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The Effect of Synovial Fluid Constituents on Friction and Lubrication of Articular Cartilage
Čípek, Pavel ; Dr. Prashant K. Sharma (referee) ; Muňoz, Anna Neus Igual (referee) ; Vrbka, Martin (advisor)
Práce se zabývá problematikou biotribologie modelu synoviálního kloubu. Cílem práce je popsat vliv složek synoviální kapaliny na formování mazacího filmu v modelu synoviálního kloubu. Práce je zaměřena na experimentální analýzu součinitele smykového tření a jeho propojení s pozorováním adsorbovaného mazacího filmu v kontaktu pomocí fluorescenční mikroskopie. Součástí práce je návrh tribometru, který umožňuje vizualizaci v průběhu experimentů. Tribometr je vyroben, kalibrován a verifikován pomocí komerčního tribometru. Dále je součástí práce návrh metodiky experimentů včetně návrhu postupu pro zpracování a hodnocení výsledků. Pro zpracování záznamu z vizualizace kontaktu byl navržen speciální software, který pracuje na principu segmentace obrazu. Poslední část práce je zaměřena na aplikaci vyvinuté metodologie spolu s nově navrženým tribometrem, což umožňuje posoudit roli složek modelové kapaliny u formování mazacího filmu v modelu synoviálního kloubu. Experimentální část je založena na měření tření za současné vizualizace kontaktu. Tato práce prezentuje originální výsledky rozšiřující oblast biotribologie synoviálního kloubu, které mohou pomoci dalšímu rozvoji účinné léčby pacientů s nemocnými klouby.
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Nanorobots
Haluza, Lukáš ; Vrbka, Martin (referee) ; Křupka, Ivan (advisor)
The point of Bachelor´s work is to illustrate Nanotechnology and Nanorbots to all. The first part concerns Nanotechnology as a science, description of nanoworld and its explanation a technical terms. The second part concerns nanorobots, their construction, succeses which was reached, areas of use, plans and problems that inhibit their full usage in ordinary life
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Comparison of frictional properties of cosmetic massage products
Dohnal, Petr ; Čípek, Pavel (referee) ; Vrbka, Martin (advisor)
This bachelor’s thesis examines tribological properties of massage products (creams and oils). Its aim is to create a comparison of the selected products. Tribometer in the pin-on-plate configuration was used for the experiment because of its ability to simulate the process of rubbing the product on the skin. Cowhide was used as a model of human skin. The attributes of products were compared based on the characteristics of the coefficient of friction during the measurements. Through the experiments a suitable parameter was found for easy comparison of the product's durability. According to the results the best oil was selected in terms of durability and lubrication. The thesis could be used as a basis for creating a standardised method for evaluation and selection of products suitable for massage purposes.
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Friction and lubrication of articular cartilage
Hilšer, Pavel ; Daniel, Matej (referee) ; Vrbka, Martin (advisor)
The main goal of this diploma thesis is to determine the role of hyaluron acid and phospholipids on friction and lubrication of articular cartilage in regard to optimization of viscosupplements. This is carried out by measuring the coefficient of friction of the articular cartilage with several lubricants. Cartilage is lubricated particularly by a conventional viscosuplement, optimized viscosuplementation with phospholipids and model synovial fluid. In order to observe the function of those viscosuplements in the human body, both are mixed with the model synovial fluid, ubiquitous in human joints, in given ratio. Experiments revealed high friction when it comes to convectional viscosupplementation as opposed to low friction of the optimized viscosuplement with phospholipids. The same situation occurs when cartilage is lubricated with those viscosuplements mixed with model synovial fluid which might lead to development of a new, better, viscosupplementation based on hyaluron acid and phospholipids.
