The increasing use of alpha/beta Ti-Al alloys in critical aircraft gas turbine engine and airframe applications necessitates the further development of physically-based constitutive models that account for their complex microdeformation mechanisms. Alpha/beta Ti-Al alloys are dual-phase in nature consisting of a mixture of hcp (alpha) and bcc (beta) crystal structures, which through variation in alloying elements and/or processing techniques can be produced in a wide range of microstructural compositions and morphologies. A constitutive model for these materials should address the various sources of material anisotropy and heterogeneity at both the micro and macroscales. The main sources of anisotropy in these materials are the low symmetry of the hcp phase, the texture, the relative strengths of different slip systems, non-planar dislocation core structures, phase distributions, and dislocation substructure evolution. The focus of this work is the development of a 3-D crystal plasticity model for duplex Ti-6Al-4V (Ti-64), an (alpha+beta) alloy. The model is used to study the process of attachment fatigue. Attachment fatigue is a boundary layer phenomenon in which most of the plastic deformation and damage accumulation occurs at depths on the order of tens of microns and encompasses regions of only a few grains into the depth of the material. The use of computational micromechanics-based crystal plasticity models to study attachment fatigue is a relatively new approach. This approach has the potential to offer additional insight to classical homogeneous plasticity models, since the length scales over which relative slip and crack initiation occur during this process is on the order of microstructural dimensions. Emphasis is placed on understanding the effects that texture, slip strength anisotropy, and phase distribution have on the surface and subsurface deformation fields during attachment fatigue. The deformation fields are quantified in terms of cumulative effective plastic strain distributions, plastic strain maps, and plastic strain-based critical plane multiaxial fatigue parameters.

No description available.

Pressverbindungen gehören zu den klassischen Maschinenelementen und werden insbesondere in der Antriebstechnik häufig eingesetzt. Zur sicheren und zugleich wirtschaftlichen Auslegung derartiger Verbindungen unter zyklischen Lasten fehlen generell gültige sowie abgesicherte normative Vorgaben bzw. Richtlinien für den Anwender. Insbesondere ist dies dann zutreffend, wenn Geometrien vorkommen, für welche keine Tabellen- bzw. Erfahrungswerte existieren. In dieser Arbeit werden ausführliche experimentelle Untersuchungen zur Ermüdungsfestigkeit von Pressverbindungen einer Standardgeometrie vorgestellt. Im Fokus der Untersuchungen steht die Dauer-, Zeit- und Betriebsfestigkeit der biege- sowie torsionsbelasteten Verbindung. Auf Basis der erzielten Festigkeiten und Lebensdauerwerte erfolgt die Ableitung normspezifischer Kennwerte für die Praxis. Weiterhin steht die Übertragung der erzielten Ergebnisse auf andere Pressverbindungs-Geometrien, wie beispielsweise die Verbindung mit Wellenabsatz, im Vordergrund. Hierbei wird das Verhalten hinsichtlich der Kerbwirkung im Vergleich zu gekerbten Wellen sowie zu anderen reibdauerbeanspruchten Verbindungen untersucht. Zudem erfolgt eine ausführliche Analyse simulationsspezifischer Einflussgrößen auf die Beanspruchungshöhe der Pressverbindung. Auf Grundlage dieser Erkenntnisse wird ein neues Auslegungskonzept erarbeitet und an Ergebnissen aus der Literatur gespiegelt.

