We present efficient and globally convergent solvers for several classes of plasticity models. The models in this work are formulated in the primal form as energetic rate-independent systems with an elastic energy potential and a plastic dissipation component. Different hardening rules are considered, as well as different flow rules. The time discretization leads to a sequence of nonsmooth minimization problems. For small strains, the unknowns live in vector spaces while for finite strains we have to deal with manifold-valued quantities. For the latter, a reformulation in tangent space is performed to end up with the same dissipation functional as in the small-strain case. We present the Newton-type TNNMG solver for convex and nonsmooth minimization problems and a newly developed Proximal Newton (PN) method that can also handle nonconvex problems. The PN method generates a sequence of penalized convex, coercive but nonsmooth subproblems. These subproblems are in the form of block-separable small-strain plasticity problems, to which TNNMG can be applied. Global convergence theorems are available for both methods. In several numerical experiments, both the efficiency and the flexibility of the methods for small-strain and finite-strain models are tested.

Les procédés d’élaboration de pièces composites par infusion de résine, malgré leurs nombreux avantages, peinent à s’imposer dans les phases de production industrielle en raison de difficultés pour les maitriser. Ainsi, en partenariat avec ESI Group, un modèle complet pour la simulation de ces procédés est développé à l’ENSM-SE depuis les travaux précurseurs de P. Celle.Nos travaux portent sur la généralisation de ce modèle afin de traiter des cas, ainsi que sur son extension à la simulation des écoulements « post-infusion ». L'approche repose sur un découpage du domaine en trois zones (drainant, préformes imprégnées, préformes sèches) consistant ainsi à coupler un écoulement de Stokes dans le drainant à un écoulement de Darcy dans les préformes. De plus, l'influence mutuelle de la résine sur le comportement des préformes et de la déformation des préformes sur la perméabilité est considérée, à travers la loi de Terzaghi et des lois exprimant la perméabilité en fonction de la fraction de fibres, paramètre accessible uniquement dans une approche 3D mécanique couplée. Enfin, le procédé est découpé en trois phases : compression initiale des préformes sèches, remplissage et « post-infusion ». Les méthodes numériques, développées dans ces travaux, s'appliquent à des cas réels d'infusion souvent mis de côté dans les publications récentes car inaccessibles, impliquant des perméabilités très faibles (~10-15 m²), un drainant fin (~1 mm) et des géométries complexes.Cette approche innovante a été implémentée dans un code de calcul industriel (ProFlotTM), validée analytiquement sur des cas tests et expérimentalement sur des cas industriel dans le cadre du projet européen INFUCOMP. / Composite manufacturing processes by resin infusion, despite their many benefits, struggle to establish themselves in the industrial production phases due to difficulties to control them. So, in partnership with ESI Group, a comprehensive model for the simulation of these processes is developed at the ENSM-SE since the pioneering work of P. Celle.Our work focuses on the generalization of this model to handle complex industrial cases in three dimensions, as well as its extension to “post-infusion” flow simulation. The approach is based on three domains decomposition of the field (Distribution medium, impregnated preforms, dry preforms) consisting in coupling a Stokes flow in the distribution medium with a Darcy flow in the preforms. In addition, the mutual influence of the resin on the preforms and of the preforms deformation on the permeability is considered, through Terzaghi’s law and models expressing the permeability as a function of the fibre fraction, data only accessible with a 3D coupled mechanical approach. Finally, the process is divided into three phases: initial compression of dry preforms, filling and “post-infusion”. The numerical methods developed in this work, apply to real infusion cases often discarded in recent publications, involving very low permeability (~10-15 m²), thin distribution medium (~ 1 mm) and complex geometries (3D curved).This innovative approach has been implemented in an industrial simulation code (ProFlotTM), validated analytically over test cases and experimentally over industrial cases in the European project INFUCOMP.

