The occurrence of hot tearing during solidification is one of the major factors influencing both the quality and productivity of aluminum castings. In order to reduce the formation of hot tears, quantitative information regarding both hot tearing formation and semi-solid deformation is essential. In this study, the mechanisms of hot tearing and semi-solid deformation have been investigated via two novel techniques: x-ray micro-tomography on material deformed in the semi-solid region, and development of a three phase microstructural model based on a geometry derived from a Voronoi diagram with rounded corners and porosity. Numerical techniques were utilized to quantify both the size evolution and orientation of internal damage relative to void growth. In order to conduct the above research, a new semi-solid tensile deformation methodology was devised which uses a two thermocouple control technique to enable accurate measurement of semi-solid tensile strength and ductility. The experimental work was conducted on the aluminum – magnesium alloy AA5182 in the as-cast and hot isostatic pressing (HIP) states. The x-ray micro-tomography technique was used to observe that semi-solid deformation is accommodated by internal damage via growth of as-cast porosity and the nucleation of new damage-based voids. As the volume fraction of damage increases, the growth of voids occurs in an orientation perpendicular to the loading direction, both through expansion within the grain boundary liquid and via coalescence between voids. The damage then localizes, causing failure. The finite element semi-solid microstructural model was used to explore the effects of fraction solid, fraction porosity, and grain size on semi-solid constitutive behaviour. The simulations revealed that increased grain size and fraction porosity lead to a reduction in flow stress for a given fraction solid. Furthermore, local strain accumulation was linked to hot tearing, since strain localizes in the liquid very early in the deformation process. Based on the model predictions, a new constitutive relationship was developed over the range 0.75 < fs < 0.95. Together, these two techniques have provided powerful new insight, such as the critical role played by as-cast porosity, on the phenomena of hot tearing and semi-solid deformation in aluminum alloys. / Applied Science, Faculty of / Materials Engineering, Department of / Graduate

Orientador: Maria Helena Robert / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecanica / Made available in DSpace on 2018-07-23T20:58:55Z (GMT). No. of bitstreams: 1 Bubenik_RubensLuiz_M.pdf: 9820006 bytes, checksum: 74e4259834492d5dafe6eb6b382dbc4f (MD5) Previous issue date: 1998 / Resumo: Este trabalho trata do projeto e construção de um equipamento capaz de alterar a morfologia da fase primária de ligas metálicas em solidificação, diferenciando-a das estruturas dendríticas produzidas na solidificação convencional. Neste processo uma força externa provoca movimentos no metal líquido com objetivo de alterar a morfologia de crescimento do sólido, resultando em estruturas pré-reofundidas. No equipamento idealizado é utilizado um campo magnético girante para fornecer a força necessária ao movimento. O trabalho envolve projeto, construção e montagem de circuitos elétricos, circuitos eletrônicos e dispositivos mecânicos, bem como testes de eficiência do equipamento na produção de estruturas pré-reofundidas da liga AA 2011. Para testes foram variados o tempo de agitação do líquido (230 e 300 s), e o modo de agitação (normal e com reversão), sendo mantidas constantes a potência (1040 W) e a taxa de resmamento ('20 GRAUS¿/min.). Os resultados obtidos atestam a eficiência do equipamento na obtenção de lingotes com macroestrutura equiaxial refinada, homogênea em todo o seu volume, e microestrutura apresentando dendritas fragmentadas, com fator de forma de 2 a 3 para todas as condições analisadas. Estes valores de fator de forma podem ser considerados excelentes para materiais a serem utilizados como matéria prima para a conformação no estado pastoso reofundido / Abstract: This work relates the design and development of an equipment capable of modifying the morphology of primary phase during solidification of metal alloys, differentiating such structures ftom those dendritic obtained in conventional solidification. In this process turbulence is imposed to the liquid metal by means of a external force with the purpose of modifying the morphology of the growing solid, resulting in pre-rheocast structures. In the idealized equipment a rotating magnetic field is used to provide the necessary stirring in the Liquid. This work involves design, building and assembling of the equipment, as well as preliminarytests to analyse the efficiency of the equipment to produce