Tesi sul tema "Metal extrusion additive manufacturing"
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1
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.
Abstract (sommario):
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.
2
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.
Abstract (sommario):
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 propriétésThe 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
3
Go, Jamison. "High-throughput extrusion-based additive manufacturing". Thesis, Massachusetts Institute of Technology, 2015. http://hdl.handle.net/1721.1/101812.
Abstract (sommario):
Thesis: S.M., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2015.Cataloged from PDF version of thesis.
Includes bibliographical references (pages 171-179).
Additive manufacturing (AM), the process of building objects layer by layer from a three dimensional digital model, is gaining significance due to its ability to create unique geometries and/or novel material compositions while spanning a wide range of length scales. However, the viability of using AM for the production of end-use parts hinges on improvements to production speed without making sacrifices to quality. This thesis seeks to understand the rate-limits to extrusion-based AM, commonly referred to as fused deposition modeling (FDM), and to demonstrate this understanding via the design and fabrication of a high-throughput extrusion AM platform. Three subsystems - the pinch wheel extruder, the conduction liquefier, and the open loop series gantry - were identified as rate limiting to conventional FDM systems via module level experimentation and analysis. These limitations motivated the development of three alternate mechanisms -a screw-feed extruder, a laser-heated extruder, and H-frame gantry - which are designed to overcome the limitations of conventional techniques. These mechanisms are combined into a high-throughput desktop-scale prototype, called FastFDM. Using the FastFDM system, test parts are fabricated at twice the material deposition rate of state-of-the-art machines while maintaining comparable accuracy and resolution. The FastFDM approach has promising future applications to the extrusion AM of nanocomposite polymer resins, high-throughput AM of high performance thermoplastics, and adaptation to large-scale extrusion AM systems.
by Jamison Go.
S.M.
4
Braconnier, Daniel J. "Materials Informatics Approach to Material Extrusion Additive Manufacturing". Digital WPI, 2018. https://digitalcommons.wpi.edu/etd-theses/204.
Abstract (sommario):
Process-structure-property relationships in material extrusion additive manufacturing (MEAM) are complex, non-linear, and poorly understood. Without proper characterization of the effects of each processing parameter, products produced through fused filament fabrication (FFF) and other MEAM processes may not successfully reach the material properties required of the usage environment. The two aims of this thesis were to first use an informatics approach to design a workflow that would ensure the collection of high pedigree data from each stage of the printing process; second, to apply the workflow, in conjunction with a design of experiments (DOE), to investigate FFF processing parameters. Environmental, material, and print conditions that may impact performance were monitored to ensure that relevant data was collected in a consistent manner. Acrylonitrile butadiene styrene (ABS) filament was used to print ASTM D638 Type V tensile bars. MakerBot Replicator 2X, Ultimaker 3, and Zortrax M200 were used to fabricate the tensile bars. Data was analyzed using multivariate statistical techniques, including principal component analysis (PCA). The magnitude of effect of layer thickness, extrusion temperature, print speed, and print bed temperature on the tensile properties of the final print were determined. Other characterization techniques used in this thesis included: differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), and scanning electron microscopy (SEM). The results demonstrated that printer selection is incredibly important and changes the effects of print parameters; moreover, further investigation is needed to determine the sources of these differences.
5
PEDEMONTE, LAURA CHIARA. "Laser in Metal Additive Manufacturing". Doctoral thesis, Università degli studi di Genova, 2019. http://hdl.handle.net/11567/973605.
Abstract (sommario):
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.
6
Malinowski, Maxwell. "High-throughput extrusion additive manufacturing using electrically resistive preheating". Thesis, Massachusetts Institute of Technology, 2016. http://hdl.handle.net/1721.1/105693.
Abstract (sommario):
Thesis: S.B., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2016.Cataloged from PDF version of thesis.
Includes bibliographical references (page 33).
