Teses / dissertações: "DED metal additive manufacturing"

1

TESTA, Cristian (ORCID:0000-0002-6064-9851). "Corrosion behaviour of metal alloys obtained by means of additive manufacturing". Doctoral thesis, Università degli studi di Bergamo, 2020. http://hdl.handle.net/10446/181512.

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Kaya, Fuat Emre. "Applications of Additive Manufacturing in Construction and Historic Building Restoration/Rehabilitation". Master's thesis, Alma Mater Studiorum - Università di Bologna, 2021. http://amslaurea.unibo.it/22784/.

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The term “Additive Manufacturing” is described as the layered production of parts from a 3D file. Over the past century, this technology has evolved from a complement tool for conventional product development into an independent production method. Whereas high technology industries such as aerospace and medicine were already embraced additive manufacturing, structural engineering and architecture are lagging. Additive manufacturing has the potential to revolutionize the construction and restoration of historic buildings, with foreseeable benefits including highly complex and efficient structures with the reduction in material use and wastage, streamlining and expedition of the design-build process, improved customization. However, there are also challenges and demands: a new way of thinking for design and verifications for stability and serviceability of printed elements, the cost, the need for well-educated engineers. In this dissertation, the current state of additive manufacturing in construction and historic building restoration/rehabilitation is reviewed as a combination of qualitative and quantitative-based studies. The research aims to give confidence to additive manufacturing applicability in these fields and stimulate further research. The opportunities and challenges are discussed by analysing concrete, polymer, and metal-based processes and their applications of additive manufacturing in the construction sector. A review of structural and non-structural applications in restoration projects, possible future applications in terms of structural strengthening are analysed and opportunities and challenges are identified and discussed. Based on the literature review and experimental lab tests, the outcome was obtained as the tensile mechanical properties are adequate for structural engineering applications. However, further interdisciplinary research on additive manufacturing is necessary to build confidence in structural engineers and architects.

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3

Schneider-Maunoury, Catherine. "Application de l’injection différentielle au procédé de fabrication additive DED-CLAD® pour la réalisation d’alliages de titane à gradients de compositions chimiques". Thesis, Université de Lorraine, 2018. http://www.theses.fr/2018LORR0260/document.

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Depuis 1984, les matériaux à gradients de fonction (FGM) permettent de former une barrière thermique et réduire les fortes discontinuités des propriétés entre deux matériaux de nature différente. Ces multi-matériaux, qui consistent en une variation intentionnelle de la composition chimique entrainant par conséquent une modification des propriétés microstructurales, chimiques, mécaniques et thermiques, permettent de lisser la distribution des contraintes thermiques. L’élaboration in situ de ces alliages sur mesure est rendu possible grâce à l’utilisation de procédés de fabrication additive tel que le procédé par dépôt de poudres DED-CLAD®. Ces procédés connaissent un essor considérable depuis les années 1980 et sont idéaux dans la fabrication de FGM. Dans le cadre de cette thèse CIFRE, des développements techniques ont été effectués pour adapter le procédé DED-CLAD® et permettre la réalisation de FGM. Grâce à plusieurs collaborations industrielles, une étude complète a été réalisée sur les alliages titane-molybdène et titane-niobium. Ces alliages permettent dans le premier cas de réaliser des pièces résistantes à de fortes sollicitations thermiques (secteur spatial), et dans le second cas d’associer les propriétés mécaniques et la biocompatibilité (secteur biomédical). L’originalité de cette thèse repose sur l’étude d’un gradient complet, c’est-à-dire que l’ajout en élément d’alliage varie de 0% à 100%. En effet, les études reportées dans la littérature ne font pas mentions des alliages titane-matériaux réfractaire pour des taux élevés en élément réfractaire. Les analyses microstructurale (DRX, structure cristallographique par EBSD, microstructure), chimique (EDS) et mécanique (microdureté, tests de traction et essais d’indentation instrumentée) ont mis en évidence une évolution des propriétés le long du gradients de composition. La caractérisation mécanique des échantillons par indentation instrumentée s’est par ailleurs révélée particulièrement pertinente dans les cas de ces multi-matériaux
Since 1984, the Functionally Graded Material (FGM) allow to create a thermal barrier and to reduce the strong discontinuities of properties between two materials of different composition. These multimaterials,whose consist of an intentional variation in the chemical composition and, consequently, modify the microstructural, chemical, mechanical and thermal properties, lead to a smooth distribution of the thermal stress. The in-situ development of these custom-made alloys is made possible by the use of additive manufacturing processes such as the DED-CLAD® powder deposition process. These processes have grown substantially since the 1980s and are optimal for the manufacture of FGM. During this industrial thesis, technical developments have been carried out to adapt the DED-CLAD® process and to allow the manufacturing of FGM. Thanks to two industrial collaborations, a full study was carried out on titanium-molybdenum and titanium-niobium alloys. These alloys make it possible, in the first case, to produce parts resistant to strong thermal stress (space sector), and in the second case to combine mechanical properties and biocompatibility (biomedical sector). The originality of this thesis rests on the study of a complete gradient, that is the addition in alloy element varied from 0% to 100%. In fact, studies reported in the literature do not mention titanium-refractory material for high levels of refractory element. Microstructural (XRD, crystallographic analysis by EBSD technique), chemical (EDS) and mechanical (microhardness, tensile test and instrumented indentation) analyses revealed an evolution of the properties along the chemical gradient. The mechanical characterization of the sample by instrumented indentation has also proved particularly relevant in the case of these multi-materials

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Vandi, Daniele. "Studio del comportamento a fatica di provini in Maraging steel realizzati tramite Additive Manufacturing". Bachelor's thesis, Alma Mater Studiorum - Università di Bologna, 2019.

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Nel presente lavoro di tesi verrà studiato ed analizzato, tramite prove effettuate in laboratorio, il comportamento a fatica di 3 set di provini metallici in Maraging steel, realizzati mediante le più moderne tecnologie di Additive Manufacturing. Tale recente tecnologia, pioniera nell'ambito della produzione manifatturiera di prototipi e pezzi, ha iniziato sin dagli inizi del suo sviluppo a mostrare le sue numerose potenzialità, e solo negli ultimi anni ha dimostrato di poter essere applicata con successo anche a componenti meccanici e parti funzionali. Ciononostante, data la modernità della tecnologia, sono richieste ulteriori ricerche ed analisi per determinare il comportamento meccanico di pezzi prodotti con tali tecnologie, in quanto la loro resistenza, statica e soprattutto a fatica, è influenzata dalla peculiarità del processo tecnologico stesso, che tende a generare forte anisotropia nelle leghe metalliche prodotte. Nella prima parte verranno discussi i fondamenti generali della meccanica per i materiali metallici, in particolare il comportamento dei materiali sottoposti a storie di carico variabile; nella seconda parte verrà presentato uno stato dell'arte dei vari processi di Additive Manufacturing; nella terza parte, verrà studiato il comportamento a fatica, ad alto numero di cicli, dei suddetti provini sottoposti da un macchinario a flessione rotante a vari livelli di carico; nella quarta parte, tramite uso di tecniche statistiche, verrà presentata un'elaborazione dei risultati ottenuti in laboratorio, in particolare per ricavare la curva S-N e il limite di fatica del materiale; infine verrà presentata l'osservazione al microscopio delle superfici di frattura dei provini, per indagare la propagazione della rottura e così risalire alle possibili cause iniziatrici della rottura stessa.

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Schneider-Maunoury, Catherine. "Application de l’injection différentielle au procédé de fabrication additive DED-CLAD® pour la réalisation d’alliages de titane à gradients de compositions chimiques". Electronic Thesis or Diss., Université de Lorraine, 2018. http://www.theses.fr/2018LORR0260.

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Depuis 1984, les matériaux à gradients de fonction (FGM) permettent de former une barrière thermique et réduire les fortes discontinuités des propriétés entre deux matériaux de nature différente. Ces multi-matériaux, qui consistent en une variation intentionnelle de la composition chimique entrainant par conséquent une modification des propriétés microstructurales, chimiques, mécaniques et thermiques, permettent de lisser la distribution des contraintes thermiques. L’élaboration in situ de ces alliages sur mesure est rendu possible grâce à l’utilisation de procédés de fabrication additive tel que le procédé par dépôt de poudres DED-CLAD®. Ces procédés connaissent un essor considérable depuis les années 1980 et sont idéaux dans la fabrication de FGM. Dans le cadre de cette thèse CIFRE, des développements techniques ont été effectués pour adapter le procédé DED-CLAD® et permettre la réalisation de FGM. Grâce à plusieurs collaborations industrielles, une étude complète a été réalisée sur les alliages titane-molybdène et titane-niobium. Ces alliages permettent dans le premier cas de réaliser des pièces résistantes à de fortes sollicitations thermiques (secteur spatial), et dans le second cas d’associer les propriétés mécaniques et la biocompatibilité (secteur biomédical). L’originalité de cette thèse repose sur l’étude d’un gradient complet, c’est-à-dire que l’ajout en élément d’alliage varie de 0% à 100%. En effet, les études reportées dans la littérature ne font pas mentions des alliages titane-matériaux réfractaire pour des taux élevés en élément réfractaire. Les analyses microstructurale (DRX, structure cristallographique par EBSD, microstructure), chimique (EDS) et mécanique (microdureté, tests de traction et essais d’indentation instrumentée) ont mis en évidence une évolution des propriétés le long du gradients de composition. La caractérisation mécanique des échantillons par indentation instrumentée s’est par ailleurs révélée particulièrement pertinente dans les cas de ces multi-matériaux
Since 1984, the Functionally Graded Material (FGM) allow to create a thermal barrier and to reduce the strong discontinuities of properties between two materials of different composition. These multimaterials,whose consist of an intentional variation in the chemical composition and, consequently, modify the microstructural, chemical, mechanical and thermal properties, lead to a smooth distribution of the thermal stress. The in-situ development of these custom-made alloys is made possible by the use of additive manufacturing processes such as the DED-CLAD® powder deposition process. These processes have grown substantially since the 1980s and are optimal for the manufacture of FGM. During this industrial thesis, technical developments have been carried out to adapt the DED-CLAD® process and to allow the manufacturing of FGM. Thanks to two industrial collaborations, a full study was carried out on titanium-molybdenum and titanium-niobium alloys. These alloys make it possible, in the first case, to produce parts resistant to strong thermal stress (space sector), and in the second case to combine mechanical properties and biocompatibility (biomedical sector). The originality of this thesis rests on the study of a complete gradient, that is the addition in alloy element varied from 0% to 100%. In fact, studies reported in the literature do not mention titanium-refractory material for high levels of refractory element. Microstructural (XRD, crystallographic analysis by EBSD technique), chemical (EDS) and mechanical (microhardness, tensile test and instrumented indentation) analyses revealed an evolution of the properties along the chemical gradient. The mechanical characterization of the sample by instrumented indentation has also proved particularly relevant in the case of these multi-materials

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TREVISAN, FRANCESCO. "Study and characterisation of different metal alloys processed through Laser Powder Bed Fusion". Doctoral thesis, Politecnico di Torino, 2018. http://hdl.handle.net/11583/2709711.

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Additive Manufacturing (AM) techniques inspired a substantial revolution in the way of concept and produce metal components for industry. Among all the available AM processes, Laser Powder Bed Fusion (LPBF) inspired a noticeable series of investments, studies and standardisation routes since the great interested it acquired in several industrial sectors. In the past years numerous researchers demonstrated how this process produces metal components with innovative and unprecedented microstructures and mechanical properties, disclosing new horizons in the scientific and industrial research. This thesis took under investigation the study and characterisation of three different metal alloys, A357 aluminium alloy, Ti-6Al-4V titanium alloy and pure copper, respectively, all processed by LPBF. Furthermore, the investigation of different post-processing heat treatments was took under study. The processed samples, as well the metal powders used, were characterised by microscopic and macroscopic analyses. The study on A357 aluminium alloy processed by LPBF investigated the process parameters necessary to build full dense components for industrial applications. By correctly combining hatching distance and scanning speed it was possible to fabricate completely dense specimens keeping a good productivity rate. Moreover, the effects of different heat treatments on specimens microstructure and mechanical properties were studied. Particularly, a stress relieving and a subsequent T6 precipitation hardening treatment were performed on the full dense LPBF parts, investigating the effects of different temperatures and durations in the case of T6 treatment. Longer solution treatments enabled to obtain higher hardness values and to reduce the time required to reach peak hardening conditions during ageing. While stress relieving strongly softened the material, a maximum hardness comparable to as-built parts conditions was obtained after subsequent 8 h solution treatment, water quenching and 3 h ageing treatment. Stress reliving treatment slightly modified the as-built microstructure by favouring the diffusion of Si but did not removed the melt pool structures present, furthermore it noticeably increased the elongation at break to detriment of tensile strength. Further T6 treatment modified the tensile properties to values comparable with the as-built conditions eliminating melt pools anisotropic features. The study on Ti-6Al-4V titanium alloy investigated the microstructural, tensile and fatigue properties of the LPBF fabricated parts, produced with two different gas atomised powders. The two powders contained two level of oxygen inside the chemical composition, a low and a high amount, in order to simulate the LPBF processing of Ti-6Al-4V ELI and Ti-6Al-4V grade 5, respectively. Two different building orientations, vertical and horizontal, were chosen for the specimens fabrication and moreover three different testing conditions were considered: after stress relieving, after stress relieving plus heat treatment and after stress relieving plus Hot Isostatic Pressing (HIP). Processing a subsequent heat treatment after stress relieving reduced tensile strength and increased ductility by coarsening α + β lamellar structure while β columnar grains faded. HIP post-processing closed the major part of porosities and defects and enabled to greatly increase both ductility and fatigue resistance. Pores and defects were detected as the most influencing factors upon the fatigue properties, rather than building orientation and oxygen content, which mostly influenced tensile strength. Only stress relieved and HIPped samples resisted more than the chosen endurance limit of 107 cycles at high applied strength than the other specimens. The study carried out on pure copper investigated the feasibility of processing such material with LPBF using a commercial machine equipped with an infrared 200 W fibre laser. The specimens fabricated did not exceed the 83 % of density due to the low absorptivity of copper to infrared radiation, but Diffuse Reflectance Spectroscopy (DRS) analysis demonstrated how modifying the laser radiation from infrared wavelengths to the green ones, the powder bed absorption raised. As-built samples did not present oxides traces inside the microstructure and were constituted by α-Cu phase. The microstructure was constituted by both equiassic and elongated grains depending on the heat fluxes generated inside the material in the horizontal and vertical cross sections.

