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Development of Film Thickness in Elastohydrodynamically Lubricated Compliant Contacts
Křupka, Jiří ; Fillot, Nicolas (referee) ; Glovnea, Romeo (referee) ; Křupka, Ivan (advisor)
Mazání polymerních strojních součástí, jako jsou polymerní ozubená kola, je v současné době předmětem zájmu mnoha strojírenských aplikací z hlediska simulace mazacích procesů a optimalizace tribologických podmínek pro zvýšení výkonnosti těchto součástí. Předkládaná disertační práce se zabývá experimentální studií vývoje tloušťky kapalinového filmu v elastohydrodynamicky mazaných poddajných kontaktech. Hlavním cílem práce je objasnit formování tloušťky filmu v poddajných kontaktech v přechodové oblasti (TR) mezi isoviscous-elastic (I-E) a piezoviscous-elastic (P-E) režimem elastohydrodynamického mazání (EHL). Za tímto účelem byly provedeny laboratorní experimenty na rotačním optickém tribometru v konfiguraci kulička na disku, ve kterých byla implementována metoda optické chromatické interferometrie. Experimentálně byl analyzován vliv jak reologické odezvy maziva, tak konstitutivní viskoelastické odezvy polymeru na tvorbu tloušťky kapalinového filmu. Na základě výsledků byla dokumentována nízká platnost predikčních modelů tloušťky filmu I-E a P-E v oblasti TR. Výsledky prezentované v této práci rozšiřují poznatky o tvorbě mazacího filmu v poddajných kontaktech pracujících v režimu EHL a mohou tak být zohledněny při návrhu polymerních strojních součástí nebo při řízení mazacích procesů.
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Lubricant film formation in compliant contact
Jaroš, Tomáš ; Čermák, Jan (referee) ; Nečas, David (advisor)
This diploma thesis deals with the study of film formation in compliant contact. Primary attention is dedicated to the influence of the entrainment speed and slide-to-roll ratio (SRR) on the central film thickness. Based on a research study of the available experimental methods, the fluorescence microscopy was used to achieve the aim of the work. Experiments were realized in ball-on-disk configuration. Firstly, a validation of the method was performed where the solid contact of the ceramic ball and the glass disk was analyzed. Since the measured values were in a good agreement with the theoretical prediction, a ball of NBR rubber material, which is commonly used for production of lip seals and o-rings, was subsequently used. The experimental measurements were performed under pure rolling and rolling/sliding conditions when the entrainment speeds varied in the range from 10 to 400 mm / s. A constant load of 0.2 N was applied. The measured data were then compared to the theoretical predictions for compliant contacts. The results showed that the thickness of the lubricating film gradually increases with increasing entrainment speed, which corresponds to theoretical assumption. Against expectations, evident influence of SRR on the film formation has been observed. In the last part of the thesis the measured data are confronted with previously published studies. Finally, some limitations of this study are discussed and recommendations for further improvement of the used experimental method are suggested.
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Friction of compliant contacts
Vala, Martin ; Galas, Radovan (referee) ; Nečas, David (advisor)
This bachelor’s thesis deals with the study of the friction of compliant contacts and parameters affecting it. First section of this thesis provides analysis of current problematics with friction and compliant materials. In the next section basic definition of friction, compliant material and compliant contacts is provided with an actual study of up-to-date articles. Last section of this thesis is discussion dealing with all the articles and pointing out the influencing parameters. Followed by potential research pathways.
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Analysis of lubricated compliant contact
Dočkal, Kryštof ; Dzimko, Marián (referee) ; Nečas, David (advisor)
This diploma thesis deals with the proposal of methodology for film thickness eva- luation within compliant contacts. With respect to characteristics of such contact pairs, like variable film thickness, high surface roughness, or poor conductivity and reflectivity, the usage of conventional experimental methods is particularly complicated. In present study, an optical method based on the principle of fluo- rescent microscopy was employed in present thesis. An evaluation algorithm in- volving background normalization and calibration of fluorescent intensity to film thickness was created in a form of experimental software. The proposed algori- thm was validated by using elastohydrodynamic contact formed between ceramic ball and glass disc. The measured film thickness was compared with theoretical prediction, while very good agreement of obtained data was observed. Further, a series of experiments with compliant samples was conducted, while the central film thickness was evaluated as a function of mean speed, applied lubricant, ap- plied load and slide-to-roll ratio. The last part of the thesis is focused on results analysis and discussion considering the previously published literature.
