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Girardin, Emmanuelle. "Biomedical metal alloys produced by Direct Metal Laser Sintering." Doctoral thesis, Università Politecnica delle Marche, 2016. http://hdl.handle.net/11566/243150.
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La Sinterizzazione Diretta di Metalli mediante Laser (DMLS), basata su un processo strato-per-strato, è stata usata per ottenere provini in leghe Co–Cr–Mo–W e Ti-6Al-4V per applicazioni biomediche. La risposta meccanica e la microstruttura sono state studiate sia nello stato “tal quale” che dopo trattamento termico post-produzione per i campioni in Co–Cr–Mo–W, e dopo due diversi trattamenti termici per quelli in Ti-6Al-4V. Misure di rugosità e durezza, così come test di trazione e flessione, sono state eseguite per studiare la risposta meccanica, mentre la diffrazione di raggi X, la microscopia elettronica (SEM, TEM, STEM) e la microanalisi (EDX) sono state usate per investigare la microstruttura. Nella lega Ti-6Al-4V è stata studiata anche l’anisotropia.
I risultati nella lega Co–Cr–Mo–W mostrano una rete di lamelle ε-Co (esagonale) nella matrice γ-Co (cubica a face centrate), responsabile della alta resistenza a trazione (UTS) e durezza nello stato “tal quale”. I trattamenti termici aumentano la frazione volumica dell’ε-Co, modificando leggermente la dimensione media della struttura lamellare. In ogni caso, i trattamenti termici danno origine ad un sensibile aumento di UTS e durezza e ad una forte riduzione della duttilità. Quest’ultima è attribuito ad una massiccia precipitazione di fase esagonale Co3(Mo,W)2Si e alla contemporanea formazione di inclusioni ricche in Si.
I campioni di Ti-6Al-4V rivelano una bassa porosità ed alte proprietà meccaniche, in particolare una maggiore elongazione rispetto ai dati di letteratura. Non si evidenzia alcuna anisotropia fre le orientazioni. La microstruttura osservata è molto fine. Si rileva una fase martensitica α’-Ti dopo il primo trattamento di rilassamento degli sforzi, mentre il ciclo termico induce una fase stabile α+β-Ti, con la fase β che cresce al bordo-grano della α.
Questi risultati suggeriscono possibili applicazioni innovative della tecnologia DMLS per la produzione di parti meccaniche in campo medico/odontoiatrico.Direct Metal Laser Sintering (DMLS), based on a layer-by-layer production process, was used to produce specimens in Co–Cr–Mo–W and Ti-6Al-4V alloys, which are utilized in biomedical applications. The mechanical response and microstructure were investigated in the as-sintered state and after post-production thermal treatments for the Co-Cr-Mo-W samples, and after two post-production treatments for the Ti-6Al-4V ones. Roughness and hardness measurements, as well as tensile and flexural tests, were performed to study the mechanical response, while X-ray diffraction (XRD), electron microscopy (SEM, TEM, STEM) and microanalysis (EDX) were used to investigate the microstructure in different conditions. The anisotropy of the Ti-6Al-4V specimens was also investigated. Results on the Co-Cr-Mo-W samples showed an intricate network of ε-Co (hcp) lamellae in the γ-Co (fcc) matrix, responsible of the high UTS and hardness in the as-sintered state. Thermal treatments increase volume fraction of the ε-Co (hcp) martensite but slightly modify the average size of the lamellar structure. Nevertheless, thermal treatments are capable of producing a sensible increase in UTS and hardness and a strong reduction in ductility. These latter effects were mainly attributed to the massive precipitation of an hcp Co3(Mo,W)2Si phase and the contemporary formation of Si-rich inclusions. Ti-6Al-4V specimens reveal extremely low porosity, high mechanical properties, in particular an elongation higher than the literature data. The results do not evidence any anisotropy between the different orientations. The observed microstructure is very fine. A martensitic α’-Ti phase is detected after the first stress relieving treatment, while the firing cycle induces a phase transformation to a stable α+β-Ti phase with the β phase growing at the α grains boundaries. These results suggest possible innovative applications of the DMLS technique to the production of mechanical parts in the medical and dental fields.
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Pozzi, Francesco. "Direct metal laser sintering of steel with high vanadium content." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2017. http://amslaurea.unibo.it/13548/.
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La definizione di "rapid prototyping" è ben nota. Ci si riferisce a quell'insieme di tecnologie utilizzate per la realizzazione di oggetti partendo da modelli geometrici molto complicati, realizzando protitipi direttamente dal disegno CAD 3D. Le tecnologie RP sono state poi sviluppate per l'industria artigianale, nell'obiettivo di accelerare la produzione senza perdita di precisione nella costruzione. Tra queste tecniche sono sorte quelle di selective laser sintering.
La sinterizzazione è il processo termico e meccanico per produrre materiali compattando sostanze in polvere, sotto una certa pressione o temperatura; più precisamente, nella sinterizzazione laser le polveri sono riscaldate per un tempo brevissimo.
La fisica che descrive questo processo è piuttosto articolata, dato che la descrizione parte dall'assorbimento di radiazione laser e che comprenderà conduzione termica nella polvere, trasformazione di fase di un materiale eterogeneo, formazione di fase solida con diversi meccanismi di condensazione e lo sviluppo delle diverse microstrutture dell'acciaio.
Il lavoro sperimentale che è stato svolto è la produzione di una polvere di acciaio e vanadio utilizzabile in solid state sintering, ma dato quanto detto, lo studio ha incluso una descrizione più generale del processo della sinterizzazione metallica da polveri.
Nel corso del lavoro si è contribuito alla messa a punto della stampante 3D per sinterizzazione di polveri metalliche realizzata alla 3d4mec, soffermandosi nella ricerca dei parametri ottimali per la stampa di polvere StainlessSteel CX by EOS.
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Dewidar, Montasser Marasy A. "Direct and indirect laser sintering of metals." Thesis, University of Leeds, 2002. http://etheses.whiterose.ac.uk/3973/.
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Manufacturing functional prototypes and tools using conventional methods usually is a time consuming procedure with multiple steps. The pressure to get products to market faster has resulted in the creation of several Rapid Prototyping (RP) techniques. However, potentially one of the most important areas of Rapid Manufacturing (RM) technology lies in the field of Rapid Tooling (RT). Layer manufacture technologies are gaining increasing attention in the manufacturing sector for the production of polymer mould tooling. Layer manufacture techniques can be used in this potential manufacturing area to produce tooling either indirectly or directly, and powder metal based layer manufacture systems are considered an effective way of producing rapid tooling. Selective Laser Sintering (SLS) is one of available layer manufacture technologies. SLS is a sintering process in which shaped parts are built up layer by layer from bottom to top of powder material. A laser beam scans the powder layer, filling in the outline of each layers CAD-image, and heats the selected powder to fuse it. This work reports the results of an experimental study examining the potential of layer manufacturing processes to deliver production metal tooling for manufacture of polymer components. Characterisation of indirect selective laser sintering and direct selective laser sintering to provide the metal tooling is reported. Three main areas were addressed during the study: mechanical strength, accuracy, and build rate. Overviews of the results from the studies are presented. Two materials (RapidSteel 2.0 and special grade of highspeed steel) and also two generations of SLS machines Sinterstation 2000 and sinterstation research machine, which was constructed in Leeds) were used during this work.
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Říčan, Daniel. "Návrh výroby tělesa plynového analyzátoru s využitím metody Direct Metal Laser Sintering." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2011. http://www.nusl.cz/ntk/nusl-229527.
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This master’s thesis deals with the possibility of manufacturing gas analyzer by Rapid Prototyping Technology and it with the method Direct Metal Laser Sintering. The theoretical part describes the current production of component in the Frentech Aerospace LLC and innovation with the DMSL method in the company Innomia Furthermore JSC. Then an analysis of the principle of single methods Rapid Prototyping, especially the method of Direct Metal Laser Sintering, is implemented. The aim of the experimental part is to compare the mechanical properties and material structures, conventional metallurgy and powder metallurgy. The thesis also contains a technical-economic evaluation comparing the manufacture of mechanical part by conventional and advanced additive technology.