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Doutre, Pierre-Thomas. "Comment intégrer et faire émerger des structures architecturées dans l'optimisation de pièces pour la fabrication additive par faisceaux d’électrons". Thesis, Université Grenoble Alpes (ComUE), 2018. http://www.theses.fr/2018GREAI039.

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Grâce à la fabrication additive, il est aujourd'hui possible de fabriquer de nouvelles géométries. Les perspectives offertes par les moyens de fabrications conventionnelles et additives sont très différentes. Des propositions de design très contraintes peuvent devenir beaucoup plus libres avec la fabrication additive. Cette liberté qu'elle offre fait émerger une multitude de possibilités. Dans ce manuscrit, nous nous sommes focalisés sur un type particulier de structures (les octetruss) ainsi que sur les moyens de fabrication EBM (Electron Beam Melting) de la société ARCAM. Les travaux présentés dans cette thèse ont été réalisés au sein des laboratoires G-SCOP et SIMAP ainsi qu'en partenariat avec l'entreprise POLY-SHAPE. Ce manuscrit est articulé autour de trois principaux points.Il s'agit tout d'abord de faire émerger des structures treillis lors du processus de conception. Pour cela, deux approches existantes sont détaillées. La première met en œuvre l'optimisation topologique et la seconde s'appuie sur le concept de matériau équivalent. Ensuite deux méthodologies permettent de faire émerger des zones dans lesquelles l'intégration de structures treillis est adaptée. La première consiste à réaliser les différentes zones en s'appuyant sur un champ de contraintes issu d'un calcul Eléments Finis, la seconde se base sur un résultat d'optimisation topologique pour établir les différentes zones. Cette seconde méthodologie est appliquée à un cas d'étude industriel.Ensuite nous étudions comment remplir les différentes zones avec des structures treillis adaptées en nous focalisant tout d'abord sur leur génération. Un accent particulier est porté sur l'intersection des différents barreaux par la mise en place de sphères. Une méthodologie permettant de générer des arrondis est également proposée. Une étude est menée sur l'ensemble des paramètres et informations à considérer pour intégrer une structure treillis à une zone donnée. Cette étude conduit à une proposition de méthodologie qui est appliquée à un cas d'étude industriel.Enfin, les aspects liés à la fabrication sont pris en compte. Pour cela, nous considérons différentes limites du moyen de fabrication EBM pour des structures treillis comme les dimensions maximales réalisables ou les problématiques thermiques. Une étude consistant à prédire la dépoudrabilité des pièces est réalisée. Enfin, des essais mécaniques sont effectués. Nos résultats sont comparés à ceux obtenus dans d'autres travaux. L'impact des arrondis sur le comportement mécanique d'une pièce est discuté
Thanks to additive manufacturing, it is now possible to manufacture new geometric shapes. The prospects offered by the methods of conventional and additive manufacturing are very different. Highly constrained design proposals can become much freer with additive manufacturing. The freedom it offers brings forward a multitude of possibilities. In this manuscript, we focused on a particular type of structures (the octetruss) as well as the use of EBM (Electron Beam Melting) of ARCAM as a means of manufacturing. The work presented in this thesis was carried out in the laboratories G-SCOP and SIMAP as well as in partnership with the company POLY-SHAPE. This manuscript focuses on three main points.The first of which is the action of emergence of lattice structures during the design process. For this, two existing approaches are detailed. The first uses topological optimization and the second is based on the concept of equivalent material. Following these, there are two methodologies used to identify areas in which the integration of lattice structures is possible and appropriate. The first consists of creating the different zones by relying on a stress field resulting from a finite element calculation, the second establishes the different zones using a topological optimization result. This second methodology is applied to an industrial case study.Secondly, we study how to fill the different areas with appropriate lattice structures by focusing first on their generation. Particular emphasis is placed on the intersection of the various bars by the establishment of spheres. A methodology for generating rounded-shape is also proposed. A study is carried out on all the parameters and information in order to integrate a lattice structure to a given area. This study leads to a proposed methodology that is applied to an industrial case study.Finally, aspects related to manufacturing are taken into account. For this, we consider different limits of the EBM manufacturing and what they mean for lattice structures; such as maximum achievable dimensions or thermal problems. A study to predict powder removal in order to extract the fabricated structure is performed. Mechanical tests are carried out. Our results are compared to those obtained in other works. The impact of curve on the mechanical behavior of a product is discussed

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Graf, Marcel, Sebastian Härtel e André Hälsig. "Numerische Auslegung des Mehrlagenschweißens als additives Fertigungsverfahren". Universitätsbibliothek Chemnitz, 2017. http://nbn-resolving.de/urn:nbn:de:bsz:ch1-qucosa-225946.

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Die additiven Fertigungstechnologien erleben seit einigen Jahren einen enormen Zuspruch bei der Herstellung von Einzelteilserien mit komplexen, endkonturnahen Geometrien und der Verarbeitung von Sonder- oder hybriden Werkstoffen. Prinzipiell lassen sich die Verfahren gemäß VDI- Richtlinie 3404 in drahtbasierte und pulverbasierte unterteilen. Eine weitere Unterteilung erfolgt hinsichtlich der Ausschmelztechnologie. Allen Verfahren ist gleich, dass schichtweise der Grundwerkstoff an den Stellen aufgetragen wird, wo er gemäß Endkontur benötigt wird. Damit ist ein immer wiederkehrender Wärmeeintrag verbunden, der somit Einfluss auf die Mikrostruktur der Bauteile und gleichzeitig auch auf die mechanischen Endeigenschaften ausübt. Die so erzeugten Komponenten sollten wenig Verzug oder Eigenspannungen als auch keine Porosität aufweisen, um die Gebrauchseigenschaften nicht negativ zu beeinflussen. Das Ziel ist es mittlerweile, diese verschiedenen Technologien numerisch abzubilden, um die Bauteileigenschaften vorherzusagen und ggf. Optimierungspotenziale zu eruieren. Der untersuchte Prozess ist das drahtbasierte Mehrlagenschweißen mittels des Metallschutzgasschweißens, bei dem neben der Simulation auch die Validierung im Fokus hinsichtlich Geometrie und Gefügeausbildung in den Schweißlagen stand. Diesbezüglich wurden im vorliegenden Fall zum einen alle, für die numerische Simulation notwendigen Materialparameter (mechanische und thermophysikalische Kenngrößen) des Schweißzusatzwerkstoffes G4Si1 bestimmt und in ein kommerzielles FEM-Programm (MSC Marc Mentat) implementiert. Zum anderen erfolgt zukünftig die wissenschaftliche Analyse der Verbesserung der Bauteileigenschaft, in dem die Schweißnaht unter Ausnutzung der Schweißhitze warmumgeformt wird. Erste Ergebnisse numerischer Simulationsergebnisse zeigen positive Effekte. Diese zeigen mikrostrukturelle Veränderungen (Kornfeinung durch Rekristallisation) und führten letztendlich zur Steigerung der mechanischen Eigenschaften. Der Vorteil dieser Verfahrenskombination ist außerdem die Kompensation des Verzuges durch die gezielte Umformung und einem gleichzeitigen „Richten“.

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Chougrani, Laurent. "Modélisation avancée de formes complexes de pièces mécaniques pour lesprocédés de fabrication additive". Thesis, Paris, ENSAM, 2017. http://www.theses.fr/2017ENAM0054.

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Les procédés de fabrication additive ont connus un fort essor dans les dernières décennies et entament aujourd'hui leur phase d'industrialisation pérenne. L'industrie, dans un souci d'améliorer sans cesse le ratio masse/rigidité des systèmes qu'elle produit (notamment l'industrie aéronautique), a pris conscience du potentiel de ces technologies à produire des structures plus complexes que les procédés classiques. Elle cherche aujourd'hui à tirer profit de ce potentiel pour alléger encore plus les pièces produites en utilisant notamment des géométries de type réseaux ou alvéolaires (Lattice en anglais). Les travaux présentés dans ce manuscrit ont pour but de proposer une méthodologie, des modèles et des outils permettant la conception, le dimensionnement et l'optimisation de telles structures en vue de leur fabrication par procédés additifs. Le framework proposé peut être résumé par les huit étapes ci-dessous:- Importation de l'espace de conception, comprenant également les cas de chargement.- Optimisation topologique sur l'espace de conception.- Reconstruction de la géométrie, appelée primitive, qui servira de support à l'insertion du réseau.- Calcul par éléments finis qui peut être réalisé pour s'assurer de la bonne tenue mécanique.- Définition de la topologie du réseau, par l'intermédiaire d'un graphe 3D.- Déformation du réseau et optimisation mécanique du réseau.- Reconstruction des volumes.- Préparation des fichiers de données et impression 3D
Additive manufacturing processes have been quickly growing those past decades and are now getting to their sustainable industrial. Industry has been caring about the mass to rigidity ratio of the structures it produces (especially in aeronautics), and is now acknowledging the potential of additive processes to produce more complex shapes than classical processes. Industry is now trying to take advantage of this potential by designing highly complex structures like lattices or metal foams. The work that is presented in this document propose a methodology, models and numerical tools allowing the conception, dimensioning and optimization of such structures through additive manufacturing. The proposed framework can be describe through the height following steps:- Importing the design space and the technical requirement (load cases).- Topology optimization of the design space- Geometry reconstruction to create a primitive which will be the lattice insertion area.- Finite elements computation to ensure that the structure meets the requirements.- Lattice topology definition using 3D graphs.- Lattice deformation and optimization.- Creation of the volumes around the lattice.- Printing file creation and 3D printing

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Marion, Guillaume. "Modélisation de procédés de fabrication additive de pièces aéronautiques et spatiales en Ti-6AI-4V par dépôt et fusion sélective d'un lit de poudre par laser : Approche thermique, métallurgique et mécanique". Thesis, Paris Sciences et Lettres (ComUE), 2016. http://www.theses.fr/2016PSLEM055.

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La fabrication additive est une famille de procédés permettant de construire des pièces finies, saines, de géométries très complexes, tout en diminuant le temps de développement des pièces, les coûts et les délais vis-à-vis des techniques de fabrication conventionnelles. Le point commun à tous ces procédés est de construire une pièce directement à partir des données CAO définissant sa géométrie sans outillage autre que la machine de fabrication additive.Cette thèse de Doctorat s'inscrit dans le projet de recherche FALAFEL (Fabrication Additive par procédé LAser et Faisceaux d’ÉLectrons) rassemblant les filières aéronautique et procédés laser dans le but de mettre en œuvre, d’améliorer et de valider des procédés de fabrication additive de pièces métalliques, dans des conditions industrielles et sur des composants aéronautiques.L'objectif est de proposer un modèle numérique permettant d’obtenir, dans des temps raisonnables, des informations sur les caractéristiques thermique, métallurgique et mécanique de pièces industrielles en titane Ti-6Al-4V destinées à être fabriquées par deux procédés de fabrication additive : la projection de poudre (Direct Metal Deposition ou DMD) et la fusion laser sélective (Selective Laser Melting ou SLM)
Additive manufacturing processes allow to build finished industrial parts with very complex geometry, while reducing development time and costs compared to conventional manufacturing processes. The main principle of all these processes is to build components directly from a CAD file defining its geometry without requiring any mold nor specific tools.This study is part of the FALAFEL research project focused on additive manufacturing processes by laser and electron beams. It is composed of academic research laboratories and industrial partners from Aeronautics and Laser Processes industries. The main goal of this project is to implement, improve and validate additive manufacturing processes regarding the production of metallic components for Aeronautics. Studies are conducted under industrial conditions.The aim of our thesis is to provide a numerical model to obtain, within a reasonable time, information about the mechanical and metallurgical properties of industrial components made out of titanium Ti-6Al-4V. It is aimed at two additive manufacturing processes: the Direct Metal Deposition (DMD) and the Selective laser melting (SLM)

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PEDEMONTE, LAURA CHIARA. "Laser in Metal Additive Manufacturing". Doctoral thesis, Università degli studi di Genova, 2019. http://hdl.handle.net/11567/973605.