Extrusion-based additive manufacturing, commonly known as fused deposition modeling (FDM) or fused filament fabrication (FFF) is incredibly useful in industry for a variety of reasons, including rapid prototyping and the ability to create complex geometries easily. However, its further adoption is limited by relatively slow part manufacturing rates when compared to conventional manufacturing methods. Previous work has identified three modules within the FDM process which are rate limiting: speed of gantry positioning, polymer heating, and extrusion pressure. Advancements in any one module will allow for higher volumetric output, which will in turn allow for higher rates of production using FDM. This work focuses on polymer heating, and demonstrates a new concept for rapid heating of filament by introducing conductive nanoparticles into the polymer resin and resistively heating sections in flow. This technique can improve the volumetric output of FDM printers by at least 20%. First, the resistive properties of the composite filament are characterized. Second, the concept is experimentally validated by demonstrating a decrease in extrusion force required to maintain a given feed rate when using resistive heating.
by Maxwell Malinowski.
S.B.
7
Byron, Andrew James. "Qualification and characterization of metal additive manufacturing". Thesis, Massachusetts Institute of Technology, 2016. http://hdl.handle.net/1721.1/104315.
Abstract (sommario):
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
8
MURUGAN, VARUN. "Optimized Material Deposition for Extrusion-Based Additive Manufacturing of Structural Components". Doctoral thesis, Università degli studi di Pavia, 2022. http://hdl.handle.net/11571/1464786.
9
McCarthy, David Lee. "Creating Complex Hollow Metal Geometries Using Additive Manufacturing and Metal Plating". Thesis, Virginia Tech, 2012. http://hdl.handle.net/10919/43530.
Abstract (sommario):
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 800µm 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
10
Cunningham, Ross W. "Defect Formation Mechanisms in Powder-Bed Metal Additive Manufacturing". Research Showcase @ CMU, 2018. http://repository.cmu.edu/dissertations/1160.
Abstract (sommario):
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.
11
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.
12
Pham, Khang Duy. "Quasi-Static Tensile and Fatigue Behavior of Extrusion Additive Manufactured ULTEM 9085". Thesis, Virginia Tech, 2018. http://hdl.handle.net/10919/82047.
Abstract (sommario):
Extrusion additive manufacturing technologies may be utilized to fabricate complex geometry devices. However, the success of these additive manufactured devices depends upon their ability to withstand the static and dynamic mechanical loads experienced in service. In this study, quasi-static tensile and cyclic fatigue tests were performed on ULTEM 9085 samples fabricated by fused deposition modeling (FDM). First, tensile tests were conducted following ASTM D638 on three different build orientations with default build parameters to determine the mechanical strength of FDM ULTEM 9085 with those supplied by the vendor. Next, different build parameters (e.g. contour thickness, number of contours, contour depth, raster thickness, and raster angle) were varied to study the effects of those parameters on mechanical strength.
Fatigue properties were investigated utilizing the procedure outlined in ASTM D7791. S-N curves were generated using data collected at stress levels of 80%, 60%, 30% and 20% of the ultimate tensile stress with an R-ratio of 0.1 for the build orientation XZY. The contour thickness and raster thickness were increased to 0.030 in. to determine the effect of those two build parameters on tension-tension fatigue life. Next, the modified Goodman approach was used to estimate the fully reversed (R=-1) fatigue life. The initial data suggested that the modified Goodman approach was very conservative. Therefore, four different stress levels of 25%, 20%, 15% and 10% of ultimate tensile stress were used to characterize the fully reversed fatigue properties. Because of the extreme conservatism of the modified Goodman model for this material, a simple phenomenological model was developed to estimate the fatigue life of ULTEM 9085 subjected to fatigue at different R-ratios.Master of Science
13
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.
Abstract (sommario):
Thesis (D. Tech. ( Mechanical Engineering )) - Central University of technology, Free State, 2012In 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.
14
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.
Abstract (sommario):
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.
15
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.
16
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.
Abstract (sommario):
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%.
17
Foschini, Alessandro. "Application of Additive Manufacturing to long fibers Metal Matrix Composites". Master's thesis, Alma Mater Studiorum - Università di Bologna, 2017.
