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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
251

Design Optimization of Heat Transfer and Fluidic Devices by Using Additive Manufacturing

Kumar, Nikhil, Kumar, Nikhil January 2016 (has links)
After the development of additive manufacturing technology in the 1980s, it has found use in many applications like aerospace, automotive, marine, machinery, consumer and electronic applications. In recent time, few researchers have worked on the applications of additive manufacturing for heat transfer and fluidic devices. As the world has seen a drastic increase in population in last decades which have put stress on already scarce energy resources, optimization of energy devices which include energy storing devices, heat transfer devices, energy capturing devices etc. is need for the hour. Design of energy devices is often constrained by manufacturing constraints thus current design of energy devices is not an optimized one. In this research we want to conceptualize, design and manufacture optimized heat transfer and fluidic devices by exploiting the advantages provided by additive manufacturing. We want to benefit from the fact that very intricate geometry and desired surface finish can be obtained by using additive manufacturing. Additionally, we want to compare the efficacy of our designed device with conventional devices. Work on usage of Additive manufacturing for increasing efficiency of heat transfer devices can be found in the literature. We want to extend this approach to other heat transfer devices especially tubes with internal flow. By optimizing the design of energy systems we hope to solve current energy shortage and help conserve energy for future generation.We will also extend the application of additive manufacturing technology to fabricate "device for uniform flow distribution".
252

Evaluation of Microstructural and Mechanical Properties of Multilayered Materials

Subedi, Samikshya 01 February 2017 (has links)
Microstructure controls many physical properties of a material such as strength, ductility, 1density, conductivity, which, in turn, determine the application of these materials. This thesis work focuses on studying microstructural features (such as grain size, shape, defects, orientation gradients) and mechanical properties (such as hardness and yield strength) of multilayered materials that have undergone different loading and/or operating conditions. Two materials that are studied in detail are 18 nm Cu-Nb nanolaminates and 3D printed Inconel 718. Copper-Niobium (Cu-Nb) nanolaminate is a highly stable, high strength, nuclear irradiation resistant composite, which is destabilized with application of high pressure torsion (HPT). This work focuses on understanding the deformation and failure behavior of Cu-Nb using a novel orientation mapping technique in transmission electron microscopy in (TEM) called Automated Crystal Orientation Mapping (ACOM) and Digistar (ASTARTM) or Precession Electron Diffraction (PED). A new theory is postulated to explain strengthening mechanisms at the nanoscale using a data analytics approach. In-situ TEM compression and tensile testing is performed to image dislocation movement with the application of strain. This experiment was performed by Dr. Lakshmi Narayan Ramasubramanian at Xi’an Jiaotong University in China. Another major aspect of this research focuses on the design, fabrication, and microstructural characterization of 3D printed Inconel 718 heat exchangers. Various heat exchanger designs, machine resolution, printing techniques such as build orientation, power, and velocity of the laser beam are explored. Microstructural and mechanical properties of printed parts (before and after heat treatment) are then analyzed to check consistency in grain size, shape, porosity, hardness in relation to build height, scan parameters, and design. Various tools have been utilized such as scanning electron microscopy (SEM), electron backscatter diffraction (EBSD), x-ray computed microtomography (at Advanced Photon Source at Argonne National Lab), hardness and micro-pillar compression testing for this study.
253

A material study of insoles : Manufactured using different methods

Hermansson, Erik, Marcus, Ekberg January 2019 (has links)
Aim: The aim of this study is to evaluate if additive manufacturing (AM) is an appropriate manufacturing method for insoles in comparison to vacuum forming (VF) and subtractive manufacturing (SM) in regards of material properties such as abrasion resistance. Background: Traditionally insoles are manufactured with either VF or SM. AM has been around for some decades but implementation into orthotic and prosthetic (O&P) business has not been accomplished yet. Therefore, the quality of the products produced with AM must be tested in comparison with traditional methods. Method: A comparison of samples for the mentioned manufacturing methods was done with the help of an abrasion testing machine with the standard ASTM G133. Two samples were produced from each manufacturing method and respectively tested for one and two hours. All the samples were weighed before and after the tests with the help of a four decimal scale. The difference in weight before and after the test and coefficient of friction was evaluated. The weight difference was analyzed to see how much material had been removed from the sample. The percentage of wear loss was calculated for each specific sample, both for one hour and two hours of testing. No statistical analysis could be made due to the limited amount of samples and testing time. Result: No statistically significant could be found for either wear loss or the coefficient of friction as mentioned above. Conclusion: A conclusion whether which material having the best abrasion resistance for respectively manufacturing method could not be drawn due to limited results. This study can be seen as a pilot study where the methodology can be used in further studies. Further research on AM needs to be conducted.
254

