Neste trabalho, foram desenvolvidos e validados métodos qualitativos e quantitativos para o controle de qualidade de cefpiroma, antibiótico β-lactâmico de amplo espectro utilizado, principalmente, no tratamento de infecções graves e episódios febris em pacientes com neutropenia, na forma farmacêutica pó para solução injetável. A substância química de referência utilizada nas análises foi caracterizada por espectrofotometria no infravermelho e por espectroscopia de ressonância magnética nuclear. A análise qualitativa foi realizada por cromatografia em camada delgada, determinação da faixa de fusão, espectrofotometria nas regiões do ultravioleta e do infravermelho e cromatografia líquida de alta eficiência, possibilitando a identificação da amostra. A determinação quantitativa foi realizada através dos métodos: espectrofotometria no ultravioleta, cromatografia líquida de alta eficiência e ensaio microbiológico pelo método de difusão em ágar – cilindros em placas, delineamento 3 x 3. Os métodos propostos foram validados segundo guias oficiais e demonstraram ser específicos, lineares, precisos e exatos. Os resultados obtidos demonstraram não haver diferença significativa entre os métodos quando comparados estatisticamente pela análise de variância (ANOVA). Outro objetivo deste trabalho foi o estudo da estabilidade da cefpiroma na forma farmacêutica reconstituída com água para injetável. Os fatores de degradação avaliados foram temperatura (40 ºC) e luz (UVC – 254 nm). Os estudos acelerados de estabilidade demonstraram que a cinética de degradação térmica e fotoquímica foi de primeira ordem. Um produto de degradação térmica foi isolado e identificado, por ressonância magnética nuclear, espectrofometria no infravermelho e espectroscopia de massa, como sulfato de 6-7-diidro-5H-ciclopenta[b]piridinium. / The aim of this study was the development and validation of analytical methods to the determination of cefpirome in powder for injectable preparation and the stability study of the drug after reconstitution of the pharmaceutical dosage form with injectable water. Cefpirome is a fourth-generation cephalosporin active against a broad spectrum of gram-negative and gram-positive bacterial infections and its principal indication is in the treatment of patients’ septic shock or several sepsis. The substance used as reference standard in the analysis was characterized by infrared spectroscopy and nuclear magnetic resonance. The qualitative analysis was performed by thin layer chromatography, melting range determination, infrared and ultraviolet spectroscopy and high performance liquid chromatography, allowing the identification of samples. The quantitative determination was performed by ultraviolet spectrophotometry, high performance liquid chromatography and cylinder-plate microbiological assay (3 x 3). The proposed methods were validated following official guides and all of them demonstrated to be specific, linear, precise and accurate. The obtained results were analyzed by the ANOVA method and they are not statistically different. The degradation factors evaluated were the temperature (40 ºC) and light (UVC – 254 nm) and the accelerated stability demonstrated that the degradation kinetics from thermal and photo degradation were first-order reactions. A thermal degradation product was isolated and identified, by nuclear magnetic resonance, infrared spectroscopy and mass spectrometry, as 6-7-dihidro-5Hcyclopenta[ b]pyridinium sulfate.

O perigo geológico de escorregamentos é a probabilidade da ocorrência de eventos ou fenômenos desta natureza, induzidos ou não pela atividade humana que podem causar danos humanos, socioeconômicos e ambientais. A cartografia de perigos geológicos de escorregamentos é um importante instrumento para gestão dos territórios para Estados Nacionais, setor privado, ONGs, comunidades locais, organizações científicas, etc. O desenvolvimento da ciência e das técnicas fez surgir diversos métodos de avaliação de perigos de escorregamento. No presente trabalho, o método sintético e o método analítico foram comparados com base em Sistemas de Informação Geográfica (SIG), técnicas de geoprocessamento e modelagem de dados cartográficos. Os atributos utilizados, na forma de matrizes numéricas foram declividade do terreno, densidade de drenagem e de lineamentos, excedente hídrico e cobertura vegetal e uso da terra (índice NDVI). Por meio de procedimentos de álgebra de mapas foi obtido o índice de perigo e elaborados os mapas de perigo de escorregamento. No método analítico o mapa de perigo ficou com uma textura mais granulada e no método sintético aparentou uma textura mais homogênea. A comparação da medida de classes em m² dos métodos coincidiu em 92% na classe muito alto, 90% na classe alto, 89% na classe médio e 90% na classe baixo. Já na tabulação cruzada a porcentagem de intersecção foi de 50% para a classe muito alto, 41% para a classe alto, 52% para a classe médio e 68% para a classe baixo. Concluiu-se que ao invés de opostos, os métodos se mostram adequados para um uso complementar. / Geological hazard due landslides is the likelihood of occurrence of such events or phenomena, either induced or not by human activities that can cause human, social-economic or environmental loss. Landslide hazard maps are important tools for territory management among government, private sector, Non-Governmental Organizations (NGO), local communities and academy. The development of science and techniques brought about many methods for landslide assessment. This work aims to compare two approaches: the syntethic and analytical methods based on Geographical Information Systems (GIS), geoprocessing and cartographic data modeling. The used attributes, organised in numeric rasters were declivity, drainage and lineaments density, water excess and vegetation cover and land use (NDVI). Procedures of map algebra resulted in the Landslide Hazard Indexes, from which the hazard maps were generated. The maps were compared and validated across previous risk and suscetibility maps with high correlation results. It was concluded that rather than opposites both methods are suitable for an complementary use.

