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Bergmann, Jana, Hans Dörmann, and Rüdiger Lange. "Interpreting process data of wet pressing process: Part 1: Theoretical approach." Sage, 2016. https://tud.qucosa.de/id/qucosa%3A35793.
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The wet pressing process represents a new production method for carbon fibre-reinforced plastics components. Due to the low cycle times, it is suitable for use in the automotive industry. Therefore, a sufficient degree of industrialisation needs to be achieved, which is characterised by a stable process. The knowledge about relevant process parameters, their interactions, and influence on the part quality builds the basis of an economic process. This is a major challenge, since in the early stage of process development the available amount of recorded process data is small and the data sets are not complete. As the implementation of time-, material-, and cost-intensive experiments represents no acceptable alternative, a theoretical approach is chosen. This article describes a theoretical procedure to define the critical factors of the wet pressing process with significantly less resource input.
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Rai, Sweta. "Identification of factors influencing the valve seat pressing process." Thesis, KTH, Industriell produktion, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-215974.
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Bergmann, Jana, Hans Dörmann, and Rüdiger Lange. "Interpreting process data of wet pressing process: Part 2: Verification with real values." Sage, 2016. https://tud.qucosa.de/id/qucosa%3A35791.
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For the analysis of the wet pressing process, which was presented in the first part of this paper, a theoretical approach was chosen. This enabled the pre-definition of three quality-related priorities which now will be considered in detail in the second part. For further analysis, real process data, recorded in an early phase of the process implementation, are used. The challenge is that in this process status, the availability of data is limited or the data sets are incomplete. Supported by the theoretical approach, an easier interpretation of the process data, and in case of ambiguous issues, an accelerated decision making is expected. The objective is to show that this combination is suitable for the process analysis in an early production phase.
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Wolfe, Robert Anthony. "The design of tooling for the vertical isostatic dust pressing process." Thesis, Staffordshire University, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.402741.
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Milani, Mauro. "Optimization of the pressing process of triangular shaped cutting tool inserts." Thesis, Linnéuniversitetet, Institutionen för maskinteknik (MT), 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:lnu:diva-58282.
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Pressing of metallic powders is a manufacturing process widely investigated in the research field and in the industry. This thesis project is focused on optimizing the pressing process of cemented carbide powder utilized for the production of triangular shaped cutting tool inserts. In particular, the filling of powder into the die cavity was investigated with respect to different pressing parameters. The aim of the project was to obtain a uniform density distribution of the powder into the die cavity, and hence to reduce the variation of the height of the insert obtaining more precise dimension of the latter. The tests were carried out at the Sandvik Coromant production department which is the creator of the project. The optimization of the pressing process was performed according to the Design of experiments theory. The dynamic of the sintering process was also investigated. The results showed a significant improvement in the filling of the die cavity and a significant decrease of the variation of the height of the inserts. The new insert obtained has more precise dimensions and is able to meet the more demanding requirements of the customers. The results achieved are directly applicable to a larger number of products, and indicate the direction to follow for further development of the manufacturing process.
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Souza, NÃgila Freitas. "Process for obtaining nanocellulose fiber from the pressing the palm mesocarp." Universidade Federal do CearÃ, 2014. http://www.teses.ufc.br/tde_busca/arquivo.php?codArquivo=12142.
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CoordenaÃÃo de AperfeiÃoamento de Pessoal de NÃvel SuperiorThe present study aimed to extract nanocellulose crystalline (NCC) and nanofibrillated (NCF), and recover of lignin from oil palm mesocarpfiber (also known as palm pressed fiber). Initially, the fibers were subjected to pulping acetosolv followed by bleaching with peroxide in basic medium. The crude fiber, bleached and post acetosolv were characterized physically, chemically and morphologically. To obtain the NCC a 23 factorial design was used. NCF was obtained by combinations of the number and size of steps chamber microfluidizer. The nanocelulose obtained by acid hydrolysis (NCC) and microfluidization (NCF) was characterized by X-ray diffraction (XRD), zeta potential and particle size. According to the results, the pre-treatments were efficient, removing a significant amount of amorphous components, promoting a greater exposure of the pulp. The lignin rich fraction, called black liquor, had a yield of 62 % compared to the lignin initially present. Nanocellulose suspensions obtained showed typical gelatinous appearance and zeta potential of -26.6 mV and -40.6 mV, which configures stability.The crystallinity index of cellulose polymorphs I and II for nanocelulose crystal obtained by pre-treatment 1 was 65%, and for the other nanofibrilada nanocrystals obtained from the pre-treatment 2 were crystallinity of 70 and 61%, respectively. The nanostructures obtained still showed good thermal stability, demonstrating a greater microfibrillated nanocelulose to 267 Â C to 250 Â C the crystal. Furthermore, nanostructures were observed with typical cellulose lengths (L) between 172-404 nm and a diameter (D) lying between 5 and 12 nm, which reproduces aspect ratios (L / D) as high as 39. This demonstrates that the nanocelulose produced can be displayed as reinforcement in polymer matrices, among other applications.
O presente trabalho teve por objetivo extrair nanocelulose, cristalina (NCC) e microfibrilada (NCF), e recuperar lignina de fibras da prensagem do mesocarpo do dendÃ. Inicialmente, as fibras foram submetidas adois tipos de prÃ-tratamentos (1. mercerizaÃÃo seguida de branqueamento e 2. polpaÃÃo acetosolv seguida de branqueamento). As fibras brutas, pÃs acetosolv e branqueadas foram caracterizadas fÃsica, quÃmica e morfologicamente. Para obtenÃÃo da NCC, foi utilizado um planejamento fatorial 23, enquanto a NCF foi obtida por meio de combinaÃÃes de nÃmero de passos e tamanho de cÃmara do microfluidizador de alta pressÃo. As nanoceluloses obtidas por hidrÃlise Ãcida (NCC) e por microfluidizaÃÃo (NCF) foram caracterizadas por difraÃÃo de raio X (DRX), potencial zeta e anÃlise termogravimÃtrica (TGA). De acordo com os resultados, os prÃ-tratamentos foram eficientes, removendo quantidade significativa de componentes amorfos, promovendo uma maior exposiÃÃo da celulose e um consequente aumento do Ãndice de cristalinidade. A fraÃÃo rica em lignina, denominada licor negro, apresentou rendimento de 62% em relaÃÃo ao conteÃdo de lignina inicialmente presente. As suspensÃes de nanocelulose obtidas apresentaram aspecto gelatinoso tÃpico e potencial zeta variando de -26,6 mV a -40,6 mV, o que configura estabilidade. Os Ãndices de cristalinidade dos polimorfos de celulose I e II, para nanocelulose cristalina obtida atravÃs do prÃ-tratamento 1 foi de 65%, quanto aos outros nanocristais e nanofibrilada obtidas do prÃ-tratamento 2 apresentaram cristalinidade de 70 e 61%, respectivamente. As nanoestruturas obtidas apresentaram ainda boa estabilidade tÃrmica, demostrando-se maior para a nanocelulose microfibrilada, 267 ÂC contra 250ÂC para as cristalinas. Foram observadas, ainda, nanoestruturas de celulose tÃpicas com comprimentos (L) entre 172 nm a 404 nm e diÃmetros (D) situados entre de 5 nm e 12 nm, o que reproduziu razÃes de aspecto (L/D) tÃo altas quanto 39. Isso demonstra que as nanocelulose produzidas podem ser indicadas como reforÃo em matrizes polimÃricas, dentre outras aplicaÃÃes.
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Zombori, Balazs Gergely. "Modeling the Transient Effects during the Hot-Pressing of Wood-Based Composites." Diss., Virginia Tech, 2001. http://hdl.handle.net/10919/27299.
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A numerical model based on fundamental engineering principles was developed and validated to establish a relationship between process parameters and the final properties of woodbased composite boards. The model simulates the mat formation, then compresses the reconstituted mat to its final thickness in a virtual press. The number of interacting variables during the hot-compression process is prohibitively large to assess a wide variety of data by experimental means. Therefore, the main advantage of the model based approach that the effect of the hot-compression parameters on the final properties of wood-based composite boards can be monitored without extensive experimentation.
The mat formation part of the model is based on the Monte Carlo simulation technique to reproduce the spatial structure of the mat. The dimensions and the density of each flake are considered as random variables in the model, which follow certain probability density distributions. The parameters of these distributions are derived from data collected on industrial flakes by using an image analysis technique. The model can simulate the structure of a threelayer oriented strandboard (OSB) mat as well as the structure of random fiber networks. A grid is superimposed on the simulated mat and the number of flakes, the thickness, and the density of the mat at each grid point are computed. Additionally, the model predicts the change in several void volume fractions within the mat and the contact area between the flakes during consolidation. The void volume fractions are directly related to the physical properties of the mat, such as thermal conductivity, diffusivity, and permeability, and the contact area is an indicator of the effectively bonded area within the mat.
The heat and mass transfer part of the model predicts the change of air content, moisture content, and temperature at designated mesh points in the cross section of the mat during the hotcompression. The water content is subdivided into vapor and bound water components. The free water component is not considered in the model due to the low (typically 6-7 %) initial moisture content of the flakes. The gas phase (air and vapor) moves by bulk flow and diffusion, while the bound water only moves by diffusion across the mat. The heat flow occurs by conduction and convection. The spatial derivatives of the resulting coupled partial differential equations are discretized by finite differences. The resulting ordinary differential equation in time is solved by a differential-algebraic system solver (DDASSL). The internal environment within the mat can be predicted among different initial and boundary conditions by this part of the hot-compression model.
In the next phase of the research, the viscoelastic (time, temperature, and moisture dependent) response of the flakes was modeled using the time-temperature-moisture superposition principle of polymers. A master curve was created from data available in the literature, which describes the changing relaxation modulus of the flakes as a function of moisture and temperature at different locations in the mat. Then the flake mat was compressed in a virtual press. The stress-strain response is highly nonlinear due to the cellular structure of the mat. Hooke's Law was modified with a nonlinear strain function to account for the behavior of the flake mat in transverse compression. This part of the model gives insight into the vertical density profile formation through the thickness of the mat.
Laboratory boards were produced to validate the model. A split-plot experimental design, with three different initial mat moisture contents (5, 8.5, 12 %), three final densities (609, 641, 673 kg êm3 or 38, 40, 42 lb ê ft3), two press platen temperatures (150, 200 °C), and three different press closing times (40, 60, 80 s) was applied to investigate the effect of production parameters on the internal mat conditions and the formation of the vertical density profile. The temperature and gas pressure at six locations in the mat, and the resultant density profiles of the laboratory boards, were measured. Adequate agreement was found between the model predicted and the experimentally measured temperature, pressure, and vertical density profiles.
The complete model uses pressing parameters (press platen temperature, press schedule) and mat properties (flake dimensions and orientation, density distribution, initial moisture content and temperature) to predict the resulting internal conditions and vertical density profile formation within the compressed board. The density profile is related to all the relevant mechanical properties (bending strength, modulus of elasticity, internal bond strength) of the final board. The model can assist in the optimization of the parameters for hot-pressing woodbased composites and improve the performance of the final panel.Ph. D.
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Diem, Matthew M. "Development of a combined hot isostatic pressing and solution heat-treat process for the cost effective densification of critical aluminum castings." Link to electronic thesis, 2003. http://www.wpi.edu/Pubs/ETD/Available/etd-0107103-162146.
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Siegl, Pavel. "Optimalizace procesu lakování." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2008. http://www.nusl.cz/ntk/nusl-227955.
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The diploma is focused on optimizing of rating during the process of painting by means of experimental methods and statistic analysis. Description of the study of the present state of painting process, result analysis and the project of optimal pre-set in practice.
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Sonberger, Vít. "Volba a optimalizace řezných podmínek pro progresivní výrobní technologii zalomeného hřídele." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2015. http://www.nusl.cz/ntk/nusl-231104.
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This thesis is focused on proposal of production process of assembled crankshaft. It consists of choice of tools, data selection and optimisation for manufacture of individual components and for the assembly. In the assembly are also calculated important parameters for pressing components. Selected cutting conditions are experimentally verified.
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Тесличко, Іван Андрійович, Святослав Юрійович Хабаль, Ivan Teslychko, and Sviatoslav Khabal. "Автоматизація технологічного процесу вібропресування фасадної плитки (комплексна тема)." Bachelor's thesis, Тернопільський національний технічний університет ім. І. Пулюя, Факультет прикладних інформаційних технологій та електроінженерії, Кафедра автоматизації технологічних процесів і виробництв, 2021. http://elartu.tntu.edu.ua/handle/lib/35499.
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Робота виконана на кафедрі автоматизації технологічних процесів і виробництв факультету прикладних інформаційних технологій та електроінженерії Тернопільського національного технічного університету імені Івана Пулюя Міністерства освіти і науки України. Захист відбудеться «25» червня 2021 р. о 9.00 год. на засіданні екзаменаційної комісії №21 у Тернопільському національному технічному університеті імені Івана ПулюяВ даній кваліфікаційній роботі автоматизовано технологічний процес пресування керамічної та бетонної плитки. Описано технологічні процеси виготовлення бетонних виробів, а також конструкцію складових частин напівавтомата що реалізує ці процеси. Зокрема розроблено креслення автоматизованої установки для вібпропресування плитки, описано роботу її складових частин, монтаж, регулювання, налагодження і пуск, а також розроблено дозатор для точного дозування сипучих матеріалів. Розраховано дозатор, обмотку магнітопроводу віброзбудників, блок живлення, стабілізатор напруги, випрямляч мостової схеми. Розроблена у кваліфікаційній роботі установка дозволяє виготовляти плитку з глини, бетону, гіпсового каменю та інших будівельних матеріалів методом імпульсного пресування.
