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Kelly, Adrian L. "On-line shear and extensional rheometry of polymer melts in the extrusion process." Thesis, University of Bradford, 1997. http://hdl.handle.net/10454/2796.
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A novel on-line capillary rheometer (OLR) was used to examine the shear and extensional characteristics of polyolefin melts during twin screw extrusion (TSE). Comparisons with off-line rheometry were made using a twin-bore capillary rheometer and a modular in-line slit die rheometer (ILR) provided in-line rheometry comparisons. Both capillary rheometers were controlled via PCs running dedicated software, and the extrusion line and ELR were fully instrumented allowing real-time process monitoring to be carried out by IBM compatible PCs via data acquisition hardware and software. The prototype OLR was developed by the re-design of several key features including an instrumented transfer section and capillary die block which facilitated the use of various die geometries. Shear and extensional on-line rheometry of three polyethylenes (linear and branched), and four molecular weight grades of polypropylene were examined, and a direct comparison with off-line capillary rheometry showed a good correlation. The effect of a high loading of filler on two of the polyethylenes was investigated. In-line shear stress and entry pressure measurements showed a reasonable correlation with on-line rheometry. A study of entry flows in the OLR using capillary dies approaching orifice showed non-linearities occurred at very low capillary length to diameter(L:D) ratios, and this was repeatable using off-line rheometry. Predicted zero length entry pressures (Po) were used to estimate apparent extensional viscosity using a number of standard models. Melt instability and capillary wall slip were also investigated using on-line rheometry. Melt pressure and temperature in the twin screw extruder and OLR were monitored at various process conditions to examine the ability of the OLR to condition melt during testing, and the effect of OLR testing on extrusion conditions. Pressure variation in the extruder, OLR and off-line rheometer were compared in order to quantify process noise. The effect of OLR testing on melt rheology and polymer molecular weight were examined using off-line rheometry and gel permeation chromatography(GPC).
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Sridharan, Harini. "COUPLED DYNAMICS OF HEAT TRANSFER AND FLUID FLOW IN SHEAR RHEOMETRY." University of Akron / OhioLINK, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=akron1597346164780318.
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Anderson, Fredrik. "Rheological changes at the air-liquid interface and examining different kind of magnetic needles." Thesis, Karlstads universitet, Avdelningen för kemiteknik, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:kau:diva-36540.
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The main objective in this work was to learn how the instrument, the Interfacial Shear Rheometer (ISR400), worked and to investigate how the rheological properties, storage modulus (elasticity), G' and loss modulus (viscous), G'', changes when the surface pressure at the air-liquid interphase changes. The second objective were to examine the different kind of magnetic needles used in the experiments and to conclude which type of needle is best for its specific field of analysis. It was concluded that the relative heavy needle with mass 70.6 mg and length 50 mm was best for systems where the viscous and elastic components are significantly large, where the inertia of the needle is not dominant. It also worked of using the heavier needle for a system of phospholipids. For the hydroxystearic acid (HSA) experiment that were tested on NaCl sub-phase there was a clear improvement after switching from the heavy needle (mass 41.5 mg; length 51 mm) to the relative lighter needle (mass 6.94 mg; length 34.7 mm). The values for the dynamic modulus therefore had a better agreement with reference literature. A spread layer of class II hydrophobins (HFBII) could be compressed to a surface pressure of 46 mNm-1. The G' and G'' values from the frequency sweep were discarded because the monolayer turned into a very viscous-like liquid, and the oscillating needle, after compression, was kind of stuck in the sub-phase and moved very staggering during a frequency sweep. The needle comparison experiment with silica particles 10 wt% Bindzil CC30 (BCC30), at pH 3.5 was done to see if there was any difference in the sensitivity for the needles at the interface which consisted of a pure 10 mM NaCl solution or a 10 mM NaCl solution with BCC30 added to it. The differences were negligible in terms of surface tension but there was a clear difference between the heavy needle and the light needle, when oscillating at higher frequencies (>≈6 rad/s). With this study, the understanding of ISR400 has increased largely. Several issues have been addressed and the results provide a good basis for further studies within the many areas the instrument can be used for. Despite the project's time limit, and the fact that the instrument was new and untested where the project was carried out, focus areas were prioritized so good results could be achieved within reasonable goals.Huvudmålet med detta arbete var att lära sig hur instrumentet ytskiktsreometern (ISR400) fungerade och undersöka hur de reologiska egenskaperna, elasticitetsmodulen G' och viskositetsmodulen G'', kommer att förändras när det sker en förändring för yttrycket vid gränsskiktet mellan luft och vätska. Det sekundära målet var att undersöka vilken typ av magnetiska nålar som är bäst att använda för respektive gränsskiktssystem. Av att använda den tyngre nålen med massan 70.6 mg och längden 50 mm kunde man dra slutsatsen att den är bäst att använda för system där de viskösa och elastiska komponenterna är signifikant stora, där nålens tröghet inte är dominant. Den fungerade även att mäta med i ett fosfolipidsystem. I experimentet med 12-hydroxy-stearinsyra (HSA) som utfördes på en subfas av NaCl, syntes en klar förbättring efter att byta från en tyngre nål (massa 41.5 mg; längd 51 mm) till en lättare (massa 6.94 mg; längd 34.7 mm). Värdena för dynamiska modulen stämde därför bättre överens med referenslitteraturen. Det utspridda lagret av klass II hydrophobins (HFBII) kunde komprimeras upp till yttrycket 46 mNm-1. Värdena för G' och G'' förkastades därför att monolagret förvandlades till en väldigt viskösliknande vätska, och den oscillerande nålen, efter kompressionen, satt fast i denna tröga vätska och rörde sig väldigt hackigt och oregelbundet under tiden ett frekvenssvep utfördes. Då en jämförelse av olika typer av nålar genomfördes med kiseldioxidpartiklar (10 % (viktsprocent) Bindzil CC30 med pH 3.5), för att se om det är någon skillnad i känslighet för nålarna vid gränssnittet, som bestod av en ren 10 mM NaCl-lösning eller en 10 mM NaCl-lösning med tillsatt BCC30. Skillnaderna var försumbara gällande ytspänningen, men det var en klar skillnad mellan den tunga nålen och den lätta nålen vid oscillering vid höga frekvenser (>≈6 rad/s). I och med detta arbete så har förståelsen för hur ISR400 fungerar förbättrats mycket sedan starten. Flera frågeställningar har behandlats och resultaten ger en bra grund för fortsatta studier inom de många områden som utrustningen kan användas till. Trots projektets tidsbegränsning, och det faktum att instrumentet var nytt och oprövat på platsen där detta arbete utfördes, så prioriterades fokusområden så att goda resultat kunde uppnås inom rimliga mål.
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Gholami, Mohammad. "Shear Induced Migration of Particles in a Yield Stress Fluid." Ohio University / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1502793185991791.
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Benhadia, Abrehem M. A. "Evaluation of the critical parameters and polymeric coat performance in compressed multiparticulate systems." Thesis, University of Bradford, 2019. http://hdl.handle.net/10454/17459.
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Compression of coated pellets is a practical alternative to capsule filling. The
current practice is to add cushioning agents to minimize the stress on the
coated pellets. Cushioning agents however add bulkiness and reduce the
overall drug loading capacity. In this study, we investigated the performance
of compressed coated pellets with no cushioning agent to evaluate the
feasibility of predicting the coat behaviour using thermo-mechanical and
rheological analysis techniques. Different coating formulations were made of
ethyl cellulose (EC) as a coating polymer and two different kinds of additives
were incorporated into the polymeric coating solution. Triethyl Citrate (TEC)
and Polyethylene glycol 400(PEG400) were used as plasticizers at different
levels to the coating formulations (10%, 20%, 30%). Thermal, mechanical
and rheological measurements of the coating film formulations were
achieved to investigate the effect of plasticizers. Thermal gravimetric
analysis results (TGA) showed higher residual moisture content in films
plasticised with PEG 400 compared to their TEC counterparts. Differential
Scanning Calorimetry (DSC), Dynamic Mechanical Analysis (DMA) and
Parallel Plate Shear Rheometer (PPSR) were used to study the influence of
the level and type of plasticisers incorporated in coating film formulation on
the performance of the coating film. In this study, both DSC and DMA were used to investigate the Tg for each film coating formulation in order to
evaluate the effect of the additives. In general DMA results for the Tg value
of the films were always higher by 10-20% than those measured by the DSC.
