The automotive industry is constantly being challenged by customers and authorities to enhance the efficiency of the internal combustion engine (ICE) in order to achieve improved fuel consumption and reduced emissions. There are several interfaces within the design of an ICE that causes frictional losses, one of them is the valvetrain. An approach to reducing the friction in the valvetrain of modern engines is to implement cam-follower rollers, resulting in a rolling rather than sliding contact when interacting with the camshaft. The prominent type of wear in rolling contacts is surface fatigue, and specifically a phenomenon called micropitting. The company in collaboration with this project is Applied Nano Surfaces Sweden AB (ANS), located in Uppsala, Sweden. The company have specialized in surface treatment methods of mechanical components. ANS has developed a mechano-chemical treatment method called ANS Triboconditioning, which have shown beneficial friction and wear reducing properties when applied to metal surfaces. This thesis was conducted to investigate how the ANS Triboconditioning would affect the frictional behaviour compared to established surface treatment methods and the occurrence of micropitting in rolling contact configurations. Two types of test programs was implemented into a Wazau UTM 2000 Twin-Disc Tribometer. No clear trend could be established from the micropitting tests and therefore no conclusion regarding if ANS Triboconditioning affects the occurrence of micropitting damage in a positive or negative manner could be stated. The results from the friction test indicated an overall reduction in friction for the test specimens that had been treated with ANS Triboconditioning when compared to specimens that only had been treated with already established surface treatment methods. Summarized, additional tests and analyses are necessary in order to statistically confirm the observed results and determine their respective trends.

Le développement de nouvelles motorisations plus économes en carburant, entraine une augmentation du niveau de vibration. Afin de répondre à cela, Valeo développe un nouveau système : le pendule centrifuge. C’est dans cette phase de développement que s’inscrit ce travail de thèse. L’objectif est de réaliser un outil de pré-dimensionnement permettant de modéliser l’endommagement des guidages d’un pendule centrifuge. Une première étude expérimentale présente la faisabilité du suivi du système mécanique par l’utilisation de l’imagerie dynamique. Des essais de caractérisation matériaux des différents constituants du système viennent ensuite compléter l’étude. Ce travail expérimental réalisé à l’aide d’un tribomètre bi-disque permet d’obtenir les lois de frottements en fonction du taux de glissement ainsi que leur sensibilité à l’état de surface, au traitement thermique et au chargement. Un modèle théorique de détermination des valeurs du glissement est ensuite proposé, permettant de prendre en compte les différentes géométries de pendules. Enfin, les perspectives d’industrialisation sont envisagées en proposant une étude paramétrique sur le système réel en vue de son dimensionnement ainsi qu’une étude d’endurance pour modéliser l’usure du système. / The development of more fuel efficient engines results in an increase in the vibration levels. To solve this, Valeo is developing a new system: the centrifugal pendulum. This PhD research thesis registered as a contribution to the system development phase. The objective is to realize a predimensioning tool in order to model the wear of a centrifugal pendulum. A first experimental study shows the feasibility of monitoring the mechanical system through the use of dynamic imaging. Materials characterization tests of the various system components complete the study. The experimental work carried out using a twin-disc tribometer provides the friction laws versus sliding rate and their sensitivity to surface condition, processing and loading. A theoretical model for determining sliding values is then proposed to take into account the different pendulum geometries. Finally, the perpectives of industrialization are considered with a parametric study on the real system for a sizing purpose and an endurance study to model the wear of the system.

Presented master's thesis is focused on the experimental research of the sanding parameters in order to improve adhesion in the contact between wheel and rail. Sanding is the application of the sanding material directly in the wheel/rail contact. It is still common, most effective and traditional way how to deal with low adhesion problem, which is mainly caused by environmental contaminants. Research is important for the better understanding of the sanding process and also provides data, which are necessary for it's optimization and efficiency improvement. Newly developed twin-disc machine was used to carry out the presented experimental research. The influence of common contaminants on the adhesion is investigated, considering various operating parameters. Different amount of the applied sand is used to increase adhesion in the contaminated contact at various slip and rolling speed. Results show, that there is the amount of the sand, from which no significant adhesion increase occur. Obtained findings and the results presented in this thesis will be used to optimize sanding system, which will contribute to reduce cost associated with sanding and low adhesion.