Cette thèse a pour objectif le développement d'une stratégie d'identification des paramètres de plasticité et d'endommagement jusqu'à amorçage, pour des métaux ductiles.Un formalisme logarithmique est utilisé pour simuler les grandes déformations subies par les éprouvettes et une formulation non-locale multi-champ permet de simuler l'adoucissement indépendamment du maillage utilisé et d'éviter le verrouillage volumique.La Corrélation d'Images Digitales est utilisée pour obtenir des mesures hétérogènes plein champ à partir d'éprouvettes entaillées.La stratégie proposée s'appuie sur des observations microscopiques et sur une approche d'identification par recalage de modèle éléments finis (FEMU), visant à minimiser l'écart entre une mesure et son pendant simulé. L'écart est exprimé en termes de force et déplacement grâce à une normalisation appropriée. L'application de la FEMU est guidée par des analyses de sensibilité.La robustesse de la comparaison essai-calcul est assurée par l'application de conditions au bord mesurées. L'effet négatif de l’incertitude de mesure est mis en évidence et une solution de filtrage innovante est proposée.La stratégie est appliquée pour l'identification des paramètres de l'alliage Inconel625. Elle permet de reproduire l'amorçage pour des éprouvettes planes, en termes de réponse macroscopique et de localisation des sites d'amorçage. / This thesis proposes an identification strategy for plastic behaviour and damage up to the onset of fracture, for an application to ductile metals.A logarithmic finite strain formulation is used to simulate the large deformations undergone by the specimens, while a locking-free non-local formulation allows a mesh independent simulation of the softening behaviour.Digital Image Correlation is used to obtain heterogeneous full-field measurements from tensile tests on notched specimens.The identification strategy is based both on microscopic observations and on a Finite Element Model Updating (FEMU) technique, according to which the parameters are identified by minimizing the discrepancy between experiment and simulation. The discrepancy is quantified both in terms of displacement and force thanks to an appropriate normalization. The application of FEMU is guided using sensitivity analysis.The robustness of the comparison between simulation and measurement is ensured by prescribing measured displacements as boundary conditions for the simulation. The negative effect of the measurement uncertainty is underlined, and an innovative filtering approach is proposed.The proposed strategy is used to identify the materials' parameters of alloy Inconel625. It allows to reproduce the onset of fracture for flat specimens, both in terms of macroscopic response and crack initiation location.

Este trabalho apresenta uma teoria de barras não-linear geometricamente exata, com multi-parâmetros para a representação geral de deslocamentos no plano da seção transversal (distorção) e também fora do plano da seção (empenamento). A formulação apresentada constitui-se em uma extensão de trabalhos anteriores, [1] a [6], [8] e [9], no sentido de que a hipótese de seção rígida (Timoshenko) e a função de empenamento elástico de Saint-Venant foram removidos. Essa abordagem define os esforços internos energeticamente conjugados, atuantes na seção transversal, em função de deformações e tensões generalizadas, baseadas no conceito de vetor diretor da seção transversal. Além da importância prática, o uso do vetor diretor simplifica a formulação das equações de equilíbrio e a imposição das condições de contorno, tanto na forma fraca quanto na forma forte do equilíbrio. Além disso, facilita a obtenção da matriz de rigidez tangente, resultando sempre simétrica pra materiais hiper-elásticos e carregamento externo conservativo, mesmo em situações distantes da condição de equilíbrio. Permite também a introdução de graus de liberdade independentes para descrever tanto os deslocamentos no plano quanto fora do plano da seção transversal. Equações constitutivas tri-dimensionais adequadas para problemas com grandes deslocamentos e grandes deformações podem ser implementadas sem a ocorrência de enrijecimentos espúrios. A formulação é absolutamente geral e sua extensão para materiais inelásticos, em particular materiais elasto-plásticos, é imediata uma vez qua a integração de tensões com carregamentos incrementais está disponível. Rotações finitas são tratadas através da expressão de Euler-Rodrigues em uma abordagem puramente Lagrangeana. Assume-se o eixo reto como configuração de referência da barra, porém, barras inicialmente curvas também podem ser consideradas como configurações de referência deformadas, sem tensões iniciais, obtidas a partir de configurações inicialmente retas [11]. É importante ressaltar que a teoria apresentada permite uma modelagem consistente e precisa de distorções da seção transversal, típicas de perfis metálicos esbeltos dobrados a frio. Acredita-se que esta seja uma das principais contribuições dessa formulação como opção ao uso de modelos de cascas. / The main purpose of this work is to present a fully nonlinear geometrically-exact multi-parameter rod model that incorporates general in-plane cross-sectional changes as well as general out-of-plane cross-sectional warping. The formulation constitutes an extension of the earlier works presented in [1] to [6], [8] and [9], in the sense that the restrictions