Furthermore, clamp size and the frequency of the oscillation have an
influence on the evaluation of Tg. Complex viscosity for different coating film
formulations revealed that the shear hinning gradient changes with
temperature and plasticiser type and concentration. The value of complex
viscosity from DMA and PPSR exhibits power law behaviour. The rheological
moduli were indirectly affected by the level of plasticiser. There was a
discrepancy between the complex viscosity results obtained from both DMA
and PPSR at similar temperature but they follow the same trend. The non
plasticized polymer showed a 10 time higher complex viscosity values when
measured by DMA over that measured by PPSR. The difference was smaller
in plasticized films but it was not consistent. Therefore a consistent
coefficient to correlate the DMA and PPSR couldn’t be accurately determined
Coated pellets were compressed and key process parameters were
evaluated. The obtained results revealed that the coating thickness has a
significant effect on the release profile of the final products. It was found that
by increasing the coating film thickness, the percentage released decreased.
Also the compression force has lower influence on the drug release profile,
while the dwell time has very low effect on the percentage release from the
final products. Optimum release profile was obtained at a coating level of 5.5%
w/w and a compression force of 4700N
In conclusion, the elasticity of the plasticised EC films in this study meant
that the internal stress is not dissipated during compression and the dwell time range that was used in this experiment. Increasing the thickness
therefore was necessary to enhance the strength of the film and avoid
cracking. The mechanical and rheological profiling was helpful therefore to
understand the behaviour of the coated pellets and predict the film properties
at various steps of the process of coating and compression (i.e., various
shear rate regimes). Experimental design approach to studying the key
process and formulation parameters helped identify the optimum values for
the process.
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Isreb, Mohammad. "Thermal and rheological approaches for the systematic enhancement of pharmaceutical polymeric coating formulations : effects of additives on glass transition temperature, dynamic mechanical properties and coating performance in aqueous and solvent-free coating process using DSC, shear rheometry, dissolution, light profilometry and dynamic mechanical analysis." Thesis, University of Bradford, 2011. http://hdl.handle.net/10454/5527.
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Additives, incorporated in film coating formulations, and their process parameters are generally selected using a trial-and-error approach. However, coating problems and defects, especially those associated with aqueous coating systems, indicate the necessity of embracing a quality-by-design approach to identify the optimum coating parameters. In this study, the feasibility of using thermal and rheological measurements to help evaluate and design novel coating formulations has been investigated. Hydroxypropyl methylcellulose acetate succinate (HPMCAS), an enteric coating polymer, was used as the film forming polymer. Differential Scanning Calorimetry (DSC), Dynamic Mechanical Analysis (DMA), and Parallel Plate Shear Rheometery (PPSR) were used to evaluate the effect of different plasticisers on the performance of HPMCAS. The results illustrate that, for identical formulations, the DSC and DMA methods yielded up to 40% differences in glass transition temperature (Tg) values. Moreover, Tg measured using loss modulus signals were always 20-30 oC less than those measured using tan delta results in DMA testing. Absolute and relative Tg values can significantly vary depending on the geometry of the samples, clamp size, temperature ramping rate and the frequency of the oscillations. Complex viscosity data for different formulations demonstrated a variable shear thinning behaviour and a Tg independent ranking. It is, therefore, insufficient to rely purely on Tg values to determine the relative performance of additives. In addition, complex viscosity results, obtained using both the DMA and PPSR techniques at similar temperatures, are shown to be comparable. The results from both techniques were therefore used to produce continuous master curves for the HPMCAS formulations. Additionally, step strain tests showed that HPMCAS chains do not fully III disentangle after 105 seconds as predicted by the Maxwell model. Finally, in situ aqueous-based coating experiments proved that mixtures of triethyl acetyl citrate and acetylated monoglyceride (TEAC/AMG), even without cooling of the suspension, do not cause blocking of the spray nozzle whereas triethyl citrate (TEC) based formulae did. TEAC (alone or in a combination with AMG) exhibits superior wettability to HPMCAS than TEC/AMG formulations and can be used to enhance the efficiency and film quality of the dry coating process.
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Rahman, Mashuqur. "Rheology of cement grout : Ultrasound based in-line measurement technique and grouting design parameters." Doctoral thesis, KTH, Jord- och bergmekanik, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-176885.
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Grouting is performed in order to decrease the permeability and increase the stiffness of the material, especially soil and rock. For tunnelling and underground constructions, permeation grouting is done where cement based materials are pumped inside drilled boreholes under a constant pressure, higher than the ground water pressure. The aim of permeation grouting is to reduce the water flow into tunnels and caverns and to limit the lowering of the surrounding groundwater table. Cement based materials are commonly used as grout due to their availability and lower costs. To obtain a proper water sealing and reduce the lowering of the ground water table, a desired spread of grout must be achieved and the rheology of the cement grout is the governing factor for estimating the required spread. Rheological properties of cement grout such as viscosity and yield stress are commonly measured off-line using laboratory instruments, and some simple tools are available to make field measurements. Although the rheological properties of the grout that is used play a fundamental role in design and execution, no method has yet been developed to measure these properties in-line in field work. In addition to the real time measurement, there is no standard method for determining the yield stress for grouting applications. Despite the common usage of Bingham model fitting to determine the yield stress, the range of shear rate is often not specified or is neglected. In this work, an in-line rheometry method combining the Ultrasound Velocity Profiling (UVP) technique with Pressure Difference (PD) measurements, known as “UVP+PD”, was successfully tested for continuous in-line measurements of concentrated micro cement based grouts. A major obstacle of using the ultrasound based methodology was the transducers, which would be capable of emitting sufficient acoustic energy and can be used in field conditions. The transducer technology was developed in a parallel project and the Flow-Viz industrial rheometer was found to be capable of detail measurement of the velocity profiles of cement grout. The shape of the velocity profiles was visualized, and the change in the shape of the profiles with concentration and time was observed. The viscosity and yield stress of the grout were determined using rheological models, e.g. Bingham and Herschel-Bulkley. In addition, rheological properties were determined using the non-model approach (gradient method) and the tube viscometry concept and were compared with results obtained using the rheological models. The UVP+PD method was found to be capable of determining the rheological behavior of cement grout regardless of the rheological model. The yield stress of cement grout was investigated using off-line rheometry techniques and UVP+PD in-line measurements. Tests were performed applying different shear histories and it was found that two ranges of yield stress indeed exist. Therefore, the design value of yield stress should be chosen with respect to the prevailing shear rate at the grout front for the required spread of grout. In addition, an appropriate shear rate range should be used when a Bingham fitting is done to determine the yield stress. In order to estimate the shear rate, plug thickness and velocity for one dimensional and two dimensional geometry, a non- dimensional nomogram was developed. The advantage of using the nomogram is that it does not depend on the applied pressure and the rheological properties of the grout and can therefore, be used as a simple design tool. Analytical approaches were used for the estimation and good agreements were found with numerical calculations and experimental results. In conclusion, in this work, it was found that it is possible to continuously measure the velocity profiles and determine the change of the rheological properties of cement grout using the ultrasound based UVP+PD method under field conditions. The yield stress was also investigated and it was found that two range of yield stress exist depending on the prevailing shear rate of the grout, which should be used for designing the grouting time at different conditions. In order to decide the design value of yield stress for grouting applications, a non-dimensional nomogram was developed that can be used to estimate the plug thickness, shear rate and velocity of the grout.Funding for the project was provided by the Swedish Rock Engineering Research Foundation (BeFo), The Swedish Research Council (FORMAS) and The Development Fund of the Swedish Construction Industry (SBUF), who are gratefully acknowledged. QC 20151112
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Pértile, Patricia. "Propriedades mecânicas em micro e mesoescala de solos do Rio Grande do Sul." Universidade Federal de Santa Maria, 2015. http://repositorio.ufsm.br/handle/1/3368.