La durée de vie en fonctionnement des pièces mécaniques peut être augmentée par la présence de contraintes résiduelles de compression. Inhérentes à la plupart des procédés de fabrication, contraintes résiduelles jouent un rôle sur la tenue en service des éléments mécaniques. La connaissance et la maîtrise de ces contraintes résiduelles et des procédés associés sont donc fondamentales. La mise en place de méthodes numériques performantes pour prédire ces contraintes résiduelles permettra à terme d'éviter de nombreux et coûteux essais et d'étudier l'influence des principaux paramètres. Cette thèse présente le développement et l'application de méthodes de calcul semi analytiques (SA) à la modélisation de procédés mécaniques de mise en compression des surfaces. Les méthodes SA, initialement développées pour la simulation des contacts élasto-plastiques, ont l'avantage de temps de calcul très significativement réduits par rapport aux méthodes numériques conventionnelles. Cette méthode est d'abord utilisée pour la simulation d'un procédé connu sous le nom de galetage, avec un chargement de type contact roulant. Enfin elle est utilisée pour la simulation d'impacts uniques puis répétés, et les développements associés présentés. Le contact roulant entre deux massifs élasto-plastiques, sans considération du frottement, est d'abord étudié. L'influence de la plasticité et du type d'écrouissage (isotrope ou cinématique), de la géométrie des massifs en contact (sphéres ou ellipsoides) et du type de chargement (indentation ou roulement) sur la pression de contact et les déformations plastique sont analysés. La simulation d'impacts est ensuite abordée. La méthode développée est tout d'abord validée numériquement, puis confrontée à l'expérience. Trois matériaux ont été plus particulièrement étudiés : 316L, AA 7010, et l'Inconel 600. Les dimensions des impacts ainsi que les déformations générées, mesurées par stéréo corrélation sont utilisées pour valider expérimentalement la méthode. Le procédé de billage ultrasonore a été tout particulièrement étudié. Dans un premier temps nous nous sommes attachés à la décrire la cinématique des billes dans une chambre fermée, mises et maintenues en mouvement par une sonotrode. L'utilisation de formules analytiques pour l'estimation des coefficients de restitution, lors des nombreux chocs entre les billes ou avec les parois de la chambre, a permis d'affiner le calcul des vitesses moyennes d'impact en fonction des paramètres du procédé. La méthode SA est ensuite utilisée pour déterminer le champ de déformations plastiques induits par les impacts. Enfin une méthode de projection est proposée pour permettre in fine la prédiction des contraintes résiduelles pour des structures fines ou épaisses. / The life time of mechanical components can be increased by the presence of compressive residual stresses. Inherent to most production processes, residual stresses play a critical role on the mechanical parts behaviour. The knowledge and mastering of residual stresses and linked processes are thus fundamental. The development of efficient numerical methods to predict these residual stresses will allow to save costly experiments and to study the influence of the main parameters. This PhD presents the development and application of semi analytical methods (SAM) to the modelling of mechanical processes of compressive residual stress generation. The SAMs, initially developed for the simulation of elasto-plastic contacts, have the advantage of significantly low computation time compared to classical numerical methods. This method is first used to simulate the low plasticity burnishing process, with a rolling loading. Then, it is used for the simulation of impacts, first unique and then repeated. The frictionless rolling contact between two elasto-plastic bodies is first studied. The influence of plasticity, of the hardening model (isotropic or kinematic), of the geometry of the bodies in contact (spheres or ellipsoids) and of the loading type (indentation or rolling) on the contact pressure and plastic strains are analysed. Impacts simulation is then addressed. The developed method is first validated numerically then confronted to experimentations. Three materials have been particularly studied: 316L, AA 7010 and Inconel 600. The impacts dimensions and the generated strains, measured by digital image correlation, are used to validate experimentally the method. The ultrasonic shotpeening process has been specifically studied. The description of the kinematics of the shots put in movement by a sonotrode in a closed peening chamber has first been studied. The use of analytical formulae for the estimation of the coefficients of restitution, during the numerous impacts between shots and with the chamber’s walls, allowed refining the calculation of the average impact velocity as a function of the process parameters. The SAM is the used to determine the plastic strain field induced by the impacts. At last a projection method is proposed to finally determine the residual stress field in thick or thin structures.

