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Performance and Safety Improvement of Large-Scale Hydrostatic Bearings
Michalec, Michal ; Wodtke, Michal (referee) ; Fillon, Michel (referee) ; Svoboda, Petr (advisor)
Táto dizertačná práca sa zaoberá experimentálnym a numerickým štúdiom veľkorozmerných hydrostatických ložísk. Takéto ložiská sa používajú na presné a plynulé polohovanie veľkých konštrukcií, pretože klzné plochy ložiska sú úplne oddelené externe tlakovaným mazacím filmom. Od jeho prvého oficiálneho predstavenia v roku 1852 prebehol rozsiahly výskum na zlepšenie výkonnosti. Napriek tomu sa výskumníci primárne zameriavali na hydrostatické ložiská malých rozmerov, zatiaľ čo len veľmi malá časť výskumu sa zameriavala na väčšie rozmery tohto typu ložísk. V takýchto prípadoch vznikajú úplne iné výzvy, ktoré sú spojené s vyššou energetickou náročnosťou, výrobou dielov ložísk, dopravou a montážou. Výrobné chyby, nesprávne zarovnanie ložísk alebo neoptimálna konštrukcia môžu zhoršiť výkonnosť ložiska, čo môže viesť až k jeho poruche. Cieľom tejto dizertačnej práce je predstaviť vylepšenia výkonu a bezpečnosti do rozsiahlej metodiky návrhu hydrostatických ložísk. Zlepšenie výkonu ložiska sa vykonáva pomocou numerického modelu oblasti tekutiny, ktorý je overený pomocou experimentálnych a teoretických údajov. Táto štúdia predstavuje úplne nový prístup založený na nezávislej optimalizácii viacerých geometrických parametrov hydrostatickej ložiskovej kapsy. Zlepšenie bezpečnosti sa vykonáva čisto experimentálne. Pozornosť je zameraná na nesúosovosť klzných plôch kapsy a bežca a ich vplyv na výkon ložísk. Okrem toho je skúmaná schopnosť samo-vyrovnávania podložky s použitím poddajnej podstavy. Experimentálna časť bola vykonaná pomocou testovania hydrostatického ložiska pozostávajúceho z dvoch káps s plnou diagnostikou. Ako ukazujú výsledky, navrhovaná metodika optimalizácie geometrických parametrov hydrostatického ložiska môže zlepšiť výkon ložiska až o 20 %. Skúmanie vplyvov nesúosovosti na výkonnosť ložiska ukazuje určitý rozsah, v rámci ktorého môže ložisko stále bezpečne fungovať, zatiaľ čo poddajná podpora môže tento rozsah ešte predĺžiť. Táto štúdia predstavuje originálny výskum rozširujúci poznatky o rozsiahlych hydrostatických ložiskových systémoch smerom k lepšiemu výkonu a vyššej bezpečnosti.
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Experimental rig for study of lubricant film in compliant contact of oil seal using fluorescence technique
Michalec, Michal ; Nečas, David (referee) ; Dočkal, Kryštof (advisor)
The thesis deals with design of the device that is used for observation of lubricant film thickness in line, compliant contact of rotary lip seal. The problem is, that with use of components made from standard materials, it is not possible to look inside their contact. Therefore, it is necessary to replace one body by optical transparent material, that will allow the insight into the contact using existing equipment, which is fluorescence microscope. In theoretical part are described issues of lubrication and observing method of fluorescence. Based on findings, there was designed a device allowing observation of lubricant behaviour. The last part of thesis describes modified design of existing equipment and individual components in detail. Functionality of designed experimental rig was verified by experiments using of R834/80 mineral oil.
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Tribological characteristics of smart fluids
Michalec, Michal ; Čermák, Jan (referee) ; Svoboda, Petr (advisor)
The master's thesis deals with experimental study of tribological characteristics of smart fluids. Smart fluids are substances in liquid state reacting to the presence of magnetic or electric field by change in rheological properties. For possible application in devices using conventional lubricants is necessary to choose suitable smart fluid and study the influence of excitation on formation of lubricating layer, friction and wear. Comprehensive description of excitation influence is executed using three experimental devices and theoretical model for measurements parameters specification. Assessed are lubricant film thickness, friction coefficient and wear under smart fluid activation in non-conformal contact. Results show significant observable influence of smart fluids excitation on all assessed aspects. Understanding the mechanisms of smart fluids excitation can be a key step in development of intelligent devices with active external control of lubricant behaviour and character, that could lead to maintenance cost reduction and effectivity improvement.
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Race car bonnet shape design based on flow analysis
Šnajdr, Petr ; Kvarda, Daniel (referee) ; Michalec, Michal (advisor)
The bachelor’s thesis deals with reducing aerodynamic drag of a pneumobile. The thesis summarizes knowledge in the field of vehicle aerodynamics and the principle of CFD simulations. The essence of the work is bonnet shape design of racing pneumobile Typhoon, developed at FME BUT, for lowest possible air resistance. CFD simulations are used to observe and analyse the influence of the bonnet shape on the aerodynamics properties. The designed shape solution of the bonnet significantly contributes to the reduction of aerodynamic drag compared to the existing bonnet. Thanks to this, the vehicle’s parameters are improved from maximum speed to the range. The acquired knowledge can also help in the further development of pneumobiles and in improving the setting of the computational model described in the work.