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Chen, Tiebing. "Analysis and modeling of direct selective laser sintering of two-component metal powders." Diss., Columbia, Mo. : University of Missouri-Columbia, 2005. http://hdl.handle.net/10355/5818.
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Thesis (Ph.D.)--University of Missouri-Columbia, 2005.The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file. Title from title screen of research.pdf file viewed on (November 15, 2006) Vita. Includes bibliographical references.
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Xu, Yangzi. "Corrosion Behavior of Direct Metal Laser Sintered Ti-6Al-4V for Orthopedic Applications." Digital WPI, 2017. https://digitalcommons.wpi.edu/etd-dissertations/282.
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Ti-6Al-4V alloy has been used as biomedical implants for decades because of its superior mechanical properties, good biocompatibility, lack of allergic problems and good corrosion resistance. It is widely used as the tibial components in total knee arthroplastry and hip cup in total hip replacement. However, the mechanical properties of Ti-6Al-4V implant can be deteriorated due to corrosion pits. In the past decades, the rapid developments in additive manufacturing have broadened their applications in biomedical area due to the high geometrical freedom in fabricating patient-friendly implants. However, the high-localized thermal input and fast cooling rate during laser processing usually result in non-equilibrium phase with high residual stress. Therefore, it is necessary to apply proper post-treatments on the as-printed parts to ensure better properties. In this work, various post-treatments (e.g. post-heat treatments, hot isostatic pressing) were applied aim to improve the corrosion behavior of direct metal laser sintered Ti-6Al-4V parts. The effect of post-treatment temperature on the mechanical properties and corrosion behavior were examined experimentally. A discussion on factors influencing corrosion rate was presented, and the corrosion mechanism on the Ti-6Al-4V part in simulated body fluid was proposed. Based on the electrochemical measurement results, enhanced corrosion resistance was observed in the samples after high temperature HIPing at the annealing temperature (α+β region) of 799°C.
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Das, Suman. "Direct selective laser sintering of high performance metals : machine design, process development and process control /." Digital version accessible at:, 1998. http://wwwlib.umi.com/cr/utexas/main.
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Coffy, Kevin. "Microstructure and Chemistry Evaluation of Direct Metal Laser Sintered 15-5 PH Stainless Steel." Master's thesis, University of Central Florida, 2014. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/6256.
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15-5PH stainless steel is an important alloy in the aerospace, chemical, and nuclear industries for its high strength and corrosion resistance at high temperature. Thus, this material is a good candidate for processing development in the direct metal laser sintering (DMLS) branch of additive manufacturing. The chemistry and microstructure of this alloy processed via DMLS was compared to its conventionally cast counterpart through various heat treatments as part of a characterization effort. The investigation utilized optical microscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-Ray diffractometry (XRD), energy dispersive X-Ray spectroscopy (EDS) and glow discharge atomic emission spectrometry (GDS) techniques. DMLS processed samples contained a layered microstructure in which the prior austenite grain sizes were relatively smaller than the cast and annealed prior austenite grain size. The largest of the quantifiable DMLS prior austenite grains had an ASTM grain size of approximately 11.5-12 (6.7?m to 5.6?m, respectively) and the cast and annealed prior austenite grain size was approximately 7-7.5 (31.8?m to 26.7?m, respectively), giving insight to the elevated mechanical properties of the DMLS processed alloy. During investigation, significant amounts of retained austenite phase were found in the DMLS processed samples and quantified by XRD analysis. Causes of this phase included high nitrogen content, absorbed during nitrogen gas atomization of the DMLS metal powder and from the DMLS build chamber nitrogen atmosphere. Nitrogen content was quantified by GDS for three samples. DMLS powder produced by nitrogen gas atomization had a nitrogen content of 0.11 wt%. A DMLS processed sample contained 0.08 wt% nitrogen, and a conventionally cast and annealed sample contained only 0.019 wt% nitrogen. In iron based alloys, nitrogen is a significant austenite promoter and reduced the martensite start and finish temperatures, rendering the standard heat treatments for the alloy ineffective in producing full transformation to martensite. Process improvements are proposed along with suggested future research.M.S.M.E.
Masters
Materials Science Engineering
Engineering and Computer Science
Materials Science and Engineering
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De, Beer N., and A. I. Odendaal. "The geometrical accuracy of a custom artificial intervertebral disc implant manufactured using Computed Tomography and Direct Metal Laser Sintering." Journal for New Generation Sciences, Vol 10, Issue 3: Central University of Technology, Free State, Bloemfontein, 2012. http://hdl.handle.net/11462/613.
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Published ArticleRapid Manufacturing (RM) has emerged over the past few years as a potential technology to successfully produce patient-specific implants for maxilla/facial and cranial reconstructive surgeries. However, in the area of spinal implants, customization has not yet come to the forefront and with growing capabilities in both software and manufacturing technologies, these opportunities need to be investigated and developed wherever possible. The possibility of using Computed Tomography (CT) and Rapid Manufacturing (RM) technologies to design and manufacture a customized, patient-specific intervertebral implant, is investigated. Customized implants could aid in the efforts to reduce the risk of implant subsidence, which is a concern with existing standard implants. This article investigates how accurately the geometry of a customized artificial intervertebral disc (CAID) can represent the inverse geometry of a patient's vertebral endplates. The results indicate that the endplates of a customized disc implant can be manufactured to a calculated average error of 0.01mm within a confidence interval of 0.022mm, with 95% confidence, when using Direct Metal Laser Sintering.
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Verma, Anoop P. "Minimizing Build Time and Surface Inaccuracy of Direct Metal Laser Sintered Parts: An Artificial Intelligence Based Optimization Approach." University of Cincinnati / OhioLINK, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1249840383.
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Sekerka, Vít. "Výroba dílů technologií DMLS a jejich porovnání s jinými konvenčními technologiemi z hlediska ekonomické náročnosti." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2011. http://www.nusl.cz/ntk/nusl-229969.
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This diploma thesis presents a technology based on the gradual smelting of fine layers of metal powder by using a laser beam. It explains and describes basic terminology related to the Rapid Prototyping technology, its division and practical usage. A part of the thesis is also the fabrication of several prototype parts by Direct Metal Laser Sintering including the economical comparison of their fabrication with other conventional technologies.
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Hussein, Ahmed Yussuf. "The development of lightweight cellular structures for metal additive manufacturing." Thesis, University of Exeter, 2013. http://hdl.handle.net/10871/15023.
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Metal Additive Manufacturing (AM) technologies in particular powder bed fusion processes such as Selective Laser Melting (SLM) and Direct Metal Laser Sintering (DMLS) are capable of producing a fully-dense metal components directly from computer-aided design (CAD) model without the need of tooling. This unique capability offered by metal AM has allowed the manufacture of inter-connected lattice structures from metallic materials for different applications including, medical implants and aerospace lightweight components. Despite the many promising design freedoms, metal AM still faces some major technical and design barriers in building complex structures with overhang geometries. Any overhang geometry which exceeds the minimum allowable build angle must be supported. The function of support structure is to prevent the newly melted layer from curling due to thermal stresses by anchoring it in place. External support structures are usually removed from the part after the build; however, internal support structures are difficult or impossible to remove. These limitations are in contrast to what is perceived by designers as metal AM being able to generate all conceivable geometries. Because support structures consume expensive raw materials, use a considerable amount of laser consolidation energy, there is considerable interest in design optimisation of support structure to minimize the build time, energy, and material consumption. Similarly there is growing demand of developing more advanced and lightweight cellular structures which are self-supporting and manufacturable in wider range of cell sizes and volume fractions using metal AM. The main focuses of this research is to tackle the process limitation in metal AM and promote design freedom through advanced self-supporting and low-density Triply Periodic Minimal Surface (TPMS) cellular structures. Low density uniform, and graded, cellular structures have been developed for metal AM processes. This work presents comprehensive experimental test conducted in SLM and DMLS processes using different TPMS cell topologies and materials. This research has contributed to new knowledge in understanding the manufacturability and mechanical behaviour of TPMS cellular structures with varying cell sizes, orientations and volume fractions. The new support structure method will address the saving of material (via low volume cellular structures and easy removal of powder) and saving of energy (via reduced build-time).
