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Vytěsnění minoritních akcionářů / Squeeze outMorava, Tomáš January 2007 (has links)
Práce se zabývá analýzou, legislativní úpravou a praktickou aplikací squeeze out, neboli vytěsnění minoritních akcionářů z akciových společností. Na základě analýzy teoretických konceptů nabídek převzetí obhajuje proces squeeze out jako legitimní a efektivní nástroj zvýšení flexibility řízení a správy společností. Práce poskytuje návody a doporučení majoritním akcionářům jak co nejlépe provést squeeze out. Práce dále poskytuje doporučení pro zákonodárné orgány ČR a EU, jakož i pro orgány dohledu nad kapitálovými trhy, na základě kterých by měla být provedena revize legislativní úpravy vytěsnění.
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Performance of a Short Open-End Squeeze Film Damper With Feed Holes: Experimental Analysis of Dynamic Force CoefficientsBradley, Gary Daniel 16 December 2013 (has links)
With increasing rotor flexibility and shaft speeds, turbomachinery undergoes large dynamic loads and displacements. Squeeze film dampers (SFDs) are a type of fluid film bearing used in rotating machinery to attenuate rotor vibration, provide mechanical isolation, and/or to tune the placement of system critical speeds. Industry has a keen interest in designing SFDs that are small, lightweight, and mechanically simple. To achieve this, one must have a full understanding of how various design features affect the SFD forced performance.
This thesis presents a comprehensive analysis, experimental and theoretical, of a short (L=25.4 mm) open ends SFD design incorporating three lubricant feed holes (without a circumferential feed groove). The damper radial clearance (c=127 μm), L/D ratio (0.2), and lubricant (ISO VG2) have similar dimensions and properties as in actual SFDs for aircraft engine applications. The work presents the identification of experimental force coefficients (K, C, M) from a 2-DOF system model for circular and elliptical orbit tests over the frequency range ω=10-250Hz. The whirl amplitudes range from r=0.05c-0.6c, while the static eccentricity ranges from eS=0-0.5c. Analysis of the measured film land pressures evidence that the deep end grooves
(provisions for installation of end seals) contribute to the generation of dynamic pressures in an almost purely inertial fashion. Film land dynamic pressures show both viscous and inertial effects. Experimental pressure traces show the occurrence of significant air ingestion for orbits with amplitudes r>0.4c, and lubricant vapor cavitation when pressures drop to the lubricant saturation pressure (PSAT~0 bar). Identified force coefficients show the damper configuration offers direct damping
coefficients that are more sensitive to increases in static eccentricity (eS) than to increases in amplitude of whirl (r). On the other hand, SFD inertia coefficients are more sensitive to increases in the amplitude of whirl than to increases in static eccentricity. For small amplitude motions, the added or virtual mass of the damper is as large as 27% of the bearing cartridge mass (MBC=15.15 kg). The identified force coefficients are shown to be insensitive to the orbit type (circular or elliptical) and the number of open feed holes (3, 2, or 1).
Comparisons of damping coefficients between a damper employing a circumferential feed groove1 and the current damper employing feed holes (no groove), show that both dampers offer similar damping coefficients, irrespective of the orbit amplitude or static eccentricity. On the other hand, the grooved damper shows much larger inertia force coefficients, at least ~60% more.
Predictions from a physics based model agree well with the experimental damping coefficients, however for large orbit motion, over predict inertia coefficients due to the model neglecting convective inertia effects.
Credence is given to the validity of the linearized force coefficients by comparing the actual dissipated energy to the estimated dissipated energy derived from the identified force coefficients. The percent difference is below 25% for all test conditions, and in fact is shown to be less than 5% for certain combinations of orbit amplitude (r), static eccentricity (eS), and whirl frequency (ω).
