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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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Influence of Process Parameters and Heat Treatment on the Structure and Properties of Cold Spray Method
Lindner, Patrik ; Řehořek, Lukáš (referee) ; Hutařová, Simona (advisor)
The bachelor thesis is a research of the state of knowledge focused on Cold spray technology and process parameters affecting the properties of coating, such as pressure, temperature, nozzle speed, sequence of individual layers, size of powder and others. This technology uses the kinetic energy of the impact of particles on the substrate. The main advantage of this method is possibility of forming a coating of large thicknesses (in millimeters) without oxides, with relatively low porosity and favourable mechanical properties. Aim of this work is to get acquainted with the Cold spray technology and the influence of process parameters on the quality of the spray. The influence of process parameters on properties is also demonstrated by own experimental results.
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Stabilizing systems of passenger cars
Odehnal, Jakub ; Vopařil, Jan (referee) ; Kučera, Pavel (advisor)
This Bachelor’s thesis describes basic stabilizing systems of passenger cars. These systems are correcting driving the cars and improve safety of the traffic. The main systems described in this thesis are ABS, ASR and ESP. There are also summarized some other assistant systems. In the end there is also view of various individual car companies and their theories of stabilizing of cars.
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Adhesion of bituminous binders to aggregate
Vlk, Petr ; Hýzl, Petr (referee) ; Varaus, Michal (advisor)
In 2005 the revised European standard 12697-11:2005 [1] was introduced offering a choice of three different methods. The static method described in part B has some similarities with the replaced Swiss standard for the determination of the affinity between bitumen and aggregates [2] and Czech standard for adhesions of asfalt binder to aggregates ČSN 73 6161 [3]. The result of this study is to compare the static method described in the [3] and a draft changes by Swiss research project [4] with the current revision of the European Standard 12697-11: 2005.
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Problems of the Expert Analysis of the Vehicle Movement and Braking Action in General Spatial Curve at Speed Higher than 50 km/h
Panáček, Vladimír ; Šachl, Jindřich (referee) ; Drahotský, Ivo (referee) ; Vémola, Aleš (advisor)
The present apparatus for the technical analysis of road accidents has no well-integrated information, recommendations or procedures of how to solve comprehensively the analysis of road accidents involving vehicles equipped with stabilization system of driving dynamics. The problem in the investigation of a vehicle movement in a curve is the ignorance of the contributions of vehicle dynamics intervention of the electronic stability system. Although some of the simulation software used in the analysis of road accidents makes it possible to take into account the modelled vehicle movement impacted by a stabilization system in the examined process, but the experts do not know what parameters should be entered in the numerical models of stabilization system in a computer programme. Therefore, the thesis investigates the issue of the expert analysis of vehicle riding and braking in a general spatial curve at speeds exceeding 50 kph with simultaneous examining the impact of electronic stability system chassis on vehicle driving dynamics. The thesis first deals with the solutions based on classical analytical methods, then dwells on experimental measurements in real conditions on testing grounds and, finally, addresses the use of computer simulation software in expert practice. Nevertheless, it is important to realize that no computer simulation software can be an absolutely unambiguous solver, and it is not enough to generate a computer simulation, but so obtained results should be evaluated and justified technically. Road accident analyst needs to know the impact of vehicle electronic stability control systems on vehicle movement. The thesis investigated the mutual relationship between the vehicle speed limit in a curve specified by analytical calculation and the vehicle speed in a curve experimentally detected by measuring the parameters of driving dynamics of a vehicle equipped with electronic stability system. The impact of selected electronic stability control systems of the chassis on the vehicle movement in the investigated processes in the curve was detected and quantified by driving experiments. Finally, the input values of significant quantities of computational models of the ESP simulation programs were found consistent with the results of experimental measurements in defined curves for the vehicles equipped with electronic stability systems. The results of the thesis can be used both in the expert and in the teaching activities.
