Analysis of geometrical defects in overhang fabrications in electron beam melting based on thermomechanical simulations and experimental validations

Ghaoui, Soukaina; Ledoux, Yann; Vignat, Frédéric; Museau, Matthieu; Vo, Thanh Hoang; Villeneuve, François; Ballu, Alex

doi:10.1016/j.addma.2020.101557

Cited by 12 publications

(11 citation statements)

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“…Vo et al [ 44 ] proposed an explanation based on the decreasing magnitude of thermal shrinkage during cooling of consecutive overhang layers which is constrained by the growing stiffness of the underlying structure. Ghaoui et al [ 16 ] performed a thermo-mechanical simulation to validate this model and obtained a good agreement with experimental data. The thermo-mechanical origin of the observed effect is also indirectly confirmed by the simulation performed in the current investigation.…”

Section: Discussionmentioning

confidence: 82%

“…Cheng and Chou [ 13 ] applied a much more detailed FEA model to simulate the warping in overhang regions for a small number of layers [ 13 ] and the effect of an underlying support structure [ 14 , 15 ]. Ghaoui et al [ 16 ] developed a model to simulate the edge loss effect and achieved a good agreement with experimental data. In total, these more detailed simulations provided the opportunity to validate theoretical models for simple and small-scale geometries.…”

Section: Introductionmentioning

confidence: 84%

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Electron-Optical In Situ Imaging for the Assessment of Accuracy in Electron Beam Powder Bed Fusion

2021

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The current study evaluates the capabilities of electron-optical (ELO) in situ imaging with respect to monitoring and prediction of manufacturing precision in electron beam powder bed fusion. Post-process X-ray computed tomography of two different as-built parts is used to quantitatively evaluate the accuracy and limitations of ELO imaging. Additionally, a thermodynamic simulation is performed to improve the understanding of ELO data and to assess the feasibility of predicting dimensional accuracy numerically. It is demonstrated that ELO imaging captures the molten layers accurately (deviations <100 μm) and indicates the creation of surface roughness. However, some geometrical features of the as-built parts exhibit local inaccuracies associated with thermal stress-induced deformation (deviations up to 500 μm) which cannot be captured by ELO imaging. It is shown that the comparison between in situ and post-process data enables a quantification of these effects which might provide the possibility for developing effective countermeasures in the future.

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Section: Discussionmentioning

confidence: 82%

Section: Introductionmentioning

confidence: 84%

Electron-Optical In Situ Imaging for the Assessment of Accuracy in Electron Beam Powder Bed Fusion

2021

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“…From the comparison results, the following outcomes could be drawn: i) The microstructure of the L-PBF and E-PBF parts were not significantly affected by the specific part geometry: this result could be expected considering the principles of the two processes, for which the laser-matter interaction is almost independent from the intended geometry. As a matter of fact, part design features such as overhanging elements, high surface to volume ratio elements (e.g., lattice structures) and very thin walled elements are considered as source of parts properties heterogeneity, the latter intended in terms of microstructure, defects, hardness and so on [35][36][37][38]. On the other hand, despite this case study included a thinwalled structure, the overall mass of the part made it less sensitive to microstructure differentiation from the axisymmetric part.…”

Section: Effects Of the Part Geometry And Anisotropymentioning

confidence: 99%

Mechanical and microstructural characterization of titanium gr.5 parts produced by different manufacturing routes

Campanella¹,

Buffa²,

Hassanin³

et al. 2022

Preprint

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In recent years, the aircraft industry has shifted its preference for metal parts to titanium and its alloys, such as the high-strength Titanium Grade5 alloy. Because of Titanium Grade 5 limited formability at ambient temperature, forming operations on this material require high temperatures. In these conditions, a peculiar microstructure evolves as a result of the heating and deformation cycles, which has a significant impact on formability and product quality. On the other hand, additive manufacturing technologies, as selective laser melting and electron beam melting, are increasingly being used and are replacing more traditional approaches such as machining and forging. Fundamental parts characteristics as mechanical and microstructural properties, geometric accuracy and surface quality strongly depend on the selection of the manufacturing method. The authors of this paper seek to identify the strengths and limitations imposed by the intrinsic characteristics of different manufacturing alternatives for the production of parts of aeronautical significance, providing guidelines for the choice of the most appropriate manufacturing route for given application and part design.

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“…The shrinkage usually causes loss of the lower edges of parts as illustrated in Figure 3 (the left side of the part is fixed). From several experiments led by Vo et al (2018) and Ghaoui et al (2020) it has been inferred that the shrinkage of a layer is highly dependent on the number of layers above it. In fact, every deposited layer shrinks when solidifying and cooling.…”

Section: Minimize Shape Deformation Risks (Ar5)mentioning

confidence: 99%

Knowledge-Based Evaluation of Part Orientation Desirability in Powder Bed Fusion Additive Manufacturing

et al. 2021

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In powder bed fusion (PBF) additive manufacturing, the definition of part orientation is one of the most important steps as it affects the quality, the cost and the build time of products. Different works already attempted to propose methodologies for the assessment of optimal build orientation based on criteria such as the minimization of support volume. Elicitation works with industry experts have shown that they use much more varied rules to determine the orientation of parts. For instance, they do not treat the different surfaces of the part the same way (e.g., experts state that “priority surfaces of the part must be oriented close to vertical”). Today, the available tools do not allow integrating these kind of specifications. This paper discusses a knowledge-based methodology for the evaluation of part candidate orientations in PBF. Desirability function approach is used to translate companies’ expertise in the form action rules into mathematical functions that are tested on geometries to provide metrics for assisting the decision-making. A case study is presented to illustrate the use of this desirability function approach on complex part orientation problem.

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Analysis of geometrical defects in overhang fabrications in electron beam melting based on thermomechanical simulations and experimental validations

Cited by 12 publications

References 40 publications

Electron-Optical In Situ Imaging for the Assessment of Accuracy in Electron Beam Powder Bed Fusion

Electron-Optical In Situ Imaging for the Assessment of Accuracy in Electron Beam Powder Bed Fusion

Mechanical and microstructural characterization of titanium gr.5 parts produced by different manufacturing routes

Knowledge-Based Evaluation of Part Orientation Desirability in Powder Bed Fusion Additive Manufacturing

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