In this qualification work the technological process of pressing ceramic and concrete tiles is automated. Technological processes of production of concrete products, and also a design of components of the semiautomatic device realizing these processes are described. In particular, the drawing of the automated installation for vibropressing of a tile is developed, the work of its components, installation, adjustment, adjustment and start-up is described, and also the batcher for exact dosing of loose materials is developed. The batcher, the winding of the magnetic circuit of the vibrators, the power supply, the voltage stabilizer, the rectifier of the bridge circuit are calculated. The installation developed in qualification work allows to make a tile from clay, concrete, gypsum stone and other building materials by a method of pulse pressing.
Вступ 6 1 Аналітична частина 9 1.1 Методи обробки сировини для виготовлення плитки з глини та бетону 9 1.2 Методи ущільнення сировини для виготовлення плитки 13 2 Проєктна частина 15 2.1 Формування компонентів бетону 15 2.2 Технічний аналіз якості бетону 22 2.3 Технологія виготовлення бетонних сумішей 33 2.4 Технологія виготовлення бетонних виробів 35 2.5 Технічні характеристики установки 44 2.6 Конструкція і робота пресової установки та її складових частин 46 2.7 Опис конструкції модуля дозатора 54 2.8 Розрахунок дозатора 56 2.9 Опис роботи схеми керування 68 2.10 Розрахунок блока живлення 75 2.11 Алгоритм і циклограма роботи установки 83 3 Спеціальна частина 85 4 Безпека життєдіяльності, основи охорони праці 96 4.1 Методи очищення повітря на дільниці цеху від шкідливих виділень 96 4.2 Розрахунок захисного заземлюючого пристрою для обладнання дільниці цеху 99 4.3 Підвищення стійкості роботи підприємства у військовий час 101 4.4 Оцінка підготовки підприємства до відновлення виробництва 103 4.5 Надійність системи матеріально-технічного постачання і виробничих зв’язків 104 Висновок 108 Література 109
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Nisar, Asim. "Förbättring av monteringsstation för plockningsroboten IRB 360 FlexPicker." Thesis, Mälardalens högskola, Akademin för innovation, design och teknik, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:mdh:diva-49952.
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This thesis is about product and process development. The thesis has been done at ABB Robotics AB in Västerås under 20 weeks with half study pace, which is equivalent to 15 higher education credits (15hp). Thesis purpose was to improve an assembly station for assembling of robot IRB 360. Problems at the assembly station are that there are some non-value-creating activities and assembling methods which correspond to low safety factor for workers. The focus of thesis was to investigate opportunities and to produce solid proposals for how to eliminate these problems. After a written contract with ABB AB, the work started with the planning with the company supervisor and Gantt Schema was created to schedule all steps for this project, to ensure during the process. The project has followed the methods described in the book "Produktutveckling konstruktion och design " by Karl T Ulrich & Steven D Eppinger. Product development tools like Quality function deployment (QFD), functional analysis, specification of requirement and Pugh's analysis matrix have been used in the development process. In the first phase of the project, observation and investigation has been performed to identify and analyse problems. In the later phases, ideas and concepts has created to solve the problems and achieve successful results. The result of the project is an improved material flow at assembling stations which eliminates nonvalue-creating activities and leads to better safety for workers. Another result of the project is an elimination of hand hammering at assembling station and for this purpose a new pressing tool has been developed for pressing down a seals around radial shaft in assembling process. The software Solidworks has been used to create a new 3D layout for the existing assembly station to understand and find the better solution for material flow. Solidworks is also used for doing Finite element method (FEM) analysis to validate the new developed pressing tool.Detta examensarbete handlar om produkt och processutveckling. Arbetet utfördes hos ABB Robotics AB i Västerås och bedrivs under 20 veckor långt på halvfart vilket motsvarar 15 högskolepoäng. Uppdraget är att förbättra en monteringsstation för plockningsrobot IRB360 FlexPicker. Problem på monteringsstation är att det sker icke värdeskapande aktiviteter, och monteringsprocess som leder till arbetsmiljöproblem. Arbetet fokus var att undersöka möjligheter och ta fram konkreta förslag att hur man kan eliminera dessa problem. Efter skriftligt kontrakt med ABB AB, arbetet började med planeringen med företaget handledare och skapades Gantt Schema. Projektet har följt metoderna som beskrivs i boken ”Produktutveckling konstruktion och design” av författare Karl T Ulrich & Steven D Eppinger. I utvecklingsprocessen har använt produktutvecklingsverktyg, några av dessa är QFD, funktionsanalys, kravspecifikation och Pughs analysmatris. I första fas av projekt gjorde undersökning och observation för att hitta och analysera problem. I senare faserna genererade koncepter för åtgärden och sedan vidare utvecklades utvalda koncept för nå framgångsrikt resultat. Resultatet av arbetet blev förbättrad materialflöde som eliminerar icke värdeskapande aktiviteter. Dessutom utvecklades fram ett nytt pressverktyg som eliminerar arbetsmiljöproblem. Mjukvaran Solidworks har använt för att skapa en ny layout för monteringsstation. Med hjälp av Solidworks gjordes FEM -analys (Finita elementmetoden) för att validera den nya pressverktyg
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Lazouk, Melha-Amel. "Étude de l’impact de l’environnement sur les productions et des procédés sur la qualité des produits : application à la graine de lin." Thesis, Compiègne, 2015. http://www.theses.fr/2015COMP2188.
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Connues pour leur forte teneur en huile, oméga 3, antioxydants et fibres, les graines de lin sont de plus en plus demandées par les industries. D’où l’importance de contrôler leurs productions. Le but de ce travail est d’étudier l’effet des paramètres environnementaux et de la variété sur la composition de la graine de lin et sur le procédé ultérieur de pressage. Pour cela dix variétés de lin oléagineux ont été cultivées sur deux sites différents (Picardie et centre de la France) au cours des années 2011, 2012 et 2013. L’étude a révélé un fort effet variétal sur les teneurs en huile, C18:3, amidon et le PMG tandis que le lieu de culture n’a affecté que la teneur en lipides et amidon. L’effet année a quant à lui été marqué pour le PMG, les teneurs en protéines, lipides et C18:3. Le pressage des graines précédemment caractérisées a montré une forte corrélation entre teneur protéines et rendement. Afin d’améliorer le processus d'expression, le dépelliculage des graines de lin avant le pressage a été envisagé. Ainsi, l’étude du pressage des graines de lin sur presse hydraulique et presses continue montre la possibilité du pressage des graines dépelliculées. Une concordance entre les performances de pressage à l’échelle laboratoire et à l’échelle pilote a été obtenue pour les graines entières et dépelliculées ce qui laisse présager une transposition possible vers l’échelle industrielleFlaxseed is known for their high oil content, omega 3, antioxidants and fiber. To meet growing demand, this requires controlling their production. The aim of this work is to study the effect of environmental factors and cultivar on linseed composition and subsequent pressing process. Ten linseed cultivars were grown in two different locations (north and south of France) during years 2011, 2012 and 2013. Every year have been characterized in terms of pluviometry, sunshine hours and degree days, each climatic factor has been cumulated from flowering to harvest. A strong impact of cultivar on oil, C18:3 and starch content has been noticed whereas the growing location has only affected the starch and lipid contents. Year effect has been recorded on thousand kernel weight, proteins, oil, C18:3 and starch content. Oil expression using the seeds previously characterized has exhibited a strong correlation between protein content and oil yield. To improve the pressing process, dehulling flax seeds before pressing was considered. The study of the pressing flax seeds on hydraulic and continuous press shows the possibility of pressing the dehulling flaxseeds. The concordance between the pressing performance at the laboratory scale and pilot scale was highlighted for the whole and dehulled seeds. This could be suggests a possible transposition to the industrial scale
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Halvarsson, Sören. "Manufacture of straw MDF and fibreboards." Doctoral thesis, Mittuniversitetet, Institutionen för naturvetenskap, teknik och matematik, 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:miun:diva-11732.
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The purpose of this thesis was to develop an economical, sustainable, and environmentally friendly straw Medium Density Fibreboard (MDF) process, capable of full-scale manufacturing and to produce MDF of requested quality. The investigated straw was based on wheat (Triticum aestivum L.) and rice (Oryzae sativa L.). In this thesis three different methods were taken for manufacture of straw MDF; (A) wheat-straw fibre was blowline blended with melamine-modified urea-formaldehyde (MUF), (B) rice-straw fibre was mixed with methylene diphenyl diisocyanate (MDI) in a resin drum-blender, and (C) wheat-straw fibre was activated in the blowline by the addition of Fenton’s reagent (H2O2/Fe2+) for production of non-resin MDF panels. The MUF/wheat straw MDF panels were approved according to the requirements of the EN standard for MDF (EN 622-5, 2006). The MDI/rice-straw MDF panels were approved according to requirements of the standard for MDF of the American National Standard Institute (ANSI A208.2-2002). The non-resin wheat-straw panels showed mediocre MDF panel properties and were not approved according to the requirements in the MDF standard. The dry process for wood-based MDF was modified for production of straw MDF. The straw MDF process was divided into seven main process steps. 1. Size-reduction (hammer-milling) and screening of straw 2. Wetting and heating of straw 3. Defibration 4. Resination of straw fibre 5. Mat forming 6. Pre-pressing 7. Hot-pressing The primary results were that the straw MDF process was capable of providing satisfactory straw MDF panels based on different types of straw species and adhesives. Moreover, the straw MDF process was performed in pilot-plant scale and demonstrated as a suitable method for producing straw MDF from straw bales to finished straw MDF panels. In the environmental perspective the agricultural straw-waste is a suitable source for producing MDF to avoid open field burning and to capture carbon dioxide (CO2), the biological sink for extended time into MDF panels, instead of converting straw directly into bio energy or applying straw fibre a few times as recycled paper. Additionally, the straw MDF panels can be recycled or converted to energy after utilization. A relationship between water retention value (WRV) of resinated straw fibres, the thickness swelling of corresponding straw MDF panels, and the amount of applied adhesive was determined. WRV of the straw fibre increased and the TS of straw MDF declined as a function of the resin content. The empirical models developed were of acceptable significance and the R2 values were 0.69 (WRV) and 0.75 (TS), respectively. Reduced thickness swelling of MDF as the resin content is increased is well-known. The increase of WRV as a function of added polymers is not completely established within the science of fibre swelling. Fortunately, more fundamental research can be initiated and likely a simple method for prediction of thickness swelling of MDF by analysis of the dried and resinated MDF fibres is possible.Syftet med denna avhandling var att lägga grunden för en ekonomisk, hållbar och miljövänlig MDF process för halmråvara, kapabel för fullskalig produktion av MDF och goda skivegenskaper. Framställningen av MDF skivor utgick från halm av vete (Triticum aestivum L.) och ris (Oryzae sativa L.). Tre olika metoder användes för att producera MDF av halm; (A) fibrer av vetehalm belimmades i blåsledning med ett melaminmodifierat urea-formaldehydlim (MUF), (B) fibrer av rishalm belimmades i en limblandare med metylen difenyl diisocyanate (MDI), (C) Limfria MDF skivor av vetehalm framställdes med aktivering av fibrer genom tillsats av Fenton´s reagens (H2O2/Fe2+) i blåsledning utan någon tillsats av syntetiskt lim. Sammanfattningsvis kan det understrykas att framställda MDF-skivor av MUF/vetehalm var godkända enligt standard för MDF (EN 622-5, 2006). Dessutom var framställda MDF skivor av MDI/rishalm också godkända enligt krav i standard för MDF ”American National Standard Institute” (ANSI A2008.2-2002). Limfria vetehalmskivor visade på måttliga skivegenskaper och klarade inte kraven i MDF standard. Fiberframställningsprocessen för MDF modifierades till en produktion utgående från halm. MDF processen för halm delades upp i sju primära processoperationer. (1) Storleksreducering och sållning av halm (2) Vätning och uppvärmning av halm (3) Defibrering (4) Belimning av halmfiber (5) Mattformning (6) Förpressning (7) Pressning De viktigaste resultaten från denna studie är att MDF av halm kunde produceras utgående från olika typer av halmsorter och lim. Dessutom utfördes MDF-processen i pilotskala och visade på en lämplig metod för framställning av MDF-skivor från halmbalar till färdiga halmfiberskivor. Det miljömässiga perspektivet på att använda jordbruksavfall till framställning av halmskivor är att undvika förbränning av halm ute på fältet, men det är även möjligt att binda koldioxid (CO2) i halmskivor under längre tid än att omsätta halmråvaran omedelbart som bioenergi eller använda halmfiber som returpapper några få gånger. Dessutom kan MDF återanvändas eller bli omsatt till energi efter användning. Ett förhållande mellan ”water retention value” (WRV), av belimmade halmfiber, tjocklekssvällning för motsvarande MDF av halmskivor och mängden av tillsatt lim vid olika nivåer har undersökts. Med ökande limhalt tilltog WRV fibersvällning, vidare minskade tjocklekssvällning för motsvarande MDF skivor. De framtagna empiriska modellerna var godtagbara och beräknade R2 värden var 0.69 (WRV) och 0.75 (TS). Minskad tjocklekssvällning med ökad limhalt är dokumenterad sen tidigare. Ökad fibersvällning WRV vid tillsats av polymerer (limmer) är inte fullständigt etablerad inom vetenskapen för fibersvällning. Lyckligtvis kan grundläggande forskning initieras och sannolikt föreligger en enkel metod för att prediktera tjocklekssvällning av MDF genom analyser av torkade och belimmad MDF fiber.
