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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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Test of remanency in a sport damper in dependence on a material of magnetic circuit
Polášek, Jan ; Kubík, Michal (referee) ; Roupec, Jakub (advisor)
This bachelor’s thesis deals with testing of maximal magnetic induction, remanence and B-H curve of different kinds of steels and application of this knowledge when choosing materials for magnetic circuit of magnetorheological (MR) dampers. The introduction of the thesis is intended to analyse knowledge of magnetorheological fluids and magnetic characteristics of different kinds of materials. Another part of bachelor’s thesis deals with the choice of steels of different chemical composition, heat treatment of steel, testing and comparing with FEM results. The aim of the thesis is also to design a clamping device for testing of magnetic circuit and to describe used measuring instruments and measurement methodology too.
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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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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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Enhancing of sedimentation stability using bentonit based clays
Michal, Lukáš ; Vimmr, Jan (referee) ; Roupec, Jakub (advisor)
The diploma thesis is focused on the issue of sedimentation stability of magnetorheological fluids, whis represents one of the most important characteristics determining the reliability of these fluids. Higher sedimentation stability can by achieved in several ways. Methods that are further examined in the thesis include particle polymerization and the addition of clay mineral additives. Both achieve positive results by schowing increased sedimentation stability. However, in the case of additives, the effect is much higher. In particular, the CLAYTONE 40 additive achieves a lower particle sedimentation rate while maintaining the same viscosity as the commercial LORD-122ED. The results provide significant knowledge in the field and can bring magnetorheological fluids closer to wider commercial use.
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Design of 1/4 car model for damper testing
Jaroš, Petr ; Růžička, Bronislav (referee) ; Roupec, Jakub (advisor)
This thesis deals by the design of 1/4 car model for testing vehicle dampers, which can be used to simulate the real suspension of a vehicle wheel (up to a maximum car weight of 1,970 kg) and the so-called linear wheel suspension. A linear mathematical 1/4 car model with 2 DOF (Degrees Of Freedom) and data from literature search are used to design and derive the basic parameters of the device. The thesis contains a description of the linear mathematical model and its outputs (acceleration of the sprung mass and forces acting on the sprung mass), description of designed device, descriptions of created simulations (static, modal and harmonic analysis in ANSYS Workbench 2020 R2) and conceptual design of the modifications this device for another possible use for testing of bicycles.
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Slit flow rheometer for magnetic and non-magnetic fluids
Železník, Tomáš ; Vimmr, Jan (referee) ; Roupec, Jakub (advisor)
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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Measurement of wear in shock absorber with magnetorheological fluid
Žáček, Jiří ; Strecker, Zbyněk (referee) ; Roupec, Jakub (advisor)
This bachelor thesis deals with measurement of abrasivity of magnetorheological fluids and its effect on hydraulic shock absorber. The abrasion could be measured and evaluated by many ways. The pin on block measurement method has been selected for this test. The pin was moving on a steel block while the whole system was surrounded by magnetorheological fluid. According to results, the lifetime of magnetorheological shock absorber is 4 times shorter than classical damper. Results of this thesis could be helpful in damper construction or in development of new magnetorheological fluids.
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