Made available in DSpace on 2014-12-17T14:57:54Z (GMT). No. of bitstreams: 1 JanainaSS.pdf: 6774864 bytes, checksum: 445b5e932b89fcc09c4b97403b959e26 (MD5) Previous issue date: 2009-10-02 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior / Low cost seals are made of NBR, Nitrile Butadiene Rubber, a family of unsaturated copolymers that is higher resistant to oils the more content of nitrile have in its composition, although lower its flexibility. In Petroleum Engineering, NBR seal wear can cause fluid leakage and environmental damages, promoting an increasing demand for academic knowledge about polymeric materials candidate to seals submitted to sliding contacts to metal surfaces. This investigation aimed to evaluate tribological responses of a commercial NBR, hardness 73 ? 5 Sh A, polytetrafluoroethylene (PTFE), hardness 60 ? 4 HRE and PTFE with graphite, 68 ? 6 HRE. The testings were performed on a sliding tribometer conceived to explore the tribological performance of stationary polymer plane coupons submitted to rotational cylinder contact surface of steel AISI 52100, 20 ? 1 HRC Hardness, under dry and lubricated (oil SAE 15W40) conditions. After screening testings, the normal load, relative velocity and sliding distance were 3.15 N, 0.8 m/s and 3.2 km, respectively. The temperatures were collected over distances of 3.0?0.5 mm and 750?50 mm far from the contact to evaluate the heating in this referential zone due to contact sliding friction by two thermocouples K type. The polymers were characterized through Thermogravimetric Analysis (TGA), Differential Scanning Calorimetry (DSC) and Dynamic Mechanical Analysis (DMA). The wear mechanisms of the polymer surfaces were analyzed by Scanning Electron Microscopy (SEM) and EDS (Energy-Dispersive X-ray Spectroscopy). NBR referred to the higher values of heating, suggesting higher sliding friction. PTFE and PTFE with graphite showed lower heating, attributed to the delamination mechanism / Retentores de baixo custo s?o comercialmente dispon?veis de NBR, copol?meros insaturados de borrachas de nitrilo-butadieno que s?o mais resistentes aos ?leos quanto mais altos forem seus teores de nitrila, ? custa de uma menor flexibilidade. Em Engenharia de Petr?leo, o desgaste dos retentores de NBR causa vazamento de fluidos e danos ambientais, provocando uma crescente demanda de conhecimento acad?mico sobre materiais polim?ricos candidatos a retentor submetidos a contatos de deslizamento com superf?cies de metal. Este trabalho objetivou avaliar respostas tribol?gicas de tr?s pol?meros comercialmente dispon?veis, NBR, dureza 73 ? 5 Sh A, polytetrafluoroethylene (PTFE), dureza 60 ? 4 HRE e PTFE com grafite, 68 ? 6 HRE. Os ensaios foram realizados em um trib?metro de deslizamento concebido para explorar o desempenho tribol?gico de corpos-de-prova polim?ricos estacion?rios de superf?cie plana submetidos a um contato seco ou lubrificado (?leo SAE 15W40) de uma superf?cie rotativa cil?ndrica de a?o 52100, dureza 20 ? 1 HRC. A carga normal, a velocidade relativa e a dist?ncia de deslizamento foram, respectivamente, 3,15 N, 0,8 m/s e 3,2 km, determinadas ap?s ensaios explorat?rios iniciais. As temperaturas foram medidas por dois termopares tipo K a 3,0?0,5 mm e 750?50 mm de dist?ncia do contato para avaliar-se o aquecimento em uma mesma regi?o devido ao atrito de deslizamento no contato. Os pol?meros foram caracterizados atrav?s de An?lises Termogravim?tricas (TGA), Calorimetria Diferencial Explorat?ria (DSC) e An?lises Din?mico-Mec?nica (DMA). Os mecanismos de desgaste das superf?cies dos pol?meros foram analisados por Microscopia Eletr?nica de Varredura (MEV) e EDS (Espectroscopia por Energia Dispersiva de Raios-X). NBR apresentou os maiores valores de aquecimento, sugerindo maior atrito de deslizamento. PTFE e PTFE grafitado apresentaram um menor aquecimento, atribu?do ao mecanismo de desgaste por delamina??o

