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Jack, William Josiah. "A Six Sigma Approach to Implementing Conformal Cooling on Existing Processes in Injection Molding." OpenSIUC, 2017. https://opensiuc.lib.siu.edu/theses/2214.
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Injection molding is one of the most common methods of mass production. After injecting molten plastic into a mold, the heat must leave the plastic material, enter the mold steel, enter the coolant, and exit the mold. This heat flow is critical to producing high quality parts rapidly. As plastic cools, the plastic shrinks. Uneven cooling causes uneven shrinkage which can cause the part to warp from the resulting internal stresses or create sink marks on the part. Thus the effect of uneven cooling is lower part quality, both in appearance and in dimension. Standard or conventional cooling channels are straight-drilled holes arranged such that they intersect and connect to form a loop for coolant, typically water, to flow through. This allows the mold to act as a heat exchanger, transferring heat to the coolant and carrying heated coolant away from the mold. While standard cooling channels have been used widely in the injection molding industry for their manufacturability and proven results, other methods have been developed for creating molds with cooling channels of any desired path or shape. These channels, called conformal due to how they conform to the shape of the part, provide uniform cooling, eliminate or reduce the quality issues of warpage and shrinkage, and provide faster, more economical cycle times. Conformal cooling is cannot be produced only by subtractive manufacturing methods that remove material from raw stock but rather through additive or hybrid manufacturing techniques that add material in layers of powder, sections, or sheets. Bonded sheet layer mold inserts can be made of any size and are currently the only feasible way of making large, conformally-cooled molds. Presented is a Six Sigma approach for implementing conformal cooling in existing molds to achieve the benefits of higher part quality and fast cycle times. Feasibility considerations include existing mold features such as slides and ejectors, choice of channel diameter, and the cooling channel path. Cost justification considerations include assessing part quality cost impact through calculation of the costs of poor quality and assessing machine capacity as relates to cycle time. With the approach presented, an injection molding company should be able to assess feasibility and cost effectiveness of implementing conformal cooling on its molds.
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Mordenti, Eugenio. "Comportamento a fatica dell’acciaio Maraging MS1 prodotto tramite DMLS: influenza della posizione nella camera." Bachelor's thesis, Alma Mater Studiorum - Università di Bologna, 2018. http://amslaurea.unibo.it/16511/.
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L’obiettivo principale di questo studio è caratterizzare dei provini, prodotti mediante additive manufacturing, con il metodo DMLS (direct metal laser sintering), a fatica mediante prove di flessione rotante. I provini sono realizzati in Maraging steel, le cui caratteristiche meccaniche e composizione sono di seguito enunciate. I dati sperimentali ottenuti dalle prove vengono poi elaborati tramite la normativa ISO 12107-2012, per trovare la curva di fatica S-N, sia usando un’interpolazione lineare, che una quadratica, per confrontarle in modo da identificare quale metodologia approssima meglio i dati. E' inoltre utilizzata la normativa Dixon tramite uno stair-caise per trovare la tensione limite di fatica.
Un altro aspetto rilevante di questo elaborato è quello di analizzare il processo produttivo dei provini per capire quali sono i principali parametri che influenzano l’additive manufacturing e che conseguenze hanno sulla vita a fatica dei componenti realizzati. Per questo studio sono stati utilizzati tre set di provini (ogni set ha numerosità pari a 12) numerati dal 20 al 22. I set vengono trattati termicamente, lavorati alle macchine utensili, pallinati e sono analizzati nel dettaglio i processi appena citati. Legato a questi studi c’è il tentativo di trovare una correlazione tra la posizione di realizzazione dei provini in camera e la vita a fatica.
Infine si esegue un’analisi frattografica per capire meglio i meccanismi di innesco e propagazione delle cricche per fatica.
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Ramosoeu, Makhabo Khabiso Ellen. "Characterisation and static behaviour of the DMLS Ti-6AI-4V for Bio-medical applications." Thesis, Bloemfontein: Central University of Technology, Free State, 2015. http://hdl.handle.net/11462/275.
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Thesis (M. Tech. (Engineering: Mechanical)) -- Central University of Technology, Free State,The Centre for Rapid Prototyping and Manufacturing (CRPM) at the Central University of Technology, Free State (CUT) manufactures implants using Electro Optical Systems (EOS) titanium Ti-6Al-4V alloy powder (further referred to as EOS Ti64 powder) by means of Direct Metal Laser Sintering (DMLS) process on the EOSINT M 270 machine. For this reason, there is a need to characterise and acquire knowledge of the basic properties of direct metal laser sintered EOS titanium Ti-6Al-4V alloy samples (further referred to as DMLS Ti64 samples) under static tensile loading in order to provide the CRPM with engineering design data. The first objective of this Master’s study is to acquire the characteristics of EOS Ti64 powder in order to ascertain its suitability in the DMLS process. Secondly, the study aims to assess tensile properties and elastic constants of DMLS Ti64 samples produced from the set process parameters of EOSINT M 270 machine. Thirdly, it is to investigate microstructures of DMLS Ti64 samples subjected to different heat treatment techniques which will eventually assist in the determination of a suitable heat treatment technique that will yield higher ductility. Finally, the study aims to validate the static behaviour of DMLS Ti64 samples subjected to the static tensile loading up to a yield point in order to determine failure due to yielding. The samples were manufactured at CRPM Bloemfontein. The metallographic examinations, heat treatment and the determination of mechanical properties were done at the CSIR in Pretoria. Optical Microscope (OM) and Scanning Electron Microscope (SEM) were used to determine microstructures of DMLS Ti64 samples while Energy Dispersive X-Ray (EDX) analyses were performed using SEM. The samples were heat treated at temperatures of 700, 1000 and 1100°C respectively, and subsequently either cooled with the furnace, air or were water quenched. The mechanical property tests included tensile, hardness and determination of elastic constants. The static behaviour of DMLS Ti64 samples under static tensile load up to a yield point was predicted and verified using ABAQUSTM Finite Element Analysis (FEA). The stress-strain curves from ABAQUSTM were interpreted using MDSolid program. The point of interest was Von Mises yield stress at 0.2% offset, in order to determine failure due to yielding. EOS Ti64 powder particles were spherical in shape and the alpha and alpha+beta phases were identified. As-laser sintered samples possess a very fine and uniform alpha case with islands of martensitic plates; samples were brittle and showed low levels of ductility with an average elongation of 2.6% and an area reduction of 3.51%. Ultrasonic test results showed that DMLS Ti64 samples have Young’s modulus of 115 GPa, Shear modulus of 43 GP, a bulk modulus of 109 GPa and Poisson’s ratio of 0,323 while the density was 4.4 g/cm3. Slow cooling of DMLS Ti64 samples from 1000 and 1100oC resulted in a microstructure constituted more by the alpha phase of lower hardness than those from 700oC and as-laser sintered samples. High hardness was obtained by water quenching. The water quenched samples showed martensitic transformation and high hardness when compared to furnace cooled samples. Beta annealing tailored a microstructure of as-laser sintered samples into a lamellar structure with different lath sizes as per cooling rate. Beta annealing improved ductility levels up to 12.67% elongation for samples furnace cooled for 4 hours and even higher to 18.11% for samples furnace cooled for 34 hours, while area reduction increased to 25.94% and 33.39%, respectively. Beta annealing conversely reduced yield strength by 19.89% and ultimate tensile strength was reduced by 23.66%. The calculated maximum Von Mises stresses found were similar to the FEA interpreted results. The average percentage error, without the stress concentration factor, was approximately 8.29%; with the stress concentration factor included, it was 0.07%. The small reaction forces induced in both x-axis and z-axis contributed to this error of 0.07% between the calculations and ABAQUSTM FEA results. Samples that were not heat treated fell outside the Von Mises criterion and failed due to yielding. This justified the brittleness found in the tensile test results where elongation and area reduction were 2.6% and 3.51% respectively. However, all samples that were heat treated fell within the Von Mises criterion. The objectives of this study were achieved; the mechanical properties were similar to those of standard specification for wrought annealed Ti-6Al-4V alloy for surgical implant applications and EOS GmbH manufacturer’s material data sheet. DMLS Ti64 samples must be beta annealed in order to attain higher levels of ductility. A recommendation was made to further investigate the effect of heat treatment on the other mechanical properties. Furthermore, detailed results of basic properties of DMLS Ti64 samples are provided in the appendices in chart format and were written on a CD disc.
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Jaime, Gustavo Carneiro. "Análise comparativa da resistência à corrosão eletroquímica da liga de Ti-6Al-4V e do aço inoxidável AISI316L obtidas por manufatura aditiva visando aplicações biomédicas /." Ilha Solteira, 2017. http://hdl.handle.net/11449/152091.