Abstract (sommario):
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.
18
Hussein, Ahmed Yussuf. "The development of lightweight cellular structures for metal additive manufacturing". Thesis, University of Exeter, 2013. http://hdl.handle.net/10871/15023.
Abstract (sommario):
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).
19
Valli, Giuseppe <1989>. "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.
Abstract (sommario):
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.
20
Habib, MD Ahasan. "Designing Bio-Ink for Extrusion Based Bio-Printing Process". Diss., North Dakota State University, 2019. https://hdl.handle.net/10365/32045.
Abstract (sommario):
Tissue regeneration using in-vitro scaffold becomes a vital mean to mimic the in-vivo counterpart due to the insufficiency of animal models to predict the applicability of drug and other physiological behavior. Three-dimensional (3D) bio-printing is an emerging technology to reproduce living tissue through controlled allocation of biomaterial and cell. Due to its bio-compatibility, natural hydrogels are commonly considered as the scaffold material in bio-printing process. However, repeatable scaffold structure with good printability and shape fidelity is a challenge with hydrogel material due to weak bonding in polymer chain. Additionally, there are intrinsic limitations for bio-printing of hydrogels due to limited cell proliferation and colonization while cells are immobilized within hydrogels and don’t spread, stretch and migrate to generate new tissue. The goal of this research is to develop a bio-ink suitable for extrusion-based bio-printing process to construct 3D scaffold. In this research, a novel hybrid hydrogel, is designed and systematic quantitative characterization are conducted to validate its printability, shape fidelity and cell viability. The outcomes are measured and quantified which demonstrate the favorable printability and shape fidelity of our proposed material. The research focuses on factors associated with pre-printing, printing and post-printing behavior of bio-ink and their biology. With the proposed hybrid hydrogel, 2 cm tall acellular 3D scaffold is fabricated with proper shape fidelity. Cell viability of the proposed material are tested with multiple cell lines i.e. BxPC3, prostate stem cancer cell, HEK 293, and Porc1 cell and about 90% viability after 15-day incubation have been achieved. The designed hybrid hydrogel demonstrate excellent behavior as bio-ink for bio-printing process which can reproduce scaffold with proper printability, shape fidelity and higher cell survivability. Additionally, the outlined characterization techniques proposed here open-up a novel avenue for quantifiable bio-ink assessment framework in lieu of their qualitative evaluation.
21
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.
Abstract (sommario):
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.
22
Butt, Javaid. "A novel additive manufacturing process for the production of metal parts". Thesis, Anglia Ruskin University, 2016. http://arro.anglia.ac.uk/701001/.
Abstract (sommario):
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.
23
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.
24
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/.
Abstract (sommario):
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.
25
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.
Abstract (sommario):
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.
26
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.
Abstract (sommario):
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.
27
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.
28
Kwan, Isabella. "Cellulose and polypropylene filament for 3D printing". Thesis, KTH, Skolan för kemivetenskap (CHE), 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-195829.
