Dissertations / Theses on the topic 'Dislocation'
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De, Cat CeÌcile. "French dislocation." Thesis, University of York, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.270049.
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Abu, Ashekh Malek. "Joint dislocation." Thesis, Sumy State University, 2014. http://essuir.sumdu.edu.ua/handle/123456789/36575.
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A joint dislocation, or luxation occurs when there is an abnormal separation in the joint, where two or more bones meet. A partial dislocation is referred to as a subluxation. Dislocations are often caused by sudden trauma on the joint like an impact or fall. A joint dislocation can cause damage to the surrounding ligaments, tendons, muscles, and nerves Dislocations can occur in any joint major (shoulder, knees, etc.) or minor (toes, fingers, etc.). The most common joint dislocation is a shoulder dislocation. Symptoms: intense pain, joint instability, deformity of the joint area, reduced muscle strength, bruising or redness of joint area, difficulty moving joint.
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Lamie, Philip Wayne. "Modern dislocation." The Ohio State University, 1986. http://rave.ohiolink.edu/etdc/view?acc_num=osu1300208224.
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Shin, Chansun. "3D discrete dislocation dynamics applied to dislocation-precipitate interactions." Grenoble INPG, 2004. http://www.theses.fr/2004INPG0116.
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La dynamique des dislocations discrètes (DDD) a été appliquée pour examiner les effets des précipités sur la plasticité des monocristaux de structure CFC. Les précipités sont modélisés par un assemblage de facettes franchissable pour une contrainte donnée. Afin de tenir compte des interactions élastiques entre les dislocations et les particules, un couplage avec la méthode des éléments finis (MEF) a été utilisé. Afin d'accélérer les temps de calculs, la 'méthode des boites' a été revisitée et une version parallèle du code a été développée en utilisant le standard du programmation 'Message Passing Interface (MPI)'. Dans un premier temps, les contraintes images créées par une particule 3D ont été calculées grâce un couplage entre la MEF et le code de DDD. Les résultats numériques ont été comparés aux solutions analytiques correspondantes. L'effet de la différence des modules d'Young sur la limite élastique et le comportement durcissant qui en découle ont ensuite été étudiés numériquement. Nous avons montré que les contraintes image ont un effet significatif sur le durcissement et les événements locaux tels que le glissement dévié et la montée. Finalement, la fatigue des matériaux durcis par des précipités cisaillables et non-cisaillables a été simulée avec le nouveau code parallèle de DDD. Les résultats obtenus grâce à nos simulations sont en accord avec nos observations experimentales et les données de la littérature. Un mécanisme de formation des bandes de glissement intense a été proposé à partir de l'observation des microstructures obtenues par simulationThe 3D Discrete Dislocation Dynamics (DDD) method has been applied to investigate the effects of precipitates on the plasticity of FCC single crystals. A method to represent the internal interfaces by a series of facets with a pre-defined strength has been proposed. For a full account of the mutual elastic interactions between dislocations and second-phase particles, the coupling method with a finite element method is extended. In order to accelerate the computing time, the serial 3D DDD algorithm has been improved by revisiting the 'box method' and a new parallel code has been developed using the standard Message passing Interface (MPI). The image stresses due to a three-dimensional particle were computed using the FEM/DDD coupling code. The numerical results have been compared to the corresponding analytical solutions. The effect of the elastic modulus mismatch on the flow stress and the subsequent hardening behavior has then been analyzed. The image stresses were found to affect significantly the work hardening and the local events such as cross slip and climb. Finally, the fatigue of precipitate-hardened materials was simulated using the new parallel DDD code. The effects of shearable and non-shearable particles on the fatigue properties were well reproduced by the simulations, and the numerical results showed good agreements with the available experimental observations in a qualitative way. The mechanism of the intense slip band formation is proposed from the observation of the simulated dislocation microstructure
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Garg, Akanksha. "Homogeneous Dislocation Nucleation." Research Showcase @ CMU, 2014. http://repository.cmu.edu/dissertations/401.
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Tighe, Stephen Patrick. "Macroscopic dislocation modelling." Thesis, University of Oxford, 1992. http://ora.ox.ac.uk/objects/uuid:e4f00d59-71b0-43c0-b141-0bb7e6108fff.