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Orientador: Ruis Camargo TokimatsuResumo: A procura por materiais, com compatibilidade e funcionalidade biológicas, que possam melhorar a qualidade da vida humana é constante, além da busca de processos de fabricação que atendam às necessidades de manufatura de artefatos de geometria complexa. Os artefatos de aço inoxidável são utilizados por possuírem uma boa biocompatibilidade, baixo custo de produção, mas podem liberar íons como o cobalto, que é carcinogênico. O uso de Ligas de titânio é uma boa alternativa, já que possuem uma maior resistência à corrosão e boa resposta biológica, porém, seu custo é muito elevado. Considerando esses aspectos, o presente trabalho foi realizado buscando estudar, comparativamente, as características de microdureza, microdesgaste e resistência à corrosão de artefatos manufaturados para aplicações biomédicas, aproveitando as características mecânicas da liga de aço inoxidável AISI316L, usado como substrato, com as características eletroquímicas apresentadas pela liga de titânio Ti-6Al-4V, usado como material de tratamento de superfície. A sinterização direta dos metais por laser (DMLS) foi o processo de manufatura escolhido por apresentar as características de fabricação desejadas. Os ensaios realizados foram o de microdureza Vickers, ensaio de desgaste microadesivo por esfera rotativa fixa (esfera-fixa) e para o comparativo da resistência à corrosão eletroquímica foram produzidas curvas de polarização potenciodinâmicas que forneceram os seguintes parâmetros: o potencial de corrosão, a... (Resumo completo, clicar acesso eletrônico abaixo)
Mestre
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Capelli, Alessandro. "Effetto della posizione in camera sulla resistenza a fatica dell'acciaio Maraging MS1 prodotto tramite DMLS." Bachelor's thesis, Alma Mater Studiorum - Università di Bologna, 2019. http://amslaurea.unibo.it/17419/.
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La tecnologia Direct Metal Laser Sintering (DMLS) è una delle più promettenti tra tutti i processi che possono essere raggruppati sotto la definizione di Additive Manufacturing, permettendo la realizzazione di componenti anche molto complessi in breve tempo, a partire da un disegno CAD 3D. In questo studio sono stati realizzati dei provini in acciaio Maraging MS1, fornito dall’azienda EOS sotto forma di polvere, i quali sono stati suddivisi in tre serie in base alla loro posizione nella camera di produzione rispetto al flusso di gas inerte che vi scorre all’interno. I provini sono stati sottoposti ad una precisa serie di trattamenti termici e meccanici, quindi testati a fatica in una macchina per flessione rotante secondo una precisa metodologia sperimentale. I dati raccolti sono stati processati con il metodo Dixon e la norma internazionale ISO 12107 per ricavare il limite di fatica e le relative bande di confidenza. Utilizzando l’ANOVA, si è poi eseguita una comparazione dei dati sperimentali ottenuti con i tre set, non evidenziando significative differenze. L’analisi frattografica delle superfici di frattura ha permesso infine di analizzare più a fondo l’origine e la propagazione delle cricche e stabilire le cause più frequenti che hanno originato la rottura.
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Righini, Nicola. "Prove di fatica a flessione rotante su provini in acciaio inossidabile PH1 ottenuti tramite DMLS." Bachelor's thesis, Alma Mater Studiorum - Università di Bologna, 2019.
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Dalla metà degli anni Ottanta si è assistito all'introduzione dell'Additive Manufacturing (AM), tecnologia completamente innovativa che permette la produzione di componenti a partire da un modello 3D realizzato tramite specifici software. La definizione di AM raggruppa svariati processi, tra cui il DMLS (Direct Metal Laser Sintering), che prevede di formare il pezzo a partire da polvere metallica, successivamente fusa da un raggio laser e lasciata solidificare, così da ottenere la geometria definitiva.
In questo elaborato è stato analizzato come alcuni parametri di processo, in particolare la rugosità e il trattamento termico, influenzino la vita a fatica del componente, ossia il numero di cicli che esso può compiere sopportando un carico al di sotto di quello di snervamento senza giungere a rottura.
Per effettuare lo studio sono state svolte prove di fatica a flessione rotante, attenendosi alla procedura descritta in specifiche normative ISO. Esse prevedono di vincolare dei provini cilindrici di diametro fissato, dei quali sono state rilevate preventivamente le caratteristiche geometriche e superficiali, su un apposito macchinario in grado di metterli in rotazione, ed attendere l'esito della prova, che può essere una sopravvivenza, se il pezzo supera un numero prestabilito di cicli di vita, o una rottura, nel qual caso è stata osservata la superficie di frattura.
Il risultato finale dello studio, conseguito tramite successiva elaborazione statistica dei dati ottenuti dalle prove, è la curva di fatica del materiale, che correla la tensione a cui esso è sottoposto ai cicli di vita che può compiere senza rompersi. Nell'ambito di questa specifica indagine, sono state confrontate le curve di fatica relative a provini realizzati tramite DMLS e in seguito sottoposti a differenti trattamenti meccanici (pallinatura, lavorazione alle macchine utensili) e che hanno subito o meno trattamento termico, così da valutare l'effettivo beneficio dei diversi processi produttivi.
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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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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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Ravaioli, Irma. "Resistenza a fatica di pezzi in acciaio realizzati per DMLS a seconda di diversi parametri costruttivi." Bachelor's thesis, Alma Mater Studiorum - Università di Bologna, 2016.
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Scopo della ricerca è stato quello di studiare la resistenza a fatica di provini in maraging steel (MS1) e in stainless steel (PH1), realizzati mediante processo DMLS, in funzione di due parametri: direzione di accrescimento e forma finale del provino (ovvero sovrametallo asportato mediante macchine utensili).
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Piraccini, Giorgio. "Prove sperimentali di fatica a flessione rotante su provini in acciaio inossidabile PH1 ottenuti per DMLS." Bachelor's thesis, Alma Mater Studiorum - Università di Bologna, 2019.
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L’avvento dell’Additive Manufacturing e la sua sempre maggiore flessibilità, resa possibile dallo sviluppo tecnologico, sta suscitando l’interesse dei progettisti i quali sempre più spesso ne considerano l’impiego per la realizzazione di componenti particolarmente complessi e/o difficilmente ottenibili tramite tecnologie tradizionali di asportazione di truciolo.
Oltre ai componenti sottoposti a carichi statici, il cui comportamento è valutabile tramite FEM (Finite Element Method), è ricorsivo l’impiego di membri meccanici in regimi di tensione alterna che ne comportano un carico a fatica; la valutabilità di tutti i fattori in gioco risulta dunque fondamentale per la realizzazione di componenti opportunamente dimensionati e capaci di lavorare in condizioni più specifiche e gravose.
In particolare, l’interesse dell’elaborato è rivolto verso l’impatto di rugosità superficiale e trattamento termico sul comportamento a fatica del materiale, considerando provini cilindrici a sezione variabile realizzati in acciaio inossidabile PH1 e sottoposti a flessione rotante.
L’analisi di ciascun provino ne comprende la rilevazione di caratteristiche geometriche e costruttive, nonché l’osservazione dei provini giunti a rottura per comprendere cause ed effetti di quest’ultima. Per ultima si esegue l’elaborazione dei dati ottenuti in seguito alla prova di fatica ed ottenimento delle relative curve di fatica a seguito di opportune valutazioni statistiche.
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Langer, H. J., and M. Shellabear. "Recent e-Manufacturing solutions developed by EOS." Journal for New Generation Sciences, Vol 4, Issue 1: Central University of Technology, Free State, Bloemfontein, 2006. http://hdl.handle.net/11462/492.
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Published Articlee-Manufacturing means the fast, flexible and cost-effective production of parts directly from electronic data, which can include rapid prototyping, rapid tooling, (spare) parts on demand etc. Especially interesting is the direct manufacture of enduse parts. In this paper, recent case studies will be presented showing commercial e-Manufacturing projects including small production batches and mass customized series production from various industrial branches. The paper also discusses the relevance of several recent technological innovations in laser-sintering for e- Manufacturing, especially how increasing the productivity of machines and process chains has increased the range of applications which are cost-effective using lasersintering.
Case studies include:
- small series production (up to a few thousand p.a.) of products
- production of customized (one-off) products
- mass production of customer-specific (mass customized) products
- optimized tooling concepts for production of up to millions of products
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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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Magnani, Alessandro. "Effetto del trattamento termico e della lavorazione meccanica sulla resistenza a fatica dell’acciaio Maraging Steel MS1 accresciuto tramite DMLS." Bachelor's thesis, Alma Mater Studiorum - Università di Bologna, 2017.
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Le nuove tecnologie di additive manufacturing consentono l'accrescimento di provini di geometria complessa mediante la fusione di polveri di leghe metalliche. La seguente trattazione intende focalizzarsi sull'incidenza dei fattori "lavorazione" e "trattamento termico" sulla vita a fatica di componenti in acciaio maraging, ottenuti mediante tecnica DMLS. In particolare, una volta classificate le serie, sono state costruite le curve S-N mediante prove di flessione rotante. I risultati sono poi stati elaborati per trovare il limite di fatica, le bande di confidenza e sono state valutate, mediante metodo ANOVA, le incidenze dei fattori sulla vita a fatica. Grazie alle analisi al microscopio, infine, è stato possibile individuare la propagazione del danno lungo le superfici di frattura dei provini.