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Gómez, Meza Diego Armando. "Modelamiento fenomenológico de la densificación del Mo en el proceso de hot isostatic pressing (HIP)." Tesis, Universidad de Chile, 2018. http://repositorio.uchile.cl/handle/2250/167757.
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Magíster en Ciencias de la Ingeniería, Mención MecánicaEl proceso denominado compactación isostática en caliente (o por su nombre en inglés, Hot Isostatic pressing, HIP) es un proceso de manufactura que ha tomado gran relevancia en las últimas décadas para la consolidación de polvos, dado que la aplicación simultánea de temperatura y presión ocasiona que los mecanismos de densificación (obtenidos tradicionalmente por sinterización) se vean optimizados; en efecto, la presión aplicada mejora los mecanismos de difusión y activa los mecanismos de densificación por deformación de las partículas, lo que permite obtener densidades de hasta 100% de su densidad teórica. Por otro lado, el molibdeno (Mo) es un metal de transición cuyas propiedades y características como aleante hacen de este un material de gran importancia en los mercados mundiales, en la producción de aceros de construcción, aceros inoxidables y superaleaciones. El Mo en su estado puro es usado en la industria en aplicaciones donde se requieren altos puntos de fusión, alta resistencia mecánica a altas temperaturas, alta conductividad térmica y/o alta resistencia a la corrosión. Sin embargo, el molibdeno es un material complejo de procesar, por lo que su aplicación a gran escala en la industria solo puede ser concebida cuando el proceso producción es eficiente. Por lo anterior, el objetivo de este trabajo es plantear y desarrollar la base de aplicación del proceso de manufactura HIP en Mo, al desarrollar un modelamiento fenomenológico que permita obtener los mapas de compactación por HIP y contrastar, experimentalmente, los mapas y modelos empleados, al fabricar muestras a diferentes valores de presión, temperatura y tiempos de sostenimiento. Los resultados obtenidos permiten predecir la densidad relativa del Mo durante el HIP, en función de los parámetros de temperatura, presión y tiempo de sostenimiento, al igual que permiten determinar el mecanismo de densificación predominante.
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Dusserre, Gilles. "Sollicitations thermomécaniques dans un moule en acier inoxydable martensitique moulé au cours du cycle de pressage de verre." Toulouse 3, 2006. http://www.theses.fr/2006TOU30216.
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Le procédé de pressage de verre consiste à mettre en forme une paraison de verre par écrasement entre deux outils. L'utilisation de moules en acier inoxydable moulé permet une réduction du prix de revient de l'outillage, mais cela s'effectue au détriment de la durée de vie des moules creux qui s'endommagent à partir de défauts de fonderie, des micro-retassures présentes aux points triples des joints inter-dendritiques. Cette thèse est une contribution à l'amélioration de la durée de vie de ces outillages. L'objectif est de déterminer les sollicitations thermomécaniques dans le moule au cours du cycle de pressage de verre Pyrex®. Les sollicitations sont de deux types : les contraintes dues au gradient de dilatation thermique lors du transfert de chaleur du verre au moule et les contraintes de surface générées par l'écoulement du verre. L'instrumentation d'un moule industriel en vue de la mesure in-situ de températures en service fournit des informations sur le procédé (temps de cycle, températures de service…) et permet, par méthode inverse, d'estimer le flux de chaleur reçu ou cédé par le moule au cours du cycle. Une loi viscoélastique en grandes déformations est proposé et identifié à partir d'essais de compression d'échantillons cylindriques de verre. Le procédé industriel de mise en forme est ensuite simulé en utilisant le modèle identifié précédemment dans le but de déterminer les contraintes normales et tangentielles exercées par le verre sur le moule au cours du pressage. Un modèle de comportement est identifié pour prendre en compte l'adoucissement caractéristique des aciers martensitiques lorsqu'ils sont soumis à un chargement mécanique cyclique. Les modèles, mesures et résultats de calculs mentionnés ci-dessus sont enfin utilisés pour calculer l'évolution du champ de contraintes dans le moule au cours du cycle de pressage en tenant compte au mieux des conditions réelles d'utilisation du moule. Cette mise en données est le point de départ d'une étude paramétrique numérique destinée à étudier l'influence des conditions d'utilisation de l'outillage sur les sollicitations thermomécaniques dans le mouleGlass pressing process is a forming process in which a glass gob is squeezed between two tools. The use of cast stainless steel moulds instead of wrought steel allows a decrease of the tooling costs, but the life time of the hollow mould is consequently decreased. The damages usually take place at the triple junction of dendrites. This thesis is a contribution to the improvement of these tools life time. The aim is to determine the thermomechanical loads of the mould during a glass pressing cycle. Two types of loading exist : the thermal stresses caused by the gradient of thermal dilatation caused by the heat transfer at the glass and mould interface and the superficial stresses caused by the flow of the glass along the surface of the die. An instrumentation of an industrial mould has been realized in order to measure the temperatures in the industrial context and inform about the process (time cycle, use temperature…). An inverse method has been used to estimate the heat flux density at the surface of the tool during the cycle. A high strain viscoelastic law is proposed and identified from compression tests with cylindrical glass samples. The industrial forming process is then simulated using this new rheological law in order to determine the normal stresses on the mould while pressing
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Vaculík, František. "Proces opravy dvojkolí." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2011. http://www.nusl.cz/ntk/nusl-229511.
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Diploma work describes in its theoretical part particular types of pairs of wheels used on railway vehicles in Czech Republic as well as their components and assembly instructions. Practical part describes workplace for wheels in reparation DPOV, a.s. at repairing centre Nymburk, its facilities and repairing possibilities by total repair of pairs of wheels. Practical part brings at the end particular report with results of pairs of wheels measuring.
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Dopler, Thomas. "Low pressure infiltration process modeling." Châtenay-Malabry, Ecole centrale de Paris, 1999. http://www.theses.fr/1999ECAP0673.
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Les composites à matrice métallique, une matrice métalliquerenforcée par des fibres ou particlues céramiques, constituent un solution élegante pour obtenir des materiaux à propriétés mécaniques, de résistance à l'usure et à la fatigue exceptionnelles. Leurs applications sonts pour le moment limitées, moins à cause de leur coût, mais plutôt à cause des problème liés à la reproductibilité et à la dispertionde leurs propriétés. Le travail présent contribue au développement d'un code de simulation capable de prédire la cinétique d'infiltration pendant l'infiltration sous pression. Pour la première fois l'écoulement non saturé et le transfert de chaleur incluant la solidification sont traités d'une façon simultanée.
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Santos, Alan Andrade dos. "Estudo de variáveis no processo de compactação de pós a base de alumina." Universidade de São Paulo, 2012. http://www.teses.usp.br/teses/disponiveis/85/85134/tde-05112012-100337/.
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O processo de conformação por prensagem uniaxial é um dos mais utilizados na indústria cerâmica devido ao seu baixo custo e alta produtividade. O entendimento e controle dos diversos fatores que interferem neste processo são cruciais, pois grande parte dos defeitos encontrados na peça final é originada nesta etapa. Este trabalho trata da avaliação da compactação de pós a base de alumina processados em spray-dryer, com diferentes composições e contendo distintos aditivos orgânicos, sendo caracterizados em relação a fluidez, densidade solta e batida, determinação da distribuição do tamanho de grânulos e morfologia. Parâmetros como umidade (10, 64 e 85%) e temperatura (5, 25 e 45°C) foram variados. O comportamento do pó foi analisado nas diferentes etapas de compactação, as quais envolvem a deformação plástica e quebra dos grânulos e também redução da porosidade intergranular e intragranular. Posteriormente foram estudadas a influência da temperatura e da umidade relativa do ar durante a compactação, sendo o efeito dos mesmos avaliados por meios de curvas de compactação. A resistência mecânica das peças também foi avaliada por meio do módulo de Weibull. Através da análise da microestrutura (MEV e porosimetria) e de curvas de compactação constatou-se que os parâmetros citados acima interferem nas características dos compactados, particularmente na resistência mecânica dos grânulos em relação à deformação e fratura. Os resultados mais importantes são que quanto maior a temperatura e umidade ocorre a redução da Tg dos ligantes, diminuindo a resistência ao esmagamento dos mesmo e que através do módulo de Weibull é possível determinar qual a melhor condição para realizar a prensagem que no caso deste estudo foi a condição intermediária.The compaction process by uniaxial pressing is the most used in the ceramics industry due to its low cost and high productivity. The understanding and control of several factors that interfere in this process are crucial, since most of the defects found in the final piece are originated at this stage. This paper deals with compaction evaluation of alumina powders, processed by spray-dryer with different compositions and containing different organic additives, being characterized according the flow, tap and apparent density, granule size distribution and morphology. Parameters such as relative humidity (10, 64 and 85%) and temperature (5, 25 and 45°C) were varied. The powder\'s behavior was analyzed at different compaction stages, which involves plastic deformation, breakage of the granules and reduction of intergranular and intragranular porosity. The influence of temperature and relative humidity during compaction were analyzed by compaction curves. The mechanical strength of the obtained parts was evaluated using the Weibull modulus. The microstructural analysis (SEM and porosimetry) and evaluation of the compaction curves shows that these parameters affect the characteristics of compacted powder, in particular the mechanical strength of the granules in relation to the deformation and fracture. The most important results show that higher the temperature and relative humidity occurs the Tg reduction of binders, decreasing the mechanical strength of binders and by Weibull modulus it is possible to determine the best condition for pressing, in this instance the intermediate condition.
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Silva, Gilson Jr. "Estudo da influência do processo ECAP (Equal Channel Angular Pressing) nas propriedades mecânicas e características microestruturais do aço SAE 1020." Universidade Estadual Paulista (UNESP), 2017. http://hdl.handle.net/11449/152335.
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A obtenção de granulometria ultrafina em aços com baixo teor de carbono pode contribuir para ampliação de suas aplicações na indústria, devido as propriedades mecânicas superiores que podem ser alcançadas com o refinamento de grãos, tais como: resistência mecânica, dureza, e tenacidade. O processo conhecido como Equal Channel Angular Pressing (ECAP) induz deformações plásticas severas suficientes para alterar as características microestruturais dos metais reduzindo seu tamanho de grão, e consequentemente melhorando algumas propriedades mecânicas, sem alterar a composição química dos materiais, ao utilizar temperaturas abaixo do ponto de recristalização dos metais. Neste trabalho o processo ECAP foi conduzido com corpos de prova na temperatura de 550°C utilizando como material de estudo aço SAE 1020. Os corpos de prova foram separados em três grupos. No primeiro grupo as amostras não foram submetidas a nenhum tratamento térmico entre os passes, no segundo grupo foi aplicado tratamento de alívio de tensões após os passes, e por fim, no terceiro grupo e foi aplicado um tratamento de recozimento intercrítico após o primeiro passe. Ensaios mecânicos de tração, dureza e charpy foram realizados com objetivo de verificar a influência do processo ECAP no comportamento mecânico do aço. Com intuito de verificar as alterações microestruturais causadas pelo processo ECAP foram utilizadas as técnicas de microscopia óptica e eletrônica de varredura. O trabalho tem como objetivo principal induzir o refinamento dos grãos por meio do processo ECAP em matriz bipartida elaborada neste trabalho. Os resultados das análises microestruturais e dos ensaios mecânicos demonstraram que os tratamentos térmicos utilizados combinados ao processo ECAP influenciaram diretamente no comportamento do aço SAE 1020. Conforme o número de passes pela matriz ECAP ocorreu uma redução do tamanho dos grãos, assim como aumento do limite de resistência a tração e dureza do aço 1020. Com relação ao tratamento térmico de alívio de tensão, uma melhor combinação entre resistência mecânica e ductilidade foi encontrada. O tratamento de recozimento intercrítico foi suficiente para induzir a transformação de fases no aço SAE 1020, o qual proporcionou resultados positivo no que diz respeito a ductilidade e resistência mecânica. Por fim, a consistência das investigações da evolução microestrutural permitiu compreender os efeitos do ECAP no aço SAE 1020.
Ultrafine grained microstructures obtaining in low carbon steels may contribute to enlarge the application of this material in industry, due to superior properties that can be achieved, such as: mechanical strength, hardness, and toughness. The process known as Equal Channel Angular Pressing (ECAP) induces severe plastic deformation sufficient to modify metals microstructures characteristics, reducing its grains size, and consequently improve its mechanical properties without materials chemistry composition changes, under temperatures below to recrystallization point. At this work ECAP process was carried out with specimens at 550° C using steel SAE 1020 as material. The specimens were divided into three groups. The specimens in the first group none heat treatment was applied between and after ECAP passes, in the second group the specimens were submitted under stress relief heat treatment after ECAP passes, and in the third group, specimens were submitted under intercritical annealing after first pass. Mechanical tensile strength, hardness and charpy impact tests were used with aim to verify the ECAP influence in steel mechanical behavior. In order to verify microstructures evolution caused by ECAP were applied optical and scanning electron microscopy. The aim of this work is grain refining by means of ECAP process with two parts tool elaborated in this study. The microstructure analysis and mechanical tests results shown that the heat treatments applied, combined with ECAP process directly influenced on steel SAE 1020 behavior. According to the number of passes grains sizes were reduced, as well the ultima tensile strength and hardness were increased. In reference of stress relief heat treatment, better combination between mechanical strength and ductility was achieved. Intercritical annealing treatment was capable to induce phase transformation in steel SAE 1020, which provided positive results with respect to ductility and mechanical strength. In conclusion, the consistence of microstructure evolution investigation became possible to understand effects of ECAP in steel SAE 1020
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Silva, Junior Gilson. "Estudo da influência do processo ECAP (Equal Channel Angular Pressing) nas propriedades mecânicas e características microestruturais do aço SAE 1020 /." Guaratinguetá, 2017. http://hdl.handle.net/11449/152335.