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Roque, Lidiane Kümpel [UNESP]. "Influência dos tratamentos térmicos na microestrutura e nos micromecanismos de fratura da liga ti-6al-4v produzida por sinterização direta de metal por laser (DMLS)." Universidade Estadual Paulista (UNESP), 2015. http://hdl.handle.net/11449/136111.
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000859657.pdf: 11263749 bytes, checksum: 51e907f4fbdf0d8ce56785c1c9af062c (MD5)A liga Ti-6A-4V é um biomaterial que tem se mostrado muito adequado na fabricação de implantes para reparar lesões craniofaciais. Entre outros requisitos, é importante que o implante resista a solicitação mecânica para garantir uma resposta clínica satisfatória de modo a proporcionar conforto e segurança ao paciente. O propósito específico do presente trabalho de pesquisa é determinar a influência de diferentes ciclos térmicos na microestrutura da amostra da Ti-6Al-4V produzida pelo processo de sinterização direta de metal por laser (DMLS) e no micromecanismo de fratura resultante de tensionamento uniaxial em tração. Para isso foram fabricados corpos-de-prova de tração, utilizando a técnica DMLS, e os mesmos foram submetidos a diferentes ciclos térmicos de 650 °C/1h, 650 °C/3h, 800 °C/4h e 850 °C/2h. Posteriormente, os corpos-de-prova foram submetidos a ensaios de tração. A caracterização microestrutural foi realizada com auxílio de microscopia óptica (MO) e eletrônica de varredura (MEV). As superfícies de fratura resultantes para as diferentes condições de ciclos térmicos foram analisadas por microscopia eletrônica de varredura. A microestrutura final da amostra como produzida resultante do processo de manufatura aditiva por DMLS revelou uma microestrutura martensita hexagonal α'. Para a amostra A6501H, a microestrutura martensítica resultante do processo DMLS não se decompôs. Na amostra A6503H a microestrutura martensítica começa a se decompor, pois são observados precipitados da fase β. Já nas amostras A8004H e A8502H observa-se uma estrutura (α +β), com cristais de fase α e fase β precipitada nos contornos. De acordo com a análise fractográfica todas as condições estudadas apresentaram fratura dúctil caracterizada pela formação e coalescência de microcavidades com forma e tamanhos variados
The Ti-6A-4V alloy is a biomaterial that has proved very suitable for the manufacture of prostheses to repair craniofacial injuries. Among other requirements, it is important that the prosthesis resist mechanical stress to ensure a satisfactory clinical response in order to provide comfort and safety to patients. The specific purpose of this research is to determine the influence of thermal cycles - as prototyped, 650 °C (1h); 650 °C (3h), 800 °C (2h) and 850 °C (4h) - on the microstructure and fracture micromechanisms resulting from uniaxial tension in traction. Therefore it was manufactured by DMLS technique bodies - of - proof traction which were subsequently subjected to different thermal cycles. Then, the bodies -specimens were subjected to tensile test. Microstructural characterization was carried out using optical and scanning electron microscopy (SEM). The resulting fracture surfaces of the five conditions for thermal cycling were analyzed by SEM. The final sample microstructure produced as a result of the additive manufacturing process DMLS revealed a hexagonal martensitic microstructure α '. For A6501H sample, the resulting martensitic microstructure DMLS process is not decomposed. In A6503H martensitic microstructure sample begins to decompose, as are observed precipitates of β phase. Already in the samples A8004H and A8502H observe a structure (α + β) with α and β phase crystal phase precipitated in the contours. According to fractographic analysis of all studied showed ductile fracture conditions characterized by the formation and coalescence wells with varying shape and sizes
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Roque, Lidiane Kümpel. "Influência dos tratamentos térmicos na microestrutura e nos micromecanismos de fratura da liga ti-6al-4v produzida por sinterização direta de metal por laser (DMLS) /." Ilha Solteira, 2015. http://hdl.handle.net/11449/136111.
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Orientador: Ruís Camargo TokimatsuCo-orientador: Maria Aparecida Larosa
Banca: Vicente Afonso Ventrella
Banca: Cecília Amelia de Carvalho Zavaglia
Resumo: A liga Ti-6A-4V é um biomaterial que tem se mostrado muito adequado na fabricação de implantes para reparar lesões craniofaciais. Entre outros requisitos, é importante que o implante resista a solicitação mecânica para garantir uma resposta clínica satisfatória de modo a proporcionar conforto e segurança ao paciente. O propósito específico do presente trabalho de pesquisa é determinar a influência de diferentes ciclos térmicos na microestrutura da amostra da Ti-6Al-4V produzida pelo processo de sinterização direta de metal por laser (DMLS) e no micromecanismo de fratura resultante de tensionamento uniaxial em tração. Para isso foram fabricados corpos-de-prova de tração, utilizando a técnica DMLS, e os mesmos foram submetidos a diferentes ciclos térmicos de 650 °C/1h, 650 °C/3h, 800 °C/4h e 850 °C/2h. Posteriormente, os corpos-de-prova foram submetidos a ensaios de tração. A caracterização microestrutural foi realizada com auxílio de microscopia óptica (MO) e eletrônica de varredura (MEV). As superfícies de fratura resultantes para as diferentes condições de ciclos térmicos foram analisadas por microscopia eletrônica de varredura. A microestrutura final da amostra como produzida resultante do processo de manufatura aditiva por DMLS revelou uma microestrutura martensita hexagonal α'. Para a amostra A6501H, a microestrutura martensítica resultante do processo DMLS não se decompôs. Na amostra A6503H a microestrutura martensítica começa a se decompor, pois são observados precipitados da fase β. Já nas amostras A8004H e A8502H observa-se uma estrutura (α +β), com cristais de fase α e fase β precipitada nos contornos. De acordo com a análise fractográfica todas as condições estudadas apresentaram fratura dúctil caracterizada pela formação e coalescência de microcavidades com forma e tamanhos variados
Abstract: The Ti-6A-4V alloy is a biomaterial that has proved very suitable for the manufacture of prostheses to repair craniofacial injuries. Among other requirements, it is important that the prosthesis resist mechanical stress to ensure a satisfactory clinical response in order to provide comfort and safety to patients. The specific purpose of this research is to determine the influence of thermal cycles - as prototyped, 650 °C (1h); 650 °C (3h), 800 °C (2h) and 850 °C (4h) - on the microstructure and fracture micromechanisms resulting from uniaxial tension in traction. Therefore it was manufactured by DMLS technique bodies - of - proof traction which were subsequently subjected to different thermal cycles. Then, the bodies -specimens were subjected to tensile test. Microstructural characterization was carried out using optical and scanning electron microscopy (SEM). The resulting fracture surfaces of the five conditions for thermal cycling were analyzed by SEM. The final sample microstructure produced as a result of the additive manufacturing process DMLS revealed a hexagonal martensitic microstructure α '. For A6501H sample, the resulting martensitic microstructure DMLS process is not decomposed. In A6503H martensitic microstructure sample begins to decompose, as are observed precipitates of β phase. Already in the samples A8004H and A8502H observe a structure (α + β) with α and β phase crystal phase precipitated in the contours. According to fractographic analysis of all studied showed ductile fracture conditions characterized by the formation and coalescence wells with varying shape and sizes
Mestre
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Haverkos, Stephen M. "FRICTIONAL PROPERTIES OF NOVEL BRACKET SYSTEMS: AN IN-VITRO STUDY." VCU Scholars Compass, 2019. https://scholarscompass.vcu.edu/etd/5770.
