Abrasive Flow Machining, (AFM), is a non-traditional machining process that is achieved by extruding polyborosiloxane, (a viscoelastic polymer), containing abrasive grit additions, across surfaces, edges, and through component cavities. The AFM process is a complex one and its machining mechanism is still only partially understood since previous research into the process has mainly been limited to qualitative study. The present work undertook to investigate the relationship between the rheological characteristics of polyborosiloxane/grit mixtures and the associated machining parameters. A significant increase in the quantitative data available with respect to both the rheological and machining characteristics of these mixtures has been provided as a consequence of the investigations. Experiments were conducted using low viscosity, (LV), medium viscosity, (MV), and high viscosity, (HV), polyborosiloxane base media, in conjunction with silicon carbide abrasive grit of 60 and 100 Mesh size; the ratios of grit to base polymer utilised in the experiments were 0,1, and 2. The test pieces used in the experimental work were mild steel dies having a diameter of 15mm and a length of 1 5mm, and the equipment used to conduct the experiments was an Extrude Hone mark 7A machine. The investigations conducted have revealed that for all polymer/grit mixtures an increase in the number of extrusion cycles results in an increase in the stock removed, an improvement in the surface roughness, and an increase in the temperature of the mixture. Furthermore as the usage of the medium increases the grit particle wear increases so that there is a corresponding decrease in the machining parameters. For all mixtures there appears to be no correlation between the viscosities of the base media types and the machining parameters. However, a relationship is demonstrated between the machining parameters and variations in the viscosities of the grit/polymer mixtures based on a specific polymer base. The factors that appear to influence this relationship are the grit to polymer ratio, the grit size, and the temperature. The most important of these parameters are suggested to be the grit to polymer ratio and temperature since these variables appear to affect the viscosity behaviour and the associated machining parameters. In addition the investigations showed that the viscosities and associated rheological dependent parameters correspond to the qualitative viscosity nomenclature given to the different media types by the manufacturer. A shear history effect is also exhibited in each of the polymer types.

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Within the oil and gas industry on offshore installations in the North Sea, several oil wells are closing in on the brink where they no longer are being profitable to keep producing from. When that day comes the oil wells are closed off and the boreholes are plugged with cement. Before the holes can be cemented shut the companies need to remove all their equipment that has been used for underwater exploitations of the well and if applicable remove the above water installation as well. This includes removing the casing that the holes are lined with which main purpose is to prevent the hole from collapsing on the production line and to prevent oil and gas leaks into the surroundings. This thesis focuses on removal of the borehole casing.  When performing this task problems have been raised regarding corrosion on the casing couplings, making them very hard to separate. When this problem occurs, the need for an alternative method to split them is necessary. As of today this operation is performed by cold cut sawing or with a beveling machine. This is a highly time consuming task and an alternative method to perform a faster cut is wanted. This degree work investigates the possibilities of doing this using the benefits of abrasive water jet (AWJ) cutting. The major concerns on using this technic is whether it is fast enough and if it is possible to perform in accordance with the fire and explosive hazards on a hydrocarbon producing installation. As a reference the maximum cut time is set to one minute. Calculations on theoretical cutting speeds as well as physical testing on the AWJ method has been performed and evaluated. The investigations show that the method does have the possibilities of making the cut within the target time.  The work also contains a simple concept model on how the equipment could be constructed. / Inom olje- och gasindustrin på offshoreanläggningar i Nordsjön, närmar sig flera reservoarer randen där de inte längre är lönsamma att fortsätta producera från. När den dagen kommer pensioneras borrhålen och pluggas med en cementblandning. Innan hålen pluggas måste företagen ta bort all utrustning som har använts vid utvinningen av brunnen, både ovan och under ytan. Detta innefattar avlägsnande av casingen, som hålen är fodrade med, och vars huvudsakliga syfte är att förhindra att hålet kollapsar och skadar produktionsledningen, men även för att förhindra olje- och gasläckor till omgivningen. Denna avhandling fokuserar på borttagandet av casingen. När detta görs upplevs problem med att casingskarvarna är kraftigt korroderade vilket gör dem mycket svåra att separera. Detta är ett problem som efterfrågar en alternativ delningsmetod. I dag utförs den här operationen med antingen kallsågning eller med en avfasningsmaskin. Detta är en mycket tidskrävande uppgift och en metod för att utföra en snabbare delning önskas. Detta examensarbete är tänkt att undersöka möjligheterna att göra detta genom att använda fördelarna med abrasiv vattenskärning för att kapa rören. De största frågorna gällande denna metod är om den är tillräckligt snabb och om det är möjligt att utföra i enlighet med de brand- och explosionsrisker som finns på en kolväteproducerande installation. Som referens är målet för maximal skärtid satt till en minut. Beräkningar på teoretiska skärhastigheter samt fysiska tester på metoden har utförts och utvärderats. Undersökningarna visar på att metoden har möjligheter att göra snittet inom utsatt tid. Arbetet innehåller också en enkel konceptmodell på hur utrustningen skulle kunna konstrueras.