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Design of a test rig for stress visualisation using photoelasticimetry
Doležel, Miroslav ; Rebenda, David (referee) ; Michalec, Michal (advisor)
The purpose of this work is to construct a specific loading device for the observation of moving samples in the existing polariscope. The experimental method of photoelasticity is often used to observe stationary samples, but the observation of moving samples is less common. However, the time-varying development of the stress profile is very important for understanding of the stress cycles in the machine components. The theoretical part contains a basic information about the method of photoelasticity, its advantages and limitations and the possibility of its use. Then the dynamically stressed machine elements are mentioned, from which the gear is selected as a preferable element for observation in the polariscope. Furthermore, attention is focused on materials and techniques of sample production. The determination of the required load of the gear sample is based on these findings. The most suitable design of the loading device capable of inducing specified stress in the samples is proposed and the critical nodes of the structure are supported by the strength calculations. This design offers variability for clamping different sample sizes and can thus be used to investigate stress in other gear configurations as well.
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Influence of inlet hole position in hydrostatic bearing recess using CFD simulation
Androvič, Dominik ; Svoboda, Petr (referee) ; Michalec, Michal (advisor)
This bachelor thesis deals with the influence of inlet hole position in hydrostatic bearing recess in combination with lubricating film tilting using CFD simulation in ANSYS Fluent software. Before the investigation, encapsulation of hydrostatic bearing, CFD simulation and research of hydrostatic bearings was implemented. For investigation of ours the analytical reference model of an axial hydrostatic bearing based on recommended design parameters was created. The main parameters of interest maximal recess pressure and load capacity of bearing were emerged from analytic solution. Subsequently, the maximal recess pressure and load capacity of the bearing were computed using CFD simulation for selected position of the inlet hole and the lubricating film tilt. The results indicate that the load capacity of the bearing is decreasing with the increasing lubricating film tilt. However, in case of alteration of inlet hole position even combined with selected lubricating film tilts no significant changes in maximal recess pressure or load capacity of the bearing with changing in position of inlet hole has been observed. The obtained results might be used to improve the design of hydrostatic bearings.
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Design of the anti-vibration platform for laboratory scale
Michalica, Jakub ; Michalec, Michal (referee) ; Košťál, David (advisor)
The bachelor thesis deals with the design of passive antivibration platform for laboratory weighing machine. In the first part of the work are listed some common isolation solution. Next is design of three possible solution concepts of this platform and their description. The calculations for possible isolators, analysis of deficiencies of the design and their solutions and measurements of the final antivibration characteristics of the finished piece are made. In the end the platform is compared if it satisfies required parameters.
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Methods for measuring the geometrical tolerances
Juráňová, Bára ; Michalec, Michal (referee) ; Svoboda, Petr (advisor)
The bachleor’s thesis deals with the analysis of geometric tolerancing of machine parts. The work clarifies the terms and definitions of geometric tolerancing. Simultaneously, the specifications of measuring with measuring devices and gauges, can be found here. The work also proposes a method for aplication geometric tolerance, wich is apply to the shaft od radial fan. Subsequently, the measurement of the prescribed tolerances for this part is described.
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Optimization of hydrostatic bearing recess shape
Kopřiva, David ; Omasta, Milan (referee) ; Michalec, Michal (advisor)
This bachelor's thesis deals with the problem of optimizing the recess shape of a hydrostatic bearing. It describes the principle of operation of hydrostatic bearings, their use and previous recess optimizations. A circular recess is considered as the reference geometry. This is firstly investigated by analytical calculation and CFD simulation. The results from the analytical calculation and from the calculation using the CFD simulation are then compared in terms of accuracy of CFD simulation. After verifying the CFD settings, three types of geometry are proposed based on research and previous studies, and with the help of CFD, these geometries are examined with respect to hydrostatic bearing load capacity and recess pressure. All proposed geometry types are then compared with the reference geometry. The results show that the reference geometry has the best results in terms of bearing load capacity and recess pressure. From the point of view of asymmetrical loading and damping, the use of the proposed geometries seems to be more appropriate. This thesis describes a detailed procedure for setting up the CFD and can serve as a basis for further optimization.
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Application of drawingless documentation in the design of a milling clamping device
Schneider, David ; Michalec, Michal (referee) ; Svoboda, Petr (advisor)
The bachelor's Thesis describes the construction of a milling fixture for clamping a component on a machine tool using drawing-less documentation. Available methods of clamping workpieces for machining are described here, and the creation of drawing-less documentation is further explained. Today, in the vast majority of cases, classic drawing documentation is used, which is in many ways more tedious than the processing of described 3D digital data about the model. The work describes the creation of drawing-less documentation on a specific design solution of a milling clamping device. This solution is developed on the basis of three proposals for possible conceptual solutions for the clamping fixture. Complete, drawingless documentation of all individual parts of the product. The bachelor's thesis shows the advantages of drawing-less documentation compared to 2D drawings of components, but also mentions shortcomings that reduce the overall impression. A possible improvement that could simplify the presentation of digital model data is suggested.
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