Neste trabalho, foram determinadas as propriedades de tração, fadiga convencional e fadiga por fretting, do aço DIN 1.4112 (DIN X 90 Cr Mo V 18) nitretado por plasma, usado na fabricação de anéis de pistão de motores de combustão interna. Os corpos de prova tratados a 500ºC durante 5 horas. O material nitretado não apresentou valores de alongamento e redução de área possíveis de serem medidos e, tanto o limite de escoamento como o limite de resistência à tração, tiveram valores próximos aos do material temperado e revenido. Os ensaios de fadiga convencional e fadiga por fretting foram realizados em temperatura ambiente, sob carregamento cíclico tração-tração com R=0,1 e freqüência de 30 Hz. O fretting foi conseguido pressionando blocos de contato, feitos a partir de um ferro fundido cinzento, contra o corpo de prova de fadiga, com uma força normal de 100 N. Com o levantamento das curvas S-N para os dois ensaios, foi obtido o fator de redução de resistência FRR=1,62, que o fenômeno de fretting causa na fadiga convencional. Nos ensaios de fadiga por fretting, o pico da força de atrito aumentou com a tensão axial cíclica aplicada, atingindo um valor mínimo de 28 N e no máximo de 76 N. A camada nitretada apresentou microdureza máxima 1288 HV100 e espessura da camada de 91 &#956m. A metalografia revelou na camada nitretada, uma camada de compostos, a zona de difusão e uma zona de transição para o subtrato bem definidas. Foram encontrados nitretos dos tipos &#949 (Fe2-3N) e &#947\'(Fe4N) na superfície da camada nitretada. A análise fratográfica, revelou, em tração, o trincamento da superfície devido à baixa tenacidade da camada nitretada, além da programação de trincas por fadiga abaixo da camada nitretada, nos ensaios de fadiga convencional. Os ensaios de fadiga por fretting produziram acumulação de detritos e a formação de trincas secundárias na área ) na área de contato de fretting. / In the present work, the fretting and plain fatigue properties of plasma nitrided martensitic stainless steel, DIN 1.4112 (DIN X 90 Cr Mo V 18), used in piston rings, were investigated. Both fretting and plain fatigue specimens were treated at 500°C for 5 h. The fretting pads were made of gray cast iron. Both fretting and plain fatigue tests were carried out under a load-controlled condition under stress rate, R=0.1 and frequency of 30 Hz. The S-N curves generated with and without fretting showed the strength reduction factor SRF=1.62 when fretting was applied. In the fretting fatigue, frictional force increased with axial cyclic stress and reached a minimum value of 28 N and maximum value of 60 N. Microhardness measurements have shown that the nitrided case presented a maximum hardness of 1288 HV100 and thickness of 91 &#956m. X-ray diffraction techniques indicated that the compound layer consists of &#949 (Fe2-3N) and &#947\' (Fe4N) phases. Fractographic observations showed superficial cracking in tensile specimens due to the low toughness of the nitrided case and fatigue crack growth below this layer in plain fatigue specimens. Fretting fatigue tests produced accumulation of debris and the formation of secondary cracks at the contact area.

Ces travaux sont consacrés à l’étude des mécanismes prépondérants pouvant intervenir dans l’endommagement en fretting-fatigue pour des alliages Al-Cu-Li. Afin d’apporter des réponses, une importante étude expérimentale a été menée en 3 sections distinctes : comportement en fatigue avec concentration de contrainte dans la pièce; résistance à l’endommagement en fretting; essais de fretting-fatigue. Un effort particulier est réalisé pour déterminer l’influence de la microstructure sur ces différents mécanismes. Dans les conditions testées en fatigue, les matériaux étudiés présentent des durées de vies similaires alors que les chemins de fissuration diffèrent aussi bien au niveau macroscopique que microscopique. L’analyse EBSD de zones fissurées met en lumière l’importance de la texture pour les alliages à l’état UA à la différence de ceux à l’état T8. L’état de précipitation est cependant le facteur le plus important contrôlant la morphologie de la fissure. Contrairement à la littérature, cette étude montre que les mécanismes de fretting ne sont pas indépendants de la microstructure. En effet, pour des conditions testées identiques, les alliages à l’état UA présentent un meilleur comportement à la fissuration que ceux à l’état T8. Deux techniques d’analyses 3D ont été utilisées afin de mettre en évidence l’effet de la microstructure. L’analyse des faciès de rupture des éprouvettes de fretting-fatigue a permis de décomposer le mécanisme d’endommagement en trois étapes: amorçage en fretting, propagation sous dominance mixte de la sollicitation de fretting et de fatigue, puis propagation uniquement contrôlée par la fatigue jusqu’à rupture brutale de l’échantillon. / The influence of microstructure on the crack nucleation and growth under fretting-fatigue loading was investigated on different Al-Cu-Li alloys used for aerospace applications. The experimental study was divided into 3 distinct parts: - behaviour in fatigue with stress concentration, - crack resistance in fretting, - fretting-fatigue tests. Although all the investigated alloys exhibit a similar life time under the fatigue conditions tested, they present different (macroscopic and microscopic) crack path morphologies. ESBD analyses show that only UA-alloys were sensitive to grain orientation. The main factor influencing the crack path remains the precipitation state, because of the direct interaction with dislocation motion. Concerning the fretting tests, this study shows that cracking is not only controlled by contact conditions as assumed in the literature. For identical testing condition, UA alloys present a better behaviour in crack resistance than T8 alloys. This tendency is also true under fretting-fatigue condition. The fracture surfaces were analysed and allow to decompose fretting-fatigue mechanism in 3 steps: crack initiation induced by fretting, crack propagation under the influence of both fretting and fatigue loadings, then propagation only controlled by fatigue until final breaking.

