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Impact of joint implant surface structure on friction behaviour
Kučera, Ondřej ; Nečas, David (referee) ; Ranuša, Matúš (advisor)
In osteoarthritis of small joints, the use of total endoprosthesis is currently being developed to ensure physiological movement, but it provides only a limited-service life. The use of microstructures on the implant surface may improve tribological properties, but this issue is not described enough. Thus, this work addresses the impact of microstructures on friction coefficient, lubricant thickness in the contact area, wear, as well as surface topography and geometry of the structures. Furthermore, the influence of DLyte electrochemical machining on the change of microstructures geometry and tribological properties is investigated. Measurements were performed using a reciprocal tribometer, interferometry and optical profilometry. The textured samples achieved an increase in both friction coefficient and lubricant thickness in the contact area. Furthermore, a correlation between the height of the texture edges and the measured lubricant thickness was demonstrated. DLyte significantly reduces these edges, also reducing wear, however, it degrades the surface of the CoCrMo samples. Implant texturing can lead to reduced wear, prolonged life, and thus improved quality of life for many patients. Texturing of Ti6Al4V alloy in combination with DLyte shows great potential.
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Friction analysis of hip joint replacements with coated surface
Nosek, Matěj ; Streďanská, Alexandra (referee) ; Nečas, David (advisor)
This bachelor thesis focuses on the effect that results from applying a coating to hip joint replacement based on the friction coefficient. The aim of this thesis was to conclude a comparison between individual combinations with and without coating in three types of fluids. Experimental measurements were conducted in configuration ball-on-head in a pendulum hip joint simulator. For these measurements, DEWEsoft, MATLAB, and MS Excel were used. During the measurements, four balls, two cups, and three fluids were used. The coating is a polymer-based solution made out of PEGMA-360 a PEGDMA-550. With the usage of the coating, gathered results point out that the coefficient of friction declines by a maximum of 5,4 % and increases by a maximum of 16,1 % compared to those without any coating. Results presented by this thesis may be in the service of further research of coatings and their application on hip joint replacement, which might increase the potency of those implants.
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Design of a test condition for determining the wear at the contact of a railway wheel and rail
Rec, Matouš ; Prokop, Aleš (referee) ; Řehák, Kamil (advisor)
This diploma thesis focuses on the issue of a wear of a railway wheel and a rail. The wear of the components depends on a number of parameters including the contact stress, the contact pressure and the contact surface dimensions. Among the factors determining these parameters belongs primarily the wheel driving gauge, the rail profile and the load of the contact area. Furthermore, the material from which the wheels and rail are made, the roughness and hardness of the functional surfaces and the residual stress in the material have a significant impact on the wear. All the parameters mentioned above are designed for the production of the railway wheels and rails and therefore they meet the standards for the production of these components. However, the existence of the changeable parameters has also a significant impact on the wear. These parameters include the presence of contaminants, or lubricants in contact, the changing driving gauge due to the wear, the slip ratio or the friction coefficient. With the wear being an inevitable process during the application it cannot be eliminated but only controlled. Applying the lubricant into the contact when passing through the arc in order to achieve an ideal coefficient or the maintenance grinding for restoring the driving gauge can serve the purpose. If properly optimized, the importance of the wear research lies in the financial savings. Being the crucial factor for optimization of the intervals between the maintenance grinding, the research is also beneficial. A high-quality wear prediction can be seen as the key field in order to increase the safety of the railway vehicles operation as well. Therefore, the wear research is made using several methods, such as the computational models, the multi-body dynamics software and the technical experiments. This thesis introduces a conceptual design of the test, enabling the wear research via experimental approach. The final device is capable of a simulation of both volume and fatigue wear during the states the railway wheel and railway undergo including riding on the straight track, passing through an arc or a wheel slip during braking.
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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.
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Friction coefficient analysis of the turbocharger bypass valve
Wolf, Juraj ; Spáčil, Tomáš (referee) ; Krejčí, Petr (advisor)
Aim of the diploma thesis is set to present a new method for evaluation of the friction coefficient of the wastegate valve system. A test fixture was designed and manufactured for this purpose. Simulations in ANSYS and MSC Adams support test results. The developed method provides an accurate and affordable solution for investigating of friction coefficient for various valves of turbochargers wastegate.
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Complete characterization of the ceramic-based hot-coated coating on the AZ91 magnesium alloy
Plevová, Kateřina ; Doskočil, Leoš (referee) ; Wasserbauer, Jaromír (advisor)
The diploma thesis is focused on the study of the thermal sprayed coating consisting of the NiCrAlY alloy bond layer and the partially stabilized zirconium oxide (8YSZ) top layer on the AZ91 magnesium alloy. The theoretical part deals with the structure of the alloy AZ91, NiCrAlY and partially stabilized zirconia. Furthermore, the methods of thermal spraying and the function and properties of thermal barrier coatings are summarized. The experimental part deals with the characterization of the thermal sprayed coating and the AZ91 alloy in terms of elemental, structural and phase composition. Optical and electron microscopy, EDS and XRD analysis were used for characterization. Electrochemical properties were investigated in~3.5% sodium chloride solution by potentiodynamic polarization. The mechanical properties (hardness, coefficient of friction) of the substrate and coating were measured using a hardness tester and tribological tests.
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Dynamic vehicle-road interaction
Svršek, David ; Blaťák, Ondřej (referee) ; Fojtášek, Jan (advisor)
Bachelor’s thesis, Dynamic vehicle-road interaction, deals with a summary of basic knowledge about the acting force and factors that affect interaction of vehicle with surface. The work is divided into six parts, which deals with the definition of basic concepts and characteristics of dynamics, traction vehicle, braking, maneuverability, the chassis aspects influencing the traction and anti-skid road surface properties.
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