Audi Uno : A symbiotic car

Nagre, Gaurang January 2016 (has links)
Abstract When we paint a nebulous future of tomorrow based on the research dictated by the available resources, we see a marathon run for the future that instigates new opportunities for the automotive industry with additive manufacturing. Cars of today are a product of subtractive manufacturing; but in future 3D printing would empower us to define a novel architecture that provokes the construction of the interior, exterior and the powertrain in one piece allowing us to celebrate the marriage between all three key components. Project UNO, meaning - ‘one’, exhibits this new architecture through a semi-autonomous concept that exaggerates the feeling of sportiness with a suspended cabin. In the autonomous mode the cabin moves around in the boundary of the exterior to enhance the g-forces by thrusting the cabin forward while accelerating, backward while braking and tilting while cornering. Therefore, the sporty nature of the design can be celebrated actively in both modes. Inspiration and Method The process was cut up into two palpable routes. The former dealt with a system level approach where the present cardinal building blocks of automotive manufacturing were rearranged with the new cues derived from additive manufacturing techniques to render a new system level solution. The later was aimed at advocating a tangible solution that best delineated this idea. Ten radical themes were generated that helped showcase the marriage between the three key components - exterior, interior and powertrain. The final theme was inspired by the analogy of an egg where the yolk moves freely within the egg white. This metaphor was then applied to the cabin experience in the autonomous mode. The occupant in the manual driven mode can cherish the full potential of the car to procure a sporty experience outside the city. While in the city, the autonomous mode seizes control and instigates the movement of the cabin within the perimeter of the exterior to amplify the g-forces by thrusting the cabin forward while accelerating, backwards while braking and tilting it while cornering. Result Concept UNO celebrates the marriage between the exterior, the interior and the powertrain that best encapsulates the process of additive manufacturing where cars would be grown and not assembled. The interior tub is reposed inside the exterior shell with the aid of six mechanical joints and is not adhered to the floor of the car. The gap around the cabin exaggerates the feel of a floating island that can shift freely. The cabin is composed of smart glass which renders opaque when an electric current is passed through it and turns transparent when the car is parked gravitating people to yield a glimpse of the interior. The bottom of the cabin is reflected by the gloss finish of the chassis unit that amplifies the floating feeling. A warm white was used to grant the concept a more puristic look while making it seem warm and friendly. The idea was then showcased through a 1:4 scale model printed in one piece using a Selective Laser Sintering (SLM) technique.
255

Etude de nanocomposites basés sur des alliages PLA/PA11 / Study of nanocomposites based on PLA/PA11 polymer blends