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Effect Of Squeeze Film Flow On Dynamic Response Of MEMS Structures With Restrictive Flow Boundary ConditionsShishir Kumar, * 06 1900 (has links) (PDF)
There are many ways in which the surrounding media, such as air between an oscillating MEMS structure and a fixed substrate, can affect the dynamic response of a MEMS transducer. Some of these effects involve dissipation while others involve energy transfer. Transverse oscillations of a planar structure can cause a lateral air flow in small gaps that results in pressure gradients. The forces due to the built–up pressure are always against the vibration of the structure and have characteristics of damper and stiffener. In this work, we study the squeeze film phenomenon due to the interaction between the air–film and the structure in the presence of restrictive flow boundary conditions. It is known that the squeeze film damping due to the air trapped between the oscillating MEMS structure and the fixed substrate often contributes to maximum energy dissipation. We carry out an analysis to estimate damping and stiffness in cases with restrictive flow boundaries in dynamic MEMS devices. While the studies reported in the present work address fluid flow damping with restrictive flow boundaries, the analysis of air-flow shows another important phenomenon of enhanced air-spring stiffness. This study is discussed separately in the context of spring stiffening behavior in MEMS devices exhibiting squeeze film phenomenon.
First a theoretical framework for modeling squeeze film flow is established and this is followed with analytical and numerical solutions of problems involving squeeze film phenomenon. Modeling of squeeze film effects under different flow conditions is carried out using Reynold’s equation. The problem of squeeze film damping in MEMS transducers
is more involved due to the complexities arising from different boundary conditions of the fluid flow. In particular, we focus our attention on estimation of damping in restricted flow boundaries such as only one side vented and no side vented passive boundary conditions. Damping coefficient for these cases are extracted when the fluid is subjected to an input velocity profile according to a specific mode shape at a given frequency of oscillation. We also explain the squeeze film flow in restricted boundaries by introducing the concept of passive and active boundary conditions and analyzing the pressure gradients which are related to the compressibility of the air in the cavity. Passive boundary conditions is imposed by specifying the free flow or no flow along one of the edges of the cavity, whereas, active boundary condition is imposed by the velocity profile being specified at the interface of the cavity with the oscillating structure.
Some micromechanical structures, such as pressure sensors and ultrasound transducers use fully restricted or closed boundaries where the damping for such cases, even if small, is very important for the determination of the Q–factor of these devices. Our goal here is to understand damping due to flow in such constrained spaces. Using computational fluid dynamics (ANSYS–FLOTRAN), the case of fully restricted boundaries is studied in detail to study the effect of important parameters which determines the fluid damping, such as flow length of the cavity, air–gap height, frequency of oscillations and the operating pressure in the cavity. A simulation strategy is developed using macros programming which overcomes some of the limitations of the existing techniques and proves useful in imposing a non–uniform velocity and the extraction of damping coefficient corresponding to the flexibility of the structure in specific oscillation modes. Rarefaction effects are also accounted for in the FEM model by introducing the flow rate coefficient, or, alternatively using the concept of effective viscosity. The analysis carried out for the fully restricted case is motivated by the analytical modeling of squeeze film phenomenon for a wide range of different restricted boundaries, and analyzing the resulting pressure gradient patterns. We show that significant damping exists even in fully restricted boundaries due to lateral viscous flow. This is contrary to known reported results, which neglect damping in such cases. The result indicates that in fully restrictive fluid flow boundaries or in a closed cavity, air damping cannot be neglected at lower oscillation frequencies and large flow length to air-gap ratio if the active boundary has a non-uniform velocity profile.
Analysis of air-flow in the case of restricted flow boundaries shows another important phenomenon of enhanced air-spring stiffness. It is found that fluid film stiffness has a nonlinear dependence on various parameters such as air-gap to length ratio, fluid flow boundary conditions and the frequency of oscillation. We carry out analysis to obtain the dynamic response of MEMS devices where it is significantly affected by the frequency dependent stiffness component of the squeeze film. We show these effects by introducing frequency dependent stiffness in the equation of motion, and taking examples of fluid boundary conditions with varying restriction on flow conditions. The stiffness interaction between the fluid and the structure is shown to depend critically on stiffness ratios, and the cut-off frequency. It is also inferred that for a given air–gap to flow length ratio, the spring behaviour of the air is independent of the flow boundary conditions at very high oscillation frequencies. Hence, we limit our focus on studying the effect of fluid stiffness in the regime where it is not fully compressible. For non-resonant devices, this study finds its utility in tuning the operating frequency range while for resonant devices it can be useful to predict the exact response. We show that it is possible to design or tune the operating frequency range or shift the resonance of the system by appropriate selection of the fluid flow boundary conditions.