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The evolution of additive manufacturing (AM) techniques has had such an exponential increase especially in recent years that various and remarkable techniques have been developed for the production of metallic materials. These techniques allow to obtain products with remarkable mechanical characteristics. Therefore, the different AM techniques that employed metallic materials were analysed and their strengths and weaknesses were considered. In particular, investigations were carried out on artefacts made by Direct Metal Laser Sintering (DMLS) technique in two different metal alloys: Inconel-625 and titanium grade 2. In relation to Inconel-625, tomographic analyses were carried out for the detection of ad hoc defects, ultrasound analyses to evaluate anistropy, micrographs and tensile tests to evaluate their mechanical characteristics. The titanium grade 2 products were compared with samples made by the traditional fusion technique to assess their suitability in the dental field. The results show that artefacts made by DMLS technique have overall better features than fusion samples: the defects are less widespread and smaller, the hardness - characteristic of mechanical properties - higher.

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Cumbunga, Judice. "Modeling and optimization of the thermomechanical behavior of metal partsobtained by sintering : Numerical and experimental approach". Electronic Thesis or Diss., Bourgogne Franche-Comté, 2024. http://www.theses.fr/2024UBFCA006.

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Le procédé de frittage sans pression à l'état solide est un traitement thermique appliqué pour améliorer ou ajuster les propriétés du matériau en fonction de son domaine d’application, compte tenu de sa capacité à traiter des pièces à géométrie complexe, de sa grande précision dimensionnelle, de ses petites dimensions et de son adéquation aux matériaux doux et durs. Cependant, la modélisation de ce type de procédé s’avère une tâche difficile, car un modèle approprié doit prendre en compte différents aspects, à savoir le caractère multi-échelle et multiphysique du problème, la forte non-linéarité du matériau, la complexité des géométries et enfin la nature des conditions aux limites, etc. Sur le plan industriel, les paramètres de traitement thermiques appropriés sont principalement obtenus par essais. La simulation numérique permet de réduire les coûts de ces essais et de fournir des prévisions ou des recommandations plus utiles pour la production réelle, que les essais de frittage proprement dits. De nombreux travaux de recherche ont été consacrés aux développements de modèles mathématiques et numériques avec des approches adaptées à différents niveaux ou échelles, tels que la petite échelle (niveau atomique), la méso-échelle (niveau des particules, des grains et des pores), et l'échelle du continuum (niveau des composants). La capacité et la maitrise de pouvoir prédire l'évolution de la microstructure ont placé le modèle mésoscopique (au niveau des particules, des grains et des pores) devant les autres.Sur le plan recherche, la question posée serait donc "Étant donné une pièce brute obtenue par MExAM, comment simuler numériquement l'évolution de la microstructure (à partir d’un état microstructural initial) pour contrôler les changements dans les propriétés thermomécaniques pendant le processus de frittage à l'état solide ?"Un modèle de calcul robuste, basé sur une approche multiphysique et multiéchèle, a été développé, testé et validé. Il permet la prédiction des évolutions de la microstructure et des grandeurs thermiques et mécaniques du matériau. Le modèle repose sur la méthode des éléments finis et prend en compte de manière progressive les couplages multiphysiques (thermique, mécanique et microstructure) influant sur le comportement du matériau. Un traitement particulier a été étudié pour la prise en compte des phénomènes non linéaires. Les résultats des différentes simulations ont montré que le modèle développé est capable de prédire avec une précision correcte le comportement du processus de frittage. Le cas particulier du comportement du matériau pour le MExAM a été présentée, ainsi que la manière d'utiliser le modèle pour optimiser ses propriétés thermomécaniques. L'optimisation a été réalisée en couplant les résultats des différentes simulations avec la méthode Taguchi. Il faut souligner que les résultats obtenus à partir de l'analyse des propriétés des matériaux témoignent de la réussite de l'application du modèle, tant du point de vue de la prévision du comportement microstructural et thermomécanique du matériau, que du point de vue de l'optimisation de ses propriétés
The pressureless solid-state sintering process is a thermal treatment applied to improve or adjust material properties according to its field of application, given its ability to handle parts with complex geometries, high dimensional accuracy, small dimensions and suitability for soft and hard materials. However, modeling this type of process proves to be a difficult task, as an appropriate model needs to take into account various aspects, namely the multi-scale and multi-physics character of the problem, the high non-linearity of the material, the complexity of the geometries and, last but not least, the type of boundary conditions. From an industrial point of view, the appropriate heat treatment parameters are mainly obtained by trial and error. Numerical simulation makes it possible to reduce the cost of these tests and to provide more useful predictions or recommendations for actual production, than sintering tests themselves. Numerous research projects have been devoted to the development of mathematical and numerical models with approaches adapted to different levels or scales, such as the small scale (atomic level), the meso-scale (particle, grain and pore level), and the continuum scale (component level). The ability to predict the evolution of microstructure has put the mesoscopic model (at particle, grain and pore level) ahead of the others.In research terms, the question posed would therefore be "Given a untreated part obtained by MExAM, how can we numerically simulate the evolution of the microstructure (from an initial microstructural state) to control changes in thermomechanical properties during the solid-state sintering process ?"A robust computational model, based on a multiphysics and multi-scale approach, has been developed, tested and validated. It enables us to predict the evolution of the material's microstructure, thermal and mechanical properties. The model is based on the finite element method, and progressively takes into account the multiphysical couplings (thermal, mechanical and microstructure) that influence the material's behavior. Special considerations have been given to the integration of non-linear phenomena. The results of the various simulations have shown that the model developed is capable of predicting the behavior of the sintering process with correct accuracy. The special case of material behavior for MExAM was presented, as well as how to use the model to optimize its thermomechanical properties. Optimization was achieved by coupling the results of the various simulations with the Taguchi method. It should be noted that the results obtained from the analysis of material properties confirm the successful application of the model, both in predicting the microstructural and thermomechanical behavior of the material, and in optimizing its properties

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Byron, Andrew James. "Qualification and characterization of metal additive manufacturing". Thesis, Massachusetts Institute of Technology, 2016. http://hdl.handle.net/1721.1/104315.

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Thesis: M.B.A., Massachusetts Institute of Technology, Sloan School of Management, 2016. In conjunction with the Leaders for Global Operations Program at MIT.
Thesis: S.M. in Engineering Systems, Massachusetts Institute of Technology, Department of Aeronautics and Astronautics, 2016. In conjunction with the Leaders for Global Operations Program at MIT.
Cataloged from PDF version of thesis.
Includes bibliographical references (pages 119-123).
Additive manufacturing (AM) has emerged as an effective and efficient way to digitally manufacture complicated structures. Raytheon Missile Systems seeks to gain limited production capability with metals AM, which can only be achieved with qualified, predictable processes that reduce variation. The project documented in this thesis produced two results needed to qualify AM for use on flight-critical parts: i) creation of a standard qualification process building upon Raytheon's product development knowledge, and ii) selection and identification of key metals AM process factors and their corresponding experimental responses. The project has delivered a qualification test plan and process that will be used next year to drive adoption and integration of Raytheon's metals AM technology. The first phase of the designed experiment on AM process factors was completed by experimenting with coupon orientation, position on the build platform, coupon shape and hot isostatic pressing (HIP) post-treatment for an Al alloy (AlSi10Mg) produced via laser powder bed fusion using 400-watt laser equipment. Only coupon orientation had a statistically significant effect on dimensional accuracy, increasing the variance of y-axis (within the build plane) error by ~50%, although this is considered a small increase. HIP decreased yield and ultimate stresses by ~60% while increasing ultimate strain by ~250%. Vertical orientation of coupons decreased yield and ultimate stresses by ~25% and increased ultimate strain by ~30%. Small coupon area on the build platform, associated with thin rectangle coupons, decreased yield stress and ultimate strain by ~5%. The processes and case study from this thesis represent a general advance in the adoption of metals AM in aerospace manufacturing.
by Andrew James Byron.
M.B.A.
S.M. in Engineering Systems

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Chabot, Alexia. "Méthodologie de monitoring multiphysique des procédés DED : développement par une démarche expérimentale". Thesis, Ecole centrale de Nantes, 2020. http://www.theses.fr/2020ECDN0022.

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La Fabrication Additive métallique apporte de nouvelles possibilités de fabrication et de liberté de conception des pièces fonctionnelles métalliques par rapport aux procédés conventionnels. En particulier, les technologies Direct Energy Deposition (DED), notamment les procédés Laser Metal Deposition (LMD) et Wire-Arc Additive Manufacturing (WAAM) fusionnent directement la matière et la déposent couche par couche pour réaliser une pièce. Actuellement, ces procédés sont majoritairement mis en œuvre en boucle ouverte. Ainsi, l’obtention d’une pièce conforme aux exigences du cahier des charges résulte le plus souvent d’une méthode essai-erreur. Afin d’améliorer la maitrise des procédés DED et de s’affranchir de cette méthode essai-erreur, la simulation numérique et le monitoring sont les principales pistes investiguées dans la littérature. Cette thèse propose une méthodologie générique de monitoring multiphysique, basée sur quatre boucles de contrôle indépendantes et pouvant être mises en œuvre simultanément. Ces boucles de contrôle se focalisent sur la température, la géométrie et la santé matière de la pièce, ainsi que sur le Stick Out. Dans ces travaux, les boucles de contrôle ont été principalement implémentées sur le procédé WAAM. Un soin particulier a été porté sur leur développement pour rendre ces boucles de contrôle adaptables au procédé LMD. Parallèlement à ces travaux, certains outils numériques existants ont été évalués dans l’optique d’être intégrés dans l’environnement de fabrication aux côtés du monitoring. Cette thèse s’inscrit dans le cadre du laboratoire commun Joint Laboratory of Marine Technology regroupant Naval Group et Centrale Nantes
Additive Manufacturing (AM) is a promising technology compared to subtractive processes, in terms of cost or freedom of manufacturing functional parts. Among the AM techniques, Laser Metal Deposition (LMD) and Wire-Arc Additive Manufacturing (WAAM), included in the Direct Energy Deposition (DED) processes, manufacture parts by directly melting the material in a layer-by-layer maner. Those processes are currently mainly operated in open-loop. Thus, an acceptable part regarding the specified specifications is often the result of a trial-and-error method. In order to improve DED processes performances and to get rid of this trial-and-error method, monitoring and numerical simulation are the most widely investigated solutions. These PhD works propose a generic multiphysic monitoring methodology, based on four independant control loops which can be operated simultaneously. Those control loops are dedicated to the part temperature, geometry, and structural health, and the Stick Out. In these PhD works, control loops have been mainly implemented on the WAAM process, and a specific attention has been devoted to their developments to ensure their applicability to the LMD process. Concurrent to these monitoring develoments, an evaluation of some existing numerical tools has been conducted, in order to integrate simulation together with monitoring in a manufacturing environement. This PhD project is part of the Joint Laboratory of Marine Techology formed by Naval Group and Centrale Nantes

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15

McCarthy, David Lee. "Creating Complex Hollow Metal Geometries Using Additive Manufacturing and Metal Plating". Thesis, Virginia Tech, 2012. http://hdl.handle.net/10919/43530.

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Additive manufacturing introduces a new design paradigm that allows the fabrication of geometrically complex parts that cannot be produced by traditional manufacturing and assembly methods. Using a cellular heat exchanger as a motivational example, this thesis investigates the creation of a hybrid manufacturing approach that combines selective laser sintering with an electroforming process to produce complex, hollow, metal geometries. The developed process uses electroless nickel plating on laser sintered parts that then undergo a flash burnout procedure to remove the polymer, leaving a complex, hollow, metal part. The resulting geometries cannot be produced directly with other additive manufacturing systems. Copper electroplating and electroless nickel plating are investigated as metal coating methods. Several parametric parts are tested while developing a manufacturing process. Copper electroplating is determined to be too dependent on the geometry of the part, with large changes in plate thickness between the exterior and interior of the tested parts. Even in relatively basic cellular structures, electroplating does not plate the interior of the part. Two phases of electroless nickel plating combined with a flash burnout procedure produce the desired geometry. The tested part has a density of 3.16g/cm3 and withstands pressures up to 25MPa. The cellular part produced has a nickel plate thickness of 800Âµm and consists of 35% nickel and 65% air (empty space). Detailed procedures are included for the electroplating and electroless plating processes developed.
Master of Science

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Cunningham, Ross W. "Defect Formation Mechanisms in Powder-Bed Metal Additive Manufacturing". Research Showcase @ CMU, 2018. http://repository.cmu.edu/dissertations/1160.

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Metal Additive Manufacturing (AM) provides the means to fabricate complex metallic parts with reduced time to market and material waste and improved design freedom. Industries with strict materials qualifications such as aerospace, biomedical, and automotive are increasingly looking to AM to meet their production needs. However, significant materials-related challenges impede the widespread adoption of these technologies for critical components. In particular, fatigue resistance in as-built parts has proven to be inferior and unpredictable due to the large and variable presence of porosity. This presents a challenge for the qualification of any load bearing part without extensive post-processing, such as Hot Isostatic Pressing, and thorough inspection. Improved understanding of the underlying mechanisms behind defect formation will assist in designing process improvements to minimize or eliminate defects without relying entirely on postprocessing. In this work, the effects of powder, processing parameters, and post-processing on porosity formation in powder-bed metal AM processes are investigated using X-ray microtomography and a newly developed in-situ high speed radiography technique, Dynamic Xray Radiography. High resolution X-ray computed tomography is used to characterize defect morphology, size, and spatial distribution as a function of process and material inputs. Dynamic X-ray Radiography, which enables the in-situ observation of the laser-metal interactions at frame rates on the order of 100 kHz (and faster), is utilized to understand the dynamic behavior and transitions that occur in the vapor depression across process space. Experimental validation of previously held assumptions regarding defect formation as well as new insights into the influence of the vapor cavity on defect formation are presented.