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This work is a preliminary attempt to study the effect between thermal shock and abrasive wear in WC-Co alloys. This was done by evaluating the thermal shock resistance of a WC-12wt%Co mining grade as a function of temperature, number of thermal shock cycles and making comparisons between the abrasive wear responses of samples subjected to thermal shock and samples not subjected to thermal shock. A furnace was designed for the thermal shock treatments. Abrasive wear tests were performed on a 2-body sliding wear apparatus using 80-grit SiC abrasive paper as a counter-face. Stereo and electron microscopy as well as microprobe techniques were used to analyse the effects of thermal shock. It is confirmed that thermal shock has a negative effect on the wear rate of WC-12wt%Co. The results showed an initial high mass loss rate during abrasive wear testing, which increased with increasing temperature and a decrease in wear rate with time until the wear rates converged for all samples. The surface analysis after thermal shock indicated voids on and below the surface, stained surfaces, a thin oxide layer and the possibility of WC decarburization which accelerated the wear response.

Resumo: O corte de aços por disco abrasivo é um dos processos que apresentam as melhores características de economia, eficiência e rapidez, e ainda hoje é muito utilizado no meio industrial se comparado a outros processos tradicionais de corte como o cisalhamento (tesourão), torneamento (sangramento), serragem com serras metálicas, serragem por atrito com lâminas circulares sem dentes e chama oxi-acetileno. Da literatura formal mais recente, nota-se que durante os últimos anos as máquinas para a realização dos cortes foram inovadas. Entretanto, esta atenção não foi dada à ferramenta de corte abrasiva. A falta de literatura técnica dificulta a escolha das condições de corte e da sua otimização no meio industrial. Este fato é agravado pela grande diversidade de discos abrasivos disponíveis no mercado, com diferentes qualidades e preço. As decisões sobre as condições de corte são baseadas em experiências pessoais, sem critério definido, e freqüentemente desprezam os aspectos de segurança inerentes ao processo. A concorrência estrangeira, através da globalização da economia, está obrigando as indústrias nacionais a atenderem os padrões internacionais de qualidade e desempenho. Uma forma das indústrias nacionais tornarem-se mais competitivas é através do conhecimento detalhado das operações de corte com discos abrasivos. Neste trabalho é apresentado um estudo sobre o comportamento de discos abrasivos, submetidos a diversas condições de corte. Os resultados são discutidos em função da análise da velocidade de corte, velocidade de mergulho do disco abrasivo na peça, força tangencial de corte média, tempo de corte e relação G. / Abstract: The cut-off operation shows the best savings, efficiency and quickness caracteristics and nowadays it is very used in the industrial environments if compared to other traditional cutting operations like shearing, turning, sawing with metalic hacksaws, friction sawing with non-tooth circular blades and oxi-acetylene torch cutting. In the most recent bibliography, it is noted that the new cutting machines have been improved. However, this fact did not happen in the abrasive cut-off tools. The lack of technical bibliography led the cutting conditions and optimizations choices to be a hard action. Such difficulties are worsen because there are many kinds of abrasive cutting wheels available with different qualities and prices. So, these choices are based on personal experiences, without parameters, and frequently despise the security aspects of the operations. The foreign competition, through the economy globalization, is forcing the national industry to attend the international quality and performance standards. One way for the national industries become more competitives (improving the productivity and decreasing the production costs) it is by the detailed knowledgment of the cut-off operations with abrasive wheels. This work shows a research about the abrasive wheels behavior, under several cutting conditions. The results are discussed in function of the cutting speed, downfeed of the abrasive wheel, average of tangencial cutting force, time per cut and G parameter analysis.

