Le titane et ses alliages sont très largement étudiés en raison de leur grande utilisation dans l'industrie chimique, les implants médicaux et les industries aérospatiales. Vu le rôle important dans la déformation plastique, le maclage a été largement étudié dans les métaux hexagonaux L'état de contrainte locale peut être modifié par maclage, ce qui influence les modes séquentiels de déformation tels que le glissement, le maclage et le maclage secondaire Ainsi, il existe une demande urgente pour comprendre le mécanisme associé à la déformation induite par maclage, utile pour le développement de modèles prédictifs qui peuvent décrire les événements ultérieurs induits par maclage, ainsi que leurs corrélations avec les microstructures. Dans ce travail, l'analyse cristallographique de la sélection de variantes de macles et des jonctions macle-macle (TTJ= twin-twin junction) est appliquée sur du titane commercialement pur. Un nouveau mécanisme de maclage séquentiel, où les macles {101̅2} sont stimulées par des jonctions macle {112̅1}-macle, est observée par EBSD quasi in situ. Un autre mécanisme de maclage séquentiel a été trouvé lorsque le maclage de compression {112̅2} contient une macle d'extension {101̅2} près des joints de grain à forte désorientation. L'accommodation est utilisée pour déterminer le variant de macle séquentiel lorsque le facteur de Schmid classique (SF) n'est pas suffisant. En outre, une analyse détaillée des 425 macles secondaires {101̅2} détectées dans les macles {11 2̅ 2} primaires révèle que les deux variants de macles qui présentent une désorientation spécifique par rapport aux grains parents sont les plus fréquentes. Il est possible de justifier la prévalence des macles secondaires avec un mécanisme de nucléation aidée par les dislocations prismatiques. Lorsqu'il est complété par une analyse SF généralisée, le critère peut prédire avec précision la sélection entre deux variants dans le groupe des macles secondaires les plus fréquentes. Lorsque plusieurs variants de macles sont actifs dans le même grain, des interactions macle-macle peuvent se produire. Les jonctions macle {112̅2}-macle peuvent être divisés en trois types selon la cristallographie des macles {112̅2}. Une analyse statistique de ces interfaces révèle qu'un seul type est le plus fréquent tandis que les autres types sont rarement activés. La fréquence des TTJ peut être évaluée en utilisant une analyse SF généralisée. Il en ressort que les interfaces macle-macle (TTB= twin-twin boundary) ne se forment que d’un côté de la macle. Concernant la formation de TTBs basée sur les interactions des dislocations de macle, les dislocations d'interface dans les TTBs observées ont une énergie de ligne inférieure à celles des TTB non observées. Une opération similaire est appliquée à l'analyse de {112̅1} TTJs / Titanium and its alloys have been extensively investigated due to their wide application in chemical industry, medical implants and aerospace industries. As a significant role in plastic deformation, twinning has been widely studied in hexagonal metals. The local stress state may be modified by twinning, which influences sequential plastic deformation modes such as slips, twinning and secondary twinning. Thus, there is also an urgent demand for understanding the mechanism associated with the twinning-induced deformation, which is useful for the development of predictive capabilities that can describe twinning and twinning-induced sequential events, and their correlations with microstructures. In this work, crystallographic analysis of twin variant selection and twin-twin junctions is applied in commercially pure titanium. A new sequential twinning mechanism that {101̅2} twins are stimulated by the {112̅1} twin-twin junctions (TTJs) is observed by quasi in-situ EBSD. Another sequential twinning mechanism that a {112̅2} compression twin adjoins a {10 1̅ 2} extension twin is found at high angle grain boundaries. Displacement gradient accommodation is used to determine the sequential twin variant while the classical Schmid factor (SF) is not sufficient. Besides, a detailed analysis of the detected 425 {101̅2} double twins inside primary {112̅2} twins reveals that the double twin variants that exhibit specific misorientation with respect to the parent grains are the most frequent. The prevalence of double twins is possible to justify with the prismatic-dislocation mediated nucleation mechanism. When complemented with an apparent SF analysis, the criterion can accurately predict the selection between two variants within the group of the popular double twins. When multiple twin variants are active in the same grain, twin-twin interactions may happen. {112̅2} TTJs can be divided into three types according to the crystallography of {112̅2} twins. A statistical analysis of {112̅2} TTJs reveals that one type is the most popular while other types are rarely activated. The frequency of TTJs can be evaluated by using an apparent SF analysis. The interesting finding is that twin-twin boundaries (TTBs) form in one side of the incoming twin as a TTJ forms. Corresponding to the formation of TTBs based on the interactions of twinning dislocations, interface dislocations in the observed TTBs have lower line energy than those in the un-observed TTBs. Similar operation is applied to the analysis of {112̅1} TTJs