This master’s thesis is focused on IP mobility support for mobile users and their devices in IPv6-based wireless networks. Then the Mobile IPv6 (MIPv6) protocol was proposed for this purpose and that is also the main objective of the thesis. This consists of several basic sections and is organized as follows: The first one deals with the overview of the function of Mobile IP, which enables the mobility of nodes around the Internet, without a change of their original IP address. Moreover there are introduced the primary differences between MIPv6 and its previous version – i.e., MIPv4, proposed for IPv4-based environment. The second chapter of the master’s thesis thereafter describes detailed information about all the most important mechanisms and features of Mobile IPv6 and this way tries to explain principles of its functioning. Further the thesis analyses some of proposed MIPv6 extensions – i.e., Hierarchical Mobile IPv6 (HMIPv6), Mobile IPv6 Fast Handover (FMIPv6) a Fast Handover for HMIPv6 (F-HMIPv6) protocols, and mainly aim at signaling process during the handover of a mobile node. In the last main section of the master’s thesis an analytical method to evaluate the performance of IPv6-based mobility management protocols was proposed. Subsequently, this method is applied on the protocols which were mentioned above and are studied the effects of various network parameters on the performance of these protocols.

The main object of this diploma thesis is solving problems concerning heat transfer in disposal cannister for spent nuclear fuel. In forepart possibilities of conceptual solving according of disposal cannister to particular states are reviwed. On the basis of this a variant of possible protect of a nuclear fuel repository in the Czech republic has been chosen for calculationof a simplified model. Second part is computational solving that was divided into two parts. The first deals with calculation of heat transfer in disposal canister and is done by an analytical method. In the second part is calculation is done by numerical model. In this way region in near surroundings of this model of disposal cannister is analysed. Last part those diploma thesis deals with design of the storage of spacing among disposal canisters as well as optimum placing in underground part of nuclear fuel repository.

<p>Pumped municipal solid waste landfill leachate samples (7 cells from a site in Nebraska, 4 cells from a site in Illinois) have been analyzed for 62 elements using Inductively Coupled Plasma-Optical Emission Spectroscopy (ICP-OES). A procedure for complete dissolution of solids in the leachate was developed. Complete dissolution aims to reduce material loss in filtration by eliminating the need for filtration, and frees materials entrapped in undissolved solids. The procedure uses centrifugation to separate solid phase matter from the raw sample to maximize the effect of acid, and uses Chloric, Nitric, Fluoric, and Boric acids with microwave digestion to achieve full dissolution. The dissolved solid fraction precipitates yttrium fluoride and some other metals due to over-solubility concentrations; the precipitate is recovered and redissolved for analysis. Platinum, (Post-) Transition, and Lanthanide group metals were positively detected in the landfill leachate. Individual metals from these groups were detected in either/both aqueous or/and solid phases: solid phase metals are usually at least one magnitude of concentration greater than liquid phase metals, unless the solid phase produced no detection of the metal where the liquid phase did. Noteworthy results are: in the solid phase; Al was quantified from 10 to 103 𝜇g/g of solid mass; Sc, Cr, Ti, and Cu were quantified in the solid phase from 1 to 50 𝜇g/g of solid mass; Zr and Eu were quantified from .5 to ~8 𝜇g/g of solid mass. In the liquid phase: Ti, Cr, Li, Cu, As, and Zr were quantified mostly between 10-2 to 10-1 𝜇g/g of liquid mass, but occasionally reach out of those bounds; Al, Sc, Pt, Co, and V were quantified mostly from 10-3 to 10-2 𝜇g/g of solid mass. Solid phase metals were positively detected with a minimum Limit of Detection (LOD) usually around 10-1 𝜇g/g of solid mass, including: In, Ge, Pb, Ru, Sb, Ta, Hf, Bi, Yb, La, Ti, Pd, Lu, Dy, and Tb. Liquid phase metals were positively detected with a minimum LOD usually around 10-5 𝜇g/g of liquid mass, including: Tm, Ge, Au, Pb, Sb, Ta, Hf, Sm, Nb, Ho, Ga, Bi, Yb, Pd, Er, and Cd.</p>