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Orientador: Angelo Caporalli FilhoBanca: Marcelo dos Santos Pereira
Banca: Ana Paula Rosifini Alves Claro
Banca: Karia Regina Cadorso
Banca: Mirian de Lourdes Noronha Motta Melo
Resumo: A obtenção de granulometria ultrafina em aços com baixo teor de carbono pode contribuir para ampliação de suas aplicações na indústria, devido as propriedades mecânicas superiores que podem ser alcançadas com o refinamento de grãos, tais como: resistência mecânica, dureza, e tenacidade. O processo conhecido como Equal Channel Angular Pressing (ECAP) induz deformações plásticas severas suficientes para alterar as características microestruturais dos metais reduzindo seu tamanho de grão, e consequentemente melhorando algumas propriedades mecânicas, sem alterar a composição química dos materiais, ao utilizar temperaturas abaixo do ponto de recristalização dos metais. Neste trabalho o processo ECAP foi conduzido com corpos de prova na temperatura de 550°C utilizando como material de estudo aço SAE 1020. Os corpos de prova foram separados em três grupos. No primeiro grupo as amostras não foram submetidas a nenhum tratamento térmico entre os passes, no segundo grupo foi aplicado tratamento de alívio de tensões após os passes, e por fim, no terceiro grupo e foi aplicado um tratamento de recozimento intercrítico após o primeiro passe. Ensaios mecânicos de tração, dureza e charpy foram realizados com objetivo de verificar a influência do processo ECAP no comportamento mecânico do aço. Com intuito de verificar as alterações microestruturais causadas pelo processo ECAP foram utilizadas as técnicas de microscopia óptica e eletrônica de varredura. O trabalho tem como objetivo principal in... (Resumo completo, clicar acesso eletrônico abaixo)
Abstract: Ultrafine grained microstructures obtaining in low carbon steels may contribute to enlarge the application of this material in industry, due to superior properties that can be achieved, such as: mechanical strength, hardness, and toughness. The process known as Equal Channel Angular Pressing (ECAP) induces severe plastic deformation sufficient to modify metals microstructures characteristics, reducing its grains size, and consequently improve its mechanical properties without materials chemistry composition changes, under temperatures below to recrystallization point. At this work ECAP process was carried out with specimens at 550° C using steel SAE 1020 as material. The specimens were divided into three groups. The specimens in the first group none heat treatment was applied between and after ECAP passes, in the second group the specimens were submitted under stress relief heat treatment after ECAP passes, and in the third group, specimens were submitted under intercritical annealing after first pass. Mechanical tensile strength, hardness and charpy impact tests were used with aim to verify the ECAP influence in steel mechanical behavior. In order to verify microstructures evolution caused by ECAP were applied optical and scanning electron microscopy. The aim of this work is grain refining by means of ECAP process with two parts tool elaborated in this study. The microstructure analysis and mechanical tests results shown that the heat treatments applied, combined with ECAP p... (Complete abstract click electronic access below)
Doutor
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Vagliatti, Rafael Brufatto. "Desenvolvimento de processo de extrusão e prensagem de rebites de aço inox." reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 2017. http://hdl.handle.net/10183/169821.
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Este trabalho analisou as diferenças entre o processo de conformação de rebites de Alumínio da liga AA 5052 e de aço inoxidável das ligas ABNT 420, ABNT 430 e ABNT 302, os quais são utilizados em grande escala na indústria cuteleira. Levando em conta as particularidades de cada material em estudo, foram analisadas as forças de conformação, tensões, deformações e temperaturas. A partir delas buscou-se chegar a um modelo de processo viável para se obter rebites de Aço inoxidável. Apesar da fabricação do rebite de Alumínio ser menos crítica, no que diz respeito a força necessária para conformação, a qualidade do produto é inferior, quando se compara com o Aço inoxidável. Este confere maior resistência mecânica e resistência à corrosão. Para modelamento do processo desenvolvido com o Alumínio AA5052 e com as ligas de Aço inoxidável utilizadas utilizou-se o software de simulação por elementos finitos SIMUFACT 11.0. Os resultados das simulações com o aço inoxidável com temperaturas a morno demonstraram grande dependência da temperatura para obtenção de tensões e forças suportadas pelo ferramental. Alguns resultados alcançados com o aço inoxidável aquecido, quando se variaram as temperaturas de 25ºC até 500ºC, geraram o grau de tensões e esforços no ferramental menor ou igual à condição onde o Alumínio é conformado a frio. Também, critérios como resistência à corrosão foram determinantes para a aprovação das ligas de aço inoxidável 302 e 430 estudadas. Esse resultado confirmou o que é indicado na bibliografia, onde são recomendadas ligas austeníticas e ferríticas, ao invés de martensíticas, para a fabricação de produtos de aço inoxidável que exigem alta resistência à corrosão, como é o caso dos rebites.This study analyzed the differences between the rivet manufacturing process made by Aluminum of alloy AA5052 and Stainless Steel of alloys AISI 420, AISI 430 and AISI 302, wich are widely used in the cutlery industry. Taking into account the particularities of both materials, it was analyzed forming forces, stresses, strains and temperatures in order to find a viable process to manufacture stainless steel rivets. Even the manufacturing of Aluminum rivets is less critical, regarding the forming forces, the quality of the product is inferior than the stainless steel, wich provides more mechanical and corrosion resistance. The study of the process of forming Aluminum AA5052 and Stainless Steel rivets was developed using the finite elements software SIMUFACT 11.0. The simulation results of the Stainless Steel with warm temperatures showed big influence of the temperature to obtain lower stresses and forces, wich are supported by the tools. Some results with heated Stainless steel, considering temperatures from 25ºC to 500ºC, resulted in lower stress and tool forces than in the Aluminum with cold temperatures. Also, criteria like corrosion resistance was very important to the approval of the Stainless Steel AISI 302 and AISI 430. Those results confirm the information available in the bibliography, where it is preferential austenitic and ferritic alloys of stainless steel instead of martensitic alloys, when used to manufacture stainless steel rivets, wich require high corrosion resistance.
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Krystýnová, Michaela. "Procesy přípravy a charakterizace objemového materiálu z prášků Mg a Zn." Master's thesis, Vysoké učení technické v Brně. Fakulta chemická, 2016. http://www.nusl.cz/ntk/nusl-240585.
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Topic of the diploma thesis is Mg-Zn bulk material preparation process by powder mixtures sintering at hot pressing. Structure, porosity and physically-mechanical properties of prepared bulk materials was evaluated. Obtained results and their interpretation were served as feedback for following optimization of individual processing parameters of bulk materials preparation. Thesis solving focuses on study and control of processes during bulk material preparation and description of the processes from physically-chemical point of view of the structure creation and final material properties.
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BONIFACIO, RAFAEL N. "Desenvolvimento de processo de produção de conjuntos eletrodo-membrana-eletrodo para células a combustível baseadas no uso de membrana polimérica condutora de protons (PEMFC) por impressão a tela." reponame:Repositório Institucional do IPEN, 2010. http://repositorio.ipen.br:8080/xmlui/handle/123456789/9520.
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Dissertacao (Mestrado)
IPEN/D
Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP
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Ciafardo, Marco. "Applicazioni del calcolo agli elementi finiti orientato alla verifica strutturale delle apparecchiature in pressione." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2021.
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La tesi documenta il lavoro di studio e applicazione svolto nel percorso di tirocinio, un percorso di formazione sull' utilizzo di software CAD/CAE e nella loro applicazione per analisi di tipo statico-lineare, modale e soprattutto analisi non lineare. Il capitolo 1 introduce l' ideologia di Open Source sulla quale si basato tutti i software utilizzati nella tesi, i quali vengono descritti nel capitolo 2. Nel capitolo 3 si affronta il discorso di analisi agli elementi finiti, il metodo di calcolo che utilizzano i software introdotti. Il capitolo 4 e il capitolo 5 si occupano di descrivere le analisi statiche lineari e modale svolte con il software Salome-Meca, mentre i capitoli 6 e 7 riportano la teoria del calcolo non-lineare e applicazioni con il software SimScale.
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Zhang, Fan. "Intensification du procédé antisolvant supercritique (SAS) par l'usage de microréacteur sous pression." Thesis, Bordeaux, 2019. http://www.theses.fr/2019BORD0269.
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Dans le cadre de cette thèse, nous nous proposons d’étudier le comportement thermo-hydrodynamique d’un mélange solvant/antisolvant supercritique dans une puce microfluidique, pour des conditions utilisées dans le procédé SAS (Supercritical Antisolvent System). Ce travail se base sur une approche complémentaire expérience/simulation via l’utilisation de techniques de recherches avancées telles que la caractérisation in situ sur puce microfluidique (micro-PIV – micro Particle Image Velocimetry) et la simulation numérique intensive. L’objectif de la thèse est de définir les conditions favorables à un « très bon » mélange (total et rapide) des espèces en termes de vitesse, température, pression et « design » d’injecteur. Les simulations sont effectuées avec le code de calcul Notus, massivement parallèle. Après un premier chapitre détaillant l’état de l’art sur les procédés antisolvant supercritiques, puis un second concernant les méthodologies utilisées (modèle numérique, outils microfluidiques), nous comparons dans un premier temps les résultats des simulations numériques à ceux obtenus avec les expériences de micro-PIV en écoulement laminaire. La comparaison est très bonne pour l’ensemble des expériences réalisées. Le code de calcul ainsi validé, nous proposons d’utiliser l’outil numérique comme véritable outil de recherche des meilleures conditions opératoires pour favoriser le mélange. Pour cela, des simulations du mélange de deux fluides (typiquement CO2 et éthanol) sont effectuées pour différentes conditions opératoires (vitesse, température, pression) pour des conditions laminaires mais également en conditions turbulentes, régime rarement atteint à ces échelles de réacteur. En effet, nous avons montré expérimentalement que le régime turbulent pouvait être atteint dans le microcanal grâce à la technologie « microfluidique haute pression » développé au laboratoire. L’étude de la qualité du mélange se base sur deux critères communément utilisées dans la littérature. Le premier est l’index de ségrégation basé sur la variance du champ de concentration ou fraction massique dans notre cas. Celui-ci peut être estimé pour tous les cas de simulation, du laminaire au turbulent. Le deuxième critère est le temps de micromélange basé sur l’estimation du taux de dissipation de l’énergie cinétique turbulente. Celui-ci est calculé uniquement dans les cas turbulents car basé sur les fluctuations des vitesses par rapport à la valeur moyenne. Un des intérêts majeurs de l’utilisation des puces microfluidiques réside notamment dans ses faibles échelles de temps et d’espace. D’un point de vue numérique, de telles échelles permettent, dans des temps de calcul raisonnables, de proposer des simulations numériques directes (DNS), i.e., dont les plus petites mailles sont inférieures ou très proches de l’échelle de Kolmogorov. Ceci est de tout premier intérêt car nous sommes capables de capter les plus petites échelles du mélange et notamment le micromélange. Ainsi, les résultats de simulation nous ont permis de proposer une analyse fiable du mélange d’un point de vue qualitatif et quantitatif, faisant la preuve que les conditions de mélange dans ce type de dispositif sont particulièrement favorables pour l’élaboration de matériaux par antisolvant supercritique. Les conditions optimales de mélange ainsi déterminées, nous proposons dans une dernière partie de simuler la synthèse de nanoparticules organiques dans de tels dispositifs. L’approche numérique est basée sur un couplage des équations de la mécanique des fluides et d’une équation de bilan de population permettant de prendre en compte la nucléation et croissance des particules. Les résultats de simulation ont été comparés avec succès avec ceux expérimentaux obtenues au laboratoireIn the context of this thesis, we propose to study the thermo-hydrodynamic behavior of a mixture, a solvent and a supercritical antisolvent (CO2) in a microfluidic chip, for conditions used in the Supercritical Antisolvent (SAS) process. This work is based on a complementary approach of both experiments and simulations through the use of advanced research techniques, such as the in situ characterization inside the microfluidic reactor (Micro-Particle Image Velocimetry) and the High Performance Computing. The objective of the thesis is to determine the favorable conditions for a "very good" mixture (total and fast) of species in terms of velocity, temperature, pressure and injector "design". The simulations are performed with the massively parallel code Notus. After the first chapter detailing the state of the art on the supercritical antisolvent processes, then the second concerning the applied methodologies (numerical model, microfluidic tools), we first compare the results of the numerical simulations to the experimental data obtained by micro-PIV in laminar flow conditions. The simulation results are in good agreement with the experiments. After the validation of the numerical code, we propose to use the numerical tool to determine the optimal operating conditions of mixing. For this, simulations of the mixture of two fluids (typically CO2 and ethanol) are performed for different operating conditions (velocity, temperature, pressure) for laminar conditions but also for turbulent conditions, a regime rarely reached in microreactors. Indeed, we have shown experimentally that the turbulent mixing could be reached in the microchannel thanks to the "high pressure microfluidic" technology developed in the laboratory. The study of the mixing quality is based on two criteria commonly used in the literature. The first is the segregation intensity based on the variance of the ethanol concentration. This can be estimated for all simulation cases, from laminar to turbulent mixing. The second criterion is the micromixing time related to the turbulent kinetic energy dissipation rate directly estimated from the local velocity fluctuations in turbulent flow conditions. One of the major interests of the use of microfluidic reactors lies especially in its small scales of time and space. From a numerical point of view, such scales allow, within reasonable CPU time, to perform direct numerical simulations (DNS), i.e., in which the grid size is smaller or very close to the Kolmogorov scale. This is of primary interest because we are able to capture the smallest scales of the mixture including the micromixing. Thus, the simulation results allow us to propose a reliable analysis of the mixture from both qualitative and quantitative point of view, proving that the mixing conditions in this type of device are particularly favorable for the material synthesis by supercritical antisolvent. After determining the optimal mixing conditions, we propose in a final part to simulate the synthesis of organic nanoparticles in such devices. The numerical approach is based on the coupling between the CFD code and a population balance equation to take into account the nucleation and growth of particles. The simulation results are also in a good agreement with the experimental measurements performed in the laboratory
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Himber, Jacques. "Caracterisation des recepteurs adrenergiques des proces ciliaires : application a l'etude in vivo et in vitro d'antagonistes beta et d'agonistes alpha actifs sur la pression intra-oculaire." Université Louis Pasteur (Strasbourg) (1971-2008), 1988. http://www.theses.fr/1988STR13231.
