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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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Design of a simulator module for analysis of friction and wear of teeth during cleaning
Snopek, Lukáš ; Streďanská, Alexandra (referee) ; Vrbka, Martin (advisor)
This thesis focuses on the design of a module for the tribological simulator Bruker UMT TriboLab, which will be used in research in the field of analysis of wear of hard dental tissues and filling materials due to tooth cleaning. The aim of this work was the design of experimental conditions, module construction, creation of drawing documentation, production and subsequent implementation of a validation experiment. The conditions of the experiment were determined on the basis of research and to create an optimal design solution, prototypes were continuously produced using the 3D printing method. Finally, two toothbrush fixtures and two dental filling sample fixtures were made based on the drawing documentation. Subsequent assembly of the fixtures and the implementation of the experiment on the tribometer verified their functionality, which makes it possible to declare all the goals successfully met. Now these fixtures will be part of several research tasks in the field of oral biotribology.
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Computational systems based on FEM for designers
Frémund, Libor ; Vaverka, Michal (referee) ; Vrbka, Martin (advisor)
This work deal with computational systems on base method final elements intended for engineer. There are descibed most often used systems, their function and included moduls that help engineer at work. Work describes four most widely used computing program - ANSYS Workbench, COSMOS DesingSTAR, Abaqus and FEMPRO. Every system is further dispersed to the subchapter, in which are circumscribed his characteristics and possibility working system. At the close are reviewed and planed individual systems and further also intended fitness using single system under given conditions.
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Review of methods to determining wear in hip replacements
Zapletal, Jakub ; Vrbka, Martin (referee) ; Ranuša, Matúš (advisor)
This bachelor thesis analysis issues of observation and measurement of wear on hip replacements. First of all there is a description of historical milestones in development of hip prosthesis. Afterwards there is a recherché study of measuring methods and devices, whereas each one of them is reviewed for pros and cons. In the last section these methods are compared and there is an author’s recommendation for the most viable method for observation and measurement of wear on hip prosthesis.
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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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Wear analysis of extracted polyethylenes of total hip replacements using optical methods
Přikryl, Adam ; Morovič, Ladislav (referee) ; Vrbka, Martin (advisor)
An experimental methodology for wear assessment of extracted polyethylene hip implants was designed in this diploma thesis. Methodology uses optical 3D scanner and optical profilometer for analysis of wear. Designed methodology for wear analysis was validated by gravimetric method. The results of validation were in good agreement with the increase of wear rate. Validation results show that the methodology is not suited for wear assessment of metal and ceramic implants which have small wear rates. On the other hand the methodology is more than useful for wear assessment of polyethylene implants. Designed methodology for wear assessment was applied on the set of thirteen extracted polyethylene hip implants. Results of the wear analysis were wear volumes and linear wear noted in the wear maps. Roughness of the surface was measured on explanted cups and results were noted in the roughness map. On articulating surface of the cups different areas were observed for measured roughness. Those areas were described as area with machining marks from manufacturing process, polished area from combination of abrasive and adhesive wear, polished area from micro-contact fatigue and area including plastic deformation.
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Friction and lubrication of fascia
Chmelík, Jiří ; Daniel, Matej (referee) ; Vrbka, Martin (advisor)
The diploma thesis was part of the project "Regeneration and lubrication of fascia with hyaluronan" of the company Contipro a.s., whose main goal is the development of an injectable medicinal product. The number of patients suffering from so-called myofascial lower back pain is increasing. The cause of the pain is increased hyaluronic acid, which is produced between the layers of the fascia. If the viscosity is low, the fascia layers are not affected and the coefficient of friction is low. The purpose of the product is to improve the sliding movement of the fascia and relieve patients of pain. The main component of the medicine is hyaluronic acid. The project included rheological and tribological analysis of hyaluronic acid samples. A tribological model of fascia in a pin-on-plate configuration was created for the analysis of the coefficient of friction. Based on the fascia models used, the dependence between the coefficient of friction and viscosity of native hyaluronic acid solutions was found. For models and real fascias, the native solution (Bonharen) was found to have better friction properties than hyaluronic acid derivatives. These analyzes have contributed not only to the development of the drug, but also to the emergence of other studies that would like to address the biotribology of fascia.
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