The thesis deals with the influence of storage time on particular physical and rheolo-gical properties of a yolk of chicken eggs. Monitored eggs were stored at 6 °C for 8 weeks. The thesis describes the influence of storage time on physical characteristics of a whole egg, such as weight and shape index. As expected, the weight loss of chicken eggs was demonstrated during eight weeks storing. Egg yolk (colour, height, width, weight, index and density) was also described and evaluated in detail. According to our estimates, there are no significant changes in weight during yolk storing. But yolk index is distinctly decreased. During the final part of monitoring rheological properties were evaluated - apparent viscosity, time dependence of viscosity and dependence of shear stress on the shear rate (flow curves). The experiments have proved Newtonian behaviour of egg yolk throughout the storage. The storage time has also clear impact on flow properties of yolk. The results of each experiment were modelled using the power law (Ostwald-de Waele) model.

This thesis is focused on the rheological properties of cow, goat and sheep milk. These kinds of milk are described and compared in the first part. The thesis describes physical properties and technology of milk transport. Next part deals with legislation about milk in the European Union and in the Czech Republic. Special attention is given to the requirements of warehouse equipment and heat treatment of milk. Another part deals with analytical properties of milk (dry matter, protein, fat, lactose, acidity of the milk, electrical conductivity and density). In the last part are monitored rheological properties of these three types of milk. Selected samples are measured with shear stress depending on the strain rate. It is important because it helps us to determine what type of fluid is milk. Then, there is monitored dependence of the dynamic viscosity at the shear stress and effect of temperature on viscosity. These experiments demonstrated that milk belongs to liquids with Newtonian behavior. To evaluation the results was used Newton's law of viscosity and Ostwald de Waele model.

This diploma thesis was focused on the rheological properties of honey. In the theoretical part of the work, there I occupied with the honey from a wider point of view: its production, general characteristics, fabrication, classification and its physical and chemical properties. The last chapter of the theoretical part dealt with the general rheology of liquids and with the rheological properties of honey. The practical part was concentrated on the rheological properties of chosen honey samples bought from beekeepers, not from the market network. Amongs the nine samples represented by three kinds of honey (rape, linden, honey dew) there was spectophotometricaly determined the colour, measured the content of carbonhydrates, the viscosity and the shear stress depending on the shear rate. The Newton model was used to assemble the flow curves (Newton viscosity law) whose the grounds it was determined that the honey belongs thanks to its rheological properties to the Newtonian liquids. Moreover, the temporal dependence of viscosity, on whose basis should have been assessed the thixotropy of honey, was established. Formula clause:

This diploma thesis deals with rheological properties of cream in this theoretical part. The first part describes the composition of milk as a basic product in the production of cream, and the definition of cream according to legislation and its composition. Another part of the thesis is focused on the production of cream and its distribution by kind. In the next chapter, attention is paid to the rheological properties of food, esspecially viscosity and density. The practical part is focused on the measurement of rheological properties of 10 whipping cream samples available on market. The fat proportion of the samples ranged between 30 - 33 %. For all of these samples, viscosiy and density were measured. For chosen samples was also determined the dependency of shear stress to shear rate. This dependence, using Ostwald-de Waele model, determines what type of fluid is involved. Another observed parameter was the dependency of the dynamic viscosity on the shear rate and the relation of this viscosity to the temperature changes. All samples were subjected to analytical determination of cream (dry matter, fat, titration acidity, active acidity, electrical conductivity). From the analysis of the fat proportion proportion, we are able to compare our measured data to the projected data declared by producers.