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Outmani, Imane. "Caractérisation des variabilités Matériaux/ Process pour une convergence produit de fonderie par approche prédictive." Thesis, Paris, ENSAM, 2017. http://www.theses.fr/2017ENAM0007/document.
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Les alliages Al-Si sont largement utilisés dans l’industrie automobile en fonderie sous pression, en particulier pour la fabrication des blocs moteurs, en raison de leurs bon rapport résistance/ poids et leurs excellentes propriétés mécaniques. Du fait de l’internationalisation de la production, la composition chimique de ces alliages et les paramètres du procédé HPDC peuvent varier d’un pays à l’autre, ils peuvent même varier d’un site de fabrication à l’autre dans le même pays. Or, les conceptions des pièces automobiles sont aujourd’hui de type déterministe et elles sont réalisées sur la base des matériaux et procédés européens, ce qui peut affecter les propriétés de ces pièces dans le cas d’une localisation hors Europe. Ainsi, il est important de pouvoir adapter les conceptions rapidement et à moindre coût en prenant en compte les contraintes matériau/ process locales. Dans cette thèse, nous avons proposé une approche méthodologique permettant de prédire les caractéristiques mécaniques en fonction de la variabilité matériaux/ process en s'appuyant sur une étude expérimentale/ statistique de l’effet de la variabilité des principaux éléments d’alliage (Si, Cu, Mg) et des paramètres procédé (température de la coulée et pression d’injection) sur les propriétés mécaniques des alliages d’Al-Si moulés sous pression. La microstructure et le taux de porosités ont également été évalués. Cette méthodologie a abouti à la construction d’un outil de conception produit permettant de prédire les caractéristiques mécaniques dans le cas du changement de l’un (ou des) paramètres Matériau/ ProcessSecondary Al-Si alloys are widely used in automotive industry for engine blocks because they offer a considerable weight reduction whilst maintaining good mechanical properties. The ever-expanding internationalisation of production, with same stages of production processes spread across a number of countries to produce locally, causes however high variability in the casting products. The chemical composition of the same alloys and the working variables of the unchanged high-pressure die casting process (HPDC) may change for the same casting parts from one country to another, they can even sometimes vary from one manufacturing site to another within the same country. Designing for aluminium automotive components does call today for new deterministic design methods that are often achieved from European material and casting process databases, which can affect the properties of these parts in the case of a location outside Europe. Thus, it is important to adapt the design of die casting parts quickly and inexpensively by taking into account the material and process local constraints. In this work, a methodological approach which permits to predict mechanical properties as a function of material and process variability based on an experimental/ statistical study on the effect of the variability of the primary factors of alloying elements contents (Si, Cu and Mg) and HPDC process parameters (casting temperature and injection pressure) on mechanical properties of die cast aluminium alloys has been proposed. The microstructural features and the porosity level were also investigated and assessed. This approach has resulted in statistical design tool that will allow designers to make changes to the design of their casting and to industrialize them outside Europe
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Viguier, Françoise. "Écoulements diphasiques lors de la vidange d'un réservoir de gaz liquéfiés sous pression. Comparaison Eau - CFC11-CFC113." Phd thesis, Ecole Nationale Supérieure des Mines de Saint-Etienne, 1992. http://tel.archives-ouvertes.fr/tel-00844457.
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Pour les études de sécurité industrielle, il est nécessaire d'évaluer le débit diphasique lors de vidanges accidentelles de stockages de gaz liquéfiés sous pression. Or, seules de rares études existent avec d'autres produits que l'eau. Le présent travail s'intéresse donc à l'influence de la nature du fluide mais aussi de la géométrie de la conduite. Nous avons conçu un montage expérimental (réservoir de 27 litres admettant une pression de 0,4 MPa) afin de comparer l'eau, le CFC11 et le CFC113 dans une même installation. Différentes conduites (diamètres 8 et 16 mm et longueurs de 0,1 à 0,6 m) ont d'abord été utilisées avec l'eau afin de déterminer la meilleure géométrie pour cette comparaison. Les mesures réalisées dans le réservoir montrent qu'au cours de la vidange il existe des oscillations de la pression, qui sont plus importantes pour les CFC que pour l'eau. Malgré ces différences, les trois fluides testes restent très prés des conditions d'équilibre. Les débits mesures sont ensuite comparés aux estimations de différents modèles. Les hypothèses les plus simples (Modèle homogène à l'équilibre) conduisent à une bonne évaluation du débit. Il ressort de cette analyse qu'il est nécessaire de considérer des frottements pour une bonne description des mesures faites le long de la conduite. Cependant, il existe des écarts résiduels entre les prévisions de ces modèles et les résultats expérimentaux: les débits mesures et ceux estimes ne sont pas égaux mais, de plus, le rapport de ces deux débits est différent selon le fluide utilisé. Pour expliquer ces écarts, il nous apparait nécessaire de prendre en compte simultanément des vitesses différentes (Échanges de quantité de mouvement entre les phases) d'une part et des écarts à l'équilibre d'autre part.
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Lenzi, Daniele. "Analisi dei difetti in componenti meccanici prodotti in lega leggera mediante il processo di colata sotto pressione." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2018. http://amslaurea.unibo.it/15209/.
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L’elaborato si prefigge l’obbiettivo di analizzare i difetti che si possono riscontrare nel realizzare prodotti in alluminio attraverso il processo di colata sotto pressione. In particolare, si studiano i parametri e i fenomeni che rivestono maggiore importanza nel processo, al fine di ottenere un prodotto finale che presenti una limitata difettosità. Infine si studia un caso di difettosità riscontrato in azienda, analizzando i risultati delle simulazioni del processo, le analisi termiche svolte attraverso l'utilizzo di termocamere e si indaga la microstruttura con l'ausilio di un microscopio ottico.
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Savignon, Edouard. "Modélisation et étude d'une décharge filamentaire à basse intensité et haute-pression dans l'argon." Phd thesis, Université d'Orléans, 2007. http://tel.archives-ouvertes.fr/tel-00458689.
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Les décharges filamentaires obtenues dans l'Argon et les gaz rares, à faible intensité (I < 1 A) et haute pression (pression atmosphérique et pressions supérieures) sont caractérisées par un petit diamètre (quelques dixièmes de millimètre), un champ électrique élevé (E = 10 kV/m) et une grande différence de température entre les électrons (Te = 10000 K) et les atomes (T0 = 1500 K). Pour étudier ces décharges encore mal connues, intermédiaires entre l'arc électrique et la décharge luminescente, nous avons élaboré un modèle capable, à partir de la connaissance d'un petit nombre de paramètres qui conditionnent le fonctionnement de la décharge (intensité du courant, champ électrique, diamètre, pression) de déterminer les principales grandeurs physiques (températures des électrons et des atomes, densités des électrons et des ions atomiques et moléculaires, densités des états excités) caractérisant le plasma ; ce modèle a été construit à partir des équations de conservation des particules chargées, des atomes excités et de l'énergie des électrons en prenant en compte l'ensemble des niveaux 4s et 4p de l'argon dont les sections efficaces d'excitation et d'ionisation par chocs électroniques sont bien connues. Le principal processus de disparition des électrons est la recombinaison dissociative des ions moléculaires A2+ (A2+ + e → A* + A) dont la formation par une réaction à trois corps (A+ + A + A → A2+ + A) est favorisée par la basse température et la haute pression du milieu ; les atomes excités A* sur un niveau 4p facilement ionisable, provenant de la recombinaison des ions A2+ permettent d'obtenir des densités électroniques importantes à des températures électroniques et atomiques relativement basses ; on a également pris en comte l'absorption partielle par le plasma des raies rouges de l'Argon issues des niveaux 4p. L'étude de ces décharges présente de l'intérêt sur le plan tant fondamental qu'appliqué (amorçage des décharges à haute intensité, caractérisation des régions périphériques des arcs électriques, lasers à excimers).
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Suprani, Enrico. "Direttiva PED: iter tecnico-procedurale ed elementi di analisi di rischio per la valutazione di conformità delle attrezzature e degli insiemi a pressione." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2013. http://amslaurea.unibo.it/5414/.
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Il presente elaborato ha ad oggetto la direttiva PED (Pressure Equipment Directive) relativa agli apparecchi a pressione.
Tale norma è stata recepita in Italia con il D.Lgs. n. 93/2000 ed è entrata in vigore definitivamente nel 2002. Essa è finalizzata alla libera circolazione delle attrezzature a pressione nella comunità europea e ne disciplina la progettazione, la costruzione, l'equipaggiamento e l'installazione in sicurezza, definendo per ciascuna delle fasi sopra elencate quali siano i documenti da presentare, gli accorgimenti da rispettare e i controlli a cui sottostare.
Il presente lavoro di tesi, svolto presso lo stabilimento di Ravenna di ENI Versalis, ha avuto l’obiettivo di individuare i punti di contatto fra quanto richiesto dalla direttiva PED e quanto solitamente emerge dall’applicazione delle tecniche per l’analisi di rischio, degli standard internazionali e aziendali e delle norme di buona tecnica. Il risultato del lavoro consiste nella definizione di un iter tecnico-procedurale standardizzato ad uso dell’utilizzatore delle attrezzature a pressione tramite la quale l’azienda possa procedere alla compilazione delle Note Tecniche destinate al fabbricante delle attrezzature stesse, secondo quanto richiesto dalla direttiva. Tali Note Tecniche devono contenere le indicazioni relative ai valori progettuali di temperatura e pressione e ai Requisiti Essenziali di Sicurezza (RES) che devono essere soddisfatti, permettendo così al fabbricante di poter svolgere una corretta analisi di rischio e all’utilizzatore di ottenere la massima sicurezza negli impianti.
L’elaborato è strutturato come segue. Dopo il Capitolo 1, avente carattere introduttivo, nel Capitolo 2 vengono illustrate le principali novità introdotte dalla direttiva PED e descritti i punti cardine della procedura di valutazione della conformità richiesta per le attrezzature a pressione. Nel Capitolo 3 viene esaminata l’integrazione della direttiva PED con la direttiva Macchine e la direttiva ATEX. Nel Capitolo 4 sono descritte le principali tecniche di analisi di rischio che possono essere utilizzate per rispondere ai Requisiti Essenziali di Sicurezza (RES) richiesti in fase di compilazione della Nota Tecnica. Nel Capitolo 5 si fornisce una descrizione dettagliata dell’iter tecnico-procedurale messo a punto per la valutazione di conformità delle attrezzature e degli insiemi a pressione. Nel Capitolo 6 vengono illustrati ad uno ad uno i punti che devono essere presenti in una Nota Tecnica, ciascuno dei quali costituisce un Requisito Essenziale di Sicurezza. Nel Capitolo 7 viene approfondito uno dei Requisiti più critici, l’incendio esterno. Infine nel Capitolo 8 sono riportate le considerazioni conclusive.
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Venturi, Alberto. "Implementazione di un sistema intelligente per la modellazione di processo con un'applicazione alla pressofusione." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2019.
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Questa tesi di laurea si pone come obbiettivo l’implementazione di un sistema di reti neurali artificiali per ottimizzare la modellazione del processo di colata sotto pressione di alluminio.
L’analisi svolta sul particolare realizzato in FAR ha permesso di evidenziare tutti i parametri e le eventuali problematiche che intervengono nel processo, delineando dipendenze e indipendenze dei fattori in gioco; in particolare, utilizzando il software di modellazione di processo ProCast, si è analizzato il solo problema della presenza di microporosità da ritiro in relazione alla variazione della temperatura iniziale del metallo fuso. L'utilizzo di tali informazioni e l'ideazione di descrittori geometrici in grado di semplificare i fenomeni fisici in atto hanno condotto all'allenamento di un sistema intelligente di reti neurali artificiali feed-forward. Successive prove hanno condotto all'ottimizzazione dell'architettura e delle caratteristiche della rete neurale per questo specifico caso di studio.
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Carnide, Guillaume. "Procédé de dépôt couplant un réacteur-injecteur et un plasma basse pression : vers le dépôt de couches minces multifonctionnelles pour l'aéronautique." Thesis, Toulouse 3, 2019. http://www.theses.fr/2019TOU30321.