La conception des turbomachines à haute densité énergétique nécessite de plus en plus la maîtrise d'un plus grand nombre de paramètres fonctionnels. La moindre défaillance d'un composant conduit quasi immédiatement la machine à la rupture. C'est en particulier le cas pour le comportement des composants à films minces.L'appellation "film mince" correspond à tout espace de très faible épaisseur situé entre le rotor et le stator de la turbomachine. Leur but est soit de limiter les fuites de manière à optimiser les performances intrinsèques de la machine, soit alors à supporter et stabiliser le rotor. Ces derniers cas sont plus appelés communément "joints lisses ou annulaires" et "paliers fluides".Lorsqu'un fluide circule dans un espace de très faible épaisseur, typiquement quelques centièmes de millimètres sur une distance très longue, son champ de vitesses, donc de pression, dépend fortement des phénomènes visqueux aux parois dont l'une est mise en rotation et l'autre est immobile. Les efforts fluides sur ces parois peuvent être alors importants et doivent être pris en compte dans le dimensionnement de la machine.La connaissance précise de ces écoulements très complexes est indispensable pour déterminer les efforts statiques et dynamiques appliqués au rotor de manière à pouvoir dimensionner un fonctionnement calme. / The design of high performance aerospace turbo pumps requires more control of an increasing number of functional parameters. Any component failure led almost immediately to a machine failure. This is particularly the case for the behavior of thin film lubricated components.The term "thin film" means any thin space between the rotor and the stator of the engine. Their goal is either to limit leakage to maximize the machine intrinsic performance, or to support and stabilize the rotor. These cases are more commonly called "smooth or annular seals" and "fluid film bearings".When a fluid flows in a space of very small thickness, typically a few hundredths of a millimeter, the velocity field, hence the pressure, are highly dependent on the walls viscous forces. Fluid forces on the walls (which one is rotated and the other is stationary) can then be important and should be taken into account in the design of the machine.The precise knowledge of these complex flows is essential to determine the static and dynamic forces applied to the rotor to ensure a quite functioning of the turbo pump.

The late Neolithic of North Mesopotamia has long been held up as the first example of a ‘global’ culture with aspects of shared material culture, most notably pottery styles and subsistence strategies, spread across North Mesopotamia, the Northern Levant, and parts of south-east Anatolia. Increasing research in the past twenty years has illustrated that the material similarities visible in the late Neolithic do not represent a closed cultural community, but instead reflect a network of loosely connected groups who were members of imagined communities that linked people within shared cosmologies. Since their discovery in the early decades of the twentieth century stamp seals have been treated as a type artefact of the late Neolithic (particularly one of its constituent parts the Halaf) where they have been used to argue for the presence of sealing systems based around administrative storage of personal or communal property and possibly trade relations. However, except for a thesis published in 1990, late Neolithic stamp seals have never been comprehensively studied or interpreted primarily within their own context. Instead previous studies of stamp seals have tied stamp seals into a modernist narrative of progression that implicitly culminates in modern, Western, Nation States. This research challenges and deconstructs this narrative to demonstrate there is little evidence that seals in the late Neolithic were used for administrative purposes. To this end it gathered and re-classified the available data on provenanced stamp seals using a classificatory ontology called prototype theory that allows for more reflexive classification then the existing Aristotelian classifications. The thesis argues that stamp seals were indexical symbols with their symbolism being used to link members of imagined communities within real communities across the late Neolithic ‘world’. These people were members of a perceived descent group originating in shifting relationships to place during the change from sedentary farming communities in the eighth millennium BC to more mobile communities in the seventh millennium BC. At the same time as negotiating these supra-community identities seals were also used indexically in a variety of sub-community ways being used for a variety of magical (primarily apotropaic and talismanic) uses. As part of this I argue sealing practices in the late Neolithic relate to specific events of efficacious sealing using the power in the seal’s design.

This study reports and evaluates child outcome measures at a non-profit autism treatment program providing applied behavior analysis (ABA) based services to children age 3 to 8. To accomplish this, a review was conducted of available outcome data for a 1 year period. Several categories of outcome measures have been reported in the autism treatment literature (post-intervention educational placement, cognitive status, developmental and achievement status and/or progress, autism symptom reduction, and diagnostic reclassification). This study found that the program relied on 2 sources of data to evaluate child outcome: Hawaii Early Learning Profile® and program goal mastery. Children are making progress as indicated by these measures. The findings are discussed in relation to broader outcome recommendations.

This diploma thesis aims to thermodynamic calculation, carbon ring seal calculation and integrated gearbox calculation of single stage mechanicl drive steam turbine. The theoretical part of this work presents general classification of steam turbines, mechanicl drive steam turbine, types of blading and design of turbine seals. In the second part, we further discuss difference between carbon and labyrinth packing.

