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3D print of gearbox housing model
Kopecký, Marek ; Rebenda, David (referee) ; Dočkal, Kryštof (advisor)
This bachelor thesis focuses on the design of two stage spur gearbox housing for food processor. Strength calculation was conducted using FEM analysis. State of the art from the field of transmission casing, CAD model and prototype created by 3D print are parts of the thesis. 3D printed model is meant for demonstration of bearing seats and use of normalized mechanical elements. The thesis should provide fundamentals of gearbox housing and show a solution of one case.
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The effect of proteins on friction of artificial articular cartilage
Plachý, Tomáš ; Nečas, David (referee) ; Rebenda, David (advisor)
This bachelor thesis deals with the influence of the composition of synovial fluid on the coefficient of friction of artificial cartilage. The effect of protein concentration and their combination with other components of synovial fluid on the coefficient of friction of CD hydrogels simulating artificial cartilage is observed. All experiments were performed at a constant load of 10 N, speed 10 mm / s, temperature 37 ° C. In experiments investigating the effect of a combination of hyaluronic acid and phospholipids together with proteins, concentrations corresponding to a healthy individual were used. In experiments where the effect of the proteins themselves and their own combinations was investigated, concentrations corresponding to both a healthy individual and patients with advanced osteoarthritis or patients with aseptic release of the prosthesis were used. The work shows that when using the proteins alone, or their combination, there is a decrease in concentration of friction coefficient with increasing concentration. However, if hyaluronic acid alone or phospholipids alone is added to the protein, the coefficient of friction increases. The reduction occurs only after the addition of the combination of acid and phospholipid.
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The design of eye-lens simulator
Špaček, Matěj ; Rebenda, David (referee) ; Nečas, David (advisor)
The aim of this bachelor thesis is a design of an eye-lens simulator. Tribometer module in pin-on-ring configuration was designed to allow direct observation of a contact zone. The survey of existing tribometers was conducted as a part of the thesis, based on which, three concept solutions were suggested. Final solution of the module was chosen and designed based on the concepts. The apparatus enables to simulate conditions of real human eye so it could contribute to a contact lens research and eye lubrication solution development.
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Experimental study of artificial articular cartilage friction
Kulíšek, Vlastimil ; Ranuša, Matúš (referee) ; Rebenda, David (advisor)
Many conventional materials are used to replace damaged articular cartilage, which are beginning to be replaced by innovative biomimetic materials that mimic cartilage properties. One of these materials are poly(vinyl alcohol) (PVA) hydrogels crosslinked by freeze-thawing and cast-drying method. These hydrogels possess similar mechanical as articular cartilage. In order to clarify the effect of kinematic conditions on the friction of hydrogels, three levels of sliding speed and load and a uniform lubricant – PBS were chosen. The coefficient of friction of the FT hydrogel decreased with increasing load. The dependence of the sliding speed did not show a uniform trend and corresponded to the adsorption-repellent model for PVA gels. The coefficient of friction of the CD hydrogel increased with increasing sliding speed according to the repulsion-adsorption model for PVA gels. The increase in load at low sliding speeds of CD hydrogel caused a slight decrease in the coefficient of friction. At the highest speed, there was an optimal load at which a low coefficient of friction was achieved. The CD hydrogel showed a lower coefficient of friction than cartilage. The FT hydrogel achieved a lower coefficient of friction than cartilage only at 5 N and 10 mm s- 1. This work contributes to the understanding of the tribological properties of PVA hydrogels.
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Design of mechanism for pronation and supination of the upper limb prostheses
Rebenda, David ; Košťál, David (referee) ; Paloušek, David (advisor)
The goal of of this work is to propose a mechanism for pronation and supination of the upper limb prosthesis and its subsequent implementation of functional prototype. The teoretical part summarizes the basic types of forearm amputation and the effect of restricting rotation of the forearm. It also describes the basic distribution of upper limb prostheses and drive types. Construction design includ complete technical documentation is made in Autodesk Inventor Professional 2013 and Rhinoceros 5.0 SR8. The prototype is made of aluminium and ABS plastic.
