De par leurs magnitudes élevées et leur potentiel tsunamigénique, les séismes qui se produisent en contexte de subduction présentent un risque majeur pour les villes côtières souvent densément peuplées. La compréhension de la géométrie et du fonctionnement des zones de failles associées à ces ruptures sismiques a donc fait l'objet de nombreuses recherches sismologiques et géologiques.L’objectif de cette thèse est centré sur la caractérisation des zones de failles paléo-sismiques traversant des formations ophiolitiques subductées puis exhumées en surface des continent et sur leur comparaison avec les zones sismogéniques actuelles. Elle s’appuie sur une approche multi-échelle faisant intervenir les outils de la géologie structurale, de la pétrographie microstructurale, de la minéralogie, de la géochimie ainsi que les données de la géophysique. Le cas de la Corse alpine, de par la présence de nombreuses pseudotachylytes (étant considérées comme des fossiles de séismes) mafiques et ultramafiques constitue un cas d’étude idéal.La rupture sismique dans la nappe du Cima di Gratera est matérialisée par des réseaux de pseudotachylytes parallèles ou à fort pendages situées de part et d’autre de la discontinuité tectonique séparant les unités ultramafiques et mafiques formant la nappe. Le système de faille est caractérisé par une cinématique vers l’ouest associée à la subduction de la plaque océanique liguro-piémontaise sous la plaque adriatique. Les analyses minéralogiques des microlites présentes dans les pseudotachylytes mafiques indiquent une formation des veines en contexte de pression et température du facies eclogite, correspondant à une profondeur comprise entre 60 et 70 km, soit le début de la zone de sismicité dite de profondeur intermédiaire. La géométrie du système de faille a également pu être comparée à des géométries observées via la géophysique au large du nord-est Japon et à des profondeurs similaires.A également été mis en lumière l’impact de la serpentinisation sur le caractère sismique / asismique des discontinuités tectoniques faisant intervenir des formations mafiques et ultramafiques. En effet, la fusion frictionnelle issue des ruptures sismiques et responsable de la formation des veines de pseudotachylytes n’a été observée que dans le cas où était mis en contact la péridotite fraiche ou faiblement serpentinisée et le métagabbro. Les contacts impliquant la serpentinite et le métagabbro n’en présentent jamais et peuvent donc être considérés comme asismiques. Au regard de l’épaisseur des réseaux de pseudotachylytes dans les masses de péridotite et de leur absence dans les serpentinites, les masses de péridotites peuvent donc être assimilées à des aspérités au sein même de la plaque plongeante. / By their high magnitude and their ability to generate tsunami, subduction earthquakes present a major risk for the high population density coastal cities. The understanding of the geometry and the functioning of these seismogenic fault zones was the subject of numerous seismogenic and geologic studies.The objective of this thesis is focus on the characterization of paleo-seismic fault zones cross-cutting subducted ophiolitic formation and exhumed on the continent surface, and their comparison with current seismogenic zones. This study is based on a multi-scale approach and involves structural geology, microstructural petrography, mineralogy, geochemistry and geophysics tools. The Alpine Corsica, by the presence of numerous mafic and ultramafic pseudotachylytes (considered as fossils of past earthquakes) can be considered as an ideal study case.The seismic rupture in the Cima di Gratera Nappe is materialized by pseudotachylyte networks parallel or with a steep dipping to the fault separating the mafic and ultramafic units. The fault system is characterized by a top-to-the-west kinematic associated to the Piemonte-Liguria oceanic plate subduction under the Adriatic plate. The mineralogical analyses of the mafic pseudotachylyte microlites indicate a formation under a pressure and temperature conditions of the eclogite metamorphic facies. These conditions are consistent with a depth between 60 and 70 km which correspond to the upper part of the intermediate-depth seismicity zone. The geometry of the fault system was also compared to some geometry observed by the geophysics in the NE Japan subduction zone and at similar depth.It was also highlighted the role of the serpentinization on the seismic / aseismic character of the fault involving the mafic and ultramafic formations. Indeed, frictional melting resulting from the seismic rupture responsible to the pseudotachylyte veins formation was only observed in the case where the fresh peridotite or weakly serpentinized peridotite is in contact with the metagabbro. By opposition, the deformed zones involving the serpentinite and the metagabbro never show any pseudotachylyte and can be considered as aseismic. Considering the thickness and the polyphaser character of the pseudotachylyte networks and their absence in the serpentinite, the peridotite masses can be considered as asperities within the plate itself.