abstract: Proteins are essential for most biological processes that constitute life. The function of a protein is encoded within its 3D folded structure, which is determined by its sequence of amino acids. A variation of a single nucleotide in the DNA during transcription (nSNV) can alter the amino acid sequence (i.e., a mutation in the protein sequence), which can adversely impact protein function and sometimes cause disease. These mutations are the most prevalent form of variations in humans, and each individual genome harbors tens of thousands of nSNVs that can be benign (neutral) or lead to disease. The primary way to assess the impact of nSNVs on function is through evolutionary approaches based on positional amino acid conservation. These approaches are largely inadequate in the regime where positions evolve at a fast rate. We developed a method called dynamic flexibility index (DFI) that measures site-specific conformational dynamics of a protein, which is paramount in exploring mechanisms of the impact of nSNVs on function. In this thesis, we demonstrate that DFI can distinguish the disease-associated and neutral nSNVs, particularly for fast evolving positions where evolutionary approaches lack predictive power. We also describe an additional dynamics-based metric, dynamic coupling index (DCI), which measures the dynamic allosteric residue coupling of distal sites on the protein with the functionally critical (i.e., active) sites. Through DCI, we analyzed 200 disease mutations of a specific enzyme called GCase, and a proteome-wide analysis of 75 human enzymes containing 323 neutral and 362 disease mutations. In both cases we observed that sites with high dynamic allosteric residue coupling with the functional sites (i.e., DARC spots) have an increased susceptibility to harboring disease nSNVs. Overall, our comprehensive proteome-wide analysis suggests that incorporating these novel position-specific conformational dynamics based metrics into genomics can complement current approaches to increase the accuracy of diagnosing disease nSNVs. Furthermore, they provide mechanistic insights about disease development. Lastly, we introduce a new, purely sequence-based model that can estimate the dynamics profile of a protein by only utilizing coevolution information, eliminating the requirement of the 3D structure for determining dynamics. / Dissertation/Thesis / Doctoral Dissertation Physics 2016

The general objective of our study is to investigate the attitudes expressed by young people from Bogotá towards the coexisting Spanish varieties. Specifically, it seeks to investigate the differences of linguistic attitudes from the categories of status and solidarity. The particular speech of young people in Ciudad Bolivar is studied as a factor of sociocultural identity. This study was conducted among a small sample of young people in Ciudad Bolívar, a popular suburb in Bogotá, Colombia. The sample consists of 38 informants between the ages of 11 to 24. A sociolinguistic survey consisting of five parts was used. In the first part, the sociodemographic data was collected, in the second part, a matched guise test was applied to evaluate the acctitudinal differences towards the varieties of Spanish, in the third part the informants answered in writing open questions. In the fourth part, a Likert scale of acceptability was applied to measure the degree of acceptability towards sociolinguistic items. The last part the informants express their acceptance of words and expressions in everyday speech contexts. The informants were divided into three groups: two groups of young students from public schools and a group of young people from a public park. The results of the analysis indicate that attitudes towards the standard variety are positive in formal and educational contexts. In informal contexts and comradeship contexts young people express very positive attitudes towards a non-standard youth variant. The results allow to recognize that this alternative variant of Spanish is characterized by the use of very particular words and expressions invented by the young people. The alternative variant is used as an element of identity and difference. Our research is an invitation to undertake more ambitious studies by expanding the population sample.

