Manufacturing Large Parts

[+] Author and Article Information
Erik R. Denlinger

Department of Mechanical and
Nuclear Engineering,
The Pennsylvania State University,
University Park, PA 16802
e-mail: erd5061@psu.edu

Jeff Irwin

Department of Mechanical and
Nuclear Engineering,
The Pennsylvania State University,
University Park, PA 16802
e-mail: jei5028@psu.edu

Pan Michaleris

Associate Professor
Department of Mechanical and
Nuclear Engineering,
The Pennsylvania State University,
University Park, PA 16802
President
Pan Computing LLC,
University Park, PA 16802
e-mail: pxm32@psu.edu

1Corresponding author.

Contributed by the Manufacturing Engineering Division of ASME for publication in the JOURNAL OF MANUFACTURING SCIENCE AND ENGINEERING. Manuscript received April 14, 2014; final manuscript received September 19, 2014; published online October 24, 2014. Assoc. Editor: David L. Bourell.

J. Manuf. Sci. Eng 136(6), 061007 (Oct 24, 2014) (8 pages) Paper No: MANU-14-1173; doi: 10.1115/1.4028669 History: Received April 14, 2014; Revised September 19, 2014

A finite element modeling strategy is developed to allow for the prediction of distortion accumulation in additive manufacturing (AM) large parts (on the order of meters). A 3D thermoelastoplastic analysis is performed using a hybrid quiet inactive element activation strategy combined with adaptive coarsening. At the beginning for the simulation, before material deposition commences, elements corresponding to deposition material are removed from the analysis, then elements are introduced in the model layer by layer in a quiet state with material properties rendering them irrelevant. As the moving energy source is applied on the part, elements are switched to active by restoring the actual material properties when the energy source is applied on them. A layer by layer coarsening strategy merging elements in lower layers of the build is also implemented such that while elements are added on the top of build, elements are merged below maintaining a low number of degrees of freedom in the model for the entire simulation. The effectiveness of the modeling strategy is demonstrated and experimentally validated on a large electron beam deposited Ti–6Al–4V part consisting of 107 deposition layers. The simulation and experiment show good agreement with a maximum error of 29%.

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References

Figures

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Fig. 3

Displacement magnitude results (mm) at the end of simulation for the uniformly fine baseline case of the small model

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Fig. 4

Displacement magnitude results (mm) at the end of simulation for the coarse case of the small model

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Fig. 5

Displacement magnitude at two different nodes versus time for both cases of the small model. The locations of these nodes are shown in Fig. 3. (a) Node 1 at free end of substrate and (b) node 2 between fifth and sixth layers

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Fig. 6

Displacement versus y location at end of simulation along line AA for both cases of the small model

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Fig. 2

Mesh 1 has a uniform density in the z direction. Element edges, which are subsequently eliminated by coarsening, are highlighted. (a) Mesh 1, (b) mesh 2, (c) mesh 3, and (d) mesh 4.

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Fig. 1

The mesh coarsening algorithm merges two layers of elements and deletes an entire plane of nodes. This is combined with a hybrid quiet inactive element activation method.

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Fig. 7

Large workpiece, deposited on 3810 mm long substrate, for model validation. (Figure provided by Sciaky, Inc.)

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Fig. 8

Illustration of the mesh used for layers 1–9. (a) Top view of mesh with mechanical constraints and (b) magnified isometric view of the mesh.

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Fig. 10

Displacement magnitude (mm) results after the model has been rotated to the same orientation as the scan results (2× magnification)

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Fig. 11

Top view of the coordinate system used for the simulated and experimental results (Figure provided by Neomek, Inc.)

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Fig. 9

Mechanical results (mm) after nine layers of deposition (a) while clamped in the fixture (b) after release of the clamps. Significant distortion can be seen after the release of the clamps (2× magnification).

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Fig. 12

Experimental and simulated distortion results in the x–z plane at y = 457 mm

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