to a rigid cross-section and to a Saint-Venant-like elastic warping are now removed from the theory. Our approach defines energetically conjugated cross-sectional resultants in terms of generalized stresses and strains, based on the concept of a cross-section director. Besides their practical importance, the use of cross-sectional resultants simplifies the derivation of equilibrium equations and the enforcement of boundary conditions, in either weak or strong senses. In addition, the corresponding tangent bilinear weak form is obtained in a more expedient way, rendering always symmetric for hyperelastic materials and conservative loadings (even far from equilibrium states). Definition of a cross-section director plays a central role in the present model. Accordingly, it allows the introduction of independent degrees-of-freedom to describe both the in-plane cross-sectional changes and the out-of-plane warping. Fully three-dimensional finite strain constitutive equations can therefore be employed with no spurious stiffening. The ideas are general and extension to inelastic rods, in particular to those of elastoplastic materials, is straightforward once a stress integration scheme within a time step is at hand. Finite rotations are treated here by the Euler-Rodrigues formula in a pure Lagrangean framework. We assume a straight reference configuration for the rod axis, but initially curved rods can also be considered if regarded as a stress-free deformed state from the straight position (see [11]). The use of convective non-Cartesian coordinate systems is this way avoided and only components on orthogonal frames are employed. Moreover, initial curvatures that are completely independent of the isoparametric concept are possible to be attained, which can be used even in (for example) straight finite elements. Altogether, the present assumptions allow a consistent basis for the proper representation of profile (distortional) deformations, which are typical of coldformed thin-walled rod structures. We believe this is one of the main features of our formulation, as the use of more complex shell models in order to capture such phenomena becomes unnecessary.

O trabalho se baseia em uma formulação numérica (Método dos Elementos Finitos Posicional) que é combinada a um modelo viscoelástico adequado (Kelvin-Voigt adaptado), o que direciona para o cumprimento do objetivo: a simulação de sólidos viscoelásticos em deformações finitas e de fluidos viscosos. A formulação desenvolvida é Lagrangeana total descrita para posições, permitindo aplicações em não linearidade dinâmica (com a utilização do método de Newton-Raphson para solução do sistema de equações não lineares e integração temporal via algoritmo implícito de Newmark) e sua combinação com um modelo viscoelástico coerente é deduzida neste trabalho. Inicialmente, são resolvidos problemas com elemento de chapa bidimensional, porém o elemento finito final utilizado é de sólido prismático de base triangular. Dois modelos são adotados para consideração do comportamento viscoelástico, (i) um modelo modificado de Kelvin-Voigt associado ao modelo constitutivo de Saint-Venant-Kirchhoff e (ii) um modelo visco-hiperelástico completo coerente para deformações finitas desenvolvido a partir da decomposição multiplicativa sobre o gradiente da função mudança de configuração em uma parcela volumétrica e duas isocóricas. Foram selecionados e comentados 15 exemplos em detalhe, abrangendo todas as etapas desta pesquisa, com problemas elásticos, dinâmicos, viscoelásticos em pequenas e grandes deformações, de flexão, de impacto e de fluidos viscosos. Os resultados obtidos para os exemplos de validação foram satisfatórios, coerentes com as referências, e o conjunto das análises conduzidas mostram a potencialidade da formulação alternativa desenvolvida neste trabalho. / The work is based on a numerical formulation (Positional Finite Element Method) combined with a suitable viscoelastic model (adapted Kelvin-Voigt), what directs to achieving its main goal: the simulation of viscoelastic solids in finite strain and of viscous fluids. The developed formulation is total Lagrangian described for positions, allowing applications in nonlinear dynamics (using the Newton-Raphson method for solution of the system of nonlinear equations, and performing time integration via an implicit Newmark algorithm); its combination with adequate viscoelastic model is shown step-by-step in this work. Initially, problems are solved using two-dimensional plate element, but the final finite element is a triangular-based prismatic solid. Two models are adopted in order to consider the viscoelastic behavior, (i) a modified Kelvin-Voigt model associated with the Saint-Venant-Kirchhoff constitutive model, and (ii) a coherent visco-hyperelastic model for finite deformations developed from the multiplicative decomposition over the deformation gradient in one volumetric and two isochoric parts. 15 examples were selected and commented in detail, comprehending all stages of this research, solving problems that are elastic, dynamic, viscoelastic under small and large strain, under flexural behavior, submitted to impact, and of viscous fluids problems. The results obtained for the validation examples were satisfactory, consistent with the references, and the whole of the conducted analysis shows the potentials of the alternative formulation developed in this work.