Le cancer colorectal est la deuxième cause de décès par le cancer en Amérique du Nord. Il a été démontré que l’intégrine α6β4 est surexprimée dans les tumeurs primaires colorectales et qu’elle a un rôle protumoral. Toutefois, deux variants d’épissage alternatif existe pour la sous-unité intégrine α6 soit, α6A et α6B. Ils possèdent des domaines cytoplasmiques différents laissant croire qu’ils ont également des fonctions différentes. De plus, dans le cancer colorectal humain, une augmentation du ratio des variants α6A/α6B est observée, suggérant ainsi que le variant α6A participerait à la fonction protumorale de l’intégrine α6β4. Toutefois, le rôle précis du variant α6A et sa régulation dans le cancer colorectal humain demeurent inconnus. Les travaux de recherche de cette thèse visent à identifier le rôle du variant α6A dans la carcinogenèse colorectale humaine, en plus de comprendre la régulation de son expression. Dans un premier temps, mes expériences ont confirmé qu’une augmentation du variant α6A est responsable de la surexpression de la sous-unité α6 observée dans le cancer colorectal humain. L’abolition spécifique de ce variant par shARN dans les cellules cancéreuses colorectales humaines a entrainée un ralentissement de la prolifération cellulaire, démontré par les expériences de croissance cellulaire et d’incorporation de BrdU. De plus, cette réduction de la prolifération cellulaire est accompagnée d’une répression importante de la voie Wnt/β-caténine, visualisée par la baisse de la β-caténine active, de sa localisation nucléaire et de son activité transcriptionnelle. La suppression du variant α6A dans les cellules cancéreuses colorectales humaines diminue leur capacité à développer des tumeurs en xénogreffe. Les analyses supplémentaires du mécanisme ont permis de constater que le variant α6A régule la voie Wnt/β-caténine par la dégradation autophagique de la protéine DVL2. De plus, la protéine PRICKLE1, un important médiateur de l’ubiquitination et la dégradation de DVL2, est augmentée par la suppression du variant α6A. Par ailleurs, une forte corrélation positive entre l’expression du variant α6A et MYC a été observée in vitro et in vivo. Mes travaux ont révélé que MYC contrôle l’expression du promoteur de la sous-unité α6 et qu’il favorise l’épissage de l’exon 25. Conséquemment, MYC régulerait l’expression du variant α6A par les facteurs d’épissage ESRP2 et HNRNPA2B1. Ces découvertes démontrent le potentiel de l’utilisation du variant α6A et de son mécanisme comme cible thérapeutique et outil diagnostique.

