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The measurement and analysis of dynamic load applied on railway switches
Růžková, Jitka ; Pazdera, Luboš (referee) ; Smutný, Jaroslav (advisor)
This bachelor's thesis deals with suggestion method to measurement, aplication this method of the real measurement and evaluation. The theoretical part contains basic informations about dynamic effects of wheel impacts and vibrations. The measurement procedur is described the two crossings of the same type constructions (monoblock crossing with the running surfaces explosive hardened) with different fastening (elastic rail fastening and fastening rail system). The practical part contains an analysis which is made in time and frequency. The point of thesis is verification of the function elastic fastening crossing in switches in comparison with rail fastening.
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High Speed Milling of Aluminum Alloys for Aircraft Industry
Pazdera, Lukáš ; Polzer, Aleš (referee) ; Píška, Miroslav (advisor)
The aim of this paper is a complex analysis of the high speed cutting in the aircraft industry. The paper studies especially the machining of aluminum alloys, which are characterized in the first part. We can find in next chapters a view on the high speed cutting from aspect of the chip formation, the force load and the machined surface roughness. The end of the paper is focused on the issues of the CNC, machining of typical aircraft shapes and description of roughing paths, which increase the productivity.
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Evaluation of Cyclic Damage in Aluminum and Magnesium Alloys Using Acoustic Emission Technique
Vlašic, František ; Samek,, Jiří (referee) ; Fiala, Jaroslav (referee) ; Pazdera, Luboš (referee) ; Mazal, Pavel (advisor)
The thesis deals with the application of nondestructive testing methods (acoustic emission, electron microscopy, X-ray diffraction topography) to description and identification of stages in the fatigue process in aluminium alloys. The main contribution of this dissertation thesis consists of the approach and evaluation methodology of cyclic damage in the materials. It dealt especially with the verification of measured data by using data obtained using other nondestructive methods. The experimental results show that the field of nondestructive testing materials can fundamentally uncover the process of fatigue damage and improve current knowledge in this area. Combination of used methods has become a powerful tool for the identification and monitoring of the whole fatigue degradation process of materials.
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Experimentální analýza vybraných železničních konstrukcí
Nohál, Viktor ; Pazdera, Luboš (referee) ; Tomandl, Vladimír (referee) ; Smutný, Jaroslav (advisor)
The thesis is focused on the possibility of using data from the measurement dynamic effects on the track structure to determine the condition of the underfilling track structure. Next, the thesis focuses on the analysis of the obtained signal and the determination of the position of the wheelsets in the measured signal. The wheelsets are an exciter of the dynamic response to the track structure, so for many applications, it is necessary to know the position of this excitation. As a secondary result of the analyses, can be obtained information about the technical condition of the wheelset, and can be also inferred other characteristics. We can divide into cargo sets vs. passenger, and between passenger sets, we can distinguish whether it is an electric unit, a locomotive with passenger cars, whether the train is pulled by a locomotive, or a control car is positioned at the front of the train and the set with a locomotive at the back is driven by a spur, etc. Measuring in the field on a railway structure is often expensive, not only from the point of view of the equipment but also for securing human resources. Therefore, the goal is to create a cheap autonomous device that would not be difficult to install and would provide the necessary data about railway vehicles and railway construction. The developed autonomous module for measuring vibrations can provide this data, and based on it, it can subsequently be evaluated whether the structure was loaded by an individual railway car or an entire train set, which train set it was, how many cars the given set consisted of, how fast it was and other useful things information. Determining the speed of the train set and identifying the axles of the individual cars of this set is a basic task that must be solved before it is possible to proceed with further data processing. The measurement of the acceleration of oscillations on the railway structure (i.e. vibrations) is carried out to determine the dynamic response of the structure to the passage of the train set and to determine the behaviour of the railway structure. Determining the individual axles of the train set is only an intermediate step to performing further analyses. The dynamic response signal of the train set is not directly intended for axle identification, however, by solving the axle identification from this signal, it was possible to greatly simplify and reduce the cost of the entire measuring system. So, it is not necessary to include another module in the assembly, which would be focused only on the identification of the axle and, in addition, would increase the price of the entire system and the perspective of its complexity (also from the subsequent installation on the track). Determining the speed of the train set and the position of the individual wheels in the measured signal is a good starting point for performing subsequent analyzes of the state of underfilling of the rail grid and the behaviour of the railway structure over time. Due to the smaller diversity of the vehicle fleet for passenger transport and also due to the smaller dispersion of the possible load from individual railway wagons, it is recommended to use only the load from the travel of the passenger train for the assessment of the condition of the railway structure in long-term measurements. Therefore, in the final phase, this work also deals with the issue of determining the type of train set.