The emphasis of the present work has been toward studying the effect of squeeze film flow on dynamic response of MEMS structures with restrictive flow boundary conditions. Estimation of energy dissipation due to viscous flow cannot be ignored in the design of MEMS which comprise of restricted flow boundaries. We also remark that modeling of a system with squeeze film flow of the trapped air in terms of frequency independent parameters, viz. damping and stiffness coefficient, is unlikely to be very accurate and may be of limited utility in specific cases. Although the central interest in studying squeeze film phenomenon is on the damping characteristics because of their direct bearing on energy dissipation or Q–factor of a MEMS device, the elastic behaviour of the film also deserves attention while considering restrictive flow boundary conditions.
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Interní audit finanční situace v kontextu změny právní formy podnikání společnostiPojerová, Lenka January 2008 (has links)
Práce hodnotí z pohledu interního auditu finanční zdraví společnosti Ideal Standard pomocí finanční analýzy. Zabývá se obdobím před a po změně právní formy podnikání z akciové společnosti na společnost s ručením omezeným a vytěsněním minoritních akcionářů. V závěru je v auditorské zprávě je provedeno srovnání obou období.
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Identification of squeeze-film damper bearings for aeroengine vibration analysisGroves, Keir Harvey January 2011 (has links)
The accuracy of rotordynamic analysis of aeroengine structures is typically limited by a trade-off between the capabilities and the computational cost of the squeeze-film damper (SFD) bearing model used. Identification techniques provide a means of efficiently implementing complex nonlinear bearing models in practical rotordynamic analysis; thus facilitating design optimisation of the SFD and the engine structure. This thesis considers both identification from advanced numerical models and identification from experimental tests. Identification from numerical models is essential at the design stage, where rapid simulation of the dynamic performance of a variety of designs is required. Experimental identification is useful to capture effects that are difficult to model (e.g. geometric imperfections). The main contributions of this thesis are: • The development of an identification technique using Chebyshev polynomial fits to identify the numerical solution of the incompressible Reynolds equation. The proposed method manipulates the Reynolds equation to allow efficient and accurate identification in the presence of cavitation, the feed-groove, feed-ports, end-plate seals and supply pressure. • The first-ever nonlinear dynamic analysis on a realistically sized twin-spool aeroengine model that fulfills the aim of taking into account the complexities of both structure and bearing model while allowing the analysis to be performed, in reasonable time frames, on a standard desktop computer. • The introduction and validation of a nonlinear SFD identification technique that uses neural networks trained from experimental data to reproduce the input-output function governing a real SFD. Numerical solution of the Reynolds equation, using a finite difference (FD) formulation with appropriate boundary conditions, is presented. This provides the base data for the identification of the SFD via Chebyshev interpolation. The identified 'FD-Chebyshev' model is initially validated against the base (FD) model by application to a simple rotor-bearing system. The superiority of vibration prediction using the FD-Chebyshev model over simplified analytical SFD models is demonstrated by comparison with published experimental results. An enhanced FD-Chebyshev scheme is then implemented within the whole-engine analysis of a realistically sized representative twin-spool aeroengine model provided by a leading manufacturer. Use of the novel Chebyshev polynomial technique is repeatedly demonstrated to reduce computation times by a factor of 10 or more when compared to the basis (FD) model, with virtually no effect on the accuracy. Focus is then shifted to an empirical identification technique. Details of the commissioning of an identification test rig and its associated data acquisition system are presented. Finally, the empirical neural networks identification process for the force function of an SFD is presented and thoroughly validated. When used within the rotordynamic analysis of the test rig, the trained neural networks is shown to be capable of predicting complex nonlinear phenomena with remarkable accuracy. The results show that the neural networks are able to capture the effects of features that are difficult to model or peculiar to a given SFD.