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Work-hardened metals typically possess large numbers of dislocations in complex three-dimensional configurations about which little is known theoretically. Here these large numbers of dislocations are accounted for by means of a dislocation density tensor, which is obtained by applying an averaging process to families of discrete dislocations. Some simple continuous distributions are examined and an analogy is drawn with solenoids in electromagnetism before the question of the equilibrium of dislocation configurations is studied. It is then proved that the only finite, simply-connected distribution of dislocations in equilibrium in the absence of applied stresses are ones in which all components of stress vanish everywhere. Some examples of these zero stress everywhere (ZSE) distributions are then given, and the concept of 'plastic distortion' is used to facilitate their interpretation as rotations of the crystal lattice. Plastic distortion can also be understood as a distribution of infinitesimal dislocation loops ('Kroupa loops'), and this idea is used in Chapter 4 to investigate the dislocation distributions which correspond to elastic inclusions. The evolution, under an applied stress, of some simple ZSEs is analysed, and the idea of 'polarisation' is introduced, again in analogy with electromagnetism. Finally, a mechanism is conjectured for the onset of plastic flow.
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Crenshaw, Mary. "Dislocation and materiality." Thesis, University of East London, 2018. http://roar.uel.ac.uk/7885/.
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Dislocation, and Materiality is the culmination my three years of research into artists and theorists, whose work provided me with a clearer direction in my practice as a painter. My research has enabled me to become more aware of the reasons for my current approach to painting that includes: relying on my physical energy, the inherent properties in the material/paint, defining space, memory of place that suggests urban landscape and its inhabitants. The theories of Georges Bataille on the mark, François Jullien on the Chinese concept of lifeforce, and Theodor Adorno on how dissonance is central to artistic and aesthetic process have fed the development of my creative practice. The key artists I researched -Anselm Kiefer, Julie Mehretu, Fabienne Verdier, Mark Bradford, and Phyllida Barlow - provided me with new concepts to introduce in my own work. Mehretu's paintings supplied me with the solution for incorporating political content by means of suggestive titles and expressive marking over imagery. Kiefer's rich assortment of media led me to understand how materials contribute to the meaning of a work. Verdier's gesture and physical energy encouraged me to let go of control and embrace expressionistic paint application. How Mark Bradford uses found brochures and posters from his neighbourhood, transforming them into material for his work gave me the insight that meaning can be in the actual materials. Phyllida Barlow's dynamic works made me consider how the different kinds of marks I create carry vitality and ideas communicated by the material properties of the paint.
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Bicknell, Louise Susan, and n/a. "Genetic contributors to congenital joint dislocation." University of Otago. Dunedin School of Medicine, 2007. http://adt.otago.ac.nz./public/adt-NZDU20080211.151359.
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Understanding the molecular basis of Mendelian disorders featuring joint dislocation can enhance the knowledge of genetic or cellular pathways required in joint development, and provide candidate genes for studying related complex disorders, such as developmental dysplasia of the hip. Two strategies were employed in this project to investigate Mendelian contributors to congenital joint dislocation.
The first strategy was to investigate in-depth a gene known to be associated with joint dislocation. Missense mutations or small in-frame deletions in FLNB, encoding filamin B, have previously been associated with a spectrum of osteochondrodysplasias. Screening a larger cohort established FLNB as the sole underlying disease gene for atelosteogenesis type I and III and also boomerang dysplasia, which was previously thought clinically to be allelic to AOI. Mutations in FLNB cause a large proportion of Larsen syndrome cases with phenotypes reminiscent of the early case series reported. Atypical or "recessive" Larsen syndrome may therefore be due to a different underlying genetic aberration. The disease-associated amino acid substitutions or in-frame deletion/insertions cluster to two main regions of the filamin B protein: the calponin homology 2 domain of the actin-binding domain, and repeats 13-17 of the rod domain. To analyse the functions of these regions, yeast two-hybrid analyses were performed. No interactors were identified with the calponin homology 2 domain, which suggests the amino acid substitutions may disrupt actin binding or the regulation thereof. A candidate interactor, centromere protein J, was identified that binds to repeats 13-15, and could suggest a model for aberrant cell division seen in growth plates of bones of individuals with atelosteogenesis types I and III and boomerang dysplasia.
The second strategy used in this project was to investigate the genetic cause of a novel syndrome featuring joint dislocation. A neurocutaneous phenotype segregated in a consanguineous New Zealand family, and through a genetic mapping strategy, a significantly linked locus was identified at 10q23 (Z = 3.63), in which segregation of a common ancestral haplotype fits the linkage hypothesis of homozygosity by descent. Candidate gene analysis and subsequent screening identified a missense mutation 2350C>T in ALDH18A1, which predicts the substitution H784Y in the encoded protein [Delta]�-pyrroline-5-carboxylate synthase (P5CS). The known function of P5CS in proline and ornithine biosynthesis was not affected by the presence of H784Y in an indirect assay, and therefore the hypothesis proposed was that a novel, unknown moonlighting function of P5CS is perturbed causing the phenotype segregating in the family. As an initial exploration of functions of P5CS in the cell, yeast two-hybrid analysis was undertaken.
