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Open accessJournal ArticleDOI: 10.1038/S41598-021-84524-Y

Macro-, meso- and microstructural characterization of metallic lattice structures manufactured by additive manufacturing assisted investment casting.

02 Mar 2021-Scientific Reports (Nature Publishing Group)-Vol. 11, Iss: 1, pp 4974-4974
Abstract: Cellular materials are recognized for their high specific mechanical properties, making them desirable in ultra-lightweight applications. Periodic lattices have tunable properties and may be manufactured by metallic additive manufacturing (AM) techniques. However, AM can lead to issues with un-melted powder, macro/micro porosity, dimensional control and heterogeneous microstructures. This study overcomes these problems through a novel technique, combining additive manufacturing and investment casting to produce detailed investment cast lattice structures. Fused filament fabrication is used to fabricate a pattern used as the mold for the investment casting of aluminium A356 alloy into high-conformity thin-ribbed (~ 0.6 mm thickness) scaffolds. X-ray micro-computed tomography (CT) is used to characterize macro- and meso-scale defects. Optical and scanning electron (SEM) microscopies are used to characterize the microstructure of the cast structures. Slight dimensional (macroscale) variations originate from the 3D printing of the pattern. At the mesoscale, the casting process introduces very fine (~ 3 µm) porosity, along with small numbers of (~ 25 µm) gas entrapment defects in the horizontal struts. At a microstructural level, both the (~ 70 μm) globular/dendritic grains and secondary phases show no significant variations across the lattices. This method is a promising alternative means for producing highly detailed non-stochastic metallic cellular lattices and offers scope for further improvement through refinement of filament fabrication.

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5 results found

Open accessJournal ArticleDOI: 10.3390/MET11050725
28 Apr 2021-
Abstract: This work was supported by Fundacao para a Ciencia e a Tecnologia FCT under the research Doctoral Grant PD/BD/114096/2015, project UIDP/04077/2020 and UIDB/04436/2020, and Stimulus of Scientific Employment Application CEECIND/03991/2017.

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1 Citations

Journal ArticleDOI: 10.1016/J.MSER.2021.100648
Abstract: Lattice structures, which are also known as architected cellular structures, have been applied in various industrial sectors, owing to their fascinated performances, such as low elastic modulus, high stiffness-to-weight ratio, low thermal expansion coefficient, and large specific surface area. The lattice structures fabricated by conventional manufacturing technologies always involve complicated process control, additional assembly steps, or other uncontrollable factors. Furthermore, limited types of unit cells can be used to construct lattice structures when using conventional processes. Fortunately, additive manufacturing technology, based on a layer-by-layer process from computer-aided design models, demonstrates the unique capability and flexibility and provides an ideal platform in manufacturing complex components like lattice structures, resulting in an effective reduction in the processing time to actual application and minimum of material waste. Therefore, additive manufacturing relieves the constraint of structure design and provides accurate fabrication for lattice structures with good quality. This work systematically presents an overview of conventional manufacturing methods and novel additive manufacturing technologies for metallic lattice structures. Afterward, the design, optimization, a variety of properties, and applications of metallic lattice structures produced by additive manufacturing are elaborated. By summarizing state-of-the-art progress of the additively manufactured metallic lattice structures, limitations and future perspectives are also discussed.

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1 Citations

Journal ArticleDOI: 10.1007/S40195-021-01326-X
Naying An1, Sansan Shuai1, Tao Hu1, Chaoyue Chen1  +2 moreInstitutions (1)
Abstract: Additive manufacturing (AM) is a rapid prototyping technology based on the idea of discrete accumulation which offers an advantage of economically fabricating a component with complex geometries in a rapid design-to-manufacture cycle. However, various internal defects, such as balling, cracks, residual stress and porosity, are inevitably occurred during AM due to the complexity of laser/electron beam-powder interaction, rapid melting and solidification process, and microstructure evolution. The existence of porosity defects can potentially deteriorate the mechanical properties of selective laser melting (SLM) components, such as material stiffness, hardness, tensile strength, and fatigue resistance performance. Synchrotron X-ray imaging and diffraction are important non-destructive means to elaborately characterize the internal defect characteristics and mechanical properties of AM parts. This paper presents a review on the application of synchrotron X-ray in identifying and verifying the quality and requirement of AM parts. Defects, microstructures and mechanical properties of printed components characterized by synchrotron X-ray imaging and diffraction are summarized in this review. Subsequently, this paper also elaborates on the online characterization of the evolution of the microstructure during AM using synchrotron X-ray imaging, and introduces the method for measuring AM stress by X-ray diffraction (XRD). Finally, the future application of synchrotron X-ray characterization in the AM is prospected.

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Topics: Selective laser melting (55%), Synchrotron (52%)

Open accessJournal ArticleDOI: 10.1007/S11831-021-09669-5
Abstract: This paper aims to present a comprehensive review of the effect of embedding porosity and enhancing with carbon nanotube (CNT) on the vibrational behavior of composite structures. This type of material belongs to the famous family of composites materials that have promising mechanical properties that can be scientifically manipulated and gradually changed into the desired directions and orientations. Due to this varying, the composite properties give more flexible and huge applications in industrial processing materials. Functionally graded materials (FGM) with reinforced CNTs have attracted more researchers to hugely investigate and many publications have been done so far. This study will mainly focus on the effect of porosity and CNT on vibrations of composite structures. For CNTs reinforced composite, CNTs volume fraction effect, methods and methodologies applied by various researchers and types and different geometric shapes will be reviewed. Similarly, the researchers have examined the influence of porosity on to the vibrational behavior of composite materials. Porous materials are members of a novel class of lightweight materials and they are designed to have continuously changeable mechanical properties along a smooth and certain direction which could be provided through the introduction of a graded porosity distribution along the thickness direction of the plates. A comprehensive examination of the influence of porosity distribution, porosity coefficient, and geometric parameters of different materials will be discussed.

