Pracovník Fakulty technologické Univerzity Tomáše Bati ve Zlíně prof. Ing. Martin Zatloukal, Ph.D., DSc., obhájil disertaci Aplikovaná reologie pro polymery: Od charakterizace k modelování a tokovým nestabilitám a získal vědecký titul „doktor chemických věd“. Prof. Zatloukal přispěl k rozvoji aplikované reologie polymerních tavenin, navrhl a aplikoval inovativní experimentální metodiky umožňující pochopení vlivu tahového toku a tlaku na tokové chování polymerních tavenin, vyvinul nové konstituční rovnice pro polymerní taveniny, které poskytují možnost rozlišit topologii polymerů, a vytvořil nový přístup pro modelování nestabilit volného povrchu polymerních tavenin v oblasti silně nelineární viskoelasticity. and Martin Zatloukal.
The paper presents analysis of the stress-strain behaviour due to creep in statically determinate composite steel-concrete beam according to Eurocode 2, ACI209R-92 and Gardner&Lockman models. The mathematical model involves the equation of equilibrium, compatibility and constitutive relationship, i.e. an elastic law for the steel part and an integral-type creep law of Boltzmann-Volterra for the concrete part considering the above mentioned models. On the basis of theory of the viscoelastic body of Maslov-Arutyunian-Trost-Zerna-Bažant for determining the redistribution of stresses in beam section between concrete plate and steel beam with respect to time ‘t‘, two independent Volterra integral equations of the second kind have been derived. Numerical metod based on linear approximation of the singular kernel function in the integral equation is presented. Example with the model proposed is investigated. and Obsahuje seznam literatury
The paper presents analysis of the stress and deflections changes due to creep in statically determinate composite steel-concrete beam. The mathematical model involves the equation of equilibrium, compatibility and constitutive relationship, i.e. an elastic law for the steel part and an integral-type creep law of Boltzmann-Volterra for the concrete part. On the basis of the theory of the viscoelastic body of Arutyunian-Trost-Bažant for determining the redistribution of stesses in beam section between concrete plate and steel beam with respect to time ‘t‘, two independent Volterra integral equations of the second kind have been derived. Numerical method based on linear approximation of he singular kernal function in the integral equation is presented. Example with the model proposed is investigated. The creep functions is suggested by the ACI 209R-92 model. The elastic modulus of concrete Ec(t) is assumed to be constant in time ‘t‘. The obtained results are compared with the results from the model CEB MC90-99. and Obsahuje seznam literatury
Differences in soil stability, especially in visually comparable soils can occur due to microstructural processes and interactions. By investigating these microstructural processes with rheological investigations, it is possible to achieve a better understanding of soil behaviour from the mesoscale (soil aggregates) to macroscale (bulk soil). In this paper, a rheological investigation of the factors influencing microstructural stability of riparian soils was conducted. Homogenized samples of Marshland soils from the riparian zone of the Elbe River (North Germany) were analyzed with amplitude sweeps (AS) under controlled shear deformation in a modular compact rheometer MCR 300 (Anton Paar, Germany) at different matric potentials. A range physicochemical parameters were determined (texture, pH, organic matter, CaCO3 etc.) and these factors were used to parameterize pedotransfer functions.
The results indicate a clear dependence of microstructural elasticity on texture and water content. Although the influence of individual physicochemical factors varies depending on texture, the relevant features were identified taking combined effects into account. Thus, stabilizing factors are: organic matter, calcium ions, CaCO3 and pedogenic iron oxides; whereas sodium ions and water content represent structurally unfavorable factors. Based on the determined statistical relationships between rheological and physicochemical parameters, pedotransfer functions (PTF) have been developed.
Flow of particles suspended in a fluid can be found in numerous industrial processes utilizing sedimentation, fluidization and lubricated transport such as food processing, catalytic processing, slurries, coating, paper manufacturing, particle injection molding and filter operation. The ability to understand rheology effects of particulate flows is elementary for the design, operation and efficiency of the underlying processes. Despite the fact that particle technology is widely used, it is still an enormous experimental challenge to determine the correct parameters for the process employed. In this paper we present \mbox{2-dimensional} numerical results for the behavior of a particle based suspension and compare it with analytically results obtained for the Stokes-flow around a single particle.
Food dispersions are the most frequent and most important food components. Useful information was obtained in the investigations of liquid emulsions. The results obtained in their study were compared with tomato ketchups. They were chosen as an example of food dispersions with low lipid content. A set of 20 samples of tomato ketchups purchased on the native market were analyzed by several rheological procedures (RheoStress 300) and by sensory profiling both of textural and flavour characteristics. The psychorheology was used for the determination of relationships between results of instrumental and sensory measurements. The data base obtained was processed by statistical methods. The temperature affects the results differently, but it is not useful to study temperatures below room temperature. The rheological parameters agree with the Herschel-Bulkley equation. Therefore, the psychorheology was applied as a suitable complex method. About a third of plots between two variables were significantly related. Several statistically significant relationships were obtained between rheological attributes, sensory attributes, and the combinations between rheological and a sensory attributes. Great variance in all characteristics was observed in all samples variables. Similarly as in case of lipid dispersions, the sensory texture acceptability was significantly related with the overall flavour acceptability, similarly as in case of other food dispersions. It proves the importance of texture in consumption of tomato ketchups. and Potravinářské disperze patří mezi nejrozšířenější potravinářské produkty. Potřebné informace k prezentovaným výsledkům předloženého studia byly získány předchozím studiem potravinářských emulzí. Kečupy byly vybrány jako příklad potravinářských disperzí s nízkým obsahem tuku. Bylo hodnoceno celkem 20 vzorků komerčních výrobků tomatových kečupů, zakoupených v české obchodní síti. Reologické charakteristiky byly získány pomocí rotačního reometru RheoStress 300 a texturní vlastnosti pomocí senzorické analýzy. Jako nejvhodnější metoda byla zvolena psychoreologie, která zkoumá funkční vztahy mezi reologickými parametry, stanovenými instrumentální analýzou a senzorickými charakteristikami, stanovenými senzorickou analýzou. Znalost těchto vztahů je důležitá ke kvantitativní charakterizaci tokových a deformačních dějů, probíhajících při senzorické zkoušce. Reologické parametry vyhovují stavové rovnici Herschel-Bulkley. Korelací reologických a senzorických dat byly získány v třetině případů těsné funkční závislosti s vysokými hodnotami korelačních koeficientů. Analýzy prokázaly velké rozdíly mezi jednotlivými vzorky kečupů. Při nižších teplotách by se patrně projevily zřetelněji vlivy optimální textury a získaly se bližší hodnoty mezi vzorky. Stejně jako u dříve hodnocených potravinářských produktů bylo prokázáno, že textura výrazně ovlivňuje chuťové vlastnosti, což zdůrazňuje význam textury při konzumaci rajčatového protlaku.
The paper present analysis of the stress changes due to creep in statically determinate composite steel-concrete beam. The mathematical model involves the equation of equilibrium, compatibility and constitutive relationship, i.e. and elastic law for the steel part and an integral-type creep law of Boltzmann-Volterra for the concrete part. For determining the redistribution of stresses in beam section between concrete plate and steel beam with respect to time t, Volterra integral equations of the second kind have been derived, on the basis of the theory of the viscoelastic body of Arutyunian-Trost-Bazant. Numerical method, which makes use of linear approximation of the singular kernal function in the integral equations is presented. Example with the model proposed is investigated. The creep functions is suggested by the 'CEB-FIP' models code 1990. The elastic modulus of concrete Ec(t) is assumed to be constant in time t. and Obsahuje seznam literatury