Este trabalho apresenta uma teoria de barras não-linear geometricamente exata, com multi-parâmetros para a representação geral de deslocamentos no plano da seção transversal (distorção) e também fora do plano da seção (empenamento). A formulação apresentada constitui-se em uma extensão de trabalhos anteriores, [1] a [6], [8] e [9], no sentido de que a hipótese de seção rígida (Timoshenko) e a função de empenamento elástico de Saint-Venant foram removidos. Essa abordagem define os esforços internos energeticamente conjugados, atuantes na seção transversal, em função de deformações e tensões generalizadas, baseadas no conceito de vetor diretor da seção transversal. Além da importância prática, o uso do vetor diretor simplifica a formulação das equações de equilíbrio e a imposição das condições de contorno, tanto na forma fraca quanto na forma forte do equilíbrio. Além disso, facilita a obtenção da matriz de rigidez tangente, resultando sempre simétrica pra materiais hiper-elásticos e carregamento externo conservativo, mesmo em situações distantes da condição de equilíbrio. Permite também a introdução de graus de liberdade independentes para descrever tanto os deslocamentos no plano quanto fora do plano da seção transversal. Equações constitutivas tri-dimensionais adequadas para problemas com grandes deslocamentos e grandes deformações podem ser implementadas sem a ocorrência de enrijecimentos espúrios. A formulação é absolutamente geral e sua extensão para materiais inelásticos, em particular materiais elasto-plásticos, é imediata uma vez qua a integração de tensões com carregamentos incrementais está disponível. Rotações finitas são tratadas através da expressão de Euler-Rodrigues em uma abordagem puramente Lagrangeana. Assume-se o eixo reto como configuração de referência da barra, porém, barras inicialmente curvas também podem ser consideradas como configurações de referência deformadas, sem tensões iniciais, obtidas a partir de configurações inicialmente retas [11]. É importante ressaltar que a teoria apresentada permite uma modelagem consistente e precisa de distorções da seção transversal, típicas de perfis metálicos esbeltos dobrados a frio. Acredita-se que esta seja uma das principais contribuições dessa formulação como opção ao uso de modelos de cascas. / The main purpose of this work is to present a fully nonlinear geometrically-exact multi-parameter rod model that incorporates general in-plane cross-sectional changes as well as general out-of-plane cross-sectional warping. The formulation constitutes an extension of the earlier works presented in [1] to [6], [8] and [9], in the sense that the restrictions to a rigid cross-section and to a Saint-Venant-like elastic warping are now removed from the theory. Our approach defines energetically conjugated cross-sectional resultants in terms of generalized stresses and strains, based on the concept of a cross-section director. Besides their practical importance, the use of cross-sectional resultants simplifies the derivation of equilibrium equations and the enforcement of boundary conditions, in either weak or strong senses. In addition, the corresponding tangent bilinear weak form is obtained in a more expedient way, rendering always symmetric for hyperelastic materials and conservative loadings (even far from equilibrium states). Definition of a cross-section director plays a central role in the present model. Accordingly, it allows the introduction of independent degrees-of-freedom to describe both the in-plane cross-sectional changes and the out-of-plane warping. Fully three-dimensional finite strain constitutive equations can therefore be employed with no spurious stiffening. The ideas are general and extension to inelastic rods, in particular to those of elastoplastic materials, is straightforward once a stress integration scheme within a time step is at hand. Finite rotations are treated here by the Euler-Rodrigues formula in a pure Lagrangean framework. We assume a straight reference configuration for the rod axis, but initially curved rods can also be considered if regarded as a stress-free deformed state from the straight position (see [11]). The use of convective non-Cartesian coordinate systems is this way avoided and only components on orthogonal frames are employed. Moreover, initial curvatures that are completely independent of the isoparametric concept are possible to be attained, which can be used even in (for example) straight finite elements. Altogether, the present assumptions allow a consistent basis for the proper representation of profile (distortional) deformations, which are typical of coldformed thin-walled rod structures. We believe this is one of the main features of our formulation, as the use of more complex shell models in order to capture such phenomena becomes unnecessary.