Swerea KIMAB is one of Europe’s leading institutes for metallic materials and excels in many different areas. KIMAB’s main advantage is its open internal structure where all groups and projects can share information and knowledge between the sections. After moving to new premises it was noted that the surface fatigue test rig that had been used had started to leak oil and was no longer suitable for new projects. Because surface fatigue testing will be of importance in the future for the development of new alloys that will replace existing alloys in for example gears, this thesis was created as a foundation for how a new test rig should be acquired.This thesis goal is to describe KIMAB’s requirements in a test rig and to do a market screening over existing solutions for test rigs. Thereafter a designed concept shall be developed for KIMAB’s specific requirements and describe how it should be made. These different parts will be the ground for how KIMAB should continue in the acquisition of a new rig.The base of the thesis is a literature study in surface fatigue, its mechanics and how these can be affected to give the desired test scenario. This information is used to make a market screening for suitable test rigs that fulfils the requirements. Thereafter a concept generation is made and evaluated during a meeting on KIMAB. The chosen concept will then be designed to be user friendly, robust and as reliable as possible.When the final concept is done and quotes from manufacturers have been gathered for most of the parts in the design, a time and cost estimation was made to give the reader the chance of deciding which alternative is the most suitable for KIMAB. This choice has to be made with regard to future projects and how the market will develop for the ordering of surface fatigue testing. / Swerea KIMAB är ett av Europas ledande institut för metalliska material med spetskompetens inom ett flertal områden. KIMAB’s stora fördel är dess öppna interna struktur där alla grupper och projekt kan dela information och kunskap emellan avdelningarna. Efter att KIMAB flyttade till nya lokaler uppmärksammades det att den kontaktutmattningsrigg de använt under flera år började läcka olja och inte längre var optimal för dagens projekt. Eftersom kontaktutmattning kommer att bli ett viktigare inslag i framtiden då nya legeringar kommer att ersätta befintliga i exempelvis kugghjul, så skapades detta examensjobb som en grund för hur en ny rigg skall införskaffas.Detta examensjobb har som mål att beskriva KIMAB’s behov i en testrigg samt att göra en marknadsundersökning efter befintliga riggar. Därefter skall ett förslag designas på hur en testrigg som är anpassas just för KIMAB’s behov skall kunna byggas. Dessa delar skall sedan ligga som grund för hur KIMAB skall gå vidare i införskaffandet av en ny rigg.Examensarbetets grund ligger i en litteraturstudie i kontaktutmattningsskador samt mekanismerna bakom dessa skador och hur de kan påverkas i ett test scenario. Denna kunskap användes för att undersöka marknaden efter lämpliga riggar som kan uppfylla kraven. Därefter skapades ett antal koncept som utvärderades under ett möte på KIMAB. Det koncept som valdes har därefter designats för att vara så användarvänligt och tillförlitligt som möjligt.När konceptet var färdigställt och prisuppgifter hämtats in på merparten av delarna så har en kostnads och tidskalkyl utförts för att låta läsaren avgöra vilket alternativ som passar bäst för KIMAB. Detta val måste baseras på framtida projekt och hur marknaden ser ut för beställning av kontaktutmattningsprover.