The recovering harbor seal population along the Swedish west coast has coincided with declining cod stocks. Although the cod stocks were primarily depleted by intense fisheries, some stakeholders argue that reduced seal populations could have direct, positive effects on the cod stocks. The outbreaks of Phocine distemper virus (PDV) in 1988 and 2002 when up to 66% of the harbor seals along the Swedish west coast died, could be viewed as natural experiments allowing for assessment of any positive impacts of reduced mortality from seal predation on cod abundance. I quantified removal from seal predation and fishery landings and analyzed correlations to cod abundance of different length classes. Analyses were conducted for a longer time- series, 1979-2019, reaching back to when removal from fisheries was substantially larger than that from seal consumption. I also analyzed the data with a more recent perspective, 2003-2019, starting after the later PDV outbreak when seal predation relative landing sizes has increased. During this period, fishery discard data is available and included in the models. Methods include graphical presentation, multiple linear regression analyses, and to expand the existing data on seal diet, I collected diet samples of harbor seal feces from two haul-outs in Skagerrak. No statistically significant, negative correlations between seal predation and cod abundance were found in any data set, hence, I cannot support the idea of harbor seals having an impact on cod abundance. Also, the significant correlations between cod abundance and landings were all positive. I argue that culling of seals cannot be motivated as a strategy to help cod recover, as this would jeopardize the persistence of the seal population rather than assuring cod stability.

