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In-situ Study of Surface Topography Changes in Elastohydrodynamic Contact
Šperka, Petr ; Dzimko, Marián (referee) ; Návrat, Tomáš (referee) ; Dobeš, Petr (referee) ; Hartl, Martin (advisor)
This dissertation thesis deals with elastohydrodynamic lubrication (EHL) of surfaces with real roughness. Systematic study of surface harmonic components behaviour, during their passage of the EHL contact, by other authors led to retrieval of a uniform principle according which individual harmonic components deform inside the contact. Although the amplitude attenuation model can provide rapid tool for more accurate surface assessment in design process it has not been validated on real surfaces till now. The thesis represents pioneering work on quantitative analysis of real surfaces EHD measurements. It contains original and new results with real and model roughness features that in many cases confirm theoretical expectations. Deeper understanding of surface roughness behaviour inside EHL contact, which is typical for machine parts like bearings, gears, cams etc., can help to improve design process of the components and ultimately enable machines and equipment to work with lower energy requirements and higher durability.
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Cam-follower contact
Urban, Filip ; Zimmerman, Martin (referee) ; Šperka, Petr (advisor)
This bachelor thesis deals with construction design of a cam-follower contact simulator. At the beginning of the thesis there is a brief overview of cams, forces acting in valve train system and types of cam-follower contact wear. There is also review of other apparatuses developed for cam-follower contact research. Main part is devoted to construction design, variants of design and calculations.
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Rolling bearings for electromobility
Mbontar, Patrik ; Frýza, Josef (referee) ; Šperka, Petr (advisor)
The aim of this bachelor thesis is to describe the problems related to the use of rolling bearings in electric vehicles. Introduction includes history, distribution, and a brief description of the bearings. In the next section, there will be a description of the use, requirements and parameters for rolling bearings of combustion engine cars. In the main part of the thesis, the parameters and requirements of bearings used in electric vehicles and hybrid vehicles will be analyzed. I will continue with familiarization with dynamic actions affecting bearings and their critical requirements. In conclusion, the two types of cars and the possible development of this type of bearings will be compared.
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Laboratory simulator of radial journal bearing
Vincenc, Jan ; Čermák, Jan (referee) ; Šperka, Petr (advisor)
The master’s thesis deals with a design of a radial journal bearing simulator, which is ready to implement a transparent sapphire journal bearing to an optical observation of the oil film. The first part of this thesis contains a short review of a few currently used journal bearing test rigs. The next part of the work deals with a discussion of concept variants and a definition of important parameters. The last part contains a detailed description of the designed radial journal bearing simulator. Limitations of the designed simulator and recommendations for future improvements are also discussed. The result of the presented work is the designed journal bearing simulator which will allow observing of the oil film. The work also consists a complete design documentation.
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Friction of materials for optomechanical parts
Mořický, Ondřej ; Košťál, David (referee) ; Šperka, Petr (advisor)
This bachelor thesis deals with friction between materials used in the construction of optomechanical assemblies. The aim of the thesis is to compare coefficient of friction for different combinations of surfaces, different roughness, and different surface treatments. Experimental measurement was carried out on a tribometer using the pin-on-plate method under the dry friction conditions. Graphs of the development of coefficient of friction over time and a table to compare individual combinations were compiled from the results of the measurement. It includes an analysis of surfaces using optical profilometry before and after the tests.
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Friction reduction by surface texturing
Mauer, Milan ; Čermák, Jan (referee) ; Šperka, Petr (advisor)
The aim of this diploma thesis is to experimentally elucidate the connection between the friction of the specimen with the textured surface and the optical observation of the sliding contact surface. The thesis focuses on the configuration of the journal bearing. This configuration is achieved by replacing the block with a circular sapphire section on a block-on-ring tribometer. For exploring of the lubricant film formation, the method of optical interferometry and fluorescence is implemented on the block-on-ring tribometer. These adjustments allow examination of the effect of the textured surface on the friction coefficient and the thickness of the lubricant film. In a mixed mode, the textures cause a significant increase in friction values and reduce the thickness of the lubricant film. The negative influence of dimples increases with the increasing radial load size. In the hydrodynamic mode, the textures have a lower negative effect on the resulting values than in the mixed mode. The changes are dependent on the size of the radial load and the viscosity of the lubricant. In the hydrodynamic mode, cavitation was not observed, and the effect of the textured surface does not correspond to theoretical prerequisites, which is reflected by lower lubricant thickness and higher friction.
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Design of Experimental Stand for the Study of Railway Vehicles Sanding
Galas, Radovan ; Hruška, Marek (referee) ; Šperka, Petr (advisor)
Presented master’s thesis describes the design and the implementation of an experimental device used for the study of tribological aspects of wheel-rail contact. In this work, the reader will first learn the fundamentals such as adhesion, slip, traction curve, etc. Subsequently, the work is describing devices that are used for the study of wheel-rail contact around the world. This section is followed by the author proposed solution. The result is a twin disc device in the scale of 1:3. The device allows determining traction characteristics for different environmental conditions (presence of water, sand and oil in contact for different temperatures) and various operating parameters (contact pressure and speed). A part of this work are also the validation experiments and complete design documentation.
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The effect of surface grooves on point contacts lubrication
Matoušek, Kamil ; Čermák, Jan (referee) ; Šperka, Petr (advisor)
This diploma thesis deals with experimental study of the effect of surface grooves on distribution of lubricant film in elastohydrodynamic lubricated point contact. Lubricant film thickness was measured by ball-on-disc apparatus using an optical interferometry technique - thin film colorimetric interferometry. The effects of groove geometry, lubricant and operating conditions were studied in this diploma thesis. The effects of these variables are evaluated based on newly suggested parameter Rgi (groove influence ratio). Groove influence ratio is defined as an influenced film thickness influenced by groove divided by film thickness for smooth surfaces.
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Sliding Bearing Apparatus
Sabo, Karol ; Šperka, Petr (referee) ; Hartl, Martin (advisor)
The bachelor’s thesis concerns with a design of experimental apparatus for a film geometry detection in hydrodynamic lubrication thrust bearing using optical interferometry. The thesis includes the current state of knowledge about experimental apparatus using optical interferometry, engineering design and drawings of design apparatus
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