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Balsamy, Kamaraj Abishek. "Study of Localized Electrochemical Deposition for Metal Additive Manufacturing". University of Cincinnati / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1539078938687749.

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Nyembwe, Kasongo Didier. "Tool manufacturing by metal casting in sand moulds produced by additive manufacturing processes". Thesis, Bloemfontein : Central University of Technology, Free State, 2012. http://hdl.handle.net/11462/162.

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Thesis (D. Tech. ( Mechanical Engineering )) - Central University of technology, Free State, 2012
In this study an alternative indirect Rapid Tooling process is proposed. It essentially consists of producing sand moulds by Additive Manufacturing (AM) processes followed by casting of tools in the moulds. Various features of this tool making method have been investigated. A process chain for the proposed tool manufacturing method was conceptually developed. This process chain referred to as Rapid Casting for Tooling (RCT) is made up of five steps including Computer Aided Design (CAD) modeling, casting simulation, AM of moulds, metal casting and finishing operations. A validation stage is also provided to determine the suitability of the tool geometry and material for RCT. The theoretical assessment of the RCT process chain indicated that it has potential benefits such as short manufacturing time, low manufacturing cost and good quality of tools in terms of surface finish and dimensional accuracy. Focusing on the step of AM of the sand moulds, the selection of available AM processes between the Laser Sintering (LS) using an EOSINT S 700 machine and Three Dimensional Printing using a Z-Corporation Spectrum 550 printer was addressed by means of the Analytic Hierarchy Process (AHP). The criteria considered at this stage were manufacturing time, manufacturing cost, surface finish and dimensional accuracy. LS was found to be the most suitable for RCT compared to Three Dimensional Printing. The overall preferences for these two alternatives were respectively calculated at 73% and 27%. LS was then used as the default AM process of sand moulds in the present research work. A practical implementation of RCT to the manufacturing of foundry tooling used a case study provided by a local foundry. It consisted of the production of a sand casting pattern in cast iron for a high pressure moulding machine. The investigation confirmed the feasibility of RCT for producing foundry tools. In addition it demonstrated the crucial role of casting simulation in the prevention of casting defects and the prediction of tool properties. The challenges of RCT were found to be exogenous mainly related to workmanship. An assessment of RCT manufacturing time and cost was conducted using the case study above mentioned as well as an additional one dealing with the manufacturing of an aluminium die for the production of lost wax patterns. Durations and prices of RCT steps were carefully recorded and aggregated. The results indicated that the AM of moulds was the rate determining and cost driving step of RCT if procurement of technology was considered to be a sunk cost. Overall RCT was found to be faster but more expensive than machining and investment casting. Modern surface analyses and scanning techniques were used to assess the quality of RCT tools in terms of surface finish and dimensional accuracy. The best surface finish obtained for the cast dies had Ra and Rz respectively equal to 3.23 μm and 11.38 μm. In terms of dimensional accuracy, 82% of cast die points coincided with die Computer Aided Design (CAD) data which is within the typical tolerances of sand cast products. The investigation also showed that mould coating contributed slightly to the improvement of the cast tool surface finish. Finally this study also found that the additive manufacturing of the sand mould was the chief factor responsible for the loss of dimensional accuracy. Because of the above, it was concluded that light machining will always be required to improve the surface finish and the dimensional accuracy of cast tools. Durability was the last characteristic of RCT tools to be assessed. This property was empirically inferred from the mechanical properties and metallographic analysis of castings. Merit of durability figures of 0.048 to 0.152 were obtained for the cast tools. It was found that tools obtained from Direct Croning (DC) moulds have merit of durability figures three times higher than the tools produced from Z-Cast moulds thus a better resistance to abrasion wear of the former tools compared to the latter.

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GALATI, MANUELA. "Design of product and process for Metal Additive Manufacturing - From design to manufacturing". Doctoral thesis, Politecnico di Torino, 2017. http://hdl.handle.net/11583/2688272.

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Additive Manufacturing (AM) is a recent new manufacturing approach that is based on the fabrication of each object using a layer-by-layer strategy. From a manufacturability perspective of components, this approach involves the possibility to manufacture parts of any geometric complexity without using additional tools and machines. Particular attention is dedicated to the powder bed fusion (PBF) AM processes in which a laser beam or an electron beam is used to sinter or melt metallic powders which are named Selective Laser Melting (SLM) and Electron Beam Melting (EBM). In fact, in these last years, growing interesting of the industry has been outlined for metal AM, because they offer exclusive benefits such as the direct production of complex functional and/or end-usable parts made with excellent materials. Today it is thus recognised the need for guidelines and tools for effective introduction of the AM processes in the metal industry. To address this issue the aim of the presented thesis was to propose concurrent engineering (CE) tools based on a comprehensive approach from design to manufacturing. The metal PBF-AM processes have been dealt by two subsequent steps. The first one addressed the development of a process selection (PS) tool that combines materials, processes and designs for the choice of the best alternative to produce a metal component. The second one concerned with the development of a model for the process simulation that can contribute to the understanding of the process. The proposed PS tool aimed to introduce the metal AM processes as alternative to producing components. In particular, the tool was implemented in order to consider the comparison between different metal AM manufacturing processes as well as AM, machining and casting. In this approach, each alternative is represented by a combination of the design, material and process features. A well-structured open architecture for PS has been suggested. The tool works by considering the requirements of the component regarding geometry constraints and specifications. A methodology based on mathematical modeling design decisions involving multiple attributes was suggested to assess the technical and economic aspects in order to analyse and rank the alternatives. For this purpose, an index, called DePri, was introduced to resume technical aspects and offers a quantitative comparison between the alternatives. On the other, the economic aspect for AM has been addressed by providing a detail model cost. The results of the process selection in which the technical aspect of each alternative has been considered and the alternatives can be compared with the corresponding manufacturing cost. An application of the proposed tool was demonstrated by an industrial case study in which the objective was to assess the best technology resource between 3-axis CNC machining, SLM and EBM for future investments of the company in the AM technologies. The second issue addresses the optimisation of the metal PBF-AM process by virtual simulation for a suitable selection of the process parameters. In this context, the resulting review showed the SLM as a consolidated process respect to process simulation while EBM has received less attention despite the numerous applications in the medical and aerospace fields. In order to improve the effectiveness and reliability of EBM FE simulation, a new type of modelling has been introduced for the energy source and the powder material properties which have been included in a thermal numerical model. The potential of the proposed modelling was demonstrated using comparison with existing experimental literature data for a single straight line, existing model in published literature and experimental measurements for multibeam and continuous line melting. The model was then used to investigate the effects of the process parameters on the microstructures of a TiAl alloy.

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Ranjan, Rajit. "Design for Manufacturing and Topology Optimization in Additive Manufacturing". University of Cincinnati / OhioLINK, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1439307951.

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Markusson, Lisa. "Powder Characterization for Additive Manufacturing Processes". Thesis, Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-62683.

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The aim of this master thesis project was to statistically correlate various powder characteristics to the quality of additively manufactured parts. An additional goal of this project was to find a potential second source supplier of powder for GKN Aerospace Sweden in Trollhättan. Five Inconel® alloy 718 powders from four individual powder suppliers have been analyzed in this project regarding powder characteristics such as: morphology, porosity, size distribution, flowability and bulk properties. One powder out of the five, Powder C, is currently used in production at GKN and functions as a reference. The five powders were additively manufactured by the process of laser metal deposition according to a pre-programmed model utilized at GKN Aerospace Sweden in Trollhättan. Five plates were produced per powder and each cut to obtain three area sections to analyze, giving a total of fifteen area sections per powder. The quality of deposited parts was assessed by means of their porosity content, powder efficiency, geometry and microstructure. The final step was to statistically evaluate the results through the analysis methods of Analysis of Variance (ANOVA) and simple linear regression with the software Minitab. The method of ANOVA found a statistical significant difference between the five powders regarding their experimental results. This made it possible to compare the five powders against each other. Statistical correlations by simple linear regression analysis were found between various powder characteristics and quality of deposited part. This led to the conclusion that GKN should consider additions to current powder material specification by powder characteristics such as: particle morphology, powder porosity and flowability measurements by a rheometer. One powder was found to have the potential of becoming a second source supplier to GKN, namely Powder A. Powder A had overall good powder properties such as smooth and spherical particles, high particle density at 99,94% and good flowability. The deposited parts with Powder A also showed the lowest amount of pores compared to Powder C, a total of 78 in all five plates, and sufficient powder efficiency at 81,6%.

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Foschini, Alessandro. "Application of Additive Manufacturing to long fibers Metal Matrix Composites". Master's thesis, Alma Mater Studiorum - Università di Bologna, 2017.

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The present thesis aims at verifying the possibility to combine the fabrication of long fibres Metal Matrix Composites with the innovative design possibilities provided by the Additive Manufacturing technology. This work documents how all the main physical and chemical interactions, defects and processing products are created starting from inputs until achieving the final mechanical and microstructure outputs. Firstly, the process limitations of SLM and of the fabrication of long fibres MMCs are evaluated through a deep study of the whole complex of variables characterizing the technologies. Secondly, thanks to the knowledge gained, a description of the possibility to combine these two technologies is made. Flowcharts are created and evaluated in order to obtain clear and simple mental schemes to understand how all variables impact on the manufacturing processes. The results achieved will help to comprehend how these processes may interact together and from this it will be possible to lay the foundations for future research.

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Hussein, Ahmed Yussuf. "The development of lightweight cellular structures for metal additive manufacturing". Thesis, University of Exeter, 2013. http://hdl.handle.net/10871/15023.

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Metal Additive Manufacturing (AM) technologies in particular powder bed fusion processes such as Selective Laser Melting (SLM) and Direct Metal Laser Sintering (DMLS) are capable of producing a fully-dense metal components directly from computer-aided design (CAD) model without the need of tooling. This unique capability offered by metal AM has allowed the manufacture of inter-connected lattice structures from metallic materials for different applications including, medical implants and aerospace lightweight components. Despite the many promising design freedoms, metal AM still faces some major technical and design barriers in building complex structures with overhang geometries. Any overhang geometry which exceeds the minimum allowable build angle must be supported. The function of support structure is to prevent the newly melted layer from curling due to thermal stresses by anchoring it in place. External support structures are usually removed from the part after the build; however, internal support structures are difficult or impossible to remove. These limitations are in contrast to what is perceived by designers as metal AM being able to generate all conceivable geometries. Because support structures consume expensive raw materials, use a considerable amount of laser consolidation energy, there is considerable interest in design optimisation of support structure to minimize the build time, energy, and material consumption. Similarly there is growing demand of developing more advanced and lightweight cellular structures which are self-supporting and manufacturable in wider range of cell sizes and volume fractions using metal AM. The main focuses of this research is to tackle the process limitation in metal AM and promote design freedom through advanced self-supporting and low-density Triply Periodic Minimal Surface (TPMS) cellular structures. Low density uniform, and graded, cellular structures have been developed for metal AM processes. This work presents comprehensive experimental test conducted in SLM and DMLS processes using different TPMS cell topologies and materials. This research has contributed to new knowledge in understanding the manufacturability and mechanical behaviour of TPMS cellular structures with varying cell sizes, orientations and volume fractions. The new support structure method will address the saving of material (via low volume cellular structures and easy removal of powder) and saving of energy (via reduced build-time).

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Valli, Giuseppe <1989&gt. "Metal additive manufacturing of soft magnetic material for electric machines". Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2022. http://amsdottorato.unibo.it/10131/1/Valli_Giuseppe_tesi.pdf.

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This research work concerns the application of additive manufacturing (AM) technologies in new electric mobility sectors. The unmatched freedom that AM offers can potentially change the way electric motors are designed and manufactured. The thesis investigates the possibility of creating optimized electric machines that exploit AM technologies, with potential in various industrial sectors, including automotive and aerospace. In particular, we will evaluate how the design of electric motors can be improved by producing the rotor core using Laser Powder Bed Fusion (LPBF) and how the resulting design choices affect component performance. First, the metallurgical and soft magnetic properties of the pure iron and silicon iron alloy parts (Fe-3% wt.Si) produced by LPBF will be defined and discussed, considering the process parameters and the type of heat treatment. This research shows that using LPBF, both pure iron and iron silicon, the parts have mechanical and magnetic properties different from the laminated ones. Hence, FEM-based modeling will be employed to design the rotor core of an SYN RM machine to minimize torque ripple while maintaining structural integrity. Finally, we suggest that further research should extend the field of applicability to other electrical devices.

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Miranda, Neiva Eric. "Large-scale tree-based unfitted finite elements for metal additive manufacturing". Doctoral thesis, Universitat Politècnica de Catalunya, 2020. http://hdl.handle.net/10803/669823.