[pt] As ferramentas de perfilagem eletromagnética para poços e túneis têm sido objeto de interesse da engenharia por muitas décadas devido às suas aplicações para a exploração de petróleo. A fim de obter uma avaliação precisa de uma formação geofísica, uma ampla variedade de métodos de eletromagnetismo computacional foi desenvolvida. O alto custo em termos de recursos computacionais para o procedimento da discretização espacial é um ponto negativo desses métodos tradicionais. Esta pesquisa tem como objetivo explorar novas abordagens semianalíticas para analisar a propagação de campos eletromagnéticos em meios anisotrópicos compreendendo camadas planares. Apresentaremos uma formulação matemática para os campos eletromagnéticos de uma fonte solenoidal em termos de um somatório de autofunções modais. O método proposto permite a análise de cenários geofísicos análogos aos do Pré-Sal brasileiro, onde rochas carbonáticas de alta condutividade são predominantes. Além disso, o efeito das formações do pré e pós-sal nas ondas eletromagnéticas pode ser facilmente incorporadas no nosso modelo. Apresentaremos resultados numéricos de validação, que demonstram o potencial da abordagem proposta neste trabalho para modelar sensores geofísicos de forma computacionalmente robusta e eficiente. / [en] Electromagnetic well-logging tools have been subject of interest for many decades due to their applications in oil exploration. In order to obtain accurate formation evaluation, a wide variety of numerical methods have been developed on Computational Electromagnetics. The high cost in terms of computational time and resources of these methods for the spatial discretization procedure is a negative point of these traditional methods. In this work, we will explore new semi-analytical approaches to analyze the propagation of electromagnetic fields in anisotropic media comprising planar layers. We will present a mathematical formulation for the electromagnetic fields due to a solenoid source in terms of a sum of modal eigenfunctions. The proposed method allows the analysis of geophysical scenarios similar to those of the Brazilian Pre-Salt, where high conductivity carbonate rocks are predominant. In addition, the effect of pre- and post-salt formations on electromagnetic waves can be easily incorporated into our model. We will present numerical validation results, which demonstrate the potential of the approach proposed in this work to model geophysical sensors in a computationally robust and efficient way.

Le p-tert-octylphénol est un produit présent dans l’environnement et issu de la dégradation des alkylphénols éthoxylés. Ce composé a la capacité de se lier au récepteur œstrogénique et d’exercer ainsi un léger effet œstrogénique. Les objectifs de cette étude étaient de 1) développer une méthode d'identification de l'octylphénol dans le sang et les tissus à l'aide de la chromatographie en phase gazeuse jumelée à la spectrométrie de masse, 2) caractériser la toxicocinétique sanguine et tissulaire de l’octylphénol chez le rat Sprague-Dawley mâle et femelle et 3) développer un modèle toxicocinétique à base physiologique permettant de décrire la cinétique sanguine et tissulaire de l’octylphénol inchangé. Pour ce faire, des rats mâle et femelle Sprague-Dawley ont reçu des doses uniques d’octylphénol par les voies intraveineuse, orale et sous-cutanée. Deux autres groupes ont reçu des doses répétées d'octylphénol par voie orale pour une durée de 35 jours consécutifs pour les femelles ou 60 jours pour les mâles. Les concentrations sanguines et tissulaires d’octylphénol ont été mesurées à différents moments après administration à partir d’une méthode d’analyse développée dans nos laboratoires dans le cadre de ce projet. Les expériences impliquant des administrations uniques ont montré que les concentrations sanguines et tissulaires d'octylphénol étaient en général plus élevées chez les femelles que chez les mâles. Des expériences réalisées avec des microsomes hépatiques ont confirmé que ces différences étaient vraisemblablement reliées au métabolisme de l'octylphénol. Les expériences impliquant des administrations répétées ont montré qu'il n'y avait pas d'accumulation d'octylphénol dans l'organisme aux doses étudiées. Les résultats obtenus expérimentalement ont servi à développer et valider un modèle toxicocinétique à base physiologique. Ce modèle a permis de simuler adéquatement les concentrations sanguines et tissulaires d'octylphénol suite à des expositions intraveineuses, orales et sous-cutanées. En conclusion, cette étude a fourni des données essentielles sur la toxicocinétique de l'octylphénol. Ces données sont nécessaires pour établir la relation entre la dose externe et la dose interne et vont contribuer à une meilleure évaluation des risques liés à l'octylphénol. / p-tert-Octylphenol is a degradation product of alkylphenol ethoxylates that can be found in the environment. It has been reported to act as a weak estrogenic compound by binding to the estrogen receptor. This study was undertaken to 1) develop a sensitive method for the determination of octylphenol in blood and various tissues using gas chromatography coupled with detection by mass spectrometry, 2) characterize the blood and tissues toxicokinetics of octylphenol in male and female Sprague-Dawley rats and 3) develop a physiologically-based toxicokinetic model for octylphenol that can describe/predict unchanged blood and tissues octylphenol concentrations in rats. Male and female Sprague-Dawley rats were given a single dose of octylphenol either by oral gavage, intravenous injection or subcutaneous injection. In a repeated dosing experiment, rats were given octylphenol (oral) daily for 35 