Rasselet, Damien 10 January 2019 (has links)
L’acide polylactique (PLA) est l’un des polymères biosourcés qui suscite le plus d’intérêt, mais ses propriétés thermomécaniques nécessitent d’être améliorées. Pour ce faire, les méthodes les plus utilisées et étudiées sont de le mélanger avec d’autres polymères ou bien d’y ajouter des charges minérales nanométriques (nanoparticules), afin de constituer un nanocomposite à matrice PLA. C’est dans la combinaison de ces deux approches que s’inscrivent ces travaux de thèse, consacrés à l’élaboration et à la caractérisation des propriétés de nanocomposites à base d’un alliage de PLA et de polyamide 11 (PA11) 80/20 m/m. L’objectif de cette thèse est l’obtention d’un matériau biosourcé aux propriétés thermiques, mécaniques et de réaction au feu améliorées par le contrôle de sa morphologie et l’ajout de nanoparticules et de retardateurs de flamme (RF). Pour y parvenir, deux techniques de compatibilisation, destinées à améliorer l’adhésion interfaciale entre le PLA et le PA11, ont été évaluées. La première consistait à incorporer des nanoparticules de silice. Il a été noté d’importantes modifications de la morphologie et des propriétés rhéologiques du mélange d’étude, selon leur localisation dans le mélange étudié fonction de la nature chimique de la surface de la silice. La deuxième consistait à introduire un copolymère époxyde multifonctionnel réactif, dénommé Joncryl. La réactivité de ce copolymère avec le PLA et le PA11 a permis de compatibiliser le mélange d’étude, conduisant à une morphologie plus fine et à l’obtention de propriétés mécaniques supérieures à celles du mélange d’étude, en particulier avec l’ajout de 3%m de Joncryl. Des échantillons basés sur les mélanges compatibilisés par cette méthode ont été préparés par le procédé de fabrication additive FDM. Une étude de l’impact de ce procédé sur la morphologie et les propriétés mécaniques obtenues a été entreprise. Enfin, une meilleure réaction au feu pour le mélange compatibilisé avec 3%m de Joncryl a pu être obtenue par l’ajout combiné de nanoparticules de phyllosilicates et de RF. / Polylactic acid (PLA) is one of the biobased polymers that generates the most interest, but its thermomechanical properties need to be improved. To do that, the most used and studied methods consist of blending PLA with other polymers or adding nanoscaled mineral fillers (nanoparticles) to get a PLA based nanocomposite. This PhD work is dedicated to the elaboration and properties characterization of nanocomposites based on a filled PLA and polyamide 11 80/20 wt/wt blend. The aim is to obtain a biobased material with improved thermal, mechanical and fire reaction properties by controlling its morphology through the addition of nanoparticles and flame retardants additives.To achieve that, two compatibilization techniques, aiming to improve PLA-PA11 interfacial adhesion, were evaluated. The first one consisted of adding silica nanoparticles. Important changes of the blend morphology and rheological properties were noticed, depending on the localization of the two different silica nanoparticles used into the polymer blend phases. The second one consisted of introducing a reactive multifunctional epoxy copolymer, named Joncryl. The reactivity of this copolymer with PLA and PA11 allowed to compatibilize the blend, leading to a fine morphology and higher mechanical properties compared to those of the pristine blend. Samples of compatibilized blends obtained through this method were processed using FDM additive manufacturing process. A study of the influence of this process on the morphology and mechanical properties obtained for these samples was performed. Finally, a better fire reaction of compatibilized polymer blend with 3%wt Joncryl was obtained by the combined addition of phyllosilicates nanoparticles and flame retardants.
256

Méthodologie de caractérisation prédictive des procédés de fabrication additive avec une approche technique, économique et environnementale / Methodology of predictive characterization of additive manufacturing processes with a technical, economic and environmental approach

