Download or read book Comportement viscoplastique des alliages de zirconium dans le domaine de temperature 20 c 400 c written by Stéphanie Graff and published by . This book was released on 2006 with total page 319 pages. Available in PDF, EPUB and Kindle. Book excerpt: De nombreuses manifestations macroscopiques de vieillissement dans les alliages de zirconium et dans le domaine de température 20°C-600°C (interaction dislocations-atomes de soluté) ont été observées dans la littérature. L’influence systématique des éléments d’addition et la caractérisation précise du domaine de vieillissement en termes de température et de vitesse de déformation restent toutefois mal connues. Cette étude a pour objectif une telle caractérisation et sa modélisation par des lois de comportement adaptées. Dans le cadre du CPR SMIRN, de nouveaux alliages de zirconium ont été spécialement élaborés à partir d’une barre de zirconium 2.2% hafnium à faible teneur en oxygène (80ppm). Des alliages enrichis en oxygène d’une part, et en niobium d’autre part, ont été caractérisés sur une large gamme de sollicitations mécaniques (traction simple, sauts de vitesse, relaxation et mesures de champs de déformation par extensométrie laser). Les phénomènes suivants ont été examinés puis modélisés : creux de sensibilité à la vitesse autour de 300°C ; arrêt de fluage à 200°C ; arrêt de relaxation à 200°C et 300°C ; hétérogénéités de déformation en traction le long du fût de l’éprouvette. Le modèle de comportement proposé est issu d’un modèle phénoménologique aujourd’hui classique de vieillissement dynamique des alliages métalliques, proposé par Estrin, Kubin et McCormick. Il comporte une variable interne caractérisant un temps de vieillissement global du matériau, ce qui le rend facile à programmer dans un code de calcul par éléments finis. La forte non-linéarité de l’équation d’évolution conduit à la simulation de bandes de localisation de vitesse de déformation plastique. Les paramètres matériau du modèle ont été identifiés pour un alliage de zirconium de référence afin de rendre compte des phénomènes précédents de vieillissement.
Download or read book Viscoplasticit et microstructures d un alliage de Titane written by Hélène Jousset and published by . This book was released on 2008 with total page 276 pages. Available in PDF, EPUB and Kindle. Book excerpt: L'étude a pour but de caractériser et d'analyser le comportement mécanique du Ti 6242-Si dans un large domaine de températures, de vitesses de sollicitation et de trajets de chargement. En effet une viscoplasticité plus marquée au voisinage de l'ambiante qu'à plus haute température caractérise de nombreux alliages de titane et de zirconium. Ce comportement inhabituel est à relier à des phénomènes d'interactions entre dislocations et atomes interstitiels (O, C, N, H), généralement décrits par les termes de " vieillissement dynamique " ou " vieillissement statique ". Les microstructures de déformation observées en microscopie électronique en transmission sur certains de ces états de déformation particuliers choisis au travers de tout le domaine de températures exploré, apportent des éclairages ponctuels sur les bases physiques possibles d'une interprétation à l'échelle microscopique des phénomènes observés et mesurés à l'échelle macroscopique. Les résultats obtenus sont alors interprétés à partir de la mobilité relative des dislocations ou groupements de dislocations, de leur interaction avec des solutés en sursaturation dans ce matériau, ou de la structure de cœur particulière de ces dislocations à basse température. L'essai de relaxation, grâce à la large gamme de vitesses de déformation qu'il couvre, a permis d'évaluer dans quelles proportions les différents régimes de déformation se mélangent à chaque température. En effet, deux modes plastiques profondément différents, en se combinant, régissent la viscoplasticité macroscopique : - dans le domaine des hautes températures (ou des faibles vitesses de déformation), le mode traînage est dominant : les dislocations coins traînent des atmosphères de solutés. - dans le domaine des basses températures (ou des vitesses élevées), c'est au contraire le mode friction qui prévaut : les dislocations se déplacent rapidement, les atomes de solutés restant quasi immobiles et ne jouant qu'un rôle de durcissement de solution solide. Dans le domaine de recouvrement de ces deux modes plastiques propres - domaine d'existence du phénomène PLC - de brusques changements de comportement peuvent donc apparaître, car la plasticité en mode friction a tendance à se rassembler localement sous forme de " bandes de vitesse ", alors que le reste de la structure ou de l'éprouvette continue à se déformer beaucoup plus lentement en mode traînage, jusqu'à atteindre le " blocage " aux plus basses températures. La plasticité du matériau est intrinsèquement hétérogène. L'étude fine des données de relaxation met en évidence la présence de " bouffées de plasticité " (strain bursts) très localisées dans le temps et dans l'espace (échelle mésoscopique). Le taux de corrélation de ces événements élémentaires détermine l'amplitude et la forme des manifestations macroscopiques (bandes de vitesse, serrations, crochets de traction,...). Les essais mécaniques ont donc permis de déterminer les frontières des différents domaines de comportement de l'alliage étudié et d'y mesurer certains paramètres macroscopiques caractéristiques tels que les énergies et les volumes d'activation apparents de ces modes plastiques. Aux températures élevées (600°C - 450°C), le mode traînage est omniprésent. Le régime de vieillissement dynamique domine au pic du domaine de l'anomalie de comportement, vers 400°C. À cette température, les capacités de restauration du matériau sont très limitées : la faible amplitude de relaxation qu'il présente est suivie d'un blocage strict de la plasticité. Le domaine des températures intermédiaires, entre 300°C et 200°C, est caractérisé par le blocage quasi-instantané de la plasticité. Dans le domaine des basses températures de l'anomalie (autour de 150°C), la plasticité est rétablie grâce à la prédominance du mode friction, et les durcissements de vieillissement et d'écrouissage s'additionnent. Enfin, à température ambiante, c'est-à-dire au voisinage de la limite basse du domaine, le vieillissement statique se manifeste.