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Tondini, Fabio. "Resistenza a fatica dell’acciaio Maraging MS1 prodotto tramite DMLS: effetto dei trattamenti post-processo e della posizione in camera." Bachelor's thesis, Alma Mater Studiorum - Università di Bologna, 2018. http://amslaurea.unibo.it/16556/.
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Determinazione del limite di fatica e delle curve S-N di fatica, realizzate sottoponendo provini di acciaio Maraging MS1, realizzati dalla ditta tedesca EOS mediante additive manufacturing dalla macchina per DMLS, EOSINT M280, a prove di flessione rotante pure.
Per l’elaborazione dati è stata seguita la normativa ISO 12107, al fine di stimare il limite di fatica e le bande di confidenza delle curve S-N ottenute sperimentalmente; sono, inoltre, stati presi in considerazione la posizione in camera di realizzazione e i trattamenti post-processo come il trattamento termico, la pallinatura e lavorazione in macchina, per osservare come questi possano influire sulle proprietà meccaniche e la vita a fatica del componente ottenuto. Infine grazie alle analisi frattografiche, è stato possibile individuare la causa della rottura e la propagazione della cricca lungo le superfici di frattura dei provini.
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Bigazzi, Elena. "Effetto dello spessore di sovrametallo rimosso nella lavorazione meccanica sulla resistenza a fatica dell’acciaio Maraging Steel MS1 accresciuto tramite DMLS." Bachelor's thesis, Alma Mater Studiorum - Università di Bologna, 2017.
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La tecnologia DMLS (Direct Metal Laser Sintering), che fa parte delle tecnologie di additive manufacturing, consente di realizzare, strato dopo strato, oggetti di geometrie anche molto complesse a partire da polveri di leghe metalliche e dal disegno CAD 3D. In questo studio sono state analizzate tre serie di provini fabbricate dalla macchina per DMLS EOSINT M280, prodotta in Germania e installata nel laboratorio “3D Impulse” della Facoltà di Ingegneria Meccanica di Kraljevo, Serbia. Le serie di provini inviate dalla Serbia sono realizzate in acciaio maraging (EOS Maraging Steel MS1), un particolare acciaio ad alte prestazioni meccaniche utilizzato in campo navale e aeronautico. A ognuna di queste serie è stata asportata, dopo il processo DMLS, una differente quantità di sovrametallo per tornitura. I provini sono stati testati a fatica in una macchina per flessione rotante (ITALSIGMA 2 TM 831) seguendo una precisa metodologia sperimentale. Dopodichè, i dati ottenuti sono stati analizzati statisticamente col metodo Dixon e con la normativa ISO 12107 al fine di stimare il limite di fatica e le bande di confidenza delle curve S-N ottenute sperimentalmente. In secondo luogo sono state analizzate al microscopio le superfici di rottura dei provini per identificare i più frequenti difetti potenzialmente responsabili del cedimento. Infine, allo scopo di confrontare i dati sperimentali, è stata svolta l’analisi della varianza (ANOVA) prendendo in considerazione due ulteriori serie con dati di letteratura. Con l’ANOVA è stata decretata l’influenza o meno del fattore sovrametallo asportato sulla resistenza a fatica.
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Longhitano, Guilherme Arthur 2015. "Estudo de tratamentos térmicos e acabamentos de superfície na liga Ti-6Al-4V produzida via DMLS para aplicação em implantes." [s.n.], 2016. http://repositorio.unicamp.br/jspui/handle/REPOSIP/265833.
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Orientador: Maria Clara Filippini IerardiDissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecânica
Made available in DSpace on 2018-08-26T21:12:43Z (GMT). No. of bitstreams: 1 Longhitano_GuilhermeArthur_2015_M.pdf: 10352364 bytes, checksum: 6157c8c85d67a80202c0078ff2bd5901 (MD5) Previous issue date: 2016
Resumo: No presente trabalho, a liga de titânio Ti-6Al-4V, empregada em implantes ortopédicos permanentes ou temporários devido à sua biocompatibilidade, foi produzida a partir da manufatura aditiva utilizando o processo de Sinterização Direta de Metais por Laser (DMLS). O material foi submetido a diferentes tratamentos térmicos com o intuito de modificar suas propriedades mecânicas, e a acabamentos de jateamento, ataque químico e polimento eletroquímico para analisar os efeitos dos mesmos no acabamento de superfície. As modificações resultantes após os tratamentos térmicos e acabamentos de superfície foram analisadas por microscopia óptica, microscopia eletrônica de varredura, difração de raios-X, medidas de rugosidade e massa, microdureza Vickers, e ensaios de tração e compressão. No estudo de acabamentos de superfície, o menor valor de rugosidade foi obtido após as etapas de jateamento e ataque químico combinadas. O acabamento de jateamento é responsável por deixar uma superfície com rugosidade uniforme, enquanto o ataque químico é responsável pela limpeza da superfície e redução da rugosidade. As amostras foram submetidas aos tratamentos térmicos nas temperaturas de 850 ºC, 950 ºC e 1050 ºC durante uma hora com resfriamento em forno. Foi constatado que quanto maior a temperatura empregada, maior é a ductilidade do material e, por outro lado, menor é a resistência mecânica. Tal fato ocorreu devido à maior nucleação e crescimento da fases 'alfa' e 'beta' no material, que apresentava inicialmente uma estrutura constituída por martensita hexagonal ('alfa'). A condição de tratamento térmico a 950 ºC foi a que apresentou a melhor relação de propriedades mecânicas, satisfazendo os requerimentos da norma ASTM F136 para a utilização da liga Ti-6Al-4V em implantes
Abstract: In this study, the Ti-6Al-4V titanium alloy, used in permanent or temporary orthopedic implants due to its biocompatibility, was produced by additive manufacturing using the Direct Metal Laser Sintering (DMLS) process. The material was subjected to different heat treatments in order to modify their mechanical properties, and to the surface finishes of blasting, chemical etching and electropolishing to analyze their effects on surface finish. The resulting changes after the heat treatments and surface finishes were analyzed by optical microscopy, scanning electron microscopy, X-ray diffraction, roughness and mass measurements, Vickers microhardness, and tensile and compression tests. In surface finishes study, the lowest roughness value was obtained after the combined steps of blasting and chemical etching. The blasting finish is responsible for leaving a surface with uniform roughness, while the chemical etching is responsible for cleaning the surface and reducing roughness. The samples were subjected to heat treatments at temperatures of 850 °C, 950 °C and 1050 °C for one hour followed by furnace cooling. It has been found that the higher the temperature employed, the higher the ductility of the material and, on the other hand, the lower the mechanical strength. This happened due to increased nucleation and growth of 'alfa' and 'beta' phases in the material, which initially had a structure made of hexagonal martensite ('alfa'). The condition of heat treatment at 950 ° C showed the best relation of mechanical properties, meeting the requirements of ASTM F136 for the use of Ti-6Al-4V alloy in implants
Mestrado
Materiais e Processos de Fabricação
Mestre em Engenharia Mecânica
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KRISHNAN, MANICKAVASAGAM. "Investigation of material and mechanical properties of Al alloy and Al based MMC parts produced by DMLS for industrial application." Doctoral thesis, Politecnico di Torino, 2014. http://hdl.handle.net/11583/2530290.
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Additive Manufacturing (AM) is the process of joining materials layer upon layer to produce parts from CAD model. Direct Metal Laser Sintering (DMLS) is an AM process in which metallic parts can be produced. The knowledge of material and mechanical properties are important for producing lightweight and functional parts. Hence, this thesis focuses on characterizing material and mechanical properties of a lightweight alloy processed by DMLS, and using it as metal matrix for producing composites in DMLS process.
AlSi10Mg was selected as lightweight alloy and it is similar to an A360 cast alloy in chemical composition. The morphology and size distribution of the AlSi10Mg starting powder was investigated by using Field Emission Scanning Electron Microscope (FESEM) and laser granulometry, respectively. Chemical composition of the AlSi10Mg powder was analyzed by using Inductive Coupled Plasma test. Material characterization of AlSi10Mg specimen produced by DMLS was carried out by using optical microscope, FESEM and X-ray Diffraction technique (XRD). Thereafter, mechanical properties such as hardness, tensile strength and Charpy impact energy were evaluated. Effect of different post processing operations on mechanical properties of AlSi10Mg parts were also investigated. Due to the very fine microstructure of the AlSi10Mg parts produced by DMLS process, nanoindentation measurements were performed. Investigation of process parameters and their effect on final density and hardness of AlSi10Mg specimens based on Design of Experiments (DOE) approach was carried out. Regression analysis was also conducted. Effect of the heat treatment (e.g. precipitation hardening T6) on the AlSi10Mg parts was also investigated.