Axisymmetric analysis of cylindrical contacts is considered in the context of axisymmetric assemblies such as shrink-fits. Fretting fatigue induces sub-critical cracks along the contact interface of press fits especially when they are subjected to vibration. The surface and near surface stresses play a major role in the fretting fatigue crack initiation process. Assuming near surface contact stresses to be largely independent of the actual geometry of components in contact, half-plane analyses and experimental results obtained from a strip configuration are often cited in the literature to predict and understand crack initiation in the actual components (ASTM STP 1425). This thesis starts with half plane and strip models for cylindrical contact such as in a shrink fitted shaft. Different traction profiles underpinning a typical fretting contact constitute a study of different geometrical parameters and friction coefficients. The cylindrical shrink fitted contact is considered using mixed boundary formulation. The different cases of contact such as full slip, partial stick-slip and full stick are considered. A formulation for cyclically varying tractions is attempted using dynamic elasticity. Finally, the problem of cylindrical cracks is highlighted to understand interface delamination in a fiber reinforced composite. Stress functions in conjunction with Fourier transforms are used for analysis. Dynamic potentials based on Helmholtz decomposition are used for dynamic loading.For static loading Love’s stress function is used for axisymmetric problems while Airy’s stress function is used for 2D problems. Solution procedures for solving traction boundary and mixed boundary conditions are described. Preliminary experiments are described to appreciate the contact stresses and crack initiation in cylindrical contact. Photoelastic fringes in a cylinder under a band of pressure illustrate fretting contact stresses concentrated close to the surface with the core of the cylinder relatively unstressed. Further, some material testing experiments using a specially designed cylindrical fretting rig demonstrated typical features of fretting fatigue crack initiation for providing the theoretical motivation. Fretting fatigue induces the initiation of a number of sub critical cracks along the contact interface of components in mechanical assemblies especially under vibration. The dominant crack among the initiated cracks may grow in size to the critical length in the presence of bulk cyclic loading finally resulting in fracture of the entire component. Fretting fatigue leads to unexpected failure of the component well below the expected life. It is therefore, critical to analyse, detect and control fretting. The blade root-disk joint in gas turbines as a critical example of fretting fatigue has spurred extensive research effort. There is relatively little literature available on cylindrical fretting in shrink fitted joint focused in this thesis. Analytical solutions for static fretting tractions are presented using both axisymmetric and plane elastic stress functions for later comparison. While Fourier transforms in conjunction with Airys stress functions are exploited for attacking plane problems, Loves axisymmetric stress functions are explored for cylindrical fretting. Near surface stresses are of great interest in fretting fatigue research. Although two dimensional models provide general understanding of stresses caused during fretting, these models become inadequate to explain the interaction of local stresses with the bulk stresses inevitably present in cylindrical components. Global stress analysis tools are desirable for estimating the fatigue life of components experiencing fretting. While numerical techniques immensely aid fatigue life estimation they have their limitation when it comes to coated components. Stress analysis of coated cylinders unveils the intricate influence of the elastic mismatch as well as the width of the loading for varying friction coefficients. Comparison of results obtained from axisymmetric elasticity with plane elasticity is discussed in detail. The validity and scope of relying on plane fretting results to cylindrical fretting contacts is examined by comparing the results obtained for three different traction profiles. Fretting is generally modeled as a stress boundary value problem wherein the normal and frictional shear stresses are prescribed on the cylindrical surface. In reality fretting generally turns out to be a mixed boundary value problem with unknown regions of stick and slip requiring prescribing traction and displacement simultaneously. This belongs to a formidable class of unsolved contact mechanics problems in cylindrical axisymmetric elasticity. The famous spherical axisymmetric Hertz problem has no cylindrical