ingots of the alloy AA 2011 with pre-rheocast structures. Different stirring times (230 and 330 s) and type of movement (normal or reverted) were utilized in the tests, while power and freezing rate in the material were kept constant (1040 W and '20 DEGREES¿/min., respectively). Results showed the efficiency of the designed equipment in the production of ingots with fine, equiaxial and homogeneous macrostructure and microstructures presenting highly ftagmented dendrites, with values of morphology index varying ftom 2 to 3 for all operational conditions tested. Those values of morphology index can be considered excellent for a material to be utilized as raw material for forming in the semi-solid state or thixoforming / Mestrado / Materiais e Processos de Fabricação / Mestre em Engenharia Mecânica

Charles University Faculty of Pharmacy in Hradec Kralove Department of Pharmaceutical Technology Author: Jakub Tisoň Title of thesis: Evaluation of rheological properties of nasal sprays Supervisor: PharmDr. Eva Šnejdrová, Ph.D. The aim of the submitted diploma thesis was to develop a comprehensive methodology for testing the rheological and especially thixotropic properties of nasal suspensions. Characterize the original preparation Avamys® and samples of a generic preparation at various stages of the formulation by selected tests. Within the theoretical part of the work, the nasal application of drugs, nasal preparations were discussed, the basics of rheometry were summarized and the principle of relevant rheological tests was described. Flow curves were measured on a Kinexus rotary rheometer using plate-to-plate geometry and analyzed by power law. The yield stress of nasal suspensions was determined. The thixotropic properties were evaluated by the area of the hysteresis loop, and especially by the three-step thixotropy test. The conformity of selected rheological characteristics of the tested samples with the original preparation was evaluated. Key words: nasal sprays, viscosity, yield stress, thixotropy.

The car industry is constantly under pressure to be competitive in their product development which includes not only safety and increased performance, but also in their environmental impact. Volvo Cars strives to be more environmental and high performing in their product development, which of course includes manufacturing methods since these highly effect a components environmental impact and mechanical performance. To optimize these aspects of car components it is important to have good knowledge of current manufacturing processes and the possibilities and challenges that come with them and their relationship to already well-established processes. This report focuses on the relatively new RheoMetal-process (called rheocasting in this report), a process that uses a partly solidified slurry to fill the mold, and the conventional high pressure die casting (HPDC) which uses a liquid melt, and their differences in casting aluminum-alloys from both a process-and design perspective. The RheoMetal-process is also compared to a few other semi-solid processes on the market, thixocasting, GISS and SEED. This report is meant to work as a foundation for product developers at Volvo Cars to learn about rheocasting, and eventually use to make future choices for manufacturing processes for aluminum alloys. With a literature review, interviews with experts and professionals and analysis of casting simulations, information of the processes and their effect on material properties was collected and compiled. What could be concluded from these methods was that the slurry in the RheoMetal process has a globular microstructure, unlike the melt in HPDC which is dendritic. The globular microstructure in rheocasting is caused from shearing the slurry which makes it run more easily. The thicker consistency of the slurry makes the flow more laminar when filling a mold which makes for less air entrapment and defects in the material. The reduced number of defects opens the possibility of using T6 heat treatment on rheocasted components to reach improved mechanical properties, which would normally not be recommended for components made with HPDC. The globular microstructure makes the slurry flow easier which means, in combination with less defects, thinner components can be cast with similar strength as thicker components made with HPDC. This would contribute to weight reduction in a car, and in turn less fuel consumption. With rheocasting, a wider range of alloys can be used because of the ability of using non-eutectic alloys for the slurry. From research and analysis of simulations it could also be concluded that a combination of a high solid phase fraction and low gate velocity result in a more laminar flow and therefore fewer porosities in the final component.