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Design of a test rig for stress visualisation using photoelasticimetry
Doležel, Miroslav ; Rebenda, David (referee) ; Michalec, Michal (advisor)
The purpose of this work is to construct a specific loading device for the observation of moving samples in the existing polariscope. The experimental method of photoelasticity is often used to observe stationary samples, but the observation of moving samples is less common. However, the time-varying development of the stress profile is very important for understanding of the stress cycles in the machine components. The theoretical part contains a basic information about the method of photoelasticity, its advantages and limitations and the possibility of its use. Then the dynamically stressed machine elements are mentioned, from which the gear is selected as a preferable element for observation in the polariscope. Furthermore, attention is focused on materials and techniques of sample production. The determination of the required load of the gear sample is based on these findings. The most suitable design of the loading device capable of inducing specified stress in the samples is proposed and the critical nodes of the structure are supported by the strength calculations. This design offers variability for clamping different sample sizes and can thus be used to investigate stress in other gear configurations as well.
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Lubrication of hip joint replacements
Rebenda, David ; Hartl, Martin (referee) ; Vrbka, Martin (advisor)
This thesis deals with the experimental study of lubrication of hip joint replacements. The influence of the synovial fluid composition and the head material to the lubricating film thickness were asssesed by using a pendulum hip joint simulator. Both of these effects were assesed under static and dynamic loading conditions. The experimental results showed that the movement of the head against the cup is unnecessary for the separation of the rubbing surfaces by a layer of adsorbed proteins. Composition of the synovial fluid then significantly influences the thickness of the lubricating film. Two opposite extremes have been observed during tests with two model synovial fluids. The first fluid formed a very strong lubricating film. The second sample almost prevent adsorption of proteins and consequently formed only very thin lubricating film. The influence of the material is noticeable when comparing the results obtained with a metal head and ceramic heads. Metal head formes under the same conditions thicker lubricating film. This evidence may be partly influenced by different diametrical clearances, which were in the case of ceramic heads higher.
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Press design for paper briquettes
Kočař, Jiří ; Rebenda, David (referee) ; Dvořáček, Jiří (advisor)
The bachelor thesis deals with an engineering design of a press briquette machine, which process refuse of paper. This refuse is used for production of paper 's, eventually paper-sawdust 's briquets. The first part contains analysis of options of processing garbage, current machines producting briquets and their versatility. The second section is focused on a final design of a pressing machine and a general description of it's parts.
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Experimental study of friction in articular cartilage
Praus, Tomáš ; Vrbka, Martin (referee) ; Rebenda, David (advisor)
This thesis deals with the experimental study of friction in articular cartilage. After the introduction to biotribology, there are described a principle of measurment on the Mini-Traction Machine and a brief description of machine itself. After that, there is a propose for a preparation and storage of cartilage samples, construction of the adapter into the MTM and research of the friction coefficient. The results of experimental research showed the negative effect of storing the samples in the refrigerator. On the other hand, the measurement of the friction coefficient of the samples stored in the freezer showed the preservation of the mechanical properties of cartilage. Even load and speed of loading have a big effect on friction. When the speed increases, the coefficient of the friction increases too. There is an extreme increase of the friction at higher speeds. But with increasing load the friction coefficient decreases.
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Effect of Viscosupplementation on Friction of Articular Cartilage
Rebenda, David ; Sawae, Yoshinori (referee) ; PhD, Axel C Moore, (referee) ; Vrbka, Martin (advisor)
Disertační práce se zabývá experimentálním studiem viskosuplementů na bázi kyseliny hyaluronové, které se aplikují do synoviálních kloubů postižených osteoartrózou. Hlavní pozornost byla věnována objasnění vlivu koncentrace a molekulové hmotnosti kyseliny hyaluronové na tření v kontaktu kloubí chrupavky resp. změnám tření v kontaktu po smíchání osteoartritické synoviální kapaliny s exogenní kyselinou hyaluronovou. Důležitou součástí experimentů bylo rovněž studium reologických vlastností synoviální kapaliny a kyseliny hyaluronové. Výsledky ukázaly, že molekulová hmotnost kyseliny hyaluronové významně ovlivňuje viskozitu a viskoelastické vlastnosti roztoku. Výrazná závislost mezi reologickými vlastnostmi kyseliny hyaluronové a třením v kontaktu však nebyla pozorována. Přimíchání kyseliny hyaluronové do synoviální kapaliny způsobí výrazný pokles součinitele tření v kontaktu. Rozdíly mezi viskosuplementy obsahující kyselinu hyaluronovou s různou molekulovou hmotností ale nijak výrazné nejsou. Nicméně, výsledky poukazují na možné ovlivnění režimu mazání v důsledku vysoké molekulové hmotnosti kyseliny hyaluronové. Tyto původní výsledky rozšiřují pochopení mechanizmů, ke kterým dochází v kloubu bezprostředně do vstříknutí kyseliny hyaluronové a mohou být použity při dalším vývoji viskosuplementů či v klinické praxi.
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