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Development of a New Generation of Devices with Advanced Diagnostics for Determining Contact Degradation
Dvořáček, Jiří ; Hájek, Karel (referee) ; Náhlík, Luboš (referee) ; Pazdera, Luboš (referee) ; Mazal, Pavel (advisor)
The thesis proposes a methodology for damage identification of thrust bearings using acoustic emission method. The work is the way of the hydraulic loading of specimens and thrust bearings with programmable settings severity and duration of load cycles during contact fatigue tests at stations Axmat. They are designed structural adjustment elements (waveguides) to capture the acoustic emission signal selected apparatus, including the modification of software to capture the data. At the described experiments is verified functionality of the circular test specimens and axial bearings . Part of this work is to propose a new methodology for identifying early stages of contact fatigue using a combination of diagnostic methods.
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Reversing cross for flexo printing machine
Falta, Jan ; Mazal, Pavel (referee) ; Brandejs, Jan (advisor)
The aim of this work is to develop a new concept of the reversing cross for flexo printing machine SomaFlex Optima. Work includes a description of the machine, the basic description of the principle of flexography. There is explained the principle of turning the material, the current method of supplying air to the air cushion and the difference between the blower and compressor as an air source for the air cushion. Conceptual solution includes two variants, namely vertical and horizontal position of turning bars. For each alternative are described its advantages and disadvantages.
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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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Primary Calibration of Acoustic Emission Sensors
Keprt, Jiří ; Mazal, Pavel (referee) ; Hájek, Karel (referee) ; Beneš, Petr (advisor)
The aim of the doctoral thesis is the problem of the primary calibration of acoustic emission sensor. In the introductory chapters, there are the results from the study of literature in field of AE and primary calibration of AE sensor summarized. The practical part of the thesis is aimed on realization of the primary calibration of AE sensors by different methods. The standardized methods of step function calibration and reciprocity calibration were practically realized as a part of the research on the same aparature. The method of reciprocity calibration with wideband excitation was practically realized too. The comparison between results from each used method was realized and the influences of the different sources of uncertainty and the different configuration of the calibration aparature on the step function calibration and the reciprocity calibration were determined. The uncertainties were determined for each realized methods. The recommendations for the calibration by the different methods on the available calibration aparature were presented. All the proceses of the reciprocity primary calibration was automated by the programmed software and the channel switcher. The UT 1000 (s.n. 169) by Physical Acoustic Corporation was used as the calibrated sensor for the comparison of the results of the calibrations.
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Vibration diagnostics of bearings
Navrátil, Pavel ; Mazal, Pavel (referee) ; Klapka, Milan (advisor)
This bachelor’s thesis introduces the basic principles of vibrodiagnostic methods and their importance for individual fase of bearing’s damage. The selected methods studied are: acoustic emission, SPM (shock pulse method), SEE (spectral emission energy), envelope method, High frequency emission, Crest factor, Kurtosis factor and special method for slow-motion machines Adash Compressed Time.
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Influence of Structure Directionality on Fatigue Properties of Formed Al Alloy.
Jíša, David ; Mazal, Pavel (referee) ; Liškutín, Petr (advisor)
The main goal of this diploma thesis is the examination of the influence of structure directionality on fatigue properties of formed aluminium alloy 6082/T6. The main attention is focused on the study of the influence of structure directionality on kinetics of short fatigue cracks growth. The measurement of short fatigue cracks growth was performed on cylindrical samples. The samples were made in two different directions; one parallel with the forming direction and second perpendicular to the forming direction. Servo hydraulic machine MTS 880 was used for the cyclic loading. The samples were cycled at two different constant stress amplitudes. Cyclic loading was systematically interrupted in order to measure the length of short cracks by a light microscope. Tensile tests, measuring of cycling hardening-softening curves, observation of microstructure, observation of surface relief, measuring of microhardness and fractographical analysis of fracture surfaces were used for further examination of the influence of the structure directionality. Some of these measured characteristics did not show any influence of the structure directionality (microhardness, fatigue life curve, Young modulus). In other cases is this influence measurable, however insignificant (yield stress, ultimate stress, cyclic hardening-softening curves and kinetics of short fatigue cracks growth). It can be summarised that the material, though the directionality of its microstructure is apparent, shows relatively isotropic mechanical behaviour.
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Base frame´s oil system under the steam turbine and generator
Petržela, Zdeněk ; Vlašic, František (referee) ; Mazal, Pavel (advisor)
This bachelor thesis describes problematics of the lube system of steam turbines as an important part for its operation. The beginning of the thesis offers an overview of steam engine and steam turbine development both at home and abroad and its working cycle. The main part of the thesis discusses lube system functions and components. Next section contains a summary of required turbine oil properties and effects that affect the oil during working cycle. The conclusion of the thesis is focused on lube system operating problems, their causes, consequences and recommendations for their preventing.
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Scanning of acoustic emission signal by using waveguides
Bančák, Matej ; Vlašic, František (referee) ; Mazal, Pavel (advisor)
Bachelor thesis is focused on the issue of scanning acoustic emissions from the surface of solid body and scanning with the help of acoustic waveguide placed on the solid body. The work includes the review of the present ways of scanning acoustic emissions, options of installation waveguide and propagation of waves. The practical part is focused on the experiment, which compares measured values from the surface of the test body and from the waveguide. The measurement was realized on steel of the standard quality for using a measuring instrument Dakel Xedo. The next object of this work was try to attenuate the reflected signal, which is produced by the action of force on the test body.
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