In this thesis a theory for large deformation of plates is presented. Herein aspects of the common 3D-theory for large deformation with the Kirchhoff hypothesis for reducing the dimension from 3D to 2D is combined. Even though the Kirchhoff assumption was developed for small strain and linear material laws, the deformation of thin plates made of isotropic non-linear material was investigated in a numerical experiment. Finally a heavily deformed shell without any change in thickness arises. This way of modeling leads to a two-dimensional strain tensor essentially depending on the first two fundamental forms of the deformed mid surface. Minimizing the resulting deformation energy one ends up with a nonlinear equation system defining the unknown displacement vector U. The aim of this thesis was to apply the incremental Newton technique with a conformal, C^1-continuous finite element discretization. For this the computation of the second derivative of the energy functional is the key difficulty and the most time consuming part of the algorithm. The practicability and fast convergence are demonstrated by different numerical experiments.

In the simulation of deformations of plates it is well known that we have to use a special treatment of the thickness dependence. Therewith we achieve a reduction of dimension from 3D to 2D. For linear elasticity and small deformations several techniques are well established to handle the reduction of dimension and achieve acceptable numerical results. In the case of large deformations of plates with non-linear material behaviour there exist different problems. For example the analytical integration over the thickness of the plate is not possible due to the non-linearities arising from the material law and the large deformations themselves. There are several possibilities to introduce a hypothesis for the treatment of the plate thickness from the strong Kirchhoff assumption on one hand up to some hierarchical approaches on the other hand.:1. Introduction 2. The 3D-deformation energy 3. Basic differential geometry of shells 4. Kirchhoff assumption and the deformed plate 5. Plate energy and boundary conditions 6. Numerical example

any experiments demonstrate that isotropic ductile materials used in engineering applications develop anisotropic damage and shows significant variation in elongation to failure. This anisotropic damage is manifest by material microstructural heterogeneities and morphological changes during deformation. The variation in elongation to the failure could be attributed to the uncertainties in the material microstructure and loading conditions. To study this deformation induced anisotropy arising from the initial material heterogeneities, we first performed uncertainty analysis using current form on an internal state variable plasticity and isotropic damage model (Bammann, 1984; Horstemeyer, 2001) to quantify the effect due to variations in material microstructure and loading conditions on elongation to failure. We extend the current isotropic damage form of theory into an anisotropic damage form for ductile material in which material heterogeneities are introduced based on damage distribution functions converted into a damage tensor of second rank. The outcome of this research is a physically motivated, uncertainty-based, anisotropic damage constitutive model that links microstructural features to mechanical properties. This was accomplished by pursuing three sub goals: (1) develop and quantify uncertainty related to material heterogeneities, (2) develop a methodology related to a higher order tensorial rank of damage for void nucleation and void growth, and (3) integrate thermodynamically constrained damage with a rate dependent plasticity constitutive material model. Later, we also proposed a new ISV theory that physically and strongly couples deformation due to damage-related internal defects to metal plasticity.