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This thesis addresses large-scale numerical simulations of partial differential equations posed on evolving geometries. Our target application is the simulation of metal additive manufacturing (or 3D printing) with powder-bed fusion methods, such as Selective Laser Melting (SLM), Direct Metal Laser Sintering (DMLS) or Electron-Beam Melting (EBM). The simulation of metal additive manufacturing processes is a remarkable computational challenge, because processes are characterised by multiple scales in space and time and multiple complex physics that occur in intricate three-dimensional growing-in-time geometries. Only the synergy of advanced numerical algorithms and high-performance scientific computing tools can fully resolve, in the short run, the simulation needs in the area. The main goal of this Thesis is to design a a novel highly-scalable numerical framework with multi-resolution capability in arbitrarily complex evolving geometries. To this end, the framework is built by combining three computational tools: (1) parallel mesh generation and adaptation with forest-of-trees meshes, (2) robust unfitted finite element methods and (3) parallel finite element modelling of the geometry evolution in time. Our numerical research is driven by several limitations and open questions in the state-of-the-art of the three aforementioned areas, which are vital to achieve our main objective. All our developments are deployed with high-end distributed-memory implementations in the large-scale open-source software project FEMPAR. In considering our target application, (4) temporal and spatial model reduction strategies for thermal finite element models are investigated. They are coupled to our new large-scale computational framework to simplify optimisation of the manufacturing process. The contributions of this Thesis span the four ingredients above. Current understanding of (1) is substantially improved with rigorous proofs of the computational benefits of the 2:1 k-balance (ease of parallel implementation and high-scalability) and the minimum requirements a parallel tree-based mesh must fulfil to yield correct parallel finite element solvers atop them. Concerning (2), a robust, optimal and scalable formulation of the aggregated unfitted finite element method is proposed on parallel tree-based meshes for elliptic problems with unfitted external contour or unfitted interfaces. To the author’s best knowledge, this marks the first time techniques (1) and (2) are brought together. After enhancing (1)+(2) with a novel parallel approach for (3), the resulting framework is able to mitigate a major performance bottleneck in large-scale simulations of metal additive manufacturing processes by powder-bed fusion: scalable adaptive (re)meshing in arbitrarily complex geometries that grow in time. Along the development of this Thesis, our application problem (4) is investigated in two joint collaborations with the Monash Centre for Additive Manufacturing and Monash University in Melbourne, Australia. The first contribution is an experimentally-supported thorough numerical assessment of time-lumping methods, the second one is a novel experimentally-validated formulation of a new physics-based thermal contact model, accounting for thermal inertia and suitable for model localisation, the so-called virtual domain approximation. By efficiently exploiting high-performance computing resources, our new computational framework enables large-scale finite element analysis of metal additive manufacturing processes, with increased fidelity of predictions and dramatical reductions of computing times. It can also be combined with the proposed model reductions for fast thermal optimisation of the manufacturing process. These tools open the path to accelerate the understanding of the process-to-performance link and digital product design and certification in metal additive manufacturing, two milestones that are vital to exploit the technology for mass-production.
Aquesta tesi tracta la simulació a gran escala d'equacions en derivades parcials sobre geometries variables. L'aplicació principal és la simulació de procesos de fabricació additiva (o impressió 3D) amb metalls i per mètodes de fusió de llit de pols, com ara Selective Laser Melting (SLM), Direct Metal Laser Sintering (DMLS) o Electron-Beam Melting (EBM). La simulació d'aquests processos és un repte computacional excepcional, perquè els processos estan caracteritzats per múltiples escales espaitemporals i múltiples físiques que tenen lloc sobre geometries tridimensionals complicades que creixen en el temps. La sinèrgia entre algorismes numèrics avançats i eines de computació científica d'alt rendiment és la única via per resoldre completament i a curt termini les necessitats en simulació d'aquesta àrea. El principal objectiu d'aquesta tesi és dissenyar un nou marc numèric escalable de simulació amb capacitat de multiresolució en geometries complexes i variables. El nou marc es construeix unint tres eines computacionals: (1) mallat paral·lel i adaptatiu amb malles de boscs d'arbre, (2) mètodes d'elements finits immersos robustos i (3) modelització en paral·lel amb elements finits de geometries que creixen en el temps. Algunes limitacions i problemes oberts en l'estat de l'art, que són claus per aconseguir el nostre objectiu, guien la nostra recerca. Tots els desenvolupaments s'implementen en arquitectures de memòria distribuïda amb el programari d'accés obert FEMPAR. Quant al problema d'aplicació, (4) s'investiguen models reduïts en espai i temps per models tèrmics del procés. Aquests models reduïts s'acoplen al nostre marc computacional per simplificar l'optimització del procés. Les contribucions d'aquesta tesi abasten els quatre punts de dalt. L'estat de l'art de (1) es millora substancialment amb proves riguroses dels beneficis computacionals del 2:1 balancejat (fàcil paral·lelització i alta escalabilitat), així com dels requisits mínims que aquest tipus de mallat han de complir per garantir que els espais d'elements finits que s'hi defineixin estiguin ben posats. Quant a (2), s'ha formulat un mètode robust, òptim i escalable per agregació per problemes el·líptics amb contorn o interface immerses. Després d'augmentar (1)+(2) amb un nova estratègia paral·lela per (3), el marc de simulació resultant mitiga de manera efectiva el principal coll d'ampolla en la simulació de processos de fabricació additiva en llits de pols de metall: adaptivitat i remallat escalable en geometries complexes que creixen en el temps. Durant el desenvolupament de la tesi, es col·labora amb el Monash Centre for Additive Manufacturing i la Universitat de Monash de Melbourne, Austràlia, per investigar el problema d'aplicació. En primer lloc, es fa una anàlisi experimental i numèrica exhaustiva dels mètodes d'aggregació temporal. En segon lloc, es proposa i valida experimental una nova formulació de contacte tèrmic que té en compte la inèrcia tèrmica i és adequat per a localitzar el model, l'anomenada aproximació per dominis virtuals. Mitjançant l'ús eficient de recursos computacionals d'alt rendiment, el nostre nou marc computacional fa possible l'anàlisi d'elements finits a gran escala dels processos de fabricació additiva amb metalls, amb augment de la fidelitat de les prediccions i reduccions significatives de temps de computació. Així mateix, es pot combinar amb els models reduïts que es proposen per l'optimització tèrmica del procés de fabricació. Aquestes eines contribueixen a accelerar la comprensió del lligam procés-rendiment i la digitalització del disseny i certificació de productes en fabricació additiva per metalls, dues fites crucials per explotar la tecnologia en producció en massa.

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26

Butt, Javaid. "A novel additive manufacturing process for the production of metal parts". Thesis, Anglia Ruskin University, 2016. http://arro.anglia.ac.uk/701001/.

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The majority of additive manufacturing methods use different materials for the production of parts. The current methods employing powder metals have their limitations and are very expensive. This research presents a novel additive manufacturing process for the generation of modest and high quality metal parts. The procedure, referred to as Composite Metal Foil Manufacturing, is a blend of Laminated Object Manufacturing and soldering/brazing strategies. A calculated model of a machine in view of the new process has been outlined and its parts accepted for usefulness either by experimentation or recreations. The viability of the new process is accepted with lap-shear testing, peel testing, microstructural examination and tensile testing. Distinctive metals, such as copper and aluminium, with shifting thicknesses were used to demonstrate the adaptability of the procedure. Composites of aluminium and copper were additionally delivered and tried for their mechanical properties to show the flexibility of the process. The outcomes of the research attained have been promising and show that the new process is not just fit for delivering astounding metal parts efficiently but can create more grounded parts contrasted with customary subtractive techniques. The comparative tensile testing demonstrated that the parts created by the new process had force values that were 11%, 8% and 11% higher than the parent copper, aluminium and composite examples individually. This shows that the procedure has the capability to be a solid competitor in the field of metal prototyping. It has been demonstrated that the proposed procedure can have a gigantic effect as it has lessened the confinements, for example, cost, pace, material determinations and beyond. The additive manufacturing identified with the generation of metal parts using the new process can work with an extensive variety of metals under typical conditions regardless of their joining capacities. The feedback that parts delivered by added substance fabrication techniques are not sufficiently strong for genuine applications can without much of a stretch is hushed with the obtained trial results. Applications can extend from little bespoke parts to large scale functional products that can be utilized with minimal post handling.

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27

Syed, Waheed Ul Haq. "Combined wire and powder deposition for laser direct metal additive manufacturing". Thesis, University of Manchester, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.556499.

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28

Gullapalli, Vikranth. "Study of Metal Whiskers Growth and Mitigation Technique Using Additive Manufacturing". Thesis, University of North Texas, 2015. https://digital.library.unt.edu/ark:/67531/metadc804972/.

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For years, the alloy of choice for electroplating electronic components has been tin-lead (Sn-Pb) alloy. However, the legislation established in Europe on July 1, 2006, required significant lead (Pb) content reductions from electronic hardware due to its toxic nature. A popular alternative for coating electronic components is pure tin (Sn). However, pure tin has the tendency to spontaneously grow electrically conductive Sn whisker during storage. Sn whisker is usually a pure single crystal tin with filament or hair-like structures grown directly from the electroplated surfaces. Sn whisker is highly conductive, and can cause short circuits in electronic components, which is a very significant reliability problem. The damages caused by Sn whisker growth are reported in very critical applications such as aircraft, spacecraft, satellites, and military weapons systems. They are also naturally very strong and are believed to grow from compressive stresses developed in the Sn coating during deposition or over time. The new directive, even though environmentally friendly, has placed all lead-free electronic devices at risk because of whisker growth in pure tin. Additionally, interest has occurred about studying the nature of other metal whiskers such as zinc (Zn) whiskers and comparing their behavior to that of Sn whiskers. Zn whiskers can be found in flooring of data centers which can get inside electronic systems during equipment reorganization and movement and can also cause systems failure.Even though the topic of metal whiskers as reliability failure has been around for several decades to date, there is no successful method that can eliminate their growth. This thesis will give further insights towards the nature and behavior of Sn and Zn whiskers growth, and recommend a novel manufacturing technique that has potential to mitigate metal whiskers growth and extend life of many electronic devices.

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29

Famodimu, Omotoyosi Helen. "Additive manufacturing of aluminium-metal matrix composite developed through mechanical alloying". Thesis, University of Wolverhampton, 2016. http://hdl.handle.net/2436/620337.

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Laser melting of aluminium alloy - AlSi10Mg has increasingly been used to create specialised products in aerospace and automotive applications. However, research on utilising laser melting of Aluminium matrix composites in replacing specialised parts have been slow on the uptake. This has been attributed to the complexity of the laser melting process, metal/ceramic feedstock for the process and the reaction of the feedstock material to the laser. Thus an understanding of the process, material microstructure and mechanical properties is important for its adoption as a manufacturing route of Aluminium Metal Matrix Composites. The effect of the processing parameters (time and speed) on embedding the Silicon Carbide onto the surface of the AlSi10Mg alloy was initially investigated in Phase 1 and 2 of the research. The particle shape and maximum particle size for each milling time and speed was analysed in determining a suitable starting powder for the Laser Melting phase. An ideal shape and size for the composite powder was obtained at 500 rev/min when milled for 20 mins. The effects of several parameters of the Laser Melting process on the mechanical blended composite were investigated. Single track formations of the matrix alloy, 5% Aluminium Metal Matrix Composites and 10% Aluminium Metal Matrix Composites were studied for their reaction to the laser melting in Phase 3. Subsequently in Phase 4, density blocks were studied at different scan speeds and step-over for surface roughness, relative density and porosity. These were utilised in determining a process window to fabricate near fully dense components. Phase 5 of the research focused on microstructural and mechanical properties of the laser melted matrix alloy using the normal parameters for the matrix alloy and the modified LM parameters for the composite powders. Test coupons were built in one orientation and some coupons were heat-treated to initiate precipitation-hardening intermetallics in the matrix and composite. This study investigates the suitability of the mechanical alloying as a novel method of producing feedstock material for the LM process. This research further explores the interaction of the composite powders with the laser until suitable process parameters were obtained. Furthermore, the fractography, mechanical and microstructural evolution of the Al/SiC composite, with different percentage volume reinforcement manufactured by the LM and subsequently heat treated, was explored for the first time.

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30

Butt, Javaid. "A novel additive manufacturing process for the production of metal parts". Thesis, Anglia Ruskin University, 2016. https://arro.anglia.ac.uk/id/eprint/701001/6/Butt_2016_thesis.pdf.

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The majority of additive manufacturing methods use different materials for the production of parts. The current methods employing powder metals have their limitations and are very expensive. This research presents a novel additive manufacturing process for the generation of modest and high quality metal parts. The procedure, referred to as Composite Metal Foil Manufacturing, is a blend of Laminated Object Manufacturing and soldering/brazing strategies. A calculated model of a machine in view of the new process has been outlined and its parts accepted for usefulness either by experimentation or recreations. The viability of the new process is accepted with lap-shear testing, peel testing, microstructural examination and tensile testing. Distinctive metals, such as copper and aluminium, with shifting thicknesses were used to demonstrate the adaptability of the procedure. Composites of aluminium and copper were additionally delivered and tried for their mechanical properties to show the flexibility of the process. The outcomes of the research attained have been promising and show that the new process is not just fit for delivering astounding metal parts efficiently but can create more grounded parts contrasted with customary subtractive techniques. The comparative tensile testing demonstrated that the parts created by the new process had force values that were 11%, 8% and 11% higher than the parent copper, aluminium and composite examples individually. This shows that the procedure has the capability to be a solid competitor in the field of metal prototyping. It has been demonstrated that the proposed procedure can have a gigantic effect as it has lessened the confinements, for example, cost, pace, material determinations and beyond. The additive manufacturing identified with the generation of metal parts using the new process can work with an extensive variety of metals under typical conditions regardless of their joining capacities. The feedback that parts delivered by added substance fabrication techniques are not sufficiently strong for genuine applications can without much of a stretch is hushed with the obtained trial results. Applications can extend from little bespoke parts to large scale functional products that can be utilized with minimal post handling.