Composite materials offer better properties comparing to traditional materials. The Metal Matrix Composite was produced by DMLS process. The matrix was of AlSi10Mg and 10 wt% SiC was used as ceramic reinforcement. The microstructure of the composite was studied by using optical microscopy and FESEM. Evaluation of mechanical properties of the composite specimens was carried out.
Finally, the production of a complex shape lightweight structure by DMLS was studied.
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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/.
Full textAbstract:
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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Gregolin, Rafael Ferreira [UNESP]. "Desenvolvimento, comportamento mecânico e microestrutural de uma prótese mandibular em liga de titânio produzida por sinterização direta a laser de metal (DMLS)." Universidade Estadual Paulista (UNESP), 2013. http://hdl.handle.net/11449/94477.
Full textAbstract:
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gregolin_rf_me_ilha.pdf: 3746269 bytes, checksum: b2a1686375b3a28a8709c13b5b75a4bd (MD5)A prototipagem rápida está sendo utilizada em diversas áreas do conhecimento humano para auxiliar no estudo e muitas vezes na própria fabricação do componente usual. Atualmente, com o avanço de softwares, pode-se criar com facilidade imagens tridimensionais, ou mesmo, capturar essas imagens de equipamentos como a tomografia computadorizada e a ressonância magnética. Consegue-se reproduzir qualquer parte do corpo humano com grande perfeição e isso é utilizado na fabricação de implantes, scaffolds (arcabouços – engenharia de tecidos), materiais de auxílio e preparação em cirurgias (biomodelos). Os principais materiais utilizados na fabricação de implantes hoje são: o titânio puro, as ligas de titânio, o aço inoxidável, o polietileno, o PMMA, as ligas de cobalto-cromo e as cerâmicas. Este trabalho se propõe a fazer: um estudo mecânico e microestrutural da liga Ti-6Al-4V obtida por prototipagem rápida no processo de sinterização direta a laser de metais (DMLS) e compará-la com a liga Ti-6Al-4V produzida por processos convencionais de conformação (trefilação). Além disso, pretende realizar o desenvolvimento de uma placa condilar personalizada utilizada para patologias de distúrbios de ATM (articulação têmporo-mandibular), avaliando sua geometria pelo software ANSYS®, com o apoio da tomografia computadoriza e do software de construção de imagens tridimensionais INVESALIUS®
Rapid prototyping is being used in various areas of human knowledge to assist in the study and often in the usual component manufacturing. Today, with the advancement of software, you can easily create three-dimensional images, or even, capture these images of equipment such as computed tomography and magnetic resonance imaging. You able to reproduce any part of the human body with great perfection and it’s used in the manufacture of implants, scaffolds (tissue engineering), material aid and preparation for surgery (biomodels). The main materials used in the manufacture of implants today are: pure titanium, titanium alloys, stainless steel, polyethylene, PMMA, the cobalt-chromium alloys and ceramics. This paper proposes to do: mechanical and microstructural studies of alloy Ti-6Al-4V obtained by rapid prototyping process in direct metal laser sintering (DMLS) and compare it with the Ti-6Al-4V alloy produced by conventional forming process (wiredrawing). Also, make the development of a custom condylar plate used for diseases of TMJ (temporomandibular joint) disorders, assessing its geometry by ANSYS® software with the help of computerized tomography and the software to build three-dimensional images INVESALIUS®
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Gregolin, Rafael Ferreira. "Desenvolvimento, comportamento mecânico e microestrutural de uma prótese mandibular em liga de titânio produzida por sinterização direta a laser de metal (DMLS) /." Ilha Solteira, 2013. http://hdl.handle.net/11449/94477.
Full textAbstract:
Orientador: Ruis Camargo TokimatsuBanca: João Antonio Pereira
Banca: Cecilia Amelia de Carvalho Zavaglia
Resumo: A prototipagem rápida está sendo utilizada em diversas áreas do conhecimento humano para auxiliar no estudo e muitas vezes na própria fabricação do componente usual. Atualmente, com o avanço de softwares, pode-se criar com facilidade imagens tridimensionais, ou mesmo, capturar essas imagens de equipamentos como a tomografia computadorizada e a ressonância magnética. Consegue-se reproduzir qualquer parte do corpo humano com grande perfeição e isso é utilizado na fabricação de implantes, scaffolds (arcabouços - engenharia de tecidos), materiais de auxílio e preparação em cirurgias (biomodelos). Os principais materiais utilizados na fabricação de implantes hoje são: o titânio puro, as ligas de titânio, o aço inoxidável, o polietileno, o PMMA, as ligas de cobalto-cromo e as cerâmicas. Este trabalho se propõe a fazer: um estudo mecânico e microestrutural da liga Ti-6Al-4V obtida por prototipagem rápida no processo de sinterização direta a laser de metais (DMLS) e compará-la com a liga Ti-6Al-4V produzida por processos convencionais de conformação (trefilação). Além disso, pretende realizar o desenvolvimento de uma placa condilar personalizada utilizada para patologias de distúrbios de ATM (articulação têmporo-mandibular), avaliando sua geometria pelo software ANSYS®, com o apoio da tomografia computadoriza e do software de construção de imagens tridimensionais INVESALIUS®
Abstract: Rapid prototyping is being used in various areas of human knowledge to assist in the study and often in the usual component manufacturing. Today, with the advancement of software, you can easily create three-dimensional images, or even, capture these images of equipment such as computed tomography and magnetic resonance imaging. You able to reproduce any part of the human body with great perfection and it's used in the manufacture of implants, scaffolds (tissue engineering), material aid and preparation for surgery (biomodels). The main materials used in the manufacture of implants today are: pure titanium, titanium alloys, stainless steel, polyethylene, PMMA, the cobalt-chromium alloys and ceramics. This paper proposes to do: mechanical and microstructural studies of alloy Ti-6Al-4V obtained by rapid prototyping process in direct metal laser sintering (DMLS) and compare it with the Ti-6Al-4V alloy produced by conventional forming process (wiredrawing). Also, make the development of a custom condylar plate used for diseases of TMJ (temporomandibular joint) disorders, assessing its geometry by ANSYS® software with the help of computerized tomography and the software to build three-dimensional images INVESALIUS®
Mestre
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Britto, Carlos Eduardo Silva. "Influência da orientação de prototipagem no comportamento mecânico da liga Ti-6Al-4V produzida por sinterização direta de metal por laser (DMLS) /." Ilha Solteira, 2015. http://hdl.handle.net/11449/145475.
Full textAbstract:
Orientador: Ruís Camargo TokimatsuBanca: Juno Gallego
Banca: Maria Aparecida Larosa
Resumo: Este trabalho tem por objetivo realizar uma análise das propriedades mecânicas e microestruturais de componentes da liga Ti-6Al-4V produzidos pelo processo de Sinterização Direta de Metal por Laser (DMLS) que se baseia na deposição de camadas de um pó metálico que posteriormente são fundidas através de um feixe de laser de alta potência. Sendo assim, foram produzidos componentes em três orientações diferentes (A, B e C) com o propósito de verificar a influência das camadas sobre as propriedades mecânicas e nos micromecanismos de fratura, através dos ensaios de tração, fadiga e tenacidade à fratura e microscopia eletrônica de varredura (MEV). As amostras também foram submetidas a um tratamento térmico para alívio de tensões residuais provenientes do processo de fabricação e posteriormente analisadas através de microscopia óptica e difração de raios-X, para averiguar se houve mudanças em sua microestrutura ou decomposição de fase em relação a uma amostra sem tratamento térmico na condição "como produzida". As orientações de construção B e C apresentaram melhores valores em todos os ensaios mecânicos quando comparados à orientação A, evidenciando assim que houve perda de resistência mecânica, exceto no ensaio de microdureza, onde os valores médios não tiveram grandes variações com a orientação de manufatura. A amostra "como produzida" apresentou maiores valores de dureza quando comparada às amostras com tratamento de alívio de tensões residuais, fato este que ocorreu devido à precipitação da fase B e crescimento da fase a no material, que inicialmente apresentava uma estrutura composta por martensita hexagonal (a')
Abstract: This work has as objective to realize analysis of the mechanical and microstructural properties of Ti-6Al-4V alloy components produced by the Direct Metal Laser Sintering (DMLS) process that is based on the deposition of a metal powder layers and posteriorly fused by a high power laser beam. Therefore, components were produced in three different orientations (A, B and C) in order to verify the influence of the layers deposition on the mechanical properties and fracture micromechanisms, through the tensile tests, fatigue and tenacity of fracture and scanning electron microscopy (SEM). The samples were also subjected to a heat treatment to relieve residual stresses resulting from the manufacturing process and after analyzed through a optical microscopy and X-ray diffraction, to ascertain if there were changes in the microstructure or phase decomposition in relation to a sample without a heat treatment and at "as manufactured" condition. The construction orientation B and C have had better values in all mechanical tests when compared to the orientation A, revealing that had a loss of mechanical strength, except in the microhardness test, where the average values did not have large variations in the orientation of manufacturing. The sample "as manufactured" presented higher hardness values when compared to samples with treatment to relieve the residual stress, and this fact occurred due the precipitation of the B phase and the growth of the a phase in the material, which initially had a structure consisting of martensite hexagonal (a')
Mestre
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Britto, Carlos Eduardo Silva [UNESP]. "Influência da orientação de prototipagem no comportamento mecânico da liga Ti-6Al-4V produzida por sinterização direta de metal por laser (DMLS)." Universidade Estadual Paulista (UNESP), 2015. http://hdl.handle.net/11449/145475.