counterpart except in the limiting case of a cylinder of large radius. These aspects are investigated for studying the hub-shaft interfacial geometry. A conformal contact profile is considered to model a shrink fit; the contact pressure is zero at the ends of contact. The case of full slip condition is analysed assuming a frictionless contact. With friction, partial stick-slip condition is analysed. The unknown contact traction is resolved in terms of Chebyshev expansions whose unknown coefficients are solved using Schmidt method. The unknown contact length and stick zone length are determined through an iterative procedure. A rigid uneven undulating axisymmetric hub in total contact over an elastic shaft under full stick condition is analysed for obtaining the near surface stresses for a given value of hub penetration. Even though the stresses oscillate in fretting, almost all the analyses reported in the literature use static formulation. Understanding this need, a dynamic analysis for modeling fretting of a cylinder subjected to harmonic pressure and shear is attempted. The Pochhammer dispersion relation becomes a prerequisite for a dynamic analysis. The results show that the stresses do not decay away from the contact, in contrast to the static results. This shows the propagation of stresses along the axial direction. Further extension of the dynamic analysis to a layered cylinder is also described. The results obtained on contact stresses and contact tractions under the cylindrical contact represent a significant advance to the literature for modeling fretting fatigue crack initiation and propagation. Formulating cylindrical crack problems is somewhat similar to cylindrical contacts. Such cylindrical cracks arise from the debonding along the fiber-matrix interface of a composite. A unified formulation for the problem of a pressurised cylindrical crack as also a pair of 2D parallel cracks in infinite media is attempted using Love’s stress function in conjunction with Fourier transforms. The results obtained for stress intensity factors, strain energy release rate, mode mixity, crack opening and sliding displacements are compared with that of a 2D pair of parallel cracks obtained using the unified formulation. The asymptotic situation of a large crack length to spacing ratio is examined in detail. In the case of a pair of parallel cracks, this implies a single crack in mode-I as far as the total energy release rate is concerned while at the same time retaining an asymptotic value for the mode mixity. This unique feature of near field mixed mode blending smoothly to mode-I in the far field is also seen for the stress field around a symmetrically branched crack. Thus, this thesis presents a collection of cylindrical elastostatic and elastodynamic axisymmetric solutions to provide better understanding of fretting and delamination problems encountered in press fit assemblies.

Fretting, which can occur when two bodies in contact undergo a low amplitude relative slip, can drastically reduce the fatigue performance of a material. The extent of fretting damage is dependent on the material combination and is affected by many parameters, making it difficult to design against fretting. Some of these parameters include contact force, displacement amplitude, and contacting materials. This work develops a method for quantifying the extent of damage from fretting as a function of these parameters for a thin sheet of AISI 301 stainless steel in the full hard condition in contact with both ANSI A356 aluminum and AISI 52100 steel contacting bodies. Fretting experiments were conducted on a Phoenix Tribology DN55 Fretting Machine using a fixture which was developed for holding thin specimens. The displacement amplitude and normal force were systematically varied in order to cover a range that could typically be experienced during service. The tribological behavior was studied by analyzing friction force during cycling and inspecting the resulting surface characteristics. Fretting damaged specimens were cycled in tension in a servohydraulic test system to failure. The decrease in fatigue life caused by fretting damage was determined by comparing the stress-life (S-N) response of the fretted specimens to the S-N response of the virgin material, thus characterizing the severity of the fretting damage. The conditions that lead to the greatest reduction in life were identified in this way. Using the fracture mechanics based NASGRO model, an Equivalent Initial Flaw Size (EIFS) was used to quantify the level of fretting damage, thus separating the life of the component into crack nucleation and subsequent propagation. This method and data will allow engineers to design more robust components that resist fretting damage, thus increasing the safety and reliability of the system.

