Polymers as construction material are common in the industry. Although more recently the use of polymer composites in more demanding applications has increased, requiring more of them mechanically, tribologically and thermally. To enhance the properties various fillers are used, from common glass fibers to more advanced nanoparticles. For this study three types of base polymers have been studied: poly-amide (PA), poly-phenylene-sulphide (PPS) and poly-ether-ether-ketone (PEEK). They have been filled with glass fibers, carbon fibers, poly-tetra-fluoro-ethylene (PTFE), graphite and thermally conductive modifier in various combinations. Fibers are used to increase the mechanical properties, PTFE and graphite are added as lubricating additives to reduce the friction, and the thermally conductive modifier to increase the thermal conductivity. Five general groups of polymer composites were studied. Pure PEEK PPS, PA and PEEK filled with fibers PPS, PA and PEEK filled with fibers and lubricating additives PA filled with lubricating additives PEEK filled with fibers and additives for lubrication and thermal conductivity The polymer composites have been tribologically tested in a reciprocating sliding test set-up. Friction, wear and surface damage have been studied. Three types of counter surfaces have been used: ball bearing steel balls, stainless steel cylinders and anodized aluminum cylinders. Load, surface temperature of the polymer composites and number of cycles were varied to study any changes in friction and wear. The wear marks on the polymer composites were studied using an SEM. Cross sections of some tested samples were prepared to study any subsurface damage. From the tests the polymer composites showed similarities in friction. Lubricating additives gave lower friction, often around 0.05-0.15, while pure and only reinforced gave higher, often around 0.4-0.5. The wear was also less for polymer composites with lubricating additives. There was no clear influence of temperature but for most tests an increase in temperature gave lower friction. The only influence of load was that higher load gave wider wear tracks. Since no cross sections were prepared to compare subsurface damage due to different loads there might be a possibility that there were some differences below the surface as well. Otherwise cross sections showed that polymer composites with only fibers had cracks and cracked fibers below the surface due to the high stresses the polymer composite had been subjected to. With lubricating additives there was no large subsurface damage and it seems as if the lubricating additives formed a protective tribofilm in the wear track, giving both lower friction and wear. The presence of such a tribofilm was confirmed by XPS analysis that showed a surface layer containing F from PTFE. The conclusions are that the tribological properties of a polymer composite are strongly dependent on its fillers. Lubricating additives form a tribofilm that lowers friction and wear. Elevated temperatures might drastically change the tribological behavior of a polymer composite why it is important to do tests at higher temperatures. Cross sections can give information about subsurface damage and might help to understand the wear mechanisms and deformation of polymer composites better. More microscopy and mechanism studies are required in order to further understand the tribological behavior of polymer composites.

With ever shorter development times and market demands on overall system performance such as efficiency, reliability and low maintenance, accurate predictive tools are necessary and gear drives prove to be no exception. All these characteristics have an impact on a process which has remained a riddle: running-in. Even though no consensus on a definition of this phenomena is readily available, this thesis examines efficiency, surface roughness and simulation through the optics of running-in. Geared transmissions are known for their formidable efficiency and their extreme reliability. However, with an ever increasing power density, the ability to accurately predict mesh losses becomes of utmost importance. The accurate quantification of bearing losses as well as efficiency of ground and superfinished gears under dip lubrication are examined with respect to running-in. Results show a considerable influence on the calculation of gear mesh losses originating from which bearing loss model is chosen. Furthermore, when a larger running-in load is used on ground gears, an increase in efficiency can be observed during working operation, while for superfinished no significant changes are found. These efficiency/frictional changes are also shown to occur in the initial cycles of the running-in phase. From a surface transformation point of view running-in is shown to be a reduction of asperity tips in case hardened ground gears, while in superfinished gears no changes were seen. These gear surface changes were measured with a novel method with a surface profilometer in-situ before, after running-in and after efficiency testing. Results also show that such changes in ground gear roughness profile occur during the very initial cycles. In order to predict running-in, a simulation method was developed. Such method utilizes a 2D surface integral method to simulate contact between rough surfaces, but requires the use of surface hardness and an accurate lower cutoff wavelength. This cutoff wavelength proved to play a pivotal role in determining an accurate contact pressure at the proper level of granularity, hence a well defined real contact area. The predicted and measured run-in surfaces are compared and are found to be in accordance with each other. / <p>QC 20170928</p>

