Academic literature on the topic 'Reologický model'
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Journal articles on the topic "Reologický model"
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Sheremeta, R. "REVIEW OF REOLOGICAL MODELS." Bulletin of Lviv National Agrarian University. Agroengineering Research, no. 22 (December 1, 2018): 22–30. http://dx.doi.org/10.31734/agroengineering2018.01.022.
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Vítěz, Tomáš, and Libor Severa. "On the rheological characteristics of sewage sludge." Acta Universitatis Agriculturae et Silviculturae Mendelianae Brunensis 58, no. 2 (2010): 287–94. http://dx.doi.org/10.11118/actaun201058020287.
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The work is focused on characterization of rheological behavior of sewage sludges sampled at different stages of waste water treatment. The main attention was focused on dynamic viscosity dependence on temperature, and shear rate. The sludge samples were examined under temperature ranging from 1 °C to 25 °C and under shear rate ranging from 0.34 s−1 to 68 s−1. Rotary digital viscometer (concentric cylinders geometry) was used to perform the reological measurements. The solids content of the sludge samples ranged from 0.43 % to 21.45 % (A and C samples, respectively) and ash free dry mass from 56.21 % to 67.80 % (A and B samples, respectively). The tested materials were found to be of non–Newtoninan nature and temperature dependent. Measured data were successfully characterized by several mathematical models (Arrhenius, Bingham Plastic, Casson Law, Exponential, Gaussian, and IPC Paste) in MATLAB® software with satisfying correlations between experimental and computed results. The best match (R2 = 0.999) was received with use of Gaussian model, in both cases, shear rate and temperature dependence. The results are quite useful e.g. for the purpose of technological equipment design.
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Nikitin, Oleg. "MONITORING AND ANALYSIS OF ROOM-AND-PILLAR MINING WITH CONTINUOUS MINER IN ESTONIAN OIL SHALE MINES." Environment. Technology. Resources. Proceedings of the International Scientific and Practical Conference 1 (June 20, 2001): 116. http://dx.doi.org/10.17770/etr2001vol1.1944.
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In this paper, the modeling, analysis and monitoring of a room-and-pillar mining technology in an Estonian underground mines is presented. Technology is based on continuous miner as the primary production machine. Many technical and economic parameters o f production, including loss of useful minerals, depend on a correct choice of the sizes for these elements. Without the account o f reological properties o f covered rocks, in particular the character of change o f their long strength, the account of the sizes of rooms and pillars on a certain determined term is impossible. For the modeling, the existing room- and-pillars determination method by IMS and with formulas by V. Undusk, Visual Basic for Application in Excel, Maplnfo, and Fast Lagrangian Analysis of Continua was used. Model allows determining the parameters of spontaneous collapse of the pillars and\ surface subsidence, optimized the working parameters for continuous mining. Proposed method suits for stability analysis, failure prognosis and monitoring.
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Mota Lima, A. B., and D. P. F. Souza. "Efeitos das variáveis de formulação de suspensões sobre o comportamento reologico e sobre a microestrutura de filmes cerâmicos NiO-YSZ." Matéria (Rio de Janeiro) 12, no. 2 (2007): 383–93. http://dx.doi.org/10.1590/s1517-70762007000200017.
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A preparação de filme cerâmico granular compósito NiO-YSZ por deposição a jato de suspensão exige rigoroso controle das variáveis de processamento, especialmente a reologia da suspensão devido sua importância tanto na viabilização do processo de deposição como na definição da microestrutura do filme final. Neste trabalho foi estudado como as variáveis de formulação da suspensão afetam sua viscosidade e a microestrutura do filme granular. Foram escolhidas seis variáveis de formulação: teor de sólidos, razão em massa dos componentes NiO e YSZ, granulometria do NiO, teor de dispersante, tipo do modificador reologico e misturas de solventes. O efeito dessas variáveis sobre a reologia da suspensão foi avaliado com base no modelo de Mooney para suspensões concentradas. O planejamento fatorial fracionário foi escolhido como ferramenta estatística de avaliação dos efeitos das variáveis de formulação. Foi observado que os defeitos no filme granular são gerados durante o processo de secagem e ocorrem devido à seleção incorreta de aditivos de formulação da suspensão.
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Földi, L., and L. Janosi. "Analysis of electro-rheological fluid in hydraulic system." International Journal Sustainable Construction & Design 1, no. 1 (November 6, 2010): 121–26. http://dx.doi.org/10.21825/scad.v1i1.20409.