Monte Carlo simulation techniques have emerged as widely accepted computing tools in tackling many problems in modern structural mechanics. Apart from developments in computational hardware, which have undoubtedly made simulation strategies practically feasible, the success of Monte Carlo simulations has also resulted equally significantly from the methodological developments aimed at controlling sampling variance of the Monte Carlo estimates. The study reported in the present thesis is aimed at developing and validating Monte Carlo simulation based approaches with inbuilt variance reduction capabilities to deal with problems of time variant reliability modeling, random vibration testing, and updating reliability models for statically/dynamically loaded instrumented structures. The relevant literature has been reviewed in Chapter 1. Time variant reliability analysis of randomly parametered and randomly driven non-linear vibrating systems has been tackled by combining two Monte Carlo variance reduction strategies into a single framework (Chapter 2). The first of these strategies is based on the application of the Girsanov transformation to account for the randomness in dynamic excitations and, the second approach is fashioned after the subset simulation method to deal with randomness in system parameters. A novel experimental test procedure to estimate the reliability of structural dynamical systems under excitations specified via random process models has been proposed (Chapter 3). The samples of random excitations to be used in the test are modified by the addition of an artificial control force. An unbiased estimator for the reliability is derived based on measured ensemble of responses under these modified inputs based on the tenets of Girsanov’s transformation. The study observes that an acceptable choice for the control force (that can reduce the sampling variance of the estimator) can be made solely based on experimental techniques. This permits the proposed procedure to be applied in the experimental study of time variant reliability of complex structural systems which are difficult to model mathematically. Illustrative example consists of a multi-axes shake table study on bending-torsion coupled, geometrically non-linear, five-storey frame under uni/bi-axial, non-stationary, random base excitation. The first order reliability method (FORM) and inverse FORM have been extended to handle the problem of updating reliability models for existing, statically loaded structures based on measured responses (Chapter 4). The proposed procedures are implemented by combining Matlab based reliability modules with finite element models residing on the Abaqus software. Numerical illustrations on linear and non-linear frames are presented. A solution strategy within the framework of Monte Carlo simulation based dynamic state estimation method and Girsanov’s transformation for variance reduction has been developed to tackle the problem of updating the reliability of instrumented structures based on measured response under random dynamic loading (Chapter 5). For linear Gaussian state space models, the solution is developed based on continuous version of the Kalman filter, while, for non-linear and (or) non-Gaussian state space models, bootstrap particle filters are adopted. Results from laboratory testing of an archetypal five storey bending-torsion coupled frame under seismic base motions form the basis of one of the illustrative examples. A set of three annexures contain details of numerical methods for discretizing Ito’s differential equations (Annexure 1), working of the Girsanov transformation through Kolmogorov’s equations (Annexure 2) and tools for interfacing Matlab and Abaqus codes (Annexure 3).

CoordenaÃÃo de AperfeiÃoamento de Pessoal de NÃvel Superior / Neste trabalho, um estudo da influencia da seleÃÃo de variantes sobre a cristalografia apÃs a transformaÃÃo martensÃtica no Maraging foi feito. O estudo cobriu a transformaÃÃo sob deformaÃÃo elÃstica e tambÃm sob deformaÃÃo plÃstica. No aÃo Maraging, austenita se transforma em martensita eu uma temperatura em torno de 200ÂC, nÃo importando a velocidade de resfriamento. Para simular a transformaÃÃo durante a deformaÃÃo elÃstica, ensaios de traÃÃo foram feitos em um forno acoplado a uma mÃquina de ensaios universais com uma tensÃo aplicada abaixo do limite de escoamento do material. A amostra foi aquecida atà 850ÂC, o forno foi aberto e a amostra resfriada ao ar sob tensÃo constante. Para estudar a influencia da deformaÃÃo plÃstica antes da deformaÃÃo, amostras foram deformadas plasticamente na temperatura acima da Ms (temperatura de inÃcio da martensita), a forÃa externa atuando sobre a amostra foi removida e o material sofreu a transformaÃÃo martensÃtica por resfriamento ao ar. Figuras de pÃlos foram medidas por EBSD (Electron Back-Scatter Diffraction) em ambas as condiÃÃes e comparadas com as figuras de pÃlos calculadas assumindo os modelos de Patel-Cohen e Taylor-Bishop-Hill. A orientaÃÃo da austenita mÃe foi obtida por envelhecimento na temperatura de 650ÂC e pelo uso de grÃos austenÃticos reconstruÃdos matematicamente. Os resultados mostraram que o modelo de Patel-Cohen foi mais adequado para a deformaÃÃo elÃstica enquanto que Taylor-Bishop-Hill foi melhor para a deformaÃÃo plÃstica. / In this work a study of the influence of variant selection on the crystallography after martensitic transformation in Maraging was studied. The study covered both the transformation under elastic deformation and also during plastic deformation. In Maraging steel, austenite becomes martensite at a temperature around 200oC regardless of the cooling speed. To simulate the transformation during elastic deformation, a tensile test was performed in a furnace attached to a universal testing machine with an applied stress below the yield strength of the material. The specimen was heated to 850o C, the furnace was opened and the sample cooled in air under a constant stress. To study the influence of plastic deformation before transformation, samples were plastically deformed in a temperature above Ms (martensite start temperature), the external force acting on the sample was removed and the material was allowed to transform into martensite by cooling in air. Pole figures were measured by EBSD (Electron Back-Scatter Diffraction) in both conditions and compared with calculated pole figures assuming Patel-Cohen model and Taylor-Bishop-Hill model. The orientation of the parent austenite was obtained either by reversing the austenite by heating at 650  C and by using the mathematically reconstructed austenite grains. Results showed that Patel-Cohen model were more suitable to elastic deformation while Taylor-Bishop-Hill model was more appropriated to plastic deformation.