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Orthodontic brackets undergo resistance during sliding that includes classical friction, binding, and notching. Current bracket systems are hampered by these challenging forces. As a result, the clinician usually needs to apply additional forces to overcome the resistance which increases the risk of root resorption and discomfort for the patient. This study evaluated frictional properties of a novel bracket that had polytetrafluoroethylene (Teflon™) coated rollers in its design. Five types of brackets (n = 10, each), including a passive self-ligating bracket, a traditional ligated bracket, a three-dimensionally printed direct metal laser sintering (DMLS) bracket with and without Teflon™ rollers, and computer numeric controlled (CNC) machine milled bracket with Teflon™ rollers were tested. The peak resistance values were assessed at 0°, 4°, and 8° of tip on a 0.019 x 0.025” arch wire. At 8° of tip, the DMLS and the CNC milled bracket systems, both with Teflon™ rollers, exhibited less friction as compared to the other brackets tested (p
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Ranjan, Rajit. "Design for Manufacturing and Topology Optimization in Additive Manufacturing." University of Cincinnati / OhioLINK, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1439307951.
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Shukitis, Amber Nicole. "A Recreation and Ballistic Evaluation of Otto Schneeloch's Firearm Curiosity - The .307 Triangular." Scholar Commons, 2014. https://scholarcommons.usf.edu/etd/5125.
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Otto Scheeloch's U.S. Patent No. 134,442 of 1872 describes a unique firearm that uses triangular bullets. The current research effort evaluates the ballistic performance of Otto's disclosure for the very first time. To achieve this goal it was necessary to seek out surviving artifacts and scour the historical record in search of all the parameters needed to meticulously recreate the curious triangular cartridges and the corresponding gun barrel, with its matching twisted triangular bore. Every aspect of the resulting reproduction ammunition was made to be as authentic as possible, including the use of vintage civil war era bullet lead, bullet grease of period recipe, and the correct type of black powder propellant. 3D CAD (SolidWorksTM) was employed in designing the components, while advanced rapid prototyping (FDM & DMLS) techniques and investment casting were used in the physical construction of the ammunition and barrel. The ballistics testing was performed from a shooting rest over a range of 10-feet. Data was obtained for five rounds using a chronograph, paper targets and ballistic gel. The triangular bullets proved to be surprisingly accurate, consistent, and stable in flight. Data was recorded for sectional density, ballistic coefficient, muzzle velocity and energy, group size and penetration.
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Ghirardi, Lorenzo. "Comportamento a fatica di provini in acciaio inossidabile realizzati tramite DMLS con diverse direzioni di accrescimento." Bachelor's thesis, Alma Mater Studiorum - Università di Bologna, 2016. http://amslaurea.unibo.it/10665/.
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Si tratta di una tesi svolta su diverse tipologie di provini ottenuti per Direct Metal Laser Sintering. Questi campioni sono stati provati a fatica, precisamente a flessione rotante. Per determinarne il limite di fatica è stato utilizzato il metodo Dixon. Una volta stimato questo valore sono stati svolti degli attacchi chimici per verificare la presenza di cricche e porosità. Infine, per controllare le caratteristiche descritte inizialmente dalla letteratura del materiale, sono stati sottoposti ad una prova di durezza Rockwell.
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Olakanmi, Eyitayo Olatunde. "Direct selective laser sintering of aluminium alloy powders." Thesis, University of Leeds, 2008. http://etheses.whiterose.ac.uk/1476/.
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The SLS/SLM of aluminium powder had been investigated by studying the effect of powder properties and laser processing parameters on the microstructures and properties of both single layer and multiple layer builds. On the basis of experimental evidence, the SLS/SLM of aluminium powders could be categorised into full melting (SLM) which was found to have occurred in both pure and pre-alloyed aluminium powders, and binary liquid phase sintering (SLS) which occurred in blended bimodal or trimodal powders. That successful disruption of the oxide film is possible is a significant result, as is the constitutional effect on this. The spheroidisation and oxide disruption phenomena in SLS/SLM processed aluminium powders arc suggested to be mainly controlled by the amount of oxide on the as-received powder's surface, the degree of the uniformity of the distribution of the surface oxide film covering the aluminium particles as well as the nature of thermal mismatch existing between the oxide film and the parent aluminium particle which was dependent on the phase present in the oxide film (alumina, mullite, and spinel). It was discovered that the attainment of high sintered density and desirable microstructural properties in the blended aluminium powders is consequent upon the determination of the right processing conditions, appropriate choice of powders (in terms of particle size distribution, spherical particle shape, and component ratio). Moreover, it is now evident that chemical constitution of the blended aluminium powders only becomes influential in the determination of the properties of SLS processed parts when the choice of processing parameters and powder properties are correct. The choice of powder properties determines the thermal conductivity of the powder bed which in effect controls the sintered properties. This had been inferred from the relationship between powder tapping density on one hand, and selective laser sintered (SLS) density, dendrite spacing and fraction of primary phase on the other hand. In making smaller samples, it has been shown that the attainment of high sintered density (up to 90%) and a good microstructure are feasible. These arc accompanied by reasonable hardness values, comparable to those of cast Al-12wt%Si castings. In fabricating larger sized parts for mechanical testing, defects such as delamination became more noticeable leading to poor mechanical properties in those samples. Thus, it is now clear that physical limitations of the sintering machine hinder the production of SLS/SLM processed parts having excellent structural integrity. On the basis of this work, it is envisaged that the use of pre-alloyed Al-Si powders of uniform composition, but a wider particle size and size distribution, blended to optimise the bed density, offers the potential to produce light alloy components by SLS. In conclusion, the specific laser energy input, the component ratio, and the particle size and size distribution of the powder were found to have strongly influenced the densitication mechanism and the solidification process in a small sized aluminium powdered part fabricatedb y SLS/SLM process.
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Amin, Zulkifli. "Metal-electroceramic bonding through selective laser sintering." Thesis, University of Leeds, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.418768.
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Eane, Radu Bogdan. "Metal powder effects on selective laser sintering." Thesis, University of Leeds, 2002. http://etheses.whiterose.ac.uk/4016/.
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Manufacturing functional prototypes and different tools using conventional methods usually is a time consuming process with multiple steps. The global economic pressure to get products to market faster has resulted in the development of several Rapid Prototyping (RP) techniques. Layer manufacturing technologies are gaining increasing attention in the manufacturing sector. They have the potential to produce tooling either indirectly or directly, and powder metal based layer manufacture systems are considered to be an effective way of producing rapid tooling. Selective Laser Sintering (SLS) is one of several available layer manufacture technologies. SLS is a sintering process in which designed parts are built up layer by layer from the bottom up using different powder materials. A laser beam scans the powder bed, filling in the outline of each layer’s CAD-image by heating the selected powder pattern to fuse it. This work reports on the results of an experimental study examining the potential of the selective laser sintering process to produce metallic parts using stainless steel powder. One material, a stainless steel powder and one sintering station research machine, which was constructed in Leeds, were used during the research. A step-by-step investigation was conducted. The research started with sintered tracks and finished with multiple layer sintering. The purpose was to find successful conditions and to establish the main problems that need to be overcome. The main achievements of this thesis have been to develop laser power and scan speed sintering maps for a stainless steel powder. 1 he maps have established conditions in which multiple layer blocks can be created, have established strategies to enable large areas to be sintered without warping and show that powder particle size has an important influence on sintering and on the position of the boundaries in the sintering maps. Although this investigation answered some questions, it also raised several more which are presented at the end of this thesis for future work.
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Vandi, Daniele. "Studio del comportamento a fatica di provini in Maraging steel realizzati tramite Additive Manufacturing." Bachelor's thesis, Alma Mater Studiorum - Università di Bologna, 2019.
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Nel presente lavoro di tesi verrà studiato ed analizzato, tramite prove effettuate in laboratorio, il comportamento a fatica di 3 set di provini metallici in Maraging steel, realizzati mediante le più moderne tecnologie di Additive Manufacturing.
Tale recente tecnologia, pioniera nell'ambito della produzione manifatturiera di prototipi e pezzi, ha iniziato sin dagli inizi del suo sviluppo a mostrare le sue numerose potenzialità, e solo negli ultimi anni ha dimostrato di poter essere applicata con successo anche a componenti meccanici e parti funzionali. Ciononostante, data la modernità della tecnologia, sono richieste ulteriori ricerche ed analisi per determinare il comportamento meccanico di pezzi prodotti con tali tecnologie, in quanto la loro resistenza, statica e soprattutto a fatica, è influenzata dalla peculiarità del processo tecnologico stesso, che tende a generare forte anisotropia nelle leghe metalliche prodotte.