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Use of intelligent materials has been a more widespread technology in the last ten years inthe area of research and development of mechatronic equipments. It’s main reason is that someproblems of the utilization needed such a solution, which couldn’t be solved only with new materialsproduced by material texture modification.A claim has come up in the research of the mechatronical systems to develop materials that can getand understand an information from a computer and change their attribution accordingly. Theconnection, what we can establish between the computer and material, sets a limit to the qualitycharacteristics that can be operated by the computer. This transposal can be ensured by effects that’sinduction and abolition rate can be compared or the control is bigger just as the velocity of the changeof a material characteristic. From a control technology viewpoint using electric or magnetic field is themost obvious.One group of these materials is electro-reologic (ER) liquids that change their shear strengthaccording to the electric field. The flow qualities of the ER liquids can be continually changed insidecertain borders, with orders of magnitude shorter interval from the previous hydraulic solutions.Making an opportunity by to create faster controlling and regulating systems from the present ones.The main aim of this work is the modification of basic properties of this kind of liquids and specificationof its utilization possibilities in mechatronic systems such as hydraulic control equipments.Mathematical model as well as its numerical solution of a flow control valve (ER valve) as anappropriate element of hydraulic systems has been prepared during this work. Function tests of thisunit have been carried out by computer aided simulation of the above mentioned mathematical model.
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Pasalic, Snezana, and Predrag Jovanic. "Modeling of the emulsion stability using fractal dimensions." Chemical Industry and Chemical Engineering Quarterly 14, no. 3 (2008): 153–58. http://dx.doi.org/10.2298/ciceq0803153p.
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There are many developed strategies in the emulsion stability evaluation, for purpose of determining the life circle of emulsions. Most of them are based on the reological properties of the emulsions. There are very few which relay on the direct emulsion observations. In this paper we present the developed method for the emulsion stability evaluation by the direct observation of optical properties. As the stability quantification measure we propose the fractal dimension approach. The method is based on the measure of the emulsion transmittance properties, which are directly dependent on the emulsion stability at the moment of measurement. As the test emulsion the oil in the water emulsion was used. The system is classified as the stable emulsion and our intention was to find the moment when the emulsion starts to break. The emulsion transmittance properties were measured using an acquisition system, consisting of a CCD camera and a fast PC configuration equipped with the capturing software. The fractal dimensions were determined by the so called box counting method. The experimental emulsions were measured continuously within the period of 1200 h, from the moment of the emulsion creation. The changes of fractal dimensions were observed which indicates that the emulsion changed its state and therefore the stability during the time. Three regions of the emulsion life circle were divided according to the fractal dimensions measurement, which can be connected with the stable, unstable, and meta-stable states of the emulsion life circle. In the end, the model of the emulsion behavior was developed for the purpose of quantifying the changes in the experimental emulsion.
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Bashkirtseva, I. A., A. Y. Zubarev, L. Y. Iskakova, and L. B. Ryashko. "Regular and stochastic auto-oscillations in the reological model." Nelineinaya Dinamika, 2009, 603–20. http://dx.doi.org/10.20537/nd0904011.
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"Reologic properties of aqueous solutions of agar and gelatine for confectionery." Kharkov University Bulletin Chemical Series, no. 31 (2018). http://dx.doi.org/10.26565/2220-637x-2018-31-06.
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Experimentally by using the rotational viscometer and the temperature scan method the dependence of shear stress on shear rate were determined and the effective dynamic viscosity of the systems water-0.5% agar (WA), water-2% gelatin (WG) and water-0.5% agar-2.0% gelatin (WAG) in the range of shear rates 17-1021 s-1 and temperature range of 298-323 K were calculated. The obtained experimental flow curves were approximated by the equations of the Ostwald power-law model, the Herschel-Bulkley model, and the Kasson model. It is established that the experimental results with good accuracy can be described by the Herschel-Bulkley equation. The values of the yield shear stress and yield index calculated using this equation made it possible to classify the systems WA and WAG in the temperature range 298-310 K as nonlinear plastic with partial transition to pseudoplastic flow. Analysis of the temperature dependence of viscosity from the viewpoint of the activation theory of viscous flow showed a deviation from linearity of the dependence of the logarithm of viscosity on the inverse temperature with decreasing temperature, which suggests the existence of a sol-gel transition from the standpoint of the structural viscosity. The gelation temperatures thus obtained are reduced in a series of WA-WAG-WG systems. Within the framework of the structural approach, the rheological data were analyzed on the basis of the generalized rheological model of Kasson. The contributions to the viscous flow from the integral characteristics of the associates of macromolecules and individual particles calculated from experimental data during their hydrodynamic interaction allowed us to explain an effect of decreasing of viscosity WA system due to adding of gelatin by ruin of the elements of initial system.