Environmentally adaptable grease (EAG) lubricants are essential in applications with loss lubrication due to their biodegradable nature. This is because the lubricants could be expelled into the environment during usage in some applications e.g., marine and mining applications. However, although this type of grease is sustainable to use, it also needs to bridge the performance gap it has with the mineral-based grease counterpart.  In this thesis project, a tribological evaluation comparison between the performance of EAGs and traditional mineral-based greases in large open gears is carried out. A twin disc tribometer is used to mimic the contact mechanisms of the test gears while being lubricated automatically by the grease samples through a syringe pump. For the experiments, the material surface of all the discs in the tribometer setup is steel while the different grease samples are tested for each setup. Two of the grease samples; UPL 04123 (NLGI 1.5) and UPL 04124 (NLGI 0.5) are fully formulated EAGs, while the third is a popular commercial mineral-based grease currently used in large open gears in the mining industry. An investigation of the wear of the discs used in each grease test is carried out using optical interferometry and a Scanning electron microscope (SEM). The wear volumes and wear rates are then analysed and compared to evaluate the performance of the grease samples. The wear results from the tribological characterisation using the twin disc are validated with the ISO 14635-3 standard on the FZG back-to-back test rig. Also, chemical characterisation of the unused and used grease is carried out using the advanced ATR-FTIR method to evaluate additive depletion and lastly an SEM-EDS analysis to confirm the presence of tribofilm on the surfaces of the disc samples. In conclusion, it is found that there is a correlation between the consistency of the grease sample and wear prevention; where the commercial grease with the least consistency performs best, followed by the 0.5G and lastly the 1.5G. Also, there are clear indications in the wear rates of the actions of extreme pressure additives activation at high contact pressures between the discs. The inadequacies of the ATR-FTIR and SEM-EDS methods to evaluate additives and tribofilm respectively are also discussed.

Gears are machine elements essential for mechanical transmission. Wear of gear teeth can causechanges in their profile geometry, causing vibration, noise, and subsequent gear failure. In this thesisproject, a twin disc tribometer has been used to mimic the actual Alfa Laval separator screw gearsystems. An investigation of the wear of different material pairs has been done using a twin disctribometer machine. In the twin disc tribometer, the material surface for one disc was bronze and thematerial for the counter disc surface was varied with steel of different types. Each bronze-steel pair wastested against different loading, lubricating and surface roughness conditions. For the wear tests, twodifferent loads, 75 N and 150 N and two different types of lubricants, Polyalphaolefin (PAO) andPolyalkylene Glycol (PAG) were taken. Wear tests were also done with the Applied Nano Surfaces(ANS) triboconditioning (TCG) steel disc samples which are surface treated to obtain a lower surfaceroughness. To obtain the wear volume and wear rate values the disc pairs were further analysed usinglaboratory equipment and computer software such as the digital microscope, optical interferometer andMountainsLab premium 9. Analytical calculations for minimum film thickness and thermally correctedminimum film thickness between the disc surfaces were obtained using the Dowson-Hamrock equationand Gupta formula, respectively. It has been found that the wear on the bronze disc is minimum if thecounter steel discs are Applied Nano Surfaces (ANS) of TCG 1 type followed by counter disc as casehardened steel, all of it at 75 N and with Polyalphaolefin (PAO) lubricant oil.

This master’s thesis is dedicated to the design of an experimental rig that allows investigation of causes for noise during tram’s passing of a track curve and the developement of means to mitigate this noise. The opening section of this thesis contains theoretical background for the tribological mechanics of wheel-rail contact with emphasis on the process of noise generation, followed by an overview of laboratory tst rigs with similar purpose. Design itself is centered around the implementation of the dynamic model of wheel-rail contact using real tram wheel. Resulting test rig allows measurement of the adhesion characteristic in tangential and lateral directions and recording of the generated noise while an angle of attack is set.