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Coordenação de Aperfeiçoamento de Pessoal de Nível SuperiorSusceptibility to soil degradation is a function of disturbance intensity and structure resistance, which is usually described by mesoscale properties. However, soil mechanical strength in the microscale (micromechanical) evaluated by rheology is not well known. The objective was to evaluate the micromechanical resistance of soils of Rio Grande do Sul through amplitude sweep tests under oscillatory shear, to know the variables that influence this resistance and to evaluate its relationship with physical and mechanical properties in mesoscale. Surface and subsurface horizons of eight soils, Oxisol (4), Ultisol (2), Alfisol (1) and Vertisol (1), were characterized for particle size, mineralogy, chemical, physical and mechanical in micro and mesoscale. The micromechanical resistance of soils was evaluated by rheological curves and parameters, and the influence of water content on rheological parameters was evaluated by regression analysis. The influence of soil composition on rheological parameters and the relationship between rheological parameters and physical and mechanical properties were evaluated by correlation analysis and principal component analysis. There was great variation between soils and horizons according its constitution of particle size, mineralogy and chemistry, where sand, clay, total carbon and presence of 2:1 clay minerals were the most influential factors on rheological behavior of the soils. Soil matric potential also had a strong influence on micromechanics resistance of soils. There were correlations of rheological parameters with physical properties (bulk density and soil porosity), but few correlations with mesomechanical properties (uniaxial compressibility and direct shear). The higher silt and clay content increased the microstructural resistance of the soil, where higher sand content decreased this resistance. The predominance of smectite in clay fraction increased the microstructural elasticity; the increased of kaolinite decreased the elasticity and the increased of iron oxides raised the microstructural stiffness (shear stress) of the soils. Increased water pressure increased micromechanical resistance of most soils due to meniscus force, occurring reduction in micromechanics stiffness at 10 kPa pressure due to presence of pseudosand associated with low bulk density. The increase of carbon content increased soil elasticity, but decreased soil rigidity; and cations content correlated only indirectly with rheological parameters. The larger correlation between rheological parameters and physical properties is probably due to aggregation factors being the same in both scales, such as particle size, mineralogy and their interactions. On the other hand, the low relation of soil mechanical resistance in micro and mesoscale seem influenced by different factors related to soil composition and structure.
A suscetibilidade do solo à degradação é função da intensidade da perturbação e da resistência da estrutura, a qual é normalmente descrita por propriedades em mesoescala. Entretanto, a resistência mecânica do solo em microescala (micromecânica) avaliada por meio da reologia é pouco conhecida. O objetivo foi avaliar a resistência micromecânica de solos do Rio Grande do Sul com o uso de testes de varredura de amplitude por cisalhamento oscilatório, conhecer as variáveis que influenciam essa resistência e avaliar sua relação com propriedades físicas e mecânicas em mesoescala. Os horizontes superficial e subsuperficial de oito solos das ordens Latossolo (4), Argissolo (2), Planossolo (1) e Vertissolo (1) foram caracterizados quanto à granulometria, mineralogia, propriedades químicas, físicas e mecânicas em micro e mesoescala. A resistência micromecânica dos solos foi avaliada por curvas e parâmetros reológicos e a influência do conteúdo de água sobre parâmetros reológicos foi avaliada por análise de regressão. A influência da composição do solo nos parâmetros reológicos e a relação entre parâmetros reológicos e propriedades físicas e mesomecânicas foram avaliadas por análise de correlação e análise de componentes principais. Houve grande variação entre os solos e horizontes quanto à sua constituição granulométrica, mineralógica e química, sendo areia, argila, carbono e presença de argilominerais 2:1 os fatores que mais influenciaram o comportamento reológico dos solos. A tensão de água também teve forte influência na resistência micromecânica dos solos. Foram verificadas correlações de parâmetros reológicos com propriedades físicas (densidade e porosidade do solo), mas poucas correlações com propriedades mesomecânicas (compressibilidade uniaxial e cisalhamento direto). O aumento dos teores de silte e argila aumentou a resistência micromecânica do solo, enquanto maiores teores de areia diminuíram essa resistência. O predomínio de esmectita na fração argila aumentou a elasticidade microestrutural; a caulinita diminuiu a elasticidade; e o aumento de óxidos de ferro aumentou a rigidez (tensão de cisalhamento) microestrutural dos solos. O aumento da drenagem aumentou a resistência micromecânica da maioria dos solos devido ao aumento das forças de meniscos, ocorrendo redução da rigidez micromecânica na tensão de água de 10 kPa em horizontes com presença de pseudoareia associada com baixa densidade do solo. O incremento dos teores de carbono aumentou a elasticidade do solo, mas diminuiu sua rigidez; e os teores de cátions correlacionaram-se indiretamente com parâmetros reológicos. A maior relação entre parâmetros reológicos e propriedades físicas decorre, provavelmente, dos fatores de agregação serem os mesmos em ambas as escalas, como a granulometria, a mineralogia e suas interações. Por outro lado, a relação da resistência mecânica do solo em micro e mesoescala foi pequena, pois parecem influenciadas por diferentes fatores relacionados à composição e estrutura do solo.
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Giacomin, A. Jeffrey. "A sliding plate melt rheometer incorporating a shear stress transducer /." Thesis, McGill University, 1987. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=76525.
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In currently used shear rheometers, shear stress is inferred from a measurement of either total force or total torque. These methods are subject to experimental errors due to uncontrolled flow at the sample boundaries. Such errors can be avoided by measuring the shear stress locally, in the region of controllable flow, using a shear stress transducer. A new sliding plate rheometer for molten plastics has been developed to incorporate a recently developed shear stress transducer. The rheometer operates at temperatures up to 250$ sp circ$C. Static and dynamic calibrations showed that the shear stress transducer sensitivity is stable and that its frequency response is suitable for the study of molten plastics. This rheometer was equipped with a computer controlled servohydraulic linear actuator, which provided wide flexibility in shear history selection. Digital data acquisition and signal processing enabled the use of the discrete Fourier transform for nonlinear viscoelastic property determination. Important differences were observed between the locally measured shear stress and values inferred from total force in both large amplitude oscillatory shear and in reciprocating exponential shear tests. For these property measurements, free boundary errors can dominate the dynamics of total force measurements.
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Walker, Alasdair Michael. "Extrusion processing of chocolate crumb paste." Thesis, University of Oxford, 2012. http://ora.ox.ac.uk/objects/uuid:1c54a2e6-a767-4fd3-8bf0-e2d250b7ac4a.
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This project considers the co-rotating twin screw extrusion of a confectionery paste comprising powdered proteins, sugars, water and fats. As is the case with many food industry products, this process has been developed experimentally with little quantitative understanding of how variations in processing conditions influence the formation of the extrudate. A variety of techniques have therefore been developed to characterise and quantify the dispersive mixing, distributive mixing and rheological flow properties of this complex, multiphase, viscoelastic, unstable material. These techniques have then been utilised in a pilot plant extruder study of the mechanics of mixing and paste formation during extrusion, considering the influence of both processing conditions and screw profile. The internal evolution of paste microstructure has been successfully tracked along the length of screw profile using dead-stop extractions of the screws. A rigorous off-line assessment of shear yield strength behaviour using cone penetrometry has shown the use of conventional off-line rheometers to be unviable due to rapid post extrusion hardening. This highlighted the need for an in-line rheological measurement technique for continuous extrusion analysis where the extruded material is severely time dependent and not extractable. In pursuit of this, a novel arrangement of bender elements is proposed and trialled, to rapidly characterise material parameters of viscoelastic pastes. A second technique looking to extend the application of shear wave interface reflection to multiphase pastes is also trialled. A novel analysis of thermogravimetric data (TGA) has generated a viable index of distributive mixing, suitable for use on complex multi-component materials where thermal decomposition temperatures of the components are not well defined. Quantitative image analysis of pastes using scanning electron microscopy (SEM), optical microscopy protein staining and a novel application of multiphoton microscopy (MPM) have been used to visualise paste microstructure and quantify dispersive mixing. From the pilot plant extruder study, the application of these techniques was successful in mapping the evolution of paste mixing and the resulting microstructure, as well as identifying key differences between pastes mixed by twin screw extrusion and batch mixing.
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Bommavaram, Ramamohan Reddy. "Evaluation of healing in asphalt binders using dynamic shear rheometer and molecular modeling techniques." [College Station, Tex. : Texas A&M University, 2008. http://hdl.handle.net/1969.1/ETD-TAMU-2919.
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Martelli, Luca. "Studio delle proprietà reologiche di leganti bituminosi modificati ad "alta lavorabilità" mediante Dynamic Shear Rheometer." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2011. http://amslaurea.unibo.it/2009/.
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Agarwal, Neeraj. "Transient Shear Flow Rheology of Concentrated Long Glass Fiber Suspensions in a Sliding Plate Rheometer." Thesis, Virginia Tech, 2009. http://hdl.handle.net/10919/34784.