Made available in DSpace on 2015-09-25T12:22:15Z (GMT). No. of bitstreams: 1 AlfredinaRosaOliveiraDoVale.pdf: 2309589 bytes, checksum: 64ba9fd0b60287525fad5aa22a3237dc (MD5) Previous issue date: 1999-07-20 / As far as textual production is concerned, this piece of research aims at describing the deviants as determinants of linguistic changes. Such deviants found in signs and notices (i.e. the conductive means of the collected messages), are exposed in public places in Campina Grande (PB). The main objective of this work is thus to identify, from the occurrences of these deviants, the possibilities to change the Brazilian spelling rules which may come to happen in the medium and/or long term. To carry out our research, we have based the study on two main theoretical moments: the first, a diachronic study from the 8th to the 10th century, divided in to six volumes HAUL, PAIVA, SPINA, MOREL PINTO, MARTINS and PIMENTEL PINTO entitled História da Língua Portuguesa. The second, a synchronic study, had two of PIMENTEL PINTO s works as a starting point: A língua escrita no Brasil (1986) and O português popular escrito (1990) and BAGNO s Preconceito lingüístico (1999). After detecting, selecting and categorizing the deviants (345 occurrences), we started the analysis, which we divided into two parts: the dismemberment of the diacritcs and the examination of the orthographic evidences in these changes. The analysis being concluded, a quantitative survey of the collected deviants was made in order to observe the incidence of these occurrences. The results so far seem to lead to a brief phonetic accommodation in the Brazilian Portuguese which will gradually abolish the general diacritic marks. As to spelling evidences, they are based on the metaplams of addition, subtraction, assimilation, and exchange. The latter is the most frequent case, which highlights the substitution of the grapheme s for the grapheme z , when it comes between two vowels. The results still show the frequent use of anglicism, or of its presence through the graphemes k and y . Thus, the analysis concludes that by being the act of writing signs and notices an uncommon situation to the ordinary man, it is this very fact that may justify the spontaneous occurrence of the deviant, stimulating linguistic changes which are considered non-acceptable at first but are accepted by the standard variant after a certain period of time. / Esta pesquisa, sob a perspectiva da produção textual, procura descrever os desvios como agentes determinadores de mudanças lingüísticas. Estes, localizados em porta-textos (o veículo condutor das mensagens coletadas), estão afixados em locais públicos de Campina Grande (PB). Identificar, a partir das incidências dos desvios, as possibilidades de mudanças no sistema ortográfico brasileiro, que poderão vir a ocorrer a médio e/ou longo prazo, é a meta principal deste trabalho. Para tal, apoiamo-nos em dois momentos teóricos: o primeiro, um estudo diacrônico, do Século XIII ao Século XX, distribuído em seis volumes HAUY, PAIVA, SPINA, MOREL PINTO, MARTINS e PIMENTEL PINTO intitulados História da Língua Portuguesa. O segundo, um estudo sincrônico, teve como ponto de partida duas obras de PIMENTEL PINTO: A Língua escrita no Brasil (1986) e O português popular escrito (1990). E, como ponto de chegada, a obra de BAGNO, intitulada Preconceito lingüístico (1999). Constatados os desvios (345 ocorrências), selecionados e categorizados, iniciamos a análise dividida em dois momentos: o desmembramento dos diacríticos e o exame das evidências (orto)gráficas em processo. Concluída a análise, foi feito um levantamento quantitativo dos desvios coletados, para observar-se a incidência das ocorrências. Os resultados obtidos acenam para uma