Dissertations / Theses on the topic "Reologický model"
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Sadílek, Jiří. "Vliv teplotní historie na vztah mezi strukturou a vlastnostmi orientovaného polypropylenu." Doctoral thesis, Vysoké učení technické v Brně. Fakulta chemická, 2010. http://www.nusl.cz/ntk/nusl-233317.
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The aim of this work is to study the effect of thermal history to structure and properties not only of oriented polypropylene monofilaments with different orientation but of course of isotropic non-oriented polypropylene. Term thermal history includes thermal regimes from alpha relaxation temperature (T?) to melting temperature (Tm). This work consists of three parts. The changes of dynamic mechanical properties, strength, deformation and tensile modulus of polypropylene samples according to annealing temperature (Ta) are described in the first part of this work. In the second part, the changes of crystal phase are observed. Preferentially, calorimetric behaviour (DSC), changes of crystal dimensions and orientation function of crystal phase (X-ray) are observed. Measured values from the first and the second part of this work were used for calculation of total orientation function of PP samples. Rheological measurements are shown in the third part of this thesis. Rheological measurements consist of short isothermal creep, shrinkage of free tapes and static deformation at higher temperatures. Measured rheological values were performed using rheological models. Using these models characteristics of entropic spring, instantaneous elasticity and viscosity and tendency to get to state of ease were calculated.
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Zvolánek, Lukáš. "Experimentální a numerická analýza reologických procesů v průběhu zrání betonu." Doctoral thesis, Vysoké učení technické v Brně. Fakulta stavební, 2017. http://www.nusl.cz/ntk/nusl-355619.
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This doctoral thesis deals with the volume changes of structural concrete caused by its shrinkage. Great importance is given to the evaluation of concrete resistance against shrinkage cracking, too. A lot of physical and numerical experiments were carried out before results and conclusion of observed phenomena was publicized. The amount of physical tests and utilization rate of the experiments can be enlarged and intensified due to the usage of materials made of micro-concrete. Consequently, the design of concrete mixtures with the ordinary size of aggregate particle reflected the large knowledge obtained by micro-concrete. In this work, the effect of different fibres and its different amount was also researched. Finally, the optimized fibre concrete mixture was designed. During the testing, the unique method referred to as “Complex experiment” was developed. Obtained data from the Complex experiment allows predicting when the shrinkage cracks may occur. The final comparison between all tested materials made of concrete was performed by means of unique parameter referred to as “Critical degree of restraint”. It was proofed that the resistance of optimized fibre concrete against to shrinkage cracking is twice of ordinary concrete. Moreover, the shrinkage cracks did not occur in the developed fibre concrete during the observed period. Based on the obtained results the new scaling factors for the rheological model B4 were derived. Due to the new scaling factors, the model B4 describes the real behavior of special composite materials very well.
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Halama, Lukáš. "Studium chování nenewtonských kapalin ve slit-flow reometru za podmínek nestabilního toku." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2019. http://www.nusl.cz/ntk/nusl-399291.
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The thesis deals with the description of the unstable flow of non-Newtonian fluid in a slit-flow rheometer, which negatively affects its behaviour. The initiators of unstable fluid flow are the roughness of the rheometer slit walls, the slip on the rheometer walls, and the influence of the inlet and outlet region geometry of the rheometer slit. The work contains methodical procedures for mathematical consideration of individual unstable fluid flow initiators and design of change of slit geometry of slit-flow rheometer. Part of the work is also a comparison of the most commonly used rheological models, derivation of general relations for the creation of the velocity profile of individual rheological models and their subsequent implementation in the rheological application, which significantly simplifies the process of evaluation of measured data when measured on slit-flow rheometer. This application can be used to determine basic parameters in CFD simulations or as a teaching aid.
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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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Toledo, Paulo Ferraz de. "Propriedades reologicas de doce de banana." [s.n.], 2004. http://repositorio.unicamp.br/jspui/handle/REPOSIP/256036.
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Orientador : Celso Costa LopesDissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia de Alimentos
Made available in DSpace on 2018-08-04T01:04:55Z (GMT). No. of bitstreams: 1 Toledo_PauloFerrazde_M.pdf: 585206 bytes, checksum: f06cb5534a00056c02bc799a2d9a8188 (MD5) Previous issue date: 2004
Mestrado
Mestre em Engenharia de Alimentos
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Hotař, Petr. "Reologické vlastnosti asfaltových pojiv." Master's thesis, Vysoké učení technické v Brně. Fakulta stavební, 2014. http://www.nusl.cz/ntk/nusl-226951.