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Topics: Porosity (55%), Nanocomposite (51%), Composite number (51%) ... read more

86 results found

Open accessJournal ArticleDOI: 10.1038/NMETH.2019
01 Jul 2012-Nature Methods
Abstract: Fiji is a distribution of the popular open-source software ImageJ focused on biological-image analysis. Fiji uses modern software engineering practices to combine powerful software libraries with a broad range of scripting languages to enable rapid prototyping of image-processing algorithms. Fiji facilitates the transformation of new algorithms into ImageJ plugins that can be shared with end users through an integrated update system. We propose Fiji as a platform for productive collaboration between computer science and biology research communities.

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Topics: Software design (51%), Software (50%)

30,888 Citations

Open accessBook
Lorna J. Gibson1, Michael F. Ashby2Institutions (2)
01 Aug 1988-
Abstract: 1. Introduction 2. The structure of cellular solids 3. Material properties 4. The mechanics of honeycombs 5. The mechanics of foams: basic results 6. The mechanics of foams refinements 7. Thermal, electrical and acoustic properties of foams 8. Energy absorption in cellular materials 9. The design of sandwich panels with foam cores 10. Wood 11. Cancellous bone 12. Cork 13. Sources, suppliers and property data Appendix: the linear-elasticity of anisotropic cellular solids.

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Topics: Sandwich-structured composite (56%), Aluminium foam sandwich (52%), Metal foam (51%) ... read more

8,936 Citations

Journal ArticleDOI: 10.1016/S0079-6425(00)00002-5
John Banhart1Institutions (1)
Abstract: The possibilities for manufacturing metal foams or other porous metallic structures are reviewed. The various manufacturing processes are classified according to the state of matter in which the metal is processed — solid, liquid, gaseous or ionised. Liquid metal can be foamed directly by injecting gas or gas-releasing blowing agents, or by producing supersaturated metal–gas solutions. Indirect methods include investment casting, the use of space-holding filler materials or melting of powder compacts which contain a blowing agent. If inert gas is entrapped in powder compacts, a subsequent heat treatment can produce cellular metals even in the solid state. The same holds for various sintering methods, metal powder slurry foaming, or extrusion and sintering of polymer/powder mixtures. Finally, electro-deposition or metal vapour deposition also allow for the production of highly porous metallic structures. The various ways for characterising the properties of cellular metals are reviewed in second section of this paper. Non-destructive as well as destructive methods are described. Finally, the various application fields for cellular metals are discussed. They are divided into structural and functional applications and are treated according to their relevance for the different industrial sectors.

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Topics: Metal powder (62%), Blowing agent (60%), Metal foam (58%) ... read more

3,005 Citations

Journal ArticleDOI: 10.1016/J.ACTAMAT.2016.07.019
15 Sep 2016-Acta Materialia
Abstract: Additive Manufacturing (AM), the layer-by layer build-up of parts, has lately become an option for serial production. Today, several metallic materials including the important engineering materials steel, aluminium and titanium may be processed to full dense parts with outstanding properties. In this context, the present overview article describes the complex relationship between AM processes, microstructure and resulting properties for metals. It explains the fundamentals of Laser Beam Melting, Electron Beam Melting and Laser Metal Deposition, and introduces the commercially available materials for the different processes. Thereafter, typical microstructures for additively manufactured steel, aluminium and titanium are presented. Special attention is paid to AM specific grain structures, resulting from the complex thermal cycle and high cooling rates. The properties evolving as a consequence of the microstructure are elaborated under static and dynamic loading. According to these properties, typical applications are presented for the materials and methods for conclusion.

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Topics: Aluminium (50%)

1,782 Citations

Journal ArticleDOI: 10.1016/S0263-8223(96)00054-2
I.G. Masters1, Kenneth E. Evans1Institutions (1)
Abstract: A theoretical model has been developed for predicting the elastic constants of honeycombs based on the deformation of the honeycomb cells by flexure, stretching and hinging. This is an extension of earlier work based on flexure alone. The model has been used to derive expressions for the tensile moduli, shear moduli and Poisson's ratios. Examples are given of structures with a negative Poisson's ratio. It is shown how the properties can be tailored by varying the relative magnitudes of the force constants for the different deformation mechanisms. Off-axis elastic constants are also calculated and it is shown how the moduli and Poisson's ratios vary with applied loading direction. Depending on the geometry of the honeycomb the properties may be isotropie (for regular hexagons) or extremely anisotropic. Again, the degree of anisotropy is also affected by the relative magnitude of the force constants for the three deformation mechanisms.

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Topics: Deformation (engineering) (54%), Honeycomb structure (52%), Deformation mechanism (51%) ... read more

641 Citations

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