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31

Kodira, Ganapathy D. "Investigation of an Investment Casting Method Combined with Additive Manufacturing Methods for Manufacturing Lattice Structures". Thesis, University of North Texas, 2013. https://digital.library.unt.edu/ark:/67531/metadc283786/.

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Cellular metals exhibit combinations of mechanical, thermal and acoustic properties that provide opportunities for various implementations and applications; light weight aerospace and automobile structures, impact and noise absorption, heat dissipation, and heat exchange. Engineered cell topologies enable one to control mechanical, thermal, and acoustic properties of the gross cell structures. A possible way to manufacture complex 3D metallic cellular solids for mass production with a relatively low cost, the investment casting (IC) method may be used by combining the rapid prototyping (RP) of wax or injection molding. In spite of its potential to produce mass products of various 3D cellular metals, the method is known to have significant casting porosity as a consequence of the complex cellular topology which makes continuous fluid's access to the solidification interface difficult. The effects of temperature on the viscosity of the fluids were studied. A comparative cost analysis between AM-IC and additive manufacturing methods is carried out. In order to manufacture 3D cellular metals with various topologies for multi-functional applications, the casting porosity should be resolved. In this study, the relations between casting porosity and processing conditions of molten metals while interconnecting with complex cellular geometries are investigated. Temperature, and pressure conditions on the rapid prototyping – investment casting (RP-IC) method are reported, thermal stresses induced are also studied. The manufactured samples are compared with those made by additive manufacturing methods.

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32

Dordlofva, Christo. "Qualification of Metal Additive Manufacturing in Space Industry : Challenges for Product Development". Licentiate thesis, Luleå tekniska universitet, Innovation och Design, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-66699.

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Additive manufacturing (AM), or 3D printing, is a collection of production processes that has received a good deal of attention in recent years from different industries. Features such as mass production of customised products, design freedom, part consolidation and cost efficient low volume production drive the development of, and the interest in, these technologies. One industry that could potentially benefit from AM with metal materials is the space industry, an industry that has become a more competitive environment with established actors being challenged by new commercial initiatives. To be competitive in these new market conditions, the need for innovation and cost awareness has increased. Efficiency in product development and manufacturing is required, and AM is promising from these perspectives. However, the maturity of the AM processes is still at a level that requires cautious implementation in direct applications. Variation in manufacturing outcome and sensitivity to part geometry impact material properties and part behaviour. Since the space industry is characterised by the use of products in harsh environments with no room for failure, strict requirements govern product development, manufacturing and use of space applications. Parts have to be shown to meet specific quality control requirements, which is done through a qualification process. The purpose of this thesis is to investigate challenges with development and qualification of AM parts for space applications, and their impact on the product development process. Specifically, the challenges with powder bed fusion (PBF) processes have been in focus in this thesis. Four studies have been carried out within this research project. The first was a literature review coupled with visits to AM actors in Sweden that set the direction for the research. The second study consisted of a series of interviews at one company in the space industry to understand the expectations for AM and its implications on product development. This was coupled with a third study consisting of a workshop series with three companies in the space industry. The fourth study was an in-depth look at one company to map the qualification of manufacturing processes in the space industry, and the challenges that are seen for AM. The results from these studies show that engineers in the space industry work under conditions that are not always under their control, and which impact how they are able to be innovative and to introduce new manufacturing technologies, such as AM. The importance of product quality also tends to lead engineers into relying on previous designs meaning incremental, rather than radical, development of products is therefore typical. Furthermore, the qualification of manufacturing processes relies on previous experience which means that introducing new processes, such as AM, is difficult due to the lack of knowledge of their behaviour. Two major challenges with the qualification of critical AM parts for space applications have been identified: (i) the requirement to show that critical parts are damage tolerant which is challenging due to the lack of understanding of AM inherent defects, and (ii) the difficulty of testing parts in representative environments. This implies that the whole product development process is impacted in the development and qualification of AM parts; early, as well as later stages. To be able to utilise the design freedom that comes with AM, the capabilities of the chosen AM process has to be considered. Therefore, Design for Manufacturing (DfM) has evolved into Design for Additive Manufacturing (DfAM). While DfAM is important for the part design, this thesis also discusses its importance in the qualification of AM parts. In addition, the role of systems engineering in the development and qualification of AM parts for space applications is highlighted.

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33

Wei, William Lien Chin. "New Studies on Thermal Transport in Metal Additive Manufacturing Processes and Products". Research Showcase @ CMU, 2017. http://repository.cmu.edu/dissertations/1057.

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Additive manufacturing (AM) is a manufacturing technique that adds material, such as polymers, ceramics, and metals, in patterned layers to build three-dimensional parts for applications related to medicine, aviation, and energy. AM processes for metals like selective laser melting (SLM) hold the unique advantage of fabricating metal parts with complex architectures that cannot be produced by conventional manufacturing techniques. Thermal transport can be a focal point of unique AM products and is likewise important to metal AM processes. This dissertation investigates AM metal meshes with spatially varied thermal conductivities that can be used to maximize the charge and discharge rates for thermal energy storage and thermal management by phase change materials (PCMs). Further, manufacturing these meshes demands excellent thermal control in the metal powder bed for SLM processes. Since the thermal conductivities of metal powders specific to AM were previously unknown, we made pioneering measurements of such powders as a function of gas infiltration. In the past, thermal transport was improved in phase change materials for energy storage by adding spatially homogeneous metal foams or particles into PCMs to create composites with uniformly-enhanced (UE) thermal conductivity. Spatial variation can now be realized due to the emergence of metal AM processes whereby graded AM meshes are inserted into PCMs to create PCM composites with spatially-enhanced (SE) thermal conductivity. As yet, there have been no studies on what kind of spatial variation in thermal conductivity can further improve charge and discharge rates of the PCM. Making such mesh structures, which exhibit unsupported overhangs that limit heat dissipation pathways during SLM processes, demands understanding of heat diffusion within the surrounding powder bed. This inevitably relies on the precise knowledge of the thermal conductivity of AM metal powders. Currently, no measurements of thermal conductivity of AM powders have been made for the SLM process. In chapter 2 and 3, we pioneer and optimize the spatial variation of metal meshes to maximize charge and discharge rates in PCMs. Chapter 2 defines and analytically determines an enhancement ratio of charge rates using spatially-linear thermal conductivities in Cartesian and cylindrical coordinates with a focus on thermal energy storage. Chapter 3 further generalizes thermal conductivity as a polynomial function in space and numerically optimizes the enhancement ratio in spherical coordinates with a focus on thermal management of electronics. Both of our studies find that higher thermal conductivities of SE composites near to the heat source outperform those of UE composites. For selected spherical systems, the enhancement ratio reaches more than 800% relative to existing uniform foams. In chapter 4, the thermal conductivities of five metal powders for the SLM process were measured using the transient hot wire method. These measurements were conducted with three infiltrating gases (He, N2, and Ar) within a temperature range of 295-470 K and a gas pressure range of 1.4-101 kPa. Our measurements indicate that the pressure and the composition of the gas have a significant influence on the effective thermal conductivity of the powder. We find that infiltration with He provides more than 300% enhancement in powder thermal conductivity, relative to conventional infiltrating gases N2 and Ar. We anticipate that this use of He will result in better thermal control of the powder bed and thus will improve surface quality in overhanging structures.

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34

Khademzadeh, Saeed. "Assessment and Development of Laser-Based Additive Manufacturing Technologies For Metal Microfabrication". Doctoral thesis, Università degli studi di Padova, 2019. http://hdl.handle.net/11577/3424951.

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Nowadays many devices are produced in very small sizes or containing small features for particular application such as biomedical and microfluidic devices. Based on this demand, manufacturing processes should be developed for implementation of micro features in different ranges of sizes. A broad range of microfabrication technologies have been developed which have different applications and capabilities such as laser ablation, plating, photolithography, lithography and electroplating. However, such techniques are restricted when utilized to new microproducts which need the employment of a diversity of materials and have complicated three-dimensional geometries. Additive manufacturing (AM) needs each layer to be fabricated according to an exact geometry defined by a 3D model. This concept seems suitable for production of complicated parts with micro features. Development of robust metal additive manufacturing for microfabrication opens a new window toward miniaturization of metallic parts such as design and production of porous implants containing micro features and micro pores (50-500 µm). This work covers the development of micro additive manufacturing through two laser based AM processes with two different concepts: Micro direct metal deposition (µDMD) and selective laser melting (SLM). Nowadays, NiTi shape memory alloys are among the most interesting materials in the field of bioengineering and medical applications. Assessment of both techniques for production of NiTi porous scaffolds for biomedical application was carried out in this thesis. Long-term fixation of biomedical implants is achievable by using porous materials. These kinds of materials can develop a stable bone-implant interface. A critical aspect in production of porous implants is the design of macro and micro pores. At the first step of this thesis, the process parameters of both technologies were optimized to obtain full density samples. Secondly, porous scaffold structures with geometry controlled porosity were designed and manufactured using both technologies. Investigations using X-ray diffraction and scanning electron microscopy equipped with energy dispersive spectroscopy showed that B2-NiTi phase with small quantity of unwanted intermetallics can be obtained by micro direct metal deposition of mechanically alloyed Ni50.8Ti49.2 powder. Micro direct metal deposition was optimized through a set of process parameters and designed experiments to improve the geometrical accuracy and repeatability of micro fabrication. Micro X-ray computed tomography were used to analyze the surface topography, micro porosity, and deviations of products with respect to nominal geometrical models. Below 10% deviation to nominal geometrical models was achieved in hollow NiTi samples through a set of micro direct metal deposition process parameters and designed experiments. A comprehensive study was conducted on Ni50.8 Ti49.2 (at%) alloy to discover the influence of SLM process parameters on different aspects of physical and mechanical properties of NiTi parts. The provided knowledge allowed choosing different optimized parameters for production of complicated geometry with micro features maintaining the phase composition through the sample. For the first time and in this thesis, without going through any solid solution and heat treatments, single phase austenite was obtained in SLM NiTi parts with the selection of three different regimes of process parameters. This knowledge led to manufacture of NiTi bony structure applying different process parameters for the border and internal parts. The experimental results showed that SLM process with specific process parameters is a feasible micro additive manufacturing method to implement the complicated internal architecture of bone. It is an important issue in production of customized prostheses.

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PAKKANEN, JUKKA ANTERO. "Designing for Additive Manufacturing - Product and Process Driven Design for Metals and Polymers". Doctoral thesis, Politecnico di Torino, 2018. http://hdl.handle.net/11583/2714732.

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Additive Manufacturing (AM) has broken through to common awareness and to wider industrial utilization in the past decade. The advance of this young technology is still rapid. In spoken language additive manufacturing is referred as 3D printing for plastic material and additive manufacturing is left as an umbrella term for other materials i.e. metallic materials and ceramics. As the utilization of AM becomes more widespread, the design for additive manufacturing becomes more crucial as well as its standardization. Additive manufacturing provides new set of rules with different design freedom in comparison with subtractive manufacturing methods. This is thought to empower product driven designs. However, in the AM methods there are process driven variables that limit the designs functions to what could be manufactured. There are often extra steps after production to finalize the design. Topology optimization utilizes product driven design where material is only where it is needed to be. The design is computed without taking into account any manufacturing constrains and only the design in the final application stage is achieved. Topology optimization algorithm is explored in detail for two algorithms. Then these algorithms are compared in case study I to gain better understanding of the algorithms functions. Case study I consists of 2D and 3D algorithms where a 3D level set method algorithm was written for this purpose. The concept of designing for additive manufacturing is examined for polymeric materials in case study II with a help of topology optimization design software tailored for additive manufacturing market. The parts are manufactured with different AM methods, examined and results are explained. The results show an interesting effect of anisotropy and the manufacture methods effect in the part mechanical properties. On the other hand, process driven design and its concepts important as the manufacturing method dictates, what can and should be done economically. Metal AM process constraints are explored in case study III through accuracy studies in metal additive manufacturing at laser powder bed fusion (LPBF) technology. Accuracy and surface studies are concluded to gain a better understanding of the process and manufacturability of metal parts. The gain knowledge is explaned and examples are shown how these are utilized to make metal parts with tailored properties and with minimal post processing needs.

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36

Odinot, Julie. "Développement de la fabrication additive directe par DED-CLAD : de la poudre à la mise en forme de pièces céramiques denses". Thesis, Université Paris-Saclay (ComUE), 2019. http://www.theses.fr/2019SACLN059.

