La conception de moteurs aéronautiques plus performants soumet les alliages de titane constitutifs des mâts-réacteurs à des contraintes thermiques et mécaniques plus sévères. Ces matériaux doivent d’une part être qualifiés en termes de tolérance aux dommages. D’autre part, l’exposition prolongée de ces alliages de titane à des températures élevées en service pose la question de leur vieillissement métallurgique. Le dimensionnement et la maintenance de telles aérostructures doit ainsi prendre en compte l’ensemble de ces deux problématiques cruciales.Dans ces travaux, le comportement cyclique ainsi que la résistance à la fissuration par fatigue d’alliages de titane de différentes nuances (TA6V, Ti 6242 et Ti 17) et de différentes microstructures, ont été étudiés en fonction du degré de vieillissement. L’effet du vieillissement se traduit essentiellement par une augmentation des vitesses de propagation à forte valeur du facteur d’intensité de contrainte, à température ambiante. Dans un second temps, une démarche de caractérisation poussée de ce phénomène mettant en œuvre des sollicitations variées, à différentes échelles et associées à des analyses fractographiques a été appliquée. Ceci a permis de proposer un scénario d’endommagement avant et après vieillissement pour l’alliage le plus affecté par l’exposition en température, le Ti 17. Ce scénario montre après vieillissement l’apparition d’un mode d’endommagement « statique » en lien avec un processus de rupture puis décohésion intralamellaire, sans modification notable du comportement cyclique. Enfin, une approche d’équivalence temps-température est proposée pour décrire la cinétique de dégradation des propriétés mécaniques consécutive au vieillissement. / The conception of more efficient aircraft engines induces increased stress and temperature levels on the titanium alloys constitutive of the engine pylon. On the one hand, these materials have to be qualified in terms of damage tolerance. On the other hand, the long term high temperature exposure of these titanium alloys gives also rise to the question of thermal aging and metallurgical stability. Hence, the dimensioning as well as the maintenance of such aerostructures need to be considered in the light of both these critical issues.In the present work, the cyclic behavior as well as the fatigue crack resistance of different titanium alloys (TA6V, Ti 6242 et Ti 17), with various microstructures were studied after different aging conditions. Aging induces mainly an increase in crack growth rates at high values of the stress intensity factor, at room temperature. Subsequently, a thorough characterization procedure of this phenomenon was undertaken,including various types of loadings, at different scales and associated with fractographic analyses. The results allowed to suggest a damage scenario before and after aging, in the case of the alloy most affected by aging: theTi 17 alloy. This scenario shows the occurrence of a « static » mode of failure, which is linked to a damage process associated with intralamellar fracture and decohesion, without noticeable changes in the cyclic behavior. Finally, a time-temperature equivalency approach was developed to describe the kinetics of degradation of the mechanical properties induced by aging.

