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Wear analysis of the sliding surface material of large-scale hydrostatic bearings
Daněk, Lukáš ; Robenek, Dětřich (referee) ; Svoboda, Petr (advisor)
This thesis focuses on the experimental investigation of the wear behavior of sliding surface materials in large-scale hydrostatic bearings during oil supply failure. The aim is to clarify the influence of materials and surface treatments on friction and wear. For this purpose, a testing methodology was designed and implemented in laboratory conditions. An experimental module was developed for the tribometer to simulate a critical state and a new procedures were established for evaluating the behavior of the contact. Wear results were observed using a profilometer, precise scales, and a microscope. A set of suitable materials for pad sliding surfaces was created, which were tested under critical conditions. The selected materials were representatives of construction steel and anticorrosion treatments (galvanization), soft and hard (aluminium) bronzes, composite bearing linings (Babbitt), polymers (UHMWPE), and composite materials (PTFE). The experimental results show the dependence of friction on sliding velocity, wear rate, and other phenomena repeatedly measured on a statistical sample of selected materials. The final result is a list of characteristics, limitations, and recommendations for the tested sliding materials, which can be used for more effective design and operation of large-scale hydrostatic bearings.
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Design of DH bike fork with magnetorheological damper
Salva, Matúš ; Robenek, Dětřich (referee) ; Strecker, Zbyněk (advisor)
When mountain biking over rough terrain, comfort and sufficient wheel pressure are often the limiting factors. That's why there is an effort to innovate suspension and develop dampers that provide better damping characteristics. The usage of semi-active suspension is one way to achieve the desired improvement over the currently used passive systems. In this work, the aim was to develop a magnetorheological damper that is suitable for implementation in commonly available mountain bike forks and whose damping characteristics allow the use of the Skyhook algorithm. A functional model of an MR damper with a stroke of 240 mm and an outer diameter of 29.5 mm, whose dynamic range is 9.5 at a piston velocity of 0.25 ms-1 and a time response of 17 ms, was developed. The magnetic circuit of the manufactured functional pattern is of 11SMn30. The damper served to verify the functionality of the concept and at the same time its damping characteristics were experimentally verified and compared with the predicted values. Due to the combination of numerical and analytical model, a very good agreement between prediction and experiment was achieved. Hence, an MR damper with a magnetic circuit made of Hiperco/Vacoflux 50 material was subsequently designed with a predicted dynamic range of 9.5 and a time response of less than 10 ms. The resulting total weight of the design is 0.68 kg. This design fully satisfies all requirements. When used in combination with semi-active control using the Skyhook algorithm, it is predicted to improve ride comfort by 28 %. The potential to use the proposed MR damper is with the increasingly widespread electric bicycles mainly due to the higher weight in conjunction. At the same time, however, the possibility of using it on a regular bicycle is not excluded. Semi-active suspension is a new and not yet widely used technology in cycling and has the potential to reach a new range of consumers. Considering all the advantages and disadvantages, it can be concluded that the proposed MR shock absorber allows to improve the rideability of mountain bikes both in terms of ride comfort, wheel traction or in the form of reduced energy expenditure during pedalling due to energy absorption by the suspension.
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Design of hydrostatic bearing for theater turntable
Foltýn, Jan ; Robenek, Dětřich (referee) ; Svoboda, Petr (advisor)
This thesis deals with the issue of hydrostatic bearings. The aim was to design a test rig for an axial hydrostatic bearing. The axial hydrostatic bearing was calculated and designed with respect to the function of the tester. The construction of the test equipment was further supported by calculations of the main parts together with FEM analyses. The design was also accompanied by an introduction to the hydraulic parts of the hydrostatic bearing, which took place in consultation with Bosch Rexroth. The aim of the work, the design of a test device in a scale of 1:10, was completed. The following results from hydrostatic bearing tests will allow the introduction of new procedures in the production of turntables mounted on a hydrostatic bearing. Examination of operating conditions and permissible assembly inaccuracies will make it possible to reduce the production requirements for bearing mounting.
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Control of hydraulic directional valves of mini excavator
Nožka, Michal ; Robenek, Dětřich (referee) ; Nevrlý, Josef (advisor)
This diploma thesis deals with the design of control algorithm for hydraulic directional control valves of a zero-emission mini excavator. Zero emission excavator have same parameters as diesel engine powered version of it. To solve this problem simulations were done for hydraulics and control algorithm of this machine. To find right parameters of simulation models, experiments have been done. There were also proposed some methods to obtain the right set of parameters. The result of this diploma thesis is control algorithm for directional control valves of this very unique mini excavator that doesn't have any competitor (in terms of control algorithm). Set of parameters was also tested during experiments.
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Design of test rig for measurement of adhesion and noise in wheel-rail contact
Gabriel, Tomáš ; Robenek, Dětřich (referee) ; Omasta, Milan (advisor)
This master’s thesis is dedicated to the design of an experimental rig that allows investigation of causes for noise during tram’s passing of a track curve and the developement of means to mitigate this noise. The opening section of this thesis contains theoretical background for the tribological mechanics of wheel-rail contact with emphasis on the process of noise generation, followed by an overview of laboratory tst rigs with similar purpose. Design itself is centered around the implementation of the dynamic model of wheel-rail contact using real tram wheel. Resulting test rig allows measurement of the adhesion characteristic in tangential and lateral directions and recording of the generated noise while an angle of attack is set.
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Design of wayside unit for top-of-rail lubrication
Valena, Martin ; Robenek, Dětřich (referee) ; Galas, Radovan (advisor)
This master’s thesis describes design and realization of a wayside unit for top-of-rail lubrication (TOR). TOR lubricant application causes wear reduction and lower noise emission. Firstly, patent analysis was provided and critically evaluated according to which requirements for developed device were specified – accurate dosage of small lubricant volume and high repeatability. On the basis of concept design, an experimental rig was created and used for lubricant application verification and spray lubrication parameter identification. Acquired results are considered in the final design of wayside unit with a technical facility. Two utility models were created within this master’s thesis.
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Adjustable portal for hydraulic pulsator Inova
Buchta, Tomáš ; Robenek, Dětřich (referee) ; Mazůrek, Ivan (advisor)
The aim of this thesis is the innovation of the testing device which is located in Institute of Machine and Industrial Design laboratory. The innovation relates to the portal construction design, where will be placed the hydraulic pulsator from the company INOVA Praha Ltd. New portal construction will be designed with respect to specified parameters and requirements and also with regard to the performed tests (damper tests, vibroizolated properties magnetorheological valves tests etc.). The thesis contains detailed analysis of the current tester and detailed analysis of similar machines with focusing on the portal structure and ways of positioning the crossmember. Further parts of the thesis is a detailed description of the design solution, including the computational simulations, attached drawing documentation and experimentally verified functional sample (crossmember).
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Mechanical design of stend for lower limbs prostheses dynamic testing
Taufer, Tomáš ; Robenek, Dětřich (referee) ; Paloušek, David (advisor)
This work describes design and realization of testing device for dynamic tests of foot prosthesis, made by methods of Rapid prototyping. Primary objective of design is to imitate the load on prosthesis during human gait. This task is accomplished by swing motion of prosthesis inside the frame of device during the loading of heel and tiptoe. Loading components can be removed and changed so the device can be used for different measurement like walking on an inclined plane. The result of this work is fully functional device including control program with many options to control the test. The result of test is to decide whether the foot prosthesis withstands the set of cyclic loads. The area of development of prosthesis by additive methods is young for the time being. It stands out especially with different materials, design, structure of prosthesis and fast process of production. Therefore this device can be used for testing of fatigue life of prosthesis made by additive methods.
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Determination of efficiency of hydraulic drive with recuperation
Kobza, Michal ; Robenek, Dětřich (referee) ; Nevrlý, Josef (advisor)
In the first part of the thesis is determined efficacy criterion for the individual operating modes of the experimental stand with energy recovery and subsequently are evaluated the records of individual measurements. Energy savings are calculated with using energy recovery. The second part describes the process of digitizing relative fuel consumption map of the engine. Results are confronted with a real application engine in the road roller Ammann AP 240 H. In addition, the master thesis describes the creation of hydrostatic converter block in the program MATLAB/Simulink 2012b. Creating block can be used in the development of simulation models.
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Design of valve block for hydrostatic recuperative module of vehicle
Ranuša, Matúš ; Robenek, Dětřich (referee) ; Nevrlý, Josef (advisor)
The Master`s Thesis deals with design and construction of a valve block for a hydrostatic recuperative module of a vehicle with a direct application on pneu tyred roller AP 240H produced by the AMMANN company. The thesis aims to analyze recovery functions of the valve block in several operating modes of the roller, followed by a selection of the right hydraulic components from the perspective of predefined parameters and pressure differences. Design specifications are based on measurements and mathematical simulations on the experimental stand. The experimental stand for this application has been developed at 1:4 scale as compared to a real vehicle. The thesis includes also design of the supporting console for the module on the frame of the vehicle. The Master`s Thesis is a part of project EUREKA with cooperation Bosch Rexroth.
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