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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.
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Hertzian contact apparatus
Marek, Jakub ; Křupka, Ivan (referee) ; Hartl, Martin (advisor)
This bachelor thesis deals with project and implementation of construction of the Hertzian contact apparatus based on commercial devices. This device will serve as education facility of Contact mechanics. Theoretical minimum needed for analytic calculation of contact between a rigid sphere and flat surface is mentioned in this thesis. Technical documentation is included.
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The effect of surface grooves on transition to mixed lubrication
Zapletal, Tomáš ; Hartl, Martin (referee) ; Šperka, Petr (advisor)
The purpose of this diploma thesis is to describe the influence of artificially produced surface grooves on transition from full EHL regime to mixed lubrication in point contact using optical interferometry. This article focuses on influences of grooves orientation, length in contact area, elastic properties of contact surfaces and different types of oil defined by pressure-viscosity coefficient. Empirical prediction model of groove influence on film thickness was established based on experimental data. The groove influence was incorporated into lubrication parameter. This modified definition was compared to classic one. It showed that avoiding groove influence in classic definition lead to significant underestimation. Influence of groove on friction coefficient is also studied.
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CAD systems for MEMS design
Lazar, Jaroslav ; Paloušek, David (referee) ; Hartl, Martin (advisor)
This thesis deals with CAD design tools for MEMS. First part describes and defines MEMS and its basic components. This is followed by a description of methods used to manufacture MEMS. The last part deals with particular CAD design tools, their modules and functions. Mentioned systems are then compared, reviewed and appropriate usage for each of them is suggested. Then the importance and advantages of MEMS are disccussed.
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Animation of force relations on power screw
Jonáš, Tom ; Klapka, Milan (referee) ; Hartl, Martin (advisor)
The bachelor thesis deals with creating animations in program Cinema 4D. The animations show what forces are generated during nut movements along the moving bolt, also show self-locking conditions and geometry between forces. These animations will be used for educational purposes for students, for a better understanding of the issue, and for a better idea of spatial distribution of forces. The thesis describes the software environment and the process of creating particular animations.
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Realization of educational problem based on torsional vibration apparatus
Bartošek, Daniel ; Hartl, Martin (referee) ; Vaverka, Michal (advisor)
The presented master´s thesis deals with realization educational tasks on torsional vibration apparatus. It was designed and tested six educational experiments, to extend student´s knowledge of the static and dynamic properties of rotary systems. On the experimental apparatus it is possible to use inertial discs, adjustable semi-rotary damper with forced vibration crank drive unit. New set of shafts extends the variability of experimental apparatus. Students can realize the measurement of dynamic characteristics and torsional vibration using oscilloscope. New frame for the apparatus which meet all operation requirements was also designed. The solved problematics and all educational tasks are described in new prepared materials for teaching.
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Effects of Non-Newtonian Lubricants on Surface Roughness in Point Contacts
Ficza, Ildikó ; Kaneta, Motohiro (referee) ; Poll, Gerhard (referee) ; Hartl, Martin (advisor)
Tato dizertační práce je zaměřena na studium deformace nerovnosti uvnitř elastohydrodynamicky mazaného (EHD) kruhového kontaktu. Práce se zabývá studiem přechodu příčné nerovnosti přes kontaktní oblast, která je modelována pomocí numerických metod. Model dále uvažuje nenewtonské chování maziva. Použitý matematický model se skládá z parciální diferenciální rovnice druhého řádu pro řešení tlaku a integro-diferenciální rovnice pro řešení elastických deformací. Pro řešení tohoto modelu je použitá takzvaná multigrid (vícesíťová) metoda. Práce obsahuje popis matematického modelu EHD kontaktu a aplikované numeriké metody. Výsledky simulací jsou porovnány s experimentálně stanovenýma hodnotama tloušťky mazacího filmu. Deformace nerovnosti uvnitř kontaktní oblasti je studována pro různé provozní podmínky (střední rychlost, poměr proklzu) a různá vlastnosti maziva.
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Design of the test rig for the observations of the lubricant distribution in the rolling bearing
Okál, Michal ; Hartl, Martin (referee) ; Košťál, David (advisor)
Given diploma thesis deals with the design and realization of a device whose purpose is to simulate real condition in the contact area of deep groove ball bearings. Direct observation of such area was then carried out. Initial part of the thesis addresses principles occurring in ball bearings, such as friction and lubrication and wear mechanisms. Several devices which are commonly used for bearing lubrication studies are then described at the work. Subsequently, author’s solution was introduced with the output of Ball-on-ring device. Ball-on-ring configuration is key feature due to its geometry since it enables to create identical conditions as those which occur in ball bearings such as contact pressure and velocities. Lubricant distribution by the contact area is analysed with fluorescent microscopy. Part of this thesis is a validation experiment and drawing documentation of the device.
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Design of Microscope LED Illumination Source
Bartoň, Luboš ; Hartl, Martin (referee) ; Šperka, Petr (advisor)
This master’s thesis deals with the construction design of microscope episcopic LED illumination source and subsequent functional sample realization. Illumination source is compatible with industrial microscope Nikon Eclipse LV150 and designed as a replacement for halogen light source. Way of collecting light is chosen with respect to search analysis results and collector optical element and LED is selected with respect to the analysis of the episcopic illuminator. Two construction designs are designed with respect to the results of photometric analyzes. Optimal design is realized and compared with used lighting sources – halogen and xenon.
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Influence of friction modifiers composition on traction in wheel-rail contact
Kvarda, Daniel ; Hartl, Martin (referee) ; Galas, Radovan (advisor)
Friction modifiers are a new effective way to control adhesion in wheel and rail contact. The aim of this diploma thesis is experimental study of the influence of the constituents of water based friction modifier on adhesion. Measurement of the adhesion behavior for different friction modifier compositions is carried out on a ball–on–disc laboratory device creating point contact. The introductory part of the experiments describes the effect of individual components on adhesion. Subsequently, combinations of different friction modifier compositions are tested. In conclusion, selected compositions are used for wear tests. The results obtained show that the performance of friction modifiers is greatly influenced by evaporation of base medium.
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