La rhéologie du béton est un facteur d'influence direct sur la relation entre la pression de pompage et le débit. La rhéologie appliquée au béton est souvent caractérisée par une loi rhéologique à l'état stationnaire (indépendant du temps). Il s'agit d'un domaine assez pointu concernant principalement l'évolution de la contrainte de cisaillement en fonction du taux de cisaillement. Cette évolution du béton traditionnel est souvent caractérisée par le modèle de Bingham alors que pour un béton auto plaçant dont le rapport E/L est faible, l'évolution peut devenir non linéaire et peut suivre le modèle de Bingham modifié ou Herschel-Bulkley pour un fluide rhéo-épaississant. Pour ces modèles, on parle souvent d'un seuil de cisaillement au-delà duquel le béton commence à s'écouler, d'un indice de consistance (et un indice de puissance pour le cas d'une relation non linéaire) qui décrit l'intensité de l'évolution. En conséquence, la relation entre la pression et le débit peut être linéaire ou non linéaire en fonction du type du béton pompé. Comme les paramètres rhéologiques d'un béton participent directement à la prédiction de la pression de pompage, la mesure de ces paramètres fait l'objet un travail très exigeant au niveau de la précision.Comme les paramètres rhéologiques d'un béton ne sont pas des grandeurs physiques directement mesurables, les rhéomètres développés pour le béton frais ne sont capables de délivrer ces paramètres qu'à travers des mesures des autres grandeurs physiques de base comme la vitesse, le couple, la pression. Ensuite, plusieurs méthodes peuvent être appliquées pour reconvertir les grandeurs mesurées. Ces méthodes sont appelées la résolution du problème inverse. La méthode la plus efficace pour résoudre (ou confirmer la résolution du) le problème inverse concerne la calibration du rhéomètre avec des matériaux dont les propriétés rhéologiques sont connues. Plus le nombre de matériau utilisé pour la calibration est grand, plus la précision est meilleure. Cependant, pour les matériaux cimentaire, le nombre de matériau nécessaire pour bien couvrir les plages de valeurs des paramètres rhéologique est de l'ordre de quelques centaines de matériau. Cela demande un travail expérimental énorme et non rentable. Cependant, à la place de réaliser cette calibration expérimentalement, il est tout à fait possible de la réaliser en faisant des simulations numériques. Ces travaux numériques font partie du deuxième chapitre de la thèse.En complément de la rhéologie, la tribologie du béton est aussi un facteur déterminant du pompage. La tribologie permet de caractériser le comportement du béton à l'interface avec la paroi de la tuyauterie. Pour le cas de béton traditionnel dont le seuil de cisaillement est très important, l'écoulement du béton est dominé par l'effet de glissement du bloc de béton sur une couche limite de comportement lubrifiant. La couche limite est uniquement créée quand il y a une contrainte de cisaillement entre le béton et la paroi. Ce phénomène est présumé être la conséquence de la combinaison des trois phénomènes: l'effet géométrique de la paroi, la rupture structurelle interne et la ségrégation dynamique. Tous ces effets entrainent une diminution de la viscosité du matériau pompé sur une distance de quelques millimètres à la paroi. En conséquence, un écoulement non homogène est formé. Une vitesse de glissement à la paroi s'additionne à la vitesse engendrée par le cisaillement.Afin de caractériser le comportement du béton à la paroi, la tribométrie du béton voit le jour. Cela s'effectue avec les tribomètres qui simulent le mouvement relatif entre le béton et la paroi. Grace au mouvement, pour les bétons traditionnels dont le seuil de cisaillement est élevé, uniquement la couche limite est cisaillée mais pas le béton. Les paramètres délivrés sont un seuil d'interface, une constante visqueuse. Ces deux grandeurs permettent d'établir une relation linéaire entre la contrainte de cisaillement à l'interf / The rheological properties of concrete are significantly influencing the relation between pumping pressure and discharge rate. The concrete rheology is often characterized by a rheological law in stationary conditions (time independent), giving the evolution of shear stresses as a function of shear rate. In case of traditional concrete, this evolution is typically described by a Bingham model, while for a self-compacting concrete with low water/powder ratio, the evolution often becomes non-linear and can be described by a modified Bingham or Herschel-Bulkley model, considering shear-thickening. In these models, a critical shear stress is typically considered above which the concrete starts to flow. Furthermore, a consistency parameter is considered (and in case of non-linear behavior also an index) to describe the intensity of the evolution. As a consequence, the relation between pressure and discharge rate can be linear or non-linear, depending on the concrete pumped. As the rheological parameters of the concrete are directly relevant for the prediction of the pumping pressure, the accurate measurement of these parameters is a challenging task.As the rheological properties of concrete cannot be directly measured as a physical