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Impact of the Instantaneous Weight of Vehicles on their Stopping Distance
Motl, Jakub ; Ptáček,, Petr (referee) ; Vémola, Aleš (advisor)
This diploma thesis is engaged in analysis of braking process of vehicles, especially heavy utility vehicles, with regard to their instantaneous weight. This thesis features survey and division of braking systems and function of brakes including schemes and descriptions. Also there is introduce of some systems improving vehicle properties. Furthermore this work puts mind to possibilities of examination of brakes, measurement of braking distance and braking retardation namely in brake test rooms or by outdoor driving tests including descriptions of particular methods and equipment. There is also mention about legislative requirements for braking distance and braking retardation. The conclusion of this thesis compares numerically predicted braking distance and real braking distance measured for factual vehicle during outdoor driving test
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Performance of top-of-rail products in railway
Jordán, Tomáš ; Polach, Pavel (referee) ; Galas, Radovan (advisor)
Presented master’s thesis deals with a development of methodology of the top-of-rail products performance in railway with use of the real rail. The performance parameters are adhesion development with carry distance, carry distance, friction layer retentivity and product redistribution. The top-of-rail products are used to reduction of wear and noise pollution in railway. Currently used methodology in laboratory cause model distortion and unreal friction layer. Field experiments are affected by environmental conditions. As a main part of this thesis was developing of the methodology for the performance parameters study. The methodology was experimentally tested with four commercial products. An obtained knowledge was presented and discussed. As a part of the methodology was studied running-in of real rail. For measuring of shear friction on the top-of-rail was designed and realized a tribometer. The output of this work is functional sample of the tribometer and a manuscript dealing with the designed methodology.
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Driving dynamics of a tractor
Renza, Jaroslav ; Bradáč, Albert (referee) ; Panáček, Vladimír (advisor)
This thesis analyses driving dynamics of tractors and its dependence on their weight and age. In the beginning, brief history of tractor development and definition of basic concept of the tractor analysis is described. The thesis states procedures for obtaining magnitudes necessary for determining of driving dynamics. Experimental part describes the realized measurement on chosen sample of tractors and interprets measured values. Last part of the thesis contains evaluation of the measurement results.
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Chassis Electrical Systems
Maňák, Radim ; Janda, Marcel (referee) ; Hájek, Vítězslav (advisor)
Increasing demands onto active safety in service and passengers´s safety. This things requiring progression in technologies. In the first place electronic components were reached the greatest prosperity and improvement. Currently price electronic equipment is approximating to half price in be half car. The most important ones of safety is best quality and trouble-free operation. This project will be described splitting active safety and system integration to the unit system.
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Atomic force microscopy of soft materials
Šudáková, Anna ; Havlíková, Martina (referee) ; Smilek, Jiří (advisor)
This bachelor thesis focuses on atomic force microscopy (AFM), mainly on studying the measurement procedure and optimalization of measurement conditions with future perspective on imaging hydrogels and measuring mechanical properties (such as adhesion or stiffness) of hydrogels and semi-rigid materials at the microlevel. Atomic force microscopy is gaining significant importance in research due to its versatility, when it can provide topographical image of conductive and non-conductive samples while measuring mechanical properties of the samples, such as adhesion, elasticity or stiffness. Advantage of AFM method is that it can provide mechanical properties of the samples not only on macro levels as we are used to, for example, from rheology, but also on local level. Optimalization was performed on standard sample, one micrometre polystyrene nanoparticles , when the individual modes were measured, such as non-contact (AC Mode Imaging) mode and quantitative mode (QITM Advanced Imaging). This was followed by the measurement of a PVA foils, the measurement was performed because they are xerogels and will be studied more in the future. They were made with polyvinyl alcohol and chitosan. The internal environment of the hydrogels has been modified by adjusting the pH (NaOH) or by changing the ionic strength (NaCl). Furthermore, the effect of freezing on the PVA foils was observed, it is one of the possible ways of preparation of physically linked hydrogels. This work also examines the effect of porosity on concentration of physically linked thermoreversible agarose gels.
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