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Les techniques d’élaboration de matériaux par fabrication additive (FA) sont en plein essor [1]. Elles permettent de fabriquer des pièces par ajout de matière, en opposition avec les techniques traditionnelles par soustraction de matière (usinage). Il existe à l’heure actuelle de nombreux procédés de FA, adaptés à différentes applications : fusion ou frittage par faisceau d’électrons ou par laser, dépôt de matière direct ou en lit de poudre… Ces procédés ont été bien développés pour des matériaux polymères puis métalliques. Des techniques de FA de matériaux céramiques via des polymères chargés ont également vu le jour, mais celles-ci nécessitent des traitements postérieurs (cycles de déliantage, frittage) [2]. Les matériaux céramiques denses sont encore peu développés en fabrication additive en raison de la fissuration de ces matériaux lors de leur élaboration.La technologie CLAD (Construction Laser Additive Directe), développée par IREPA-LASER, permet la fabrication de pièces par dépôt de matière fondue. Le matériau sous forme de poudre est acheminé via une buse laser et projeté dans le faisceau. Il est ainsi porté à la température de fusion. La fusion successive de plusieurs couches permet l’obtention de la pièce. Cette technique, en plus de n’utiliser que la matière nécessaire (contrairement aux techniques de fabrication par lit de poudre), permet la fabrication de pièces de grandes dimensions, voire en multi-matériaux. Cette technologie est, pour l’heure, dédiée aux matériaux métalliques.L’objet de ce sujet de thèse, en partenariat entre l’ONERA et IREPA-LASER dans le cadre du projet inter-Carnot CLADIATOR, est d’étudier la FA de matériaux céramiques denses par le procédé CLAD®. Cette étude porte ainsi sur le procédé dans son ensemble, des matières premières aux pièces finales, en passant par l’adaptation du moyen de fabrication aux contraintes spécifiques liées aux matériaux céramiques.Les matières premières exigent d’être adaptées au procédé ; les deux principales difficultés étant la coulabilité de la poudre, nécessaire pour son acheminement dans la buse, et l’absorption de la source laser par le matériau pour sa montée en température. En parallèle de la caractérisation des matières premières (granulométrie, MEB, dilatométrie, DRX…), des essais d’atomisation par séchage seront effectués pour optimiser la coulabilité des poudres [3]. Ce procédé d’atomisation permet d’obtenir des poudres sous forme d’agglomérats sphériques de plus petites particules ; leur forme est régulière, mais elles restent poreuses. L’ajout de dopants sera étudié pour améliorer l’absorption du signal, en adéquation avec une éventuelle adaptation du laser. Les matériaux considérés sont l’alumine, la zircone ainsi que des compositions eutectiques d’alumine-zircone.La principale difficulté de ce sujet réside dans la sensibilité à la fissuration des matériaux céramiques, en raison du fort gradient thermique induit par le chauffage local du laser et le refroidissement de la pièce. Des solutions de chauffage de la pièce et/ou du matériau avant et après le dépôt seront étudiées pour limiter les contraintes thermomécaniques subies par le matériau [3,4].La machine devra également être modifiée pour supporter les températures élevées nécessaires à l’élaboration de céramiques (températures de fusion et dispositif de pré/post chauffage). L’étude et l’optimisation de ces solutions seront effectuées à l’aide de modélisations multi physiques sur le logiciel COMSOL en collaboration avec IREPA-LASER.Enfin, l’influence du procédé d’élaboration sur l’état des pièces réalisées sera étudiée grâce à des caractérisations microscopiques, mécaniques, thermiques…
This work, in partnership between the ONERA Materials and Composite Structure Department (DMSC) and IREPA Laser within the CLADIATOR project, is based on the study of direct additive manufacturing of dense ceramic materials by direct melt deposition (also known as laser cladding) process. This process enables high dimensions or even multi-materials part manufacturing.It will deal with the adaptation of raw materials (ceramic powders) to the existing machine, especially in the case of powder flowability and optical absorption. Indeed, the powder flowability enables its transportation up to the laser nozzle, while the optical absorption of the laser signal is necessary to allow its melting.In parallel, the existing machine also needs to be adapted to ceramic materials : the main difficulty of this work will be the occurence of cracks during the manufacturing. This phenomena is due to the local heating by the laser and the materials brittleness. That’s why some secondary heating solutions, before or after the melt, will have to be defined to decrease the thermal gradient in the material while processing. Those solutions will be discussed between Onera and Irepa Laser, based on FEM simulations established with COMSOL Multiphysics software.Finally, the elaboration process influence on the manufactured ceramics parts will be investigated with microscopy, mechanical and thermal characterization

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37

PISCOPO, GABRIELE. "Analysis, numerical modelling and experimental investigation of Laser Powder Directed Energy Deposition (LP-DED) process". Doctoral thesis, Politecnico di Torino, 2020. http://hdl.handle.net/11583/2809317.

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Hehr, Adam J. "Process Control and Development for Ultrasonic Additive Manufacturing with Embedded Fibers". The Ohio State University, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=osu1461153463.

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Kumara, Chamara. "Microstructure Modelling of Additive Manufacturing of Alloy 718". Licentiate thesis, Högskolan Väst, Avdelningen för avverkande och additativa tillverkningsprocesser (AAT), 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:hv:diva-13197.

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In recent years, additive manufacturing (AM) of Alloy 718 has received increasing interest in the field of manufacturing engineering owing to its attractive features compared to those of conventional manufacturing methods. The ability to produce complicated geometries, low cost of retooling, and control of the microstructure are some of the advantages of the AM process over traditional manufacturing methods. Nevertheless, during the building process, the build material undergoes complex thermal conditions owing to the inherent nature of the process. This results in phase transformation from liquid to solid and solid state. Thus, it creates microstructural gradients in the built objects, and as a result,heterogeneous material properties. The manufacturing process, including the following heat treatment that is used to minimise the heterogeneity, will cause the additively manufactured material to behave differently when compared to components produced by conventional manufacturing methods. Therefore, understanding the microstructure formation during the building and subsequent post-heat treatment is important, which is the objective of this work. Alloy 718 is a nickel-iron based super alloy that is widely used in the aerospace industry and in the gas turbine power plants for making components subjected tohigh temperatures. Good weldability, good mechanical properties at high temperatures, and high corrosion resistance make this alloy particularly suitablefor these applications. Nevertheless, the manufacturing of Alloy 718 components through traditional manufacturing methods is time-consuming and expensive. For example, machining of Alloy 718 to obtain the desired shape is difficult and resource-consuming, owing to significant material waste. Therefore, the application of novel non-conventional processing methods, such as AM, seems to be a promising technique for manufacturing near-net-shape complex components.In this work, microstructure modelling was carried out by using multiphase-field modelling to model the microstructure evolution in electron beam melting (EBM) and laser metal powder directed energy deposition (LMPDED) of Alloy 718 and x subsequent heat treatments. The thermal conditions that are generated during the building process were used as input to the models to predict the as-built microstructure. This as-built microstructure was then used as an input for the heat treatment simulations to predict the microstructural evolution during heat treatments. The results showed smaller dendrite arm spacing (one order of magnitude smaller than the casting material) in these additive manufactured microstructures, which creates a shorter diffusion length for the elements compared to the cast material. In EBM Alloy 718, this caused the material to have a faster homogenisation during in-situ heat treatment that resulting from the elevated powder bed temperature (> 1000 °C). In addition, the compositional segregation that occurs during solidification was shown to alter the local thermodynamic and kinetic properties of the alloy. This was observed in the predicted TTT and CCT diagrams using the JMat Pro software based on the predicted local segregated compositions from the multiphase-field models. In the LMPDED Alloy 718 samples, this resulted in the formation of δ phase in the interdendritic region during the solution heat treatment. Moreover, this resulted in different-size precipitation of γ'/γ'' in the inter-dendritic region and in the dendrite core. Themicro structure modelling predictions agreed well with the experimental observations. The proposed methodology used in this thesis work can be an appropriate tool to understand how the thermal conditions in AM affect themicro structure formation during the building process and how these as-built microstructures behave under different heat treatments.

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Argenio, Paolo. "Additive manufacturing of metal alloys for aerospace application: design, production, repair and optimization". Doctoral thesis, Universita degli studi di Salerno, 2018. http://hdl.handle.net/10556/3032.

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2016 - 2017
In the industrial field the employment of innovative fabrication technologies is emerging to the purpose of cost reduction and flexibility. In particular, great interest is addressed to additive manufacturing (AM) techniques, which allow to obtain complex parts based on CAD models. AM enables the fabrication of parts with complex geometry that are impractical to be manufactured using conventional subtractive manufacturing methods. Basically, all of the AM techniques employ the same basic principle: the final component is fabricated by means of layer by layer addition of the material. Today, in addition to plastic material, several metallic materials including steel, aluminium, nickel-based superalloys, cobalt-base alloys and titanium alloys may be processed to full dense parts with properties complying with the requirements of industrial applications. There has been particular interest in aerospace and biomedical industries owing to the possibility for high performance parts with reduced overall cost for manufacturing. For the aerospace industry this could lead to a reduction of required raw materials used to fabricate an in-service component, which is known as the “buy-to-fly” ratio. AM could also lead to new innovations for lightweight structures for several applications. Repairing and overhaul of in-service parts is possible as well. Furthermore, AM provides the potential to enable novel product design which would be impossible to be managed using conventional subtractive processes... [edited by author]
XVI n.s.

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Sequeira, Almeida P. M. "Process control and development in wire and arc additive manufacturing". Thesis, Cranfield University, 2012. http://dspace.lib.cranfield.ac.uk/handle/1826/7845.

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This thesis describes advancements in the modelling, optimisation, process control and mechanical performance of novel high deposition rate gas metal arc welding processes for large scale additive manufacturing applications. One of the main objectives of this study was to develop fundamental understanding of the mechanisms involved during processing with particular focus on single layer welds made of carbon steel using both pulsed-current gas metal arc welding and cold metal transfer processes. The effects of interactions between critical welding process variables and weld bead and plate fusion characteristics are studied for single and multi-layers. It was shown that several bead and plate fusion characteristics are strongly affected by the contact tip to work distance, TRIM, wire feed speed, wire feed speed to travel speed ratio, and wire diameter in pulsed-current gas metal arc welding. The arc-length control, dynamic correction and the contact tip to work distance are shown to strongly influence the weld bead geometry in the cold metal transfer process. This fundamental knowledge was essential to ensure the successful development of predictive interaction models capable of determining the weld bead geometry from the welding process parameters. The models were developed using the least-squares analysis and multiple linear regression method. The gas tungsten constricted arc welding process was utilised for the first time for out-of-chamber fabrication of a large scale and high-quality Ti-6Al-4V component. The main focus was, however, in the use of the cold metal transfer process for improving out-of-chamber deposition of Ti-6Al-4V at much higher deposition rates. The effect of the cold metal transfer process on the grain refinement features in the fusion zone of single layer welds under different torch gas shielding conditions was investigated. It was shown that significant grain refinement occurs with increasing helium content. The morphological features and static mechanical performance of the resulting multi-layered Ti-6Al-4V walls were also examined and compared with those in gas tungsten constricted arc welding. The results show that a considerable improvement in static tensile properties is obtained in both testing directions with cold metal transfer over gas tungsten constricted arc welding. It was suggested that this improvement in the mechanical behaviour could be due to the formation of more fine-grained structures,which are therefore more isotropic. The average ultimate tensile strength and yield strength of the as-deposited Ti-6Al-4V material processed via cold metal transfer meet the minima specification values recommended for most Ti-6Al-4V products. Neutron diffraction technique was used to establish the effect of repeated thermo-mechanical cycling on the generation, evolution and distribution of residual stresses during wire and arc additive manufacturing. The results show a significant redistribution of longitudinal residual stresses along both the substrate and multi-bead with repeated deposition. However, a nearly complete relaxation occurs along the built, once the base plate constraint is removed.

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Roca, Jaime Bonnín. "Leaders and Followers: Challenges and Opportunities in the Adoption of Metal Additive Manufacturing Technologies". Research Showcase @ CMU, 2017. http://repository.cmu.edu/dissertations/1092.

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Policymakers in the United States and elsewhere have recognized that a broad and competitive manufacturing sector is crucial to a robust economy and that to remain competitive, a nation must invent and master new ways of making things. Moving technologies from laboratory to commercial success poses considerable challenges however. If the technology is radically new, this transition can be so risky and investment-heavy that only very large private firms can attempt it. One such new technology is metal additive manufacturing (MAM). MAM provides a vivid illustration of the tensions policymakers must resolve in simultaneously supporting the commercialization of early-stage innovations of strategic national interest, while fulfilling the government’s duty to ensure human health and safety. After an initial chapter with a general overview of additive manufacturing technologies, this dissertation explores these tensions from the perspective of two very different industrial contexts: the U.S. as a technology leader and trailblazer in the development of the technology, and Portugal as a technology follower with severely constrained resources. In the first case study, I use the extreme case of MAM (an emerging technology with many sources of process uncertainty) in commercial aviation (an industry where lapses in safety can have catastrophic consequences) to unpack how the characteristics of a technology may influence the options for regulatory intervention. Although my work focuses on the U.S. and the Federal Aviation Administration’s regulation, I expect this work to have an international scope, given that in most countries regulation is heavily influenced by, if not an exact copy of, the U.S. regulation. Based on my findings, I propose an adaptive regulatory framework in which standards are periodically revised and in which different groups of companies are regulated differently as a function of their technological capabilities. I conclude by proposing a generalizable framework for regulating emerging process-based technologies in safety-critical industries in which the optimal regulatory configuration depends on the industry structure (number of firms), the performance and safety requirements, and the sources of technological uncertainty. In the second case study, I analyze the adoption of polymer (PAM) and metal (MAM) additive manufacturing technologies in the Portuguese molds industry, both of which offer important benefits to their products. Leveraging archival data (related to the history of Portuguese institutions, and the development of additive manufacturing both globally and in Portugal), insights from 45 interviews across academia, industry, and government; and 75 hours of participant observations, we develop insights about why institutional instability affected the adoption of Polymer Additive Manufacturing (PAM) and Metal Additive Manufacturing (MAM) differently. In both cases, Portugal invested in the technology relatively early, and in the case of PAM the research community has been able to move towards high-tech applications. In contrast, the adoption of MAM has been modest despite its potential to greatly improve the performance and competitiveness of metal molds. From the comparison between PAM and MAM, we generate theory about which technological and contextual factors affect their ‘technological forgiveness’, defined as the resiliency of a new technology’s adoption to institutional instability. We conclude by proposing a generalizable framework for ‘forgiveness’ in different industrial contexts. The final chapter of this dissertation contains practical recommendations for regulators and managers interested in adopting the technology. Policymakers in the aviation industry may want to encourage the creation of programs to gather more flight experience with MAM parts. Small aircraft and other applications with higher risk tolerance than commercial aviation might represent more important channels to gather information, as the history of composite materials suggests. More importantly, regulators may need to introduce clauses in their rules to regulate MAM to avoid situations of ‘regulatory lock-in’ which could harm the long-term potential of the technology. Despite the potential of additive manufacturing, we believe that near-term expectations for it are overblown. In general, additive manufacturing holds great promise, but in many areas the cart has gotten ahead of the horse. Much of the technology is still under development. The history of comparable technologies such as composite materials and high-performance castings shows that the problems may take decades to resolve. For now, additive manufacturing is cost-competitive only in niche applications — for instance, those involving plastics. Businesses that want to plunge into additive manufacturing should be cognizant of the challenges. Determining whether it makes sense to invest in additive manufacturing will require experimentation and learning.