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Design of the loading mechanism for low load
Polnický, Vojtěch ; Galas, Radovan (referee) ; Nečas, David (advisor)
The aim of the bachelor’s thesis is to provide a design and full drawing documentation of instrument for applying low loads. In case of realization, the mechanism will be implemented into a ball-on-disc laboratory tribometer, which is used in the laboratory of IMID FME BUT in Brno. The first part of the thesis deals with research study of tribometers considering the configuration of test samples and loading mechanism systems. According to information analysis, four different variants are introduced. The final design is described in detail, including the information about the advantages and disadvantages. This design is developed into technical drawings and electronic models.
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Friction of compliant contacts
Vala, Martin ; Galas, Radovan (referee) ; Nečas, David (advisor)
This bachelor’s thesis deals with the study of the friction of compliant contacts and parameters affecting it. First section of this thesis provides analysis of current problematics with friction and compliant materials. In the next section basic definition of friction, compliant material and compliant contacts is provided with an actual study of up-to-date articles. Last section of this thesis is discussion dealing with all the articles and pointing out the influencing parameters. Followed by potential research pathways.
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Lubricant film formation in compliant contact
Jaroš, Tomáš ; Čermák, Jan (referee) ; Nečas, David (advisor)
This diploma thesis deals with the study of film formation in compliant contact. Primary attention is dedicated to the influence of the entrainment speed and slide-to-roll ratio (SRR) on the central film thickness. Based on a research study of the available experimental methods, the fluorescence microscopy was used to achieve the aim of the work. Experiments were realized in ball-on-disk configuration. Firstly, a validation of the method was performed where the solid contact of the ceramic ball and the glass disk was analyzed. Since the measured values were in a good agreement with the theoretical prediction, a ball of NBR rubber material, which is commonly used for production of lip seals and o-rings, was subsequently used. The experimental measurements were performed under pure rolling and rolling/sliding conditions when the entrainment speeds varied in the range from 10 to 400 mm / s. A constant load of 0.2 N was applied. The measured data were then compared to the theoretical predictions for compliant contacts. The results showed that the thickness of the lubricating film gradually increases with increasing entrainment speed, which corresponds to theoretical assumption. Against expectations, evident influence of SRR on the film formation has been observed. In the last part of the thesis the measured data are confronted with previously published studies. Finally, some limitations of this study are discussed and recommendations for further improvement of the used experimental method are suggested.
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Analysis of lubricated compliant contact
Dočkal, Kryštof ; Dzimko, Marián (referee) ; Nečas, David (advisor)
This diploma thesis deals with the proposal of methodology for film thickness eva- luation within compliant contacts. With respect to characteristics of such contact pairs, like variable film thickness, high surface roughness, or poor conductivity and reflectivity, the usage of conventional experimental methods is particularly complicated. In present study, an optical method based on the principle of fluo- rescent microscopy was employed in present thesis. An evaluation algorithm in- volving background normalization and calibration of fluorescent intensity to film thickness was created in a form of experimental software. The proposed algori- thm was validated by using elastohydrodynamic contact formed between ceramic ball and glass disc. The measured film thickness was compared with theoretical prediction, while very good agreement of obtained data was observed. Further, a series of experiments with compliant samples was conducted, while the central film thickness was evaluated as a function of mean speed, applied lubricant, ap- plied load and slide-to-roll ratio. The last part of the thesis is focused on results analysis and discussion considering the previously published literature.
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|
|
Design of the loading mechanism for low load
Polnický, Vojtěch ; Galas, Radovan (referee) ; Nečas, David (advisor)
The aim of the bachelor’s thesis is to provide a design and full drawing documentation of instrument for applying low loads. In case of realization, the mechanism will be implemented into a ball-on-disc laboratory tribometer, which is used in the laboratory of IMID FME BUT in Brno. The first part of the thesis deals with research study of tribometers considering the configuration of test samples and loading mechanism systems. According to information analysis, four different variants are introduced. The final design is described in detail, including the information about the advantages and disadvantages. This design is developed into technical drawings and electronic models.
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