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Effect of femoral head size on friction and lubrication in THR
Bartošík, Jan ; Dzimko, Marián (referee) ; Vrbka, Martin (advisor)
This diploma thesis concerns itself with the experimental study of friction and lubrication in the artificial hip joint depending on the head size. Measurements were made in a hip joint simulator based on the principle of pendulum. For the friction measurements artificial joints, made from three material combinations and two diameters, from two companies were used. The measurements show that the material combination has a more significant effect to friction coefficient than the head size. Using a bigger head size shows a decrease in friction coefficient for all material combinations when compared to a smaller head size. For the measurement of lubrication film the colorimetric interferometry was applied. A metal-on-glass contact pair was used, where the glass cups were made according to the real measurements of the joint cups. Four types of hip replacements with diameters of 28 and 36 mm with two different diametral clearance were measured during a constant motion of 210 seconds. Measurements show, that the lubrication film in the hip joint with a small diametral clearance increases very fast over the 800 nm value. Contact surfaces in the hip joint with a large diametral clearance aren’t separated by the lubrication film, resulting in a damage of the chromium coating in cup. A thick lubrication film results in a higher friction coefficient, when compared with hip joints with a very thin or no lubrication film.
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Effect of Conformity on Friction in Roller Bearing
Pisklák, Jan ; Zikmund, Vladimír (referee) ; Vrbka, Martin (advisor)
This master’s thesis describes the influence of conformity on friction in rolling bearings. The coefficient of friction is measured on an experimental machine - Mini Traction Machine 2 – using ball-on-disc method. The results are plotted in graphs which showing the dependence of the coefficient of friction at spin-to-roll ratio for specific conformity, normal load and speed in the contact area. The influence of load, speed or different lubricant viscosity is verified for a given value of conformity. Experimentally obtained data are compared with the mathematical model developed in MatLab, within this thesis.
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Fluid flow analysis in vicinity of exhaust valve using CFD
Šesták, Josef ; Náhlík, Luboš (referee) ; Vrbka, Martin (advisor)
This diploma thesis discuss a flow in a vicinity of exhaust valve using computational of fluid dynamics. In a light of current state of the problem solution this approach is forward but very sophisticated. Intention of author is description of multidimensional boundary of characteristic variables which determinates the flow behaviour for given geometry and boundary conditions. Technical knowlegde of fluid flow in vicinity of exhaust valve allow to design geometry which provide more effective cylinder flush out berofe the exhaust stroke will become. This process reduce quantity of loss work of piston and improve its effective pointers.
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Educational exercises for finite element method lectures
Sovadina, František ; Vrbka, Martin (referee) ; Nečas, David (advisor)
This work is concerned with mapping of exercises for teaching Finite Element Method (FEM) at Czech as well as foreign universities. The first part reviews exercises on FEM in use at Czech and foreign universities, which might be used for teaching FEM at the Faculty of Mechanical Engineering in Brno in the future. Based on the analyzed material, the aim of the second part of this work was to create a new assignment of an exercise together with its model calculation in ANSYS. The results were then proved through an experiment on a physical model.
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Mechanical-hydraulic model of vehical energy regeneration
Pisklák, Jan ; Vrbka, Martin (referee) ; Nevrlý, Josef (advisor)
This bachelor thesis is a research about mathematic-physical model of vehicle’s kinetic energy regeneration. Mr. Pourmovahed A. et al. were dealing with this problem. He used the method of the determinated thermal time constants. Pourmovahed continued in study reports written by Green W. L. and Otis D.. His scientific work covers the analytical treatment which is compared with an experimental tests.
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Experimental study of friction and lubrication in THR
Urban, Filip ; Čermák, Jan (referee) ; Vrbka, Martin (advisor)
This work analyzes problems of friction and lubrication of total hip replacement (THR). At first, experimental study of friction coefficient under various conditions was conducted using hip joint simulator based on principle of pendulum. After that, lubrication film development was observed, using colorimetric interferometry with head from THR and glass cup with respect of geometry and clearance to cups made originally for THR. With respect to research study [25] it was found that increasing contact conformity leads to increased film thickness. Also protein adsorption on articulating surfaces was observed. Thanks to adsorption 80 nm film thickness was measured even if relative surface speed was zero. Furthermore protein aggregation was observed on the border of contact zone, similar aggregations were observed by Myant et al. [29] or Vrbka et al. [25]. These aggregations are formed when lubricant is under shear stress and it can positively affect film thickness. If the relative motion of articulating surfaces is not sufficient, the protein layer can`t be refreshed enough and film thickness start decreasing. Coefficient of friction 0,13 was measured when lubricating film development was observed. Close to this value are material combinations metal on polyethylene and metal on metal.
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