Στην παρούσα Μεταπτυχιακή Διατριβή αναλύονται τα παραμορφωτικά και συστασιακά (πετρογραφικά - ορυκτοχημικά) χαρακτηριστικά μυλωνιτιωμένων λιθολογιών από την πλαστική ζώνη διάτμησης του Φελλού (Βορειοδυτική Άνδρος). Η ζώνη διάτμησης του Φελλού είναι μια μεσοσκοπικής κλίμακας δομή, ΒΒΑ διεύθυνσης, με δομικό πάχος της τάξεως των 200 μέτρων. Το κεντρικό τμήμα της ζώνης διάτμησης φιλοξενείται σε μετα-πηλιτικές λιθολογίες και οριοθετείται από έντονα παραμορφωμένα μετα-υπερβασικά και μετα-βασικά λιθολογικά σώματα. Οι μυλωνιτιωμένες λιθολογίες της ζώνης διάτμησης χαρακτηρίζονται σαν S έως S – L τεκτονίτες. Η τεκτονική χαρτογράφηση στην περιοχή μελέτης αποκάλυψε ότι η μυλωνιτική ζώνη αναπτύχθηκε υπο-παράλληλα με το αξονικό επίπεδο ενός ήπια κεκλιμένου συγκλινοειδούς το οποίο έχει υποστεί καθολικό μετασχηματισμό. Οι ρεολογικές αντιθέσεις μεταξύ του πυρήνα της ζώνης διάτμησης και των περιθωρίων της σε συνδυασμό το τεκτονικό περιβάλλον ενός μετασχηματισμένου συγκλινοειδούς έχουν συμβάλλει στον εντοπισμό της παραμόρφωσης στην θέση ανάπτυξης της ζώνης διάτμησης. Σε χαρτογραφική κλίμακα ο προσανατολισμός των γραμμώσεων έκτασης μεταβάλλεται από ΝΝΔ , παράλληλα στη διεύθυνση της ζώνης διάτμησης, σε ΔΒΔ διεύθυνση βύθισης. Η μεταβολή στον προσανατολισμό των γραμμώσεων έκτασης δείχνει ότι η διεύθυνση κίνησης εντός της ζώνης διάτμησης διαμερίζεται χωρικά σε συνιστώσες κίνησης παράλληλα και κάθετα στην παράταξη της μυλωνιτικής φολίωσης. Ο κινηματικός διαμερισμός στην πλαστική ζώνη διάτμησης του Φελλού είναι χαρακτηριστικό γνώρισμα ζωνών διάτμησης πλάγιας συστολής. Ο κινηματικός διαμερισμός που αναγνωρίστηκε, ερευνήθηκε περαιτέρω με την εξέταση της χωρικής κατανομής των κρυσταλλογραφικών αξόνων [c] του χαλαζία, από δείγματα χαλαζιακών φλεβών και χαλαζιακών μυλωνιτών, προσανατολισμένα παράλληλα στη μυλωνιτική φολίωση και κάθετα στη γράμμωση έκτασης (ΧΖ επίπεδο ελλειψοειδούς παραμόρφωσης). Τα ιστολογικά διαγράμματα [c] αξόνων χαλαζία παρουσιάζουν μεταβολές στην τοπολογία τους σε διαφορετικά δομικά επίπεδα της ζώνης διάτμησης και διακριτές διαφορές με τα πρότυπα κρυσταλλογραφικά διαγράμματα [c] αξόνων μονοκλινικής συμμετρίας. Διακριτό χαρακτηριστικό , ειδικά για τα ανώτερα δομικά επίπεδα της ζώνης διάτμησης, είναι η εστίαση των [c] αξόνων σε σημειακά μέγιστα που προβάλλονται σε περιφερειακές θέσεις των κρυσταλλογραφικών διαγραμμάτων. Η βάση , δομικά, της ζώνης διάτμησης βρίσκεται στην ρεολογική διεπιφάνεια μετα-πηλιτών – μετα-βασιτών. Στην επαφή αυτή, ιστολογικά διαγράμματα από γειτονικά δείγματα χαλαζιακών φλεβών παρουσιάζουν συστηματικά διαγράμματα τύπου μικρών κύκλων. Η συστηματικότητα αυτή υποδηλώνει εντοπισμό της γεωμετρίας της παραμόρφωσης στην λιθολογική επαφή των μετα-πηλιτών - μετα-βασίτων. Η ποσοτική ανάλυση της παραμόρφωσης έδειξε ότι η παράμετρος Rxz μεταβάλλεται από 2.1 έως 6.45 ενώ η παράμετρος Flinn κυμαίνεται από 0.01 έως 0.93, υποστηρίζοντας και ποσοτικά ότι η γεωμετρία της παραμόρφωσης ανήκει στο πεδίο της πλάτυνσης. Η γεωμετρία της παραμόρφωσης στο πεδίο της πλάτυνσης είναι ένα επιπλέον διαγνωστικό χαρακτηριστικό των ζωνών διάτμησης πλάγιας συστολής. Η πετρογραφικη εξέταση μυλωνιτιωμένων λιθολογιών εστίασε στην αναγνώριση ζωνωμένων ορυκτών φάσεων με σκοπό την στοιχειοθέτηση των ορυκτοχημικών χαρακτηριστικών τους. Η πετρογραφική εξέταση δειγμάτων από μια επιφανειακή εμφάνιση μεταβασιτών από την βάση της μυλωνιτικής ζώνης συνέβαλλε στην αναγνώριση, σε κλίμακα λεπτής τομής, δύο λιθολογικών τύπων οι οποίοι είναι (α) Γρανατούχος – γλαυκοφανιτικός σχιστόλιθος και (β) Επιδοτιτικός - γλαυκοφανιτικός σχιστόλιθος. Η ορυκτοχημεία ζωνωμένων γρανατών και αμφιβόλων από τους δύο λιθολογικούς τύπους εξετάστηκε μέσω SEM/EDS.