Orientador: Lídia Almeida Barros / Banca: Maurizio Babini / Banca: Nelson Luis Ramos / Banca: Ricardo Baptista Madeira / Resumo: A presente dissertação resulta do desenvolvimento de um projeto sobre o léxico, mais especificamente sobre a terminologia especializada predominante em atas de assembléias de associados submetidas à tradução juramentada. A língua de partida é a espanhola, nas variantes nacionais da Venezuela e do Uruguai, e a de chegada é a portuguesa do Brasil. Procedemos a investigações científicas no campo da Terminologia, utilizando também o arcabouço teórico e metodológico da Lingüística de Corpus e dos Estudos da Tradução Baseada em Corpus. Os termos foram identificados e contrastados aos corpora comparáveis em busca das aproximações e distanciamentos existentes entre os termos utilizados pelos tradutores juramentados e os termos encontrados em documentos de mesma natureza originalmente escritos em português. Buscamos ainda equivalentes em espanhol dos termos em português levantados em nossa pesquisa. Diante dos resultados, observamos questões de equivalência terminológica bilíngüe (total, parcial e ausência de equivalência). As análises foram feitas visando observar o quanto as diferentes realidades dos sistemas organizacionais do país de origem dos textos traduzidos e do país a que tais termos se destinam são relevantes para a compreensão do texto e de sua tradução. As diferenças encontradas não se situam apenas entre as duas línguas em questão (o português e o espanhol), mas também entre as variantes nacionais venezuelana, uruguaia e espanhola. / Abstract: The present work results from the development of a project about the lexicon, more specifically about the terminology that can be found in minutes of member's meetings submitted to sworn translation. The source language is Spanish, from Venezuela and Uruguay and the target language is Brazilian Portuguese. Our study was performed based on Terminology; we also drawn on some theoretical and methodological principles of Corpus Linguistics and of Corpus-Based Translation Studies. The terms were identified and contrasted with two comparable corpora to find approximations and distances from the terminologies that were used by the sworn translators and the terms found dealing with the same subject. We also searched for the equivalents in Spanish to the terms in Portuguese that were found in our corpus of study. We observed bilingual terminological equivalencies related to total, partial or even absence of equivalence. The analysis was carried out in order to show how different realities of the organizational systems of the countries in which the texts are produced, and the country to which the texts are destined, are relevant for the understanding and the translation, mainly the sworn translation. The differences found were not only between Spanish and Portuguese, but also between the language spoken in Venezuela, Uruguay and Spain. / Mestre

Made available in DSpace on 2014-06-11T19:22:19Z (GMT). No. of bitstreams: 0 Previous issue date: 2009-06-01Bitstream added on 2014-06-13T20:28:35Z : No. of bitstreams: 1 costa_lr_me_sjrp.pdf: 516889 bytes, checksum: 36d1aac51c9fc1b9b626da124ab023e7 (MD5) / A presente dissertação resulta do desenvolvimento de um projeto sobre o léxico, mais especificamente sobre a terminologia especializada predominante em atas de assembléias de associados submetidas à tradução juramentada. A língua de partida é a espanhola, nas variantes nacionais da Venezuela e do Uruguai, e a de chegada é a portuguesa do Brasil. Procedemos a investigações científicas no campo da Terminologia, utilizando também o arcabouço teórico e metodológico da Lingüística de Corpus e dos Estudos da Tradução Baseada em Corpus. Os termos foram identificados e contrastados aos corpora comparáveis em busca das aproximações e distanciamentos existentes entre os termos utilizados pelos tradutores juramentados e os termos encontrados em documentos de mesma natureza originalmente escritos em português. Buscamos ainda equivalentes em espanhol dos termos em português levantados em nossa pesquisa. Diante dos resultados, observamos questões de equivalência terminológica bilíngüe (total, parcial e ausência de equivalência). As análises foram feitas visando observar o quanto as diferentes realidades dos sistemas organizacionais do país de origem dos textos traduzidos e do país a que tais termos se destinam são relevantes para a compreensão do texto e de sua tradução. As diferenças encontradas não se situam apenas entre as duas línguas em questão (o português e o espanhol), mas também entre as variantes nacionais venezuelana, uruguaia e espanhola. / The present work results from the development of a project about the lexicon, more specifically about the terminology that can be found in minutes of member’s meetings submitted to sworn translation. The source language is Spanish, from Venezuela and Uruguay and the target language is Brazilian Portuguese. Our study was performed based on Terminology; we also drawn on some theoretical and methodological principles of Corpus Linguistics and of Corpus-Based Translation Studies. The terms were identified and contrasted with two comparable corpora to find approximations and distances from the terminologies that were used by the sworn translators and the terms found dealing with the same subject. We also searched for the equivalents in Spanish to the terms in Portuguese that were found in our corpus of study. We observed bilingual terminological equivalencies related to total, partial or even absence of equivalence. The analysis was carried out in order to show how different realities of the organizational systems of the countries in which the texts are produced, and the country to which the texts are destined, are relevant for the understanding and the translation, mainly the sworn translation. The differences found were not only between Spanish and Portuguese, but also between the language spoken in Venezuela, Uruguay and Spain.