This project examined the contribution of two genes, FLNB and ALDH18A1, to Mendelian congenital joint dislocations. How the cellular functions of the encoded proteins in the cytoskeleton, metabolism, or signal transduction, are critical for joint development is ill understood. Future investigations aimed at identifying candidate genes that confer susceptibility to developmental dysplasia of the hip should consider candidate genes that encode proteins related in function to the products of the FLNB and ALDH18A1 genes.
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Chen, Qian. "Evolution, interaction, and intrinsic properties of dislocations in intermetallics anisotropic 3D dislocation dynamics approach /." [Ames, Iowa : Iowa State University], 2008.
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Ruggles, Tim. "Characterization of Geometrically Necessary Dislocation Content with EBSD-Based Continuum Dislocation Microscopy." BYU ScholarsArchive, 2015. https://scholarsarchive.byu.edu/etd/4392.
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Modeling of plasticity is often hampered by the difficulty in accurately characterizing dislocationdensity on the microscale for real samples. It is particularly difficult to resolve measureddislocation content onto individual dislocation systems at the length scales most commonly of interestin plasticity studies. Traditionally, dislocation content is analyzed at the continuum levelusing the Nye tensor and the fundamental relation of continuum dislocation theory to interpret informationmeasured by diffraction techniques, typically EBSD or High Resolution EBSD. In thiswork the established Nye-Kroner method for resolving measured geometrically necessary dislocationcontent onto individual slip systems is assessed and extended. Two new methods are alsopresented to relieve the ambiguity of the Nye-Kroner method. One of these methods uses modifiedclassical dislocation equations to bypass the Nye-Kroner relation, and the other estimates the bulkdislocation density via the entry-wise one-norm of the Nye tensor. These methods are validatedvia a novel simulation of distortion fields around continuum fields of dislocation density based onclassical lattice mechanics and then applied to actual HR-EBSD scans of a micro-indented singlecrystals of nickel and tantalum. Finally, a detailed analysis of the effect of the spacing betweenpoints in an EBSD scan (which is related to the step size of the numerical derivatives used in EBSDdislocation microscopy) on geometrically necessary dislocation measurements is conducted.
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Tucker, Judith Ann. "Painting landscape : mediating dislocation." Thesis, University of Leeds, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.425628.
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Akarapu, Sreekanth. "Dislocation interactions with interfaces." Pullman, Wash. : Washington State University, 2009. http://www.dissertations.wsu.edu/Dissertations/Summer2009/S_Akarapu_080509.pdf.
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Thesis (Ph. D.)--Washington State University, August 2009.Title from PDF title page (viewed on Sept. 9, 2009). "School of Mechanical and Materials Engineering." Includes bibliographical references (p. 180-188).
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Landeiro, dos Reis Marie. "Étude de l'interaction dislocation - amas de lacunes par simulations numériques." Thesis, Université Paris-Saclay (ComUE), 2019. http://www.theses.fr/2019SACLS311/document.
