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Start Over Creator Hartl, Martin

2. Controlling and measuring starvation severity in EHL contacts

Creator:
Košťál, David, Šperka, Petr, and Hartl, Martin
Format:
bez média and svazek
Type:
model:article and TEXT
Subject:
elastohydrodynamic lubrication, starvation, and replenishment
Language:
English
Description:
Starvation is the regime of elastohydrodynamic lubrication which is designated with thinner lubrication films than fully flooded regime. Paper summarizes main aspects of starvation and deals with differences in area of experimental investigation of starved lubrication phenomena in comparison with fully flooded regime. Thinner lubrication film creates obstacles in experiment process and data evaluation. Effect that can be neglected in the fully flooded regime can create obstacles. and Obsahuje seznam literatury
Rights:
http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public

3. Mapping of film thickness in bovine serum lubricated contacts

Creator:
Vrbka, Martin, Návrat, Tomáš, Křupka, Ivan, Hartl, Martin, and Gallo, Jiří
Format:
bez média and svazek
Type:
model:article and TEXT
Subject:
artificial hip joint, femoral head, bovine serum, protein formation, lubrication, film thickness, and colorimetric interferometry
Language:
English
Description:
The aim of this study is to perform detail experimental mapping of the lubricating film thickness of bovine serum (BS) within the contact between an artificial metal or ceramic femoral head and a glass disc and analyze effect of proteins on the film formation. Mapping of the lubricating film of various concentrations of BS solutions was carried out using an optical test rig. Chromatic interferograms were recorded with a high-speed digital camera and evaluated with thin film colorimetric interferometry. The film thickness was studied as a function of both time and mean speed. The results showed that film thickness increases with time for both the metal and ceramic heads. Films formed at the end of measurements with the metal head were found to be typically in the range of 60-100 nm for all BS solutions and were independent on the amount of proteins in tested fluids. At the beginning of the speed measurements, BS of all concentrations forms a very thin film (1-2 nm) and its thickness increases with increasing mean speed. However, when the speed was decreased, the film thickness did not reduce but increased with decreasing speeeds that supports the findings of other researchers. Moreover, it was found that BS supply is sensitive parameter. When the lubricant reservoir below tested head was used then the measured central film thicknesses achieved values only about 20 nm, whereas when the tests were realized without the reservoir, measured central film thicknesses achieved higher values about 100 nm. For both types of the experiments, distribution of the film thickness within the contact zone is not homogeneous and two different film thickness regions can be found; thicker protein film and thinner base film that both increase with time and speed. and Obsahuje seznam literatury
Rights:
http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public

4. Transient calculations in elastohydrodynamically lubricated point contacts

Creator:
Ficza, Ildikó, Šperka, Petr, and Hartl, Martin
Format:
bez média and svazek
Type:
model:article and TEXT
Subject:
elastohydrodynamic lubrication, surface roughness, fluid rheology, and multigrid method
Language:
English
Description:
The aim of the paper is to present transient calculations of an elastohydrodynamically lubricated (EHL) point contact. The paper focuses on the description of the numerical algorithm used to model non-smooth contacts with surface feature on one of the contacting bodies. Results of film thickness and pressure distributions of a selected surface feaure are presented. Simulations were performed and compared for two different rheology approaches (Newtonian, resp. non-Newtonian). and Obsahuje seznam literatury
Rights:
http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public

5. Twin-disc experimental device for study of adhesion in wheel-rail contact

Creator:
Galas, Radovan, Smejkal, David, Omasta, Milan, and Hartl, Martin
Format:
bez média and svazek
Type:
model:article and TEXT
Subject:
wheel/rail contact, adhesion curve, twin-disc, and traction
Language:
English
Description:
In order to understand friction processes in wheel/rail contact a new experimental device has been developed. Twin-disc approach has been used to determine adhesion curves in wheel-rail contact under various conditions. This paper describes some details about the design of the twin-disc experimental device. Finally, preliminary results are discussed. and Obsahuje seznam literatury
Rights:
http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public

6. Užití spektroskopické reflektometrie při studiu elastohydrodynamického mazání

Creator:
Čudek, Vladimír, Křupka, Ivan, and Hartl, Martin
Format:
bez média and svazek
Type:
model:article and TEXT
Subject:
EHD, tenké mazací filmy, and spektroskopická reflektometrie
Language:
Czech
Description:
Paper deals with the application of spectroscopic reflectometry for the central lubrication film thickness measurement in elastohydrodynamic contacts. This approach overcomes the main limitations of other measurement techniques used for film thickness measurements in tribological problems studies and provide absolute data that eliminates the relative comparation between calibration table and measured lubrication film. and Článek se zabývá problematikou využití spektroskopické reflektometrie ke stanovení centrální tloušťky maziva, případně rozložení tlaku v elastohydrodynamickém (EHD) kontaktu při studiu tribologických problémů. Jedná se o metodu, jejíž silnou stránkou, na rozdíl od dnes nejpoužívanějších měřicích technik, je absolutní měření.
Rights:
http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public

7. Užití spektroskopické reflektometrie při studiu elastohydrodynamického mazání

Creator:
Čudek, Vladimír, Křupka, Ivan, and Hartl, Martin
Format:
bez média and svazek
Type:
model:article and TEXT
Subject:
precision mechanics, přesná mechanika, EHD, tenké mazací filmy, and spektroskopická reflektometrie
Language:
Czech
Description:
Paper deals with the application of spectroscopic reflectometry for the central lubrication film thickness measurement in elastohydrodynamic contacts. This approach overcomes the main limitations of other measurement techniques used for film thickness measurements in tribological problems studies and provide absolute data that eliminates the relative comparation between calibration table and measured lubrication film. and Článek se zabývá problematikou využití spektroskopické reflektometrie ke stanovení centrální tloušťky maziva, případně rozložení tlaku v elastohydrodynamickém (EHD) kontaktu při studiu tribologických problémů. Jedná se o metodu, jejíž silnou stránkou, na rozdíl od dnes nejpoužívanějších měřicích technik, je absolutní měření.
Rights:
http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public