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The comparison of rheological properties (complex shear modulus and phase angle and dynamic viscosity) of four paving bitumens and two polymer modified bitumens is performed in this diploma thesis. Furthermore, the empirical tests (needle penetration and softening point) were determined on these binders. Effect of asphalt binders aging was modeled using RTFOT test and modified RTFOT test (3 x RTFOT).
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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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Pazour, Miroslav. "Časový vývoj reologických parametrů strusky aktivované různými aktivátory." Master's thesis, Vysoké učení technické v Brně. Fakulta chemická, 2021. http://www.nusl.cz/ntk/nusl-449706.
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Tato diplomová práce se zabývá aktuálními poznatky, společně s optimalizací oscilačních měření pomocí hybridního reometru, ale hlavně pozorováním změn reologických parametrů v čase past mleté granulované vysokopecní strusky aktivované různými aktivačními roztoky s koncentrací alkálií M: 4 and 7.5 moldm. Výsledky byly pro diskuzi podpořeny výstupy z Vicatovy metody a izotermické kalorimetrie. Nejprve bylo zjištěno, že limit lineární viskoelastické oblasti se zmenšuje v čase. Dále bylo pozorováno, že v time sweep testech vykazovala struska aktivovaná křemičitany nejnižší hodnoty komplexního modulu a struska aktivovaná hydroxidy o koncentraci 4 moldm nejvyšší hodnoty a ostatní pasty vykazovaly hodnoty mezi těmito dvěma extrémy a měly mezi sebou porovnatelné hodnoty. Podobný trend byl pozorován u vývoje kritické meze oscilačního napětí, získaného z amplitude sweep testů (přerušovaně a nepřerušovaně). Oba výše zmíněné parametry, komplexní modul a mez napětí, se vyvíjely v čase. Výsledky všech testů jasně ukázaly, že povrchová chemie hraje roli ve výsledném reologickém chování. Odsud, povaha a koncentrace aktivátoru ovlivňují reologické vlastnosti skrze efekty Na a K iontů, stejně tak skrze koncentraci, která má dopad na elektickou dvojnou vrstvu. Reologické chování může být také ovlivněno dalšími faktory, např. viskozitou aktivačního roztoku a celkovou kinetikou hydratačního procesu.
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Paixão, Ana Eleonora Almeida. "Escoamento anular de fluidos não-newtonianos utilizando modelo reologico a três parâmetros." reponame:Repositório Institucional da UFS, 1990. https://ri.ufs.br/handle/riufs/979.
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A industria química e também a área de prospeção de petróleo utilizam freqüentemente muitas suspensões sólido-líquido de comportamento reológico não-newtoniano com tensão residual, que é um valor crítico abaixo do qual o fluido escoa sem deformação. Essa característica exige o uso de modelos reológicos mais sofisticados para descrever o seu comportamento fluido-dinâmico. _________________________________________________________________________________________ ABSTRACT: Several solid-liquid suspensions frequently encountered in chemical industry and also in oil well drilling operations exhibit a non-Newtonian behavior with an yield stress, a critical value of stress below which they do not flow. Due to the real conditions usually verified, it is important to master calculations techniques involve the laminar also the transitional and turbulent flow regimes.
Conference papers on the topic "Reologický model"
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Martinovs, Andris, Svetlana Polukoshko, Elvijs Apeinans, and Edgars Zaicevs. "Determination constants of 4-element reological model with rebound resilience method." In 16th International Scientific Conference Engineering for Rural Development. Latvia University of Agriculture, 2017. http://dx.doi.org/10.22616/erdev2017.16.n189.
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Balevičius, Robertas. "The effect of concrete creep on the long-term tension-stiffening law and prediction of a time-dependent inertia moment of the cracked RC flexural cross-sections." In The 13th international scientific conference “Modern Building Materials, Structures and Techniques”. Vilnius Gediminas Technical University, 2019. http://dx.doi.org/10.3846/mbmst.2019.017.
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In the paper, a long-term stress-strain model is proposed for predicting the deformational response of the cracked reinforced concrete beams subjected to sustained bending. The linear and non-linear evolution creep strains is evaluated in the analytical manner by using an average stress-strain approach. The cracking and creep phenomena are coupled by two reologic elements connected in a series. In this way, the total strain of concrete prior to cracking is determined by a linear creep law accounting for the stress rate effect, while the post-cracking behavior is specified as a sum of elastic strain between cracks, creep and cracked concrete strain, defined by the descending branch of the stress-strain law. The smeared crack approach is adopted and, in turn, this law is associated with the tension stiffening phenomenon. The formulae accounting for the tension stiffening decay with time due to time-variable stress are proposed and applied in prediction of the inertia moment of the cracked RC flexural members along with the obtained results verification with the experimental data.