Currently, finite element analysis (FEA) serves as the only analytical tool used in the evaluation of seals. The FEA does not allow the dynamic analysis of the seal, which must be performed experimentally. As a result, the designing of a seal can be a costly and extensive procedure. The aim of this project has been to develop a numerical model and computer program that will have the ability to predict key seal performance characteristics, such as leakage and friction. This numerical model provides a means for evaluating potential seal designs, which can be performed without having to endure the costs of creating and evaluating the performance of the seal. Thus, the numerical model reduces the time and cost involved in evaluating seal designs. The numerical model developed differs from previous models as the effects of mixed lubrication and surface roughness are investigated. This model consists of three coupled analyses of fluid mechanics, deformation, and contact mechanics. After computational procedure has converged coupling the three analyses, auxiliary calculations are performed to obtain the quantities of leakage rate and friction force. These obtained results then allow the evaluation of the seal design, which will lead to better seal designs with lower friction and less (or no) leakage. The results obtained for a typical hydraulic seal show that the leakage characteristics depend strongly on the seal roughness.

In this study, the mixed lubrication of line contact is numerically calculated and analyzed. The surface asperities are in contact for mixed lubrication which differs from elastohydrodynamic lubrication. In this study, the Poiseuille term is neglected when the film thickness was smaller than the cut-off value about 0.5 nanometer, so that the surface asperities in contact or not contact can be solved in a system equation using the Newton-Raphson method. The mixed lubrication was studied in three parts, including the steady-state, the transient state and the start-up process. The effect of amplitude and wavelength on the film thickness and the pressure are investigated using the deterministic quantifiable method. The mixed lubrication zone in terms of rolling speed and load is established for the smooth surface under the steady-state conditions. For a single asperity on the surface, results show that the maximum pressure increases with increasing amplitude and decreasing wavelength. At high load situation, the film thickness is flattened around the asperity in the steady-state conditions, but it is increased due to the squeezing effect in transient state. For the start-up process, two surfaces are gradually separated due to the growth of film thickness, so that the contact area of two surfaces decreases linearly with time. However, the interval of contact time decreases with increasing roller speed and Young¡¦s modulus, but decreasing load.

Health condition monitoring, commonly referred as Integrated Vehicle Health Management (IVHM) for fleets or vehicles, studies the current and future health state of a system. Health monitoring techniques based on data driven approaches have proven successful in several areas and are easily scalable; however they do not rely on the understating of the physics of failure; whereas Physics-based Model (PbM) approaches require expert knowledge of the failure modes and are based on the understanding of the component behaviour and degradation mechanisms. The development of IVHM is particularly challenging for legacy aircraft due to the restrictive regulations of the aerospace industry. This thesis proposes a novel PbM technique to detect metal-metal contact in hydrodynamic bearings. The planetary transmission of an aircraft’s Integrated Drive Generator (IDG) is used as a case study. Research on the detection of metal-metal contact in hydrodynamic bearings has focused on data driven approaches using vibration or acoustic emissions rather than on PbMs. The proposed technique estimates metal-metal contact by modelling the physical phenomena involved in the failure mechanism and only the speed, load and temperature are required as inputs, all of them available in the IDG and not requiring any additional sensors. The study of metal-metal in hydrodynamic bearings in the field of tribology has focused on mixed lubrication models of the whole bearing, or computational models accounting for local effect under the hydrodynamic lubrication region. In addition to the IVHM technique, this thesis contributes to the field of tribology by proposing a computational mixed lubrication model capable of studying metal-metal contact locally along the lubricated surface of the bearing. Experimental results of a plain journal bearing have been used to validate the PbM and a replica of the transmission of the IDG has been tested to evaluate the effectiveness of the proposed technique at detecting metal-metal contact.

No description available.

This thesis describes a study of the influence of surface texturing on rolling contact fatigue of non-conformal contacts. The texture depth and density have been considered during experiments. It also presents the methodology and the procedure of creation of micro-dents on sample surfaces. Described results suggested that properly designed surface texturing should not necessarily increase the risk of fatigue failure of rubbing surfaces.

Axial piston machines are operating at high pressure and varying speeds, which requires high reliability of the components. The machine components are separated by a fluid film, but sometimes this film gets penetrated by the surface asperities causing the machine to operate with metal-to-metal contact. In order to improve the design and predict the operating conditions might numerical tools be used. The goal with this thesis was to describe how the tribological contacts in Parkers machines can be modelled, considering oil and surface roughness. The so called Luleå Mixed Lubrication Model have therefore been investigated and it has been described how the model can be used in Parkers machines. The model uses a two-scale method to include the influence of real surface topographies of the components, it gives information about how the surface roughness affect the lubrication conditions. Different options of softwares have been investigated and compared to get an understanding of what possibilities and shortcomings they might have when it comes to this kind of simulations. Results show that all interesting contacts can't be treated the same, therefore must each contact be investigated separetly even though the Luleå Mixed Lubrication Model is used in all cases.

The purpose of this diploma thesis is to describe the influence of artificially produced surface grooves on transition from full EHL regime to mixed lubrication in point contact using optical interferometry. This article focuses on influences of grooves orientation, length in contact area, elastic properties of contact surfaces and different types of oil defined by pressure-viscosity coefficient. Empirical prediction model of groove influence on film thickness was established based on experimental data. The groove influence was incorporated into lubrication parameter. This modified definition was compared to classic one. It showed that avoiding groove influence in classic definition lead to significant underestimation. Influence of groove on friction coefficient is also studied.