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Transient viscosity growth measurements at the startup of shear flow were performed on long glass fiber-filled polypropylene. Samples were prepared with fibers pre-oriented either in 1-direction, 3-direction or random in 1-3 plane, where the 1-direction is the direction of shear motion, the 2-direction is perpendicular to the shear plane and the 3-direction is the neutral direction. A sliding plate rheometer incorporating a shear stress transducer was constructed in the lab. It was shown that this device works well for the tested materials including a Newtonian oil, a low density polyethylene (LDPE) and short glass fiber-filled polypropylene. The transient viscosity growth behavior for long glass fiber suspensions was subsequently investigated. The results suggested that both, fiber length and fiber concentration have pronounced effect on the steady state suspension viscosity. It was also observed that the transient behavior of the pre-oriented samples was highly dependent on the initial orientation state of the fibers.Master of Science
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Dakhil, Haider [Verfasser], and Andreas [Akademischer Betreuer] Wierschem. "A narrow-gap rotational rheometer for high shear rates and biorheological studies / Haider Dakhil. Gutachter: Andreas Wierschem." Erlangen : Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU), 2016. http://d-nb.info/1085634256/34.
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Li, Ming. "Study of the FT4 powder rheometer : comparison of the test methods and optimization of the protocols." Thesis, Compiègne, 2017. http://www.theses.fr/2017COMP2327/document.
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Ce travail a pour objectifs d’évaluer le potentiel d'une technique spécifique de caractérisation des propriétés d'écoulement des poudres : le rhéomètre à poudre FT4. L'objectif est de pouvoir mettre en place une analyse complète sur les avantages, les inconvénients et les limites d'utilisation des tests, l'impact de la cohésion des poudres et la répétabilité des mesures. Tout d'abord, des efforts sont faits pour explorer les différences entre la consolidation test de FT4 et le tap-tap. Les résultats indiquent que la consolidation test de FT4 a une bonne répétabilité, mais il peut sous-estimer la compressibilité des poudres. Cette méthode peut être optimisée en améliorant sa procédure d'initialisation pour donner des résultats cohérents en tant que le tap-tap. Deuxièmement, le cisaillement test de FT4 est comparé avec Schulze Ring Shear Tester et Evolution Powder Tester. Cette comparaison indique que le cisaillement test de FT4 peut sous-estimer la cohésion des poudres. Par conséquent, les dimensions des accessoires doivent être optimisées. Enfin, une nouvelle technique de caractérisation a été mise au point. Dans cette méthode, les poudres présentent des mouvements périodiques et la période correspondant peut être liée aux propriétés d'écoulement des poudres. Cette méthode a une très bonne capacité à identifier et à catégorier les propriétés d'écoulement de la poudre dans les conditions de faible contrainteThis research has been dedicated to evaluate the reliability of the FT4 and to improve the current tests for a better and convenient powder characterization. Firstly, efforts are made to explore the differences between the compaction test provided by the FT4 and the traditional tapped density measurement. Results indicate that the FT4 compaction test has good repetability but it may underestimate powder compressibility. This method can be optimized by improving its initialization procedure to give consistent results as the tapped density measurement. Secondly, the shear tests provided by the FT4 are evaluated by comparing with the methodologies provided by Schulze Ring Shear Tester and Evolution Powder Tester. This comparison indicates that the FT4 shear cell test may underestimate powder strength, especially when a cohesive powder sample is measured, which may cause blockage when using the FT4 method to design a silo. To overcome this shortage, the dimensions of the shear accessories should be optimized. Most importantly, a new characterization technique has been developed. ln this method, powder materials present periodic motions and the cycle time of the periodic flow can be linked to the powder flow properties. This method has very good capability to identify and classify powder flow properties under low stress conditions
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Bhatia, Rupesh. "Effect of molecular mass, concentration and temperature on the rheological properties of non-newtonian aqueous polymeric solutions." University of Cincinnati / OhioLINK, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1313765879.
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Orlandi, Giulia. "Caratterizzazione reologica avanzata di bitumi estesi con materiali di riciclo per lo sviluppo di conglomerati bituminosi innovativi." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2019.
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Lo scopo di questa tesi è studiare leganti eco-sostenibili per pavimentazioni stradali ottenute mediante l’uso di polverino di gomma da Pneumatici Fuori Uso (PFU) ed il residuo della raffinazione di oli motore esausti (Re-refined Engine Oil Bottom, REOB). In questo modo si cerca di approfondire le attuali conoscenze scientifiche sull'uso dei materiali di riciclo come agenti modificanti del risultante legante bituminoso al fine di ridurre l'uso del bitume di origine petrolifera, testando il legante ed i conglomerati bituminosi dal punto di vista meccanico e reologico.
Al fine di stimare le prestazioni di questi nuovi materiali "green" per la costruzione di strade, sono stati eseguiti test sperimentali di laboratorio. In dettaglio, i test reologici su estensioni e leganti bituminosi vengono eseguiti con il Dynamic Shear Rheometer (DSR), determinando il modulo di rigidezza mediante la prova Indirect Tensile Stiffness Modulus (ITSM), la resistenza a trazione indiretta con il Indirect Tensile Strength (ITS) e la sensibilità all’acqua determinando il rapporto Indirect Tensile Strength Ratio (ITSR). L'interpretazione dei risultati mostra la possibilità di modificare il bitume con materiali di scarto, ottenendo prestazioni pari a quelle dei conglomerati bituminosi tradizionali e riducendo in questo modo l'uso di bitume, dando una "seconda vita" a questi materiali di scarto.
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Uccellatori, Martina. "Modelli particellari per lo studio delle miscele bituminose." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2013. http://amslaurea.unibo.it/5423/.
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Mazzotta, Francesco. "Studio reologico avanzato di bitumi modificati ed additivati:proposta di una nuova procedura di aging." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2012. http://amslaurea.unibo.it/4257/.
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Le problematiche ambientali e socio – economiche legate alla costruzione di nuove infrastrutture viarie, impongono la progettazione e costruzione di strade che combinino ad elevati standard prestazionali, la riduzione dell’impatto ambientale in fase realizzativa e manutentiva. Quanto detto avvalora il crescente utilizzo di materiali bituminosi modificati con polimeri ed additivati con cere. I primi conferiscono alla miscela maggiore elastoplasticità, incrementandone la durabilità e la resistenza a fatica. Nei secondi la presenza del materiale paraffinico contribuisce a ridurre la viscosità del bitume, il che consente il notevole abbassamento della temperatura di produzione e stesa della miscela. Numerosi studi inoltre hanno dimostrato che le caratteristiche meccaniche della pavimentazione sono fortemente influenzate dal grado di ossidazione delle componenti organiche del bitume, ovvero dal fenomeno dell’invecchiamento o aging. Risulta pertanto fondamentale affiancare allo studio reologico del bitume, prove di simulazione dell’ invecchiamento nel breve e lungo termine. Nel corso della seguente ricerca si provvederà pertanto ad analizzare leganti modificati ed additivati secondo la teoria della viscoelasticità, simulando le reali condizioni di carico ed invecchiamento alle quali il bitume è sottoposto. Tutte le prove di caratterizzazione reologica avanzata prevederanno l’utilizzo del DSR (Dynamic Shear Rheometer) in varie configurazioni di prova e si simulerà l’invecchiamento a breve termine mediante RTFOT (Rolling thin film oven test). Si proporrà inoltre una nuova procedura di aging invecchiando il bitume alla temperatura di equiviscosità o Twork , ovvero a quel valore della temperatura tale per cui, in fase di messa in opera, si avrà una distribuzione molecolare omogenea del modificante all’interno del bitume. Verranno quindi effettuate ulteriori prove reologiche sui leganti invecchiati a tale temperatura. Si darà infine supporto ai risultati della ricerca effettuando prove chimiche con la tecnica analitica FTIR (Fourier Transform Infrared Spectroscopy), analizzando i cambiamenti molecolari avvenuti nel bitume a seguito dell’aggiunta del modificante e dell’invecchiamento.
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Calamelli, Filippo. "Studio reologico di mastici per miscele di conglomerato bituminoso drenante contenente polverino di gomma da pfu." Bachelor's thesis, Alma Mater Studiorum - Università di Bologna, 2016.