quantity, concrete rheometers can only be used to determine the rheological parameters in an indirect way, by measuring other physical values like speed, couple or pressure. Different methods can be applied in order to convert the measured physical values to obtain the rheological properties. The most direct method consist of calibrating the rheometers by testing materials with known rheological parameters. A higher precision in this approach can be obtained by testing a higher number of known materials. However, in order to cover the whole range of rheological properties of concrete, a very high number of known materials would have to be tested, which would thus become very cumbersome. Instead of performing this calibration in an experimental way, it can be done in a numerical way. This kind of numerical calibration is the topic of chapter 2 of the doctoral thesis.Besides the rheology of the concrete, tribology is also an important factor determining the pumping characteristics. Tribology enables to characterize the behavior of concrete in the interface with the surface of the pumping pipe. For traditional concrete with high yield stress, the flow of concrete in the pumping pipe is dominated by the slip layer or lubrication layer near the surface, while the bulk of the concrete is flowing as a plug. This slip layer can only be formed due to shear stresses in this area, and is considered to be the consequence of three phenomenons: geometrical wall effect, structural breakdown, and dynamic segregation. These phenomenons induce a reduction of the viscosity of the concrete within a layer of a few millimeter near the surface of the pumping pipe. As a result, a non-homogeneous flow is induced. Due to the occurrence of the slip layer, an additional speed component is added to the speed profile already induced by shear of the concrete.In order to characterize the concrete behavior near the surface, tribometers are being used, simulating the relative movement between concrete and the surface. In case of traditional concrete, with high yield stress, due to the relative movement only the slip layer is sheared, while the bulk concrete is not sheared. In this case, the use of tribometers results in a yield stress and a viscous constant of the slip layer. These two parameters enable to define a linear relation between shear stress and shear rate in the interface. Meanwhile, in case of self-compacting concrete, the concrete is also sheared, leading to very complicated tribology measurements. For this reason, it is very difficult to characterize the behavior of self-compacting concrete near the interface by means of a tribometer. This situations complicates the prediction of the relation between pumping pressure

Ces travaux de thèse concernent l'étude du contact à grande vitesse pouvant intervenir entre le pied de l'aube et l'alvéole du disque (tous deux en Ti6Al4V) de la soufflante du turboréacteur CFM56. Le comportement et les modes d'endommagement associés à ce type d'événements restent méconnus et peu traités dans la littérature. L'utilisation d'un tribomètre spécifique adapté sur un banc balistique, d'un thermocouple feuille-pièce et de modélisations numériques (éléments finis) ont permis d'étudier les liens existants entre vitesse, pression, température et efforts de frottement. Les endommagements induits ont ensuite été analysés en étudiant l'usure et l'évolution de la microstructure en sous surface (MEB, Imagerie 3D et EBSD). Une modélisation semi-analytique basée sur le cisaillement adiabatique des aspérités a été développée pour étudier l'évolution de la taille de la surface réelle de contact. En associant ce modèle à deux essais expérimentaux, des enveloppes inférieures et supérieures de l'évolution du coefficient de frottement pour une large gamme de vitesse de glissement ont été calculées. Ce travail de thèse est le fruit d'une collaboration entre la société Snemca, le LaBPS (Laboratoire de mécanique, Biomécanique, Polymères et Structure) et le LEM3 (Laboratoire d'étude des Microstructures et de Mécanique des Matériaux) / In case of exceptional events in aircraft engines (bird ingestion or blade disassembly), blade motions induce sliding at the interlock between the blade root and the slot of the fan rotor. The interface then undergoes quasi-instantaneous sliding under high normal pressure. This thesis work was initiated to investigate this phenomena and deals therefore with extreme sliding interactions for a Ti6Al4V tribopair (aircraft engine CFM56). Interface behavior and wear modes associated to these extreme thermomechanical loads remain poorly studied in literature. Links between velocity, pressure, temperature and friction force have been investigated by using a specific tribometer adapted on a ballistic bench, a foil-workpiece thermocouple and finite elements analysis. Induced damage were then analyzed by studying wear and microstructure evolutions (SEM, nanotomography and EBSD). A semi-analytical model, based on adiabatic shearing of asperities, has been proposed to evaluate the evolution of the real area of contact. By associated the latter with two experimental tests, upper and lower estimations of the mean friction force for a large velocity range can be calculated. This work is the result of collaboration between aircraft manufacturer Snecma, the LaBPS (Laboratory of Mechanics, Biomechanics, Polymers and Structures) and the LEM3 (Laboratory of Microstructure and Mechanics of Materials)