Abrasive finishing is a machining process which alters the surface of a workpiece to achieve a specific property. Typical abrasive finishing processes focus on geometric tolerances and surface topography. Abrasive finishing is primarily dependent on finishing forces, relative velocities, and abrasive size. The material removal rate in finishing is inversely related to the surface finish. Magnetic and electric fields have been used to control the force applied to abrasives which finish the workpiece. These processes show an increase in performance when the field is used to control the process. Field assisted finishing processes can be energy intensive and expensive. A novel finishing media is proposed which does not require a field to achieve a similar force response. This media has inherent thickening mechanisms driven by shear jamming. This shear jamming mechanism can deliver forces an order of magnitude higher than shear thickening mechanisms. This novel slurry is demonstrated as a viable finishing media with performance similar to magnetic abrasive finishing. / Thesis / Master of Applied Science (MASc)

L’énergie hydraulique, où l’énergie cinétique de l’eau est transformée en énergie électrique, représente une contribution importante aux énergies renouvelables. L’eau qui passe par les turbines hydrauliques contient toujours une partie solide, par exemple du sable et de l’argile. Ces sédiments peuvent atteindre des niveaux de concentration élevés, ce qui nuit considérablement à la structure de la turbine par un mécanisme d’endommagement appelé érosion hydro-abrasive. Des types de turbine impliquant des vitesses d’écoulement très élevées, comme les turbines Pelton, sont particulièrement sensibles à l’érosion hydro-abrasive. Les simulations numériques présentent un moyen efficace d’étudier le sujet de l’érosion hydro-abrasive dans les turbines Pelton car elles permettent facilement la variation des nombreux paramètres. Ainsi, une réponse immédiate aux questions opérationnelles, de conception ou d’optimisation peut être obtenue. Cependant, il a été démontré que l’application des modèles d’érosion généraux et souvent utilisés ne fournit pas de résultats corrects en raison des propriétés particulières du matériel et de l’écoulement des turbines Pelton. Par conséquent, ce travail étudie le potentiel de la modélisation de l’érosion directe basée sur des principes fondamentaux. Cela implique que le mouvement des sédiments dans le fluide est simulé, leurs paramètres au moment de l’impact enregistrés et ensuite l’endommagement macroscopique global du matériel calculé sur la base des simulations de structure en microéchelle. Une formulation très appropriée pour les simulations fluides dans les turbines Pelton est une méthode sans maillage, plutôt nouvelle, qui s’appelle Smoothed Particle Hydrodynamics (SPH). Par conséquent, la première partie de ce travail aborde la mise en oeuvre et l’évaluation d’un modèle Lagrangien de transport des sédiments dans le cadre de cette méthode où les sédiments sont transportés par une équation de mouvement. L’effet du bruit inhérent à la méthode SPH sur le mouvement des sédiments est évalué par rapport à l’effet de la dispersion turbulente des sédiments, qui a été introduite par un modèle basé sur l’équation de Langevin. En outre, les termes liés aux différentes forces dans l’équation du mouvement sont étudiés dans le cadre de la méthode SPH. Une deuxième partie de ce travail développe une approche efficace et généralement applicable pour obtenir l’endommagement globale sans adopter des modèles d’érosion. Pour obtenir cet endommagement global en macroéchelle, l’endommagement causé par un seul impact de sédiment, qui est calculé par des simulations de structure en microéchelle, est combiné avec les statistiques d’impact des simulations du fluide. / Hydraulic energy represents one important contribution to the growing source of renewable energies where the kinetic energy of water is transformed into electric energy. The water flowing through the hydraulic turbines always contains a solid part, for example sand and clay. Those sediments can reach high concentrations, harming importantly