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Experimental Study of Liquid Squeeze-flow as it Relates to Human Voice ProductionLo Forte, Daniel Victor 27 April 2011 (has links) (PDF)
Approximately 7.5 million people suffer from voice disorders in the United States. Previous studies indicate that the quality of the fluid layer that coats the vocal folds appears to be different for people with voice disorders than for people whose voice is considered normal. These studies suggest that the composition and/or physical properties of the fluid layer may contribute to voice disorders. Despite these findings, little research has been undertaken to investigate the role of the fluid layer on voice, and in almost all cases, the fluid layer is considered to be insignificant. The purpose of this research was to investigate the role of the fluid layer and the potential it may have to influence voice production; particularly, to identify some aspects of the fluid layer that have the potential to contribute to voice disorders. In order to investigate the potential significance of the effects of a fluid layer on vocal fold operation, an existing lumped model was modified to incorporate the Newtonian squeeze-flow equation as a fluid model during the colliding portion of the oscillatory cycle. Results indicated that thicker films produced more significant deviations from the case with no fluid layer. Experimental testing was performed to validate existing analytical equations for squeezing flow of Newtonian and non-Newtonian fluids confined between parallel axisymmetric plates. Based on available published data on the rheological properties of the fluid layer found on the surface of the vocal folds, several fluids with a range of fluid properties were selected. Reasonable agreement was found for much of data collected for the Newtonian fluid cases within measurement tolerances. For the non-Newtonian cases, the constitutive equation was found to be in poor agreement with the measured physical characteristics of the selected non-Newtonian fluids. A summary of the collected experimental data is provided so that it can be used in for validation and comparison in future research. A preliminary computational model based on the classical two-mass vocal fold model was implemented which incorporated squeezing effects of a thin Newtonian film of fluid on the surface of the vocal folds. Results indicated that the fluid layer may not be insignificant, although further tests and modeling are required. Finally, different fluids were applied to a physical model of the vocal folds and measurements were taken to determine the effects of the application of fluid. The results showed significant changes in the vocal fold model response that indicated the fluid layer affects vocal fold operation in important ways. Some of the changes in response could not be attributed solely to the fluid layer. Suggestions regarding future work with physical model testing are given which may help clarify the effects of a fluid layer on vocal fold flow-induced vibration.
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Rheological Properties of Peanut Paste and Characterization of Fat Bloom Formation in Peanut-Chocolate ConfectioneryBuck, Vinodini 05 May 2010 (has links)
Fat bloom in chocolates is the gray-white discoloration and dullness that can occur on the surface of the confectionery. Fat bloom is a common quality defect that can result from temperature fluctuations during storage. Chocolates candies with peanuts or other nut fillings are more prone to fat bloom compared to plain chocolates, due to a release of incompatible nut oils into the chocolate matrix. The overall goal of this study was to determine if differences in triacylglycerol (TAG) composition and rheological properties of high, medium, and normal oleic peanuts influence fat bloom formation. All three peanut varieties showed high concentrations of triolein. Normal oleic peanuts had a slightly higher trilinolein than high and medium oleic peanuts, which contained trilinolein in trace amounts. Peanut pastes from the three peanut varieties all had a minimum apparent yield stress, and all pastes showed varying degrees of shear thinning. The apparent yield stress of high and normal oleic pastes was higher than the apparent yield stress of medium oleic paste. The absolute value of the flow index behavior was 1 for the high oleic peanut paste, suggesting friction in the experimental apparatus, even with use of Teflon plates. The peanut chocolate candies took around 45 days for significant dulling of the chocolates with temperature cycling between 26-29 °C approximately every 26 hours. Optical microscopy scans showed differences in glossiness and surface textural attributes of the unbloomed and bloomed peanut chocolate confectionery. Consumer evaluation showed some differences in the glossiness and significant differences in surface texture of unbloomed and bloomed chocolates. A majority (62%) of the survey respondents had seen whitish discoloration in chocolates and 40% of the respondents thought this is because the chocolate had grown old. / Ph. D.
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Using Non-Lubricated Squeeze Flow to Obtain Empirical Parameters for Modeling the Injection Molding of Long-Fiber CompositesLambert, Gregory Michael 29 October 2018 (has links)
The design of fiber-reinforced thermoplastic (FRT) parts is hindered by the determination of the various empirical parameters associated with the fiber orientation models. A method for obtaining these parameters independent of processing doesn't exist. The work presented here continues efforts to develop a rheological test that can obtain robust orientation model parameters, either by fitting directly to orientation data or by fitting to stress-growth data.
First, orientation evolution in a 10 wt% long-glass-fiber-reinforced polypropylene during two homogeneous flows (startup of shear and planar extension) was compared. This comparison had not been performed in the literature previously, and revealed that fiber orientation is significantly faster during planar extension. This contradicts a long-held assumption in the field that orientation dynamics were independent of the type of flow. In other words, shear and extension were assumed to have equal influence on the orientation dynamics.
