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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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Experimental Study of the Efect of Lubricants on Rolling Contact Life
Šembera, Václav ; Ficza, Ildikó (referee) ; Nohál, Libor (advisor)
The aim of this bachelor’s thesis is to summarize the art of state in the area of the contact fatigue, lubricants and detection of the rolling contact fatigue exploiting the acoustic emission method. In the experimental part of this bachelor’s thesis are performed the rolling contact testing for the standard grease and the lubricant with EP additives by marginal exploiting the acoustic emission method. The effect of the lubricants on the rolling contact life is evaluated by basic rating life L10 stated by using Weibull distribution.
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Reconstruction of AXMAT Testing Station
Gergel, Matej ; Dobeš, Petr (referee) ; Dvořáček, Jiří (advisor)
The master´s thesis deals with reconstruction of RCF test rig AXMAT. Main goal is design new hydraulic load system and his realization. The first part of thesis describes similar experimental machines and their pros and cons. This analysis is base for complete reconstruciton of AXMAT. New hydraulic load system allows dynamic programmable load cycles. Control system with close loop and feedback was created in software Matlab – Simulink. Main frame was reconstructed too. Control and action parts were asseble to station. Output of thesis is function sample.
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Influence of topography of rubbing surfaces on rolling contact fatigue
Zahradník, Radek ; Čermák, Jan (referee) ; Vrbka, Martin (advisor)
This master thesis deals with influence of topography of friction surfaces on rolling contact fatigue. This influence is examined by newly reconstructed R-MAT station, whose reconstruction and fully report about it, is part of this master thesis. Influence is examined on area with higher surface's roughness which it wasn't examined before. Further research is made on area of surfaces with topographical modification with higher surface's roughness.
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Correlation of AE Signal Changes to Rolling Contact Damage Propagation
Nohál, Libor ; Čermák, Jan (referee) ; Hájek, Karel (referee) ; Hutař, Pavel (referee) ; Mazal, Pavel (advisor)
This PhD thesis deals with the experimental study of more precise rolling contact fatigue damage detection using acoustic emission method. A series of experiments was carried out on two representatives bearing steels and the analysis of sensitivity for the presence of contact damage was performed on selected parameters of acoustic emission. The extent of damage was classified into four classes and signal parameters the most characterizing the development of damage were correlated with the extent of damage. It was also verified the influence of lubricants on acoustic emission signals. The results have an impact on the implementation of more precise rolling contact fatigue tests and evaluation of parameters of acoustic emission signal. On the basis of experiments was established methodology for more precise RCF testing method using acoustic emission on test-rig AXMAT II.
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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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Condition monitoring of thrust ball bearings using continuous AE
Chlada, Milan ; Nohal, L. ; Převorovský, Zdeněk
Fast and reliable analysis of continuous AE recorded during endurance tests on flat washer parts reliably simulating critical rolling contact fatigue of the full-scale bearings is presented in the paper. Two channels of continuous AE signal were partially recorded within whole specimen lifetime tests and compared with other experimental parameters as vibration rate or temperature. As an alternative to classical spectrogram analysis, we proposed to use histograms of time intervals between threshold amplitudes crossings in various frequency bands represented by the wavelet decomposition. Results obtained on long-time records are discussed, illustrating advantages of proposed AE signal processing, which can be done in real time to observe the processes before the onset of the final damage on the surface of the specimen more precisely than vibrodiagnostics.
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Correlation of AE Signal Changes to Rolling Contact Damage Propagation
Nohál, Libor ; Čermák, Jan (referee) ; Hájek, Karel (referee) ; Hutař, Pavel (referee) ; Mazal, Pavel (advisor)
This PhD thesis deals with the experimental study of more precise rolling contact fatigue damage detection using acoustic emission method. A series of experiments was carried out on two representatives bearing steels and the analysis of sensitivity for the presence of contact damage was performed on selected parameters of acoustic emission. The extent of damage was classified into four classes and signal parameters the most characterizing the development of damage were correlated with the extent of damage. It was also verified the influence of lubricants on acoustic emission signals. The results have an impact on the implementation of more precise rolling contact fatigue tests and evaluation of parameters of acoustic emission signal. On the basis of experiments was established methodology for more precise RCF testing method using acoustic emission on test-rig AXMAT II.
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