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Le prestazioni meccaniche di una miscela di conglomerato bituminoso dipendono principalmente dai materiali che la compongono e dalla loro interazione. La risposta tenso-deformativa delle sovrastrutture stradali è strettamente legata al comportamento reologico del legante bituminoso e dalla sua interazione con lo scheletro litico. In particolare nelle pavimentazioni drenanti, a causa dell’elevato contenuto di vuoti, il legame che si crea tra il legante (mastice bituminoso) e l’aggregato è molto forte, per questo motivo è importante migliorarne le prestazioni. Additivando il mastice con polverino di gomma da PFU (pneumatici fuori uso), non solo si migliorano prestazioni, resistenza alle deformazioni permanenti ed elastoplasticità del materiale, ma si sfruttano anche materiali di recupero, portando vantaggi anche dal punto di vista ambientale.
In quest’ottica la ricerca effettuata nella tesi si pone come obiettivo l’analisi reologica e lo studio di mastici additivati con polverino di gomma ricavato da PFU, per la realizzazione di conglomerati bituminosi drenanti. In particolare, partendo da un bitume di base, sono stati preparati due mastici: il primo ottenuto miscelando bitume modificato e filler calcareo, il secondo aggiungendo al precedente anche il polverino di gomma. Tale studio è stato eseguito mediante l’utilizzo del DSR (Dynamic Shear Rheometer – UNI EN 14770), con il quale sono state affrontate tre prove:
Amplitude Sweep test, per la valutazione del valore di deformazione di taglio γ entro il quale il materiale si mantiene all’interno del campo di viscoelasticità lineare (Linear visco-elasticity, LVE);
Frequency Sweep test, per l’estrapolazione delle master curves;
Multiple stress Creep Recovery, per valutare la resistenza del materiale alle deformazioni permanenti. Dall’analisi dei dati è stato possibile definire il comportamento reologico di entrambi i mastici e, in seconda analisi, confrontarne le caratteristiche e le prestazioni.
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Pedholla, Prashanth Kumar. "Rheological and mechanical analysis of bituminous mixtures modified with recycled crumb rubber by wet technology." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2017.
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Road construction and maintenance is not only expensive, but it also has a huge impact on the environment. Being context sensitive in finding the material for the asphalt pavement with a superior quality have been always a challenge. The use of recycled material might be a good solution for reducing the overall impact of the road infrastructures.
This report studied the effect of using crumb rubber in the asphalt mixture. The research was based on a practical experience of using crumb rubber modified mixture in Zola Predosa, Bologna (Italy). The mixtures were also having limestone filler as a modifier. Mastic(Binder-modifier system) and mortar (mastic-fine aggregate system) mixture having different quantities of crumb rubber and limestone filler modifiers have been tested in order to find the best rutting resistance combination with an acceptable stiffness. The rheological tests on bituminous mastics and mortars have done in the laboratories of University of Bologna.
The results show that using fine crumb rubber reduces the thermo sensibility of the mastic (Binder Bitumen System) and improves its elasticity. Limestone filler in the other hand increases the mixture stiffness at high Frequencies.
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Dostál, Filip. "Vliv druhu a dávky polymeru na vlastnosti modifikovaných pojiv." Master's thesis, Vysoké učení technické v Brně. Fakulta stavební, 2020. http://www.nusl.cz/ntk/nusl-409806.
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The diploma thesis is focused on polymer modified binders with different polymer doses. The theoretical part describes the history of the use of bitumen, the extraction of bitumen from oil and behavious of the polymer type SBS/SB, which is used in the diploma thesis on modified binders. Further, the theoretical part describes the empirical and functional tests of bitumen binders. In the practical part the results of indidual tests are presented and compared with the standard ČSN 65 7222-1. At the end of the diploma thesis are summarized results of work and evaluation of binders with the best achieved properties.
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Bernardoni, Fausto. "Caratterizzazione delle proprietà reologiche dei bitumi tiepidi fluidificati ed identificazione di una procedura ottimale di invecchiamento." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2011. http://amslaurea.unibo.it/2857/.
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Rigal, Claire. "Comportement de fluides complexes sous écoulement : approche expérimentale par résonance magnétique nucléaire et techniques optiques et simulations numériques." Thesis, Université de Lorraine, 2012. http://www.theses.fr/2012LORR0091/document.
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Cette thèse est une contribution à la fois expérimentale, théorique et numérique à l'étude des écoulements bidimensionnels de fluides complexes dans une conduite cylindrique présentant des singularités et dans une géométrie annulaire à cylindres excentrés. Le fluide utilisé est une solution de xanthane à différentes concentrations présentant un caractère non newtonien rhéofluidifiant. L'objectif principal de cette thèse est la caractérisation de l'influence des propriétés rhéofluidifiantes sur le comportement des zones de recirculation, en terme de morphologie, de positionnement et d'intensité, par l'utilisation et le développement de techniques de mesures non intrusives et performantes. La première méthode expérimentale utilisée une technique laser classique: la vélocimétrie par images de particules. La seconde technique mise en oeuvre est une méthode originale: la vélocimétrie par imagerie par résonance magnétique. Elle est utilisée pour la première fois au laboratoire pour la mesure de champ de vitesse d'écoulement de fluides complexes en conduite cylindrique, représentant l'intérêt majeur de cette thèse. La première partie de notre travail consiste en une description rhéologique complète de nos fluides modèles avec la détermination de leur loi de comportement et la mise en évidence de leurs propriétés viscoélastiques, par ailleurs négligeables. Par la suite les mesures de champ de vitesse des écoulements bidimensionnels étudiés et la représentation des lignes de courant montrent que les propriétés rhéofluidifiantes influencent très fortement la structure et la morphologie de ces écoulements et le comportement des zones de recirculation. Par une étude fine nous observons qu'il existe une compétition entre les effets d'inertie et les effets rhéofluidifiants induisant un champ de contrainte variable qui modifie le positionnement et la taille de la zone de recirculation. Nous montrons également que l'augmentation du caractère rhéofluidifiant affaiblit son intensité de la zone de recirculation. Enfin, des simulations numériques utilisant la loi de comportement macroscopique déterminée par rhéométrie classique ont été réalisées avec le logiciel Fluent. Une bonne concordance est observée entre les résultats de ces simulations numériques et les expérimentaux. Cette comparaison permet ainsi de valider le code de calcul et la loi de comportement, utilisée pour les simulations numériques au travers de sa modélisation suivant la loi de Cross, pour les écoulements considérésThis thesis is an experimental and numerical study of structured fluids bidimensional flows in a cylindrical pipe with singularity and in an annular geometry with eccentric cylinders. The objective of this thesis is to characterize the influence of the shear thinning properties on the recirculation zones by using efficient and non-intrusive techniques: particle image velocimetry and velocimetry by nuclear magnetic resonance imaging. Materials are xanthane solutions at different concentrations. In the first part, we determine the rheological and viscoelastic properties of the fluids used. The second part concerns the measured velocity field. It is shown that the shear thinning behavior have a strongly influence on the structure and the morphology of these flows and the pattern of the recirculation zones. Simultaneously, numerical simulations performed by Fluent and using the rheological behavior. A good concordance is observed between the experimental and numerical results. For the flows considered here, this comparison allows to validate the computational code and the behavior law used in the numerical simulations and modelling by a Cross model
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Železník, Tomáš. "Slit-flow reometr pro magnetické i nemagnetické kapaliny." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2020. http://www.nusl.cz/ntk/nusl-417518.
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In this thesis was designed, manufactured and tested the fourth evolution of a slit-flow rheometer with another necessary parts, eg. rheometer`s holder, drive frame and important jig tools. The rheometer is able to measure rheological properties of magnetic and non-magnetic fluids at very high shear rates, which commercial rheometers can not reach. It is designed for 200 bar pressure and maximum load 15 kN. The construction of the slit-flow rheometer with it`s holder and drive frame improves user friendliness, accelerates change of the fluid sample and expands research opportunities thanks to a big space for additional adjustments. It is possible to use different length of the slit and thanks to a changeable inserts it is possible to change parameters of the slit (roughness of the walls, wall material, thickness of the slit). A part of this thesis was focused on illation of necessary equations for planning calibration measurements. Aim of these measurements is to obtain minor pressure losses dependence on Reynolds number for specific slit.
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Ali, Mahdi. "Study of the bitumen aging effects on the rheological properties and fatigue behavior." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2018. http://amslaurea.unibo.it/16255/.