A non-lubricated squeeze flow test was subsequently implemented on 30 wt% short-glass-fiber-reinforced polypropylene. An analytical solution was developed for the Newtonian case along the lateral centerline of the sample to demonstrate that the flow is indeed a superposition of shear and extension. Furthermore, an existing fiber orientation model was fit to the gap-wise orientation profile, demonstrating that NLSF can, in principle, be used to obtain fiber orientation model parameters. Finally, model parameters obtained for the same FRT by fitting to orientation data from startup of steady shear are shown to be inadequate in predicting the gap-wise orientation profile from NLSF.
This work is rounded out with a comparison of the fiber orientation dynamics during startup of shear and non-lubricated squeeze flow using a long-fiber-reinforced polypropylene. Three fiber concentrations (30, 40, and 50 wt%) were used to gauge the influence of fiber concentration on the orientation dynamics. The results suggest that the initial fiber orientation state (initially perpendicular to the flow direction and in the plane parallel to the sample thickness) and the fiber concentration interact to slow down the fiber orientation dynamics during startup of shear when compared to the dynamics starting from a planar random initial state, particularly for the 40 and 50 wt% samples. However, the orientation dynamics during non-lubricated squeeze flow for the same material and initial orientation state were not influenced by fiber concentration. Existing orientation models do not account for the initial-state-dependence and concentration-dependence in a rigorous way. Instead, different fitting parameters must be used for different initial states and concentrations, which suggests that the orientation models do not accurately capture the underlying physics of fiber orientation in FRTs. / Ph. D. / In order to keep pace with government fuel economy legislation, the automotive and aerospace industries have adopted a strategy they call “lightweighting”. This refers to decreasing the overall weight of a car, truck, or plane by replacing dense materials with less-dense substitutes. For example, a steel engine bracket in a car could be replaced with a high-temperature plastic reinforced with carbon fiber. This composite material will be lighter in weight than the comparable steel component, but maintains its structural integrity. Thermoplastics reinforced with some kind of fiber, typically carbon or glass, have proven to be extremely useful in meeting the demands of lightweighting. Thermoplastics are materials that can be melted from a feedstock (typically pellets), reshaped in the melted state through use of a mold, and then cooled to a solid state, and some common commodity-grade thermoplastics include polypropylene (used for Ziploc bags) and polyamides (commonly called Nylon and used in clothing). Although these commodity applications are not known for their strength, the fiber reinforcement in the automotive applications significantly improves the structural integrity of the thermoplastics. The ability to melt and reshape thermoplastics make them incredibly useful for highthroughput processes such as injection molding. Injection molding takes the pellets and conveys them through a heated barrel using a rotating screw. The melted thermoplastic gathers at the tip of the barrel, and when a set volume is gathered, the screw is rammed forward to inject the thermoplastic into a closed mold of the desired shape. This process typically takes between 30-60 seconds per injection. This rate of production is crucial for the automotive industry, as manufacturers need to put out thousands of parts in a short period of time. The improvement to mechanical properties of the thermoplastics is strongly influenced by the orientation of the reinforcing fibers. Although design equations connecting the part’s mechanical properties to the orientation of the fibers do exist, they require knowledge of the orientation of the fibers throughout the part. Fibers in injection-molded parts have an extremely complicated orientation v state. Measuring the orientation state at each point would be too laborious, so empirical models tying the flow of the thermoplastic through the mold to the evolving orientation state of the fibers have been developed to predict the orientation state in the final part. These predictions can be used in lieu of direct measurements in the part design equations. However, the orientation models rely on empirical fitting parameters which must be obtained before injection molding simulations are performed. There is currently no standard test for obtaining these parameters, nor is there a standardized look-up table. The work presented in this dissertation continues efforts to establish such a test using simple flows in a laboratory setting, independent of injection molding. Previous work focused exclusively on using shearing flow (e.g. pressure-driven flow found in injection molding) to obtain these parameters. However, when these parameters were used in simulations of injection molding, the agreement between measured and predicted fiber orientation was mediocre. The work here demonstrates that another type of flow, namely extensional flow, must also be considered, as it has a non-negligible influence on fiber orientation. this is crucial to injection molding, as injection molding flows have elements of both shearing and extensional flow. The first major contribution from this dissertation demonstrates that extensional flow (e.g. stretching a film) has a much stronger influence than shearing flow, even at the same overall rate of deformation. The second major contribution used a combination shear/extensional flow to demonstrate that the empirical model parameters, thought to be characteristic of the composite, are actually strongly influenced by the type of flow experienced by the sample, and that no single set of model parameters can fit the full orientation state. The final major contribution extends the previous case to long-fiber reinforcement at multiple fiber concentrations which are of industrial interest. This finds the same results, that the model parameters are dependent on the type of flow experienced by the sample. The flow-dependence of the parameters is a crucial point to address in future work, as the flows found in injection molding contain both shearing and extensional flow. By further developing this flow-type dependence, future injection molding simulations should become more accurate, and this will make computer-aided injection-molded part design much more efficient.