breve acomodação fonética na língua portuguesa brasileira que, gradativamente, deverá abolir os diacríticos gerais. Quanto às evidências ortográficas, estas têm sua base nos metaplasmos de adição, subtração, assimilação e permuta. Este é o caso mais freqüente, destacando-se a substituição do grafema s pelo grafema z , quando aquele surge entre duas vogais. Os resultados ainda evidenciam o uso freqüente do anglicismo, ou da marca deste, através dos grafemas k e y . Assim, a análise conclui que sendo o ato de grafar uma situação rara para o homem comum, é esta realidade, possivelmente, que justifica o surgimento espontâneo do desvio, provocando alterações lingüísticas, execradas a princípio e aceitas posteriormente pela variante padrão.

CoordenaÃÃo de AperfeiÃoamento de Pessoal de NÃvel Superior / O presente trabalho visou estudar o efeito da deformaÃÃo plÃstica prÃvia por laminaÃÃo e o efeito da deformaÃÃo por traÃÃo no processo de seleÃÃo de variantes durante a transformaÃÃo martensÃtica no aÃo inoxidÃvel austenÃtico AISI 301L. Foram comparadas amostras previamente laminadas e deformadas em ensaio de traÃÃo com amostras apenas deformadas plasticamente em traÃÃo. Aspectos relativos a macrotextura obtidos pela tÃcnica de difraÃÃo de Raios-x e microtextura obtidos por difraÃÃo de elÃtrons retro-espalhados (EBSD) foram estudados. A macrotextura analisou a evoluÃÃo das principais componentes de textura da fase martensÃtica a partir do cÃlculo das funÃÃes de distribuiÃÃo de orientaÃÃo cristalogrÃfica (FDOC). As figuras de pÃlos obtidas por EBSD para grÃos selecionados foram comparadas com figuras de pÃlos calculadas utilizando a teoria fenomenolÃgica da cristalografia da transformaÃÃo martensÃtica cuja sigla em inglÃs à (PMTC). O modelo de Patel-Cohen para simular a influÃncia da tensÃo aplicada durante o processo de transformaÃÃo martensÃtica foi utilizado. Os resultados mostraram que a textura da martensita induzida por deformaÃÃo à tÃpica de uma microestrutura cÃbica de corpo centrado (CCC). Mostraram tambÃm que as amostras apenas tracionadas seguiram o modelo de Patel-Cohen para a seleÃÃo de variantes. Jà as amostras prÃ-deformadas por laminaÃÃo apresentaram uma maior dispersÃo em relaÃÃo ao modelo principalmente as que tiveram posteriormente pouca deformaÃÃo plÃstica por traÃÃo. / The present work aimed to study the effect of the plastic prior strain for rolling and the effect of the strain for tensile test in the process of variants selection during the martensitic transformation in the austenitic stainless steel AISI 301L. There were compared samples previously rolled and deformed in tensile test with samples only plastically deformed in tensile test. Relative aspects to macrotexture obtained by the technique of diffraction of X-rays and microtexture obtained by Electron backscattered diffraction (EBSD) were studied. The macrotexture analysed the evolution of the principal texture components of the martensitic phase from the calculation of the orientation distribution function (ODF). The pole figures obtained by EBSD for selected grains were compared with pole figures calculated using the phenomenological theory of martensite crystallography whose acronym in English is (PMTC). The model of Patel-Cohen to simulate the influence of the tension applied during the process of martensitic transformation was used. The results showed that the texture of the deformation induced martensite is typical of a body-centered cubic microstructure. They showed also that the only tensile samples followed the model of Patel-Cohen for the variants selection. The prior deformed samples by rolling presented a bigger dispersal regarding model principally those who subsequently had little plastic deformation for traction.