Náplní této disertační práce je popis komplexní a obecně použitelné strategie výpočetního modelování chování kluzných ložisek, pracujících v režimu smíšeného mazání a uvažujících reálné struktury drsných povrchů obou členů kluzných ložisek – ložiskových pánví a ložiskových čepů. V práci jsou uvedeny a detailně popsány způsoby získání charakteristických popisných dat těchto drsných povrchů a její nedílnou součástí je i popis numerických algoritmů, sloužících k následnému zpracování těchto dat. Dále jsou zde rozebrány implementované výpočetní přístupy k modelování kontaktního tlaku. Ovlivnění hydrodynamické mazací vrstvy kluzných ložisek je dáno velikostí a průběhem faktorů toku, jejichž numerické stanovování je zde detailně popsáno. Alternativní stanovení faktorů toku pomocí analytických funkcí je zde pro úplnost rovněž obsaženo. V závěru práce je uveden popis numerického řešiče modelování chování kluzných ložisek spolu s uvedenými výsledky provedených simulací a jejich diskuzí. Ověření jednotlivých výpočetních modelů, popřípadě porovnání výsledků s výsledky získanými alternativním způsobem, je uvedeno v příslušných kapitolách.

Este trabalho trata de um estudo experimental das respostas de desgaste e de atrito encontradas em um sistema deslizante lubrificado. Para tanto, foram realizados ensaios de deslizamento em um equipamento para ensaios de desgaste, adotando-se o dispositivo pino-contra-disco, para ensaios com movimento relativo rotativo contínuo entre as amostras, e o dispositivo pino-contra-placa, para ensaios com movimento relativo alternado, ou oscilatório, entre as amostras. Os materiais metálicos ensaiados foram pinos de aço AISI 52100 e contra-corpos de aço AISI 8640. O óleo lubrificante foi o mineral de base parafínico, IV 100. Foram variadas as condições de aditivação e de contaminação do óleo lubrificante e foram utilizados dois níveis de carregamento mecânico, determinada pela relação velocidade/carga. O desgaste foi estudado por microscopia óptica e eletrônica de varredura, medição da área afetada pelo desgaste, perfilometria das superfícies desgastadas e análise de óleo. O atrito e o potencial de contato foram monitorados ao longo dos ensaios. Os resultados obtidos mostraram que o desgaste dos corpos metálicos foi sensível ao carregamento mecânico, à aditivação e à contaminação do óleo. Diferenças foram notadas nas morfologias superficiais entre os resultados de desgaste dos ensaios rotativos e oscilatórios. / This work concerns with experimental study of wear and friction responses of lubricated sliding system. Sliding tests were carried out using pin-on-disk wear testing machine for tests with continuous rotating movement, and the pin-on-plate device, for reciprocating tests between specimens. The metallic test coupons were AISI 52100 steel pins and AISI 8640 steel counter-faces. The used lubricant was paraffinic mineral oil, VI 100. The presence of additives and contamination in the lubricant oil were investigated under two mechanical loading levels, determined by the velocity/load relation. The wear was studied by means of optic and scanning electronic microscopes, perfilometry and dimensional analysis of the worn surfaces and oil analysis. The friction and the contact potential were monitored through out the sliding tests. The results showed that the wear of the metallic materials was susceptible to the mechanical loading, the additive and the contamination existence in the oil. It was observed differences among the wear results of the rotating and the reciprocating tests in terms of surface morphologies.

Este trabalho trata de um estudo experimental das respostas de desgaste e de atrito encontradas em um sistema deslizante lubrificado. Para tanto, foram realizados ensaios de deslizamento em um equipamento para ensaios de desgaste, adotando-se o dispositivo pino-contra-disco, para ensaios com movimento relativo rotativo contínuo entre as amostras, e o dispositivo pino-contra-placa, para ensaios com movimento relativo alternado, ou oscilatório, entre as amostras. Os materiais metálicos ensaiados foram pinos de aço AISI 52100 e contra-corpos de aço AISI 8640. O óleo lubrificante foi o mineral de base parafínico, IV 100. Foram variadas as condições de aditivação e de contaminação do óleo lubrificante e foram utilizados dois níveis de carregamento mecânico, determinada pela relação velocidade/carga. O desgaste foi estudado por microscopia óptica e eletrônica de varredura, medição da área afetada pelo desgaste, perfilometria das superfícies desgastadas e análise de óleo. O atrito e o potencial de contato foram monitorados ao longo dos ensaios. Os resultados obtidos mostraram que o desgaste dos corpos metálicos foi sensível ao carregamento mecânico, à aditivação e à contaminação do óleo. Diferenças foram notadas nas morfologias superficiais entre os resultados de desgaste dos ensaios rotativos e oscilatórios. / This work concerns with experimental study of wear and friction responses of lubricated sliding system. Sliding tests were carried out using pin-on-disk wear testing machine for tests with continuous rotating movement, and the pin-on-plate device, for reciprocating tests between specimens. The metallic test coupons were AISI 52100 steel pins and AISI 8640 steel counter-faces. The used lubricant was paraffinic mineral oil, VI 100. The presence of additives and contamination in the lubricant oil were investigated under two mechanical loading levels, determined by the velocity/load relation. The wear was studied by means of optic and scanning electronic microscopes, perfilometry and dimensional analysis of the worn surfaces and oil analysis. The friction and the contact potential were monitored through out the sliding tests. The results showed that the wear of the metallic materials was susceptible to the mechanical loading, the additive and the contamination existence in the oil. It was observed differences among the wear results of the rotating and the reciprocating tests in terms of surface morphologies.