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A study of bitumen aging effects on the rheological properties and fatigue behavior is carried out on five polymer modified bitumen provided by an oil company. Dynamic Shear Rheometer (DSR), is used to perform advanced experimental investigation. It allows practicing frequency sweep tests, fatigue tests and time sweep tests. Polymer modified bitumen with different percentage of SBS with or without the presence of crumb rubber are tested before and after short and long aging processes.
Master curves were generated based on frequency sweep tests data, they are studied, and a comparison was conducted between each bitumen before and after aging. In this thesis, the DSR is presented, as well as the testing procedure and the tested materials. A fatigue life analysis of the results, based on the use of two different criteria, the first criterion is classically used: it consists in defining the failure as a 50% loss of the initial stiffness. The other criteria based on dissipated energy data.
This thesis provides results which show the effects of several factors on fatigue and healing response such as bitumen type, ageing, the presence of rubber and polymer modification.
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Střasáková, Monika. "Stárnutí asfaltových pojiv." Master's thesis, Vysoké učení technické v Brně. Fakulta stavební, 2016. http://www.nusl.cz/ntk/nusl-240117.
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The theoretical part of this thesis describes the rheology of bituminous binders, aging of asphalt binders and laboratory methods simulating short and long term aging. The following describes an empirical tests (needle penetration, softening point ring ball method) and functional tests (complex shear modulus and phase angle, dynamic viscosity), which are performed in the dynamic shear rheometer. At the end of this section, laboratory aging of bituminous binders using method RTFOT and method RTFOT + PAV is described in more detail. In the practical part of this thesis, the results of all tests performed on the binders aged using RTFOT + PAV are introduced and compared with results of properties of non-aged binders and binders aged by 3xRTFOT.
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Zábranský, Ivo. "Vlastnosti nízkoteplotních polymerem modifikovaných asfaltů." Master's thesis, Vysoké učení technické v Brně. Fakulta stavební, 2019. http://www.nusl.cz/ntk/nusl-392123.
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The Diploma thesis is focus on polymer modified bitumen for warm mix asphalt. The theoretical part of the thesis describes additives which influence the properties of bitumen for their use and reduction of production and service temperatures. Further, the theoretical part describes the conclusions from the researches. This part also describes empirical and functional tests of bituminous binders. The practical part presents the results of individual tests. Tests were performed on samples of non-aged, aged by RTFOT and RTFOT + PAV methods. The results of the work and the assessment of the suitability of bituminous binders are summarized at the end of the thesis.
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Musil, Vladimír. "Relaxace smykového napětí asfaltových pojiv v DSR." Master's thesis, Vysoké učení technické v Brně. Fakulta stavební, 2015. http://www.nusl.cz/ntk/nusl-227690.
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The thesis describes the relaxation properties of bituminous binders determined in dynamic shear rheometer (DSR). Paving bitumen, polymer modified bitumen (PMB) and crumb rubber modified bitumen (CRmB) were chosen for comparison. In order to describe the effects of ageing on asphalt binders relaxation properties, the laboratory simulation of ageing using RTFOT and 3xRTFOT method was performed. For each binder were simultaneously conducted tests of needle penetration, softening point and elastic recovery. Selected bitumens were used for the production of asphalt mixtures. The low-temperature properties tests (TSRST) were performed for these mixtures, when the results were compared to the relaxation properties of binders determined in the DSR.
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Gromeš, Vít. "Studium reologických vlastností betonů s přídavkem polymerních vláken upravených nízkoteplotním plasmatem." Master's thesis, Vysoké učení technické v Brně. Fakulta stavební, 2013. http://www.nusl.cz/ntk/nusl-225912.
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Polypropylene fibers are used in concrete mixtures to avoid early cracks during shrinkage. Low thickness of each fiber and low density are reasons, why these fibers are effective in small dosage. Their disadvantages are smooth surface and hydrophobic character of polypropylene, thus it is necessary to improve their surface for better spread during mixing and to reach needed adhesion between fibers and cement paste. In present time are using chemical solutions applied on surface of the fibers to provide better water absorption, but the trend is reducing of using chemicals in industry and this situation demands new technology. There is possible solution, polypropylene fibers treated by low-temperature plasma. This method was developer by cooperation Masaryk University in Brno with company KrampeHarex and Brno Universiry of Technology. The goal of this thesis is to bring comparison, of influence on rheology properties of fresh concrete, between admixed the fibers with applied chemical layer and low-temperature plasma treated polypropylene fibers.
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Pěnčík, Michal. "Reologické vlastnosti asfaltových pojiv." Master's thesis, Vysoké učení technické v Brně. Fakulta stavební, 2015. http://www.nusl.cz/ntk/nusl-227653.
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The Diploma thesis is focused on rheological properties of bituminous binders and mixtures. Above all, it describes the changes of these properties of samples of bituminous binders and mixtures. Those were brought by the process of laboratory aging, since it simulates the changes occurring in the in the real-life conditions. The theoretical part depicts the field of rheology and methods utilized for simulating the ageing of binders and mixtures. The practical part describes the process of preparation of samples and its testing. Firstly, the ageing of bituminous mixture by the means of BSA method (Braunschweiger Alterung) took place, which was followed by preparing the solids for testing the modulus of stiffness and main testing. The rest of the mixture was used for extracting the binder. Tests with the binder were focused on the usage of dynamic shear rheometer (complex shear modulus, dynamic viscosity). The last part of the work is dedicated to the comparison of the outcomes of testing.
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Coufalík, Pavel. "Reologické vlastnosti asfaltových pojiv." Doctoral thesis, Vysoké učení technické v Brně. Fakulta stavební, 2017. http://www.nusl.cz/ntk/nusl-355627.
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Dissertation thesis is focused on rheological properties of asphalt binders and on changes of their performance during the lifetime in road structures. Aging processes of asphalt binders and methods of laboratory aging are described in the theoretical part of the thesis. Furthermore, basic rheological models and related test methods for the evaluation of asphalt binders are described. In the practical part, properties of asphalt binders are investigated after aging process and their performance is evaluated by empirical and functional test methods. The various methods of aging are compared with each other and a relationship between real conditions and laboratory aging is researched. In the next section, vacuum flashed cracked residue (VFCR) is added to the selected asphalt binders and their influence on rheological properties during description of aging of asphalt binders is investigated. The results were used in publication of two certified methodology under the title „The methodology for the evaluation of paving bitumen in terms of susceptibility to thermal oxidative aging“ and „The methodology describes laboratory aging of asphalt mixtures“. The results of the thesis are listed in the conclusion.
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Hegrová, Michaela. "Vliv etherů celulózy na reologické vlastnosti vápna." Master's thesis, Vysoké učení technické v Brně. Fakulta stavební, 2018. http://www.nusl.cz/ntk/nusl-371927.
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The subject of this diploma thesis is a study of the influence of cellulose ethers on the rheological properties of lime. The theoretical part focuses on rheological parameters, techniques and test equipment used in rheology measurements. Various types of cellulose ethers and their influence on the rheological properties of fresh mortars are described. The practical part deals with the study of the influence of different types and quantities of cellulose ethers on the properties of fresh lime pastes and mortars. The results were obtained from measurements on a rotational rheometer with a special geometry for building materials. Measuring methods used were flow and oscillatory tests. Yield stress, viscosity and flow index were determined by the flow measurement. The stability and stiffness of fresh materials were determined during the oscillation measurements. The measured results are then evaluated and compared.
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Yengul, Sanjay S. "Shear wave rheometry with applications in elastography." Thesis, 2019. https://hdl.handle.net/2144/34923.
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The goal of elastography is to map the mechanical properties of soft tissues associated with health and disease. The mechanical property of interest in this work is the complex shear modulus, composed of a real part, the storage modulus, which is a measure of elasticity, and an imaginary part, the loss modulus, which is a measure of viscosity. Together, they determine the speed and attenuation of shear waves in the medium. Elastography techniques based on either ultrasound imaging or MRI can image shear wave propagation and thus are capable of measuring shear wave speed and attenuation.
