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Design of surface texturing experimental rig
Bouma, Adam ; Svoboda, Petr (referee) ; Šamánek, Otakar (advisor)
The aim of this thesis is mechanical indenter design, mainly two basic parts of this apparatus. The introductory section describes the basic techniques of mechanical surface texturing of engineering surfaces. The second part deals with the particular design of the device. It also describes the strength control of loaded components. The economic evaluation is given at the end.
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Research on the textured journal bearings for engines in automotive
Svoboda, Martin ; Hartl, Martin (referee) ; Omasta, Milan (advisor)
The aim of this thesis is to describe the effect of surface textures of radial journal bearings with polymer coating on friction and damage development using experimental tests. Wear and friction tests of real bearings with different texture geometries and surface materials were performed. It was found that the wear deterioration of the textured aluminum sliding bearing surface and neutral or positive effects on the wear of the textured bearing with polymer coating. The reason for the improvement is the good resistance to high pressures of the polymer coating and the preservation of the texture dimensions throughout the bearing run. The friction test showed an improvement in the frictional properties of the textured surfaces when the amount of lubricant in contact was insufficient. At the same time, a positive effect on tribological properties was demonstrated by reducing the lateral lubricant discharge.
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Surface texturing of rubbing surfaces
Chlachula, Petr ; Čermák, Jan (referee) ; Křupka, Ivan (advisor)
Surface texturing of rubbing surfaces represents the way how to increase tribological performances by improving the lubrication film formation and diminishing friction and wear. Its application in machine components requires detailed understanding of the mechanism taking place between rubbing surfaces in microscopic scale. This diploma thesis is focused on the processes taking place in tribology systems to consider the possibility of surface texturing applications in highly loaded machine parts operated under transient operational conditions.
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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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Study of lubricant film formation in textured conformal contacts
Plachý, Ladislav ; Dzimko, Marián (referee) ; Omasta, Milan (advisor)
The aim of this diploma thesis is to describe mechanisms involved in a lubricant film formation in textured conformal contacts. For exploring of the lubricant film formation, the method of optical interferometry is implemented on a pin-on-disc tribometer. That allows to study an influence of a texture on lubricant film thickness and coefficient of friction of textured samples. These samples have different parameters of a texture. On the basis of these effects and the visual image of the contact, the flow of lubricant in the contact area is described. Shallow dimples lead to larger film thickness in elasto-hydrodynamic lubrication regime. They act like a lubricant reservoir. Deep dimples positively affect film thickness in hydrodynamic lubrication regime, where the effect of shallow dimples descend. During experiments, the formation of a cavitation is observed. The cavitation causes a starvation of dimples in many cases. This leads to reducing of the lubricant film thickness. This effect can be eliminated by appropriate parameters of texture in operational conditions of elements.
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Study of Correlation between Grease Film Formations and Mechanical Losses on Various Surfaces
Sakai, Kazumi ; Glovnea, Romeo (referee) ; Gonçalves, David (referee) ; Křupka, Ivan (advisor)
Tato disertační práce se zaměřuje na studium závislosti mezi reakčním momentem ložiska mazaného plastickým mazivem s lithným mýdlem a vlastnostmi maziva, jako například tloušťka vytvářeného mazacího filmu, jeho reologie, struktura zpevňovadla, trakční vlastnosti či vliv topografie povrchu. Typ maziva poskytujícího nižší odpor závisí na podmínkách provozu ložiska, zejména rychlosti. Chování mazacího filmu za nízkých rychlostí má vliv na reakční moment ložiska v nízkých rychlostech. Mez toku a trakční chování koreluje s momentem ložiska za vysokých rychlostí. Schopnost zpevňovadla vstupovat do kontaktu má vliv na tloušťku filmu, vzhled kavitační oblasti na výstupu kontaktu a chování hladovění. Důvod vstupu zpevňovadla do kontaktu je jeho chemická struktura. Vysoká polárnost hydroxylových sloučenin zpevňovadla podporuje jeho vtažení kontaktními povrchy. Mazivo s nejvyšší polaritou prokázalo na površích obsahujících denty nejčastější vstup do prostoru dentů. Na základě předchozích pozorování je navržen popis principu mechanismu mazání.
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The study of transition between fully flooded and starved regimes in EHL Contact
Popelka, Michal ; Čermák, Jan (referee) ; Svoboda, Petr (advisor)
The diploma thesis deals with The study of transition between fully flooded and starved regimes in EHL Contact. The work is focused on problems of starved contact and surface texturing of rubbing surfaces. Surface texturing of rubbing surfaces is one of the adjustments that cause in a sense improved lubricity and reduce friction and wear. The aim of this study is to compare numerical models with real experimental results measured on the Experimental apparatus.
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Influence of topography of rubbing surfaces on rolling contact fatigue
Zahradník, Radek ; Čermák, Jan (referee) ; Vrbka, Martin (advisor)
This master thesis deals with influence of topography of friction surfaces on rolling contact fatigue. This influence is examined by newly reconstructed R-MAT station, whose reconstruction and fully report about it, is part of this master thesis. Influence is examined on area with higher surface's roughness which it wasn't examined before. Further research is made on area of surfaces with topographical modification with higher surface's roughness.
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Effect of surface texturing on starved contact
Jordán, Jakub ; Náhlík, Luboš (referee) ; Křupka, Ivan (advisor)
The diploma thesis deals with the analysis of the effects surface texturing on starved contact. Experimental verification was realized on apparatus simulating contact between a steel ball and glass disc using colorimetric interferometry and high-speed camera. The work deals with lubrication regimes, problems with starved contacts and surface texturing which can reduce effects of starvation on non-conformal surface contacts.
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Lubrication of combustion engines in 21st century
Súkeník, Juraj ; Nevrlý, Josef (referee) ; Křupka, Ivan (advisor)
Lubrication is inseparable part of internal combustion engines. It primary influences operation, lifetime and efficiency of internal combustion engine. This bachelor`s thesis summarizes present state and future view of internal combustion engine lubrication. The work deals with tribology of several engines sections and composition of present lubricants for internal combustion engines.
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