Hyperelasticity is a significant property of rubber, taken advantage of in engineering applications. A common application is the use of seals to prevent fluid transfer (liquid or gas) between solid regions. Volvo CE is often depending on external supplier when developing seals. However, it could be beneficial to be able to do design and analysis in-house. Thus, they want with this master thesis to increase their knowledge about rubber and FEM simulations of seals in ANSYS. The aim with this work is to develop a method and guidelines for analysis and simulation of seals of hyperelastic materials. Components analyzed in this thesis work are two static seals, an O-ring andan in-house modified X-ring design. Selected materials, HNBR and FKM, are commonly used elastomers at Volvo CE. Material tests performed at RISE are for three different load cases:uniaxial tension test, planar tension test and biaxial tension test. Quasi-static analyses are performed in ANSYS. Hyperelastic materials need different constitutive models, hyperelastic material models, to describe their material behavior and these are defined in terms of a strain energy density function.However, the challenge is to determine the material constants in the equation, to characterize the material properties, by processing test data. Research questions answered are ‘’What material tests are needed for hyperelastic materials?’’, ‘’How is the test data converted to work as input to ANSYS and obtain material constants?’’ and ‘’How is an appropriate material model selected for simulation in ANSYS?’’. The study shows the importance of that material test represents the condition the application will experience. It should capture material behavior at the specific frequency, strain amplitude and temperature range for the application. The expected strain range and deformation modes that will play a functional role in the application should be considered in the material testing. Material constants can be determined from test data separately or simultaneously. Test data from at least one deformation mode is required, but one can't accurately predict full deviatoric behavior of hyperelastic material models by using one mode. If data only is used for one deformation mode, simulations in other deformation modes can yield erroneous results. It is therefore recommended to use several deformation modes. For applications with more complex load cases more deformation modes are needed. Generally, recommended tests are uniaxial tension test, planar tension test and biaxial tension test due to homogenous deformation is achieved. It is important to verify the material model before analysis. Using test data from one deformation mode can still provide a good fit. In the cases investigated verifications of the material model Yeoh 3rd order show that the fit obtained by only using uniaxial tension test data and using test data from three tests doesn’t seem to differ. Both uniaxial tension test data and test data from three tests give agood fit when simulating the tests with this material model. The benefit of using test data from three tests is questionable due to costs. It seems that only uniaxial tension test data could have been used as it provided a good fit. Moreover, test data must be processed to work as input to ANSYS. ANSYS requires engineering stress-strain test data for hyperelastic materials besides from the volumetric test, where true stress strain is required. The biaxial tension state which is realized with so called Bulge test thus needs to be converted to engineering stress. Then, test data needs to be adjusted to account for effects such as hysteresis and Mullin’s effect, where choice of curve and a process zero-shift must be done. Hyperelastic material models have different validity for different strain ranges. The selected material model was Yeoh 3rd order, which showed be a good fit for both the materials, HNBR and FKM, in strain range 30 %. The curve fit is based on three tests. The selection was based on the material model with lowest relative error with stability. Material constants were obtained for that material model, and these were used in simulations. Material models tends to be unstable for strains outside the test data. Simulations of seals with fluid pressure were performed for different pressure and stretch of the seal. If the contact pressure is larger than fluid pressure in the seals no leakage will occur. / Hyperelasticitet är en betydande egenskap hos gummi, som används i tekniska tillämpningar. En vanlig tillämpning är tätningar för att förhindra vätskeöverföring (vätska eller gas) mellan fasta områden. Volvo CE är ofta beroende av externa leverantörer vid utveckling av tätningar. De vill därför med detta examensarbete öka sina kunskaper om gummi och FEM-simuleringar av tätningar i ANSYS. Målet med arbetet är att utveckla en metod och riktlinjer för analys och simulering av tätningar av hyperelastiska material. Komponenter som analyseras i detta examensarbete är två statiska tätningar, en O-ring och en intern modifierad X-ringdesign. Utvalda material, HNBR och FKM, är vanliga elastomerer hos Volvo CE. Materialtester som genomförts på RISE är för tre olika belastningsfall: enaxligt dragprov, plant dragprov och biaxialt dragprov. Quasi-statiska analyser genomfördes i ANSYS. Hyperelastiskt material behöver olika konstitutiva modeller, hyperelastsiska materialmodeller, för att beskriva dess materialbeteende och dessa definieras i termer av töjningsenergidensitetsfunktion. Utmaningen är att bestämma materialkonstanterna i ekvationen, för att karakterisera materialegenskaper, genom att processa testdatat. Forskningsfrågor som besvaras är ’’Vilka materialtester är nödvändiga för hyperelastiska material?’’, ’’Hur konverteras testdata för att fungera som indata till ANSYS och erhålla materialkonstanter?’’ och ’’Hur väljs lämplig materialmodell för simulering i ANSYS?’’. Studien visar vikten av att materialtester representerar förhållanden som är representativa för applikationen. Det bör fånga materialbeteendet vid den specifika frekvensen, töjningsamplitud och temperatur för applikationen. Det förväntade töjningsomårdet och deformationslägen som kommer spela en funktionell roll i applikationen bör beaktas i materialtestningen. Materialkonstanter kan beräknas från testdata separat eller simultant. Testdata från minst ett deformationsläge krävs, men man kan inte exakt förutsäga fullständigt devatoriskt beteende hos hyperelastiska materialmodeller genom att använda ett deformationsläge. Om testdata endast används för ett deformationsläge kan simuleringar i andra deformationslägen ge felaktiga resultat. Det är därför rekommenderat att använda flera deformationslägen. Generellt rekommenderade tester är enaxligt dragprov, plant dragprov och biaxialt dragprov då homogen deformation uppnås. Det är viktigt at verifiera materialmodellen innan analys. Att använda testdata från ett deformationsläge kan fortfarande ge en bra passning. I de undersökta fallen visar verifikation av materialmodellen Yeoh 3:e ordningen att passningen som erhållits av enbart enaxligt dragprovtestdata och testdata från tre tester inte skiljer sig åt. Både enaxligt dragprov testdata och testdata från tre tester ger en bra passning när simulerar testerna med den materialmodellen. Fördelarna med att använda testdata från tre tester är ifrågasatt pga. kostnaderna. Det verkar som enbart enaxligt dragprov testdata kunde ha använts då det gav en bra passning. Vidare behövs testdata hanteras för att fungera som indata till ANSYS. ANSYS behöver nominellspänning-töjning testdata för hyperelastiska material förutom för det volymetriska testet, där sannspänning-töjning behövs. Det biaxiala dragprovet som realiserades med s.k. Bulge test måste därför konverteras till nominell spänning. Sedan behöver testdata justeras för att ta hänsyn till effekter som hysteres och Mullins effekt, där val av kurva samt en process ‘’zero-shift’’ måste göras. Hyperelastiska materialmodeller har olika giltighet för olika töjningsområden. Val av materialmodell blev Yeoh 3:e ordningen som visade sig vara en bra passning för båda materialen, HNBR och FKM, i töjningsområden 30%. Kurvanpassningen är baserad på tre tester. Valet baserades på den materialmodell som hade minst relativt fel och som var stabil. Materialkonstanterer hölls för den materialmodellen och dessa användes i simuleringar. Materialmodeller tenderar att vara ostabila för töjningar utanför testdata. Simuleringar av tätningar med flödestryck genomfördes för olika tryck och stretch av tätningen. Om kontakttrycket är större än flödestrycket i tätningen sker inget läckage.