"This research investigated the relationship between T5 heat treatment and elongation in thixocast and rheocast SSM components as a means to reduce the energy, time, and cost associated with T6 treatments while still producing improved properties over the as-cast condition. Temperature and time were varied as a part of work to optimize aging conditions for SSM materials. Both conventional furnace and fluidized bed heat treatments were employed. Tensile bars were fabricated from the heat treated A356 components and were pulled. Extensive SEM and stereo microscopy were performed to examine the factors which produced favorable results in the T5 condition. Data generated for T6 and as-cast components were also collected for purposes of comparison. Quality index calculations were employed to help evaluate the results. Optimized procedures and aging parameters have been presented"

Orientador: Maria Helena Robert / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecanica / Made available in DSpace on 2018-11-08T18:39:47Z (GMT). No. of bitstreams: 1 Silva_RenatoRafaelda_M.pdf: 15646556 bytes, checksum: 19ff8cd2fd9081ac7985bc44c94795f5 (MD5) Previous issue date: 2008 / Resumo: Este trabalho teve como objetivo estudar o processo de produção de esponjas metalicas por tixoconformacao em pré-formas removiveis e caracterizacao mecanico-metalurgica do produto, visando a compreensão da influencia de parametros de processo nas suas caracteristicas estruturais e propriedades. A liga empregada, AA2011, foi infiltrada sobre pre-formas de particulas de NaCl de granulometrias distintas, sinterizadas ou soltas. As esponjas metalicas produzidas foram caracterizadas quanto a sua arquitetura, propriedades fisicas (densidade real e relativa, condutividade e difusividade termicas) e mecanicas (tensão de compressão, modulo de Young, tensão no plato, deformação e energia de impacto absorvida); foi analisada a influencia do tipo de pre-forma utilizada para produção das esponjas, nestas caracteristicas e propriedades. Os resultados mostraram boa reprodutibilidade do processo, principalmente quando da utilização de pre-formas de partículas medias e grosseiras nao sinterizadas. A densidade da esponja e a espessura da parede celular apresentam tendencia a aumentar com o aumento das dimensões das celulas produzidas em preformas de particulas mais grosseiras. Todas as amostras produzidas apresentaram condutividade termica da ordem de 10x inferior e difusividade termica da ordem de 4x superior as do metal maciço. O comportamento das esponjas em compressão estatica ou dinamica se mostrou tipico de materiais celulares, com reduzidos valores de modulo de Young e de tensão de compressão, grande plato de deformação plástica sem acréscimo de tensão, e elevados valores de deformação total e energia absorvida no impacto / Abstract: The aim of this work was the analysis of the thixoforming process to produce metallic sponges and the mechanical and metallurgical characterization of the product, searching for better understanding the influence of processing parameters in the material structural characteristics and properties. The aluminium alloy AA2011 was infiltrated in the semi-solid state into performs of NaCl particles with different sizes and in sintered and non sintered conditions. Cellular products were characterized concerning internal architecture, physical properties (actual and relative densities, thermal conductivity and diffusivity) and mechanical properties (Young's modulus, compressive strength, plateau stress and absorbed impact energy); it was analyzed the influence of processing parameters on the properties and characteristics of the produced sponges. Results showed good reproducibility of the process, mainly when medium and coarse non sintered space holder particles were employed. Density of the product as well as cell wall thickness increases as space holder particles sizes increase. All the sponges produced showed low thermal conductivity (~10x inferior compared to the bulk material) and high thermal diffusivity (~3x superior compared to the bulk alloy). Results of static and dynamic compression tests showed typical cellular material behaviour in all cases, presenting low values for Young's modulus and compressive strength, a well defined plateau of plastic deformation, high plastic deformation and high capacity of energy absorption in impact events / Mestrado / Materiais e Processos de Fabricação / Mestre em Engenharia Mecânica

