|
|
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.
|
|
|
The effect of surface condition of artificial joint cup on the friction coefficient
Černohlávek, Mikuláš ; Dočkal, Kryštof (referee) ; Nečas, David (advisor)
This bachelor’s thesis deals with the effect of microtextured surface of an artificial joint cup on a friction coefficient. The primary aim of this thesis was to compare friction coefficients of original and microtextured joint cups. Experimental measurements were made on pendulum hip joint simulator and results were evaluated in Matlab. Four types of femoral heads (CoCrMo, BIOLOX Delta, BIOLOX Forte and oxinium) and three types of lubricants (PBS, model synovial fluid and hyaluronic acid solution) were used during the measurements. The results show, that using PBS and synovial fluid leads to decrease of the coefficient of friction while using modified joint cup. We can assume that microtextured surface of artificial joint cup (separately or in combination with microtextured femoral head) could be a significant benefit for prolonging lifespan of implants.
|
|
|
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.
|
|
|
Lubricants created by nature
Drobilič, Ivo ; Urban, Filip (referee) ; Nečas, David (advisor)
This bachelor thesis provides an overview of substances which can be considered as the lubricants in its natural environment. The first part of the thesis of focused on lubricants in human body. The substances such as water, blood or synovial fluid are analysed in a detail. The following chapter deals with lubricants in everyday life. As the example, decrease of tyre adhesion in case of rain or longer breaking distance of trains as a consequence of presence of leafs on rails, can be mentioned. The last part, in addition, summarizes the lubricants which are based on natural products.
|
|
|
Biotribology of articular cartilage
Furmann, Denis ; Látal, Roman (referee) ; Nečas, David (advisor)
This bachelor thesis deals with biotribology of articular cartilage. The first part deals with the analysis of individual building components of cartilage. Another part is devoted to the definition of the tribological properties of cartilage with regard to friction, wear and lubrication. The thesis also briefly analyses selected publications dealing with articular cartilage biotribology. Two hypotheses have been formulated and verified on the basis of the processed articles. Will the friction coefficient fall at a higher load? Will the friction coefficient increase at higher speed? It has been experimentally confirmed that the friction coefficient value increases with increasing speed and decreasing load.
|
|
|
The effect of synovial fluid composition on friction of joint cartilage
Furmann, Denis ; Daniel, Matej (referee) ; Nečas, David (advisor)
This thesis deals with the study of the effect of the constituents of the model synovial fluid on the frictional properties of articular cartilage. The influence of constituents, concentration, speed and load is observed. Experiments were performed on a commercial tribometer at configuration pin-on-plate. Several types of lubricants containing synovial fluid constituents have been selected for the experiments. Lubricants were prepared at two concentrations, the concentration of healthy individuals and at a concentration typical of for osteoarthritic patients. Speeds 5 and 10 mm/s and 5 and 10 N loads were used for all experiments. It is shown that when using only lubricant containing proteins, no difference in the coefficient of friction is observed and the effect of concentration is also not observed. The addition of hyaluronic acid has a synergistic effect with -globulin, however in the case of lubricants containing albumin, the effect is opposite. After the addition of phospholipids, no significant effect on friction is observed in -globulin containing lubricants. No significant effect of the composition and concentration of the lubricants is observed with the load change.
|
|
|
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.
|
|
|
Design of adaptive wiper of liquids
Novotný, Antonín ; Nečas, David (referee) ; Košťál, David (advisor)
This thesis deals with the structural design of the adaptive fluid wiper, which is the complement of laboratory equipment. Laboratory equipment is used to study the thickness of the lubricating layer and the frictional force at contact. The purpose of the adaptive wiper is to remove the maximum amount of liquid from a moving planar disc or to make a uniform film in a rolling path around the periphery of the disc. Among the most controllable features, there are the wiper geometry, the evenly pressing and the follow the disc throwing. The thesis includes the design report, drawings and 3D model.
|
|
|
Experimental analysis of lubricant film formation in hip joint replacements
Švachová, Michaela ; Dzimko, Marián (referee) ; Nečas, David (advisor)
This diploma thesis deals with an experimental analysis of lubricant film formation in hip joint replacements. The main objective is to clarify the effect of mean speed, slide-to-roll ratio, and material of femoral head on the development of film thickness, focusing on the role of particular constituents contained in model synovial fluid, such as albumin and -globulin. For this purpose, a model ball-on-disc configuration was applied, while the development of lubricant film was evaluated using the combination of fluorescent microscopy and optical interferometry. To better understand the process, coefficient of friction between implant surfaces was later investigated as well. The effect of material, slide-to-roll ratio, mean speed and model fluid composition was analysed. Results indicate that the main parameter, influencing the character of film formation, is slide-to-roll ratio. Under most conditions, the dominant constituent responsible for the film thickness development was albumin. Coefficient of friction is affected mainly by the material of implant. The thesis contains original scientific results extending the knowledge in the area of hip joint biotribology.
|
|
|
Thin metal coating of polymer materials
Zatloukal, Filip ; Furmann, Denis (referee) ; Nečas, David (advisor)
The study of compliant contacts from a tribological standpoint is very complicated due to low reflectivity and electrical conductivity of materials such as polymers or rubber. These properties significantly limit the possibilities of using conventional methods which are being used to study the film formation and lubricant flow. To enable the use of the conventional methods it is necessary to apply a thin reflective layer on the non-reflective surface. This work evaluates the current literature dealing with the coating of polymeric materials. A method was chosen based on the analysis of the currently available technologies, which is used to apply a thin reflective layer on the polydimethylsiloxane sample. This part is followed by a feasibility study to clarify the effects of the coating on friction processes. This work can significantly contribute to the field of compliant contacts, especially in terms of clarifying the mechanisms of lubrication.
|
guest ::
RSS feed.