Full textAbstract:
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000870790.pdf: 7892118 bytes, checksum: 926da8111d0d883df7f587ca01ee6dfd (MD5)Este trabalho tem por objetivo realizar uma análise das propriedades mecânicas e microestruturais de componentes da liga Ti-6Al-4V produzidos pelo processo de Sinterização Direta de Metal por Laser (DMLS) que se baseia na deposição de camadas de um pó metálico que posteriormente são fundidas através de um feixe de laser de alta potência. Sendo assim, foram produzidos componentes em três orientações diferentes (A, B e C) com o propósito de verificar a influência das camadas sobre as propriedades mecânicas e nos micromecanismos de fratura, através dos ensaios de tração, fadiga e tenacidade à fratura e microscopia eletrônica de varredura (MEV). As amostras também foram submetidas a um tratamento térmico para alívio de tensões residuais provenientes do processo de fabricação e posteriormente analisadas através de microscopia óptica e difração de raios-X, para averiguar se houve mudanças em sua microestrutura ou decomposição de fase em relação a uma amostra sem tratamento térmico na condição como produzida. As orientações de construção B e C apresentaram melhores valores em todos os ensaios mecânicos quando comparados à orientação A, evidenciando assim que houve perda de resistência mecânica, exceto no ensaio de microdureza, onde os valores médios não tiveram grandes variações com a orientação de manufatura. A amostra como produzida apresentou maiores valores de dureza quando comparada às amostras com tratamento de alívio de tensões residuais, fato este que ocorreu devido à precipitação da fase B e crescimento da fase a no material, que inicialmente apresentava uma estrutura composta por martensita hexagonal (a')
This work has as objective to realize analysis of the mechanical and microstructural properties of Ti-6Al-4V alloy components produced by the Direct Metal Laser Sintering (DMLS) process that is based on the deposition of a metal powder layers and posteriorly fused by a high power laser beam. Therefore, components were produced in three different orientations (A, B and C) in order to verify the influence of the layers deposition on the mechanical properties and fracture micromechanisms, through the tensile tests, fatigue and tenacity of fracture and scanning electron microscopy (SEM). The samples were also subjected to a heat treatment to relieve residual stresses resulting from the manufacturing process and after analyzed through a optical microscopy and X-ray diffraction, to ascertain if there were changes in the microstructure or phase decomposition in relation to a sample without a heat treatment and at as manufactured condition. The construction orientation B and C have had better values in all mechanical tests when compared to the orientation A, revealing that had a loss of mechanical strength, except in the microhardness test, where the average values did not have large variations in the orientation of manufacturing. The sample as manufactured presented higher hardness values when compared to samples with treatment to relieve the residual stress, and this fact occurred due the precipitation of the B phase and the growth of the a phase in the material, which initially had a structure consisting of martensite hexagonal (a')
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Asllani, Engjell. "Analisi sperimentale della resistenza a fatica di provini ottenuti per Additive Manufacturing." Bachelor's thesis, Alma Mater Studiorum - Università di Bologna, 2018.
Find full textAbstract:
L’obbiettivo della mia tesi è la valutazione delle prestazioni a fatica di provini realizzati in Maraging Steel MS1 e PH1, prodotto da DMLS, prendendo in considerazione il loro processo produttivo.
L'argomento è stato affrontato sperimentalmente, studiando l'impatto del trattamento termico, della lavorazione meccanica e della pallinatura micro-shot sulla resistenza a fatica rispetto allo "stato costruito". I provini testati sono stati suddivisi in 3 lotti differenti caratterizzati da tipi diversi di composizione del materiale e trattamenti post-stampa.
Per valutare il comportamento a fatica sono stati inoltre considerati la rugosità superficiale, la dimensione del provino, la densità e la distorsione dei campioni causata dalle tensioni residue.
Per individuare la causa del cedimento sono state fotografate le superfici di frattura mediante l’uso di due microscopi.
I dati sperimentali ottenuti dalle prove vengono poi elaborati tramite la normativa ISO12107-2012 per trovare la curva di fatica S-N, sia usando un’interpolazione lineare che una quadratica per confrontarle in modo da identificare quale metodologia approssima meglio i dati. E' inoltre utilizzata la normativa Dixon tramite uno stair-caise per trovare la tensione limite di fatica.
Per questo studio in particolare sono stati usati tre set di provini e ogni set ha numerosità pari a 15.
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Kabbur, Nikhil. "Design and Manufacturing Guidelines for Additive Manufacturing of High Porosity Cellular Structures." University of Cincinnati / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1504878916930908.
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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.
Full textAbstract:
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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.
Full textAbstract:
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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Betti, Enrico <1984>. "Utilizzo in chirurgia ortognatica di dime di taglio per le osteotomie e placche di osteosintesi CAD-CAM stampate con tecnologia DMLS per l'osteotomia ed il riposizionamento mandibolare." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2019. http://amsdottorato.unibo.it/8976/1/PDF%20TESI%20DOTTORATO%20-%20BETTI.pdf.
Full textAbstract:
Obiettivo: lo scopo di questo studio è quello di valutare l’utilizzo di una metodica nuova per la chirurgia ortognatica. La metodica proposta prevede l’integrazione della medicina con le nuove tecnologie al fine di testare l’utilizzo di dime di taglio e placche di ostosintesi CAD-CAM per la osteotomia ed il riposizionamento mandibolare. Materiali e Metodi: lo studio
prende in considerazione 10 pazienti arruolati dal luglio 2017 al Maggio 2018, affetti da dismorfia dento scheletrica e sottoposti a chirurgia ortognatica bimascellare. Lo studio 3D dei paziente e la simulazione virtuale dell’intervento è stato eseguito con il software IPS Case Designer (KLS Martin, Germany). Sulla base della
programmazione virtuale sono state progettate e realizzate le guide di taglio e le placche di osteosintesi mandibolare CAD-CAM. Tutti i pazienti sono stati operati con approccio mandibolar-first, utilizzando il sistema individualizzato.
I dati post-operatori sono stati confrontati con quelli del planning virtuale al fine di valutare l’accuratezza della metodica. Risultati: l’accuratezza del riposizionamento mandibolare si è dimostrato soddisfacente e gli errori sono stati omogenei tra i casi.Objective: the aim of this study is to evaluate the use of a new method for orthognathic surgery. The proposed method involves the integration of medicine with new technologies in order to test the use of cutting guides and CAD-CAM ostosynthesis plates for osteotomy and mandibular repositioning. Materials and Methods: the study takes into consideration 10 patients enrolled from July 2017 to May 2018, suffering from skeletal dento dysmorphia and undergoing orthognathic surgery. The 3D patient study and the virtual simulation of the intervention was performed with the IPS Case Designer software (KLS Martin, Germany). Based on the Virtual programming has been designed and implemented cutting guides and CAD-CAM mandibular osteosynthesis plates. All patients were operated with a mandibolar-first approach, using the individualized system. Post-operative data were compared with those of virtual planning in order to evaluate the accuracy of the method. Results: the accuracy of the mandibular repositioning was satisfactory and the errors were homogeneous between the cases.
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Pereira, M. F. V. T., M. Williams, and Preez W. B. Du. "Characterization of metal powder based rapid prototyping components with respect to aluminium high pressure die casting process conditions." Journal for New Generation Sciences, Vol 8, Issue 2: Central University of Technology, Free State, Bloemfontein, 2010. http://hdl.handle.net/11462/563.