Soot is a carbonaceous materials produced as a result of incomplete combustion of fuels (gasoline, diesel, etc). At the present level of automobile technology, emission of soot from combustion in diesel engine appears to be an inevitability. The disadvantage in the diesel combustion is that it is not homogeneous throughout the cylinder. So the fuel-air ratio cannot be maintained constant throughout the flame zone and hence rich combustion zone leads to the formation of soot. Diesel engine combustion processes produce a large amount of soot, which is one of the major pollutant emissions of the exhaust systems. The fraction of combustion particulate, which is soot, is often estimated by finding the insoluble portion of the particulate. Hydrocarbons or other available molecules may also condense on or beads orbed by soot depending on the surrounding conditions. Other particulate matter constituents include partially burned fuel/lubricant oil bound water, wear metal and fuel derived sulfate. In diesel engine lubrication, soot has long been recognized as the major contaminant that is detrimental to engine lubrication, particularly in friction and wear. Different techniques for soot abatement have been investigated by researchers from the field of combustion and fuel. In spite of the large numbers of investigations of soot formation conducted till date, there is relatively little quantitative information is available about the mechanisms and governing rate processes. Some of the studies focused on the combustion chemistry of soot formation while some emphasized on engine design. On the other hand comparatively a few research works are coming out from the tribological point of view. Considering that internal combustion engines play such an important role in industry, investigative research of the parametric influences of particle size, agglomeration, oil viscosity, additives and surfactant as well as chemistry and electrical properties of particles on wear as well as into the wear mechanisms have not perhaps been as extensive as it is detrimental. Existence of a large numbers of variables in tribological contacts makes the situation very complex and difficult to analyze it quantitatively. In this complex scenario, where many opposed effects are playing their roles in soot tribology, the influence of the physical, structural and mechanical properties of soot on engine tribology has limited attention. We focus our study on one of the end effects of engine soot; friction and wear of the engine components. Since a diesel engine is not particularly suitable for use in a laboratory study of the fundamental processes and parameters of combustion due to its inherent difficulties on control and safety as well as data analysis uncertainty, so the most useful studies of soot fundamentals have emerged from studies of processes which have used simplified environments such as diffusion flames. We focus on soot tribology in steel-on-steel interaction in the presence of soot material suspended in relatively simple paraffinic hydrocarbons, hexadecane; with and without an additive. The physical, structural, chemical and mechanical properties of the particle and their changes as a function of tribological parameters are monitored throughout this study. Three type of soot are used in this work. Firstly, commercial grade carbon blacks has been used as soot simulant. Secondly, to enable controlled variations of the physical, mechanical, chemical and geometrical parameters of the particles, soot is generated in-situ by burning ethylene gas and the particles are extracted thermophoretically from different thermal zones of the flame. Thirdly, to establish the validity of the study, two types of diesel soots are extracted from an engine and studied. The objective is to use such an understanding to elucidate the basic mechanisms of friction and wear in the presence of soot which may limit the performance of a diesel engine. From our study we find that these soots have widely different morphologies, crystallographic orders and reactivity. At tribological contact the soot agglomerates fragment to primary level particles. The physical and chemical properties of such particles determine the friction between and wear of mating components. If the soot is strongly graphitic, the friction and wear are moderate. If the soot is made of chemically active organic groups, the friction and wear are high. The hardness, friction and resistance to material removal of the soot collected near the flame tip and diesel soot are found to be high compared to the other types of soot. Besides, the high hardness, irregular primary particle shape, large inter-particle adhesion leading to agglomeration and more abrasive nature of diesel soot influence the metal wear adversely. This trend of soot tribology is profound when these soots are suitably dispersed in the oil by the addition of dispersants, in our case it is polyisobutylene succinimide. Different functional groups present on the soot surface play important role in defining the interaction between surrounding medium and contacts which, in turn define the contact conditions, particle/agglomerate behavior and soot tribology. Finally, agglomeration is simulated using the features of a dissipative particle dynamics package as the simulation technique. Simulations are performed on a sizeable number of particles to observe agglomeration behavior, on simple environment, in future which can be further extended.