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Dans l'industrie aéronautique, la glace se formant sur la surface des avions au sol ou en vol est un problème majeur. Afin de résoudre ce problème, une solution passive pourrait être employé par un revêtement antigivre durable. Un matériau permettant d'obtenir ses propriétés tout en étant durable sur des avions est le nanocomposite. Le nanocomposite est un revêtement dans lequel des nanoparticules sont intégrées dans une matrice et permet de coupler les propriétés pour être multifonctionnel. Cette thèse développe et étudie un nouveau, sécurisé et flexible procédé pour la formation de revêtement nanocomposite. En effet, ce procédé combine un réacteur-injecteur et un procédé plasma. Le réacteur-injecteur est un injecteur de gaz/liquide dans lequel se forme des petites nanoparticules de ZnO (Ø : < 10 nm) par l'hydrolyse d'un précurseur organométallique. Dans cette thèse, nous montrons que le contrôle des réactifs chimiques et des paramètres d'injection permet la formation de nanoparticules non-agrégée avec une faible quantité d'agent stabilisant. Pour la formation de revêtement nanocomposite, le réacteur-injecteur est couplé avec un procédé plasma basse-pression. Ce procédé plasma interagit avec le précurseur de matrice injecté pour former la matrice recouvrant les nanoparticules. L'effet de l'injection pulsée sur le plasma basse pression a été étudié pour comprendre les mécaniques de transport des nanoparticules au cours du procédé. De plus, ce procédé permet de limiter les interactions entre l'utilisateur et les nanoparticules de leur synthèse à leur incorporation dans le revêtement. La caractérisation de ces revêtements montre de petites nanoparticules dispersées de façon homogène avec la combinaison de propriétés hydrophobes et de résistance à l'abrasion. Au final, ce procédé est montré comme flexible car en fonction des précurseurs utilisés, il est possible de former différents types de nanoparticules (CuOx, WOx...) ou de matrice (a-CH, SiOx)In the aeronautic industry, icing appears over the airplane's surfaces at ground or in flight is a major problematic. One solution could be a passive solution by the use of antiicing coatings. One material wich could allow these properties and be sustainable for aeronautics is the nanocomposite. Nanocomposite (NC), i.e. coatings with nanoparticles (NP) embedded in a matrix develop multi-functional properties. This thesis develops and studies a novel, flexible and secure approach for the formation of nanocomposite coatings. Indeed, this process combines a reactor-injector and a plasma process. The reactor-injector is a liquid/gaz injection device in which is form small ZnO NP (Ø : < 10 nm) from the hydrolysis of an organometallic precursor. Hence, the control of the chemical reagents and the injection's parameters allows to form non-aggregates NP with small quantity of stabilizing agent. This technology called "reactor-injector" has been patented. For the formation of the nanocomposite coatings, the reactor-injector is combined with a low pressure plasma process. The plasma process will interact with the matrix precursor injected to form an embedment coating for the nanoparticles. The impact of the pulsed pressure injection over the low pressure plasma has been studied to understand the mechanics of the NP transport during the process. Thus, this process permits to limit the interaction between the user and the nanoparticles from their synthesis to their embedment. The characterisation of these coatings shows well dispersed and small ZnO nanoparticles with the combination of hydrophobicity and abrasion-resistant properties. Finally, this process is flexible and depending on the precursors allows the formation of differents NP (CuOx, WOx...) or matrix (a-CH,SiOx)
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Dinh, Thi hong nhung. "Etudes technologiques de composants PDMS pour applications biomédicales : développement de capteurs souples de pression par transfert de film." Thesis, Université Paris-Saclay (ComUE), 2015. http://www.theses.fr/2015SACLS127/document.
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Les travaux de thèse portent sur le développement de méthodologies d'élaboration de dispositifs à base de polymères PDMS, destinés à des applications médicales. Ce travail s'appuie sur deux volets applicatifs : le développement de matrices de micro-capteurs capacitifs souples portables destinées à la mesure de champs de pression dans un contexte de suivi d'appuis du corps humain, et le développement d'une technique de collage réversible de composants PDMS dans une application de laboratoire sur puce en micro-fluidique. Dans ces travaux, les propriétés mécaniques du PDMS sont déterminées expérimentalement et à l'aide de modélisations numériques, afin d'identifier les éléments essentiels du dimensionnement des micro-capteurs capacitifs. Différents types de micro-capteurs de pression souples sont réalisés par un procédé de microfabrication à transfert de films. Ce procédé est optimisé à chacune de ses étapes afin d'obtenir un procédé fiable et reproductible. Les caractérisations électromécaniques montrent que les capteurs fabriqués sont opérationnels et adaptés aux applications médicales visées. Les capteurs de pression normale ont une variation de capacité de 3 à 17 % à 10 N - 300 kPa, adaptée à une application dentaire. Les capteurs à trois axes de sensibilité ont une résolution spatiale de 25 mm2, et une sensibilité de 4 % à 3 N en compression et 1,4 % par Newton en cisaillement pur, et sont adaptés à une application de mesure de la pression plantaire destinée à l'analyse de la marche et la détection des hyper-appuis. Par ailleurs, deux méthodes différentes permettant le collage réversible de composants PDMS sont développées. Les dispositifs microfluidiques fabriqués avec ces méthodes peuvent être utilisés avec jusqu'à 5 cycles de collage/décollage, et travailler à débit élevé (500 µL/min, correspondant à une pression de 148 kPa). Les méthodologies développées dans ces travaux ouvrent la voie à l'élaboration de dispositifs à base de PDMS performants et optimisés pour répondre à des cahiers des charges exigeants pour des applications biomédicales cibléesThis thesis focuses on the development of methodologies dedicated to the development of PDMS-based devices, which are required in medical applications. Two objective applications are considered in this work: i) the development of wearable flexible micro-sensors arrays for measuring pressure fields on human body and ii) the development of a reversible bonding technique of PDMS components dedicated to microfluidic chips. In this work, the mechanical properties of PDMS are determined using experiments and computations; they allow identifying the essential elements of the design of capacitive micro-sensors. The manufacturing process is reliable and reproducible, and different types of flexible pressure sensor have been fabricated by a film transfer process. Electromechanical characterizations show that the fabricated sensors are fully operational and suitable for the intended applications. Normal pressure sensors have a capacitance change ranging from 3 to 17% under a 10 N - 300 kPa - load, which is suitable for dental applications. Fabricated triaxial sensor arrays have a spatial resolution of 25 mm2, and a sensitivity of 4% under 3 N load in compression, and 1.4% / N under shear. These features are suitable for plantar pressure measurements required in gait analyses or for the detection of over-pressures. Besides, two different process methods for the reversible bonding of PDMS devices are developed. The microfluidic devices fabrcitated with these methods can be used within up to 5 “bonding & peeling off” cycles, and can be working at high microfluidic flows (500 µL / min, corresponding to a pressure of 148 kPa). The methodologies developed in these works open the way to the design and fabrication of PDMS-based devices suitable for demanding biomedical applications
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Robert, Sébastien. "Conception d'un reacteur dynamique de depollution par procede plasma hors equilibre a pression atmospherique a l'aide d'une molecule modele." Paris 6, 2001. http://www.theses.fr/2001PA066364.
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La conception d'un reacteur dynamique de depollution a l'aide d'une molecule modele par procede plasma hors equilibre a pression atmospherique a ete l'objectif de notre travail, en considerant le role de l'oxygene comme l'etape cle de notre demonstration. La qualification des phenomenes physiques, hydrodynamiques et reactionnels, qui s'etablissent conjointement dans le reacteur a decharges impulsionnelles, constituent les differents points que nous avons developpes lors de cette etude. L'etude a debute par la caracterisation hydrodynamique du reacteur pointe - plan par anemometrie laser doppler, notamment des phenomenes d'ecoulement et de recyclage. En les reliant aux caracteristiques electriques, nous avons mis en evidence le sequencage de l'ecoulement d'un point de vue temporel. Dans un deuxieme temps, l'acetaldehyde ch 3cho a ete employe comme molecule modele en presence d'air, afin d'effectuer la caracterisation physico-chimique du reacteur plasma par la technique gc/ms. La validation d'un bilan matiere precis a ete obtenue en considerant les reactions en phase homogene et en phase heterogene, ainsi que les especes formees notamment les r-no x. La nature des produits formes a souligne le role de l'oxygene dans les processus d'oxydation et d'attaque de la molecule d'acetaldehyde. Afin d'elucider les mecanismes reactionnels en phase homogene, nous avons eu recours a la technique de marquage isotopique a l'oxygene 1 8o et au deuterium. Les echanges d'atomes d'oxygene et leur repartition dans les produits ont demontre le role des radicaux oxygenes (oh ,̱ co ,̱ o )̱ tandis que le deuterium a permis de souligner la preponderance de la fonction methyle. Enfin, a partir de la diversite des molecules obtenues par traitement plasma, la modelisation statique thermodynamique et cinetique a permis d'apprehender les compositions et le temps de sejour necessaire a l'obtention d'especes stables alors que le code de calcul dynamique fluent a confirme l'ecoulement observe.
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Essoltani, Abdelaziz. "Modelisation d'un plasma d'oxygene homogene et stationnaire a la pression atmospherique 2000 k <- t <- 15000 k." Toulouse 3, 1988. http://www.theses.fr/1988TOU30104.
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Modele radiatif-collisionnel applique a un plasma d'oxygene contenant a la fois des especes atomiques (o**(-), o**(+), o) et des especes moleculaires (o**(-)::(2), o::(2), o**(+)::(2)). Calcul de la composition du plasma a la pression atmospherique compte tenu des radiations. Description d'un modele concu pour decrire un plasma completement dissocie, applicable lorsque la temperature depasse 7500 k. Etude d'un plasma contenant a la fois des especes atomiques et moleculaires. Les calculs ont ete faits, dans un premier temps dans un milieu monotherme (theta ::(e)=theta ::(g)). Dans un second temps, on a considere une temperature des particules lourdes comprises entre theta ::(e) et theta ::(e)/5
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Saffar, Florence. "Etude de la consolidation interpli de stratifiés thermoplastiques PEKK/fibres de carbone en conditions de basse pression." Thesis, Ecole nationale supérieure Mines-Télécom Lille Douai, 2019. http://www.theses.fr/2019MTLD0008.
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De nouveaux modes d’élaboration de pièces composites à matrice thermoplastique sont actuellement étudiés, par le milieu aéronautique, afin de remplacer le procédé autoclave, qui est coûteux et limite les cadences de production. Ainsi cette thèse a pour objet l’étude des phénomènes de consolidation interpli dans le cas d’élaborations basse pression. Dans ce but, deux systèmes de fabrication sont développés : l’un en étuve et l’autre sur plateau chauffant. Ces deux dispositifs permettent à la fois de définir les paramètres procédés optimaux pour assurer une bonne consolidation interpli, et de réaliser un suivi d’élaboration grâce à des mesures de variations d’épaisseur, de gradient thermique et de pertes de charges. Les matériaux utilisés sont des pré-imprégnés unidirectionnels thermoplastiques haute performance (PEKK/fibres de carbone). Une partie de ce travail est consacrée à la caractérisation de la matrice, peu étudiée dans la littérature, et à l’influence des paramètres matériau sur la qualité de l’élaboration. Deux événements de consolidation interpli sont identifiés au cours de cette étude : l’un à la température de transition vitreuse (Tg) et l’autre à la température de fusion (Tm). Ils sont respectivement associés aux phénomènes de mise en contact des plis et d’écoulement de l’ensemble fibres/matrice. Une simulation de ces étapes de consolidation est également proposée. La mise en contact des plis est notamment décrite par une évolution de la résistance thermique de contact et par un aplanissement des aspérités de surface. L’écoulement à Tm permettant la réduction du taux de porosité aux interplis est, lui, modélisé à partir des propriétés rhéologiques du matériau déterminées expérimentalementNew manufacturing technologies of thermoplastic composite parts are being developed in order to replace the autoclave molding which requires higher manufacturing costs and longer processing time. In this context, the subject of this thesis is the study of the vacuum-bag-only (VBO) consolidation for thermoplastic (PEKK)/carbon fibers laminates. In this work, two kinds of heating method are considered: the one in an oven and the other on a heating plate. Firstly, we investigate the influence of the process on the consolidation quality. The second step of this thesis is to understand and interpret the interlaminar consolidation phenomena. For that purpose, an in-situ monitoring system has been developed to record the evolution of the laminate thickness, of the temperature gradient and of pressure losses during the whole consolidation cycle. Using these systems two major consolidation phenomena have been identified. The first one takes place at the glass transition temperature and corresponds to the establishment of intimate contact between the adjacent layers. The second one happens at the melting temperature and is associated with the flow of the molten material. The final third step is the integration of these consolidation phenomena into a FEM model. The intimate contact establishment is simulated by an improvement on the thermal contact resistance at the interlayers and by a flattening of the prepreg asperities. The melted composite behavior is described by a Carreau fluid which parameters have been experimentally identified
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Boyer, Philippe. "Gravure de l'aluminium en plasmas halogénés basse pression-influence du facteur d'aspect." Toulouse, INSA, 1993. http://www.theses.fr/1993ISAT0002.
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Ce travail s'inscrit dans le cadre du developpement des filieres de fabrication de circuits integres prototypes cmos 0,5 et 0,35 m au centre national d'etudes des telecommunications de meylan (france telecom), et plus precisement de procedes de gravure de l'aluminium. Dans un premier temps, l'auteur presente les specificites de la gravure de l'aluminium, et montre les limites des reacteurs de gravure classique, fonctionnant dans un regime de pression intermediaire (100 mtorr). Cela a conduit au choix d'un reacteur de gravure basse pression (reacteur triode a confinement magnetique, 1 mtorr) dont les caracteristiques ont ete etudiees. L'auteur presente par la suite la demarche experimentale qui a permis de mettre au point un procede de gravure aluminium basse pression, utilisant un melange brome-chlore. Le procede issu de ce travail a demontre sa fiabilite et sa large fenetre de fonctionnement puisqu'il est utilise pour graver differentes metallisations a base d'aluminium (alliages, multicouches). L'apport plus specifique a la comprehension des mecanismes de gravure de l'aluminium a porte sur l'etude de la variation de la vitesse de gravure en fonction du facteur d'aspect. L'influence de la conductivite du masque, des parametres plasma tels que flux d'ions et flux de neutres, et de l'aspect du motif (trou, tranchee,. . . ) a ete etudiee. Ces resultats ont permis de developper un modele base sur l'ecrantage des flux; cet ecrantage est a la fois de nature geometrique (flux d'ions et de neutres) et electrique (flux d'ions)
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Gonzalez, Gomez Jesus Antonio. "Transitions optiques dans gaas sous haute pression : application a la transition de phase cubiques-orthorhombique." Paris 6, 1988. http://www.theses.fr/1988PA066264.