Full textAbstract:
Published ArticleThis paper is based on tests performed on die component specimens manufactured by EOS-DMLS (direct metal laser sintering) and LENS (laser engineered net shape) RP (rapid prototyping) technology platforms, as well as manufactured specimens machined out of preferred standard hot work steel DIN 1.2344. These specimens resemble typical components used in metal high pressure die casting tool sets. The specimens were subjected to a programme of cyclic immersion in molten aluminium alloy and cooling in water-based die release medium. The heat checking and soldering phenomena were analyzed through periodic inspections, monitoring crack formation and evidence of surface washout. At the end of the thermal tests, mechanical strength and hardness tests were performed to assess toughness and core resistance variations in relation to the initial conditions. Finally metallographic investigations were performed through optical microscopy on all the specimens considered. The outcomes of this research will be presented and used by the CSIR for further development and application of the assessed EOS-DMLS and LENS rapid prototyping technologies in rapid die manufacturing techniques and die design principles, including time and economic feasibility criteria to be applied when considering rapid die manufacture.
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Bastos, Jaqueline Silva [UNESP]. "Reparo ósseo em scaffolds de TI6AL4V sinterizados pela tecnologia de sinterização direta de metais a laser (DMLS) submetidos a tratamento de superfície associado à aplicação de ultrassom de baixa intensidade (LIPUS)." Universidade Estadual Paulista (UNESP), 2016. http://hdl.handle.net/11449/138130.
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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)
O objetivo desse estudo in vivo foi verificar a resposta óssea de scaffolds porosos revestidos processados pela técnica de Sinterização Direta de Metais a laser (DMLS) associado à terapia de ultrassom de baixa intensidade. Os scaffolds foram processados empregando a técnica DMLS e tratados termicamente a 1000°C por 24 horas. Três tipos de tratamento de superfície foram avaliados: Alcalino, biomimético e imobilização de alendronato de sódio. Para o tratamento alcalino, as amostras foram imersas na solução de NaOH (5M) a 60ºC por 24 horas. O tratamento biomimético consistiu na imersão dos scaffolds em solução SBF (SimulatedBodyFluid) enquanto a imobilização do alendronato foi realizada a partir da imersão dos scaffolds em uma solução formada por SBF e medicamento durante 5 dias. As superfícies dos scaffolds foram avaliadas para cada etapa empregando microscopia eletrônica de varredura (MEV) e análise por difração de raios-X. Os scaffolds foram implantados na tíbia direita de 85 ratos machos da raça wistar com idade média de 12 semanas. A microtomografia computadorizada (µCT) e análise histológica foram realizadas para avaliar o reparo ósseo no defeito. As micrografias das superfícies obtidas mostraram mudanças no aspecto da superfície e composição química de acordo com o tratamento. O tratamento biomimético promoveu o crescimento da apatita sobre a superfície enquanto a imobilização com alendronato suprimiu sua formação. As imagens obtidas na microtomografia mostraram elevado valor de densidade óssea para o último grupo. No entanto, análises histológicas mostraram a formação de cápsula fibrosa em torno dos scaffolds a qual foi minimizada usando ultrassom pulsado de baixa intensidade. No entanto, mais estudos precisam ser realizados para avaliar a influência da geometria dos scaffolds na incorporação de medicamentos.
The objective of this in vivo study was to verify the bone response of coated Ti6Al4V porous scaffolds processed by Direct Metal Laser Sintering (DMLS) technique associated to low intensity pulsed ultrasound therapy. Scaffolds were processed by using Direct Metal Laser Sintering technique (DMLS) and heat treated at 1000 °C for 24 hours. Three types of surface treatments were evaluated: alkaline, biomimetic and sodium alendronate immobilization. For alkaline treatment, samples were immersed in a NaOH (5M) solution at 60ºC for 24 hours. Biomimetic treatment consisted in the immersion of the scaffolds into Simulated Body Fluid solution while for sodium alendronato immobilization the scaffolds were immersed in the solution formed by SBF plus drug during 5 days. The scaffolds surfaces were evaluated after each step employing SEM (Scanning Electron Microscopy)and X-rays diffraction analysis(XRD). Scaffolds were implanted into right tibia of 85 male Wistar rats with average age of 12 weeks. X-rays micro-computed tomography (µCT) and histological analysis were carried out to evaluate the bone repair on the defect. Micrographs analysis showed that the aspect of the surfaces and chemical composition changed according treatment. Biomimetic treatment promoted the growth of the apatite on the surface; in contrast the immobilization of alendronate suppressed apatite formation. Micro CT images showed higher value of bone density for the last group. However, histological analysis showed the formation of encapsulation fibrous around the scaffolds. This formation was minimized by using low intensity pulsed ultrasound technique, however, more studies can be carried out to evaluate the influence of scaffolds geometry in the drug incorporation.
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Bastos, Jaqueline Silva. "Reparo ósseo em Scaffolds de Ti6Al4V sinterizados pela tecnologia de Sinterização Direta de Metais a Laser (DMLS) submetidos a tratamento de superfície associado à aplicação de ultrassom de baixa intensidade (LIPUS) /." Guaratinguetá, 2016. http://hdl.handle.net/11449/138130.
Full textAbstract:
Orientadora: Ana Paula Rosifini Alves ClaroBanca: André Luiz Jardini Munhoz
Banca: Ricardo Tadeu Lopes
Banca: Orivaldo Lopes da Silva
Banca: Ana Lia Anbinder
Resumo: O objetivo desse estudo in vivo foi verificar a resposta óssea de scaffolds porosos revestidos processados pela técnica de Sinterização Direta de Metais a laser (DMLS) associado à terapia de ultrassom de baixa intensidade. Os scaffolds foram processados empregando a técnica DMLS e tratados termicamente a 1000°C por 24 horas. Três tipos de tratamento de superfície foram avaliados: Alcalino, biomimético e imobilização de alendronato de sódio. Para o tratamento alcalino, as amostras foram imersas na solução de NaOH (5M) a 60ºC por 24 horas. O tratamento biomimético consistiu na imersão dos scaffolds em solução SBF (SimulatedBodyFluid) enquanto a imobilização do alendronato foi realizada a partir da imersão dos scaffolds em uma solução formada por SBF e medicamento durante 5 dias. As superfícies dos scaffolds foram avaliadas para cada etapa empregando microscopia eletrônica de varredura (MEV) e análise por difração de raios-X. Os scaffolds foram implantados na tíbia direita de 85 ratos machos da raça wistar com idade média de 12 semanas. A microtomografia computadorizada (µCT) e análise histológica foram realizadas para avaliar o reparo ósseo no defeito. As micrografias das superfícies obtidas mostraram mudanças no aspecto da superfície e composição química de acordo com o tratamento. O tratamento biomimético promoveu o crescimento da apatita sobre a superfície enquanto a imobilização com alendronato suprimiu sua formação. As imagens obtidas na microtomografia mostraram elevado valor de densidade óssea para o último grupo. No entanto, análises histológicas mostraram a formação de cápsula fibrosa em torno dos scaffolds a qual foi minimizada usando ultrassom pulsado de baixa intensidade. No entanto, mais estudos precisam ser realizados para avaliar a influência da geometria dos scaffolds na incorporação de medicamentos
Abstract: The objective of this in vivo study was to verify the bone response of coated Ti6Al4V porous scaffolds processed by Direct Metal Laser Sintering (DMLS) technique associated to low intensity pulsed ultrasound therapy. Scaffolds were processed by using Direct Metal Laser Sintering technique (DMLS) and heat treated at 1000 °C for 24 hours. Three types of surface treatments were evaluated: alkaline, biomimetic and sodium alendronate immobilization. For alkaline treatment, samples were immersed in a NaOH (5M) solution at 60ºC for 24 hours. Biomimetic treatment consisted in the immersion of the scaffolds into Simulated Body Fluid solution while for sodium alendronato immobilization the scaffolds were immersed in the solution formed by SBF plus drug during 5 days. The scaffolds surfaces were evaluated after each step employing SEM (Scanning Electron Microscopy)and X-rays diffraction analysis(XRD). Scaffolds were implanted into right tibia of 85 male Wistar rats with average age of 12 weeks. X-rays micro-computed tomography (µCT) and histological analysis were carried out to evaluate the bone repair on the defect. Micrographs analysis showed that the aspect of the surfaces and chemical composition changed according treatment. Biomimetic treatment promoted the growth of the apatite on the surface; in contrast the immobilization of alendronate suppressed apatite formation. Micro CT images showed higher value of bone density for the last group. However, histological analysis showed the formation of encapsulation fibrous around the scaffolds. This formation was minimized by using low intensity pulsed ultrasound technique, however, more studies can be carried out to evaluate the influence of scaffolds geometry in the drug incorporation
Doutor
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Biancoli, Giacomo. "Additive manufacturing: ricerca sui principali fattori che influenzano il comportamento a fatica." Bachelor's thesis, Alma Mater Studiorum - Università di Bologna, 2017.
Find full textAbstract:
Gli obiettivi di questo elaborato sono fondamentalmente caratterizzare dei provini (realizzati in Maraging steel e Stainless steel attraverso DMLS) a fatica oligociclica, distinguerne il comportamento in base all'orientamento di costruzione ed analizzare tutti i fattori che possono influenzare la vita di un provino. Esaminando questa caratterizzazione, è possibile avvicinarci all'idea di impiegare direttamente nel processo produttivo pezzi realizzati e montati direttamente in produzione.