Une lubrification suffisante est essentielle au bon fonctionnement des mécanismes et/ou composants comme par exemple les paliers à roulement. Par contre, les lubrifiants contiennent souvent des débris d’usure ou des polluants extérieurs. Ces particules micrométriques peuvent pénétrer des contacts d’épaisseur inférieure au micromètre induisant des empruntes ou indents pouvant conduire à des endommagements irréversibles pour les surfaces en contact. L’objet de ce travail est l’étude du piégeage de polluants solides à l’aide de particules sphériques d’acier, d’un point de vue théorique, numérique et expérimental. Dans un premier temps, une étude phénoménologique a été proposée à l’aide d’une nouvelle méthode expérimentale basée sur la technique PIV combinée à un tribomètre bille/disque. Les trajectoires des polluants à l’entrée du contact ont pu ainsi être identifiées. En parallèle, un modèle numérique d’écoulement du lubrifiant a été développé pour permettre l’évaluation des conditions menant au piégeage ou non de particules. Finalement, des expériences sur une machine bi-disques en conditions de lubrification polluée contrôlée ont permis de valider les tendances observées pour le piégeage. Une première série de résultats a montré que le piégeage de contaminants est fortement dépendant du profil de vitesse du lubrifiant. Un taux de piégeage très hétérogène a été observé sur des contacts avec une ellipticité transverse à l’écoulement variable. De manière surprenante, malgré une augmentation de la largeur de contact, une forte diminution du nombre de particules piégées a été observée dans des contacts elliptiques. Il a été démontré que cette diminution pouvait être imputée à la présence d’importants reflux de lubrifiant dans les contacts elliptiques larges. L’étude de contacts hybrides, nitrure de silicium–acier, a montré une bonne résistance à l’indentation du nitrure de silicium. Il est à noter que les contacts hybrides présentent des niveaux de piégeage similaire à un contact tout acier. / Contact lubrication is essential in a wide range of mechanical systems like rolling element bearings (REBs). A minimum quantity of clean lubricant all along the bearing life is necessary but difficult to ensure. In fact, lubricants contain inevitably wear debris or external particles, like dust. Carried by the lubricant in the vicinity of elastohydrodynamic (EHD) contacts, particles can be entrapped with disastrous consequences for contacting surfaces. Entrapment of micrometric particles in submicrometric contacting gaps means irreversible damages for the surfaces. Damages weaken the surfaces and reduce significantly the REBs lifetime. The goal of this work is to analyze the critical particle entrainments in the contact inlet. Entrapment of steel spherical particles was investigated from the numerical and experimental point of view. Firstly, the phenomenology of entrapment was explored with a new experimental method based on Particle Image Velocimetry (PIV) technique installed on a tribometer. It enabled the evaluation of velocity profiles in the contact inlet and the tracking of particles within EHD contacts. Secondly, a numerical modelling of the inlet flow for EHD contacts, including the particle tracking, was developed. Finally, tests on a twin-disc machine with a controlled level of well-defined contamination were conducted to validate previous conclusions. A first set of results showed that particle entrapment is highly dependent on the lubricant velocity profile. Depending on contact geometry, from point to wide elliptical contacts, different entrapment probability were revealed. Surprisingly, increasing contact width with wide elliptical contacts leads to a drop of entrapped particles. It was demonstrated that this phenomenon is due to backflows occurring upstream from these contacts. Introducing a hybrid pair of contacting materials (silicon nitride–steel), dents on the surfaces due to entrapped particles were explored. It has been confirmed that silicon nitride surface offers a real ability to resist to indentation. It was also noticed that the entrapment probability for silicon nitride–steel contacts is equivalent to a steel–steel one.

This thesis work was conducted at Luleå University of Technology in collaboration with Sandvik Rock Tools. The aim of the work was to determine the influence of carbon content on the wear performance in carburized steel in the dry contact interface of threaded connections between drill rods. In order to investigate this, samples of drill rod steel were carburized to three different carbon concentrations and shot peened to replicate the production process of a drill rod. The samples were wear tested by utilizing a twin-disc wear tester with one disc rotating at 100 RPM and the other at 3000 RPM to mimic the operating conditions in the threaded connection between drill rods. The results was evaluated by wear rate, surface topography, hardness as well as optical analysis by light optical microscopy and scanning electron microscopy. The results show that an increased surface carbon content provide a decrease in wear rate and an increase in hardness in the surface layer that undergo microstructural changes due to the frictional heat and contact pressure during wear testing. The primary wear mechanisms were identified as plastic deformation, adhesive scratching and material removal through delamination.