Neste trabalho, foram determinadas as propriedades de tração, fadiga convencional e fadiga por fretting, do aço DIN 1.4112 (DIN X 90 Cr Mo V 18) nitretado por plasma, usado na fabricação de anéis de pistão de motores de combustão interna. Os corpos de prova tratados a 500ºC durante 5 horas. O material nitretado não apresentou valores de alongamento e redução de área possíveis de serem medidos e, tanto o limite de escoamento como o limite de resistência à tração, tiveram valores próximos aos do material temperado e revenido. Os ensaios de fadiga convencional e fadiga por fretting foram realizados em temperatura ambiente, sob carregamento cíclico tração-tração com R=0,1 e freqüência de 30 Hz. O fretting foi conseguido pressionando blocos de contato, feitos a partir de um ferro fundido cinzento, contra o corpo de prova de fadiga, com uma força normal de 100 N. Com o levantamento das curvas S-N para os dois ensaios, foi obtido o fator de redução de resistência FRR=1,62, que o fenômeno de fretting causa na fadiga convencional. Nos ensaios de fadiga por fretting, o pico da força de atrito aumentou com a tensão axial cíclica aplicada, atingindo um valor mínimo de 28 N e no máximo de 76 N. A camada nitretada apresentou microdureza máxima 1288 HV100 e espessura da camada de 91 &#956m. A metalografia revelou na camada nitretada, uma camada de compostos, a zona de difusão e uma zona de transição para o subtrato bem definidas. Foram encontrados nitretos dos tipos &#949 (Fe2-3N) e &#947\'(Fe4N) na superfície da camada nitretada. A análise fratográfica, revelou, em tração, o trincamento da superfície devido à baixa tenacidade da camada nitretada, além da programação de trincas por fadiga abaixo da camada nitretada, nos ensaios de fadiga convencional. Os ensaios de fadiga por fretting produziram acumulação de detritos e a formação de trincas secundárias na área ) na área de contato de fretting. / In the present work, the fretting and plain fatigue properties of plasma nitrided martensitic stainless steel, DIN 1.4112 (DIN X 90 Cr Mo V 18), used in piston rings, were investigated. Both fretting and plain fatigue specimens were treated at 500°C for 5 h. The fretting pads were made of gray cast iron. Both fretting and plain fatigue tests were carried out under a load-controlled condition under stress rate, R=0.1 and frequency of 30 Hz. The S-N curves generated with and without fretting showed the strength reduction factor SRF=1.62 when fretting was applied. In the fretting fatigue, frictional force increased with axial cyclic stress and reached a minimum value of 28 N and maximum value of 60 N. Microhardness measurements have shown that the nitrided case presented a maximum hardness of 1288 HV100 and thickness of 91 &#956m. X-ray diffraction techniques indicated that the compound layer consists of &#949 (Fe2-3N) and &#947\' (Fe4N) phases. Fractographic observations showed superficial cracking in tensile specimens due to the low toughness of the nitrided case and fatigue crack growth below this layer in plain fatigue specimens. Fretting fatigue tests produced accumulation of debris and the formation of secondary cracks at the contact area.

L'optimisation du dimensionnement des structures passe par une meilleure connaissance de leur mode d'endommagement. Cette étude se focalise donc sur la caractérisation de l'endommagement du contact aube/disque des moteurs aéronautique. Cet assemblage mécanique est soumis a une combinaison d'un effort normal (force centrifuge) et tangentiel (dynamique de l'aube). La portée du disque en Ti-6Al-4V subi donc un chargement complexe de type fretting fatigue. Ce type de sollicitation entraine, entre autre dégradation, de la fissuration dont la modélisation expérimentale et numérique est rendue difficile par les limitations des moyens et des connaissances actuelles. Le premier objectif de ce travail de thèse est de développer un moyen d'essai et une instrumentation associée afin d'étudier de façon qualitative et quantitative la fissuration d'un contact Ti-6Al-4V/Ti-6Al-4V. Le second but est d'utiliser les données issues de ce moyen expérimental afin de proposer un modèle de prédiction des durées de vie de cet assemblage. Un montage inédit de fretting fatigue double vérin mono-contact a été mis en place avec une instrumentation nouvelle pour ce type d'essai : suivi de fissuration par suivi de potentiel et par émission acoustique. Une attention particulière a été apportée aux calibrations et aux méthodologies expérimentales. Ce banc d'essai permet notamment de simuler des efforts de fretting applique en phase ou alors de telle manière a simuler un vrai cycle de vol. Cet outil a permis de décrire quantitativement les premières courbes de Wohler en fretting à amorçage (Effort de fretting vs Nombre de cycles à amorçage) pour deux configurations de contact (cylindre/plan et plan/plan). Les impacts des différents paramètres de fretting sur l'amorcage ont pu être quantifies. Les paramètres influant sont : la configuration du contact, les niveaux des efforts appliques et leur mode de combinaison (cycles en phase ou cycles de type vol). De plus des courbes de cinétique de propagation des fissures ont pu être extraites des différents essais, montrant un fort impact du fretting sur les vitesses de propagation des fissures. Une analyse qualitative via l'émission acoustique a montré un mécanisme d'amorçage et de propagation en 3 étapes suivant la perte d'influence du contact. Un modèle de prédiction de l'amorçage et de simulation de la propagation des fissures a été mis en place. Bien que limite dans la prise en compte des effets gradients (approches non locales), ce modèle se montre très performant surtout dans sa capacité à utiliser les données expérimentales dans l'identification des lois d'amorçage ou de propagation. Ce travail a donc permis d'importantes avancées dans la compréhension des mécanismes de fissuration et dans leur modélisation ouvrant ainsi la porte vers une prédiction fiable de l'endommagement des contacts aube/disque.