Abstract (sommario):
Additive manufacturing has become a very popular and well mentioned technique in recent years. The technique, where 3 dimensional (3D) printing is included, creates opportunities to develop new designs and processing systems. As a research institute within the forest based processes and products, Innventia AB has an idea of combining 3D printing with cellulose. The addition of cellulose will increase the proportion of renewable raw material contributing to more sustainable products. However, when cellulose is added the composition of the filaments changes. The main aim for the project is to devise methodologies to improve properties of composite filaments used for 3D printing. Filament in 3D printing refers to a thread-like object made of different materials, such as PLA and ABS, that is used for printing processes. A literature study was combined with an extensive experimental study including extrusion, 3D printing and a new technique that was tested including 3D scanning for comparing the printed models with each other. The extruding material consisted of polypropylene and cellulose at different ratios, and filaments were produced for 3D printing. The important parameters for extruding the material in question was recorded. Because the commingled material (PPC) was in limited amount, UPM Formi granulates, consisting of the same substances, was used first in both the extrusion and printing process. Pure polypropylene filaments were also created in order to strengthen the fact that polypropylene is dimensional unstable and by the addition of cellulose, the dimensional instability will decrease. After producing filaments, simple 3D models were designed and printed using a 3D printing machine from Ultimaker. Before starting to print, the 3D model needed to be translated into layer-by-layer data with a software named Cura. Many parameters were vital during printing with pure polypropylene, UPM and PPC. These parameters were varied during the attempts and marked down for later studies. With the new technique, in which 3D scanning was included, the 3D printed models were compared with the original model in Cura in order to overlook the deformation and shape difference. The 3D scanner used was from Matter and Form. Photographs of the printed models, results from the 3D scanner, and screenshots on the model in Cura were meshed together, in different angles, using a free application named PicsArt. The result and conclusion obtained from all three parts of the experimental study was that polypropylene’s dimensional stability was improved after the addition of cellulose, and the 3D printed models’ deformation greatly decreased. However, the brittleness increased with the increased ratio of cellulose in the filaments and 3D models.Additiv tillverkning har på den senare tiden blivit en mycket populär och omtalad teknik. Tekniken, där tredimensionell (3D) utskrivning ingår, ger möjligheter att skapa ny design och framställningstekniker. Som ett forskningsinstitut inom massa- och pappersindustrin har Innventia AB en ny idé om att kombinera 3D-utskrivning med cellulosa. Detta för att höja andelen förnybar råvara som leder till mer hållbara produkter. Dock kommer filamentens sammansättning vid tillsättning av cellulosa att ändras. Det främsta syftet med detta projekt är att hitta metoder för att förbättra egenskaperna hos de kompositfilament som används för 3D-utskrifter. Filament inom 3D-utskrivning är det trådlika objektet gjort av olika material, såsom PLA och ABS, som används vid utskrivningsprocessen. En enkel litteraturstudie kombinerades med en experimentell studie. Det experimentella arbetet var i fokus i detta projekt som omfattade extrudering, 3D-utskrivning samt en ny teknik som prövades, där 3D-scanning ingick, för att jämföra de utskrivna modellerna med varandra. Extruderingsmaterialet bestod av polypropen och cellulosa av olika halter, och av detta material tillverkades filament för 3D-utskrivning. De viktiga parametrarna för extrudering med det önskade materialet antecknades. Eftersom mängden cominglat material (PPC) var begränsat, användes först UPM Formi granuler, som består av samma substanser som i PPC, i både extruderingen och utskrivningen. Filament av ren polypropen tillverkades också för att stärka det faktum att polypropen är dimensionellt instabil. Genom att tillsätta cellulosa minskades dimensionsinstabiliteten. Efter att filamenten hade tillverkats, designades enkla 3D-modeller för utskrivning med en 3D-utskrivare från Ultimaker. Innan utskrivningen kunde börja behövde 3D-modellen bli översatt till lager-på-lager-data med hjälp av en programvara vid namn Cura. Många parametrar är viktiga vid utskrivning med ren polypropen, UPM samt PPC. Temperatur och hastighet varierades för de olika försöken och antecknades för senare studier.Med den nya tekniken, där 3D-scanning ingår, jämfördes de utskrivna 3D-modellerna med originalmodellen i Cura för att se över deformationen och formskillnaden. Den 3D-scanner som användes kom från Matter and Form. Fotografier på de utskrivna modellerna, resultaten från 3D-scannern och bilder på modellerna i Cura sammanfogades i olika vinklar med hjälp av ett gratisprogram som heter PicsArt. Det resultat som erhölls och den slutsats som kunde dras utifrån alla tre delarna av den experimentella studien var att polypropens dimensionsinstabilitet minskades efter tillsatsen av cellulosa, och att de 3D-utskrivna modellernas deformation minskade kraftigt. Skörheten ökade ju högre halt cellulosa som filamenten och de utskrivna modellerna innehöll.
29
Jiang, Sheng. "Processing rate and energy consumption analysis for additive manufacturing processes : material extrusion and powder bed fusion". Thesis, Massachusetts Institute of Technology, 2017. http://hdl.handle.net/1721.1/111753.