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Gibbs, Jonathan Sutton. "Testbeds for quality and porosity control in metal additive manufacturing by selective laser melting". Thesis, Massachusetts Institute of Technology, 2018. http://hdl.handle.net/1721.1/120394.

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Thesis: Ph. D., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2018.
Cataloged from PDF version of thesis.
Includes bibliographical references (pages 277-283).
Selective laser melting (SLM) is a metal additive manufacturing process that can achieve high local density and near-net shape geometric accuracy. The dynamics of the meltpool and stability of the melt track upon cooling are critical to the microstructure, porosity, and final properties of the solidified material. Recent studies are replete with optimization of SLM scan parameters, yet there is need to develop a more fundamental understanding of how meltpool dynamics influence the SLM process, which may lead to new means of process control. First, a custom-built SLM testbed is presented integrating precision recoating, high resolution thermal metrology, and the capability to fabricate novel hybrid composites through selective doping of the powder bed by inkjet deposition. An initial demonstration of this testbed relates basic scan strategies to thermal history and resultant porosity in as-built alloy 316L austenitic stainless steel. Second, the thesis will investigate the influence of elevated ambient gas pressure on the meltpool and solidified track to elucidate how pressure may be used as a control variable to influence surface quality, porosity and material loss due to evaporation with the ultimate objective of improving processing throughput for 316L. Third, a preliminary study is performed on the generation of fine porosity by SLM, using powder feedstock mixed with a gassing agent, in combination with control of build environment pressure.
by Jonathan S. Gibbs.
Ph. D.

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44

Narra, Sneha Prabha. "Melt Pool Geometry and Microstructure Control Across Alloys in Metal Based Additive Manufacturing Processes". Research Showcase @ CMU, 2017. http://repository.cmu.edu/dissertations/914.

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There is growing interest in using additive manufacturing for various alloy systems and industrial applications. However, existing process development and part qualification techniques, both involve extensive experimentation-based procedures which are expensive and time-consuming. Recent developments in understanding the process control show promise toward the efforts to address these challenges. The current research uses the process mapping approach to achieve control of melt pool geometry and microstructure in different alloy systems, in addition to location specific control of microstructure in an additively manufactured part. Specifically, results demonstrate three levels of microstructure control, starting with the prior beta grain size control in Ti-6Al-4V, followed by cell (solidification structure) spacing control in AlSi10Mg, and ending with texture control in Inconel 718. Additionally, a prediction framework has been presented, that can be used to enable a preliminary understanding of melt pool geometry for different materials and process conditions with minimal experimentation. Overall, the work presented in this thesis has the potential to reduce the process development and part qualification time, enabling the wider adoption and use of additive manufacturing in industry.

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Everton, Sarah. "Ensuring the quality of components produced by metal additive manufacturing using laser generated ultrasound". Thesis, University of Nottingham, 2018. http://eprints.nottingham.ac.uk/51651/.

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Laser powder bed fusion offers many advantages over conventional manufacturing methods, such as the integration of multiple parts which can result in significant weight-savings. The increased design freedom that layer-wise manufacture allows has also been seen to enhance component performance at little or no added cost. However, for such benefits to be realised, the material quality must first be assured. Laser ultrasonic testing is a non-contact inspection technique which has been proposed as suitable for in-situ monitoring of metal additive manufacturing processes. The thesis presented here explores the current capability of this technique to detect manufactured, seeded and process generated sub-surface “defects” in Ti6Al4V samples, ex-situ. The results are compared with X-ray computed tomography reconstructions, focus variation microscopy and destructive testing. Whilst laser ultrasound has been used to successfully identify a range of material discontinuities, further work is required before this technique could be implemented in-situ.

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Dagres, Ioannis. "Simulation-guided lattice geometry optimization of a lightweight metal marine propeller for additive manufacturing". Thesis, Massachusetts Institute of Technology, 2019. https://hdl.handle.net/1721.1/122309.

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Thesis: Nav. E., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2019
Thesis: S.M., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2019
Cataloged from PDF version of thesis.
Includes bibliographical references (pages 149-153).
Additive manufacturing (AM) is one of the most promising emerging technologies for advanced mechanical systems. When compared to conventional manufacturing processes, AM offers major advantages in production of complex components, enhanced performance, material savings, and supply chain management. These advantages are driving a shift towards AM in marine industry, which is highlighted by recent relative publications of the American Bureau of Shipping (ABS) and others. This thesis focuses on the design of an exemplary marine propeller that leverages the advantages of AM through simulation-guided design of an internal lattice structure. Specifically, a B-series Wageningen three-blade propeller model, provided by Naval Warfare Surface Center (NSWC) Carderock, was used as a baseline. Its open water loading conditions were calculated numerically using OpenFOAM®, a computational fluid dynamics (CFD) software. The CFD results were verified using the provided test data, the thrust and torque coefficients differed by a maximum of 2.7%. The derived loads were introduced to the Finite Element Analysis (FEA) based optimization utility in Autodesk® Netfabb Ultimate, in order to identify the optimum lattice geometry for this application. The design limitations were dictated by the material (316SL stainless steel), the metal additive manufacturing process, and the propeller outer geometry.A variety of lattice infill designs were generated to create a design trade space and conclude to the most appropriate design for this application. The design with the best performance was a hexagonal grid lattice with 1 mm wall thickness, which was prescribed as a manufacturing constraint (i.e., the thinnest wall). The material volume was reduced by more than 50%, while exhibiting a satisfactory safety factor based on the material properties and the simulated loads. Sections of the propeller were prototyped by Desktop Metal Studio System[superscript TM].
by Ioannis Dagres.
Nav. E.
S.M.
Nav.E. Massachusetts Institute of Technology, Department of Mechanical Engineering
S.M. Massachusetts Institute of Technology, Department of Mechanical Engineering

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47

Andurand, Lewis. "Développement d'une méthode de génération de trajectoire versatile pour la réalisation de pièces par procédés DED multi-axes à partir de surfaces facettisées". Electronic Thesis or Diss., Toulon, 2023. http://www.theses.fr/2023TOUL0001.

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La fabrication additive est une catégorie de procédés qui permet l’obtention de pièces mécaniques par apport de matière. Les procédés de type Directed Energy Deposition (DED), combinables avec des robots multi-axes, sont prometteurs pour l’obtention de pièces à la structure complexe. Cependant, les méthodes de génération de trajectoire et les structures des machines utilisées restent un enjeu dont les innovations décupleraient les possibilités industrielles.Cette thèse présente une méthode numérique systématique de génération de trajectoire adaptée aux procédés DED à partir d’une surface facettisée de forme arbitraire. Validée à travers des simulations sur des surfaces minimales tri-périodiques, la méthode permet la création d’un premier trajet de dépôt respectant la contrainte de distance entre la pièce et l’outil. Combinable à de la rétroaction par priorisation de régions, il pourra être modifié ultérieurement selon les contre-indications physiques issues du robot utilisé, du matériau de fabrication et de l’outil
Additive manufacturing is a category of processes that allows the production of mechanical parts by the adding of material. Directed Energy Deposition (DED) processes can be combined with multi-axis robots and are a promising option to obtain parts with complex structures. However, the path generation methods and the machine structures used remain an issue. With innovations in these areas, the industrial possibilities would increase tenfold.This thesis presents a numerical and systematic path generation method based on meshed surfaces and adapted to DED processes. The method was validated through simulations on minimal triply periodic surfaces and allows the creation of a first deposition path that meets the distance constraint between the part and the tool. This first path can be combined with region prioritization feedback to obtain a final path adapted to the physical warnings provided by the robot, the manufacturing material and the tool

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Snelling, Jr Dean Andrew. "A Process for Manufacturing Metal-Ceramic Cellular Materials with Designed Mesostructure". Diss., Virginia Tech, 2003. http://hdl.handle.net/10919/51606.

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The goal of this work is to develop and characterize a manufacturing process that is able to create metal matrix composites with complex cellular geometries. The novel manufacturing method uses two distinct additive manufacturing processes: i) fabrication of patternless molds for cellular metal castings and ii) printing an advanced cellular ceramic for embedding in a metal matrix. However, while the use of AM greatly improves the freedom in the design of MMCs, it is important to identify the constraints imposed by the process and its process relationships. First, the author investigates potential differences in material properties (microstructure, porosity, mechanical strength) of A356 — T6 castings resulting from two different commercially available Binder Jetting media and traditional 'no-bake' silica sand. It was determined that they yielded statistically equivalent results in four of the seven tests performed: dendrite arm spacing, porosity, surface roughness, and tensile strength. They differed in sand tensile strength, hardness, and density. Additionally, two critical sources of process constraints on part geometry are examined: (i) depowdering unbound material from intricate casting channels and (ii) metal flow and solidification distances through complex mold geometries. A Taguchi Design of Experiments is used to determine the relationships of important independent variables of each constraint. For depowdering, a minimum cleaning diameter of 3 mm was determined along with an equation relating cleaning distance as a function of channel diameter. Furthermore, for metal flow, choke diameter was found to be significantly significant variable. Finally, the author presents methods to process complex ceramic structure from precursor powders via Binder Jetting AM technology to incorporate into a bonded sand mold and the subsequently casted metal matrix. Through sintering experiments, a sintering temperature of 1375 °C was established for the ceramic insert (78% cordierite). Upon printing and sintering the ceramic, three point bend tests showed the MMCs had less strength than the matrix material likely due to the relatively high porosity developed in the body. Additionally, it was found that the ceramic metal interface had minimal mechanical interlocking and chemical bonding limiting the strength of the final MMCs.
Ph. D.

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Snelling, Dean Andrew Jr. "A Process for Manufacturing Metal-Ceramic Cellular Materials with Designed Mesostructure". Diss., Virginia Tech, 2015. http://hdl.handle.net/10919/51606.

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The goal of this work is to develop and characterize a manufacturing process that is able to create metal matrix composites with complex cellular geometries. The novel manufacturing method uses two distinct additive manufacturing processes: i) fabrication of patternless molds for cellular metal castings and ii) printing an advanced cellular ceramic for embedding in a metal matrix. However, while the use of AM greatly improves the freedom in the design of MMCs, it is important to identify the constraints imposed by the process and its process relationships. First, the author investigates potential differences in material properties (microstructure, porosity, mechanical strength) of A356 — T6 castings resulting from two different commercially available Binder Jetting media and traditional 'no-bake' silica sand. It was determined that they yielded statistically equivalent results in four of the seven tests performed: dendrite arm spacing, porosity, surface roughness, and tensile strength. They differed in sand tensile strength, hardness, and density. Additionally, two critical sources of process constraints on part geometry are examined: (i) depowdering unbound material from intricate casting channels and (ii) metal flow and solidification distances through complex mold geometries. A Taguchi Design of Experiments is used to determine the relationships of important independent variables of each constraint. For depowdering, a minimum cleaning diameter of 3 mm was determined along with an equation relating cleaning distance as a function of channel diameter. Furthermore, for metal flow, choke diameter was found to be significantly significant variable. Finally, the author presents methods to process complex ceramic structure from precursor powders via Binder Jetting AM technology to incorporate into a bonded sand mold and the subsequently casted metal matrix. Through sintering experiments, a sintering temperature of 1375 °C was established for the ceramic insert (78% cordierite). Upon printing and sintering the ceramic, three point bend tests showed the MMCs had less strength than the matrix material likely due to the relatively high porosity developed in the body. Additionally, it was found that the ceramic metal interface had minimal mechanical interlocking and chemical bonding limiting the strength of the final MMCs.
Ph. D.

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Linn, John Ross. "Characterizing Interfacial Bonds in Hybrid Metal AM Structures". BYU ScholarsArchive, 2018. https://scholarsarchive.byu.edu/etd/7030.

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The capabilities of various metal Additive Manufacturing (AM) processes, such as Powder Bed Fusion – Laser (PBF-L) and Direct Energy Deposition (DED) are increasing such that it is becoming ever more common to use them in industrial applications. The ability to print atop a substrate broadens that scope of applications. There is ongoing research regarding the mechanical properties of additively processed materials, but little regarding the interaction between additive material and its substrate. An understanding of the mechanical and performance properties of the AM/substrate interface is imperative. This paper describes a study of the strength properties of AM/substrate interfaces, with respect to torsion and tension, and compares them to their fully wrought and fully additive counterparts. PBF-L and DED are used to produce tensile and torsion test specimens of two different materials, SS316L and M300 steels. This provides sufficient variety in testing for a confident analysis to be made.

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