Some non-newtonian fluids exhibit nonmonotonous dependence of the shear stress on shear rate. This nonmonoticity leads to flow instabilities which result in formation of banded flow, namely in shear banding and vorticity banding. An important role is played here by so called stress diffusion which uniquely determines size of bands in the flow. If the classical kinetic approach is employed and the spatial inhomogeneity of the flow is taken into the account, then stress diffusion can be obtained in the fluid model, however this approach has difficulties with identifying heat transfer within the continuum. In this thesis, we present alternative approach how to introduce stress diffusion to fluid models. We employ thermodynamical framework proposed by Rajagopal and Srinivasa (2000), this approach guaranties thermodynamical consistency of resulting model and also the interplay between stress diffusion and heat transfer can be easily established. Furthermore, we extend this framework such that wider range of viscoelastic models can be obtained, in particular we derive Johnson-Segalman model. Powered by TCPDF (www.tcpdf.org)

The aim of this labor is to optimize the vortex pump. When this pump should find application on the field of health like human heart for extracorporeal circulation. We will deal with the analysis of shear stress in the pump and its size of it and consider the use nonwetting surfaces to reduce the shear stress values. All our analysis will be made by CFD calculations.

The use of flat slabs in constructions due to its many functional and economic advantages is wide-spread. Behavior of flat slabs in shear and flexure is a fairly complex problem. Therefore, the punching shear failure belongs to one of the most critical aspects in the design of concrete buildings. Over the last decades several buildings have collapsed due to the failure of the punching shear strength, resulting in loss of lives and financial damages. These disasters revealed gaps in the current (or former) design codes and recommendations. As a part of theoretical framework of the dissertation a method for predicting the punching shear strength of flat slabs was developed. Several experiments on scaled down slabs were conducted in order to verify the proposed method and for optimization of its parameters. Proposed method in development predicts the punching shear for slabs without shear reinforcement according to the EC2 and replaces the area of the shear crack with a system of struts and ties.

This master thesis shortly deals with properties and usage of the Resysta material. The main objective of this thesis is to determine a temperature influence on tensile strength of welded and glued joints made from the material Resysta, for an usage such as an outdoor furniture, temperature influence analysis of the joints and to present the results of the analysis obtained by measurements. Further objectives are: tensile strength experiment of material Resysta and to determine influence of placing the pieces in a desk in different directions. Results will serve as a basis for a specific firm; as a basis for deciding between technology of gluing and a technology of welding and also for input for a custom made single purpose machine made for welding of material Resysta. Tests were performed in exposure temperatures -30 °C, 20 °C and 60 °C. We will perform two tests; first test will focus on the tensile strength of glued and welded joints and second one will try to test of tensile strength of Resysta material. Experiments were conducted according to standards ČSN EN 205 and ISO 527-1 on the Instron 3365 testing machine. Laboratory tests showed that values of tensile strength were decreased while increasing the exposure temperature and this was consistent in every test performed. A statistical significance was also confirmed in work piece direction influence on a board. There were higher values of the tensile strength in longitudinal direction than in the transverse.

This thesis is concerned with the mechanical stress generated in thin layers applied on a substrate. The application takes place at high temperatures and due to different coefficients of thermal expansion of materials, the sample is deformed, and thereby the stress is generated. The first part of the thesis includes the derivation of the Stoney formula for uniaxial and biaxial stress in a layer. Besides, analytical calculations of the normal stress in the layer for the simplified link model, and shear stress on the layer interface were evaluated. The main part of the work consists of solving the problem using FEM modeling. Because the actual temperature behavior during the application was not known, a fictitious temperature load was used as an input. For the samples, the coefficients of thermal expansion of the layer were then searched so that the thermal load resulting deflection corresponds to the experimental data. Three types of models were created, namely the link body model, the axisymmetric model, and the solid model. The axisymmetric model was used for the calculation of samples forming circular isolines during deformation and a volume model for samples forming elliptical isolines. The result of the FEM calculations was the normal stress in the applied layers, for which corresponding relationships were created using regression analysis.

The primary objective of this masters thesis is to assess the eects of the length of crack and the angle, of which is this crack inclined on the stress and strain states at its front for the test sample loaded under shear. The rst part of this thesis will analyze the individual approaches that lead to the description of the aforementioned conditions. The second part deals with the FEM model assembly, which will lead to the fracture parameters, the values of which will be compared in part three.