|
|
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.
|
|
|
The effect of texture geometry on friction and lubricating film formation in radial journal bearing
Katrincová, Tereza ; Čermák, Jan (referee) ; Šperka, Petr (advisor)
The aim of this diploma thesis is to find out how the geometric parameters of circular textures affect the friction and lubrication in a conformal contact. The configuration of a partial, radial, hydrodynamic bearing was investigated on a modified block on-ring device, where the block was replaced by a sapphire section. The device allows simultaneous measurement of friction and optical observation of processes in contact. The light induced fluorescence method was used for the measurement of film thickness. None of the studied texture combinations had a positive effect on the transition from hydrodynamic mode to mixed lubrication mode. Textures in the narrow band of the combination of diameter and depth have a positive effect, outside of them negative effect of texture on friction and film thickness was observed.
|
|
|
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.
|
|
|
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.
|
|
|
The effect of surface texture on friction and lubrication of axial plain bearings
Knotek, Jan ; Hartl, Martin (referee) ; Šperka, Petr (advisor)
This paper deals with the influence of textures on friction and lubrication of axial plain bearings. Targeted texturing has the potential to affect the performance of mechanical components, where the main parameter is the friction coefficient and the thickness of the lubricating layer. Many experimental studies have been published so far, but few of them lead to a more detailed understanding of the function of textures on parallel surfaces and their interaction with a wedge-shaped gap. The problem was modeled in this work using a pin-on-disk configuration operated with controlled tilt in the hydrodynamic lubrication regime. In contrast to previously published studies, the thickness of the lubricating film was measured in real-time during the experiment using fluorescence microscopy, along with the friction coefficient. It has been demonstrated that textures are generally more beneficial in conditions with parallel surfaces compared to conditions with wedge-shaped gaps. For the case of parallel surfaces, the influence of partial texturing was identified, where the surface textured with a quarter of its area located at the entrance to the contact in the centerline led to the most positive results. In addition to partial texturing, the influence of texture size and the pattern of their distribution on the contact surface was confirmed. Parallel surfaces showed a high sensitivity of results to small changes in surface tilt. However, with increasing tilt, the effect of the wedge-shaped gap dominated over the effect of textures, and their contribution was typically in the range of single-digit to low double-digit percentages.
|
|
|
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.
|
|
|
The effect of texture geometry on friction and lubricating film formation in radial journal bearing
Katrincová, Tereza ; Čermák, Jan (referee) ; Šperka, Petr (advisor)
The aim of this diploma thesis is to find out how the geometric parameters of circular textures affect the friction and lubrication in a conformal contact. The configuration of a partial, radial, hydrodynamic bearing was investigated on a modified block on-ring device, where the block was replaced by a sapphire section. The device allows simultaneous measurement of friction and optical observation of processes in contact. The light induced fluorescence method was used for the measurement of film thickness. None of the studied texture combinations had a positive effect on the transition from hydrodynamic mode to mixed lubrication mode. Textures in the narrow band of the combination of diameter and depth have a positive effect, outside of them negative effect of texture on friction and film thickness was observed.
|
|
|
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.
|
|
|
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.
|
guest ::
