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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.
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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 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.
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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.
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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.
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The effect of viscoelasticity and operating conditions on friction of compliant contacts
Quinn, Cheney ; Daniel, Matej (referee) ; Nečas, David (advisor)
Poddajné kontakty obsahující polymerní nebo pryžové členy lze nalézt v technických i biologických aplikacích. I přes vývoj v této oblasti existují efekty, které ovlivňují tribologické aspekty těchto kontaktů, a je třeba je dále zkoumat. Tato práce se zabývá vlivy kinematických podmínek, konfigurace, viskoelasticity a viskozity maziva na tření v mazaných poddajných kontaktech. Výsledky byly použity k vývoji numerického modelu pro predikci kapalinového tření v poddajných kontaktech. K objasnění chování poddajných kontaktů bylo použito zařízení Mini Traction Machine (MTM) v konfiguraci ball-on-disc, což umožnilo zkoumání zmíněných vlivů. Z poznatků z technické oblasti bylo zjištěno, že viskoelasticita se projevuje ve všech konfiguracích, tedy soft-on-hard, hard-on-soft a soft-on-soft, a její efekt je nejvýznamnější v konfiguracích s poddajným diskem. Data dále ukazují, že poměr skluzu a valení má vliv na valivé tření což je v rozporu se současnou literaturou. Výsledky z biologické oblasti naznačují, že za určitých podmínek lze nahradit nativní kapalinu jednoduchým mazivem. Tyto poznatky mohou posloužit jako odrazový můstek pro další studie zabývající se poddajnými kontakty.
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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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An experimental investigation of friction coefficient in hip joint replacements
Tkadlec, Tadeáš ; Urban, Filip (referee) ; Nečas, David (advisor)
This bachelor thesis deals with an experimental analysis of friction coefficient within hip joint replacements. The measurements were realized on Mini Traction Machine device in ball-on-disc configuration. The main goal was to determine the effect of implant material, kinematic conditions and model synovial fluid composition on the development of coefficient of friction as a function of time. For this purpose, three different materials (metal, ceramic, polymer), two mean speeds (5.7 mm/s; 22m/s), three different slide-to-roll ratios (SRR = 0 %, SRR = -150 %; SRR = 150 %) and six various model fluids containing albumin and -globulin in a various ratios and concentrations were employed. The results are evaluated in the form of graphs showing the dependence of friction coefficient on time and are confronted with previously published studies.
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Thermal analysis of plastic part using finite element method
Zemanová, Lucie ; Nečas, David (referee) ; Zatočilová, Aneta (advisor)
The bachelor thesis deals with the thermal deformation of a plastic component after thermal loading and ways of processing digital data for a thermal analysis. There is optical digitizing outlined, since input data were obtained this way, and methods of subsequent processing for the thermal analysis. The analysis is carried out by the finite element method using ANSYS Workbench software. The finite element method is described. The work builds on measuring performed by photogrammetry, the aim is to compare applicability finite element method and photogrammetry for measuring deformation.
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The Effect of Synovial Fluid Constituents on Lubrication of Hip Joint Replacements
Nečas, David ; Daniel,, Matej (referee) ; Sawae, Yoshinori (referee) ; Hartl, Martin (advisor)
Dizertační práce se zabývá mechanismy mazání v náhradách kyčelního kloubu. Byla provedena systematická studie formování proteinového filmu při zahrnutí různých materiálů a provozních podmínek. Hlavní pozornost je přitom věnována roli jednotlivých proteinů obsažených v synoviální kapalině při současné přítomnosti dalších proteinů. Jelikož metody aplikované v předchozích studiích neumožňovaly separovat jednotlivé složky maziva, byla vyvinuta optická měřící metoda na principu fluorescenční mikroskopie. Z důvodu verifikace metody byly provedeny dvě nezávislé studie zaměřené na měření tloušťky mazacího filmu a dělení maziva na výstupu mazaného kontaktu. Z důvodu určitých limitací fluorescenční mikroskopie byla dále využita i metoda optické interferometrie, jejíž využití je ilustrováno ve studii zabývající se formováním mazacího filmu v náhradách kyčelního klubu při uvažování reálné konformity třecích povrchů. Závěrečná část práce představuje nový metodologický přístup založený na in situ pozorování kontaktní oblasti umožňující popsat roli jednotlivých proteinů ve vztahu k vývoji tloušťky mazacího filmu. Práce obsahuje originální výsledky, které přináší nové poznání v oblasti biotribologie náhrad kyčelního kloubu vedoucí k dalšímu vývoji implantátů při snaze zabránit jejich selhání v důsledku omezené životnosti.
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