A thorough investigation on the existing hydrodynamic lubrication theories and the reverse pumping theories for the conventional lip seal is conducted. On that basis, the algorithms and the methods used in the numerical modeling of the conventional lip seal are modified and applied to the study of the lip seal running against surface textured shafts. For each step of the study, the numerical model is benchmarked against the experimental results. Important physical mechanisms which explain the reverse pumping ability of the triangular surface structures are revealed. Meanwhile, the accuracy of the numerical model is tested. In general, the numerical simulation results match the experimental observation well. However, there are several important discrepancies. For each discrepancy the possible causes are discussed, which benefits the further attempts of the modeling work on the lip seal running against surface textured shafts. The conclusions of this study themselves can be used as a guidance to the design of the surface textured shafts for the lip seal applications. Finally the limitation of the current theories and the modeling methods are discussed and reasonable improvements which can be done are proposed for the future work.

Gear rattle is caused by engine torsional vibration (engine order response) imparted to the transmission components, further causing the gears to oscillate within their functional backlashes. These oscillations lead to the repetitive impact of gear teeth, which lead to noisy responses, referred to as gear rattle. The lack of in-depth research into the effect of lubricant on gear rattle has been identified as a deficiency in the previous research in rattle. The aim ofthe current work is to address this shortcoming. The thesis outlines a new approach in investigating the problem of idle gear rattle. The approach is based on the assumption that under idling condition the teeth-pair impact loads are sufficiently low and the gear speeds are sufficiently high to permit the formation of a hydrodynamic lubricant film between the mating gear teeth. This film acts as a non-linear spring-damper that couples the driver and the driven gears. A torsional single-degree of freedom model is used in the development of the theory. The model is then expanded into a seven-degree of freedom torsional model and finally into an Il-degree of freedom model that also includes the lateral vibrations of the supporting shafts. The Il-degree of freedom model is based on a real life transmission that is also used in experimental studies to validate the model. It is found that lubricant viscosity and bearing clearance (lubricant resistance in squeeze) play important roles in determining the dynamics of the system and its propensity to rattle. At low temperatures, the lateral vibrations of the shafts, carrying the gears interfere with the gear teeth impact action. The severity of rattle is determined by the relationship between the entraining and squeeze film actions of the hydrodynamic film. When the latter dominates, the system can rattle more severely. The numerical results are found to correlate well with the experimental findings obtained from vehicle tests in a semi-anechoic chamber and also with those from a transmission test rig in the powertrain laboratory.

