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Adhesion modelling of grease lubricant in wheel-rail contact
Kuchař, Tomáš ; Voltr, Petr (referee) ; Kvarda, Daniel (advisor)
Currently, there are efforts to optimise the coefficient of adhesion in wheel-rail contact to reduce wear, noise and energy consumption. A project to create a digital twin for the Brno–Adamov line is being solved by ŠKODA TRANSPORTATION, a.s., the Jan Perner Transport Faculty of the University of Pardubice and the Institute of Machine and Industrial Design of the Brno University of Technology. In this thesis, within the previously mentioned project, the problem of grease retentivity was addressed, which is the distance or time for which the grease is able to efficiently lubricate the contact and thus maintain the adhesion coefficient at the desired level. The main objective of this work was to develop a model describing the effect of climatic conditions and operating parameters on retentivity of grease. The studied grease was BECHEM EcoRail 2009, which consists of bentonite thickener and a synthetic ester as a base oil. The grease was studied on a commercial Mini-Traction Machine (MTM) device in a ball on disc configuration. The effects of temperature, air humidity, load, slip, speed and lubricant quantity on retentivity were investigated. It was found that increasing load and slip caused a decrease in retentivity and could be described by using the energy absorbed by the lubricant. Increasing velocity caused a decrease in retentivity expressed in time but an increase in retentivity expressed in slip distance or number of cycles. Increasing the amount of lubricant caused a linear increase in retentivity. Increasing temperature caused an increase in retentivity, but only if the temperature was within the operating range of the grease. Air humidity only had an effect if condensation occurred, such that an increase in retentivity was observed. Dimensionless parameters were used in the model, which should make it possible to transfer the model to real scale. However, lubricant deposition to the rail and redistribution to other wheelsets was not included in the model. The model was then verified with a rail tribometer and it was shown that the model prediction was consistent with the measured results.
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Concentration of grease constituents in the EHD contact and its surroundings
Palán, Miroslav ; Čermák, Jan (referee) ; Košťál, David (advisor)
The thesis focused on the study of the effect of thickener particle size and speed on the concentration of grease particles (thickener and base oil) in the contact and its close surroundings. The calibration images were taken on a sandwich module and the experiments were carried out in a ball-on-disk configuration. The distribution of particles in the grease was investigated by fluorescence microscopy, which allows separate observation of the individual particles. The results showed that the particle size of the thickener fundamentally affects its concentration in and around the contact. The larger particle size is found in the lubricant, the higher is it concentration in the contact. The work also shows the effect of changing the velocity on the change in concentration of the individual components and the connection of the transition velocity with the distribution of the components. The work gives a new perspective on the behavior of greases and provide useful knowledge for the development and optimization of greases for different applications.
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Distribution of grease in rolling bearing
Hynek, Jakub ; Čermák, Jan (referee) ; Šperka, Petr (advisor)
The work deals with the issue of grease distribution in a rolling bearing. Grease lubricated ball bearing in this way often experience the problem of starvation, when the contact area is not sufficiently supplied with lubricant, which leads to bearing failure. In general, this is a very complex and comprehensive topic. Specifically, the description of the effect of selected parameters on the distribution of grease in the rolling bearing was solved. The evaluation took place on the contact surfaces of the inner and outer ring and bearing balls. The average film thickness in selected areas at the point of contact and in front of it were evaluated. The method for observation was fluorescence microscopy. The effects of the percentage filling of the bearing with grease, the speed, the material and the design of the cage on the distribution and distribution of the grease on the bearing surfaces are described in the thesis. The result is information about the distribution of the grease on the raceways and balls of the bearing and their immediate surroundings. It was shown that the new experimental approach used makes it possible to evaluate the amount of grease available for bearing lubrication in a real configuration.
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Study of starvation in a grease-lubricated elastohydrodynamic contact
Kuňák, Jiří ; Hartl, Martin (referee) ; Svoboda, Petr (advisor)
This diploma thesis is an experimental study of grease lubrication in a starved elastohydrodynamic lubricated (EHL) contact. Lubricating film thickness is measured with tribological experimental device ball-on-disc using optical interferometry and high speed camera. The experiment is aimed at a comparison of results acquired by ball-on-disc device and full scale axial bearing. In addition, this paper also investigates the influence of number of the rolling elements (overrolling time) on the resulting film thickness.
