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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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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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Study of Elastohydrodynamic Film Formation in Hypoid Gears
Omasta, Milan ; Dobeš, Petr (referee) ; Čermák,, Jan (referee) ; Dzimko, Marián (referee) ; Křupka, Ivan (advisor)
This PhD thesis deals with elastohydrodynamic lubrication (EHL) under the conditions that occur between mated hypoid gear teeth. The aim is to describe experimentally the behaviour of lubricating film and mechanisms of its formation. The focus is mainly placed on clarifying the influence of direction and magnitude of sliding velocity in circular and elliptical contacts. Generally, it is still assumed that the direction of sliding velocity has no effect on the resulting lubricant film. In this study optical interferometry is used to determine distribution of lubricant film thickness. This work includes new and original results which clarify the studied problem. It was found that the direction of sliding velocity affects shape of the film at high speeds. This relates to the effect on heat flow through the contact. The results have an impact on the development of general EHL theory and provide knowledge applicable in film thickness prediction in the design of real tribological nodes.
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Design and realization of the device for measurement of light scattering from surfaces of solar cells
Gründling, Vladimír ; Křupka, Ivan (referee) ; Ohlídal, Miloslav (advisor)
The principle of an original instrument for experimental measurement of electromagnetic wave scattering from rough planar surfaces is presented in the diploma theses. A design and realization of the instrument is presented too. The instrument is primarily intended for measurement of angle intensity distribution of light scattered from solar cells surfaces. Owing to a possibility to analyse surfaces with a high level anisotropy of electromagnetic wave scattering it is possible to use the instrument for a study of surfaces with an arbitrary type of the surface roughness.
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Usage of a high-speed camera for a study of changes of a lubricating film.
Mucha, Roman ; Křupka, Ivan (referee) ; Svoboda, Petr (advisor)
The aim of Bachelor´s thesis is to give an overview of the state of knowledge in the field of usage of a high-speed camera for a study of changes of a lubricating film. The first part desribes the basic terms in the field of high-speed camera. The next part of thesis deals with the history of high-speed cameras and their use in an industry, including study of changes of a lubricating film. Finally, evaluation of current status and further development are included.
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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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COHERENCE-CONTROLLED HOLOGRAPHIC MICROSCOPE
Kolman, Pavel ; Křupka, Ivan (referee) ; Kozubek, Michal (referee) ; Chmelík, Radim (advisor)
ransmitted-light coherence-controlled holographic microscope (CCHM) based on an off-axis achromatic and space-invariant interferometer with a diffractive beamsplitter has been designed, constructed and tested. It is capable to image objects illuminated by light sources of arbitrary degree of temporal and spatial coherence. Off-axis image-plane hologram is recorded and the image complex amplitude (intensity and phase) is reconstructed numerically using fast Fourier transform algorithms. Phase image represents the optical path difference between the object and the reference arms caused by presence of an object. Therefore, it is a quantitative phase contrast image. Intensity image is confocal-like. Optical sectioning effect induced by an extended, spatial incoherent light source is equivalent to a conventional confocal image. CCHM is therefore capable to image objects under a diffusive layer or immersed in a turbid media. Spatial and temporal incoherence of illumination makes the optical sectioning effect stronger compared to a confocal imaging process. Object wave reconstruction from the only one recorded interference pattern ensures high resistance to vibrations and medium or ambience fluctuations. The frame rate is not limited by any component of the optical setup. Only the detector and computer speeds limit the frame rate. CCHM therefore allows observation of rapidly varying phenomena. CCHM makes the ex-post numerical refocusing possible within the coherence volume. Coherence degree of the light source in CCHM can be adapted to the object and to the required image properties. More coherent illumination provides wider range of numerical refocusing. On the other hand, a lower degree of coherence makes the optical sectioning stronger, i.e. the optical sections are thiner, it reduces coherence-noise and it makes it possible to separate the ballistic light. In addition to the ballistic light separation, CCHM enables us to separate the diffused light. Multi-colour-light
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Effect of surface texturing on elastohydrodynamic films
Puchner, Jiří ; Dzimko, Marián (referee) ; Křupka, Ivan (advisor)
Diploma thesis describes analysis of influence of surface texturing on non-conformal rubbing surfaces. High speed camera was used to observe the effect of micro-dents of various depths on film thickness under pure rolling and rolling/sliding conditions. It can be concluded from the obtained results that micro-texture of suitable sizes can results in film thickness increase without lubrication film breakdown.
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