Made available in DSpace on 2018-06-27T18:56:17Z (GMT). No. of bitstreams: 3 Marcia Bruschi.pdf: 1447481 bytes, checksum: 9167778faf308c7c784cba022bf22e92 (MD5) Marcia Bruschi.pdf.txt: 164415 bytes, checksum: 05463637576c35d9cd4085d38b088783 (MD5) Marcia Bruschi.pdf.jpg: 3373 bytes, checksum: b0a58d14b52a24617b54a774ddbef2fc (MD5) Previous issue date: 2010-08-23 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Acne is a chronic disease with an inflammatory disorder of the pilosebaceous follicle, characterized by open and closed comedones, papules, pustules and nodules. One of the drugs used to treat it is adapalene, which has fewer side effects compared to other retinoids, exerting an appropriate anti-inflammatory and comedolytic activity. Even with these advantages over other retinoids it is relevant the use in the exact site of action, the keratinocytes, focusing an increase of the drug activity and a reduction of side effects. As a result, nanocarrier systems have been extensively studied to improve the selectivity and efficiency of the formulations. This study presents as objective developing, characterize and evaluate the physical and chemical stability as well as the release and skin permeation of a semisolid topical formulation with base of Carbopol 940® containing adapalene-loaded nanocapsules. For this, they were needed physics, chemical, mathematics and pharmacy knowledgements, once Nanoscience presents a multidisciplinary character. All studies were performed comparing adapalene-loaded nanocapsules with the free form. The samples were stored at room temperature (25 ± 2 ° C), refrigerator (-4 ± 2 ° C) and oven (40 ± 2 ° C and 75 ± 5% RH) for 90 days and analyzed at 0, 7, 14, 30, 60 and 90 days in relation to physical-chemical characteristics organoleptic, rheological and drug contents. The average particle size was (201.1 ± 32.8 nm) and was maintained at refrigerator temperature and remained stable during the ninety days of analysis. The values of zeta potential (-23.4 ± 0.2 mV) and pH (5.94 ± 0.16) remained stable for all formulations regardless of storage temperature. The semisolid formulations, independent of the dispersion of the drug, exhibited a non-Newtonian behavior presenting pseudoplastic characteristics and determination of their values (85 a 98 %) remained unchanged during the 90 days of experiment. For release assays and skin permeation it was observed that most of the drug was retained on the surface and stratum corneum of the skin, but the adapalene-loaded nanocapsules obtained a higher permeation into the dermis and epidermis when compared with the free form. Through the results, we can conclude that the incorporation of nanocapsules of adapalene in a semisolid formulation in Carbopol® gels showed satisfactory physical-chemical stability, representing technological feasibility. / A acne é uma doença crônica com desordem inflamatória do folículo pilossebáceo, caracterizada por comedões, pápulas, pústulas e nódulos. Um dos fármacos utilizados para o tratamento é o adapaleno, uma molécula sintética que apresenta menos efeitos colaterais quando comparado a outros retinóides, exercendo uma atividade comedolítica e antiinflamatória apropriada. Mesmo com essas vantagens sobre os demais retinóides, ainda tornase relevante a administração mais direcionada no sítio de ação, os queratinócitos, objetivando um aumento da atividade do fármaco e uma redução dos efeitos colaterais. Em vista disso, sistemas nanocarreadores têm sido bastante estudados com objetivo de melhorar a seletividade e a eficiência das formulações. Este trabalho teve como objetivo desenvolver, caracterizar e avaliar a estabilidade físico-química, bem como a permeação cutânea de uma formulação semissólida com base de Carbopol 940® contendo adapaleno na forma nanoencapsulada. Para isso, foi necessário um conhecimento em física, química, matemática e farmácia, uma vez que a Nanociência apresenta um caráter interdisciplinar. Todos os estudos foram realizados comparando o adapaleno na forma nanoencapsulada com a forma livre. As amostras foram armazenadas à temperatura ambiente (25 ± 2 °C), geladeira (-4 ± 2 °C) e em estufa (40 ± 2 °C e 75 ± 5% UR) durante 90 dias e analisadas em 0, 7, 14, 30, 60 e 90 dias com relação às características físico-químicas, organolépticas, reológicas e teor do fármaco. O tamanho médio das partículas (201,1±32,8 nm) armazenadas em temperatura ambiente e geladeira mantiveram-se estáveis durante os noventa dias de análises. Os valores de potencial zeta (-23,4±0,2 mV) e pH (5,94±0,16) permaneceram estáveis para todas as formulações independente da temperatura de armazenamento. As formulações semissólidas independente da forma de dispersão do fármaco apresentaram fluxo não-newtoniano, comportamento pseudoplástico e mantiveram seus valores de doseamento (85 a 98 %) sem alterações durante os 90 dias de experimento. Para os testes de permeação cutânea, foi observado que a maior parte do fármaco ficou retida na superfície e estrato córneo da pele, porém para o fármaco nanoencapsulado (1,23 &#956;g/cm²) obteve-se uma maior permeação até a derme e epiderme quando comparada com a forma livre (0,84 &#956;g/cm²). Através dos resultados, pode-se concluir que a incorporação das suspensões contendo nanocápsulas de adapaleno em uma formulação semissólida utilizando como veículo o Carbopol 940® apresentou características físico-químicas e estabilidade adequada, representando viabilidade tecnológica.

