Modeling the Effect of Different Support Structures in Electron Beam Melting of Titanium Alloy Using Finite Element Models

Umer, Usama; Ameen, Wadea; Abidi, Mustufa Haider; Moiduddin, Khaja; Alkhalefah, Hisham; Alkahtani, Mohammed; Al-Ahmari, Abdulrahman

doi:10.3390/met9070806

Cited by 29 publications

(24 citation statements)

References 25 publications

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“…Repairing the STL file before 3D printing was a mandatory operation, because any faulty STL file could lead to geometric inaccuracies and a defective build [35]. Support structures were used to dissipate the heat and to assist in overhanging structures [36]. Moreover, Magics ® was also used for the orientation and best possible position during the build process to minimize the build time for the support structure.…”

Section: Stl Corrections and Support Generationsmentioning

confidence: 99%

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Patient-Specific Surgical Implant Using Cavity-Filled Approach for Precise and Functional Mandible Reconstruction

et al. 2020

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Mandibular reconstruction is a complicated task because of the complex nature of the regional anatomy. Computer-assisted tools are a promising means of improving the precision and safety of such complex surgeries. The digital techniques utilized in the reconstruction of mandibular defects based on medical data, computer-aided-design approaches, and three-dimensional (3D) printing are widely used to improve the patient’s aesthetic appearance and function, as well as the accuracy and quality of diagnosis, and surgical outcomes. Nevertheless, to ensure an acceptable aesthetical appearance and functional outcomes, the design must be based on proper anatomical reconstruction, mostly done in a virtual environment by skilled design engineers. Mirroring is one of the widely used techniques in the surgical navigation and reconstruction of mandibular defects. However, there are some discrepancies and mismatches in the mirrored anatomical models. Hence, in order to overcome these limitations in the mirroring technique, a novel approach called the cavity-filled technique was introduced. The objective of this study was to compare the accuracy of the newly recommended cavity-filled technique with the widely used mirror reconstruction technique in restoring mandibular defects. A prominent 3D comparison technique was employed in this work, where the resected and the reconstructed mandibles were superimposed to quantify the accuracy of the two techniques. From the analysis, it can be inferred that the cavity-filled technique with a root-mean-square value of 1.1019 mm produced better accuracy in contrast to the mirroring approach, which resulted in an error of 1.2683 mm. Consequently, by using the proposed cavity-filled design, the discrepancy between the reconstruction plate and the bone contour was mitigated. This method, owing to its high precision, can decrease the number of adjustments and the time of surgery, as well as ensure a quick recovery time with better implant tissue in-growth.

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Section: Stl Corrections and Support Generationsmentioning

confidence: 99%

“…Figure 8 illustrates the FDM machine and its fabricated original resected mandible with support structures. and to assist in overhanging structures [36]. Moreover, Magics was also used for the orientation and best possible position during the build process to minimize the build time for the support structure.…”

Section: Fdm Fabricationmentioning

confidence: 99%

Patient-Specific Surgical Implant Using Cavity-Filled Approach for Precise and Functional Mandible Reconstruction

et al. 2020

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“…The entire EBM build process takes place under vacuum and under elevated temperature. This is done to prevent reactions between reactive metals (titanium) with oxygen and to prevent residual stresses [38]. Figure 8a illustrates the fabricated titanium zygomatic implant with support structures.…”

Section: Implant Customization and Fabricationmentioning

confidence: 99%

Reconstruction of Complex Zygomatic Bone Defects Using Mirroring Coupled with EBM Fabrication of Titanium Implant