the turbine structure by a mechanism called hydro-abrasive erosion. Turbine types implying very high flow velocities, like Pelton turbines, are in particular sensitive to hydro-abrasive erosion. Numerical simulations present an efficient way to study the topic of hydro-abrasive erosion in Pelton turbines as they allow the variation of numerous parameters. Thus an immediate response to operational, design or optimization questions can be obtained. However it has been shown that the application of general, widely used erosion models do not deliver physical correct results due to the particular material and flow properties of Pelton turbines. Consequently this work investigates the potential of erosion modeling based on first principals. That means the sediment movement in the fluid is simulated, their state at impact tracked and then the overall macroscopic material damage calculated based on microscale structural simulations. A convenient formulation for fluid simulations in Pelton turbines is the rather novel, meshless method Smoothed Particle Hydrodynamics (SPH). Therefore the first part of this work addresses the implementation and evaluation of a Lagrangian sediment transport model in the framework of this method where sediments are transported by a particle equation of motion. The effect of the SPH method inherent noise on the sediment movement is evaluated against the effect of the turbulent dispersion of the sediments, which has been introduced via an ad-hoc model based on the Langevin equation. Furthermore the different force terms in the particle equation of motion are investigated with respect to the SPH method. A second part develops an efficient and general applicable approach to obtain the overall erosion damage without adopting erosion models. Therefore the damage caused by a single sediment impact is calculated by structural simulations on the microscale in a first step. In a second step that isolated damage is combined with impact statistics from the fluid simulations and hence gives the overall damage profile on the macroscale.

A iminente escassez de recursos naturais e de fontes energéticas não renováveis são forças motrizes para a adoção de práticas sustentáveis. Dentre os processos industriais que fazem uso intensivo de recursos naturais, estão os que utilizam processos de usinagem baseados em ferramentas abrasivas para desbaste, esmerilhamento, corte, entre outros. A partir deste panorama geral, é possível enxergar a necessidade de estudar os processos de usinagem com ferramentas abrasivas a fim de aumentar a compreensão sobre eles e de torná-los sustentáveis. Sendo assim, o objetivo deste trabalho é avaliar, por meio do comportamento mecânico de compósitos abrasivos resinoides, o potencial de reciclagem de grãos de alumina oriundos de ferramentas abrasivas. No presente trabalho, foi estudada a preparação e caracterização de compósitos abrasivos resinoides reforçados com grãos alumina reciclada e virgem. Uma das aluminas recicladas é oriunda de rebolos e discos de corte resinoides, outra alumina é oriunda de rebolos vitrificados, e a última, composta por alumina branca, é recuperada de rebolos vitrificados refugados ou usados. As amostras de grãos de alumina reciclada e a de grãos de alumina marrom virgem foram caracterizadas por meio das técnicas de fluorescência de raios X (FRX), difratometria de raios X (DRX), microscopias óptica (MO) e eletrônica de varredura (MEV). Corpos de prova de compósitos utilizando os quatro tipos de alumina foram preparados por meio da mistura, prensagem e tratamento térmico de grãos de alumina e resinas fenólicas resol e novolaca. Por fim, os compósitos foram caracterizados por meio das técnicas de calorimetria exploratória diferencial (DSC), módulo elástico por excitação por impulso, impacto Izod, flexão em quatro pontos, análise térmica dinâmico-mecânica (DMTA), dureza por Sand Blasting Penetration (SBP), porosidade pelo método de Arquimedes e microscopias óptica e eletrônica de varredura. Os resultados dos ensaios mecânicos mostraram que os compósitos de alumina reciclada apresentaram depreciação em todas as propriedades estudadas em relação ao