Dopo una breve introduzione sull'additive manufacturing e sul suo sviluppo nel corso degli anni con le varie tecnologie di stampa (analizzandone i relativi vantaggi e svantaggi), vengono accennati i costi della tecnologia di cui ci occuperemo. Dopo una prima introduzione sui materiali impiegati, vengono introdotti i provini protagonisti dell'esperienza, la macchina utilizzata e lo svolgimento della prova. Segue un'illustrazione dei vari orientamenti di costruzione del provino e di come variano le proprietà meccaniche quando sottoposto a fatica. In seguito sono analizzate le tensioni residue sui provini (post sinterizzazione) ed i trattamenti eseguibili, presentando la loro influenza sulle proprietà meccaniche. Infine è analizzata la meccanica della frattura, in particolare la propagazione della cricca. Tradizionalmente, si è sempre analizzato il comportamento dei provini secondo i due orientamenti classici, orizzontale e verticale: in questo elaborato verrà presentato, per quanto reperibile dai documenti scientifici, anche il loro comportamento a 45°. Grazie a queste nuove caratterizzazioni, è sempre più possibile analizzare a pieno il comportamento delle proprietà meccaniche di ogni prodotto realizzato mediante questa tecnologia, facendo riferimento (nel caso di analisi di forme geometriche complesse) ai modelli più semplici già analizzati.
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Palmer, Andrew. "The Design and Development of an Additive Fabrication Process and Material Selection Tool." Master's thesis, University of Central Florida, 2009. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/3635.
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In the Manufacturing Industry there is a subset of technologies referred to as Rapid Technologies which are those technologies that create the ability to compress the time to market for new products under development . Of this subset, Additive Fabrication (AF), or more commonly known as Rapid Prototyping (RP), acquires much attention due to its unique and futuristic approach to the production of physical parts directly from 3D CAD data, CT or MRI scans, or data from laser scanning systems by utilizing various techniques to consecutively generate cross-sectional layers of a given thickness upon the previous layer to form 3D objects. While Rapid Prototyping is the most common name for the production technology it is also referred to as Additive Manufacturing, Layer Based Manufacturing, Direct Digital Manufacturing, Free-Form Fabrication, and 3-Dimensional Printing. With over 35 manufacturers of Additive Fabrication equipment in 2006 , the selection of an AF process and material for a specific application can become a significant task, especially for those with little or no technical experience with the technology and to add to this challenge, many of the various processes have multiple material options to select from . This research was carried out in order to design and construct a system that would allow a person, regardless of their level of technical knowledge, to quickly and easily filter through the large number of Additive Fabrication processes and their associated materials in order to find the most appropriate processes and material options to create physical reproductions of any part. The selection methodology used in this paper is a collection of assumptions and rules taken from the author's viewpoint of how, in real world terms, the selection process generally takes place between a consumer and a service provider. The methodology uses those assumptions in conjunction with a set of expert based rules to direct the user to a best set of qualifying processes and materials suited for their application based on as many or as few input fields the user may be able to complete.M.S.
Department of Industrial Engineering and Management Systems
Engineering and Computer Science
Industrial Engineering MS
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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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Hossain, Mohammad Arif. "Sweeping Jet Film Cooling." The Ohio State University, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=osu1586462423029754.
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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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Deml, Christoph. "Analyse und Modellierung des DMOS-Transistors." [S.l.] : [s.n.], 2003. http://deposit.ddb.de/cgi-bin/dokserv?idn=969618816.
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Deml, Christoph Hoffmann Kurt. "Analyse und Modellierung des DMOS-Transistors." Neubiberg Universitätsbibliothek der Universität der Bundeswehr, 2008. http://d-nb.info/998614890/34.
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Faigle, Christopher Tyler. "DMS-Splines and radiosity." Thesis, University of Cambridge, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.624727.
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Hung, Merit Y. (Merit Yi). "Double diffused (DMOS) FETs for analog applications." Thesis, Massachusetts Institute of Technology, 1990. http://hdl.handle.net/1721.1/13698.
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Angel, Mattias, and Albert Berggren. "Regionala DMOs marknadsföring och sociala mediers påverkan." Thesis, Mittuniversitetet, Institutionen för ekonomi, geografi, juridik och turism, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:miun:diva-39247.
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Destination management organizations (DMOs) är organisationer som ofta är uppbyggda av två eller flera medlemsorganisationer. En huvudsaklig uppgift som DMOs har är att marknadsföra destinationen. Sociala medier är något som förändrat sättet många organisationer bedriver sin marknadsföring på. Kommunikationen har gått från statisk envägs, alltså från den som producerar budskap till den som konsumerar, till mer dynamisk tvåvägskommunikation där relationer, samarbete och kommunikation mellan de två parterna kommit att bli allt viktigare. Vi undersöker i den här uppsatsen hur svenska regionala DMOs använder sig av sociala medier i sitt marknadsföringsarbete. Empirin har samlats in genom kvalitativa, semistrukturerade intervjuer med personer som arbetar med marknadsföring vid fyra svenska regionala DMOs. Detta har kombinerats med en analys av berörda DMOs respektive sidor på de sociala medierna Facebook och Instagram. Resultaten visar att de olika organisationerna har både likheter och skillnader i hur de operativt och strategiskt använder sig av sociala medier i marknadsföringssyfte.Destination management organizations (DMOs) are usually structured by two or more member-organizations. One of the main tasks for a DMO is to market the destination. Social medias have changed the way a lot of organizations manages their marketing. Communication has gone from a static one directional, from the producer to the consumer, to a more dynamic two-way communication where the interaction between the two parts has become more important. In this paper we examine how swedish regional DMOs use social medias in their marketing. The empirical data has been gathered by qualitative semi-structured interviews with persons who work with marketing at four different swedish regional DMOs. This has been combined with analysis of the concerned DMOs social media pages on Facebook and Instagram. The results show that the different organizations have both similarities and differences in their strategic and operative use of social media in marketing efforts.
2020-06-08
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Zupac, Dragan. "Radiation-induced mobility degradation in DMOS transistors." Diss., The University of Arizona, 1993. http://hdl.handle.net/10150/186456.
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Effects of radiation-induced interface-trapped charge and oxide-trapped charge on the inversion-layer carrier mobility in double-diffused metal-oxide-semiconductor (DMOS) power transistors are investigated. Interface-trapped charge is more effective in scattering inversion-layer carriers than oxide-trapped charge. However, the effects of oxide-trapped charge must be taken into account in order to properly describe the mobility behavior. An effective approach to detecting effects of oxide-trapped charge and separating these effects from effects of interface-trapped charge is demonstrated. Detection is based on analyzing mobility data sets which have different functional relationships between the two trapped charge components. These relationships may be linear or nonlinear. Separation of effects of oxide-trapped charge and interface-trapped charge is possible only if these two trapped charge components are not linearly dependent. A significant contribution of oxide-trapped charge to mobility degradation is demonstrated and quantified. Effects of oxide-trapped charge may be dominant in non-hardened DMOS transistors irradiated at relatively high dose rates. In addition, DMOS devices have been irradiated at room temperature and mobility measurements performed at room temperature and at 77 K to analyze mobility degradation due to the same density of radiation-induced defects at these two different temperatures. Radiation-induced mobility degradation is more pronounced at 77 K than at room temperature, due to increased relative importance of Coulomb scattering from trapped charge when phonon scattering is significantly reduced. Effects of oxide-trapped charge on mobility are more pronounced at cryogenic temperatures than at room temperature.
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Giske, Mats Andreas. "DML in VIDEO-CONFERENCING APPLICATIONS." Thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for elektronikk og telekommunikasjon, 2012. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-19416.
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Today's audio in video-conference rooms do not in general have high quality audio standards.Most of the set-ups are PC-Speakers mounted on the wall, with a microphone on the table. With this, strong room modes are often excited from the speakers. When speaking to someone which also have bad equipment, the speech-intelligibility can be really bad. One solution presented with this Master thesis is to improve the loudspeaker set-up by mounting a DML(Distributed Mode Loudspeaker) above and parallel to the conference table. The DML will then radiate sound on both sides of the table equally in opposite phase, like a dipole. This will also minimize sound-radiation to the ceiling and the office-table.The DML is designed and modified from a loudspeaker originally deigned by the loudspeaker-company e-Scape. The Plexiglas panel, made out of an Acrylic material, has exciters mounted on the panel. After testing different combinations of two and three exciters in an anechoic chamber, the polar frequency response of the DML with only one exciter had a much better response than the other combinations.The idea of mounting the DML over the table is that the audience will get closer to the sound source, and room-effects will be very small compared to the direct signal. This should give a much better speech-intelligibility of the perceived sound signal compared to existing solutions. Subjective tests show that the majority of the participants preferred the DML rather than the PC-Speaker in all areas; a more natural sound, more closeness to the one speaking and better speech-intelligibility.One problem, which is seen on the measurements and feedback from the participants on the subjective test, is a low SPL(Sound Pressure Level) in the low frequency area. Under 100Hz the magnitude of the DML is reduced, compared to the response of ordinary monopole speakers. From this frequency area one can also see some dipole effects from the results, which gives us good qualities such as less radiation to the ceiling and the office table.