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Des amas de lacunes ont été observés et caractérisés expérimentalement dans les métaux de haute pureté après déformation plastique ou après une suite de traitements thermiques particuliers. Ces amas sont des obstacles à la propagation des dislocations et peuvent par conséquent induire un durcissement du métal.Cette étude par simulations numériques a permis d'explorer différents mécanismes de propagation de dislocations dans une concentration d'amas en fonction de la contrainte de cisaillement appliquée et de la température. À haute contrainte, la force appliquée sur la dislocation devient supérieure aux forces d'ancrage s’exerçant sur la ligne. La dislocation franchit la distribution d'amas en glissant et en cisaillant les amas. La dépendance de la force d'ancrage en fonction de la taille de l'amas est ajustée sur nos simulations de statique moléculaire. Dans ce domaine de contrainte, les configurations d'amas ancrant la dislocation sont rares et l'activation thermique suffit à désancrer la ligne. La probabilité de désancrer la ligne dépend de l'enthalpie d'activation, un paramètre que nous avons également estimé à l'aide d'un modèle analytique ajusté sur nos résultats atomistiques. À plus faible contrainte, lorsque la force appliquée est inférieure aux forces d'ancrage induites par les amas, la probabilité que la dislocation se désancre uniquement par glissement devient faible. La diffusion des lacunes, émises préférentiellement des amas, intervient alors et favorise la formation de crans. Cela contribue au désancrage de la ligne. Ce mécanisme est le glissement assisté par la montée. Les barrières d'émission, d'absorption et de migration de lacunes ont été déterminées par statique moléculaire et sont fortement dépendantes du champ élastique et de la distorsion du réseau atomique générés par la présence de la dislocation. Cela induit une forte anisotropie de diffusion au voisinage des dislocations qui conduit notamment au mécanisme de 'pipe diffusion'. L'évolution au cours du temps de l'ensemble de ces mécanismes a été étudiée à l'aide d'un modèle de ligne élastique couplé à un algorithme de Monte Carlo cinétique dont l'ensemble des barrières d'énergie provient de nos simulations atomistiques. Moyennant les hypothèses du modèle, nous avons alors obtenu une estimation de la vitesse des dislocations en fonction de la contrainte et de la température appliquée. Nous avons ensuite utilisé la loi d'Orowan pour estimer la vitesse de déformation liée à ces mécanismesVacancy clusters have been observed and characterized experimentally in highly pure metals after plastic deformation or after a particular sequence of heat treatments. These clusters hinder the dislocation propagation and can therefore harden the metal.Using numerical simulations we have explored different mecanisms of dislocation propagation through a vacancy-cluster distribution, for several applied shear stress and temperature. At high stresses, the force applied on the dislocation becomes greater than the pinning forces acting on the line. The dislocation gets through the cluster distribution by gliding and shearing the clusters. The dependence of the pinning force with the cluster size is adjusted on our molecular static simulations. In this stress range, the pinning configurations are rare and the thermal activation is sufficient to unpin the line. The probability for the line to pass the pinning configuration depends on the activation enthalpy, a parameter that we have also estimated using an analytical model adjusted on our atomistic results. At lower stresses, when the applied force is below the pinning forces induced by the cluster, the probability that the dislocation unpins by pure glide becomes negligeable. The diffusion of vacancies, emitted preferentially from the vacancy clusters, intervenes and promotes the formation of jogs that contributes to the unpinning of the line. Such a mecanism is the glide assisted by climb. The emission, the absorption and the vacancy migration barriers have been determined by molecular static and are highly dependent on the elastic field and the atomic network distortion induced by the dislocation. This promotes a strong diffusion anisotropy in the vicinity of the dislocations which leads in particular to the pipe diffusion mechanism. The evolution with time of all these mechanisms has been studied using an elastic line model coupled to a kinetic Monte Carlo algorithm in which the parameters come from our atomistic simulations. According to the model assumptions, we obtained an estimation of dislocation velocity as a function of the applied shear stress and the temperature. We used the Orowan's law to estimate the strain rate related to such mechanisms
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Liu, Bing [Verfasser]. "Discrete dislocation dynamics simulations of dislocation : low angle grain boundary interactions / Bing Liu." Aachen : Hochschulbibliothek der Rheinisch-Westfälischen Technischen Hochschule Aachen, 2012. http://d-nb.info/1027743900/34.
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Sandfeld, Stefan. "Evolution of dislocation density in a higher-order continuum theory of dislocation plasticity." Thesis, University of Edinburgh, 2010. http://hdl.handle.net/1842/11367.
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Shi, Xiangjun. "Etude par simulations de dynamique des dislocations des effets d'irradiation sur la ferrite à haute température." Thesis, Paris 6, 2014. http://www.theses.fr/2014PA066500/document.
