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Experimental Study of Lubrication Films Formation During Start-up and Reversal Motion of Rubing Surfaces
Svoboda, Petr ; Dzimko, Marián (referee) ; Čermák, Jan (referee) ; Dobeš, Petr (referee) ; Křupka, Ivan (advisor)
This dissertation is focused on the effects of both artificially produced and real roughness features on mixed lubrication film formation during start-up and reversal of non-conformal contacts operated under rolling/sliding conditions. The start-up operation of mixed lubricated contacts represents one of the transient conditions that bring the risk of the surface damage because of asperities interactions. Chromatic interferograms captured by CMOS high-speed camera during start up of the motion enabled to observe the detailed changes in lubrication film caused by surface features. The observation of the effects of surface dents artificially produced on the ball surface helped to understand better the behaviour of real surface topography. It was found that the presence of shallow surface features can help to separate mixed lubricated rubbing surfaces more efficiently than it could be suggested from the results obtained with smooth surfaces. It can be suggested from the obtain results that properly designed topography of the rubbing surfaces can help to reduce the asperities interactions under transient operational conditions.
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The effect of surface roughness on friction and lubrication in simulated gear contact
Mořický, Ondřej ; Čermák, Jan (referee) ; Šperka, Petr (advisor)
This diploma thesis deals with experimental study of the effect of surface roughness on lubricating film formation and friction behaviour in lubricated point contact. The ball-on-disc contact is operated under conditions of transition from mixed to elastohydrodynamic lubrication regime. The measurement of the thickness of thin lubrication films on generally rough surfaces is approached by fluorescence microscopy. The effects of magnitude and character of the initial roughness, including their evolution during the running-in processes, are described. The result is a closer understanding of the mechanisms taking place in this type of contact and the identification of the optimum surface roughness in terms of resistance to changes during running-in for specific operating conditions.
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Piston Ring Tribology in Internal Combustion Engines
Orbán, Tomáš ; Maršálek, Ondřej (referee) ; Raffai, Peter (advisor)
The theme of the thesis is tribology of piston rings for internal combustion engines. The work is divided into seven chapters. The first chapter deals with the piston rings, piston rings requirements, describes the main functions of piston rings, types of piston rings, compression rings and oil control rings. Finally, this chapter provides information about the kinematics of piston rings. The second chapter presents the mechanism of friction and lubrication of piston rings, is dedicated to tribology, friction, friction observation history, mechanism of friction and friction suitability. In addition, the work contains information about lubrication, specifically about a lubrication way of internal combustion engines and lubrication regimes. The third chapter deals with hydrodynamic lubrication. The theme of the fourth chapter is boundary lubrication. The fifth chapter provides information about mixed lubrication. Friction in the oil film is the theme of the sixth chapter. Last seventh chapter deals with dry contact friction due to surface roughness contact.
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Running-in of machine elements
Rejent, Pavel ; Křupka, Jiří (referee) ; Šperka, Petr (advisor)
This bachelor’s thesis deals with the effect of topography change on the running-in of a machine element. The objective was to evaluate the time change of the friction coefficient during running-in of five steel balls with different surface treatment. The experiment was performed in mixed lubrication regime. There was also a task to measure the change of surface topography after a concrete time intervals. Another task was to evaluate a fluid film thickness for every steel ball. The output of the measurement are graphs containing the time function of friction coefficient and time change of selected surface topography parameters. The change of topography was also displayed on Abbott-Firestone curves and the fluid film evaluation was compared with the predicted value. The thesis improves knowledge about running-in process and provides comparison for surface machining by three different types of sandpaper and shown change in the behaviour of machine element after lapping or polishing.
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The effect of surface roughness on friction and lubrication in simulated gear contact
Mořický, Ondřej ; Čermák, Jan (referee) ; Šperka, Petr (advisor)
This diploma thesis deals with experimental study of the effect of surface roughness on lubricating film formation and friction behaviour in lubricated point contact. The ball-on-disc contact is operated under conditions of transition from mixed to elastohydrodynamic lubrication regime. The measurement of the thickness of thin lubrication films on generally rough surfaces is approached by fluorescence microscopy. The effects of magnitude and character of the initial roughness, including their evolution during the running-in processes, are described. The result is a closer understanding of the mechanisms taking place in this type of contact and the identification of the optimum surface roughness in terms of resistance to changes during running-in for specific operating conditions.
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Running-in of machine elements
Rejent, Pavel ; Křupka, Jiří (referee) ; Šperka, Petr (advisor)
This bachelor’s thesis deals with the effect of topography change on the running-in of a machine element. The objective was to evaluate the time change of the friction coefficient during running-in of five steel balls with different surface treatment. The experiment was performed in mixed lubrication regime. There was also a task to measure the change of surface topography after a concrete time intervals. Another task was to evaluate a fluid film thickness for every steel ball. The output of the measurement are graphs containing the time function of friction coefficient and time change of selected surface topography parameters. The change of topography was also displayed on Abbott-Firestone curves and the fluid film evaluation was compared with the predicted value. The thesis improves knowledge about running-in process and provides comparison for surface machining by three different types of sandpaper and shown change in the behaviour of machine element after lapping or polishing.
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Experimental Study of Lubrication Films Formation During Start-up and Reversal Motion of Rubing Surfaces
Svoboda, Petr ; Dzimko, Marián (referee) ; Čermák, Jan (referee) ; Dobeš, Petr (referee) ; Křupka, Ivan (advisor)
This dissertation is focused on the effects of both artificially produced and real roughness features on mixed lubrication film formation during start-up and reversal of non-conformal contacts operated under rolling/sliding conditions. The start-up operation of mixed lubricated contacts represents one of the transient conditions that bring the risk of the surface damage because of asperities interactions. Chromatic interferograms captured by CMOS high-speed camera during start up of the motion enabled to observe the detailed changes in lubrication film caused by surface features. The observation of the effects of surface dents artificially produced on the ball surface helped to understand better the behaviour of real surface topography. It was found that the presence of shallow surface features can help to separate mixed lubricated rubbing surfaces more efficiently than it could be suggested from the results obtained with smooth surfaces. It can be suggested from the obtain results that properly designed topography of the rubbing surfaces can help to reduce the asperities interactions under transient operational conditions.
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Piston Ring Tribology in Internal Combustion Engines
Orbán, Tomáš ; Maršálek, Ondřej (referee) ; Raffai, Peter (advisor)
The theme of the thesis is tribology of piston rings for internal combustion engines. The work is divided into seven chapters. The first chapter deals with the piston rings, piston rings requirements, describes the main functions of piston rings, types of piston rings, compression rings and oil control rings. Finally, this chapter provides information about the kinematics of piston rings. The second chapter presents the mechanism of friction and lubrication of piston rings, is dedicated to tribology, friction, friction observation history, mechanism of friction and friction suitability. In addition, the work contains information about lubrication, specifically about a lubrication way of internal combustion engines and lubrication regimes. The third chapter deals with hydrodynamic lubrication. The theme of the fourth chapter is boundary lubrication. The fifth chapter provides information about mixed lubrication. Friction in the oil film is the theme of the sixth chapter. Last seventh chapter deals with dry contact friction due to surface roughness contact.
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