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Laser treatment of the surfaces of small human joints
Křístek, Mikuláš ; Odehnal, Lukáš (referee) ; Ranuša, Matúš (advisor)
Nowadays, in osteoarthritis of small joints, total endoprostheses are used to ensure physiological movement; unfortunately, the durability of these joint implants is very limited. The most frequent wear occurs in the contact area of the implants with the articulating surface. The use of microtextures appears to be beneficial in influencing tribological properties, but this issue is not well described. This bachelor thesis investigates the effect of different microtextures on the coefficient of friction, the movement of proteins in the synovial fluid in the contact area, wear, and the surface topography. Measurements were made using a reciprocal tribometer, optical profilometry and fluorescence observation. The textured samples achieved an increase in the coefficient of friction in the contact region. The results show that surface texturing can significantly affect the coefficient of friction in the contact region, which contributes to the reduction of wear and extension of endoprosthesis life.
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Friction and lubrication of total hip replacement produced by 3D metal printing technology
Uhrová, Simona ; Horák, Zdeněk (referee) ; Vrbka, Martin (advisor)
This thesis investigates the tribological properties of total hip replacements manufactured by both traditional and additive technologies. The primary objective is to assess the impact of different manufacturing methods on friction and lubrication at the contact between the joint head and the acetabular cup. Techniques such as a pendulum joint simulator and optical methods are utilized to analyse the lubricant film formation and friction coefficient. The findings indicate that additively manufactured implants can potentially offer comparable or superior tribological properties compared to traditional methods, potentially leading to enhanced longevity and functionality of the implants. However, the need for appropriate surface treatment and further research into wear to ensure extended life and improved implant functionality is emphasised.
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Friction of Titanium Surfaces in Implantology
Heto, Matyáš ; Odehnal, Lukáš (referee) ; Ranuša, Matúš (advisor)
This bachelor thesis focuses on the frictional properties and wear resistance of Ti6Al4V alloy. This alloy is suitable for use in orthopaedic implants such as the first metatarsophalangeal (MTP) joint in the big toe. The aim is to investigate different surface treatment methods that can reduce friction and wear of this material. The effect of applying DLC coatings and creating microtextures or microstructures on the surface is described. Metal on metal pair tests have been carried out using profilometer and tribometer in pin on plate configuration. The results show a noticeably higher coefficient of friction for the Ti6Al4V alloy than for the compared CoCrMo alloy. DLC coating significantly helped in reducing the friction and wear of Ti6Al4V. This cannot be said for the two microstructures tested, which did not have a significant effect on the observed tribological properties. The results indicate the importance of surface treatment of Ti6Al4V alloy for use in implants.
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Reducing friction losses of piston rings
Csintalan, Radoslav ; Novotný, Pavel (referee) ; Svída, David (advisor)
This diploma thesis deals with the possibilities of reducing the friction losses of the first sealing piston rings of the VW Group 1.5 TSI, 110kW engine. The first part of the thesis theoretically deals with the issue of piston rings in terms of their classification. Reduction of friction losses is ensured by PVD and PECVD coating technology. The second part of the thesis describes the production of coated piston rings. Measurements are performed on the created coatings, which are compared and evaluated in the conclusion at the end of the thesis.
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Pavement skid resistance and Skid Resistance Index
Nekulová, Pavla ; Šachlová, Zora (referee) ; Kudrna, Jan (advisor)
This diploma thesis deals with the relation between the longitudinal friction coefficient dependence on measuring speed and the value of road surface macrotexture MPD. Results of longitudinal friction coefficient and value of MPD measurement on 73 sections are included in this thesis. The results were compared by regression analysis and its outcome was used for determination of formula that enable calculation of longitudinal friction coefficient for any operating speed when longitudinal friction coefficient for 60 km/h and value of macrotexture are known. The evaluation scale for skid resistance index (SRI) was also determined in this thesis. It could be used for evaluation of skid resistance independently of the type of device used for friction coefficient measurement.
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Dependance of pavement surface skid resistance on aggregate polishing and traffic loading
Dašková, Jaroslava ; Čelko,, Ján (referee) ; Šachl,, Jindřich (referee) ; Vojtěšek, Antonín (referee) ; Kudrna, Jan (advisor)
Road safety is a complex problem. It is influenced mainly by the driver, the vehicle and the road surface. This thesis is focused on the road surface properties and especially skid resistance that directly affect the braking distance and keeping the vehicle in the horizontal curves and thus traffic accidents. The thesis deals with the durability of pavement surface skid resistance, the type of pavement layers and aggregate polishing used in wearing course. The aim of this thesis was to develop the methodology for improvement of road surfaces skid resistance durability and implementation of functional test for their assessment.
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Boundary Conditions in the Roll Gap during Hot and Cold Rolling
Luks, Tomáš ; Pernis,, Rudolf (referee) ; Hajduk, Daniel (referee) ; Horský, Jaroslav (advisor)
Boundary conditions in the roll gap play an important role in modelling of rolling processes. In the roll gap we can observe the following: changes of rolling pressure, changes of relative velocity, influences of oxides and lubrication, etc. When taking into account all conditions mentioned above the determination of the boundary conditions is not trivial and extensive measurements are necessary. Therefore, this thesis is dealing with design of temperature and force sensors specified for the determination of friction coefficient and heat transfer coefficient in contact. The temperature sensor with an installed thermocouple measures subsurface temperature for a given depth; and then the inverse heat conduction task is used to compute temperature and heat flux on the surface. Several temperature sensors were designed and used for measuring in pilot mill and industrial rolling mill as well. The thermal responses of different sensors were compared in the numerical simulations. The inverse calculations were tested for various rolling conditions. A durability of the sensors was also studied in industrial rolling conditions. The contact stresses in the roll gap were measured by a pin, which was in direct contact with the rolled material. The forces on the top of the pin were measured by a three-axes piezoelectric force transducer and recalculated to the contact stress and friction coefficient. The sensor was implemented in a work roll and tested when rolling aluminium and steel slab for different rolling conditions. The results were compared with the integrative force sensor ROLLSURF.
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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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