days (female) or 60 days (male). Blood and tissue samples were collected at various time following the onset of exposure and analyzed for octylphenol content using a method developed in our laboratory. These results showed that blood and tissues octylphenol concentrations were generally higher in female than male rats. Experiments done with rat liver microsomes confirmed that these differences were related to octylphenol metabolism. The results of the repeated exposure study indicate that there is no bioaccumulation of octylphenol at these exposure levels. A physiologically-based pharmacokinetic model for octylphenol was developed and validated using the data obtained in female and male rats. The model simulates adequately blood and tissues octylphenol concentrations following oral, intravenous or subcutaneous exposure. In conclusion, this study provided essential data on the toxicokinetics of octylphenol. These data are essential to predict the relationship between the internal and the external dose of octylphenol and will facilitate the risk assessment of octylphenol in humans.

De nombreux modèles numériques sont proposés dans la littérature en utilisant des méthodes d'éléments finis et d'éléments finis discrets pour étudier l'usure par frottement, ils incluent à peine l'effet des débris d'usure. Ces modèles étant coûteux en termes de calcul, simuler un grand nombre de cycles d'usure par frottement n'est pas réalisable dans la pratique. Une nouvelle méthodologie est proposée qui ne nécessite que des propriétés de matériau en vrac comme les coefficients de frottement / usure et utilise des méthodes semi-analytiques pour simuler l'usure par frottement avec des débris piégés. Dans cette approche, les débris sont supposés être attachés à l'une des surfaces pendant le processus de fretting. Les résultats obtenus à partir de cette approche ont été comparés avec des expériences de fretting. La méthode proposée permet de saisir la profondeur d'usure et la largeur des cicatrices, et les résultats sont très proches de ceux observés dans les expériences. L'assemblage des soupapes des moteurs à combustion subit une usure par frottement en raison d'un phénomène complexe impliquant une rigidité structurelle et une tribologie de contact. L'usure des soupapes a de nombreux effets néfastes sur les performances du moteur. Il provoque une récession de la soupape entraînant des changements dans les connexions du mécanisme d'entraînement de la soupape, ce qui perturbe l'ouverture et la fermeture des soupapes. Avec des normes d'émission strictes, l'utilisation de lubrifiant pour réduire la friction au contact est limitée. Si l'usure à travers la circonférence n'est pas uniforme, il y aura une fuite de gaz et le moteur donne moins de puissance. Il est nécessaire de bien comprendre la raison de l'usure des soupapes et de développer un modèle numérique capable de prédire l'usure par frottement de la soupape pour le nombre d'heures de fonctionnement donné. Des expériences ont été réalisées pour comprendre le mécanisme d'usure et calculer les coefficients d'usure qui peuvent être utilisés dans le modèle numérique. Un modèle d'usure numérique est construit qui capture la rigidité structurelle de l'ensemble de soupape et le mécanisme d'usure au contact du siège. / Many numerical models are proposed in the literature using finite element and finite discrete element methods to study fretting wear, they barely include the effect of wear debris. These models being computationally expensive, simulating large number of fretting wear cycles is not practically feasible. A new methodology is proposed which needs only bulk material properties like friction/wear coefficients and uses semi-analytical methods to simulate fretting wear with entrapped debris. In this approach, debris are assumed to be attached to one of the surfaces during the fretting process. The results obtained from this approach were compared with fretting experiments. The proposed method permits to capture the wear depth and scar width, and results are very close to that observed in the experiments. Valve assembly of combustion engines undergo fretting wear due to a complex phenomenon involving structural stiffness and contact tribology. Valve wear has many detrimental effects on the engine performance. It causes valve recession leading to changes in connections of valve drive train in turn disturbing the opening and closing of valves. With stringent emission norms, usage of lubricant to reduce friction at the contact is restricted. If the wear across the circumference is not uniform, there will be leakage of gas and the engine gives lesser power output. There is a need to thoroughly understand the reason for valve wear and develop a numerical model that can predict valve fretting wear for the given number of operating hours. Experiments were performed to understand the wear mechanism and derive wear coefficients that can be used in the numerical model. A numerical wear model is built that captures structural stiffness of the valve assembly and wear mechanism at seat contact.