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Cette étude s’insère dans le cadre d’une modélisation multi-échelles du durcissement et de la fragilisation par irradiation de l’acier de cuve des Réacteurs nucléaires à Eau Pressurisée (REP). Des simulations en Dynamique des Dislocations (DD) ont été menées pour décrire la plasticité du fer pur irradié à l’échelle du grain et fournir aux échelles supérieures des informations quantitatives telles que la force d’épinglage des dislocations par les boucles induites par l’irradiation. Nous avons débuté notre étude par l’analyse des interactions élémentaires entre une dislocation coin et différents types de boucles. Un nouveau modèle de DD a été identifié puis validé, que ce soit d’un point de vue qualitatif (mécanismes d’interaction) ou quantitatif (contrainte critique), en comparant ces résultats à ceux obtenus en Dynamique Moléculaire dans la littérature. L’influence de la taille des boucles et de la vitesse de déformation a été particulièrement étudiée.Des simulations élémentaires impliquant cette fois-ci une dislocation vis et les mêmes défauts d’irradiation ont permis d’étendre le domaine de validité du modèle de DD, en se comparant toujours aux résultats de DM de la littérature. Enfin, un premier jeu de simulations massives entre une dislocation coin et différents types de boucles a permis d’obtenir une première estimation de la valeur de la force d’obstacle pour ce type de défauts, α≈0,26. Cette valeur est en accord avec différents travaux précédents, expérimentaux ou numériques, et permet d’envisager avec confiance de futurs travaux s’appuyant sur ce nouveau modèle de DDThis study is a contribution to the multi-scale modeling of hardening and embrittlement of the vessel steel in Pressurized Water Reactors (PWR) under irradiation conditions. Dislocation Dynamics simulations (DD) were conducted to describe the plasticity of irradiated iron at grain scale. Quantitative information about the pinning strength of radiation-induced loops was extracted and can be transferred at crystal plasticity scale. Elementary interactions between an edge dislocation and different types of loops were first analyzed. A new model of DD was identified and validated, both qualitatively in terms of interaction mechanisms and quantitatively in terms of critical stress, using Molecular Dynamics results available in the literature. The influence of the size of the loops and of the strain rate was particularly studied. Elementary simulations involving a screw dislocation and the same radiation-induced defects were conducted and carefully compared to available MD results, extending the range of validity of our model. Finally, a set of massive simulations involving an edge dislocation and a large number of loops was performed and allowed a first estimation of the obstacle strength for this type of defects (α≈0.26). This value is in a good agreement with previous experimental and numerical studies, and gives us confidence in future work based on this new DD model
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Li, Yang. "Fragilisation des aciers de cuve irradiés : analyse numérique des mécanismes de plasticité à l’aide de simulations de dynamique des dislocations." Thesis, Université Paris-Saclay (ComUE), 2019. http://www.theses.fr/2019SACLN031/document.
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Ce travail est une contribution à l’étude de la dégradation des propriétés mécaniques des matériaux métalliques irradiés, dans le contexte de la production d’énergie nucléaire. Cette thèse porte en particulier sur l’étude du comportement des dislocations dans les matériaux ferritiques irradiés, à l’aide de simulations de dynamique des dislocations (DD).L’évolution de la microstructure des défauts d’irradiation est tout d’abord analysée à l'aide d’un code nodal (code NUMODIS). Le Chapitre 2 traite en particulier de la diffusion et l’interaction de boucles prismatiques, en utilisant la dynamique des dislocations dite «stochastique». Ces calculs reproduisent les forces d’interaction élastiques boucle/boucle et les forces stochastiques associées aux fluctuations thermiques ambiantes. Il est ainsi montré que la réorientation des boucles (tilt) a un fort effet sur leur dynamique, en ce qui concerne notamment le taux d’évolution du confinement élastique boucle/boucle.L'effet du glissement dévié sur l’interaction entre dislocation/boucle est ensuite examiné au Chapitre 3. Cette étude fait appel à une configuration initiale spécifique, associée à un changement du plan de glissement d'une source de dislocation vis. De cette manière, il est montré que le glissement dévié réduit considérablement la résistance des défauts/obstacles. Cet effet confirme le rôle critique du glissement dévié durant la déformation plastique post-irradiation.La déformation plastique post-irradiation est étudiée à l’échelle du grain, au Chapitre 4, à l’aide de simulations DD à base de segments (code TRIDIS). Ces simulations traitent les mécanismes de glissement dévié et de glissement thermiquement activé (vis). Chaque condition d’irradiation simulée peut être caractérisée par un «décalage de la température apparente induite par des défauts d’irradiation» (ΔDIAT). Cette quantité est proportionnelle aux évolutions statistiques de la mobilité effective des dislocations. Le ΔDIAT calculé est pratiquement équivalent au décalage de la température de transition fragile à ductile (ΔDBTT) obtenu expérimentalement, pour une taille et densité de défauts d’irradiation donnée. Cette corrélation ΔDIAT/ΔDBTT peut être interprétée à partir de mécanismes de déformation plastique élémentaires, faisant appel à la théorie des dislocationsThe interplay between radiation-generated defects and dislocation networks leads to a variety of changes in mechanical properties and results in a detrimental effect on the structural reactor component lifetime. The present PhD work focuses on studying elementary and collective dislocation mechanisms