Nella prima parte verranno discussi i fondamenti generali della meccanica per i materiali metallici, in particolare il comportamento dei materiali sottoposti a storie di carico variabile; nella seconda parte verrà presentato uno stato dell'arte dei vari processi di Additive Manufacturing; nella terza parte, verrà studiato il comportamento a fatica, ad alto numero di cicli, dei suddetti provini sottoposti da un macchinario a flessione rotante a vari livelli di carico; nella quarta parte, tramite uso di tecniche statistiche, verrà presentata un'elaborazione dei risultati ottenuti in laboratorio, in particolare per ricavare la curva S-N e il limite di fatica del materiale; infine verrà presentata l'osservazione al microscopio delle superfici di frattura dei provini, per indagare la propagazione della rottura e così risalire alle possibili cause iniziatrici della rottura stessa.
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Asar, Munevver Elif. "Investigating Turbine Vane Trailing Edge Pin Fin Cooling in Subsonic and Transonic Cascades." The Ohio State University, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=osu155551385206548.
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Cruz, Fernando Manuel Martins. "Direct manufacture of hydroxyapatite based bone implants using selective laser sintering." Thesis, Bucks New University, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.408253.
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Taylor, Christopher Martin. "Direct laser sintering of stainless steel : thermal experiments and numerical modelling." Thesis, University of Leeds, 2004. http://etheses.whiterose.ac.uk/378/.
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SLS is a commercial solid freeform fabrication process. Layers of powder material are bonded by a laser beam to rapidly manufacture three dimensional freeform models. In this work, the direct SLS of room temperature single-phase steel powder beds is researched. Two approaches are adopted: - Experimental analysis of heat transfer in the process; - Numerical modelling of the process. Experimental work involves the use of analytical equations to calculate the thermal conductivity and laser energy absorptance of the SLS powder bed. Experiments take place in a range of representative situations. Two temperature measurement systems are used, requiring some custom-designed elements. Conductivity values in the range 0.07 to 0.25 W/(m. K) are found, dependent on atmospheric gas and powder particle size. Absorptance varies from 0.08 to 0.21, dependent on atmosphere and material type. Measurements are made to learn more about temperature variation in the bed with position and time. It is found that processed material melts and solidifies in under 4 seconds in studied cases. Numerical modelling involves developing and testing an existing Fortran model of the SLS process. A method is devised to visualise modelled parts in 3D. Preprocessing is simplified, and more status information is communicated during execution. The effect on modelled parts of changes made to the program are tested. The stability of part depth is improved. The nature of parts is categorised against input parameters. The area, relative density and morphology of manufactured and modelled single layer parts are compared. Manufactured scans are found to have a variable cross-sectional shape, whereas the cross-sectional shape of modelled scans does not change. Modelled parts are found to be significantly smaller than manufactured parts. Reasons for these two differences are suggested.
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Xiao, Bin. "Modeling of selective laser sintering of single-component metal powders." Diss., Columbia, Mo. : University of Missouri-Columbia, 2006. http://hdl.handle.net/10355/5859.
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Thesis (Ph. D.)--University of Missouri-Columbia, 2006.The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file. Title from title screen of research.pdf file (viewed on August 10, 2007) Vita. Includes bibliographical references.
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Pereira, M. F. V. T., M. Williams, and R. Bruwer. "Rapid die manufacturing using direct laser metal deposition." Journal for New Generation Sciences, Vol 7, Issue 3: Central University of Technology, Free State, Bloemfontein, 2009. http://hdl.handle.net/11462/542.
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Published ArticleGlobal issues such as energy and climate changes have impacted on both the automotive and aerospace industries, forcing them to adopt measures to produce products that consume fewer combustibles and emit less carbon dioxide. Making vehicles lighter is one of the logical ways of reducing fuel consumption. The need for light components, able to fulfil technical and quality specifications, led to market growth for tooling that is able to mass produce parts using manufacturing processes such as high pressure die casting. Competitive pressures to reduce the lead time required for tooling-up has also increased dramatically. For this reason research into various methods, techniques and approaches to tool manufacture is being undertaken globally. This paper highlights the work undertaken at the CSIR on the issue of rapid die manufacturing through the application and evaluation of a rapid prototyping technique and coating technologies applied to die components of a high pressure casting die for the production of aluminium components. Criteria for determining suitability were developed against which the technique was evaluated that included time, cost and life-expectancy. Results of accelerated testing procedures to evaluate the die material produced by the rapid prototyping technique and surface coatings and treatments of die materials for their resistance to washout, erosion, heat checking and corrosion in a high pressure die casting environment, are presented. The outcomes of this research will be used for further development and application of specific techniques, design principles and criteria for this approach.
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Onyeako, Isidore. "Resolution-aware Slicing of CAD Data for 3D Printing." Thesis, Université d'Ottawa / University of Ottawa, 2016. http://hdl.handle.net/10393/34303.
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3D printing applications have achieved increased success as an additive manufacturing (AM) process. Micro-structure of mechanical/biological materials present design challenges owing to the resolution of 3D printers and material properties/composition. Biological materials are complex in structure and composition. Efforts have been made by 3D printer manufacturers to provide materials with varying physical, mechanical and chemical properties, to handle simple to complex applications. As 3D printing is finding more medical applications, we expect future uses in areas such as hip replacement - where smoothness of the femoral head is important to reduce friction that can cause a lot of pain to a patient. The issue of print resolution plays a vital role due to staircase effect. In some practical applications where 3D printing is intended to produce replacement parts with joints with movable parts, low resolution printing results in fused joints when the joint clearance is intended to be very small. Various 3D printers are capable of print resolutions of up to 600dpi (dots per inch) as quoted in their datasheets. Although the above quoted level of detail can satisfy the micro-structure needs of a large set of biological/mechanical models under investigation, it is important to include the ability of a 3D slicing application to check that the printer can properly produce the feature with the smallest detail in a model. A way to perform this check would be the physical measurement of printed parts and comparison to expected results. Our work includes a method for using ray casting to detect features in the 3D CAD models whose sizes are below the minimum allowed by the printer resolution. The resolution validation method is tested using a few simple and complex 3D models. Our proposed method serves two purposes: (a) to assist CAD model designers in developing models whose printability is assured. This is achieved by warning or preventing the designer when they are about to perform shape operations that will lead to regions/features with sizes lower than that of the printer resolution; (b) to validate slicing outputs before generation of G-Codes to identify regions/features with sizes lower than the printer resolution.
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McCarthy, David Lee. "Creating Complex Hollow Metal Geometries Using Additive Manufacturing and Metal Plating." Thesis, Virginia Tech, 2012. http://hdl.handle.net/10919/43530.
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Additive manufacturing introduces a new design paradigm that allows the fabrication of geometrically complex parts that cannot be produced by traditional manufacturing and assembly methods. Using a cellular heat exchanger as a motivational example, this thesis investigates the creation of a hybrid manufacturing approach that combines selective laser sintering with an electroforming process to produce complex, hollow, metal geometries. The developed process uses electroless nickel plating on laser sintered parts that then undergo a flash burnout procedure to remove the polymer, leaving a complex, hollow, metal part. The resulting geometries cannot be produced directly with other additive manufacturing systems.
Copper electroplating and electroless nickel plating are investigated as metal coating methods. Several parametric parts are tested while developing a manufacturing process. Copper electroplating is determined to be too dependent on the geometry of the part, with large changes in plate thickness between the exterior and interior of the tested parts. Even in relatively basic cellular structures, electroplating does not plate the interior of the part. Two phases of electroless nickel plating combined with a flash burnout procedure produce the desired geometry. The tested part has a density of 3.16g/cm3 and withstands pressures up to 25MPa. The cellular part produced has a nickel plate thickness of 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
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Pogson, Simon Richard. "Fabrication of functionally graded structures by direct metal laser remelting." Thesis, University of Liverpool, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.494170.