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Análise comparativa de argamassas colantes de mercado através de parâmetros reológicos. / Comparative analysis of commercial dry-set mortars using rheological parameters.Costa, Marienne do Rocio de Mello Maron da 31 January 2006 (has links)
O presente trabalho propõe o entendimento do comportamento no estado fresco de argamassas colantes, com base na caracterização reológica e físico-química de diferentes composições comerciais, servindo de base para analisar o fenômeno de deslizamento, a partir do ensaio estabelecido na norma brasileira. Para isso, foi utilizado o ensaio Squeeze flow" (escoamento por compressão axial), empregado na caracterização de argamassas de revestimento no laboratório de microestrutura do CPqDCC da EPUSP, como ferramenta de análise do comportamento de argamassas colantes. Neste ensaio, o escoamento do material decorre da aplicação de uma carga de compressão sobre a amostra no estado fresco, a qual ocasiona deslocamentos no seu interior devido a esforços de cisalhamento radiais originados durante o fluxo. O critério de seleção das argamassas colantes comerciais (tipo AC-I) se baseou nos resultados do ensaio de deslizamento, escolhendo-se duas com resultado muito abaixo do limite especificado, duas com resultado próximo do limite e outras duas com resultado acima do mesmo. A composição química e física foi caracterizada com o objetivo de embasar a análise dos resultados obtidos no Squeeze flow". A separação da fração fina das argamassas na peneira no.200 contribuiu para o conhecimento da viscosidade da pasta e da sua influência no comportamento reológico das argamassas. Foi observado que as argamassas estudadas apresentam diferenças de composição físico-química e de comportamento reológico. As diferenças de comportamento reológico das argamassas decorrem, provavelmente, de ação sinérgica de alguns parâmetros da composição, com destaque para a distribuição granulométrica. O Squeeze flow" mostrou-se uma ferramenta adequada na caracterização das argamassas colantes e contribuiu para explicar o deslizamento estabelecido na norma brasileira, pela proposição de modelos hipotéticos de comportamento. / Present thesis proposes the study of plastic-state behaviour of dry-set mortars based on the rheological and physicochemical characterization of different commercially available dry-set mortar compositions. Such characterization served as basis for the analysis of dry-set mortar slip phenomena using the tests recommended by brazilian standards (NBR). The Squeeze Flow test (slip by axial compression) originally used for coating mortars characterization by the EPUSP CPqDDC Microstructure Laboratory was adopted as a test tool for analysing the dry-set mortar behaviour. In the mentioned test the material slip is obtained by compressing the sample in its plastic state which caused internal displacements due to radial shearing tensions originated during the mentioned slip. The dry-se mortars (all of them AC-I type) used in the study were selected based in the slip tests results against brazilian standards specified limits resulting in the selection of two dry-set mortars below the specified limit, two dry-set mortars close to the specified limit and dry-set mortars above the specified limit. Chemical and physical compositions were characterized in order to serve as basis for Squeeze Flow results analysis. Fine fraction segregation, using number 200 sieve contributed to understanding of plastic-state mortar viscosity and its influence in mortar rheological behaviour. It was observed diverse physicochemical and rheological behaviour among the studied dry-set mortars. The rheological behaviour diversity of dry-set mortars were due to the synergy among some composition parameters, specially the granular distribution. The Squeeze Flow was considered a suitable tool for the characterization of dry-set mortars and contributed to develop hypotetical behaviour models that allowed to explain the slip as stated by brazilian standards.