in irradiated iron-based materials, by means of dislocation dynamics (DD) simulations.Evolutions of the radiation-induced defect microstructure are studied first. Namely, the 1D diffusion of interacting prismatic loops is analyzed using the stochastic dislocation dynamics approach, accounting for the elastic forces acting between the loops and the stochastic forces associated with ambient thermal fluctuations. It is found that the interplay between stochastic forces and internal degrees of freedom of loops, in particular the loop reorientation, strongly influences the observed loop dynamics, especially the reaction rates resulting in the elastic confinement of loops.The cross-slip effect on the dislocation/loop interactions is then examined using a specific initial configuration associated with the glide plane change of a screw dislocation source, due to a single and well defined cross-slip event. It is shown that cross-slip significantly affects the effective strength of dislocation/defect interactions and therefore, post-irradiation plastic strain spreading.Lastly, post-irradiation plastic strain spreading is investigated at the grain scale using segment-based dislocation dynamics simulations, accounting for the thermally activated (screw) dislocation slip and cross-slip mechanisms. It is shown that each simulated irradiation condition can be characterized by a specific “Defect-Induced Apparent Straining Temperature shift” (ΔDIAT) level, reflecting the statistical evolutions of the effective dislocation mobility. It is found that the calculated ΔDIAT level closely matches the ductile to brittle transition temperature shift (ΔDBTT) associated with the corresponding, experimentally-observed defect size and number density. This ΔDIAT/ΔDBTT correlation can be explained based on plastic strain spreading arguments
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Titchener, J. B. "Continuum models for dislocation distributions." Thesis, University of Oxford, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.382704.
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Shah, Manan H. (Manan Harish) 1977. "Arrival / departure : architecture of dislocation." Thesis, Massachusetts Institute of Technology, 2002. http://hdl.handle.net/1721.1/70351.
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Thesis (M. Arch.)--Massachusetts Institute of Technology, Dept. of Architecture, 2002.Includes bibliographical references (p. 76-77).
Our identities are defined by a qualitative set of parameters that are at once universal and site specific. We are, as an old saying puts it, "products of our environment." Our knowledge and our beings are constantly being tested and changed through our interactions, both physical and cerebral, in our environments. Historically this sphere of influence was rather narrow, but as technology and travel have increased, environments have become fragmented; they no longer have clear edges, are discontinuous, and above all, are always changing. I am at once a product of where I live, where my parents lived, where I study, what I have read about, where I have traveled, and where I dream to be. I consequently have many homes, many anchors, and many points of reference. The following architectural thesis investigations study architectural responses to the complexity of the conditions created in individuals and communities through the modern migratory process. Using the theme of ambivalence (the coexistence of opposing attitudes or feelings), this thesis addresses many independent and overlapping issues of identity and migration from both the scale of object and architecture. The thesis posits the question: is an architectural infrastructure possible that can allow for communication between migrants and local communities and between migrants themselves that can span time, language, and space? And can such infrastructure protect ethnicity while still allowing to be shared?
by Manan H. Shah.
M.Arch.
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Gannon, Suzanne. "Divine dislocation and analysing Sita." Thesis, Lancaster University, 2014. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.732706.
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The creative text and its accompanying critical thesis explore how - through the writing of memoirs - ex-members of total institutions justified their acceptance of institutional controls. The critical thesis uses narratives within the sub-genre of apostate memoirs to support a sociological understanding of social dynamics within religious and political total institutions. It draws on theories concerning women’s experiences in new religious movements (NRMs), as well as studies of disaffiliation from NRMS. The creative text is a personal memoir, exploring the author’s experience of living within the Hare Krishna movement. The creative component of this thesis and the exegetical component are a bi-partite entity. Sociological and stylistic theories are informed by the nexus of the memoir writing and analysis of existing memoirs; the creative component is informed by the sociological theories of religion explored in the critical component. Both components address the same research question: Why do members of total institutions accept the controls placed on them? As a subset, additional questions are addressed. These include how a memoirist reveals the stage of disaffiliation they were in at the time of writing the memoir, and whether they can be positioned as apostate or defector. There is a focus on how dyadic relationships are controlled by institutional practices. A feminist perspective is used to understand the ways women in total institutions adopt cognitive justification strategies as coping mechanisms within these patriarchal environments.
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Goetz, Benoît. "La dislocation - architecture et experience." Université Marc Bloch (Strasbourg) (1971-2008), 1996. http://www.theses.fr/1996STR20017.
