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Studies on Non-Newtonian Behavior in Slit-flow rheometer at Unsteady flow
Halama, Lukáš ; Vimmr, Jan (referee) ; Roupec, Jakub (advisor)
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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Study on stability of bidisperse MR fluid and its magnetorheological effect
Dvořáček, Ondřej ; Mazůrek, Ivan (referee) ; Roupec, Jakub (advisor)
The diploma thesis deals with the study of the behaviour of bidisperse MR fluids. The introduction gives brief research and analysis of previously published studies. In the main part of this thesis, the sedimentation properties of monodispersions and bidispersions are investigated influencing on the primary and secondary particles size, the ratio between the fractions, the total concentration of the particles dispersed in the MR fluid and the carrier fluid viscosity. The initialization sedimentation rate is used to assess sediment stability. Subsequently, MR samples are tested on a slit-flow rheometer, and flow curves are measured at different temperatures and in the presence of various magnetic fields intensities. The MR effect is evaluated by the yield stress. The study contains results describing the behaviour of investigated MR fluid samples.
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Properties and behavior of magnetorheological elastomers and foams
Zedník, Roman ; Macháček, Ondřej (referee) ; Roupec, Jakub (advisor)
This bachelor thesis provides a current overview of magnetorheological foams and elastomers. The structure of individual types of foams and elastomers was discussed here. Various operation modes which are essential for constructing of devices with these materials were explained. Further regulation options and ways of magnetic induction conduction were discussed. And most important microscopic and macroscopic properties were highlighted. Latest ways of production of these materials are mentioned here. Lastly methods of use of MR foams and elastomers were proposed and above that which of the materials is most appropriate for certain application was said.
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Numerical hydraulic model of active zone in magnetorheological damper
Regner, Dominik ; Roupec, Jakub (referee) ; Kubík, Michal (advisor)
This bachelor thesis deals with the comparison of analytic hydraulic model and numerical models of MR damper‘s active zone. Next is the study of the influence of annular gap geometry and rheological properties of MR fluid to damper‘s performance. In the first part, there is the summary of knowledge about MR dampers and used numerical approaches. Next part describes the creation of models and in the final part there is the comparison of these models and validation is completed with data from the real damper. Also, there is an evaluation of results about changes of geometry and rheology.
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Design of dual-chamber pneumatic spring
Pantůček, Michal ; Roupec, Jakub (referee) ; Macháček, Ondřej (advisor)
This thesis is engaged in the design of a pneumatic spring which will be useful for a design of a strut intended for cosmic applications. The design will be supported with an analytic calculation which to be subsequently verified by means of experiments, however, those reach beyond the scope of this thesis. The spring will be a part of a strut with adjustable shock damping. For this reason it is desirable for the spring to have the lowest passive resistances occurring mainly during sealing mutually moving parts. For the spring they are the piston, the piston rod and the cylinder. On the theoretical level the thesis should explore the possibility of replacing conventional sealings by unconventional ones and possibly determine the influence upon dynamical behaviour of the spring where the piston would not be sealed at all.
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The study of MR fluids sedimentation
Berka, Pavel ; Vimmr, Jan (referee) ; Roupec, Jakub (advisor)
This diploma thesis investigates the accelerated sedimentation of the magnetorheological fuids (MRFs) using centrifuge. Experiments are carried out at room temperature as well as at higher temperatures (40°C, 60°C and 80°C). The development of the new improved measuring device for the sedimentation evaulation is described. Magnetic components of the device were designed using FEM analysis. Newly designed device is verified. To accomplish the experiments at the high temperatures the new heated chamber for experimental centrifuge is designed and constructed. In the next part of the work full experiment of the accelerated sedimentation is performed. At final the empirical model of the sedimetation velocity for various accelerations and temperatures is synthesized.
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Design and analysis of racing pneumobile frame
Jelínek, Josef ; Roupec, Jakub (referee) ; Ranuša, Matúš (advisor)
This bachelor thesis reacts to the changes in the Aventics Pneumobil competition in the new season and proposes a solution to eliminate problems affecting drivability of the vehicle which were identified previously. Part of this thesis aims to analyze recent Institute of machine and industrial design at Brno University of Technology’s pneumobile vehicles frames and their problems. It also contains a whole new frame designing process. There are basic informations about the Aventics Pneumobil competition and its rules connected to this thesis. The process of designing a new frame requests a lot of input quantities of the vehicle. A lot of them were unknown and had to be set in order to gain the desired vehicle properties. The main part of the thesis is the construction part. A detailed CAD model is designed on the basis of chosen vehicle concept. It is then exported into a Finite element software for a strength analysis. All results are summarized in the conclusion and the next procedure is recommended.
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The study of sedimentation of MR fluids for space applications
Vančurová, Martina ; Strecker, Zbyněk (referee) ; Roupec, Jakub (advisor)
This bachelor thesis deals with experimental determination of the effect of iron particle size on the sedimentation rate of magnetorheological (MR) fluids. MR fluids from three producers are examined here: Liquids Research Limited (Great Britain), HaoHua (China) a LORD Corporation (USA). Particles describing the effect of MR fluids’ different attributes on their sedimentation are summarized in an overview of current knowledge. The development of the Matlab script, that detects and measures the size of particles in the input electron microscope images, is presented. The particles are also measured manually in some images, which is partly used as a reference measurement for the developed script. The particle size measurement results are then compared with the sedimentation behavior of examined MR fluids.
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Design of stand for magnetic seal testing
Švec, Jaroslav ; Kubík, Michal (referee) ; Roupec, Jakub (advisor)
This bachelor thesis deals with design and construction of mounting board of stand for magnetic seal testing and with control of mounted asynchronous motor using inverter. In this thesis was done analysis of ways of controlling three-phase asynchronous motor with inverter, analysis of sensors for measuring testing conditions and analysis of modular aluminium profile systems. There was created three conceptions of mounting board from which the most suitable was chosen to be built. From ways of control was chosen the most convenient way. The result of this thesis is stand for magnetic seal testing, using which will be possible to gain new knowledge of magnetic sealing and its future use.
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Limiting and Degradation Processes of Magnetorheological Suspension Dampers
Roupec, Jakub ; Bauer, František (referee) ; Ondrůšek, Čestmír (referee) ; Dobeš, Petr (referee) ; Mazůrek, Ivan (advisor)
This work deals with the research of degradation of magnetorheological (MR) fluid during long-term loading under conditions that correspond to the real load in the linear MR devices such as dampers. The behaviour of MR fluid is described by a Bingham model of viscoplastic fluid. The parameters of this model are the yield stress and viscosity. Their values are determined by the shear rate from 1 to 2,8104 s-1. Results of durability tests show a significant decrease in viscosity of MR fluid, a gradual increase in yield stress in the off-state and a significant decrease in MR effect. The paper also described the effect of temperature on these parameters and there is also designed a method of non-assembly diagnostic of the MR fluid state in the damper using the "rate of pulsation."
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