This thesis investigates the effect of scale on themorphology, mechanics and transmissivity of single rockfractures using both laboratory and in-situ experiments, aswell as numerical simulations. Using a laboratory 3D laserscanner, the surface topography of a large silicon-rubberfracture replica of size 1m x 1m, as well as the topography ofboth surfaces of several high-strength concrete fracturereplicas varying in size from 50mmx50mm to 200mm x 200mm, werescanned. A geodetic Total Station and an in-situ 3D laser radarwere also utilized to scan the surface topography of a largenatural road-cut rock face of size 20m x 15m in the field. Thisdigital characterization of the fracture samples was then usedto investigate the scale dependency of the three dimensionalmorphology of the fractures using a fractal approach. Thefractal parameters of the surface roughness of all fracturesamples, including the geometrical aperture of the concretefracture samples, were obtained using the Roughness-Lengthmethod. The results obtained from the fractal characterization ofthe surface roughness of the fracture samples show that bothfractal dimension, D, and amplitude parameter, A, for aself-affine surface are scale-dependent, heterogeneous andanisotropic, and their values generally decrease withincreasing size of the sample. However, this scale-dependencyis limited to a certain size—defined as the stationaritythreshold, where the surface roughness parameters of thefracture samples remain essentially constant beyond thisstationarity threshold. The surface roughness and thegeometrical aperture of the tested concrete fracture replicasin this study did not reach stationarity due to the structuralnon-stationarity of their surface at small scales. Although theaperture histogram of the fractures was almost independent ofthe sample size, below their stationarity threshold both theHurst exponent, Hb, and aperture proportionality constant, Gb,decrease on increasing the sample sizes. To investigate the scale effect on the mechanical propertiesof single rock fractures, several normal loading and directshear tests were performed on the concrete fracture replicassubjected to different normal stresses under Constant NormalLoad (CNL) conditions. The results showed that both normal andshear stiffnesses, as well as the shear strength parameters ofthe fracture samples, decrease on increasing the sample size.It was observed that the structural non-stationarity of surfaceroughness largely controls the contact areas and damage zoneson the fracture surfaces as related to the direction of theshearing. The aperture maps of the concrete fracture replicas ofvarying size and at different shear displacements, obtainedfrom numerical simulation of the aperture evolution duringshearing using their digitized surfaces, were used toinvestigate the effect of scale on the transmissivity of thesingle rock fractures. A FEM code was utilized to numericallysimulate the fluid flow though the single rock fractures ofvarying size. The results showed that flow rate not onlyincreases on increasing the sample size, but also significantlyincreases in the direction perpendicular to the shearing, dueto the anisotropic roughness of the fractures. <b>Key words:</b>Anisotropy, Aperture, Asperity degradation,Contact area, Finite Element Method (FEM), Flow analysis,Fractals, Fracture morphology, Heterogeneity,Stress-deformation, Surface roughness, Roughness-Length method,Scale dependency, Stationarity, Transmissivity, 3D laserscanner.