The accuracy of rotordynamic analysis of aeroengine structures is typically limited by a trade-off between the capabilities and the computational cost of the squeeze-film damper (SFD) bearing model used. Identification techniques provide a means of efficiently implementing complex nonlinear bearing models in practical rotordynamic analysis; thus facilitating design optimisation of the SFD and the engine structure. This thesis considers both identification from advanced numerical models and identification from experimental tests. Identification from numerical models is essential at the design stage, where rapid simulation of the dynamic performance of a variety of designs is required. Experimental identification is useful to capture effects that are difficult to model (e.g. geometric imperfections). The main contributions of this thesis are: • The development of an identification technique using Chebyshev polynomial fits to identify the numerical solution of the incompressible Reynolds equation. The proposed method manipulates the Reynolds equation to allow efficient and accurate identification in the presence of cavitation, the feed-groove, feed-ports, end-plate seals and supply pressure. • The first-ever nonlinear dynamic analysis on a realistically sized twin-spool aeroengine model that fulfills the aim of taking into account the complexities of both structure and bearing model while allowing the analysis to be performed, in reasonable time frames, on a standard desktop computer. • The introduction and validation of a nonlinear SFD identification technique that uses neural networks trained from experimental data to reproduce the input-output function governing a real SFD. Numerical solution of the Reynolds equation, using a finite difference (FD) formulation with appropriate boundary conditions, is presented. This provides the base data for the identification of the SFD via Chebyshev interpolation. The identified 'FD-Chebyshev' model is initially validated against the base (FD) model by application to a simple rotor-bearing system. The superiority of vibration prediction using the FD-Chebyshev model over simplified analytical SFD models is demonstrated by comparison with published experimental results. An enhanced FD-Chebyshev scheme is then implemented within the whole-engine analysis of a realistically sized representative twin-spool aeroengine model provided by a leading manufacturer. Use of the novel Chebyshev polynomial technique is repeatedly demonstrated to reduce computation times by a factor of 10 or more when compared to the basis (FD) model, with virtually no effect on the accuracy. Focus is then shifted to an empirical identification technique. Details of the commissioning of an identification test rig and its associated data acquisition system are presented. Finally, the empirical neural networks identification process for the force function of an SFD is presented and thoroughly validated. When used within the rotordynamic analysis of the test rig, the trained neural networks is shown to be capable of predicting complex nonlinear phenomena with remarkable accuracy. The results show that the neural networks are able to capture the effects of features that are difficult to model or peculiar to a given SFD.

Orientadores: Cecilia Amelia de Carvalho Zavaglia, Marcelo de Carvalho Reis / Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecanica / Made available in DSpace on 2018-08-04T01:42:37Z (GMT). No. of bitstreams: 1 Bavaresco_VanessaPetrilli_D.pdf: 14276021 bytes, checksum: d5ab24900afcc34fe160b1d9a55fa2bd (MD5) Previous issue date: 2004 / Resumo: O desenvolvimento de próteses articulares com superfície complacente, capaz de favorecer ou permitir a lubrificação entre os componentes das juntas artificiais, como acontece nas juntas naturais, vem despertando grande interesse visto que diminui o coeficiente de atrito entre as superfícies, favorecendo o deslizamento entre as mesmas e minimizando o desgaste. A proposta deste trabalho foi estudar e melhorar as propriedades mecânicas de hidrogéis poliméricos de poli (metacrilato de 2-hidroxietila) (pREMA) e poli (álcool vinílico) (PVA) reconhecidamente utilizados no estudo de reparadores da cartilagem articular natural. Para tanto foram obtidos copolímeros de pREMA e n-vinil pirrolidona (NVP) (polímero hidrofílico de reforço) variando-se a concentração de agente de reticulação e blendas de poliHEMA com o copolímero poli(metacrilato de metila-co-ácido acrílico) (75:25) enquanto que, os hidrogéis a base de poli (álcool vinílico) foram reticulados com radiação ionizante de feixe de elétrons. O estudo envolveu a caracterização térmica, mecânica e morfológica desses materiais bem como sua caracterização quanto ao desgaste em um equipamento do tipo PIN-ON-DISK com uma contra-superficie de metal em condições próximas à fisiológica com movimento relativo rotativo e, ainda, com movimento recíproco ou