compósito de alumina virgem, exceto a resistência ao impacto Izod, no qual todas as amostras apresentaram baixa resistência. A razão desta baixa resistência ao impacto deveu-se à estrutura formada pelo grão de alumina, ligante (resina fenólica) e porosidade, na qual a baixa proporção de resina fenólica (10% m.) foi a responsável pelo resultado. Por outro lado, a causa da depreciação nas propriedades mecânicas apresentadas pelos compósitos de alumina reciclada foi a menor concentração em alumina e a presença de impurezas oriundas da produção das ferramentas abrasivas. Neste caso, o compósito de alumina branca reciclada apresentou melhores resultados das propriedades mecânicas em relação aos compósitos de alumina oriunda de rebolos vitrificados e os de alumina oriunda de rebolos e discos resinoides. Concluindo, o potencial de reciclagem dos grãos de alumina oriundos de ferramentas abrasivas visando o seu reaproveitamento no processo de fabricação destas ferramentas é limitado pela sua pureza, de modo que se no processo de reciclagem dos grãos for aumentada a concentração de alumina haverá possibilidade de seu reaproveitamento. / The imminent scarcity of natural resources and nonrenewable energy sources are driving forces for the adoption of sustainable practices. Among the industrial processes that make intensive use of natural resources, there are those that use machining processes based on abrasive tools for roughing, grinding, cutting, among others. From this general panorama, it is possible to see the need to study the machining processes with abrasive tools in order to increase the understanding about them. Thus, the objective of this work is to evaluate, through the mechanical behavior of resin-bound abrasive composites, the recycling potential of alumina grits from abrasive tools. In the present work, the preparation and characterization of resinoid abrasive composites reinforced with recycled and virgin alumina grits was studied. One of the recycled aluminas comes from resin-bound grinding wheels and thin wheel cut-off discs, another alumina comes from vitrified grinding wheels, and the latter, composed of white alumina, is recovered from scrapped or used glazed grinding wheels. The samples of recycled alumina grits and virgin brown alumina grits were characterized by X-ray fluorescence spectroscopy (XRF), X-ray diffractometry (XRD), optical microscopy (OM) and scanning electron microscopy (SEM). Composite test bodies using the four types of alumina were prepared by mixing, pressing and heat treatment of alumina grits and resol and novolak phenolic resins. Finally, the composites were characterized by differential scanning calorimetry (DSC), impulse excitation elastic modulus, Izod impact, four-point flexing, dynamic-mechanical thermal analysis (DMTA), Sand Blasting Penetration hardness (SBP), porosity by the Archimedes method and optical and scanning electron microscopy. The results of the mechanical tests showed that the recycled alumina composites presented depreciation in all the studied properties in relation to the virgin alumina composite, except the Izod impact resistance, in which all the samples presented low resistance. The reason for this low impact strength was due to the structure formed by the alumina grit, binder (phenolic resin) and porosity, in which the low proportion of phenolic resin (10% m) was responsible for the result. On the other hand, the reason for the depreciation in the mechanical properties presented by the recycled alumina composites was the lower concentration in alumina and the presence of impurities from the production of the abrasive tools. In this case, the recycled white alumina composite presented better mechanical properties in relation to alumina composites from vitrified grinding wheels and those from alumina from grinding wheels and resinoid disks. In conclusion, the recycling potential of the alumina grits from abrasive tools aiming at their reuse in the process of manufacturing these tools is limited by their purity, so that if in the grit recycling process the alumina concentration increases it will make possible its reuse.

No description available.