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Mesure du coefficient d'absorption a 300 k et pour des pressions jusqu'a 13 gpa et comparaison avec les modeles d'elliott-toyozawa a basse pression et de dumke a haute pression. Les variations avec la pression, des bandes interdites directes et indirectes est deduite. Au dela des 13 gpa l'etude de la transition de phase structure blende-orthorhombique a permis d'etablir le domaine de stabilite de la phase blende. L'etude de la photo conductivite sous pression a permis l'estimation de la longueur de diffusion et de la duree de vie des porteurs photo excites
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Himber, Jacques. "Caractérisation des récepteurs adrénergiques des procès ciliaires application à l'étude in vivo et in vitro d'antagonistes beta et d'agonistes alpha actifs sur la pression intraoculaire /." Grenoble 2 : ANRT, 1988. http://catalogue.bnf.fr/ark:/12148/cb37614298n.
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Deumier, François. "Formulation et déshydratation de viande de volaille par immersion. Étude des transferts de matière à pression atmosphérique et sous vide." Phd thesis, ENSIA (AgroParisTech), 2000. http://tel.archives-ouvertes.fr/tel-00709458.
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L'application du procédé de Déshydratation-Imprégnation par Immersion (DII) dans des solutions ternaires (eau, NaCl, sirop de glucose) à basse température a été proposée pour la transformation de la viande de dinde. La connaissance des propriétés des solutions utilisées conjuguée à celle des transports de matière entre le produit et la solution ont permis de dégager un domaine d'applications rationnelles du procédé de DII à la viande de dinde, en fonction des caractéristiques finales du produit transformé souhaité. Afin de s'affranchir en partie de la lenteur des mécanismes diffusifs qui régissent les transports de matière en DII et également d'élargir la gamme potentielle des produits pouvant être obtenus par immersion de viande de volaille dans des solutions concentrées, le procédé d'Immersion sous Vide Pulsé dans une solution saturée en sel a été proposé. Il s'agit d'immerger le produit dans une solution et de le soumettre à un traitement alternant des phases sous pression résiduelle et des phases à pression atmosphérique. L'IVP a pour effet une forte augmentation du gain en sel et une diminution de la perte en eau, ce qui a pour conséquence une augmentation du rendement massique. Les principales variables de commande de ce procédé ont été identifiées et leurs effets sur les transports de matière ont été quantifiés. Cette étude a montré l'importance de la structure de la viande et de la présence de gaz occlus et/ou dissous dans la viande. Les essais conduits sur viande et sur gels modèles ont permis de proposer un modèle de représentation des phénomènes intervenant dans les transports de matière en IVP. Ainsi, le traitement sous vide permet-il de dégazer les pores de la viande et la remise à pression atmosphérique se traduit par une infiltration de solution dans ces pores, les gaz encore présents dans ces pores étant alors comprimés. Cette infiltration se traduit également par une augmentation de la surface d'échanges entre la viande et la solution. Cependant, la solution infiltrée est très rapidement diluée et cette dilution diminue notablement, voire inverse, les transports d'eau. Enfin, le séquençage des opérations de DII et/ou d'IVP a été proposé pour obtenir plus rapidement certains produits et pour formuler d'autres produits, impossibles à obtenir par DII dans des conditions satisfaisantes.
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Montilha, Fernanda Silveira. "Identificação de um modelo constitutivo para simulação computacional do processo de prensagem a frio de um material refratário sílico-aluminoso." Universidade Federal de São Carlos, 2016. https://repositorio.ufscar.br/handle/ufscar/8419.
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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)
One of the methods for the processing of refractory material is cold pressing of the powder material, followed by sintering. Heterogeneous distribution of density can occur in the green compact during pressing because of the friction between the particles of the material and the pressing tools, that may hinder the sintering step. In this context, the simulation of the pressing process constitutes an important tool for the study and improvement of this step, to obtain green compacts with good microstructural homogeneity and also analyze the pressing tools to optimize its design in industrial applications. The identification of a constitutive model to represent the powder material is required to perform the simulation and it is the most complex step. The Drucker-Prager/Cap model implemented in the commercial software of finite elements, AbaqusTM, is suitable primarily for soil compaction study and is able to simulate the mechanical compaction of particulate materials. The parameters of this model have been obtained for a silico-aluminous refractory by a combination of simple, diametrical and hydrostatic compression tests. In studies available in the literature, the material models are partially identified, and in many cases, inadequate simplifications are applied. This study aimed to identify the parameters of the material model more precisely using the digital images correlation technique in the mechanical tests, which enabled a greater understanding of the yielding mechanisms and the achievement of data not obtained by conventional techniques. This methodology allowed the identification of a constitutive model and it was valitaded by the good agrrement between experimental results and those obtained in computer simulations, applied to a uniaxial case followed by isostatic pressing.
Um dos métodos para o processamento de materiais refratários é a prensagem a frio do material particulado, seguida da etapa de sinterização. Durante a prensagem pode ocorrer uma distribuição heterogênea de densidades no compacto verde, causada pelo atrito entre as partículas do material e as paredes da cavidade do ferramental de prensagem, que pode prejudicar a etapa de sinterização. Neste contexto, a simulação computacional do processo de prensagem constitui-se em uma ferramenta importante para o estudo e aperfeiçoamento desta etapa, visando obter compactos verdes com boa homogeneidade microestrutural e também analisar as solicitações no ferramental a fim de otimizar seu projeto em aplicações industriais. A identificação de um modelo constitutivo que represente o material é necessária para realização das simulações e trata-se da etapa de maior complexidade. O modelo de Drucker-Prager/Cap implementado no software comercial de elementos finitos AbaqusTM é adequado principalmente para o estudo de compactação de solos e é capaz de simular o adensamento mecânico de materiais particulados. Os parâmetros deste modelo para um material refratário sílico-aluminoso foram identificados pela combinação de ensaios de compressão simples, diametral e hidrostática. Em trabalhos disponíveis na literatura, os modelos de material são parcialmente identificados e, em muitos casos, são aplicadas simplificações inadequadas. O presente estudo visou uma identificação mais precisa dos parâmetros do modelo de material, uma vez que os ensaios mecânicos foram auxiliados pela técnica de correlação de imagens digitais, que possibilitou a avaliação mais profunda dos mecanismos de escoamento e a obtenção de dados não alcançados por técnicas convencionais. Essa metodologia permitiu a identificação do modelo constitutivo e a validação consistiu na comparação entre resultados experimentais e os obtidos em simulações computacionais, aplicados a um caso de prensagem uniaxial seguida de prensagem isostática, apresentando boa concordância.
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Silva, Késia Filadélfia Dionizio. "Efeito do processo ECAP sobre a microestrutura e as propriedades mecânicas da liga Ti-35Nb-0,15Si e do Ti CP." Pós-Graduação em Ciência e Engenharia de Materiais, 2017. http://ri.ufs.br/jspui/handle/riufs/7204.
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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPESThis work investigated the effect of different types of homogenization on the microstructure and the cold deformation behavior of Ti-35Nb-0,15Si alloy. Homogenization was performed under two conditions. Condition 1: treatment in ambient air at 1000 °C for 8, 24, 48, 72, 96 and 120 hours. Condition 2: treatment in argon atmosphere at 1000 °C for 8 hours. For the cold deformation study samples of the Ti-35Nb-0,15Si alloy and samples of Ti CP were deformed by ECAP with up to 8 passes, using the routes A and BC in a matrix with angle of intersection between the channels of Φ = 120º. The microstructural characterization was performed in the internal and external regions with the aid of optical microscopy, scanning electron microscopy and X-ray diffractograms. Vickers microhardness measurements were performed to evaluate the changes caused by deformation. In the ambient air atmosphere the samples showed the presence of the oxide layer influencing the hardness and the level of cold deformation. With the deformation of Ti-35Nb-0,15Si by ECAP it was possible to refine the structure and increase the hardness with increasing the number of passes. XRD analysis showed the presence of the α” phase induced by deformation. With the Ti CP deformed by ECAP, it was possible to analyze the microstructural evolution throughout the sample.
Este trabalho investigou o efeito de diferentes tipos de homogeneização sobre a microestrutura e o comportamento em deformação a frio da liga Ti-35Nb-0,15Si. A homogeneização foi realizada em duas condições. Condição 1: tratamento em atmosfera de ar ambiente na temperatura 1000 °C por 8, 24, 48, 72, 96 e 120 horas. Condição 2: tratamento em atmosfera inerte de argônio de 1000 °C por 8 horas. Para o estudo de deformação a frio, amostras da liga Ti-35Nb-0,15Si e amostras de Ti CP foram deformadas via ECAP com até 8 passes, utilizando as rotas A e BC numa matriz com ângulo de intersecção entre os canais de Φ = 120º. A caracterização microestrutural foi realizada nas regiões internas e externas com o auxílio de microscopia óptica, microscopia eletrônica de varredura e difratogramas de raios-X. Medidas de microdureza Vickers foram realizadas para avaliar as mudanças ocasionadas pela deformação. Em atmosfera de ar ambiente as amostras apresentaram a presença da camada de óxido influenciando na dureza e no nível de deformação a frio. Com a deformação de Ti-35Nb-0,15Si por ECAP foi possível refinar a estrutura e aumentar a dureza com o aumento do número de passes. A análise de DRX mostrou a presença da fase α’’ induzida por deformação. Com o Ti CP deformado por ECAP foi possível analisar a evolução microestrutural ao longo da amostra.
São Cristóvão, SE
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Schneider, Christine. "Etude du procede d'elaboration de composites a matrice metallique par inflitration moyenne pression. : Elaboration et caracterisation microstructurale et mecanique du composite unidirectionnel A9/Al203." Lyon, INSA, 1994. http://www.theses.fr/1994ISAL0071.
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Ce travail de thèse s'est articule autour de deux pôles principaux: la mise au point de l'élaboration par infiltration moyenne pression appliquée aux composites a matrice métallique et la caractérisation microstructurale et mécanique du composite unidirectionnel A9/Al2O3 obtenu par ce procédé. La première phase de cette étude a été consacrée a la conception de moules et de préformés adaptés à ce nouveau procédé puis à la détermination de conditions d'élaboration pertinentes. La deuxième phase a consiste à évaluer l'influence de ces conditions sur la qualité du matériau par une étude de la microstructure (défauts d'élaboration et répartition du renfort dans la matrice) et des propriétés mécaniques. Ces dernières ont été déterminées dans le cas d'une sollicitation en traction parallèlement et perpendiculairement aux fibres. Les résultats concernant l'ensemble des caractéristiques mécaniques du matériau ont été interprétées a partir de modèles théoriques existantsThis study dealt with : the optimization of pressure infiltration casting elaboration for Metal Matrix Composites and the microstructural and mechanical characterization of the unidirectionnal A9/ Al203 composites obtained with this process. In the first part of this study, moulds were conceived and preforms were manufactured to be adapted to the new processing system. Than the optimal elaboration conditions were determined. The second part consisted to evaluate the influence of these conditions on the material quality with a study of the microstructure (elaboration defects and fibres repartition in the matrix) and of the mechanical properties. This properties were determined with axial and transverse tension tests. The result of the whole mechanical properties of the composite were interpreted on the basis of theoretical existing models
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Hashemi, Sanatgar Razieh. "FDM 3D printing of conductive polymer nanocomposites : A novel process for functional and smart textiles." Thesis, Lille 1, 2019. http://www.theses.fr/2019LIL1I052/document.