Abstract (sommario):
Thesis: S.M., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2017.Cataloged from PDF version of thesis.
Includes bibliographical references (pages 111-116).
Additive technologies have given birth to an expanding industry now worth 5.1 billion dollars. It has been adopted widely in design and prototyping as well as manufacturing fields. Compared to conventional technologies, additive manufacturing technologies provides opportunity to print unique complex-shaped geometries. However, it also suffers from slow production rate and high energy consumption. Improving the rate and energy becomes an important issue to make additive manufacturing competitive with conventional technologies. Among all the different limiting factors including printing strategy, heat transfer and mechanical movement limitations, heat transfer is the fundamental limiting barrier preventing further improvement the production rate. This thesis looks at the heat transfer mechanisms in material extrusion and powder bed fusion processes. In all the models developed for these two processes, processing rate is bounded by an adiabatic rate limit at which all the input energy is perfectly utilized to heat up the material to its molten/flowable state. In material extrusion, fused deposition technology suffers low throughput due to poor conductive heat transfer, big area additive manufacturing technology achieves high throughput by introducing viscous heating at the cost of resolution. In powder bed fusion, due to the intensive laser heating, the process window is limited to ensure high density material while avoid excessive evaporation. Further study quantifies the inefficiency from heat transfer mechanisms which leads to lower processing rates than the adiabatic rate limit. Energy consumption for material extrusion and powder bed fusion machines are reviewed to evaluate significance of energy consumed to heat up the material. For fused deposition technology, most of the energy is consumed by environment heating; while for powder bed fusion technology, laser unit takes the most energy. Life cycle energy consumption for products made with powder bed fusion process is compared with same/similar parts made from conventional manufacturing processes to explore scenarios in which manufacturing with additive technologies is less energy intensive.
by Sheng Jiang.
S.M.
30
D'Amico, Tone Pappas. "Predicting Process and Material Design Impact on and Irreversible Thermal Strain in Material Extrusion Additive Manufacturing". Digital WPI, 2019. https://digitalcommons.wpi.edu/etd-dissertations/572.
Abstract (sommario):
Increased interest in and use of additive manufacturing has made it an important component of advanced manufacturing in the last decade. Material Extrusion Additive Manufacturing (MatEx) has seen a shift from a rapid prototyping method harnessed only in parts of industry due to machine costs, to something widely available and employed at the consumer level, for hobbyists and craftspeople, and industrial level, because falling machine costs have simplified investment decisions. At the same time MatEx systems have been scaled up in size from desktop scale Fused Filament Fabrication (FFF) systems to room scale Big Area Additive Manufacturing (BAAM). Today MatEx is still used for rapid prototyping, but it has also found application in molds for fiber layup processes up to the scale of wind turbine blades. Despite this expansion in interest and use, MatEx continues to be held back by poor part performance, relative to more traditional methods such as injection molding, and lack of reliability and user expertise. In this dissertation, a previously unreported phenomenon, irreversible thermal strain (ITε), is described and explored. Understanding ITε improves our understanding of MatEx and allows for tighter dimensional control of parts over time (each of which speaks to extant challenges in MatEx adoption). It was found that ITε occurs in multiple materials: ABS, an amorphous polymer, and PLA, a semi-crystalline one, suggesting a number of polymers may exhibit it. Control over ITε was achieved by tying its magnitude back to part layer thickness and its directionality to the direction of roads within parts. This was explained in a detail by a micromechanical model for MatEx described in this document. The model also allows for better description of stress-strain response in MatEx parts broadly. Expanding MatEx into new areas, one-way shape memory in a commodity thermoplastic, ABS, was shown. Thermal history of polymers heavily influences their performance and MatEx thermal histories are difficult to measure experimentally. To this end, a finite element model of heat transfer in the part during a MatEx build was developed and validated against experimental data for a simple geometry. The application of the model to more complex geometries was also shown. Print speed was predicted to have little impact on bonds within parts, consistent with work in the literature. Thermal diffusivity was also predicted to have a small impact, though larger than print speed. Comparisons of FFF and BAAM demonstrated that, while the processes are similar, the size scale difference changes how they respond to process parameter and material property changes, such as print speed or thermal diffusivity, with FFF having a larger response to thermal diffusivity and a smaller response to print speed. From this experimental and simulation work, understanding of MatEx has been improved. New applications have been shown and rational design of both MatEx processes and materials for MatEx has been enabled.