<p>This thesis investigates the effect of scale on themorphology, mechanics and transmissivity of single rockfractures using both laboratory and in-situ experiments, aswell as numerical simulations. Using a laboratory 3D laserscanner, the surface topography of a large silicon-rubberfracture replica of size 1m x 1m, as well as the topography ofboth surfaces of several high-strength concrete fracturereplicas varying in size from 50mmx50mm to 200mm x 200mm, werescanned. A geodetic Total Station and an in-situ 3D laser radarwere also utilized to scan the surface topography of a largenatural road-cut rock face of size 20m x 15m in the field. Thisdigital characterization of the fracture samples was then usedto investigate the scale dependency of the three dimensionalmorphology of the fractures using a fractal approach. Thefractal parameters of the surface roughness of all fracturesamples, including the geometrical aperture of the concretefracture samples, were obtained using the Roughness-Lengthmethod.</p><p>The results obtained from the fractal characterization ofthe surface roughness of the fracture samples show that bothfractal dimension, D, and amplitude parameter, A, for aself-affine surface are scale-dependent, heterogeneous andanisotropic, and their values generally decrease withincreasing size of the sample. However, this scale-dependencyis limited to a certain size—defined as the stationaritythreshold, where the surface roughness parameters of thefracture samples remain essentially constant beyond thisstationarity threshold. The surface roughness and thegeometrical aperture of the tested concrete fracture replicasin this study did not reach stationarity due to the structuralnon-stationarity of their surface at small scales. Although theaperture histogram of the fractures was almost independent ofthe sample size, below their stationarity threshold both theHurst exponent, Hb, and aperture proportionality constant, Gb,decrease on increasing the sample sizes.</p><p>To investigate the scale effect on the mechanical propertiesof single rock fractures, several normal loading and directshear tests were performed on the concrete fracture replicassubjected to different normal stresses under Constant NormalLoad (CNL) conditions. The results showed that both normal andshear stiffnesses, as well as the shear strength parameters ofthe fracture samples, decrease on increasing the sample size.It was observed that the structural non-stationarity of surfaceroughness largely controls the contact areas and damage zoneson the fracture surfaces as related to the direction of theshearing.</p><p>The aperture maps of the concrete fracture replicas ofvarying size and at different shear displacements, obtainedfrom numerical simulation of the aperture evolution duringshearing using their digitized surfaces, were used toinvestigate the effect of scale on the transmissivity of thesingle rock fractures. A FEM code was utilized to numericallysimulate the fluid flow though the single rock fractures ofvarying size. The results showed that flow rate not onlyincreases on increasing the sample size, but also significantlyincreases in the direction perpendicular to the shearing, dueto the anisotropic roughness of the fractures.</p><p><b>Key words:</b>Anisotropy, Aperture, Asperity degradation,Contact area, Finite Element Method (FEM), Flow analysis,Fractals, Fracture morphology, Heterogeneity,Stress-deformation, Surface roughness, Roughness-Length method,Scale dependency, Stationarity, Transmissivity, 3D laserscanner.</p>

Journal bearings are being used in various locations of an internal combustion engine. They contribute to a large portion of total engine friction and lowering it means a significant contribution to CO2 reduction. Operating under heavy loads, journal bearings are often subject to mixed regime of lubrication where a part of bearing load is carried by asperities. This necessitates accurate modelling of asperities contact in order to get more realistic predication of friction losses in journal bearings contact. The evaluation method at Scania couples 3D confocal measurement of bearings’ surface roughness to a Multi-body Dynamic Analysis of journal bearings lubrication utilizing AVL EXCITE. During running-in, asperity peaks are reduced due to wear caused by metal-to-metal contact resulting in change of bearing surface profile and different contact zones in axial and circumferential direction. The aim of this thesis is to include these different contact zones and run-in wear profile of the bearing to the existing evaluation method at Scania to simulate run-in effects more precisely. Surface measurements were made on a run-in big end bearing surface at edges, center and region after oil hole. From these measurements, using the existing Local Scale Model at Scania, asperity pressure curve and flow factors were obtained, which were used to perform AVL EXCITE big end bearing simulations with multiple surface contact patches. The results show that the inclusion of multiple surface patches and run-in wear profile lead to a significant change in distribution and also magnitude of bearing performance parameters e.g. pressure, friction losses, clearance height. / Glidlager är en av de mest använda komponenterna i motorer. De bidrar till en stor del av motorns totala friktion och en minskning av denna bidrar i hög grad till minskade utsläpp av CO2. Glidlager som arbetar under hög last utsätts ofta för blandfilmssmörjning där en del av lasten bärs av mekanisk kontakt mellan ytornas asperiteter. Detta kräver en noggrann modellering av asperitetskontakter för att få en realistisk prediktion av friktionsförluster i glidlager.Utvärderingsmetoden på Scania kopplar ihop 3D-mätning av lagrets ytfinhet i ett konfokalmikroskåp med en dynamisk tribologiberäkning i MBS-programvaran (Multi Body Simulation) AVL Excite.Under inkörning nöts asperiteterna ner på grund av metallkontakten mellan ytorna vilket påverkar lagerytans profil och ger olika kontaktzoner i axiell och periferiell riktning.Syftet med examensarbetet är att inkludera de olika kontaktzonerna och lagrets profil efter inkörning i Scanias befintliga utvärderingsmetod i syfte att noggrannare kunna simulera inkörning av lagren.Ytfinhetsmätningar utfördes med ett konfoklamikroskop på ett inkört vevlager vid kanterna, i mitten och i närheten av oljehålet.Med hjälp av dessa mätningar och en av Scanias befintliga kontaktmodeller beräknades asperitetstryck och flödesfaktorer vilka användes för att utföra vevlagerberäkningar i AVL Excite med olika kontaktegenskaper i olika regioner.Resultaten visar att införandet av regioner på lagerytan med olika lokala kontaktegenskaper och lagerprofil efter inkörning ger en signifikant förändring av såväl storleken som fördelningen av olika lagerresultat såsom till exempel lagertryck, friktionsförluster och oljefilmstjocklek.