The elastohydrodynamic lubrication regime (EHD) is found in many machine elements, such as rolling element bearings, gears, cam/tappet, where a combination of hydrodynamic effect, elastic deformation of the surfaces and an increase of the lubricant’s viscosity with pressure create a continuous lubricant film which is capable of supporting pressures of the order of tens of thousands of atmospheres. One of the most important features of these films is their thickness, as this determines whether the bounding surfaces are completely separated, thus avoiding premature wear and failure of the contact. Consequently for many years scientists were interested in finding methods for measuring the lubricant film thickness in elastohydrodynamic conditions. One of the most versatile and widely used techniques for measuring lubricant film thickness in EHD contacts is the optical interferometry method. Apart from numerous advantages, this method has the limitation in the fact that one of the contacting surfaces must be transparent, usually glass or sapphire, thus it does not replicate real conditions found in machine elements contacts. On the other hand, the other group of methods used for studying the behaviour of elastohydrodynamic films includes a variety of electrical methods. Historically, these appeared before the optical methods, but gradually lost importance with the success of the later. Most capacitive, resistive, inductance methods developed so far use specially designed sensors for monitoring the lubricant film thickness. In the case of electrical techniques, both elements of the contact are metallic, which means that these can be used for measuring film thickness in real machine elements. One of the main disadvantages of electrical methods though, is the difficulty with which the calibration of various electrical quantities, against lubricant film thickness is obtained. This thesis describes the work carried out by the author on the application of a capacitive method for studying lubrication of elastohydrodynamic contacts. The novelty of the method used consists in the calibration of the capacitance of the contact with optical interferometry. This project started from the premises that a thicker Chromium layer will supply the phase change needed to precisely measure the lubricant film thickness by eliminating the fragile silica layer, and it has been shown that an increase in Cr thickness results in a increase in reflection of the glass–Cr interface making the resulting images hard to process. Modifications to the existing experimental rig were carried out in order to apply/collect an electrical signal from both the disc and the ball. Signal collection from the disc was quite straightforward and a graphite brush paired with a copper nut was used, as this is the oldest method of collecting/applying and electrical signal from a rotating element. Collecting an electrical signal from the ball presented quite a challenge as the ball is submerged in oil. A number of brushes was designed, made and tested and the one that provided the most stable results chosen. For calibration purposes a base oil and two additives were chosen, the additives were chosen in such a way that the improvement made to the lubrication process to be very different from one additive to the other. The chosen additives were a Viscosity Index Improver [VII] and an Organic Friction Modifier [OFM]. The VII is used by many researchers in order to obtain multigrade lubricants using the same base oil by varying its percentage in the mix. The OFM is used to provide protection between the two contacting bodies when EHD film fails and EHD lubrication is replaced by mixed lubrication by forming a boundary layer on the contacting surfaces. Optical measurements were carried out on the base oil and the two resulting lubricants from the additive mixes using the Ultra Thin Film Interferometry [UTFI] method. The measurements were used as a benchmark against which the capacitive measurements were calibrated. Tests were conducted in a number of controlled conditions for speed, temperature, load and sliding conditions. Results showed that the highest influence on the lubrication process was given by the speed, an increase in speed results in an increase in optically measured film thickness and a decrease in electrically measured film thickness. Phenomenon explained by a large amount of lubricant pushed into the contact. Another parameter that influenced the results quite significantly was temperature, a rise in temperature supplies a decrease in optically measured film thickness and an increase in capacitive measured film thickness which was explained by lubricant viscosity dropping with a rise in temperature. Three different sliding conditions were employed and a small drop in optically measured film thickness followed by a small rise in electrically measured film thickness was recorded due to a local increase in contact temperature when sliding was employed. The capacitive method developed in this project is precise enough to accurately measure lubricant film thickness down to 100nm; a model for thicknesses lower that 100nm was proposed Results from the optical and capacitive methods were compared and a good correlation was found, indicating that the developed capacitive method can be used as a tool for measuring metal on metal contacts without further calibration.

Ce travail s’intéresse au renforcement mécanique de films lubrifiants auto-assemblés en milieu aqueux par réticulation. Deux stratégies ont été suivies. La première consiste à réticuler physiquement un film de tensioactifs cationiques par coadsorption d’un copolymère associatif anionique. La deuxième est de réticuler chimiquement un film de copolymères triblocs par la création de liaisons covalentes entre les différentes macromolécules. Nous étudions l’auto-assemblage des films par microbalance à cristal de quartz et microscopie à force atomique (AFM). Nous discutons ensuite les effets de la réticulation sur la morphologie des films (caractérisée par AFM), et sur leurs propriétés mécaniques mesurées avec l’appareil à mesure de force SFA-nanotribomètre. Cette étude a montré que dans les deux cas, la réticulation modifie les propriétés des films lubrifiants et permet une augmentation de la cohésion des films adsorbés. / In this work, we study the effect of cross-linking on boundary lubricant films in aqueous media. Two strategies have been followed. First, we investigate a physical network on a cationic surfactant bilayer by coadsorption of an anionic copolymer. Secondly a tribloc copolymer film was chemically cross-linked by creating some chemical bounds between macromolecules. We study film self-assembling by Quartz Crystal Microbalance and Atomic Force Microscopy. We discuss then on the effect of cross-linking on the morphology of the film and its mechanical properties by combining AFM and Surface Force Apparatus SFA-nanotribometer. We have shown that in both cases, lubricant films properties are modified and the cohesion of the adsorbed films is increased by cross-linking.