[pt] A correta operação de equipamentos na indústria de Óleo e Gás é fundamental para a reduzir perdas ambientais, humanas e financeiras. Neste cenário, foram estudados selos secos a gás (em inglês,DGS) de compressores cetrífugos, por serem identificados como os mais críticos devido à extensão dos danos potenciais causados em caso de falha. Neste estudo, foram desenvolvidos 31 modelos regressivos disponíveis no Scikit-Learn através de técnicas de aprendizado de máquina (em inglês, ML). Estes foram treinados com um conjunto de dados escassos, criado a partir de uma técnica de planejamento de experimentos, para substituir simulações numéricas na previsão de confiabilidade operacional de DGSs. Primeiramente, foi validado um modelo baseado na simulação da Dinâmica dos Fluidos Computacionais (em inglês, CFD) para representar o escoamento do gás entre as faces de selagem, a fim de possibilitar o cálculo da confiabilidade operacional do equipamento. Neste, foi utilizado o software de CFD de código aberto OpenFOAM em conjunto com o banco de dados de substâncias do software REFPROP, a fim de possibilitar ao usuário definir a mistura gasosa e as condições operacionais avaliadas. Em seguida, foram realizados dois estudos de caso seguindo um fluxograma genérico de projeto proposto. O primeiro consistiu na determinação de um modelo regressivo para estimar a confiabilidade de um DGS cuja composição gasosa (composta por metano, etano e octano) é fixa porém suas condições operacionais podem ser alteradas. Já o segundo consistiu na determinação de um modelo regressivo mais robusto, onde tanto a composição gasosa como as condições operacionais podem ser alteradas. Por fim, foi avaliada a viabilidade de implementação de ambos os modelos em condições reais de operação, baseado na norma infinita obtida para a predição do conjunto de teste. As performances atingidar foram de 1.872 graus Celsius e 6.951 grau Celsius para o primeiro e segundo estudos de caso, respectivamente. / [en] The correct equipment operation in the Oil and Gas industry is essential to reduce environmental, human, and financial losses. In this scenario, dry gas seals (DGS) of centrifugal compressors were studied, as they are identified as the most critical device due to the extent of the potential damage caused by their failure. In this study, 31 regression models available at Scikit-Learn were developed using machine learning (ML) techniques. They were trained with a scarce dataset, created based on a design of experiment technique, to replace numerical simulations in predicting the operational reliability of DGSs. First, a model based on Computational Fluid Dynamics (CFD) simulation was validated to represent the gas flowing between the sealing faces, to enable the calculation of the equipment’s operational reliability. Thus, the open-source CFD software OpenFOAM was used together with the substance database of the software REFPROP, to allow the user to define the gas mixture and the evaluated operational conditions. Then, two case studies were carried out following a proposed generic workflow. The first comprised determining a regression model to estimate the reliability of a DGS whose mixture composition (composed of methane, ethane, and octane) is fixed but its operating conditions can vary. The second consisted of determining a more robust regressive model, where both the mixture composition and the operational conditions can vary. Finally, the feasibility of implementing both models under realistic operating conditions was evaluated, based on the infinity norm obtained for the prediction of the test set. The performances achieved were 1.872 degrees Celsius and 6.951 degrees Celsius for the first and second case studies, respectively.

No description available.

Sound transmission loss of vehicle seals was studied in this thesis. Reverberation room test and semi-anechoic chamber test were respectively studied. By comparing the sound pressure level, sound intensity level and average sound power level at the receiving side, it proved that a simple sound pressure level test may obtain same measurement accuracy when there is little reflected sound. A semi-anechoic chamber was designed for testing sound transmission losses of the seals on a trial vehicle. By comparing the sound pressure levels between the location of the passenger ear and door area, it proved that most of outside sound energy passed through the door seals into the interior. The sound transmission losses of different sealing conditions were measured which included well sealed and imperfectly sealed conditions; Sound pressure levels at passenger’s ear in three different types of vehicles were also compared, these comparison results indicated this laboratory was capable of distinguishing different sealing conditions. The installation procedure was compared with the one in reverberation room test. Numerical analysis showed that the latter method produced a different compression shape which would definitely influence the sound insulation abilities of the seals.   The transmission mechanism of the acoustic waves through a vehicle seal was also discussed. Contact analysis showed high compression ratio leaded to tremendous inner stress intensity. But any further increase of the contact depth would not improve the effect of wind noise prevention. A vehicle seal with a complex shape was replaced by a simple model. The sound transmission theory of multiple partitions on the basis of mass law was applied. Whereas, compared with the experimental result, a different trend in the high frequency range was found. When taking the transmission though the side material and integration of incident angle into account, the result was quite similar to the experimental one. FEM analysis was also performed. The majority of sound power was believed to transmit along the seal wall into the interior instead of passing through the multiple partitions. A distorted circular duct model is believed to be close to the real geometry. / QC 20101117