alternado / Abstract: There is an increasing interest in the development of soft layered articular prostheses, which favour sliding between components, as natural joints do, thus reducing contact stresses and wear. The purpose of this work was to characterize and improve the mechanical properties of poly (2-hydroxyethyl metacrylate) (pHEMA) and polyvinyl alcohol (PVA) hydrogels. These hydrogels are extensively studied for articular cartilage repair. Samples of pHEMA and n-vinyl pirrolidone (NVP) copolymers with different amounts of trimethylol propane trimethacrylate (TMPTMMA) crosslinking agent, and samples of pHEMA/poly (methyl metacrylate-co-acrylic acid) blends were prepared by thermal polymerization. Additionally, PVA based hydrogels were prepared by means of electron beam ionizing radiation. Hydrogel samples were characterized by indentation creep test, equilibrium water content (EWC) and Differential Scanning Calorimetry (DSC). The tribological characterization of hydrogels was performed under nearly looading physiological conditions at room temperature on a pin-on-disc equipment, Plint TE67, using a stainless steel 316L disc counter surface / Doutorado / Materiais e Processos de Fabricação / Mestre em Engenharia Mecânica

Orientador: Katia Lucchesi Cavalca / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecânica / Made available in DSpace on 2018-08-14T16:47:29Z (GMT). No. of bitstreams: 1 Nonato_Fabio_M.pdf: 2576321 bytes, checksum: 620be5d1e8be22816a88e01fd2596425 (MD5) Previous issue date: 2009 / Resumo: Com a necessidade da diminuição do tempo de projeto, a utilização de modelos computacionais para simulação de componentes mecânicos se torna rota obrigatória para se evitar excessivos testes físicos. Com base nesta premissa, se torna necessário estudar a dinâmica de componentes anteriormente considerados rígidos, como mancais de elementos rolantes, e assim conhecer sua influência sobre o sistema completo. Assim, utilizando um modelo por diferenças finitas em múltiplos níveis, foi avaliada a condição de lubrificação no contato em rolamentos sujeitos a lubrificação Elastohidrodinâmica (EHD) transiente. Desta forma foi possível caracterizar dinamicamente o contato, aproximando o filme de óleo a um conjunto de mola e amortecedor não lineares. Portanto introduz-se um elo flexível ao mancal, possibilitando a sua análise dinâmica como parte do sistema. / Abstract: With the need of time reduction on mechanical projects, the use of computational models for the analysis of mechanical components becomes mandatory in order to avoid excessive physical tests. Based on this assumption, is necessary to study the dynamic of previously assumed rigid components, as the rolling elements bearings, and thus knowing its influence on the complete system. Utilizing a multi-level finite difference method, the lubrication condition on the contact in bearings under Elastohydrodynamic (EHD) transient lubrication was evaluated. Therefore the dynamic characterization of the contact was possible, adjusting the oil film to a nonlinear spring-damper set. Hence a flexible joint is introduced in the bearing, making it possible its dynamic analyses as part of the system. / Mestrado / Mecanica dos Sólidos e Projeto Mecanico / Mestre em Engenharia Mecânica

The dissertation thesis deals with the lubricant film formation chemistry on hip implant material surfaces with synovial fluid components. Biochemical and tribological properties of synovial fluid after joint replacement are focused, precisely on the chemical composition of the formed lubricating film and chemical structural changes of the associated constituents under mechanical loading. Nevertheless, the synovial fluid components‘ chemical structural changes after the joint replacement are rarely addressed and require further attention. Including metal and ceramics, various combination implant materials were applied within the lubricants of synovial fluid constituents separately and different model synovial fluids to reveal the biochemical reactions and frictional coefficients for understanding the possible lubrication mechanism. Raman Spectroscopic technique is manifested as the most appropriate method to explain the biochemical behaviour of synovial fluid and chemisorption on the surface of the implant material. The method is depicted presenting two different studies focusing on the chemical structure of the synovial fluid film on the implant surface and frictional coefficient measurement of the contact pair within the artificial hip joint. This latest methodological precedent also facilitates to evaluate the chemical structural change of the synovial fluid due to the tribological activity in the hip prosthesis. The thesis expounds original results concerning biotribology to increase the depth of knowledge on joint replacement procedure and to enhance the longevity of the orthopaedic implantations.

No description available.