Yosofi, Mazyar 24 October 2018 (has links)
L'Organisation des Nations Unies vise à moderniser les industries afin de les rendre durables et plus respectueuse de l'environnement d'ici 2030. Afin de répondre à ces attentes, il faut mettre en place des voies d'améliorations des procédés de fabrication d'un point de vue environnemental. Cette démarche nécessite une connaissance fine des flux entrants et sortants lors de la fabrication d'un produit. Néanmoins, ce n'est pas le cas pour les procédés de fabrication additives ou les impacts environnementaux générés lors de la fabrication d'un produit sont encore méconnus. Par conséquent, il est primordial de bien "compter" les différentes sources de consommations et de rejets. Pour cela, une évaluation quantitative des flux intervenants pendant la fabrication de pièces est nécessaire pour améliorer la connaissance de la performance environnementale d'un procédé. Les travaux de cette thèse portent sur la proposition d'une méthodologie d'évaluation multicritère pour les procédés de fabrication additive afin de pouvoir prédire, dès l'étape de conception d'un produit, des informations sur les aspects techniques, économiques et environnementaux du couple pièce/procédé. Afin de proposer aux concepteurs la possibilité d'évaluer un produit dès son étape de conception, des modèles de consommation fins traduisant le comportement du procédé ont été mis en place. La méthodologie développée s’intéresse à l'ensemble des sources de consommation et de rejets ainsi qu'à l'ensemble des étapes nécessaires à la fabrication d'une pièce mécanique.Ce manuscrit est divisé en six chapitres qui permettent de présenter le contexte général de l'étude, l'état de l'art, la méthodologie d'évaluation multicritère, l'application sur les procédés de fabrication additive et l'exploitation sur un cas industriel. Le dernier chapitre se consacre à la conclusion sur les apports de ces travaux et propose des perspectives de recherche. / The United Nations aims to modernize industries in order to make them sustainable and more environmentally friendly by 2030. In order to meet these expectation, it is necessary to put in place ways of improving production processes from an environmental point of view. This approach requires a detailed knowledge of the incoming and outgoing flows during the manufacturing of a product. However, this is not the case for additive manufacturing processes where the environmental impacts generated during this stage are still unknown. For that, a quantitative evaluation of the flows involved during the manufaturing of parts is necessary in order to improve the knowledge of the environmental performance of a process. The work of this thesis focuses on the development of methodology for additive manufacturing processes in order to predict information on the technical, economic, and environmental aspects of a product during the design stage of a part. The methodology developped is increasingly interested in all the sources of consumption as well as all the stages necessary for the manufacturing of a mechanical part.This manuscript is divided into six chapters that can present the general context of the study, the state of the art, the methodology developped, a application of the methodology to additive manufacturing processes and the computer tool developed during this thesis. The last chapter is devoted to the conclusion on the contributions of this work and provides research perspectives.
257

Conventional heat treatment of additively manufactured AlSi10Mg

Sarentica, Atilla January 2019 (has links)
No description available.
258

Study on the machinability and surface integrity of Ti6Al4V produced by Selective Laser Melting (SLM) and Electron Beam Melting (EBM) processes / Pas de titre fourni

Milton, Samuel 28 May 2018 (has links)
Les technologies de fabrication additive(FA) basées sur la technique de fusion laser sur lit de poudres, telles que les procédés de fusion sélective laser (Selective Laser Melting ‘SLM’) et de fusion par faisceau d'électrons (Electron Beam Melting ‘EBM’), ne cessent de se développer afin de produire des pièces fonctionnelles principalement dans les domaines aérospatial et médical. Le procédé de fabrication additive offre de nombreux avantages, tels que la liberté de conception, la réduction des étapes de fabrication, la réduction de la matière utilisée, et la réduction de l'empreinte carbone lors de la fabrication d'un composant. Néanmoins, les pièces obtenues nécessitent une opération d’usinage de finition afin de satisfaire les tolérances dimensionnelles et l’état de surface. / Additive Manufacturing (AM) techniques based on powder bed fusion like Selective Laser Melting(SLM) and Electron Beam Melting processes(EBM) are being developed to make fully functional parts mainly in aerospace and medical sectors. There are several advantages of using AM processes like design freedom, reduced process steps, minimal material usage and reduced carbon footprint while producing a component. Nevertheless, the parts are built with near net shape and then finish machined to meet the demands of surface quality and dimensional tolerance.
259

Lead-time reduction and rapid prototyping of tools and fixtures, therefore I AM : A case study about additive manufacturing in the automotive industry