La durée de vie des pièces mécaniques en contact est fortement affectée par la présence d'hétérogénéités dans le matériau, comme des renforts (fibres, particules), des précipités, des porosités, ou encore des fissures. Des hétérogénéités dures et de formes complexes peuvent créer des surcontraintes locales, initiatrices de fissures par fatigue à proximité de la surface de contact. Une analyse quantitative des surcontraintes créées par les hétérogénéités est nécessaire à la compréhension des mécanismes d'endommagement. Cette étude s'applique à des roulements de ligne d'arbre qui font partie des éléments critiques de moteurs en aéronautique. Elle vise à déterminer précisément la distribution du champ de pression sur l'aire effective de contact et à prédire le profil et l'évolution des champs de contraintes/déformations à chaque passage de la charge sur un volume élémentaire représentatif prenant en compte le gradient de dureté, la présence de carbures et l'existence des contraintes initiales d'origine thermochimique. Une partie de l’étude est consacrée au développement d’un solveur du problème de contact roulant élasto-plastique avec présence d’hétérogénéité par les méthodes semi analytiques assurant un excellent gain en temps et ressources de calculs. Ensuite, un algorithme homogénéisation a été conçu pour analyser le comportement effectif d’un massif élasto-plastique hétérogène sous indentation. Enfin une partie expérimentale est dédiée à la caractérisation microstructurale des aciers étudiés dans le but de déterminer leurs propriétés. Les analyses des résultats de cette étude concourent à soutenir que bien que les inclusions de particules non métalliques soient responsables de la haute résistance de ces matériaux, certaines d’entre elles (celles de longueur dépassant les dizaines de micromètre ou celles qui forment des chaines dans une direction particulière) deviennent, au cours des cycles de fatigue, les principales sources d’endommagement depuis l’échelle locale jusqu’à la rupture globale de la structure. / The lifetime of contacting mechanical parts is strongly affected by the presence of heterogeneities in their materials, such as reinforcements (fibers, particles), precipitates, porosities, or cracks. Hard heterogeneities having complex forms can create local overstress that initiating fatigue cracks near the contact surface. The presence of heterogeneities influences the physical and mechanical properties of the material at microscopic and macroscopic scales. A quantitative analysis of the over-stresses generated by heterogeneities is necessary to the comprehension of the damage mechanisms. The present study is applied to rolling bearings which are the critical elements of the aero-engine's mainshaft. The performance required for these bearings, led SKF Aerospace to introduce a new technology of hybrid bearing with ceramic rolling elements on high-strength steels having experienced a double surface treatment (carburizing followed by nitriding). The study aims to precisely determine the pressure field distribution on the effective contact area and to predict the profile and the evolution of the stress/strain fields at each loading cycle on a representative elementary volume that takes into account the gradient of hardness, the presence of carbides and the existence of an initial compressive stress from thermochemical origin. A major part of this study is devoted to develop a heterogeneous elastic-plastic rolling contact solver, by semi-analytical methods ensuring an excellent saving of calculation time and resources. Thereafter, a homogenization algorithm was built to analyze the effective behavior of a heterogeneous elastic-plastic half-space subjected to an indentation loading. Finally, an experimental part is dedicated to the microstructure characterization of the studied steels with intent to determine their properties. A description of the carbides behavior inside the matrix during micro-tensile tests was carried out under SEM in-situ observation. In the scheme of all analyses conducted in the present work, it can be argued that, although the heterogeneities (such as carbides or nitrides) are responsible for the high resistance of the studied materials, some of them (those whose length exceeds tens of micrometer or those which form stringers in a particular direction) become, over fatigue cycles, the main sources of damage, from their local scale up to the macroscopic failure of the structure.