Afin d’améliorer la durée de vie des micro-relais MEMS ohmiques, plusieurs traitements de surface de films minces d’or sont réalisés pour augmenter leur dureté tout en conservant une résistance électrique de contact faible.Les revêtements ultrafins de ruthénium (20 à 100 nm) déposés sur l’or augmentent la dureté des surfaces de contact d’un facteur 15. L’implantation ionique de bore ou d’azote (3,5 ppm à 10 % atomique) à une profondeur de 100 nm dans le film mince d’or permet d’atteindre un gain en dureté de 75%. Le contrôle (AFM, EBSD et DRX) de la microstructure induite met en évidence le durcissement par solution solide par insertion. Mais au-delà de 1% atomique, les atomes d’azote quittent le réseau cristallin de l’or pour former des précipités de nitrure d’or.L’analyse AFM (rugosité et diamètre) des empreintes résiduelles (quelques μm²) réalisées par nano-indentation sphérique, imitant le cyclage et le fluage des surfaces de contact de ces MEMS, démontre l’apport de ces traitements de surface. De plus, leurs résistances électriques de contact, mesurées par nano-indentation instrumentée reproduisant un micro-contact identique à un dispositif réel, sont similaires à celle de l’or pur.La modélisation discrète mécanique du contact rugueux est ajustée à la mesure de la déformation mécanique de nano-rugosités en comparant les relevés topographiques réalisés par AFM avant et après nano-indentation sphérique. La comparaison entre la modélisation et la mesure de la résistance électrique de contact indique que pour les gammes de force utilisées dans les micro-relais MEMS (inférieure au mN), seule une fraction allant de 2% à 9% de la surface de contact réelle est conductrice. / Ohmic MEMS switches made by gold thin films are promising devices but their mechanical contacts are one of the critical concerns for enhancing reliability. For this reason, surface processes are investigated in this work to improve both mechanical and electrical contact resistance (ECR) of MEMS gold contacts. Ruthenium ultra-thin films (20 to 100 nm) deposited on a top of gold layer increase surface hardness by a factor of fifteen. In parallel, surface implantations of both boron (<10% atomic) or nitrogen (<0.1% atomic) into gold reveals a solid solution hardening by insertion, thus increasing the hardness of initial film by about 75% and 25%, respectively. Notably, above 0.1% atomic of nitrogen, atoms precipitate from the tetra or octahedral sites of gold inducing a decrease of hardness.Static and multi load/unload spherical nano-indentation are performed on treated gold thin films to simulate the mechanical actuation of ohmic MEMS switches. Analysis of residual imprints (about few µm²) from treated surface exhibits both minimal local deformation and adhesion forces that reduce stiction probability. In-situ measurement of ECR for treated gold by instrumented nano-indentation, reproducing the design of MEMS, is in the same range of pure gold-to-gold configuration.A new mechanical discrete model of rough contact is introduced, confronted and validated to the experimental mechanical surface deformation obtained by comparison of AFM images before and after spherical nano-indentation. An electrical discrete model is added and fitted to the ECR measurements. In ohmic MEMS switch load range (< 1 mN), the conductive area is found to be about 2% to 9% of the real contact area.

This master’s thesis introduces a slide bearing analysis using the MBS software tool of FEV Virtual Engine, including real surface topography based on 3D roughness measurements. The first half of the thesis gives a brief overview about gasoline combustion engines, slide bearing usage in engines, slide bearing construction and about essential approaches for the characterization of elasto-hydrodynamic behavior. In the second half, the process of model building, rough surface measurement and preparation of analyses are described. At the end of this thesis, the results of the analyses are shown and discussed.