Gustafsson, Christopher January 2019 (has links)
The purpose of this thesis is to investigate how to decrease lead-times of conventionally manufactured prototypes of tools and fixtures. Which could lead to increased knowledge of how an operations site within the automotive industry could utilize additive manufacturing when producing company specific prototypes of tools and fixtures.  The research approach applied in this case study combines a literature review to systematically find relevant literature aligned with the research topic of additive manufacturing or 3D printing related to lead-time reduction and generative design terms. With the help of interviews and observations profound knowledge was gained as preparation before continuing the research. Thereafter, a pre-study was conducted in order to further enhance the understanding of the industrial context of the two chosen fixtures (study objects). Rapid prototyping activities with additive manufacturing processes and technologies of experimentation character was conducted iteratively with both 3D CAD and 3D printing software and hardware. Analysis of the data was conducted through a comparison between lead-times of conventionally manufactured and 3D printed prototypes of the two chosen fixtures. Moreover, identifying potential effects with additive manufacturing of prototypes have with a SWOT analysis.  The case study found that additive manufacturing could significantly decrease lead-times when producing prototypes compared to conventional manufacturing. Furthermore, the results showed that the effects of additive manufacturing are plenty and rather complex due to the fact of this new way to manufacture prototypes. Therefore, the term design for additive manufacturing need first class priority if next steps were to be taken in the additive manufacturing field to enhance industrial and academic benefits.  The research on this subject is strongly constrained by the scarcity of empirical experience and, consequently, by the scarcity of available empirical data. Research publication on the topic are fruitful and plenty but their findings specified to their chosen study objects. This case study gives an up-to-date contribution to the topic of additive manufacturing with endless possibilities to reduce lead-time with rapid prototyping activities that utilizes additive manufacturing. Moreover, the research approach used in this thesis combines 3D CAD data through theoretical concepts and physical objects with additive manufacturing practice. Overall, the results can be used to improve academic research in the topic and promote discussion among different actors entering or within the additive manufacturing field.
260

Modelo de processo de avaliação para adoção de manufatura aditiva na indústria de alto valor agregado. / Process model to evaluate additive manufacturing adoption in high value added industries.

Mançanares, Cauê Gonçalves 13 May 2016 (has links)
Manufatura aditiva é um processo de fabricação de objetos que tem chamado a atenção de acadêmicos, empresas e órgãos de governo. Alguns setores específicos possuem demandas que podem ser mais bem atendidas com a utilização da manufatura aditiva na produção de peças de alto valor agregado. O problema prático que motiva a realização deste trabalho é a dificuldade enfrentada pelas empresas em avaliar as tecnologias de manufatura aditiva existentes para decisão de adoção ou não adoção delas em seus fluxos produtivos. A análise da situação atual na literatura indica que falta um modelo de processo específico de avaliação para adoção da manufatura aditiva na indústria de alto valor agregado. Visando preencher essa lacuna e propor uma solução para o problema identificado, este trabalho tem como objetivo a definição de um modelo de processo específico de avaliação para adoção de manufatura aditiva na indústria de alto valor agregado. Tal modelo é desenvolvido a partir de modelos de processo existentes para avaliar a adoção de outras tecnologias de manufatura avançada (Advanced Manufaturing Technologies - AMTs) e do levantamento das características específicas da manufatura aditiva. O modelo de processo de avaliação para adoção da manufatura aditiva na indústria de alto valor agregado proposto contempla nove passos para decidir sobre a adoção ou a não adoção da manufatura aditiva. A aplicabilidade do modelo proposto foi avaliada por meio de entrevistas com especialistas. A avaliação dos resultados indica que os passos e as atividades propostos no modelo contribuem para auxiliar na avaliação para adoção da manufatura aditiva na indústria de alto valor agregado. / Additive manufacturing is a manufacturing process that has gained attention of scholars, companies and government bodies. Some specific sectors have demands that can be better met with the use of additive manufacturing to produce high added value parts. The practical problem that motivates this work is the difficulty met by companies in assessing additive manufacturing technologies for decision to adopt or not adopt them in their production flows. The analysis of the current situation in the literature indicates a gap of a specific process model to evaluate the adoption of additive manufacturing in the high added value industry. To fill this gap and to propose a solution for the identified problem, this work has the goal to define a specific process model to evaluate the adoption of additive manufacturing in the high added value industry. This model is developed based on existing process models to evaluate the adoption of other Advanced Manufacturing Technologies and the study of specific characteristics of additive manufacturing. The model proposed contemplates nine steps to decide on the adoption or not adoption of additive manufacturing. The applicability of the proposed model was evaluated through interviews with experts. The evaluation of the results indicates that the steps and the activities proposed in the model contribute to assist in the evaluation of the adoption of additive manufacturing in high added value industry.

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