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The application of low noise barriers in SŽ conditions
Slepánková, Aneta ; Pazdera, Luboš (referee) ; Smutný, Jaroslav (advisor)
The main aim of my bachelor thesis was to describe the problem of noise spread and its further reduction by low noise barriers in rail transport. A partial aim was to analyse the given issue and to investigate individual possibilities in the Czech Republic and abroad. The following step was to build a suitable acoustic model for the selected location and simulate the acoustic situation with different types of low noise barriers. An important part of the thesis is to summarise the results and suggest possible solutions for the Railway Administration.
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Komplexní metodika pro nedestruktivní a šetrnou semidestruktivní diagnostiku fyzikálně-mechanických vlastností historických pálených zdících prvků
Cikrle, Petr ; Sokolář, Radomír ; Topolář, Luboš ; Pazdera, Libor ; Anton, Ondřej
Uvedená metodika popisuje základní principy a způsob provádění a vyhodnocování zkoušek zdících prvků určených primárně jako náhrada či doplnění stávajícího historického zdiva. Metodika je určena především pro výběr lícových cihel, které musí mít určité specifické vlastnosti, závislé na prostředí jejich aplikace. Tato metodika je aplikovatelná jak na cihlách starých (použitých, získaných ze zbouraných konstrukcí), tak na nových vyrobených v cihelně, ať už se jedná o běžnou produkci nebo speciálně vyráběné repliky historických cihel. Metodika využívá rozsáhlý soubor zkušebních metod, které však nemusí být vždy v celé šíři využity v závislosti na konkrétních požadavcích na zdící prvky. Novost postupu metodiky spočívá v komplexním zapojení zcela nedestruktivních elektroakustických metod – metody impact-echo, metody rezonanční a metody ultrazvukové impulzové, které posouvají tradiční třídění na výrazně vyšší úroveň. Díky zapojení nedestruktivních zkoušek, jejichž provedení je relativně jednoduché a časově nenáročné, přičemž výsledky jsou u většiny z nich okamžitě viditelné v reálném čase, umožňuje tato metodika provést kvalifikovaný předvýběr souborů cihel vhodných pro náhradu historického zdiva a následně u vybraných souborů provést jejich efektivní třídění a vzorkování, včetně výběru zkušebních vzorků pro ověření fyzikálně-mechanických vlastností cihel tradičními laboratorními metodami. Díky řadě provedených srovnávacích zkoušek (nedestruktivní × destruktivní) na souborech různých cihel z různých období je dokonce možné částečně predikovat trvanlivost (mrazuvzdornost) cihel a provést jejich základní roztřídění do skupin: 1) vhodné pro použití, 2) diskutabilní, 3) zcela nevhodné. Uvedené nedestruktivní zkoušky však mají značný význam i pro posouzení nových cihel, např. pro odhalení textury, která je jednou z hlavních příčin snížené mrazuvzdornosti cihel. Rovněž lze pomocí těchto metod provést třídění cihel přímo ve výrobně (zejména v případě starších typů pecí, kde je poměrně velká variabilita vypálených cihel). V neposlední řadě lze odhalit případnou dodávku špatných (nekvalitních) cihel a zabránit jejich zabudování do stavby. Metodika byla ověřena nejen prostřednictvím velkého množství laboratorních zkoušek cihel různého stáří (cihly gotické, renesanční, barokní, novodobé z 19. století a současné), ale rovněž přímo in situ v rámci rekonstrukce unikátní technické památky – barokního mostu Portz Insel u Mikulova, kde byla přímo aplikována pro výběr náhradních cihel určených pro obnovu chybějících částí mostu (původních barokních, nově vyráběných i použitých ze zbouraných staveb).