Dispersion, or the frequency-dependence of material parameters, is a primary confounding factor when comparing measurements between different shear wave elastography implementations. Prior attempts at quantifying this frequency-dependence suffered from inaccurate modeling assumptions and low signal-to-noise ratios (SNR). To overcome these limitations, a high-fidelity forward model of shear wave propagation in homogeneous media was developed. The model is an exact semi-analytical solution of Navier's equation and is well-suited for acoustic radiation force impulse shear wave elastography (ARFI-SWE) because it does not require precise knowledge of the strength of the source, nor its spatial or temporal distribution. Unlike models used in ARFI-SWE heretofore, it accounts for the vector polarization of shear waves and exactly represents geometric spreading of the shear wavefield, whether spherical, cylindrical, or neither. Furthermore, it is material-model independent, i.e. it makes no assumption about the frequency-dependence of material parameters. It overcomes the problem of low SNR through spatial averaging and enables estimation of the frequency-dependent complex shear modulus over a wider frequency range than has hitherto been possible. This improved ARFI-SWE was named Shear Wave Rheometry (SWR). By combining SWR with a novel torsional vibration rheometry, dispersion in tissue-mimicking gels was quantified from 1--1800 Hz. The measurements show sizable frequency-dependent variation in the shear modulus of gelatin, a material often assumed to be non-dispersive based on narrow-band measurements. SWR measurements in ex vivo bovine liver tissue yielded complex shear modulus estimates from 25--250 Hz and showed that liver tissue exhibits significant dispersion in this frequency range: a factor of 4 increase in the storage modulus and a factor of 10 increase in the loss modulus. Quality metrics showed that liver tissue can be reasonably approximated as homogeneous and isotropic for ARFI-SWE measurements in this frequency range.
Results demonstrate that accounting for dispersion is essential for meaningful comparisons of measurements between systems. Moreover, improved tissue characterization enabled by SWR may have clinical relevance, for example, in the diagnosis and monitoring of chronic liver disease.
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Kolitawong, Chanyut. "Local shear stress transduction in sliding plate rheometry." 2002. http://www.library.wisc.edu/databases/connect/dissertations.html.
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(6620462), Eduard Andres Caicedo Casso. "SHEAR RHEOMETRY PROTOCOLS TO ADVANCE THE DEVELOPMENT OF MICROSTRUCTURED FLUIDS." Thesis, 2019.
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This doctoral dissertation takes the reader through a journey where applied shear rheology and flow-velocimetry are used to understand the mesoscopic factors that control the flow behavior of three microstructured fluids. Three individual protocols that measure relative physical and mechanical properties of the flow are developed. Each protocol aims to advance the particular transformation of novel soft materials into a commercial product converging in the demonstration of the real the chemical, physical and thermodynamical factors that could potentially drive their successful transformation.
First, this dissertation introduces the use of rotational and oscillatory shear rheometry to quantify the solvent evaporation effect on the flow behavior of polymer solutions used to fabricate isoporous asymmetric membranes. Three different A-B-C triblock copolymer were evaluated: polyisoprene-b-polystyrene-b-poly(4-vinylpyridine) (ISV); polyisoprene-b-polystyrene-b-poly(N,N-dimethylacrylamide) (ISD); and polyisoprene-b-polystyrene-b-poly(tert-butyl methacrylate) (ISB). The resulting evaporation-induced microstructure showed a solution viscosity and film viscoelasticity strongly dependent on the chemical structure of the triblock copolymer molecules.
Furthermore, basic shear rheometry, flow birefringence, and advanced flow-velocimetry are used to deconvolute the flow-microstructure relationships of concentrated surfactant solutions. Sodium laureth sulfate in water (SLE1S) was used to replicate spherical, worm-like, and hexagonally packed micelles and lamellar structures. Interesting findings demonstrated that regular features of flow curves, such as power-law shear thinning behavior, resulted from a wide variety of experimental artifacts that appeared when measuring microstructured fluids with shear rheometry.
Finally, the successful integration of shear rheometry to calculate essential parameters to be used in a cost-effective visualization technique (still in development) used to calculate the dissolution time of polymers is addressed. The use of oscillatory rheometry successfully quantify the viscoelastic response of polyvinyl alcohol (PVA) solutions and identify formulations changes such as additive addition. The flow behavior of PVA solutions was correlated to dissolution behavior proving that the developed protocol has a high potential as a first screening tool.
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Paradkar, Anant R., Adrian L. Kelly, Philip D. Coates, and Peter York. "Shear and extensional rheology of hydroxypropyl cellulose melt using capillary rheometry." 2009. http://hdl.handle.net/10454/6121.
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NoWith increasing interest in hot melt extrusion for preparing polymer-drug systems, knowledge of the shear and extensional rheology of polymers is required for the formulation and process design. Shear and extensional rheology of three commercial grades of hydroxypropyl cellulose (HPC) was examined at 140, 145 and 150 degrees C using twin bore capillary rheometry at range of processing rates. The power law model fitted for shear flow behaviour up to shear strain rates of approximately 1000s(-1), above which measured shear viscosities deviated from the power law and surface instabilities were observed in the extrudate, particularly for higher molecular weight grades. Shear thinning index was found to be relatively independent of temperature and molecular weight, whilst the consistency index, indicative of zero shear viscosity increased exponentially with increase in molecular weight. Extensional viscosity of all grades studied was found to decrease with increasing temperature and increasing processing rate. Foaming of the extrudate occurred especially at low temperatures and with the high molecular weight grade. An understanding of the relationships between shear and extensional flows with temperature, processing rate and molecular weight is a useful tool for process design; optimisation and troubleshooting of Hot melt extrusion (HME) of pharmaceutical formulations.
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Lin, X., Adrian L. Kelly, Michael Woodhead, D. Y. Ren, K. S. Wang, and Philip D. Coates. "Capillary Study on Geometrical Dependence of Shear Viscosity of Polymer Melts." 2014. http://hdl.handle.net/10454/10726.
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Lin, X., Adrian L. Kelly, D. Y. Ren, Michael Woodhead, Philip D. Coates, and K. S. Wang. "Geometrical dependence of viscosity of polymethylmethacrylate melt in capillary flow." 2013. http://hdl.handle.net/10454/9681.
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NoThe shear viscosity of polymethylmethacrylate (PMMA) melt is particularly investigated by using a twin-bore capillary rheometer at four temperatures of 210, 225, 240, and 255 degrees C with different capillary dies. Experimental results show that the geometrical dependence of shear viscosity is significantly dependent on melt pressure as well as melt temperature. The measured shear viscosity increases with the decrease of die diameter at lower temperatures (210 and 225 degrees C) but decreases with the decrease of die diameter at higher temperatures (240 and 255 degrees C). Based on the deviation of shear viscosity curves and Mooney method, negative slip velocity is obtained at low temperatures and positive slip velocity is obtained at high temperatures, respectively. Geometrical dependence and pressure sensitivity of shear viscosity as well as temperature effect are emphasized for this viscosity deviation. Moreover, shear viscosity curve at 210 degrees C deviates from the power law model above a critical pressure and then becomes less thinning. Mechanisms of the negative slip velocity at low temperatures are explored through Doolittle viscosity model and Barus equation, in which the pressure drop is used to obtain the pressure coefficient by curve fitting. Dependence of pressure coefficient on melt temperature suggests that the pressure sensitivity of shear viscosity is significantly affected by temperature. Geometrical dependence of shear viscosity can be somewhat weakened by increasing melt temperature. (c) 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 3384-3394, 2013
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Mriziq, Khaled Suleiman M. "A high shear-rate optical rheometer for complex fluids." 2003. http://etd.utk.edu/2003/MriziqKhaled.pdf.
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Thesis (Ph. D.)--University of Tennessee, Knoxville, 2003.Title from title page screen (viewed Apr. 15, 2004). Thesis advisor: Robert N. Compton. Document formatted into pages (xv, 136 p. : ill.(some col.)). Vita. Includes bibliographical references (p. 120-124).
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SOLEIMANI, ABDOLRASOUL. "Use of Dynamic Phase Angle and Complex Modulus for The Low Temperature Performance Grading of Asphalt Cements." Thesis, 2009. http://hdl.handle.net/1974/5110.
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This thesis discusses and documents the validation efforts related to Ontario’s LS-299 and LS-308 test methods which are two new test methods developed for the performance-based specification grading of asphalt cement. In addition, this report presents the field validation of a simple performance indicator, loss tangent, for specification grading of asphalt cement for thermal cracking. Furthermore, another objective of this study is to investigate and compare the low temperature fracture and rheological behavior of engineered asphalt materials from field and laboratory-aged test sections on Highway 655 in northern Ontario.
Extracted asphalt cements from 20 contract sites in eastern and northeastern Ontario were tested according to Ontario’s LS-299 and LS-308 test methods. It was found that all good performing contracts that showed little or no distress showed low grade losses in LS-308 and retained high strain tolerances as measured in LS-299 compared to the poor performing contracts.