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Investigations have been conducted into the production of Functionally Graded Structures (FGS) with varying composition and porosity using Direct Metal Laser Remelting (DMLR), a Rapid Prototyping (RP) technology. Following a series of experiments on a number of metal systems and analyses conducted using a series of metallographic and spectrographic techniques (SEM-EDS, XRD), it has been possible to assess the viability of a processing system to produce tailored structures.
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Shah, Kamran. "Laser direct metal deposition of dissimilar and functionally graded alloys." Thesis, University of Manchester, 2011. https://www.research.manchester.ac.uk/portal/en/theses/laser-direct-metal-deposition-of-dissimilar-and-functionally-graded-alloys(baa5f8fd-cead-4047-afbf-860844b501d8).html.
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The challenges in the deposition of dissimilar materials are mainly related to the large differences in the physical and chemical properties of the deposited and substrate materials. These differences readily cause residual stresses and intermetallic phases. This has led to the development of functionally graded materials which exhibit spatial variation in composition. Laser direct metal deposition due to its flexibility, it offers wide variety of dissimilar and functionally graded materials deposition. Despite considerable advances in process optimization, there is a rather limited understanding of the role of metallurgical factors in the laser deposition of dissimilar and functionally graded alloys. The aim of this work is to understand and explain mechanisms occurring in diode laser deposition of dissimilar materials and functionally graded materials. The first part of this work addressed diode laser deposition of Inconel 718 nickel alloy to Ti-6Al-4V titanium alloy. Here, the effect of laser pulse parameters and powder mass flow rates on the stress formation and cracking has evaluated by experiment and numerical techniques. Results showed that the clad thickness was an important factor affecting the cracking behaviour. In the second part of this study, an image analysis technique has been developed to measure the surface disturbance and the melt pool cross section size during laser direct metal deposition of Inconel 718 on a Ti-6Al-4V thin wall. It was noted that under tested conditions the overall melt pool area increased with the increase in powder flow rate; the powder carrier gas flow rates also seemed to play important roles in determining the melt pool size. In the third part of this study, a parametric study on the development of Inconel 718 and Stainless steel 316L continuously graded structure has been carried out. Results suggested that microstructure and other mechanical properties can be selectively controlled across the deposited wall. The results presented in this dissertation can be used as a metallurgical basis for further development of dissimilar and functionally graded manufacturing using LDMD technique, guiding future manufacturing engineers to produce structurally sound and microstructurally desirable laser deposited samples.
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Wohlert, Martin Steven. "Hot isostatic pressing of direct selective laser sintered metal components /." Digital version accessible at:, 2000. http://wwwlib.umi.com/cr/utexas/main.
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Zekovic, Srdja. "Numerical simulation and experimental investigation of laser-based direct metal deposition." Ann Arbor, Mich. : ProQuest, 2006. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:3207912.
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Thesis (Ph.D. in Mechanical Engineering)--S.M.U.Title from PDF title page (viewed July 20, 2007). Source: Dissertation Abstracts International, Volume: 67-02, Section: B, page: 1125. Adviser: Radovan Kovasevic. Includes bibliographical references.
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Syed, Waheed Ul Haq. "Combined wire and powder deposition for laser direct metal additive manufacturing." Thesis, University of Manchester, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.556499.
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Bradford-Vialva, Robyn L. "Development of a Metal-Metal Powder Formulations Approach for Direct Metal Laser Melting of High-Strength Aluminum Alloys." University of Dayton / OhioLINK, 2021. http://rave.ohiolink.edu/etdc/view?acc_num=dayton1620259752540201.
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Hussein, Nur Izan Syahriah. "Direct metal deposition of Waspaloy wire using laser and arc heat sources." Thesis, University of Nottingham, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.523507.
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Yadroitsau, Ihar. "Direct manufacturing of 3D objects by selective laser melting of metal powders." Saint-Etienne, 2008. http://www.theses.fr/2008STET4006.
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The accomplished doctoral study concerns the interaction of the powerful laser radiation with powder metallic materials. The problem is of a great scientific interest, since it is a multi-disciplinary subject integrating powder metallurgy, thermo-physics, radiation and heat tranfer, phase transformations. Along with this, the subject has a considerable practical interest because Laser-assisted Direct Manufacturing based on Selective Laser Melting (SLM) is an emerging technology for manufacturing 3D functional objects with great added value, and also complex customized parts. Systematic study is accomplished for the powder materials currently employed in laser-assisted direct manufacturing : stainless steel 316L (-25 µm), tool steel H13 (-25 µm), Inconel 718 (-25 µm), CuNi10 (-25 µm), titanium grade 2 (-25 µm) and NiTi (-45 µm) ; stainless steel 904L (-16 µm et -7 µm), Inconel 625 (-16 µm), Co212F (CoCr, -31 µm). The above mentioned powders were employed in the experimental study for fabrication of 2D planar objects, 3D models and functional components. Comprehensive experimental research on laser-matter interaction are carried out for interaction of a powerful (0. 3-1. 3x106 W/cm²) moving laser beam with a complex system « metallic powder on solid metallic substrate ». Manufacturing strategies allowing 100% density on the fabricated objects are found. Optimal parameters for stable SLM process are determinedL'objectif principal de la thèse de doctorat présentée dans ce mémoire est l'étude de l'interaction d'un faisceau laser de puissance avec des poudres métalliques. Le sujet est d'un grand intérêt scientifique par sa multidisciplinarité intégrant la métallurgie de poudres, la physique thermique, le transfert de chaleur et radiatif, la transformation de phases. En même temps, le sujet a une signification pratique considérable car la Fabrication Directe par fusion laser sélective des poudres (SLM) est une technologie émergente de fabrication d'objets 3D avec une grande valeur ajoutée et de pièces fonctionnelles complexes sur mesure. Une étude systématique a été réalisée sur les poudres actuellement utilisées dans la Fabrication Directe assistée par laser : Inox 316L (-25 µm), acier d'outillage H13 (-25 µm), Inconel 718 (-25 µm), CuNi10 (-25 µm), Ti grade 2 (-25 µm) et NiTi (-45 µm) ; Inox 904L (-16 µm et -7 µm), Inconel 625 (-16 µm), Co212F (CoCr, -31 µm). A partir de ces poudres, des objets plats 2D, des modèles 3D et des pièces fonctionnelles ont été fabriqués. Des recherches expérimentales approfondies sur l'interaction laser/matière sont effectuées, plus particulièrement sur l'interaction d'un faisceau laser de haute puissance mobile (0. 3-1. 3x106 W/cm²) avec un système complexe de poudres métalliques sur substrat métallique solide. Les stratégies de fabrication permettant d'obtenir la densité 100% de pièces résultantes sont identifiées. Les paramètres optimaux pour assurer la stabilité du procédé SLM sont définis
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Pinkerton, Andrew J. "A mathematical and experimental investigation of thin wall Laser Direct Metal Deposition." Thesis, University of Manchester, 2004. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.488244.
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Booysen, G., M. Truscott, D. Mosimanyane, and Beer D. De. "Combining additive fabrication and conventional machining technologies to develop a hybrid tooling approach." Interim : Interdisciplinary Journal, Vol 8, Issue 2: Central University of Technology Free State Bloemfontein, 2009. http://hdl.handle.net/11462/367.
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Published ArticleSouth Africa is constantly loosing contracts for the manufacturing of innovative projects to the East, due to its non-competitive mould-making industry. The paper will report on progress made in a specific focus area in mould-making, namely Hybrid Moulds for injection moulding. Hybrid Moulds refers to a hybrid between Additive Fabrication and conventional methods through the use of amongst others, Direct Metal Laser Sintering techniques, combined with conventional CNC machining (High Speed) techniques. Although the emphasis is on an economically viable process for limited production runs, once the moulds have been developed, it normally is pushed to its limits to realize production quantities. One of the competitive edges is the cutting of lead-times, which obviously impacts on production costs. Another aspect is the ability to manufacture short runs of injection moulded parts in the required engineering material Realising that Laser Sintering of metals is an expensive manufacturing process, a concurrent manufacturing process was developed. Intricate mould details, which normally are time-consuming to manufacture through EDM processes, were grown as inserts, while the less-complex parts of the mould is machined in Aluminium through 3 and 5 Axis High Speed CNC Machining. Using a 3-axis CNC wire cutter, pockets will be created where the more complex Laser Sintered Metal inserts will be fitted. One of the competitive edges is the cutting of lead-times, which obviously impacts on production costs. Another aspect is the ability to manufacture short runs of injection moulded parts in the required engineering material.