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Schepp, Oliver. "Simulations- und Meßmethoden zur Bestimmung der Temperatur von LeistungsMOSFETs /." Düsseldorf : VDI-Verl, 1998. http://www.gbv.de/dms/bs/toc/251116484.pdf.
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Adam, Banafscheh. "DMPS und Dimercaprol in der Therapie der akuten Arsenintoxikation." [S.l.] : [s.n.], 2004. http://deposit.ddb.de/cgi-bin/dokserv?idn=972308113.
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Adolph, Daniela. "Zunahme der renalen Quecksilberausscheidung durch DMPS bei chronischer Quecksilbervergiftung." Diss., lmu, 2007. http://nbn-resolving.de/urn:nbn:de:bvb:19-79299.
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Lundén, Jenny. "Atmospheric DMS in the High Arctic." Stockholm : Department of Meteorology, Stockholm University, 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-38178.
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Diss. (sammanfattning) Stockholm : Stockholms universitet, 2010.At the time of the doctoral defense the following papers were unpublished and had a status as follows: Paper 1: Manuscript. Paper 2: Manuscript. Paper 4: Manuscript.
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Lundén, Jenny. "Atmospheric DMS in the High Arctic." Doctoral thesis, Stockholms universitet, Meteorologiska institutionen (MISU), 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-38178.
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During the Arctic summer when the anthropogenic influence is limited, the natural marine source of sulfur in the form of gas-phase dimethyl sulfide viz. DMS(g), is of great importance for cloud formation. The harsh environment of the Arctic makes it difficult to perform in situ measurements of DMS(g) and hence regional model simulations can serve as a complement to increase our understanding of DMS related processes in the Arctic. In this thesis a regional scale meteorological forecast model, extended with DMS(g) calculations, is used to provide a consistent three-dimensional time evolving picture of DMS(g) over the pack-ice region. The analysis focus on meteorological aspects on the horizontal and vertical distribution of DMS(g). Our results show that the amount of DMS(g) over an oceanic source region alone does not determine concentration found over the pack-ice, the prevailing wind also exerts a large influence on the horizontal DMS(g) distribution. The modeled DMS(g) concentrations are advected in plumes in over the pack-ice, which, in combination with the photo-chemical decay, explain the large observed temporal variability of DMS(g) over the pack-ice. The modeled vertical structure show episodes with DMS(g) maxima well above the local boundary layer. Also shown is that DMS(g) maxima can be formed adjacent to frontal zones. In the presence of turbulence DMS(g) can be mixed downwards into the local boundary layer and aid growth to local particles and hence contribute to cloud formation in the boundary layer.At the time of the doctoral defense the following papers were unpublished and had a status as follows: Paper 1: Manuscript. Paper 2: Manuscript. Paper 4: Manuscript.
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Elbashiri, Ali. "Distributed Marking System (DMS), cORBA implementation." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape7/PQDD_0007/MQ45367.pdf.
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Žáček, Jan. "Pilotní zavádění DMS v bankovním prostředí." Master's thesis, Vysoká škola ekonomická v Praze, 2014. http://www.nusl.cz/ntk/nusl-202082.
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The diploma thesis focuses on the analysis of a document management system (DMS) pilot implementation in the environment of a Czech bank. The thesis is divided into three parts; the first part is theoretical and remaining two parts are practical (analytical). The theoretical part is devoted to summarization of basic theoretical knowledge in the field of DMS and in a pilot deployment of information systems. The second part describes the EMC xCP 2.1 platform and evaluates its advantages and disadvantages compared to competing products. The third part describes the technological implementation and deployment of a new DMS pilot solution in a bank. Further it analyzes and describes the follow-up activities and related projects that increase the DMS usability in a real business applications. The diploma thesis concurrently focuses on the business requirements analysis including constrains of a new solution deployment, as well as the DMS technological aspects description and the solution design. The author of this thesis has been working as an analyst in the IT company and has been in a long-term cooperation with the DMS team in the bank. The motivation for choosing this topic is to make a summary and clarification of knowledge gained on projects in the the bank and to take an advantage of it in the future cooperation.
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Feumi-Jantou, Charles. "Rôle du récepteur CX3CR1 dans la dégénérescence maculaire liée à l'âge (DMLA)." Thesis, Paris 5, 2012. http://www.theses.fr/2012PA05T066.
Full textAbstract:
La DMLA est parmi les pathologies du vieillissement oculaire qui posent un réel problème de santé publique.Elle affecte plus de 50% de la population de plus de 80 ans. On distingue un stade asymptomatique marqué par laprésence de tâches blanchâtres, les Drusen et un stade symptomatique compliqué par une baisse de la vision liée soit àun phénomène de néovascularisation choroïdienne maculaire dite DMLA exsudative soit à une dégénérescence desphotorécepteurs s’accompagnant d’une atrophie du tissu choroïdien et rétinien dite DMLA atrophique. Les moyensthérapeutiques sont limités aux complications en rapport avec la néovascularisation. La physiopathogénie de cetteaffection est encore mal connue. Parmi les facteurs de risque, on connaît l’âge, le tabac, les facteurs nutritionnels et desfacteurs génétiques. Les chimiokines, cytokines chimio-attractantes recrutant des sous-populations leucocytaires de lacirculation générale vers les sites inflammatoires sont impliquées dans la physiopathogénie de la DMLA. La mutationde CX3CR1, récepteur de la chimiokine fractalkine est associée à une augmentation du risque de DMLA. Notre travail aété d’étudier le rôle du récepteur de la fractalkine, CX3CR1 dans la DMLA. Nous avons observé une augmentation del’incidence de la DMLA en cas d’homozygotie pour l’allèle M280 du récepteur CX3CR1 chez l’homme. Au niveautissulaire, notre étude a mis en évidence l’expression du récepteur CX3CR1 par les cellules microgliales rétinienneschez l’homme comme chez la souris. Nous avons constaté chez l’homme que les cellules microgliales migraient versl’espace sous rétinien et s’accumulaient au site de la dégénérescence rétinienne et de la néovascularisation choroïdienneDans le modèle de souris CX3CR1-/-, les cellules microgliales s’accumulent dans l’espace sous rétinien sous différentesconditions comme la sénescence, la photocoagulation rétinienne au laser Argon et l’illumination rétinienne (sourisCX3CR1-/- albinos). L’accumulation sous rétinienne des cellules microgliales avec l’âge prend l’aspect des Drusen aufond d’oeil chez les souris et cette accumulation CX3CR1-dépendante exacerbe la néovascularisation choroïdienneinduite expérimentalement. Il s’agit de signes cardinaux observés au cours de la DMLA à travers de nouveauxmécanismes physiopathogéniques. De nouvelles pistes thérapeutiques vont être susceptibles d’émerger à partir de cesnouvelles cibles potentiellesAge-related macular degeneration (AMD) is the leading cause of vision loss in elderly people in theindustrialized countries. Early AMD is characterized by yellowish white dots called drusen, clinically visible withfunduscopy. There are two clinical forms of late AMD: the fast progressive “wet” form defined by choroidalneovascularisation, responsible for the most part of legal blindness in AMD, and the more slowly progressive “atrophic”form characterized by RPE atrophy, photoreceptor degeneration and choroidal involution. “Wet” AMD is the onlytreated form Epidemiological studies have helped to identify key factors in its pathogenesis. Age, family history andgenetic are the principal predisposing factors. Over the past few years, numerous studies have focused on the role ofchemotactic cytokines, also known as chemokines and their receptors. Retinal microglial cells (MC) express CX3CR1.The role of retinal microglial cells (MC) in age-related macular degeneration (AMD) is unclear. This study shows thatall retinal MC express the chemokine receptor CX3CR1 and that homozygosity for the CX3CR1 M280 allele, which isassociated with impaired cell migration, increases the risk of AMD. We found that in humans with AMD, MCaccumulated in the subretinal space at sites of retinal degeneration and of choroidal neovascularization. In CX3CR1-deficient mice, MC accumulated subretinally with age and albino background and after laser impact preceding retinaldegeneration. The appearance of lipid-bloated subretinal MC is drusen-like on funduscopy of senescent mice, andCX3CR1-dependent MC accumulation is associated with an exacerbation of experimental choroidal neovascularization.These results show that CX3CR1-dependent accumulation of subretinal MC evokes cardinal features of AMD. Thesefindings as new pathogenic process might be useful for new therapies development