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Caracterização reológica de argamassas colantes. / Adhesive mortars rheological characterization.Kudo, Elisabete Kioko 04 October 2012 (has links)
As argamassas colantes são produtos constituídos por areia natural ou artificial, ligantes e aditivos químicos que cumprem uma função de adesivo para assentamento de revestimentos em pisos e paredes. Sob o ponto de vista reológico, a argamassa colante é um material multifásico formado por uma pasta que envolve agregados minerais. Atualmente, o único teste preconizado em norma a fresco é o ensaio de deslizamento, que apesar de ter baixo custo e relativa facilidade de execução em laboratório. As grandes desvantagens desse método são: imprecisão e a baixa repetibilidade, além de ser insuficiente para efetuar uma avaliação mais completa desses produtos no estado fresco. Assim, técnicas de caracterização reológica (Squeeze Flow, Pull Out Flow e reometria rotacional) foram especificadas e aplicadas, como alternativa tecnológica para avaliação de argamassas colantes. Porém, o potencial da configuração tradicional do ensaio de Squeeze Flow e a reometria rotacional foram pouco explorados neste tipo de argamassa. Neste estudo foi necessário empreender ajustes de configuração. O objetivo desta dissertação foi o de aplicar métodos de caracterização reológica em argamassas colantes de mercado (ACI e ACIII) de certo fabricante e ACI formulada em laboratório composta por areias com morfologias diferentes que permitissem identificar suas características relevantes no estado fresco, avaliar a influência dos parâmetros experimentais do método de Squeeze Flow (principalmente em relação à configuração e parâmetros), avaliar a adesividade das argamassas no estado fresco e aplicar o método de reometria rotacional para avaliação das energias de mistura e reológica. Os experimentos para avaliação das configurações e parâmetros do ensaio de Squeeze Flow e Pull Out Flow mostraram que tais métodos foram sensíveis para diferenciar as argamassas e refletiram o que, na prática, é percebido: ACIII (Argamassa Colante do Tipo III) tem maior consistência que ACI (Argamassa 7 Colante do Tipo I), além de mostrar que são sensíveis às diferentes taxas de deslocamento, teores de água e morfologia de agregados. Já a reometria rotacional mostrou-se sensível para identificar e diferenciar a cinética de mistura das argamassas colantes ACI e ACIII. Os resultados indicaram que o tempo de mistura de 150 segundos foi eficiente e suficiente para homogeneizar e estabilizar as argamassas testadas, e que a argamassa do tipo ACI apresenta maior dificuldade de mistura e resulta em uma suspensão com maior viscosidade e tensão de escoamento do que a argamassa ACIII. Por fim, a aplicação dos métodos de caracterização reológica em argamassas ACI compostas por areias com morfologias diferentes, indicou que o método de Squeeze Flow mostrou ser sensível para diferentes teores de água, em argamassas compostas por areia artificial. As curvas de carga de compressão da argamassa ACI com areia artificial mostraram serem superiores às formuladas argamassas com areia natural, indicando que, com a mesma proporção de insumos e teor de água (volume), as argamassas não possuem perfis reológicos similares. / Adhesive mortars are products constituted of natural or artificial sand, binder (cement) and chemical additives which serve as an adhesive for laying floor and wall tiles. From the rheological point of view, the adhesive mortar is a multiphase material consisting of a paste that coats mineral aggregates. Currently, the only test done is the slip test, which has low cost and has a relatively easy execution. The disadvantage of this method is not to have a good repeatability and is not sufficient to evaluate products in fresh state. Thus, techniques of rheologic characterization (flow squeeze, pull out flow and rotational rheometry) were applied as technologic alternatives for evaluation of adhesive mortars. However, the potential of the traditional configuration of the Squeeze Flow test and rotational rheometry were not explored in this type of product due to the requirement of configuration settings. The purpose of this dissertation is to apply advanced methods for rheological characterization of adhesive mortars in order to identify important characteristics of fresh-state application; evaluation of the influence of the squeeze-flow experimental method (mainly due to configuration and parameters); applied rheometry techniques to evaluate the mixing energy; and to evaluate the adhesiveness of fresh mortars. The evaluation of the configuration and parameters of the Squeeze Flow and Pull Out Flow showed that the methods were sensible enough to differentiate mortars in the same way that is perceived in practice: ACIII has greater consistency than ACI, also shows that are sensitive to different rates of displacement, water content and morphology of aggregates. The mixing and rotational rheometry showed that the method is sensitive to identify and differentiate the kinetics of mixing for ACI and ACIII mortars. The results indicate that the mixing time of 150 seconds was effective to homogenize and disperse the mortars. The mixing and flow torque values are higher for ACI than for ACIII, indicating that ACI is more difficult to be mixed and has a higher viscosity and yield stress than ACIII.
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