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Tal, Amir. "THREE-DIMENSIONAL MICRON-SCALE METAL PHOTONIC CRYSTALS VIA MULTI-PHOTON DIRECT LASER WRITING AND ELECTROLESS METAL DEPOSITION." Master's thesis, University of Central Florida, 2007. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/3889.
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Three-dimensional (3D) metal photonic crystals (MPCs) can exhibit interesting electromagnetic properties such as ultra-wide photonic or "plasmonic" band gaps, selectively tailored thermal emission, extrinsically modified absorption, and negative refractive index. Yet, optical-wavelength 3D MPCs remain relatively unexplored due to the challenges posed by their fabrication. This work explores the use of multi-photon direct laser writing (DLW) coupled with electroless metallization as a means for preparing MPCs. Multi-photon DLW was used to prepare polymeric photonic crystal (PC) templates having a targeted micron-scale structure and form. MPCs were then created by metallizing the polymeric PCs via wet-chemical electroless deposition. The electromagnetic properties of the polymeric PCs and the metallized structures were characterized using Fourier transform infrared spectroscopy. It is shown that metallization transforms the optical properties of the structures from those of conventional 3D dielectric PCs to those consistent with 3D MPCs that exhibit ultra-wide photonic band gaps. These data demonstrate that multi-photon DLW followed by electroless deposition provides a viable and highly flexible route to MPCs, opening a new path to metal photonic materials and devices.M.S.
Optics and Photonics
Optics and Photonics
Optics MS
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Yarrapareddy, Eswar. "Development of slurry erosion resistant materials by laser-based direct metal deposition process." Ann Arbor, Mich. : ProQuest, 2007. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:3258777.
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Thesis (Ph.D. in Mechanical Engineering)--S.M.U., 2007.Title from PDF title page (viewed Mar. 18, 2008). Source: Dissertation Abstracts International, Volume: 68-03, Section: B, page: 1898. Adviser: Radovan Kovacevic. Includes bibliographical references.
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Ahsan, Muhammad Naveed. "Modelling and analysis of laser direct metal deposition of Ti-6Al-4V alloy." Thesis, University of Manchester, 2011. https://www.research.manchester.ac.uk/portal/en/theses/modelling-and-analysis-of-laser-direct-metal-deposition-of-ti6al4v-alloy(e56c53a4-ca76-4870-89df-b34390b6697a).html.
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A major strength of the laser direct metal deposition (LDMD) rapid manufacturing technique is its ability to manufacture freeform shapes, to directly create different surface coatings on a part, and to produce parts from graded porous to fully dense solid structures. This technique is gaining popularity in the fields of aerospace and biomedical manufacture due to its flexibility and cost effectiveness. Surface coating and repair are its biggest application in industry. Previous models of surface layer coating predicted heat flow in the substrate and the resulting temperature distributions successfully, however layer geometry predictions were absent or incomplete. Here, an analytical modelling method of surface layer coating has been presented which accounts for track interactions and uses a novel powder mass affinity factor in multiple track laser direct metal deposition. The model has been validated by a series of surface layer coating experiments using Ti-6Al-4V alloy. Surface layer characteristics in terms of layer profile, layer thickness and layer roughness have been compared. The model is, then, extended from multiple tracks to multilayer structure fabrication. The multilayer porous structures have been fabricated by using the laser in continuous-wave and pulsed-wave modes for potential use in biomedical applications. In the second part of the work, a coupled analytical-numerical solution has been developed for the single track deposition model described earlier. Laser direct metal deposition is a complex process involving multiple interdependent processes which can be best simulated using a fully coupled mass-energy balance solution and the model removes the shortcoming of previous models where energy and mass balance equations are solved in a decoupled manner. The model has been applied to find out temperature distributions, track profile and microstructure scale, its experimental validation makes it convincing. The model is quite efficient as compared to finite element methods and a useful industrial aid for selecting the parameters to use for laser direct metal deposition when separate geometric and microstructural outcomes are required. In the third part of the work, a comparative study of LDMD characteristics using GA (gas-atomised) and PREP (plasma rotating electrode process) Ti-6Al-4V powders has been presented. The LDMD characteristics in terms of geometric dimensions, surface finish, microstructure, micro hardness and any defects such as intralayer porosity are compared and it is concluded that PREP powder deposition has some potential benefits when high value components are to be built, for example, aerospace applications. This study has also exposed the scientific understanding on the causes of intralayer porosity generation behaviour in laser direct metal deposition. To minimize the intralayer porosity, optimum combinations of processing parameters/ conditions and characteristics of the initial powder, have been proposed for practical engineering applications.
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Patibandla, Aditya Ramamurthy. "Effect of Process Parameters on Surface Roughness and Porosity of Direct Metal Laser Sintered Metals." University of Cincinnati / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1544691813554763.
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Raja, Sandeep. "The systematic development of Direct Write (DW) technology for the fabrication of printed antennas for the aerospace and defence industry." Thesis, Loughborough University, 2014. https://dspace.lboro.ac.uk/2134/14930.
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Low profile, conformal antennas have considerable advantages for Aerospace and Military platforms where conventional antenna system add weight and drag. Direct Write (DW) technology has been earmarked as a potential method for fabricating low profile antennas directly onto structural components. This thesis determines the key design rules and requirements for DW fabrication of planar antennas. From this, three key areas were investigated: the characterisation of DW ink materials for functionality and durability in harsh environments, localised processing of DW inks and the optimisation of DW conductive ink material properties for antenna fabrication. This study mainly focused on established DW technologies such as micro-nozzle and inkjet printing due to their ability to print on conformal surfaces. From initial characterisation studies it was found that silver based micro-nozzle PTF inks had greater adhesion then silver nano-particle inkjet inks but had lower conductivity (2% bulk conductivity of silver as opposed to 8% bulk conductivity). At higher curing temperatures (>300??C) inkjet inks were able to achieve conductivities of 33% bulk conductivity of silver. However, these temperatures were not suitable for processing on temperature sensitive surfaces such as carbon fibre. Durability tests showed that silver PTF inks were able to withstand standard aerospace environments apart from Skydrol immersion. It was found that DW inks should achieve a minimum conductivity of 30% bulk silver to reduce antenna and transmission line losses. Using a localised electroplating process (known as brush plating) it was shown that a copper layer could be deposited onto silver inkjet inks and thermoplastic PTF inks with a copper layer exhibiting a bulk conductivity of 66% bulk copper and 57% bulk copper respectively. This was an improvement on previous electroless plating techniques which reported bulk copper conductivities of 50% whilst also enabling DW inks to be plated without the need for a chemical bath. One of the limitations of many DW ink materials is they require curing or sintering before they become functional. Conventional heat treatment is performed using an oven which is not suitable when processing DW materials onto large structural component. Previous literature has investigated laser curing as means of overcoming this problem. However, lasers are monochromatic and can therefore be inefficient when curing materials that have absorption bands that differ from the laser wavelength. To investigate this, a laser diode system was compared to a broadband spot curing system. In the curing trials it was found that silver inks could be cured with much lower energy density (by a factor of 10) using the broadband white light source. Spectroscopy also revealed that broadband curing could be more advantageous when curing DW dielectric ink materials as these inks absorb at multiple wavelengths but have low heat conductivity. Themodynamical modelling of the curing process with the broadband heat source was also performed. Using this model it was shown that the parameters required to cure the ink with the broadband heat source only caused heat penetration by a few hundred micro-metres into the top surface of the substrate at very short exposure times (~1s). This suggested that this curing method could be used to process the DW inks on temperature sensitive materials without causing any significant damage. Using a combination of the developments made in this thesis the RF properties of the DW inks were measured after broadband curing and copper plating. It was found that the copper plated DW ink tracks gave an equivalent transmission line loss to a copper etched line. To test this further a number of GPS patch antennas were fabricated out of the DW ink materials. Again the copper plated antenna gave similar properties to the copper etched antenna. To demonstrate the printing capabilities of the micro-nozzle system a mock wireless telecommunications antenna was fabricated on to a GRP UAV wing. In this demonstrator a dielectric and conductive antenna pattern was fabricated on to the leading edge of the wing component using a combination of convection curing and laser curing (using an 808nm diode laser).