Download or read book Properties of UO2 written by J. Belle and published by . This book was released on 1957 with total page 146 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Offshore Power Systems written by Faye H. Horn and published by . This book was released on 1974 with total page 84 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Generalized Continua as Models for Classical and Advanced Materials written by Holm Altenbach and published by Springer. This book was released on 2016-04-15 with total page 456 pages. Available in PDF, EPUB and Kindle. Book excerpt: This volume is devoted to an actual topic which is the focus world-wide of various research groups. It contains contributions describing the material behavior on different scales, new existence and uniqueness theorems, the formulation of constitutive equations for advanced materials. The main emphasis of the contributions is directed on the following items - Modelling and simulation of natural and artificial materials with significant microstructure, - Generalized continua as a result of multi-scale models, - Multi-field actions on materials resulting in generalized material models, - Theories including higher gradients, and - Comparison with discrete modelling approaches
Download or read book Generalized Models and Non classical Approaches in Complex Materials 1 written by Holm Altenbach and published by Springer. This book was released on 2018-03-24 with total page 799 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book is the first of 2 special volumes dedicated to the memory of Gérard Maugin. Including 40 papers that reflect his vast field of scientific activity, the contributions discuss non-standard methods (generalized model) to demonstrate the wide range of subjects that were covered by this exceptional scientific leader. The topics range from micromechanical basics to engineering applications, focusing on new models and applications of well-known models to new problems. They include micro–macro aspects, computational endeavors, options for identifying constitutive equations, and old problems with incorrect or non-satisfying solutions based on the classical continua assumptions.
Download or read book Generalized Continua from the Theory to Engineering Applications written by Holm Altenbach and published by Springer Science & Business Media. This book was released on 2012-10-17 with total page 403 pages. Available in PDF, EPUB and Kindle. Book excerpt: On the roots of continuum mechanics in differential geometry -- a review.- Cosserat media.- Cosserat-type shells.- Cosserat-type rods.- Micromorphic media.- Electromagnetism and generalized continua.- Computational methods for generalized continua. The need of generalized continua models is coming from practice. Complex material behavior sometimes cannot be presented by the classical Cauchy continua. At present the attention of the scientists in this field is focused on the most recent research items • new models, • application of well-known models to new problems, • micro-macro aspects, • computational effort, and • possibilities to identify the constitutive equations The new research directions are discussed in this volume - from the point of view of modeling and simulation, identification, and numerical methods.
Download or read book ECCOMAS 2012 September 10 14 2012 Vienna Austria proceedings of the 6th European Congress on Computational Methods in Applied Sciences and Engineering written by European Congress on Computational Methods in Applied Sciences and Engineering and published by . This book was released on 2012 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Mesoscale Models written by Sinisa Mesarovic and published by Springer. This book was released on 2018-11-19 with total page 348 pages. Available in PDF, EPUB and Kindle. Book excerpt: The book helps to answer the following questions: How far have the understanding and mesoscale modeling advanced in recent decades, what are the key open questions that require further research and what are the mathematical and physical requirements for a mesoscale model intended to provide either insight or a predictive engineering tool? It is addressed to young researchers including doctoral students, postdocs and early career faculty,
Download or read book Mechanics of Strain Gradient Materials written by Albrecht Bertram and published by Springer Nature. This book was released on 2020-06-30 with total page 177 pages. Available in PDF, EPUB and Kindle. Book excerpt: Over the past 50 years, strain gradient material theories have been developed for the continuum modeling of size effects in materials and structures in terms of their elasticity, plasticity and fracturing. This book puts forward a unifying perspective to combine existing theories involving the higher order gradient of the strain tensor, or of plastic strain. It begins by reviewing experimental findings on the existence (or non-existence) of size effects on the mechanics of materials. In turn, the book devises first, second and higher order strain gradient theories from general principles, and presents constitutive frameworks that satisfy thermodynamic requirements. The special case of strain gradient plasticity is then developed and illustrated via computational analyses of size effects on the plasticity of metals at small scales. In closing, the book explains the origin of gradient effects in the case of lattice structures by drawing on homogenization theory.