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Cette these est une tentative pour faire de la philosophie a partir de l'architecture. Il s'agit, d'abord, d'envisager l'architecture comme pensee de l'espace et de tirer les consequences ethiques et politiques d'une telle definition. On montre de la sorte que l'architecture ne se limite pas a ce melange de technique et d'art (ou quelquefois un sens parvient a poindre) en quoi la tradition esthetique la maintenait enfermee depuis le xviiieme siecle. L'architecture construit des moments de monde. Dans la mesure ou l'existence est spatiale, l'architecture doit etre envisagee comme une condition d'existence. Ce "mode d'action de l'architecture" passe generalement inapercu. La singularite architecturale, que perdent de vue les "plasticiens" et les " esthetes", c'est d'etre une "construction ethique", c'est-a-dire une "installation" dont le mode d'action concerne directement l'existence humaine. L'architecture est un constructivisme existentiel. Il s'agit d'autre part d'entreprendre une critique du concept de lieu, en denoncant le caractere vain des discours nostalgiques qui tentent de le reactiver. La dislocation, c'est-a-dire la ruine du principe de localisation, ne doit pas etre pensee comme un evenement destructeur. Habiter, en effet, n'a jamais lieu de maniere simple et univoque. . L'architecture nous apprend a distinguer des espaces sans commune mesure dont aucun ne peut pretendre au monopole de la verite ou de l'authenticite. Il faut toujours aujourd'hui se demander ce qu'habiter veut dire.
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Farber, Boris Yarovlevick. "Dislocation velocities and dislocation structure in cubic zirconia and sapphire (alpha-aluminum oxide) single crystals." Case Western Reserve University School of Graduate Studies / OhioLINK, 1994. http://rave.ohiolink.edu/etdc/view?acc_num=case1061555653.
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Sandfeld, Stefan [Verfasser]. "The Evolution of Dislocation Density in a Higher-order Continuum Theory of Dislocation Plasticity / Stefan Sandfeld." Aachen : Shaker, 2011. http://d-nb.info/1084535742/34.
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Gaume, Marine. "Etude des mécanismes de déformation des alliages de zirconium après et sous irradiation." Thesis, Toulouse 3, 2017. http://www.theses.fr/2017TOU30220/document.
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Au sein des Réacteurs à Eau Pressurisée, le flux de neutrons entraîne une modification des propriétés mécaniques des gaines à combustible en alliage de zirconium. Bien que leur comportement macroscopique soit bien connu, les mécanismes microscopiques de la déformation des alliages de zirconium restent à caractériser. Afin de simuler l'irradiation aux neutrons, des irradiations aux particules chargées (ions et électrons) ont été réalisées à 400 et 450°C sur un alliage de zirconium: le Zircaloy-4 RXA. L'analyse expérimentale de la microstructure obtenue après irradiation, effectuée au Microscope Electronique en Transmission (MET), a montré la présence de défauts cristallins: les boucles de dislocation de vecteur de Burgers . Leur évolution au cours de l'irradiation (taille et densité), ainsi que leurs caractéristiques (nature et plan d'habitat) ont été déterminées et discutées sur la base de la diffusion des défauts ponctuels. Les résultats obtenus suggèrent une diffusion des auto-interstitiels très faiblement anisotrope. Des expériences de traction in-situ ont été réalisées au MET, après irradiation aux ions, afin d'activer le glissement des dislocations et d'observer leurs interactions avec ces boucles . Certains cas d'interactions observés expérimentalement ont été modélisés par Dynamique des Dislocations pour une meilleure compréhension des mécanismes. L'effet simultané de la contrainte et de l'irradiation sur les mécanismes de déformation a ensuite été étudié. Des irradiations in-situ aux électrons et aux ions ont été effectuées, sans et avec application d'une contrainte. Des mécanismes de déformation impliquant la montée des dislocations ont ainsi été mis en évidence. Grâce à l'ensemble de cette étude, des modèles basés sur les mécanismes identifiés pourront être, à terme, proposés afin de prédire le comportement des alliages de zirconium en réacteurIn Pressurized Water Reactors, the neutron flux leads to a change in the mechanical properties of the fuel cladding tubes made of zirconium alloys. Although their macroscopic behavior is well known, the microscopic deformation mechanisms of zirconium alloys still need to be characterized. In order to simulate the neutron irradiation, charged particles irradiations (ion and electron) were carried out at 400°C and 450°C on a zirconium alloy: RXA Zircaloy-4. The experimental analysis of the irradiated microstructure, performed by using a Transmission Electron Microscope (TEM), have shown some crystalline defects: dislocation loops with a Burgers vector. Their evolution (size and density) and their characteristics (nature and habit plane) have been determined and discussed based on the point defects diffusion. The results suggest a weak anisotropy in the self-interstitial diffusion. In-situ tensile tests were performed using a TEM, after ion irradiation, in order to activate the dislocation glide and to observe their interaction with the loops. Some of the experimental cases of interaction have been simulate using Dislocation Dynamics for a better understanding of the mechanisms. The simultaneous effect of the stress and of the irradiation on the deformation mechanisms have been then studied. In-situ electron and ion irradiations were conducted, with and without an applied stress. Deformation mechanisms involving dislocation climb have thus been demonstrated. Through this study, models based on the identified mechanisms may be suggested, in order to predict the behavior of zirconium alloys in the reactor
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Archer, J. A. "Dislocation enhanced diffusion in sodium chloride." Thesis, University of Kent, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.380594.