Moiduddin

Mian

Umer

et al. 2019

Metals

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Reconstruction of zygomatic complex defects is a surgical challenge, owing to the accurate restoration of structural symmetry as well as facial projection. Generally, there are many available techniques for zygomatic reconstruction, but they hardly achieve aesthetic and functional properties. To our knowledge, there is no such study on zygomatic titanium bone reconstruction, which involves the complete steps from patient computed tomography scan to the fabrication of titanium zygomatic implant and evaluation of implant accuracy. The objective of this study is to propose an integrated system methodology for the reconstruction of complex zygomatic bony defects using titanium comprising several steps, right from the patient scan to implant fabrication while maintaining proper aesthetic and facial symmetry. The integrated system methodology involves computer-assisted implant design based on the patient computed tomography data, the implant fitting accuracy using three-dimensional comparison techniques, finite element analysis to investigate the biomechanical behavior under loading conditions, and finally titanium fabrication of the zygomatic implant using state-of-the-art electron beam melting technology. The resulting titanium implant has a superior aesthetic appearance and preferable biocompatibility. The customized mirrored implant accurately fit on the defective area and restored the tumor region with inconsequential inconsistency. Moreover, the outcome from the two-dimensional analysis provided a good accuracy within 2 mm as established through physical prototyping. Thus, the designed implant produced faultless fitting, favorable symmetry, and satisfying aesthetics. The simulation results also demonstrated the load resistant ability of the implant with max stress within 1.76 MPa. Certainly, the mirrored and electron beam melted titanium implant can be considered as the practical alternative for a bone substitute of complex zygomatic reconstruction.

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“…Several approaches are aimed at reducing the computational effort. Umer et al [7] make use of dimensional reduction in their thermo-mechanical model to study the effect of different support structures in electron beam melting. A 2D model is not suitable for all geometries, and it will always introduce a loss of details in the problem.…”

Section: Introductionmentioning

confidence: 99%

History Reduction by Lumping for Time-Efficient Simulation of Additive Manufacturing

Malmelöv

Lundbäck

Lindgren

2019

Metals

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Additive manufacturing is the process by which material is added layer by layer. In most cases, many layers are added, and the passes are lengthy relative to their thicknesses and widths. This makes finite element simulations of the process computationally demanding owing to the short time steps and large number of elements. The classical lumping approach in computational welding mechanics, popular in the 80s, is therefore, of renewed interest and is evaluated in this work. The method of lumping means that welds are merged. This allows fewer time steps and a coarser mesh. It was found that the computation time can be reduced considerably, with retained accuracy for the resulting temperatures and deformations. The residual stresses become, to a certain degree, smaller. The simulations were validated against a directed energy deposition (DED) experiment with alloy 625.a thermo-mechanical model where whole layers were added simultaneously when a part with 50 layers was built. This model was validated against an experiment. Keller et al. [17,18] described a model where several layers were added simultaneously. With their model they were able to predict deformation and residual stresses at the macroscopic level. In the current work the temperature and deformation evolution is studied when the passes are added transiently, and only lumped in the build direction. To the authors' knowledge there is no publication where the approach has been used in this way. The inherent strain method is another approach for fast prediction of the resulting deformation and residual stress in AM processes [19,20]. The method was first proposed for welding by Ueda and coworkers [21][22][23]. Li et al. [24,25] used the inherent strain approach, but instead of using strain, a residual stress tensor is added to each layer in the mechanical macro-scale model. The simulation was performed with a multi-scale model in three different scales. A micro-scale model was used to predict an equivalent heat source, which was the input to the meso-scale model. Because the AM process is very fast, it was assumed that the heat could be added to the whole layer simultaneously. In the thermo-mechanical meso-scale model, a residual stress tensor from one added layer was calculated.Finally, the mechanical model on the macro-scale was computed, wherein the material was added layer by layer and the pre-determined residual stress tensor was applied on each added layer. The drawback with the inherent strain method is that it often requires calibration. The inherent strains are in general sensitive to changes in the boundary conditions.The main aim of this work was to study the method lumping of welds, described above, and evaluate the error introduced in the modeling and the achieved reduction in computation time for the simulations. A detailed thermo-mechanical FE model was validated with in situ temperature and displacement measurements for directed energy deposition (DED) with alloy 625. All experimental data and results that are used for comparison with the sim...

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Modeling the Effect of Different Support Structures in Electron Beam Melting of Titanium Alloy Using Finite Element Models

Cited by 29 publications

References 25 publications

Patient-Specific Surgical Implant Using Cavity-Filled Approach for Precise and Functional Mandible Reconstruction

Patient-Specific Surgical Implant Using Cavity-Filled Approach for Precise and Functional Mandible Reconstruction

Reconstruction of Complex Zygomatic Bone Defects Using Mirroring Coupled with EBM Fabrication of Titanium Implant

History Reduction by Lumping for Time-Efficient Simulation of Additive Manufacturing

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