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Development of a testing system for evaluation of rolling bearings with variable lubrication parameters
Škoviera, Jozef ; Čermák, Jan (referee) ; Omasta, Milan (advisor)
The presented diploma thesis deals with the design of a test system for rolling bearings, which allows the change of the lubrication parameters (e.g. changing of the relubrica-tion interval). In the document, the reader first learns about the meaning of lubrication of rolling bearings, the possibilities of lubricant supply to the bearing (specifically for the supply of grease) and the possibilities of dosing control. Subsequently in the document is described the present state of experimental stations for testing rolling bearings, which is available at the Institute of Machine and Industrial Design. The end of the part about current state of knowledge is also mentioned the possibility of speeding up fatigue tests. In the next part, the author describes his own solution. The result is the design of an experimental station (for option to relubricate with grease), the creation of a lubrication control platform and the creation of a basic program. Part of the work is also verification experiments and drawing documentation.
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Study of Correlation between Grease Film Formations and Mechanical Losses on Various Surfaces
Sakai, Kazumi ; Glovnea, Romeo (referee) ; Gonçalves, David (referee) ; Křupka, Ivan (advisor)
Tato disertační práce se zaměřuje na studium závislosti mezi reakčním momentem ložiska mazaného plastickým mazivem s lithným mýdlem a vlastnostmi maziva, jako například tloušťka vytvářeného mazacího filmu, jeho reologie, struktura zpevňovadla, trakční vlastnosti či vliv topografie povrchu. Typ maziva poskytujícího nižší odpor závisí na podmínkách provozu ložiska, zejména rychlosti. Chování mazacího filmu za nízkých rychlostí má vliv na reakční moment ložiska v nízkých rychlostech. Mez toku a trakční chování koreluje s momentem ložiska za vysokých rychlostí. Schopnost zpevňovadla vstupovat do kontaktu má vliv na tloušťku filmu, vzhled kavitační oblasti na výstupu kontaktu a chování hladovění. Důvod vstupu zpevňovadla do kontaktu je jeho chemická struktura. Vysoká polárnost hydroxylových sloučenin zpevňovadla podporuje jeho vtažení kontaktními povrchy. Mazivo s nejvyšší polaritou prokázalo na površích obsahujících denty nejčastější vstup do prostoru dentů. Na základě předchozích pozorování je navržen popis principu mechanismu mazání.
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Influence of the grease aging to its behavior in the vicinity of the elastohydrodynamic contact
Navrátil, Marek ; Dzimko, Marián (referee) ; Košťál, David (advisor)
This thesis aims to describe the differences in grease behaviour caused by degradation. Observation of EHL contact and its surroundings is done using optical fluorescence, which allows to measure lubricant thickness even if it is discontinuous and air is present. New grease is observed, along with samples aged in bearings. One sample was worked for 1000 hours, which was the planned duration of the experiment. Two other samples were stopped prematurely after approx. 900 hours. Several possible age-related factors were examined and strong link between contamination and grease behaviour was found. In observed cases, contamination was identified to be the leading cause of lubricant shortage near EHL contact, which is one of possible bearing failure causes. The results expand existing knowledge about grease lubrication topic, but much further research is needed.
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Review of grease types
Mauer, Jindřich ; Ficza, Ildikó (referee) ; Košťál, David (advisor)
This bachelor thesis provides a basic distribution of greases according various aspects, which are used for lubrication the various components. The first part of bachelor thesis deals with the composition of greases. The following section describes the manufacture of greases. Another section includes the distribution of greases in terms of their composition. The following section is about distribution of greases in terms of practical use. The last part of the bachelor thesis deals with transmission electron microscopy, by this method is possible to examine the structure of greases.
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Design of adaptive wiper of liquids
Novotný, Antonín ; Nečas, David (referee) ; Košťál, David (advisor)
This thesis deals with the structural design of the adaptive fluid wiper, which is the complement of laboratory equipment. Laboratory equipment is used to study the thickness of the lubricating layer and the frictional force at contact. The purpose of the adaptive wiper is to remove the maximum amount of liquid from a moving planar disc or to make a uniform film in a rolling path around the periphery of the disc. Among the most controllable features, there are the wiper geometry, the evenly pressing and the follow the disc throwing. The thesis includes the design report, drawings and 3D model.
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Experimental observation of grease migration in a rolling bearing simulator
Palán, Miroslav ; Okál, Michal (referee) ; Košťál, David (advisor)
This thesis is using fluorescence microscopy to separately observe components of grease lubricate in simulator of ball rolling bearing. Simulator is in the configuration ball-on-disk when the disk was replaced by the outside ring made by tempered glass. This ring allows light passing to normally unseeable places of steel bearing. By the separate study of greases particles, coloured with special fluorescent dye, was found that method of fluorescence microscopy can be used to gain information about grease lubricated process in bearing.
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