31
Baich, Liseli Jeanette. "Impact of Infill Design on Mechanical Strength and Production Cost in Material Extrusion Based Additive Manufacturing". Youngstown State University / OhioLINK, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=ysu1485161020020828.
32
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/.
Abstract (sommario):
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.
33
Shivananda, Sripada. "Virtual manufacturing on the Web extrusion die design". Ohio : Ohio University, 1998. http://www.ohiolink.edu/etd/view.cgi?ohiou1176398269.
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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.
Abstract (sommario):
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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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.
Abstract (sommario):
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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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.
Abstract (sommario):
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.
37
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.
38
Woods, Benjamin Samuel. "Enhancing the Capabilities of Large-Format Additive Manufacturing Through Robotic Deposition and Novel Processes". Thesis, Virginia Tech, 2020. http://hdl.handle.net/10919/98843.
Abstract (sommario):
The overall goal of this research work is to enhance the capabilities of large-format, polymer material extrusion, additive manufacturing (AM) systems. Specifically, the aims of this research are to (1) Construct, and develop a robust workflow for, a large-format, robotic, AM system; (2) Develop an algorithm for determining and relaying proper rotation commands for 5 degree of freedom (DoF) multi-axis deposition; and (3) Create a method for printing a removable support material in large-format AM. The development and systems-integration of a large-format, pellet-fed, polymer, material extrusion (ME), AM system that leverages an industrial robotic arm is presented. The robotic arm is used instead of the conventional gantry motion stage due to its multi-axis printing ability, ease of tool changes for multi-material deposition and/or subtraction, and relatively small machine footprint. A novel workflow is presented as a method to control the robotic arm for layer-wise fabrication of parts, and several machine modifications and workflow enhancements are presented to extend the multi-axis manufacturing capabilities of the robot. This workflow utilizes existing AM slicers to simplify the motion path planning for the robotic arm, as well as allowing the workflow to not be restricted to a single robotic deposition system.
To enable multi-axis deposition, a method for generating tool orientations and resulting deposition toolpaths from a geometry's STL file was developed for 5-DoF conformal printing and validated via simulation using several different multi-DOF robotic arm platforms. Furthermore, this research proposes a novel method of depositing a secondary sacrificial support material was created for large-format AM to enable the fabrication of complex geometries with overhanging features. This method employs a simple tool change to deposit a secondary, water-soluble polymer at the interfaces between the part and supporting structures. In addition, a means to separate support material into smaller sections to extend the range of geometries able to be manufactured via large-format AM is presented. The resultant method was used to manufacture a geometry that would traditionally be considered unprintable on conventional large-format AM systems.Master of Science
Additive manufacturing (AM), also known as 3D printing, is a method of manufacturing objects in a layer-by-layer technique. Large-format AM is typically defined as an AM system that can create an object larger than 1 m3. There are only a few manufacturers in the world of these systems, and all currently are built on gantry-based motion stages that only allow movement of the printer in three principal axes (X, Y, Z). The primary goal of this thesis is to construct a large-format AM system that uses a robotic arm to enable printing in any direction or orientation. The use of an industrial robotic arm enables printing in multiple planes, which can be used to print structures without support structures, print onto curved surfaces, and to purt with curved layers which produces a smoother external part surface. The design of the large-format AM system was validated through successful printing of objects as large as 1.0x0.5x1.2 m, simultaneous printing of a sacrificial support material to enable overhanging features, and through completing multi-axis printing. To enable multi-axis printing, an algorithm was developed to determine the proper toolpath location and relative orientation to the part surface. Using a part's STL file as input, the algorithm identifies the normal vector at each movement command, which is then used to calculate the required tool orientation. The tool orientations are then assembled with the movement commands to complete the multi-axis toolpath for the robot to perform. Finally, this research presents a method of using a second printing tool to deposit a secondary, water-soluble material to act as supporting structures for overhanging and bridging part features. While typical 3D printers can generally print sacrificial material for supporting overhangs, large-format printers produce layers up to 25 mm wide, rendering any support material impossible to remove without post-process machining. This limits the range of geometries able to be printed to just those with no steep overhangs, or those where the support material is easily reachable by a tool for removal. The solution presented in this work enables the large scale AM processes to create complex geometries.