Asphalt cements recovered from these 20 contract sites in eastern and northeastern Ontario were also tested in torsion bar geometry to determine their viscoelastic properties. It was decided to focus on the phase angle, as a more direct measure for low temperature performance. Phase angle is a very sensitive parameter to small changes in rheology as the phase angle is approximately equal to the derivative of the logarithm of the stiffness with respect to frequency.
It was found that tan() was able to distinguish good from poor performers with 95% accuracy after only a short period of conditioning prior to testing. This is a considerable improvement over the current low temperature bending beam rheometer protocol.
Black space diagrams, frequency sweeps, Cole-Cole plots, and master curves were generated for comparison of field and laboratory aged materials from the Highway 655 trial in northern Ontario. The findings show that chemical hardening occurs much faster in the field than through laboratory ageing methods. Also, reversible ageing of binders may occur at low temperatures and could be linked to field performance. Furthermore, a high low temperature phase angle appears to be a reasonable indicator for thermal cracking resistance.Thesis (Master, Chemistry) -- Queen's University, 2009-08-28 15:12:29.845
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Motamed, Arash. "Constitutive modeling of viscoelastic behavior of bituminous materials." Thesis, 2012. http://hdl.handle.net/2152/23464.
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Asphalt mixtures are complex composites that comprise aggregate, asphalt binder, and air. Several research studies have shown that the mechanical behavior of the asphalt mixture is strongly influenced by the matrix, i.e. the asphalt binder. Therefore, accurate constitutive models for the asphalt binders are critical to ensure accurate performance predictions at a material and structural level. However, researchers who use computational methods to model the micromechanics of asphalt mixtures typically assume that (i) asphalt binders behave linearly in shear, and (ii) either bulk modulus or Poisson’s ratio of asphalt binders is not time dependent. This research develops an approach to measure and model the shear and bulk behavior of asphalt binders at intermediate temperatures. First, this research presents the findings from a systematic investigation into the nature of the linear and nonlinear response of asphalt binders subjected to shear using a Dynamic Shear Rheometer (DSR). The DSR test results showed that under certain conditions a compressive normal force was generated in an axially constrained specimen subjected to cyclic torque histories. This normal force could not be solely attributed to the Poynting effect and was also related to the tendency of the asphalt binder to dilate when subjected to shear loads. The generated normal force changed the state of stress and interacted with the shear behavior of asphalt binder. This effect was considered to be an “interaction nonlinearity” or “three dimensional effect”. A constitutive model was identified to accommodate this effect. The model was successfully validated for several different loading histories. Finally, this study investigated the time-dependence of the bulk modulus of asphalt binders. To this end, poker-chip geometries with high aspect ratios were used. The boundary value problem for the poker-chip geometry under step displacement loading was solved to determine the bulk modulus and Poisson’s ratio of asphalt binders as a function of time. The findings from this research not only improve the understanding of asphaltic materials behavior, but also provide tools required to accurately predict pavement performance.text
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Canon, Falla Gustavo. "Characterization and modeling of asphalt concrete from micro-to-macro scale." 2020. https://tud.qucosa.de/id/qucosa%3A75159.
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The main objectives of this research were twofold: 1). to develop advanced material characterization techniques for bitumen, mastic and mortar aiming to improve the knowledge of the behavior of asphalt concrete at micro and meso scales, and 2). to develop an efficient macro-mechanical numerical model capable of determining flexible pavement responses to traffic and environmental loads.
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Peralta, Elvira Joana Ferreira. "Study of the interaction between bitumen and rubber." Master's thesis, 2009. http://hdl.handle.net/1822/10557.
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Dissertação de mestrado em Engenharia Civil (área de especialização em Engenharia Rodoviária)Approximately 9 to 10 kg of rubber from tyres per inhabitant and year are currently discarded in the industrialized societies. It is a waste material with a highly valuable constituent: vulcanized natural and synthetic rubber. Thus, the introduction of crumb rubber in the production of asphalt rubber (AR) mixes for road pavements should be considered as a sustainable technology which transforms an unwanted residue into a new bituminous mixture highly resistant to fatigue and fracture. However, the increasing demands in relation to the quality and durability of pavements lead to the need of a profound knowledge in the physicochemical changes of the materials which constitute the AR binders. Thus, the main objective of this research project is to characterize the influence of bitumen and rubber properties and their interaction in the AR binder performance, namely by (i) evaluating the influence of the rubber morphology and physical properties of base bitumen in the physical and rheological properties of AR binder, (ii) assessing the changes that occur, at a molecular scale, in the base bitumen and in the rubber during their mutual interaction, and (iii) analyzing the aging effects during the pavement construction. In this work several base bitumens interacted with crumb rubber in order to produce AR binders, which were subsequently separated by using a modified “Basket drainage method” to recover the residual bitumen and rubber. The aging effect was studied by using the RTFOT method. Additionally, a new method, the “Sphere AR production simulator”, was developed to reproduce the AR production without the contribution of rubber. CEN standard tests and the dynamic shear rheometer were used to evaluate the changes in the properties of the binders during the production of AR. The rubber changes were studied through microscopic observation, swelling and depolymerization tests. The laboratory tests demonstrated that the aging of bitumen make it harder due to oxidation and restructuration. Likewise the AR production also contributes to its hardening because of the diffusion of light fractions of bitumen (mainly non volatile molecules) in the rubber particles. The rubber particles swelled 250 to 300% their weight, but the equivalent diameter only increased 2.5%. It was found that the 150/200 bitumen is an excellent alternative to produce AR binders. Minor changes in the loss of weight and in the rheological and physical properties of the AR binder can be observed after aging if compared with the aging effect in the other studied materials (base and residual bitumen). The physical and rheological properties of all tested materials can be related through known mathematical equations.
Nas sociedades industrializadas actuais são rejeitados aproximadamente 9 a 10 kg de pneus, por habitante por ano, sendo que os materiais desaproveitados do pneu têm um elevado valor intrínseco, nomeadamente o seu constituinte principal: borracha natural e sintética vulcanizada. Assim, a introdução de granulado de borracha na produção de misturas betuminosas com betume de borracha (BB) para pavimentos rodoviários deve ser considerada uma tecnologia sustentável, que transforma um resíduo indesejado numa nova mistura betuminosa com elevada resistência à fadiga e à fractura. No entanto, a crescente exigência de qualidade e durabilidade dos pavimentos obriga a um conhecimento profundo das alterações físico-químicas que ocorrem nos materiais constituintes do BB. Assim, o principal objectivo deste trabalho é determinar a influência das propriedades do betume e da borracha, e da sua interacção, no desempenho do BB, nomeadamente através da avaliação (i) da influência da morfologia da borracha e das propriedades físicas e reológicas do betume nas características do BB, (ii) das alterações no betume e na borracha, à escala molecular, durante a sua interacção mútua, e (iii) dos efeitos do envelhecimento durante a construção do pavimento. Neste trabalho, um conjunto de betumes interagiu com granulado de borracha para produzir BB, sendo subsequentemente utilizando um “método do cesto drenante” modificado para separar e recuperar o betume e a borracha residuais. O envelhecimento dos ligantes durante a construção do pavimento foi estudado através do método RTFOT. Foi desenvolvido um “simulador de produção do BB com esferas” para reproduzir o envelhecimento na produção do BB sem a contribuição da borracha. As alterações nas propriedades dos ligantes durante a produção de BB foram avaliadas através de normas CEN e do reómetro dinâmico de corte. As alterações na borracha foram estudadas através de observação microscópica e de ensaios para avaliação da densidade e do grau de inchamento e despolimerização. Os ensaios laboratoriais demonstraram que o envelhecimento e a produção de BB causam o endurecimento do betume, respectivamente devido à oxidação, crescimento e reestruturação molecular e devido à difusão das fracções leves do betume (principalmente moléculas não voláteis) através da borracha. As partículas de borracha incham cerca de 250 a 300% (em peso), mas o seu diâmetro equivalente aumenta apenas 2.5%. Concluiu-se que o betume 150/200 é uma boa alternativa para produção de BB. As alterações na perda de peso e nas propriedades físicas e reológicas do BB após envelhecimento são inferiores às observadas nos outros ligantes estudados. As propriedades físicas e reológicas dos materiais estudados relacionam-se através de equações matemáticas conhecidas.