Download or read book Multiscale Methods in Computational Mechanics written by René de Borst and published by Springer Science & Business Media. This book was released on 2010-10-09 with total page 451 pages. Available in PDF, EPUB and Kindle. Book excerpt: This work gives a modern, up-to-date account of recent developments in computational multiscale mechanics. Both upscaling and concurrent computing methodologies will be addressed for a range of application areas in computational solid and fluid mechanics: Scale transitions in materials, turbulence in fluid-structure interaction problems, multiscale/multilevel optimization, multiscale poromechanics. A Dutch-German research group that consists of qualified and well-known researchers in the field has worked for six years on the topic of computational multiscale mechanics. This text provides a unique opportunity to consolidate and disseminate the knowledge gained in this project. The addition of chapters written by experts outside this working group provides a broad and multifaceted view of this rapidly evolving field.
Download or read book Generalized Continua as Models for Materials written by Holm Altenbach and published by Springer Science & Business Media. This book was released on 2014-07-08 with total page 336 pages. Available in PDF, EPUB and Kindle. Book excerpt: This volume presents contributions describing the micro- and macro-behaviours, new existence and uniqueness theorems, the formulation of multi-scale problems, etc. and now it is time to ponder again the state of matter and to discuss new trends and applications. The main focus is directed on the following items - Modelling and simulation of materials with significant microstructure, - Generalized continua as a result of multi-scale models, - Multi-field actions on materials resulting in generalized material models, and - Comparison with discrete modelling approaches
Download or read book Mechanics of Generalized Continua written by Gérard A. Maugin and published by Springer Science & Business Media. This book was released on 2010-03-24 with total page 337 pages. Available in PDF, EPUB and Kindle. Book excerpt: In their 1909 publication Théorie des corps déformables, Eugène and François Cosserat made a historic contribution to materials science by establishing the fundamental principles of the mechanics of generalized continua. The chapters collected in this volume showcase the many areas of continuum mechanics that grew out of the foundational work of the Cosserat brothers. The included contributions provide a detailed survey of the most recent theoretical developments in the field of generalized continuum mechanics and can serve as a useful reference for graduate students and researchers in mechanical engineering, materials science, applied physics and applied mathematics.
Download or read book EMMC2 written by A. Bertram and published by . This book was released on 1998 with total page 448 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Continuum Thermomechanics written by Gérard A. Maugin and published by Springer Science & Business Media. This book was released on 2006-04-11 with total page 428 pages. Available in PDF, EPUB and Kindle. Book excerpt: Contributed by world-renowned specialists on the occasion of Paul Germain's 80th birthday, this unique book reflects the foundational works and the intellectual influence of this author. It presents the realm of modern thermomechanics with its extraordinary wealth of applications to the behaviour of materials, whether solid or fluid. The thirty-one contributions follow an easygoing autobiographical sketch by Paul Germain, and highlight the power and richness of a methodological approach to the phenomenology of many materials. This approach combines harmoniously thermodynamics and continuum theory in order to provide exploitable, thermodynamically admissible models of a large variety of behaviours and phenomena, including those of diffusion, thermoelasticity, viscoplasticity, relaxation, hysteresis, wetting, shape-memory effects, growth, phase transitions, stability, fracture, shocks, machining of materials, microstructured solids, complex fluids, etc. Especially aimed at graduate students, researchers, and engineers in mechanical engineering and materials science, this book also presents the state of the art in an active field of research and opens new horizons in other scientific fields, such as applied mathematics and applied physics, because of the intellectual satisfaction and remarkable efficiency provided by the advocated approach.
Download or read book Physical Aspects of Fracture written by Elisabeth Bouchaud and published by Boom Koninklijke Uitgevers. This book was released on 2001-08-31 with total page 388 pages. Available in PDF, EPUB and Kindle. Book excerpt: Proceedings of the NATO Advanced Study Institute, Cargèse, France, 5-17 June 2000
Download or read book Continuum Models and Discrete Systems written by Gérard A. Maugin and published by Longman Scientific and Technical. This book was released on 1990 with total page 354 pages. Available in PDF, EPUB and Kindle. Book excerpt:
