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Diagnostics of adhesion of the tram wheel using Acoustic emission method
Skoupý, Martin ; Dočkal, Aleš (referee) ; Klapka, Milan (advisor)
The aim of the thesis is to develop a method of adhesion diagnostics of a tram wheel by monitoring the acoustic emission originating from the wheel-rail contact. Application on a twin-disk test rigs is expected. The possibilities of using both contact and contactless sensors are examined. The thesis is focused on describing the response to varying speeds, angles of attack and the change of adhesion due to the application of water into the contact. RMS and energy of the acoustic emission, kurtosis or Shannon’s entropy were evaluated. It was discovered, that form the low values of the angle of attack (10 mrad) the acoustic emission RMS rises in linear manner with further increase of the angle or speed. After the application of water, the drop of the acoustic emission corresponding to the drop of adhesion coefficient was detected. The transitional states associated with unequal distribution of water were observed following its application and during the contact starvation. This can lead to an undesirable squeal noise. Another transient phenomenon manifested by the increase of acoustic emission activity was observed preceding the contact starvation, its timing corresponds to the removal of oxide layer described in the literature. Acoustic emission therefore proved to be suitable for its study and possibly for the contact starvation prediction.
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Design of a 3D print head for mixing additives into cement mixtures
Vícha, Daniel ; Dočkal, Aleš (referee) ; Škaroupka, David (advisor)
The subject of the thesis is the design of a 3D printing head for cement-composite mixtures (concretes). The device enables the addition of the basic component of the mixture by using a liquid solidification accelerator, followed by active homogenization of the mixture and dosing at the printing site. 3D printing of cementitious mixtures often leads to a loss of buckling stability of the printout. Therefore, it is necessary for the printed material to contain additives that accelerate the solidification of the mixture. However, these additives can cause clogging of the hoses when the mixture is pumped into the print head due to premature solidification. Hence, a more suitable solution is to mix these additives in the print head itself. The objective was to develop a 3D print head that allows for homogeneous mixing of the additives in the mixture, thereby eliminating complications associated with pumping. A working prototype of the print head was designed, which consists of a mixing and extrusion chamber. The mixing efficiency of this prototype was verified through numerical simulations using Particleworks. Subsequently, the prototype underwent a mixture experiment without a solidification accelerator to investigate pumpability through the printhead. Based on the numerical simulations, it was determined that the proposed prototype provides sufficient homogeneity of the solidification accelerator with the cement mixture, which should resolve the issues associated with pumping the accelerated mixture. By having a separate mixing chamber, the mixing efficiency can be controlled by adjusting the speed of the motor that drives the mixing shaft. The print head was designed to allow extrusion to be interrupted during print head passes. This was achieved by extruding the mixture into the open space of the chamber using a screw feeder. Therefore, based on the conducted experiments and numerical simulations, it can be concluded that the developed print head has the potential to enhance the quality of 3D printing of cement mixtures and eliminate the problems associated with pumping.
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Noise form rolling stock in Brno
Dolíhal, František ; Dočkal, Aleš (referee) ; Klapka, Milan (advisor)
This study is focused on the analysis of data from long-term noise measurements of trams at the turning loop in Brno-Komín, and at the Technological Park turning loop in Brno. Automated field measurement based on sound pressure level and frequency evaluated tram passages to determine if there was the occurrence of squealing noise while traversing tightly curved track segments. Concurrent with noise measurements, meteorological conditions (temperature, relative humidity, and rain) were recorded. Alongside data from the preceding switch memory, including vehicle identification numbers and inspection data provided by the Brno Public Transit Company, an analysis of influencing factors on the occurrence and parameters of squealing noise was conducted. A weak dependence on air humidity (and consequently temperature) was found. This revealed varied noise behavior among tramcars of the same construction. Influence of water in contact of wheel was described during process of drying tracks. Manual field measurements also suggest the influence of vehicle speed. Observations also indicate the need for future assessment of the driver's influence and overall driving dynamics (especially acceleration), which this study does not address.
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Analytical Methods in Motorsport
Růžička, Bronislav ; Dočkal, Aleš (referee) ; Čejka, Václav (referee) ; Karpíšek, Zdeněk (referee) ; Mazůrek, Ivan (advisor)
This dissertation is focused on proposal for simplified data analyze approach for sport-car vehicle dynamic evaluation with relationship to possibility for qualified estimation of set-up parameters influence for overall vehicle performance. In common practice can be usual overlapping effect caused by concurrent changes of car setup elements if performed in the same moment with resulting in not correct or hardly definable process determination for evaluation and decision about next steps in car development. For analyze of these multidimensional data is then chosen process with approach by Linear Regression Model (LRM). In dissertation is proposed basic philosophy with concern on specificity of car vehicle dynamics, performed experiment with defined inputs including analyze and interpretation method of obtained outputs. This methodic take into account also possibility for general application of multidimensional data analyses not only in motorsport, but as well for dynamic behavior diagnostics of technical systems where finding of optimal running condition depends on multi-parametric setup whose combination must reflect often changes of outer conditions too.
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The study of magnetorheological shaft seal
Pavlíček, Dušan ; Dočkal, Aleš (referee) ; Kubík, Michal (advisor)
This thesis deals with the experimental study of magnetorheological shaft seal. The purpose of this diploma thesis is to describe the operating parameters of rotational magnetoreological shaft seal. In thesis, the effects of magnetic field and shaft speed on the pressure resistance and braking torque are described. Operating parameters were measured by an experimental device. Research has shown that the magnetoreological seal is characterized by a high pressure resistant. Disadvantages are the high braking torque and leakage of carrier oil from the magnetorheological fluid. These problems have been solved by a new design of magnetic circuit, that has been identified as a magnetoreological gradient pinch seal (MRGPS).
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Reconstruction of Gearbox Testing Rig
Rozsypálek, Tomáš ; Dočkal, Aleš (referee) ; Klapka, Milan (advisor)
The aim of this diploma thesis is reconstruction of gearbox testing rig. Modernization will allow fully automatic long-term gearbox tests according to pre-defined test parameters. The first part of thesis describes commercial and scientific solutions of used testing rigs. Individual solutions are inspected and evaluated for applicability to upgrade the testing rig. The second part of diploma thesis deals with selection of purchased components for allowing automatic drive, design concepts, selection of appropriate design, assembly and installation of control board and calibration of used components. This part of diploma thesis deals with analysing of software solution made for automatic drive too. The output of this work is a functional sample of control hardware and software for automatic and manual control which contains recording of measured data.
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Construction of comparison measuregauge for measurement of tools.
Brabenec, Petr ; Dočkal, Aleš (referee) ; Ždímal, Pavel (advisor)
This work is about construction of a comparison gauge to meausure revolving tools. The gauge measures cutting and clamping parts of standard and special reamers. The gauge is unique and is designed for a company manufacturing concerete. It was designed in accordance with requirements and a prototype was tested for functionality. There is made analysis, development, design, theoretic estimation and practical verification of accurancy.
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Modernization of R-mat test stations
Papaj, Lukáš ; Dočkal, Aleš (referee) ; Mazal, Pavel (advisor)
The aim of the thesis is to reconstruct obsolete R-mat test stations, which are used for rolling contact fatigue tests of material, which are still of interest from industry. It was necessary to replace the original control electronics with a new industrial computer to allow use modern sensors and automate the entire test process. At the same time, the measurement was supplemented by an acoustic emission method, which can also record the development of damage. Design modifications have been made that allow the installation of all new sensors. The main method for evaluating the tests is vibrodiagnostics, which is supplemented by the acoustic emission method. With the help of several experiments, the shortcomings of the new control system were identified, some parameters were designed, and the main functionality of the modernized R-mat station was verified. According to the proposed parameters and the identified shortcomings, the control system was modified, and a script was created, which is used to evaluate the test. It is still possible to perform rolling contact fatigue tests of the material on the modernized equipment, and thanks to the modernization of the electronics, it is possible to test completely new methods of test evaluation.
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Design automation of simple inject moulds for tool factory
Žváček, Michal ; Dočkal, Aleš (referee) ; Paloušek, David (advisor)
The dissertation is concerned with automatization proposal of simple injection moulds for plastics. The dissertation is concentrating on the process of CAD design with the aim of make it more effective and automate by the help of 3D parametric strickle board of moulds. It serves for rapid proposal of basic mechanism of the tools. Strickle board of the mould is managed by length of side moulding plate in required range from 300 to the 700mm. For managing of standardized parts was created web portal, which includes database of single parts. These parts can be simply insert to the groups of moulds by the help of hypertext links in software Catia V5. Dissertation includes description of whole system automatization and matching of the new way of CAD design with the original.
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Experimental chamber for testing of special materials using SLM technology
Malý, Martin ; Dočkal, Aleš (referee) ; Koutný, Daniel (advisor)
The thesis deals with the influence of process temperature and pressure on 3D printing using Selective Laser Melting. The aim of the thesis is the design, manufacture and testing of the experimental chamber for SLM 280HL from company SLM Solutions. The main task of the experimental chamber is to increase the temperature of the preheating of the powder bed from the original 200 °C to at least at 400 °C. The device will be used to investigate the influence of high process temperature on the properties of printed materials. The thesis also deals with the design of the powder applicator for elevated temperatures.
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