Η ορυκτοχημική ανάλυση οδήγησε στην αναγνώριση τριών τύπων ζώνωσης στις αμφιβόλους με τα εξής χαρακτηριστικά (α) Σκούροι πράσινοι πυρήνες σιδηρο-Κεροστίλβης με κροσσιτικά περιθώρια (β) Παλίνδρομη ζώνωση μεταξύ μπλε (σιδηρο-Γλαυκοφανής) και πράσινων αμφιβόλων (σιδηρο-Βαρροϊσίτης) και (γ) Απομονωμένοι κρύσταλλοι με κροσσιτικούς πυρήνες και ριβεκιτικά περιθώρια. Τα περιθώρια των ζωνωμένων γρανατών που εξετάστηκαν βρίσκονται σε ιστολογική ισορροπία με μπλέ αμφιβόλους, το γεγονός αυτό σε συνδυασμό με τα ορυκτοχημικά πειστήρια της κλασμάτωσης του μαγγανιου στους πυρήνες αποδεικνύει ότι η βλάστηση των γρανατών συνέβη σε αυξανόμενες συνθήκες πίεσης και θερμοκρασίας κατά την διάρκεια του υψηλής πίεσης μεταμορφικού γεγονότος. / The subject of the present contribution is the analysis of deformation in the Fellos ductile shear zone, which crops out in the island of Andros. Fellos shear zone (FSZ) is an outcrop scale NNE –striking structure with a total structural thickness of, approximately, 200 m. The central main domain of the shear zone is defined by mylonitized metapelitic rocks, bounded by strongly deformed meta-basic and meta–ultrabasic rocks both on top and bottom. Mylonitic rocks in the shear zone can be classified as S to S – L tectonites. Structural mapping revealed that the Fellos shear zone resulted from the complete transposition of a gently inclined synform the axial plane of which is orientated sub – parallel to the mylonitic foliation. The rheological contrasts between the core of the shear zone and its margins in conjunction with the structural framework of a transposed synform are first order influences to the localization of deformation. The map scale pattern of the stretching lineations in the shear zone shows that the lineation swings from a NNE orientation, trending parallel to the strike of the shear zone, to an ESE orientation. This variation shows that transport orientation in the shear zone is spatially partitioned into strike parallel and strike normal movements. This kinematic partitioning in the Fellos shear zone is a characteristic feature of transpressional high strain shear zones. The recognized partitioning was further investigated by examining the pattern of quartz [c]-axes fabrics in quartz veins oriented parallel to the mylonitic foliation as well as in quartz –rich mylonites. Quartz [c] axes fabric diagrams shows variations in their topology at different structural levels of the shear zone and distinct differences with the [c] axes patterns of monoclinic strain symmetry. Distinct feature, especially at the uppermost structural levels of the shear zone, is the point maxima clustering of the [c] axes in peripheral position of the crystallographic diagrams. At the base of the shear zone, in the rheological interface of metapelites with metabasites, the fabric diagrams from neighboring quartz vein specimens shows consistently small circle girdle pattern. This observation denotes localization in the geometry of deformation (flattening) at this lithological contact. Finite strain analysis shows that Rxz varies from 2.1 to 6.45, while the Flinn parameter range between 0.01 and 0.93, supporting quantitatively the flattening geometry of strain. Flattening strain is another diagnostic criterion of transpressional shear zones. The means to constrain the compositional features of the mylonitic rocks was mineral chemistry and petrologic analysis. Petrographic examination, specifically, of a metabasite outcrop from the base of the shear zone revealed, in thin section scale, two lithologic types : (a) Garnet blueschist and (b) Epidote blueschist. The mineral chemistry of zoned garnets and amphiboles from these petrographic types has been examined using SEM/EDS. The microchemical analysis revealed three different zoning patterns in the amphiboles which are characterized by (a) dark green Ferro – hornblende cores with crossite rims (b) Amphiboles with compositional zoning and alternations of blue (Ferro – glaucophane) and green amphiboles (Ferro – barroisite) and (c) Isolated grains with crossite cores and riebeckite rims. Compositional mapping of zoned garnets witnessed fractionation of manganese to the cores, which is the Prima facie evidence of growth zoning. In addition, the almandine rims of the zoned garnets are in textural equilibrium with blue amphiboles, observation which implies that these garnets nucleated during the HP event.