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Nyembwe, K., Beer D. De, der Walt K. Van, and S. Bhero. "Time and cost assessment of the manufacturing of tooling by metal casting in rapid prototyping sand moulds." Interim : Interdisciplinary Journal, Vol 10 , Issue 1: Central University of Technology Free State Bloemfontein, 2011. http://hdl.handle.net/11462/335.
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Published ArticleIn this paper the time and cost parameters of tooling manufacturing by metal casting in rapid prototyping sand moulds are assessed and comparison is made with alternative tool making processes such as computer numerical control machining and investment casting (Paris Process). To that end two case studies obtained from local companies were carried out. The tool manufacturing was conducted according to a five steps process chain referred to as Rapid Casting for Tooling (RCT). These steps include CAD modelling, casting simulation, rapid prototyping, metal casting and finishing operations. In particular the Rapid Prototyping (RP) step for producing the sand moulds was achieved with the aid of an EOSINT S 550 Laser Sintering machine and a Spectrum 510 Three Dimensional Printer. The results indicate that RP is the rate determining step and cost driver of the proposed tooling manufacturing technique. In addition it was found that this tool making process is faster but more expensive than machining and investment casting.
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Verma, Anoop Prakash. "Minimizing build time and surface inaccuracy of direct metal laser sintered parts an artificial intelligence based optimization approach /." Cincinnati, Ohio : University of Cincinnati, 2009. http://rave.ohiolink.edu/etdc/view.cgi?acc_num=ucin1249840383.
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Thesis (M.S.)--University of Cincinnati, 2009.Advisor: Sam Anand. Title from electronic thesis title page (viewed Jan. 15, 2010). Includes abstract. Keywords: Direct Metal Laser Sintering; Volumetric Error; Optimization; Genetic Algorithm; .STL. Includes bibliographical references.
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Borkar, Tushar Murlidhar. "Processing and Characterization of Nickel-Carbon Base Metal Matrix Composites." Thesis, University of North Texas, 2014. https://digital.library.unt.edu/ark:/67531/metadc500026/.
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Carbon nanotubes (CNTs) and graphene nanoplatelets (GNPs) are attractive reinforcements for lightweight and high strength metal matrix composites due to their excellent mechanical and physical properties. The present work is an attempt towards investigating the effect of CNT and GNP reinforcements on the mechanical properties of nickel matrix composites. The CNT/Ni (dry milled) nanocomposites exhibiting a tensile yield strength of 350 MPa (about two times that of SPS processed monolithic nickel ~ 160 MPa) and an elongation to failure ~ 30%. In contrast, CNT/Ni (molecular level mixed) exhibited substantially higher tensile yield strength (~ 690 MPa) but limited ductility with an elongation to failure ~ 8%. The Ni-1vol%GNP (dry milled) nanocomposite exhibited the best balance of properties in terms of strength and ductility. The enhancement in the tensile strength (i.e. 370 MPa) and substantial ductility (~40%) of Ni-1vol%GNP nanocomposites was achieved due to the combined effects of grain refinement, homogeneous dispersion of GNPs in the nickel matrix, and well-bonded Ni-GNP interface, which effectively transfers stress across metal-GNP interface during tensile deformation. A second emphasis of this work was on the detailed 3D microstructural characterization of a new class of Ni-Ti-C based metal matrix composites, developed using the laser engineered net shaping (LENSTM) process. These composites consist of an in situ formed and homogeneously distributed titanium carbide (TiC) as well as graphite phase reinforcing the nickel matrix. 3D microstructure helps in determining true morphology and spatial distribution of TiC and graphite phase as well as the phase evolution sequence. These Ni-TiC-C composites exhibit excellent tribological properties (low COF), while maintaining a relatively high hardness.
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Patil, Amit k. "ADVANCED PROCESSING OF NICKEL-TITANIUM-GRAPHITE BASED METAL MATRIX COMPOSITES." Cleveland State University / OhioLINK, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=csu1560298763233401.
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Morville, Simon. "Modélisation multiphysique du procédé de Fabrication Directe par Projection Laser en vue d'améliorer l'état de surface final." Lorient, 2012. http://www.theses.fr/2012LORIS280.
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Lindell, David. "Process Mapping for Laser Metal Deposition of Wire using Thermal Simulations : A prediction of material transfer stability." Thesis, Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:kau:diva-85474.
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Additive manufacturing (AM) is a quickly rising method of manufacturing due to its ability to increase design freedom. This allows the manufacturing of components not possible by traditional subtractive manufacturing. AM can greatly reduce lead time and material waste, therefore decreasing the cost and environmental impact. The adoption of AM in the aerospace industry requires strict control and predictability of the material deposition to ensure safe flights. The method of AM for this thesis is Laser Metal Deposition with wire (LMD-w). Using wire as a feedstock introduces a potential problem, the material transfer from the wire to the substrate. This requires all process parameters to be in balance to produce a stable deposition. The first sign of unbalanced process parameters are the material transfer stabilities; stubbing and dripping. Stubbing occurs when the energy to melt the wire is too low and the wire melts slower than required. Dripping occurs when too much energy is applied and the wire melts earlier than required. These two reduce the predictability and stability that is required for robust manufacturing. Therefore, the use of thermal simulations to predict the material transfer stability for LMD-w using Waspaloy as the deposition material has been studied. It has been shown that it is possible to predict the material transfer stability using thermal simulations and criterions based on preexisting experimental data. The criterion for stubbing checks if the completed simulation result produces a wire that ends below the melt pool. For dripping two criterions shows good results, the dilution ratio is a good predictor if the tool elevation remains constant. If there is a change in tool elevation the dimensionless slenderness number is a better predictor. Using these predictive criterions it is possible to qualitatively map the process window and better understand the influence of tool elevation and the cross-section of the deposited material.Additiv tillverkning (AT) är en kraftigt växande tillverkningsmetod på grund av sin flexibilitet kring design och möjligheten att skapa komponenter som inte är tillverkningsbara med traditionell avverkande bearbetning. AT kan kraftigt minska tid- och materialåtgång och på så sett minskas kostnader och miljöpåverkan. Införandet av AT i flyg- och rymdindustrin kräver strikt kontroll och förutsägbarhet av processen för att försäkra sig om säkra flygningar. Lasermetalldeponering av tråd är den AT metod som hanteras i denna uppsats. Användandet av tråd som tillsatsmaterial skapar ett potentiellt problem, materialöverföringen från tråden till substratet. Detta kräver att alla processparametrar är i balans för att få en jämn materialöverföring. Är processen inte balanserad syns detta genom materialöverföringsstabiliteterna stubbning och droppning. Stubbning uppkommer då energin som tillförs på tråden är för låg och droppning uppkommer då energin som tillförs är för hög jämfört med vad som krävs för en stabil process. Dessa två fenomen minskar möjligheterna för en kontrollerbar och stabil tillverkning. På grund av detta har användandet utav termiska simuleringar för att prediktera materialöverföringsstabiliteten för lasermetalldeponering av tråd med Waspaloy som deponeringsmaterial undersökts. Det har visat sig vara möjligt att prediktera materialöverföringsstabiliteten med användning av termiska simuleringar och kriterier baserat på tidigare experimentell data. Kriteriet för stubbning kontrolleras om en slutförd simulering resulterar i en tråd som når under smältan. För droppning finns två fungerande kriterier, förhållandet mellan svetshöjd och penetrationsdjup om verktygshöjden är konstant, sker förändringar i verktygshöjden är det dimensionslös ”slenderness” talet ett bättre kriterium. Genom att använda dessa kriterier är det möjligt att kvalitativt kartlägga processfönstret och skapa en bättre förståelse för förhållandet mellan verktygshöjden och den deponerade tvärsnittsarean.