National Repository of Grey Literature 48 records found  1 - 10nextend  jump to record: Search took 0.02 seconds. 
Design of device for material antiseizure testing
Burk, Filip ; Kvarda, Daniel (referee) ; Šperka, Petr (advisor)
Friction between materials can be partially eliminated by lubrication between surfaces. In order to select the correct lubricating oil, it is necessary to have the necessary test means to make an evaluation. One of these is a four-ball tester, which is lacking at the BUT Institute of Design. The aim of the bachelor thesis is the design of a modification of the existing tribometer R-MAT 3 for a four-ball configuration. The review part includes a description of the preparation, measurement and evaluation of the four-ball tester and an evaluation of conventional testers. The design of the ball mounting, drive and torque transfer to the tribometer spindle was carried out. Measurement and recording of friction torque, contact force and temperature during the test was also proposed. The result is a configuration ready for implementation. The review section includes a description of the preparation, measurement and evaluation of the four-ball test and an evaluation of conventional testers.
Distribution of grease in rolling bearing
Hynek, Jakub ; Čermák, Jan (referee) ; Šperka, Petr (advisor)
The work deals with the issue of grease distribution in a rolling bearing. Grease lubricated ball bearing in this way often experience the problem of starvation, when the contact area is not sufficiently supplied with lubricant, which leads to bearing failure. In general, this is a very complex and comprehensive topic. Specifically, the description of the effect of selected parameters on the distribution of grease in the rolling bearing was solved. The evaluation took place on the contact surfaces of the inner and outer ring and bearing balls. The average film thickness in selected areas at the point of contact and in front of it were evaluated. The method for observation was fluorescence microscopy. The effects of the percentage filling of the bearing with grease, the speed, the material and the design of the cage on the distribution and distribution of the grease on the bearing surfaces are described in the thesis. The result is information about the distribution of the grease on the raceways and balls of the bearing and their immediate surroundings. It was shown that the new experimental approach used makes it possible to evaluate the amount of grease available for bearing lubrication in a real configuration.
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.
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.
Conceptual design of a polymeric gear tester in vacuum
Ptáček, Matyáš ; Šperka, Petr (referee) ; Černohlávek, Mikuláš (advisor)
The bachelor thesis deals with the conceptual design of a polymeric gear tester in vacuum. Using a test device, it is possible to test the coefficient of friction in gears. At the beginning of the work is described the issue of operating conditions of satellites in low orbit together with the effects that affect them. Subsequently, suitable polymeric materials are selected, and current publicly available test rigs are described. Based on the research, two conceptual designs are made, one of them is selected and described in detail at the end of the work.
Overview of continues variable transmission design
Fryčar, Michal ; Dočkal, Kryštof (referee) ; Šperka, Petr (advisor)
Friction variators are used in many industries mainly for their ability to continuously change the engine-to-output gear ratio while machine is running. In this paper, six types of construction were described (using a belt, chain, ball or toroidal, conical and disc wheel). Their properties were then compared based on the maximum transmitted power and transmission efficiency. The results calculated using Hertz's theories shows, that belt, chain and toroidal constructions are transmitting the highest amount of maximum torque. These results are in accordance to earlier studies in this field and they are intended to serve as a source of information for further research on topic.
Design of the triaxial vibration positioner for removing residual powder from the metal prints
Šváb, Čeněk ; Šperka, Petr (referee) ; Suchý, Jan (advisor)
This bachelor's thesis is focused on the construction of a two-axis positioner, designed for removing dust out of parts created by a 3D printer SLM 280HL. The aim of this work is to design the construction of a two-axis positioner with an integrated vibration drive. The first part deals with the description of the types of manipulators and vibration motors. Based on the obtained information, the construction issues are outlined and various design tips are proposed to address it. The most suitable design is then selected and elaborated in detail. The output is a functional design solution of a two-axis positioner with an implemented vibration motor and the ability to run in a dusty environment.
Parameters of lubricating films and rubbing surfaces in contacts operated in superlubricity regime
Poláček, Tomáš ; Hartl, Martin (referee) ; Šperka, Petr (advisor)
The work investigates the reduction of friction between non-conformal macro contacts with partial slip. The measurement of the coefficient of friction, with the magnitude of the superlubricity, is extended by the influence of relative slip, direct observation of the contact area and the measurement of the thickness of the lubricating film. It also includes a comparison of changes in topography by friction. The experiments were mainly performed on a ball-on-disk tribometer with measuring the film thickness by colorimetic interferometry. The surface roughness changes were investigated using an optical profilometer. The effect of mean velocity, slide-to-roll radio and topography were observed for selected combinations, one of which did not allow the measurement of film thickness and one did not achieve the expected reduction in friction. For the other combinations, it was possible to observe a reduction of the coefficient of friction to 0,003 or less. The influences affecting the friction between selected materials have been investigated considerably. Thus, a foundation is laid for the research of superlubricity between contacts with partial rolling. The thesis could contribute to the reduction of friction losses, earlier(quicker/faster?) and more common use of some lubricants and materials in mechanical engineering.
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.
Design of reciprocal module fixture for wear and friction measurements in tribometer
Zeman, Petr ; Šperka, Petr (referee) ; Dočkal, Kryštof (advisor)
The thesis deals with design of a clamping fixture for fastening surface samples for the reciprocating drive of the tribometer. The fixture is designed to compensate for shape deviations of the samples by tilting in two axes in a small range. The objective has been fulfilled, the tilting mechanism is achieved by rotating the spherical surface. The fixture is sufficiently rigid. It has been achieved of better user experience and repeatability of clamping. The paper contains an overview of commercially available clamping methods, their evaluation and description of the construction of the newly designed device, which simplifies the clamping of uniquely shaped samples for the reciprocating drive of the UMT TriboLab tribometer.

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2 Šperka, Pavel
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