Le vieillissement des lignes de transport d’énergie électrique est une problématique majeure des réseaux. D’ailleurs, des problèmes se posent au plan de l’évaluation de l’état des conducteurs qui, soumis aux vibrations éoliennes, sont vulnérables à l’endommagement en fatigue. Surtout présent aux pinces de suspension, ce phénomène est encore difficile à quantifier, notamment quant à la prédiction de la durée de vie résiduelle des conducteurs. D’autre part, avec le besoin croissant d’optimiser l’exploitation du réseau tout en maintenant sa fiabilité, une estimation précise de l’état d’endommagement des conducteurs est primordiale. Pour cela, une caractérisation des sollicitations à l’échelle des brins est d’abord requise. L’objectif principal de cette thèse vise donc le développement d’une stratégie de modélisation et d’analyse des conducteurs sollicités en vibrations éoliennes permettant une évaluation précise des conditions de chargement locales à l’échelle des brins, tout en tenant compte de l’effet de la géométrie des pinces de suspension. Une stratégie de modélisation 3D des solides toronnés est d’abord développée avec la méthode des éléments finis selon une discrétisation individuelle des brins par éléments poutres, capable de traiter toutes les interactions inter-filaires en frottement. Cette modélisation traduit efficacement la cinématique des torons tout en donnant accès aux charges locales. Son caractère général lui permet aussi d’être appliquée à tout problème impliquant des torons. Appliquée à l’étude des conducteurs sous l’effet des vibrations éoliennes, la stratégie conduit à une description précise de leur comportement tant au plan global en flexion que de la description des contraintes aux brins. Des estimations réalistes de durées de vie en fatigue des conducteurs sont même possibles par l’application de critères d’endommagement aux contraintes. Ensuite, les pinces de suspension sont intégrées à la stratégie de modélisation selon une représentation surfacique traitant le contact pince/conducteur. Une comparaison à des mesures expérimentales met en relief la précision de l’approche. L’analyse de la solution numérique permet l’identification des zones critiques d’endommagement en contact à chacune des couches du conducteur et révèle des informations nouvelles quant à la nature de la sollicitation des brins à la pince de suspension. Finalement, des travaux exploratoires proposent un nouveau concept d’analyse multi-échelles en combinant la modélisation numérique d’un système pince/conducteur à des essais de fatigue sur brins individuels. Une mise en œuvre préliminaire de l’approche permet de valider le concept et en jette les bases en vue de son application future. En somme, la stratégie de modélisation développée dans cette thèse constitue un puissant outil d’analyse qui ouvre maintenant la voie à une caractérisation appropriée de la fatigue des conducteurs en vue ultimement de prédire leur durée et vie résiduelle. / Abstract : The aging of overhead transmission lines is a major concern for utilities. In particular, problems arise in assessing the integrity of conductors whose exposure to Aeolian vibrations renders them vulnerable to fatigue damage. Occurring mainly at the suspension clamps, conductor fatigue is still difficult to quantify, especially regarding the prediction of their residual life. With the increasing need to optimize the power grid while maintaining its reliability, accurate evaluations of the conductor damage state become crucial. To this matter, a characterization of the stress levels at the wire scale is first required. The main objective of this thesis is therefore to develop a strategy for the modeling and analysis of conductors subjected to wind induced vibrations, allowing an accurate description of the local load conditions, while accounting for the effects of the suspension clamps. A finite element wire strand modeling strategy is first developed based on a 3D beam element discretization, considering all frictional wire interactions. The modeling approach efficiently reproduces the wire strand kinematics while giving access to the local loads. Its general formulation also allows it to be applied to any problem involving strands. Applied to the study of conductors subjected to Aeolian vibrations, the strategy leads to an accurate description of their behavior at both the global strand deformations and the wire stress description. Realistic conductor residual life estimates are even possible with the use of common damage criteria. The suspension clamps are then incorporated into the modeling strategy using a surface representation of the conductor/clamp contact. Comparisons with experimental measurements highlight the precision of the approach. The model response analysis allows now the identification of the critical damage zones within each conductor layers and reveals new information about the nature of the wire stresses at the suspension clamp. Finally, exploratory works propose a new concept of multi-scale analysis combining the numerical conductor/clamp modeling strategy to experimental fatigue tests on individual wires. A preliminary implementation of the approach validates the concept and lays the foundations for its future application. In summary, the modeling strategy developed in this thesis constitutes a powerful analytical tool which now opens the way to an appropriate characterization of conductor fatigue with the ultimate objective to eventually predict their residual life.