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Reproductive senescence in female barn swallows (Hirundo rustica): age-related changes in components of reproductive success
Pazdera, Lukáš ; Tomášek, Oldřich (advisor) ; Riegert, Jan (referee)
The effect of age on an individual's fitness is one of the key topics of evolution ecology. Currently intensively studied manifestation of age is an aging of organism, thus a deterioration of metabolic functions and condition with age. An increasing count of studies shows that aging in the wild is rather a rule than exception, even with short-lived species of which the aging has not been previously presumed at all. Despite an increasing interest of evolution ecologists in this matter, some important aspects remain overlooked. Senescence of the traits are usually studied separately, therefore, an information whether an individual traits show similar or different aging dynamics is missing. The information is needed to assess if the signs are aging synchronously, as predicted by the William's antagonistic pleiotropy theory, or rather asynchronously. The suitable traits for study are these, which are involved in a reproduction activity. The reproduction is a sequential process consisting of many components, e.g. an expression of sexual ornaments (attractivity), nesting timing, amount of eggs laid and their size, etc. There is currently a little knowledge of which of these reproduction components are affected by the aging the most, and which are resistant to the the effect of age. Well studied is...
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Reproductive senescence in female barn swallows (Hirundo rustica): age-related changes in components of reproductive success
Pazdera, Lukáš ; Tomášek, Oldřich (advisor) ; Riegert, Jan (referee)
The effect of age on an individual's fitness is one of the key topics of evolution ecology. Currently intensively studied manifestation of age is an aging of organism, thus a deterioration of metabolic functions and condition with age. An increasing count of studies shows that aging in the wild is rather a rule than exception, even with short-lived species of which the aging has not been previously presumed at all. Despite an increasing interest of evolution ecologists in this matter, some important aspects remain overlooked. Senescence of the traits are usually studied separately, therefore, an information whether an individual traits show similar or different aging dynamics is missing. The information is needed to assess if the signs are aging synchronously, as predicted by the William's antagonistic pleiotropy theory, or rather asynchronously. The suitable traits for study are these, which are involved in a reproduction activity. The reproduction is a sequential process consisting of many components, e.g. an expression of sexual ornaments (attractivity), nesting timing, amount of eggs laid and their size, etc. There is currently a little knowledge of which of these reproduction components are affected by the aging the most, and which are resistant to the the effect of age. Well studied is...
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The analysis of dynamic effects in the frog region of railway turnout
Balash, Arsen ; Pazdera, Luboš (referee) ; Smutný, Jaroslav (advisor)
This thesis is focused on measurement and analysis of dynamic effects on railway turnouts. Two same-type turnouts with different fastening elasticity were chosen. My attention was focused mainly on the crossing part of the turnout, where the highest dynamic impacts occur. The point of the thesis is comparison of the crossing part of turnouts in term of dynamic behaviour and assessment of influence of soft rail pads on spread of dynamic energy through the construction. A part of the thesis is choice of methodology of the measurement and proposal of convenient mathematical apparatus for analysing of the dynamic effects on crossings.
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Evaluation of the rail pad stiffness
Šardická, Klára ; Pazdera, Luboš (referee) ; Smutný, Jaroslav (advisor)
Rail pads are part of baseplate and baseplateless fastening system. It is a flexible element that is used primarily to reduce the negative effects of dynamic stress, reduce noise and vibration. This thesis deals with laboratory measurement of low-frequency dynamic stiffness at 5 Hz, static stiffness according to ČSN and static stiffness according to OTP of rail pads. The aim is to carry out and evaluate the measurements of samples supplied by different manufacturers and to compare them according to the variance of the resulting stiffnesses. Evaluate the stiffness of used rubber pads and compare with the results of new samples. Further, this thesis deals with the factors that the measurement itself and its results could influence.
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