I pappersmaskiner används kräppblad för att kräppa av pappret från en stor roterande cylinder, en så kallad yankee-cylinder. Dessa blad utstår stora nötningar och beläggs därför med antingen en kromoxidbeläggning eller en hårdmetallsbeläggning för att öka bladets nötningsbeständighet. Bladen beläggs med termisk sprutning, kromoxiden via plasmasprutning och hårdmetallen via "High-Velocity-Oxy-Fuel"-sprutning (HVOF). I detta arbete har slitagetester utförts på belagda kräppblad genom att använda en "slider-on-flat-surface" (SOFS) tribometer för att ta reda på vilken av dessa beläggningar som är bäst lämpad för att användas på kräppblad. Vid användning av SOFS belastas kräppbladen med en normalkraft och glider mot en platta till önskad total glidsträcka är uppnådd. För att kunna genomföra slitagetesterna i SOFSen behövdes en fixtur konstrueras och tillverkas och kräppblad behövde kapas till önskad geometri. Det skapades tre koncept för fixturen och med en beslutsmatris gjordes valet vilken av dem som skulle tillverkas. Den tillverkade fixturen håller kräppbladen stabila i både sidled och i glidriktningen och håller kräppbladen i en vinkel likt i verkligheten. Slitagetesterna utfördes vid tre olika glidsträckor med konstant normallast. Efter slitagetesterna analyserades bladen i stereomikroskop och svepelektronmikroskop för att identifiera nötningsmekanismer. De dominerande nötningsmekanismerna var abrasiv och adhesiv nötning. På grund av porositet i beläggningarna ökades antalet sprickor och mer och mer fragment lossnade vid ökande glidsträcka under slitagetesterna. Det visade sig efter mätningar av bortnött bredd på bladet att det hårdmetallbelagda kräppbladet hade bäst nötningsbeständighet. Detta på grund av dess hårda tungstenkarbider som minskade den abrasiva nötningen och spricktillväxten i beläggningen och dess högre duktilitet jämfört med kromoxiden. / Creping blades are used in paper machines for creping tissue paper from a rotating cylinder called a yankee cylinder. These blades experience severe wear and are therefore coated by either chromium oxide or a hard metal coating to make the blades more wear resistant. The coatings are sprayed on to the blade by thermal spraying processes, the chromium oxide coating with plasma spraying and the hard metal coating with "High-Velocity-Oxy-Fuel" (HVOF) spraying. In this thesis wear testing of the coated creping blade using a "slider-on-flat-surface" (SOFS) tribometer has been done to find out which of these coatings that is best suited for coating on the creping blade. When using the SOFS, the creping blade is subjected to a chosen normal force and is scraped against a counterface for a set total distance. In order to execute the wear tests in SOFS, construction and manufacturing of a holder for the creping blades was needed and the creping blades had to be cut to correct geometry. Three concepts were created for the holder and the decicion about which one to manufacture was made with a decision matrix. The new holder holds the creping blades stable in side movements and in the sliding direction. It also keeps the blade at a set angle to the counterface as in the real application. The wear tests consisted of three sliding distances with constant normal load. The blades were analyzed in a stereo microscope and in a scanning electron microscope to identify the wear mechanisms when the wear tests were completed. The major wear mechanisms were abrasive and adhesive wear. Because of porosity in the coatings, the number of cracks increased and fragments from the blades came loose when increasing the sliding distance during the wear tests. It showed that by measuring the eroded width on the blades that the hard metal coated blade had the best wear resistance because of the hard tungsten carbides that lowered the abrasive wear and the crack growth in the coating and because of its higher ductility in comparison to chromium oxide.

Cone crushers are widely used in the mining, mineral processing and quarrying segments of the industry to crush ores and large rocks. In such machinery, the load to be carried is rather heavy and the motion is gyratory which creates a need for a bearing set that can withstand such severe conditions. Sandvik AB is a high-technology Swedish engineering group specialized in tools and tooling systems for metal cutting, equipment, as well as tools and services for the mining and construction industries. One of their products relevant to the mining industry is the cone crusher which utilizes a 3-piece bearing set to carry thrust load. This bearing can be classified as a Spiral Groove Bearing \footnote{The abbreviation S.G.B will be used interchangeably throughout the thesis.}, and it has been incurred that it wears out rather quickly and is believed to be running under mixed-lubrication conditions where the interfaces in the bearing-set are not fully lubricated. The aim behind this thesis is to create a multiphysics model of this bearing in order to understand deeply how it works and the reasons why it does not perform as expected as well as to predict design improvements which can improve the performance of the bearing-set, thus increasing its operating life. It has been concluded that the bearing operates under severe mixed-lubrication conditions and that the generation of a squeeze film is the only method by which lubrication takes place due to the excessive depth of the grooves which is needed to allow for an adequate amount of cold oil to flow into the grooves and cool the interface as well as to accommodate for a considerable amount of wear particles. In light of the results and insight gathered from the simulations, possible design variations of the bearing which can be advantageous in terms of mitigating asperity friction in the interfaces of the bearing are discussed and tested.