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Le but de cette étude est d’exploiter les fonctionnalités des nano-Composites Polymères Conducteurs (CPC) imprimés en utilisant la technologie FDM (modélisation par dépôt de monofilament en fusion) pour le développement de textiles fonctionnels et intelligents. L’impression 3D présente un fort potentiel pour la création d’une nouvelle classe de nanocomposites multifonctionnels. Par conséquent, le développement et la caractérisation des polymères et nanocomposites fonctionnels et imprimables en 3D sont nécessaires afin d’utiliser l’impression 3D comme nouveau procédé de dépôt de ces matériaux sur textiles. Cette technique introduira des procédés de fonctionnalisation de textiles plus flexibles, économes en ressources et très rentables, par rapport aux procédés d'impression conventionnels tels que la sérigraphie et le jet d'encre. L’objectif est de développer une méthode de production intégrée et sur mesure pour des textiles intelligents et fonctionnels, afin d’éviter toute utilisation d'eau, d'énergie et de produits chimiques inutiles et de minimiser les déchets dans le but d’améliorer l'empreinte écologique et la productivité. La contribution apportée par cette thèse consiste en la création et la caractérisation de filaments CPC imprimables en 3D, le dépôt de polymères et de nanocomposites sur des tissus et l’étude des performances en termes de fonctionnalité des couches de CPC imprimées en 3D. Dans un premier temps, nous avons créé des filaments de CPC imprimables en 3D, notamment des nanotubes de carbone à parois multiples (MWNT) et du noir de carbone à haute structure (Ketjenblack) (KB), incorporés dans de l'acide polylactique (PLA) à l'aide d'un procédé de mélange à l'état fondu. Les propriétés morphologiques, électriques, thermiques et mécaniques des filaments et des couches imprimées en 3D ont été étudiées. Deuxièmement, nous avons déposé les polymères et les nanocomposites sur des tissus à l’aide d’une impression 3D et étudié leur adhérence aux tissus. Enfin, les performances des couches de CPC imprimées en 3D ont été analysées sous tension et force de compression appliquées. La variation de la valeur de la résistance correspondant à la charge appliquée permet d’évaluer l'efficacité des couches imprimées en tant que capteur de pression / force. Les résultats ont montré que les nanocomposites à base de PLA, y compris MWNT et KB, sont imprimables en 3D. Les modifications des propriétés morphologiques, électriques, thermiques et mécaniques des nanocomposites avant et après l’impression 3D nous permettent de mieux comprendre l’optimisation du procédé. De plus, différentes variables du procédé d’impression 3D ont un effet significatif sur la force d'adhérence des polymères et des nanocomposites déposés sur les tissus. Nous avons également développé des modèles statistiques fiables associés à ces résultats valables uniquement pour le polymère et le tissu de l’étude. Enfin, les résultats démontrent que les mélanges PLA/MWNT et PLA/KB sont de bonnes matières premières piézorésistives pour l’impression 3D. Elles peuvent être potentiellement utilisées dans l’électronique portable, la robotique molle et la fabrication de prothèses, où une conception complexe, multidirectionnelle et personnalisable est nécessaireThe aim of this study is to get the benefit of functionalities of fused deposition modeling (FDM) 3D printed conductive polymer nanocomposites (CPC) for the development of functional and smart textiles. 3D printing holds strong potential for the formation of a new class of multifunctional nanocomposites. Therefore, development and characterization of 3D printable functional polymers and nanocomposites are needed to apply 3D printing as a novel process for the deposition of functional materials on fabrics. This method will introduce more flexible, resource-efficient and cost-effective textile functionalization processes than conventional printing process like screen and inkjet printing. The goal is to develop an integrated or tailored production process for smart and functional textiles which avoid unnecessary use of water, energy, chemicals and minimize the waste to improve ecological footprint and productivity. The contribution of this thesis is the creation and characterization of 3D printable CPC filaments, deposition of polymers and nanocomposites on fabrics, and investigation of the performance of the 3D printed CPC layers in terms of functionality. Firstly, the 3D printable CPC filaments were created including multi-walled carbon nanotubes (MWNT) and high-structured carbon black (Ketjenblack) (KB) incorporated into a biobased polymer, polylactic acid (PLA), using a melt mixing process. The morphological, electrical, thermal and mechanical properties of the 3D printer filaments and 3D printed layers were investigated. Secondly, the performance of the 3D printed CPC layers was analyzed under applied tension and compression force. The response for the corresponding resistance change versus applied load was characterized to investigate the performance of the printed layers in terms of functionality. Lastly, the polymers and nanocomposites were deposited on fabrics using 3D printing and the adhesion of the deposited layers onto the fabrics were investigated. The results showed that PLA-based nanocomposites including MWNT and KB are 3D printable. The changes in morphological, electrical, thermal, and mechanical properties of nanocomposites before and after 3D printing give us a great understanding of the process optimization. Moreover, the results demonstrate PLA/MWNT and PLA/KB as a good piezoresistive feedstock for 3D printing with potential applications in wearable electronics, soft robotics, and prosthetics, where complex design, multi-directionality, and customizability are demanded. Finally, different variables of the 3D printing process showed a significant effect on adhesion force of deposited polymers and nanocomposites onto fabrics which has been presented by the best-fitted model for the specific polymer and fabric
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Masmoudi, Amal. "Modélisation et développement expérimental du procédé de fabrication additive par fusion laser sélective d'un lit de poudre métallique : influence de la pression de l'atmosphère." Thesis, Belfort-Montbéliard, 2016. http://www.theses.fr/2016BELF0287/document.
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Le procédé de fusion sélective par laser (SLM) d’un lit de poudre métallique, est un procédé de fabrication additive qui permet de fabriquer des pièces de forme complexe directement à partir d’un fichier CAO en passant par la fusion totale de couches de poudre déposées successivement. Au cours du procédé SLM l’apport d’énergie du laser à la cible engendre de nombreux cycles thermiques: fusion – vaporisation – solidification. Dans ce contexte, cette thèse a pour double objectif :1) une meilleure caractérisation et compréhension des phénomènes qui se produisent lors de l’interaction du faisceau laser avec la poudre et le bain de métal fondu à l’aide d’essais et 2) le développement d’un modèle numérique prenant en compte les phénomènes de fusion et de vaporisation de la matière ainsi que à la présence du gaz environnant à l’intérieur de la chambre de fabrication.Dans un premier temps, en considérant des géométries simples (cordons et surfaces) en acier inoxydable 316L, on a étudié l’interaction faisceau laser - lit de poudre / bain liquide métallique par différentes méthodes de diagnostics (spectrométrie, calorimètre, …) pour comprendre la nature et le rôle de la vapeur métallique générée au cours du procédé. Les résultats ont montré que cette vapeur est sans effet sur la transmission de l’énergie du laser à la matière au cours du procédé SLM. Par contre, elle conduit à la formation de condensats et peut aussi entrainer des gouttelettes de métal fondu.Ces analyses ont permis, dans un second temps, de développer un modèle numérique qui a pour objectif principal de caractériser l’influence de la pression du milieu environnant sur le processus de fusion du lit de poudre par le faisceau laser. Des paramètres caractérisant l’évolution des propriétés physiques du matériau et du milieu gazeux en fonction de la température et de la pression ont été intégrés dans les bases de données du modèle. Ces paramètres physiques du matériau ont été déterminés à partir de la littérature et d’autres ont été obtenus empiriquement à l’aide de mesures expérimentales spécifiques.Ce modèle numérique a été utilisé pour traiter le sujet principal de la thèse, à savoir celui de l’effet de la pression. Le modèle a permis de préciser les phénomènes physiques inhérents à la variation de la pression. Des manipulations expérimentales ont permis de vérifier la pertinence des données du modèle numérique proposéThe selective laser melting process (SLM) of a metallic powder bed is an innovative process that allows the manufacturing of complex shape parts directly from a CAD file via a complete melting of powder layers deposited successively. During the SLM process, the high laser energy density creates many thermal cycles: melting - vaporization - solidification.The purpose of this work was: 1) to better characterize and understand experimentally the phenomena that occur during the laser beam - powder / molten metal pool interaction and 2) to develop a numerical model taking into account the phenomena of melting and vaporizing of the material and the presence of the surrounding gas in the build chamber.In a first time, considering simple geometries (tracks and surfaces) and 316L stainless steel as material, we studied the interaction between the laser beam, the powder bed and the liquid metal pool using several experimental techniques (spectrometry, calorimetry, ...) in order to understand the nature and the role of the metal vapor generated during the process. The results showed that the vapor has no effect on the transmission of the laser beam energy to the material during the SLM process. Meanwhile it leads to the deposition of condensed vapor and also drag some molten metal droplets.In a second time a numerical model was developed to determine the influence of the pressure of the surrounding environment on the melting process of a powder bed by a laser beam. Parameters characterizing the evolution of the physical properties of the material and of the gaseous medium according to the temperature and pressure were incorporated into the model database. Some material parameters were determined from the literature and others were obtained empirically using specific experimental measurements.Finally, this numerical model, complementing experimental results, was used to treat the main subject of the thesis which is the effect of the surrounding pressure on the SLM process. The model helped to clarify the physical phenomena provided by the change in the pressure level and its validity was checked through experimental measurements
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NARDARI, CHRISTIAN. "Etude des relations entre parametres de fabrication, caracteristiques mecaniques et conception de pieces composites structurales elaborees par injection a basse pression sur preforme (procede rtm)." Toulouse 3, 1999. http://www.theses.fr/1999TOU30074.
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Une methodologie generale de mise en uvre du procede rtm (resin transfer molding ou injection a basse pression sur preforme fibreuse en moule clos) est proposee. Elle concerne les phases d'elaboration des pieces composites structurales. La premiere etape du projet permet de dresser un bilan des aspects industriels du procede : modelisations d'ecoulement de resine en milieu poreux, etude des moules et des materiels de mise en uvre (matrices et renforts). La conception des pieces d'application fait appel a des solutions innovantes. La validation de la demarche s'appuie sur la realisation de prototypes partiels permettant de valider des choix de solutions tant du point de vue du comportement mecanique que de la faisabilite technologique. L'application est une vanne de pressurisation d'avion. Les proprietes mecaniques des materiaux realises avec des tissus injectex et de la resine epoxyde ou phenolique par le procede rtm etant inconnues, des essais de caracterisation mecanique sont menes. Ensuite, les permeabilites principales du renfort sont mesurees. Cette etape est le prealable a la simulation numerique des ecoulements basee sur la loi de darcy. La conception des pieces, donc des preformes, dimensionnees en fonction du cahier des charges est developpee. La forme definitive des moules est determinee grace aux simulations d'ecoulements de resine (points d'injection et d'events). En dernier lieu, des tests mecaniques sur pieces reelles permettent de valider la demarche de conception. Cette etude a ete realisee en collaboration avec liebherr aerospace toulouse et moulages plastiques du midi.
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Laghi, Giulia. "Deposizione plasma assistita di coating barriera a base silicio su packaging polimerici: studio sperimentale e simulativo degli effetti dei parametri di processo." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2018.
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Negli ultimi decenni, l’industria alimentare ha sviluppato soluzioni per il packaging prevalentemente costituite da materiali plastici, come PET e PP. Questi polimeri non offrono sufficienti proprietà barriera alla permeazione di gas e di conseguenza non garantiscono un’adeguata shelf-life dei prodotti confezionati. Per questa ragione è forte l’interesse dell’industria alimentare nel trovare soluzioni barriera nuove ed efficienti. Tra queste, i coating barriera di silice si rivelano promettenti perché sono trasparenti e compatibili con il riscaldamento al microonde ed il riciclo del polimero su cui sono stati depositati. Una tecnica particolarmente interessante per la produzione di questi film è la deposizione plasma assistita a pressione atmosferica, che si caratterizza per basse temperature di trattamento, tempi di processo contenuti e ridotti costi d’impianto. Ottenere coating a pressione atmosferica con caratteristiche barriera adeguate è una sfida complessa ma la tecnologia offre numerosi gradi di libertà (configurazioni plasma, precursori gassosi e altri parametri di processo) che motivano fortemente la ricerca in questo ambito. L’obiettivo principale di questo lavoro di tesi è stata la ricerca delle condizioni ottimali per la deposizione plasma assistita a pressione atmosferica su substrati di polipropilene di coating di silice per applicazioni barriera. Mediante l’utilizzo di una configurazione Corona-jet sono stati depositati coating a partire da HMDSO al variare di alcuni parametri di processo, in particolare è stato osservato l’effetto della portata di ossigeno, del duty cycle e del tempo di trattamento sui depositi mediante analisi ATR-FTIR e SEM. In parallelo, è stata effettuata la progettazione di una configurazione DBD, assistita da una fase di modelling, al fine di indagare l’uniformità del profilo di velocità del flusso di gas all’interno della sorgente, aspetto indispensabile per garantire l’uniformità del deposito.
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Motta, Valentina. "Messa a punto di processi assistiti da plasmi freddi a pressione atmosferica per la sintesi in volo di nanoparticelle e la codeposizione di film polimerici nanostrutturati per applicazioni biomedicali." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2017.
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Il lavoro presentato riguarda la progettazione e messa a punto di un set up sperimentale assitito da plasmi atmosferici di non equilibrio per la sintesi in volo di nanoparticelle (NPs) di argento (Ag) e la simultanea codeposizione di coating polimerici nanostrutturati su substrati utilizzati per applicazioni biomedicali. Dapprima, le attività sperimentali hanno investigato la possibilità di sintetizzare in liquido NPs di Ag, sottoponendo una soluzione acquosa contenente il sale precursore al trattamento plasma effettuato mediante sorgente Corona Jet. Le analisi UV-VIS dei colloidi ottenuti hanno confermato la presenza di NPs di Ag nella soluzione, dimostrando la capacità del plasma di ridurre l’Ag del sale precursore portando alla formazione di NPs. Verificata la possibilità di sintetizzare NPs in liquido, la seconda fase di questo studio ha riguardato la messa a punto di un set up in grado di sostenere la sintesi in volo di NPs di Ag, introducendo nella regione di plasma la soluzione nebulizzata contenente il sale precursore. Le analisi condotte al microscopio elettronico a scansione (SEM) dotato di un sistema spettroscopia Energy Dispersive X-ray Spectrometry (EDS) hanno evidenziato la sintesi di NPs di Ag con dimensioni comprese tra qualche nanometro e il micron. Dimostrata la fattibilità della sintesi in volo, si è proceduto alla fase di codeposizione plasma assistita di coating polimerici nanostrutturati. La produzione di tali rivestimenti è avvenuta mediante contestuale introduzione nella regione di plasma del precursore monomerico, per la realizzazione della matrice polimerica, e del precursore salino in soluzione acquosa, per la sintesi in volo di NPs di Ag. La composizione chimica dei coating codepositati è stata analizzata mediante spettroscopia ad infrarossi in trasformata di Fourier e la morfologia è stata investigata mediante SEM-EDS.