39
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.
Abstract (sommario):
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.
40
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.
Abstract (sommario):
2016 - 2017In 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.
41
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.
Abstract (sommario):
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.
42
Raynaud, Jonathan. "Elaboration de pièces 3D multimatériaux par fabrication additive". Thesis, Limoges, 2019. http://www.theses.fr/2019LIMO0101.
Abstract (sommario):
Actuellement, les pièces HTCC et LTCC (High and Low Temperature Co-fired Ceramics) sont élaborées selon deux procédés : le coulage en bande pour le substrat diélectrique en céramique et la sérigraphie pour la réalisation des pistes et vias métalliques. Un procédé de fabrication additive hybride, capable de construire une pièce 3D en céramique / métal, pourrait trouver un intérêt majeur dans la fabrication de composants utilisés en micro-électroniques. En effet, un des principaux avantages de la fabrication additive est de pouvoir réaliser des géométries qui ne peuvent actuellement pas être obtenues en micro-électronique, ce qui permettrait d’obtenir un gain de performances comparé aux circuits actuels. L’objectif de ce travail est de proposer un nouveau procédé d’obtention de pièces monolithiques multimatériaux utilisant le couplage de deux technologies de fabrication additive .Une stratégie combinant la stéréolithographie et la micro-extrusion est proposée pour la fabrication de pièces multimatériaux HTCC et LTCC. Les pièces modèles sont des circuits électroniques dans les trois dimensions de l’espace comprenant un substrat diélectrique ainsi que des pistes horizontales et des vias. Des structures innovantes ont également été construites (blindage continus et vias obliques). La caractérisations de ces composants conduit à des valeurs similaires à celles des HTCC et LTCC réalisés par des procédés conventionnelsCurrently, HTCC and LTCC (High and Low Temperature Co-fired Ceramics) parts are produced by two processes: tape casting for the dielectric ceramic part and screen printing for the realization of metal tracks and vias. The main objective of this work is to propose a new process for obtaining monolithic multi-material parts using the coupling of two additive manufacturing technologies. In this respect, a hybrid additive manufacturing process capable of building a 3D ceramic / metal part could be of major interest in the manufacture of such electronic components. Stereolithography and robocasting seem to be complementary processes to achieve this goal. The advantage of using additive manufacturing instead of conventional methods is to be able to achieve forms that can not currently be obtained in microelectronics, which would allow a performance gain compared to current circuits. A strategy combining stereolithography and robocasting is proposed for the simple manufacture of HTCC and LTCC multi-material parts. The model parts are electronic circuits in the three dimensions of the space including a dielectric substrate as well as horizontal tracks and vias. To improve the performance of current circuits new geometries are being studied, such as armored or inclined vias. They will then be characterized in microwave to verify the application of selected materials in these frequency ranges
43
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.
Abstract (sommario):
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.
44
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.
Abstract (sommario):
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.
45
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.
Abstract (sommario):
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/.
Abstract (sommario):
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.
47
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.
Abstract (sommario):
Thesis: Nav. E., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2019Thesis: 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
48
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.
Abstract (sommario):
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.
49
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.
Abstract (sommario):
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.
50
Gingerich, Mark Bryant. "Joining Carbon Fiber and Aluminum with Ultrasonic Additive Manufacturing". The Ohio State University, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=osu1461161262.