L’élaboration de combustible nucléaire UO2-30%PuO2 pour les nouveaux réacteurs nucléaires de Génération IV repose sur l’utilisation de plutonium issu du recyclage des combustibles MOX (Mélange d’OXydes UO2-PuO2) des réacteurs actuels. Par rapport au Pu initial, ce plutonium présente une proportion d’isotopes fissiles beaucoup plus faible et une quantité plus importante (x30) en 238Pu dont l’activité spécifique alpha et la puissance thermique sont importantes. Le procédé d’élaboration du combustible qui consiste à mettre en forme les poudres d’oxydes par pressage met en jeu un lubrifiant organique, le stéarate de zinc. L’objectif de la thèse est d’étudier le comportement en température et sous irradiation de ce composé. Un effet de la montée en température et du vieillissement en température a été observé sur les propriétés cristallographiques du stéarate de zinc, avec une amorphisation partielle du matériau qui engendre une détérioration de ses propriétés de lubrification dès 110°C. La dégradation radiolytique du stéarate de zinc a été étudiée à travers l’analyse des gaz produits par irradiation alpha au contact de poudres de PuO2 ou par irradiation externe aux hélions, complétée par des analyses physico-chimiques du stéarate irradié. Les rendements de production de gaz sont calculés et permettent d’établir un mécanisme de radiolyse. Il a été montré que l’impact de la radiolyse sur les propriétés de lubrification est moindre que l’effet de la température. Le couplage des dégradations a un effet synergique, avec une détérioration des propriétés de lubrification observée à des températures plus faibles que sur le matériau non irradié. A partir de ces résultats, des recommandations d’utilisation du stéarate de zinc ont été proposées. / The manufacturing of nuclear fuels UO2-30%PuO2 for the Gen IV nuclear reactors is based on the use of plutonium coming from MOX (Mixed OXides) fuel recycling from actual reactor. This plutonium would contain a few quantities of fissionable isotopes and a significant amount (x30) of 238Pu compared to initial Pu. This isotope possesses a strong alpha activity and a great thermal power. The manufacturing process which consists in powders pressing will use zinc stearate, an additive used as lubricant. The aim of this PhD is to study the behaviour in temperature and under irradiation of this compound. An effect of temperature increasing and thermal ageing has been observed on crystallographic properties with a material amorphisation and a deterioration of lubricant properties from 110°C. Radiolytic degradation of zinc stearate has been studied through the analysis of gases produced by alpha radiation at the contact of PuO2 powders or by external radiation by helions, with the support of chemical analysis of irradiated solid. Gaz production yields are calculated and enable establishment of a radiolysis mechanism. It has been showed that impact of radiolysis on lubricant properties is less important than temperature effect. The coupling of degradations has a synergic effect, with a deterioration of lubricant properties observed at lower temperature compared to non-irradiated material. From these results, recommendations for use of zinc stearate have been proposed.

Les joints sans contact sont des solutions d’étanchéité optimales pour les systèmes mécaniques fonctionnant à des vitesses relativement élevées. Ils ont une durée de vie importante et ont été proposés pour une utilisation dans les moteurs spatiaux. Une type de joints d'étanchéité sans contact, le joint visqueux, est étudié en détail dans ce travail de thèse au moyen d'une analyse numérique et expérimentale. Ce travail présente un modèle numérique développé pour prédire le comportement du joint visqueux en régime laminaire et turbulent. L’interface liquide-air dans le joint est également étudiée en utilisant une approche CFD basée sur la méthode VOF. La conception et la réalisation d’un dispositif expérimental a permis de confronter les résultats numériques et expérimentaux, l’écart entre les deux approches n’excède pas 10% dans 95% des cas étudiés. / Contactless seals are optimal sealing solution for mechanical systems operating with relatively high speeds. They have an important operation life time, and they were proposed for use in space engines. One sub-category of non-contact seals, the viscoseal, is studied in detail in this work through a numerical and experimental analysis. This work presents a numerical model developed to predict the viscoseal performance in laminar and turbulent regime. Furthermore the sealing performance of the viscoseal is investigated for different geometrical characteristics of the seal. The interface liquid-air in the seal is also studied using a CFD approach based on VOF method. The design and installation of an experimental device allowed the comparison of the numerical and experimental results, the difference between the two does not exceed 10% for 95% of studied cases.