This Master’s thesis is aimed at improving the management of artifacts in the context of a joint-project between Jönköping University with the SEMCO project and industrial partner, a company involved in developing software for safety components. Both have a slightly distinct interest but this project can serve both parties. Nowadays feature modelling is efficient way for domain analysis. The purpose of this master thesis is to analysis existing four popular feature diagrams, to find out commonalities between each of them and conclude results to give suggestions of how to use existing notation systems efficiently and according to situations. The developed software based on knowledge established from research analysis. Two notation systems which are suggested in research part of the thesis report are implemented in the developed software “NotationManager”. The development procedures are also described and developer choices are mentioned along with the comparisons according to the situations Scope of the research part as well as development is discussed. Future work for developed solution is also suggested.

Mainly two different morphologies of martensite can be obtained in steels depending on the amount of alloying elements. The first morphology, referred to as lath martensite, forms in low alloy, low carbon steels. It is, by far, the most extensively studied form of martensite due to its industrial applications. The second morphology of martensite, referred to as plate martensite, forms in highly alloyed and in high carbon steels and in particular in Fe-High Ni alloys. In this case, the transformation product is disc shaped and internally twinned. This morphology is the only form of martensite that has the potential to exhibit shape memory properties. It is therefore of great interest to understand the mechanisms of its formation. This is investigated in the present dissertation through the study of the martensitic transformation occurring in a Fe-30.5%Ni-0.155%C alloy. More precisely, the influence of stress and grain size on the crystallography of plate martensite is discussed in the general framework of the phenomenological theory of martensite crystallography. This theory allows associating a unique shape deformation to each orientational variant. In this way, the experimental observations carried out at different length scales by means of optical microscopy, EBSD and TEM can be used to infer the transformation path followed under different conditions. Firstly, the burst configurations of variants observed in coarse-grained austenite under stress free conditions are rationalized by considering the mechanical couplings between the variants. It is shown that self-accommodating and autocatalytic couplings are responsible for the formation of hierarchical configurations of variants. More precisely, the transformation is shown to occur through the alternate formation of perpendicular plate groups of variants. Self-accommodation is the dominant coupling between variants of the same plate group while autocatalytic couplings are responsible for the transfer of the transformation from one generation to the next. It is suggested that the plastic accommodation of the shape deformation plays a dominant role in propagating the transformation to a lower length scales. Secondly, the influence of a uniaxial stress state on the transformation is studied. It is seen experimentally that only the most favoured variants are systematically formed in coarse Cube grains while coarse non-Cube grains generally transform into plate groups of variants that are only moderately favoured by the stress. These observations are well explained by considering the interaction energy between the applied stress and the shape deformation associated with the transformation. Thirdly, the influence of the austenitic grain size on the transformation is also studied. A decrease in grain size is seen to decrease the martensite start temperature. For a grain size below about 10µm, the thermal transformation in liquid nitrogen is indeed suppressed in the present alloy. This observation is related to the increasing yield strength of austenite as the grain size is reduced. A noticeable change in the morphology of martensite also accompanies the decrease in grain size. Indeed, martensite forming in coarse-grained austenite is mostly lens shaped and partially twinned while it appears plate shaped and fully twinned in smaller grains. Furthermore, martensite forming in fine-grained austenite develops self-accommodating configurations suggesting that most of the transformation deformations are elastically accommodated in this case. This is believed to be related to the observance of a shape memory effect in the present alloy in its fine-grained condition. / Doctorat en Sciences de l'ingénieur et technologie / info:eu-repo/semantics/nonPublished