Orientador: Maria Helena Robert / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecanica / Made available in DSpace on 2018-11-08T18:37:47Z (GMT). No. of bitstreams: 1 Delbin_Daniel_M.pdf: 8551361 bytes, checksum: 770e9d00eeb959cc6e40cf3f314faa4e (MD5) Previous issue date: 2006 / Resumo: Neste trabalho é estudada a viabilidade de produção de esponjas metálicas pela conformação de pasta tixotrópica da liga A2011, sobre camada de agente bloqueador (NaCl) posteriormente removido para formação da porosidade. Investiga-se a influência da temperatura de tratamento térmico, para obtenção da pasta semi-sólida, e da granulometria do agente bloqueador, na estrutura formada do material celular (aspecto geral, caracterização qualitativa e quantitativa dos poros, microestrutura da parede celular e densidade) e nas características de processo (forças de tixoforjamento e capacidade de penetração da pasta). São produzidos cilindros de material poroso metálico tipo sanduíche, compostos de camada porosa entre camadas maciças da liga, com três diferentes classes de porosidade: fina, média e grosseira. As esponjas foram submetidas à tomografia computadorizada e à análise metalográfica para sua caracterização estrutural. Os resultados obtidos mostram a viabilidade de obtenção de esponjas metálicas utilizando a tecnologia de semi-sólidos e o tipo de bloqueador utilizado. O sucesso do processo depende da fração líquida presente na pasta metálica tixotrópica, reduzida fração líquida pode resultar em incompleta infiltração e compressão das partículas do agente bloqueador. Nas condições analisadas a granulometria do agente bloqueador não teve influência sensível na qualidade do produto. A densidade do material poroso aumenta com o aumento da temperatura de processo, devido ao aumento da espessura de paredes metálicas na estrutura porosa / Abstract: The work analyses the possibility of the production of cellular material by pressing the A2011 alloy in the thixotropic semi-solid state, into a space holder pre-form. Space holder particles used are NaCl, which are removed from the product after the forming operation, resulting the porous material. It is investigated the influence of the thixoforming temperature and the size of space holder particles, in the structure of the obtained porous material (general aspect, quantitative and qualitative characterization of porosity, microstructure of cell walls and density of the product), as well as in the processing characteristics (required forces for infiltration, penetration ability of the slurry in the salt pre-form). Cylindrical samples, sandwich type, with a porous layer inserted between layers of compact alloy are produced, presenting three different ranges of porosity. The cellular material obtained contains opened porosity, being characterized as sponge. Products were analyzed by tomography and metallographic techniques. Results show that the proposed process is able to produce acceptable porous material, with a simple and low cost technique. The quality of the product depends rather on the processing temperature than on the size of space holder particles. Low liquid fraction in the thixotropic slurry can lead to incomplete infiltration and deformation of the pre-form. In the analyzed conditions, influence of the size of space holder particles could be observed neither in the processing ability nor in the quality of the product. Density of produced porous material increases as processing temperature increases, due to the increase of thickness of cell walls / Mestrado / Materiais e Processos de Fabricação / Mestre em Engenharia Mecânica

In several applications of casting, dendritic microstructure is not desirable as it results in poor mechanical properties. Enhancing fluid flow in the mushy zone by stirring is one of the means to suppress this dendritic growth. Strong fluid flow detaches the dendrites formed at the solid-liquid interface and carries them into the mould to form slurry. When this slurry solidifies, the microstructure is characterized by globular, non-dendritic primary phase particles, separated and enclosed by a near-eutectic lower-melting secondary phase. This property represents a great potential for further processing in semisolid forming (SSF) by various techniques such as pressure die casting and forging. Among all currently available methods, linear electromagnetic (EM) stirring is considered as one of the most suitable routes for large scale production of semisolid feed stock. One of the biggest advantages of EM stirring is that the stirring intensity and direction can be modulated externally and in a non-intrusive manner. With this viewpoint, the primary objective of the present research is to investigate rheocasting using linear electromagnetic stirring. A systematic development of a linear electromagnetic stirrer (LEMS) is the subject of the