This project has been executed at the forestry machine track manufacturer Olofsfors AB and has been aimed at development of a rig for simulation of the wear that occurs in the linkage of Olofsfors AB forestry machine tracks. The problem is that link hooks in the tracks wears out first, often several times faster than other components. Olofsfors AB want to be able to test this wear in a controlled environment. The purpose of the wear rig is to distinguish what type of wear that is in effect as well as be able to optimize materials for Olofsfors AB: s products.   The project began with an pilot study of different types of relevant wear and different types of complete methods of wear measurement and simulation to better understand the problem. After this a market screening of existing machines and rigs that could be of interest was done. The project continued with creation of concepts of wear rigs and methods of wear. After a selection process the project proceeded with one concept to a 3D prototype.   From the market screening it could be found that the market is very thin with few suppliers. Their products are relatively expensive and need specially made test samples. The recommendation to Olofsfors AB will therefore be to construct a rig themselves. The market screening could be used by Olofsfors AB as a basis if they decide to expand their test activity in the future.    The project reached the overall goals and delivered a prototype that passes the set demands. This means that the project is basically ready to move on to construction of a physical wear rig. There are still some problems to overcome but these will be easiest to solve during the construction phase. / Projektet har utförts hos skogmaskinbandstillverkaren Olofsfors AB och har gått ut på att ta fram en rigg för att simulera den nötning som uppstår i länksystemet på Olofsfors AB:s skogsmaskinband. Problemet är att länkkrokar i banden nöts ut först, ofta flera gånger snabbare än andra komponenter. Nu vill Olofsfors AB kunna testa denna nötning i kontrollerade miljöer. Syftet med nötningsriggen är att kunna avgöra vilken typ av nötning som verkar samt kunna göra materialoptimering för Olofsfors AB:s produkter.   Projektet inleddes med en förstudie av olika typer av relevant nötning samt olika typer av färdiga metoder för att mäta och simulera nötning för att förstå problemet bättre. Efter detta gjordes en marknadsundersökning av befintliga maskiner och riggar som kan vara av intresse. Projektet fortsatte med konceptgenerering av nötningsriggar och nötningsmetoder. Efter utsållning gick projektet vidare med ett koncept till en 3D-prototyp.   Från marknadsundersökningen konstaterades det att marknaden är väldigt smal med få leverantörer. Deras produkter är relativt dyra och kräver speciella provbitar. Rekommendationen till Olofsfors AB blir därför att konstruera en egen rigg. Marknadsundersökningen kan användas som underlag av Olofsfors AB om de vill expandera sin testverksamhet i framtiden.   Projektet nådde de övergripande målen och levererade en prototyp som klarar av uppsatta krav. Detta innebär att projektet är i stort sett redo att gå vidare till konstruktion av en fysisk nötningsrigg. Vissa problem kvarstår, men dessa löses enklast under konstruktionsfasen.

O presente trabalho destina-se à discussão sobre o cálculo de vida útil de rolamentos. Mostrando o avanço do processo de cálculo ao longo das décadas até o mais alto grau de desenvolvimento atual. A preocupação do texto é demonstrar de forma simples e objetiva as divergências que existem entre a formulação teórica e a real vida dos rolamentos, no que tange a fadiga de contato. Neste contexto foram realizados testes, em máquina especialmente destinada ao ensaio da fadiga de rolamentos. Variando-se para as duas séries de ensaios, apenas, a temperatura (aproximadamente 85°C e 110°C). Os resultados obtidos indicam que a vida real dos rolamentos apresenta grande divergência se comparada com a vida útil calculada, principalmente, no regime com maior temperatura. Atribui-se a esta disparidade, a ausência de cálculos precisos quanto à correlação da vida útil com o fator l, que é uma forma de se calcular o espaçamento entre as superfícies de contato, e o não emprego do cálculo do fator de carga, na formulação da vida útil de rolamentos. / The present work has the purpose of discussing the life of rolling bearings, describing the evolution of bearing life calculation until its current state of the art. Our focus is to demonstrate, simply and objectively, the inconsistencies occurring between the actual life of rolling bearings and their theoretical fatigue life estimation. For such purpose, tests were developed in a special bearing test rig to assess bearing fatigue. Two test sets were carried out with temperature being the only variation (approximately 85°C and 110°C). Results obtained from these tests suggest that the real life of rolling bearings is indeed very different from calculated bearing life, especially under higher temperature. Such disparity can be attributed to the lack of a precise computation of the relationship between bearing real life and the l factor - which determines the thickness of lubricant separating raceways and balls - as well as to the failure to compute the load factor in bearing life estimation.