first part of the thesis. The LEMS consists of a set of six primary coils displaced in space. These coils are excited by a three-phase power supply to produce an axially travelling magnetic field. The metal to be stirred is placed in the annular space of the stirrer. The travelling field induces secondary current in the molten metal. The current and magnetic fields interact to generate a net mechanical force in the metal, commonly termed as the Lorentz force. The molten metal is stirred under the influence of this force. Two prototype stirrers, one for low melting alloys and the other for aluminium alloys are developed. The stirrers are characterized by measuring forces on low melting point alloy and on solid aluminum cylinders placed inside the annular space of the stirrer. As an outcome of these tests, a non-intrusive method of detecting stirring of liquid metal is developed. The development of a rheocasting mould for the LEMS forms the second part of the work presented in the thesis. The mould design and cooling arrangement are such that solidification in the mould is primarily unidirectional. Heat from the solidifying metal is extracted at the bottom of the mould, so that the axisymmetric EM stirring effectively shears the dendrites formed at the solid-liquid interface. The outer surface of the mould is cooled with water or air exiting from 64 jets, each of 4 mm diameter. Such an arrangement provides a high heat transfer coefficient and a wide range of cooling rate in the metal ranging from 0.01 to 10 K/s. Temperature is measured at various depths in the solidifying melt and at other key locations in the mould to assess the various heat transfer mechanisms. The results from the rheocasting experiments using the above mould and LEMS are presented in the third and final part of the thesis. Such studies are required for understanding the solidification process in presence of electromagnetic stirring and for highlighting the important issues connecting solidification, fluid flow, dendrite fragmentation and the resulting microstructure. A series of experiments are performed with A356 (Al-7Si-0.3Mg) alloy. Experiments are conducted with various combinations of operating parameters, and the resulting microstructures and cooling curves at various locations are examined. The key process parameters are stirring current, cooling rate, pouring temperature, and stirring current frequency. The parametric studies also include the case without EM stirring in which liquid aluminium is poured into the rheocast mould without powering the LEMS. It is found that stirring at high currents produces non-dendritic microstructures at all locations of the billet. For lower currents, however, dendritic microstructures are observed in regions outside the zone of active stirring. Stirring also enhances heat loss from the exposed top surface, leading to solid front advancement from the top as well. Without EM stirring, microstructures are found to be dendritic everywhere. The percentage of primary α-Al phase and its number density are found to increase with stirring intensity. With a decrease in cooling rate with air as the coolant, the average grain size of primary α-Al phase increases. Excitation frequency is found to be an important parameter, with lower frequencies generating a more uniform force field distribution, and higher frequencies enhancing induction heating. At higher frequencies, the effect of higher induction heating results in the formation of larger and coarser primary phase grains. This phenomenon has led to the development of a one-step process for rheocasting and heat treatment of billets.

There is limited knowledge on provisions used to ensure swallowing safety, nutritional adequacy and sensory acceptability of pureed foods in long-term care homes (LTCHs). The overall aim for this research was to expand knowledge of pureed food production in LTCHs, to study the impact of varying ingredients and preparation on sensory and nutrition and to model perceived oral textures in pureed food. Qualitative interviews with dietary staff (n=53) in 25 LTCHs showed a variety of challenges and practices in production, affecting overall quality. Pureed turkey varying in added liquid, meat muscle and seasoning method and pureed carrots varying in thickener type were evaluated by a descriptive sensory panel (n=10). Results indicate that small formulation changes can have a significant impact on the nutrition and sensory properties of pureed food. Instrumental tests using a viscometer, line-spread test and texture analyzer showed different strengths in predicting variation in orally-perceived textures. / Funding for this project has been provided by Agriculture and Agri-Food Canada through the Canadian Agricultural Adaptation Program (CAAP). In Ontario, this program is delivered by the Agricultural Adaptation Council (AAC).