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Salim, Tamari. "The dislocation and reconstitution of Peasantry." Thesis, University of Manchester, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.510045.
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The war of 1948 has had a major dislocating impact on the various institutions of Palestinian society. This study attempts to examine the consequences of this dislocation on the agrarian regime in two ecological zones of central Palestine: the dry farming regions in the highlands of the West Bank, and the intensive farming areas of the Western Valley of the Jordan. Explanations are provided for the persistence and even prosperity of peasant communities which have undergone a process of protracted 'de-peasantisation' in areas of marginal and marginalized dry farming. Variables of landlessness, wage labour, tenancy forms, and population movements are utilized to interpret current trends in Palestinian rural society in the light of four village case studies. Particular attention is directed towards the consolidation of a stratum of peasant-workers and their future in the context of Israeli annexation of Arab land, and integration of the Palestinian labour force into the Israeli economy. At a different level of analysis,. the study examines the manner in which the dispossessed peasants of coastal Palestine re-constituted themselves in a new rural economy under conditions of intensified agriculture and capitalization of farm inputs in a process identified here as 're-peasantisation'. In this context, the thesis discusses the decline of patrimonial relations and the subjugation of peasants to relations of dependency under the new agricultural technology. Finally, changes in the social economy of Palestinian villages are compared to features of rural transformation in Europe and the third world today
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Yap, Kheng Kin. "PROJECT: SPANNING THE SPACE OF DISLOCATION." Thesis, The University of Sydney, 2005. http://hdl.handle.net/2123/1336.
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Studio work The Postgraduate Degree Show is held from 6PthP December 2005 to 17PthP December 2005 and my work is installed in the Sculpture Studio (as a gallery space) at Building 29 of Sydney College of the Arts, Sydney. There are three installations of work, each with a series of paintings and object-models. The media I am using are oil on canvas for the paintings and wood for the models. The titles of my exhibition pieces are Project Studio (Stairs), Project Rented Room (Chair), Project Rented Room (Bed), and Project Object. Together they are entitled Project: Spanning the Space of Dislocation. The project explores the perception of space and its representation through painting and installation. The starting point is the image of familiar architectural objects to which I displace the experience of it from one site (my painting studio) to another (the gallery space) through painting as index. I use the technique of ambiguous linear forms in painting and the reflexive reading of orthogonal projective planes in installation to further extend the viewer’s perception of space and objects. The aim is to show that space has a meaningful relationship to objects and bring about a renewed awareness of habitual practice in seeing and representing space. UResearch paperU I have divided my research paper in two chapters. Chapter one explores the issue of spatial representation through ambiguity of simple linear forms and painting as index. My concern is on space being less important to objects in the distinction between space as ground and object as figure. Within this chapter I argue for an extended and a reflexive mode of seeing and representing space and objects instead of for a ground-figure contrast. By mapping my experience on a usual working site and displacing it to another space, I show that my perception of space is extended such that the boundary between the familiar and foreign (that is, space-object distinction) is blurred. Chapter two explores the method of presentation through painting and installation in a gallery and addresses the viewer’s space of perception with the work. I also discuss possible reflexive readings on the projective planes of the work which further extend the perception of it.
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Yap, Kheng Kin. "PROJECT: SPANNING THE SPACE OF DISLOCATION." University of Sydney, 2005. http://hdl.handle.net/2123/1336.
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Master of Visual ArtsStudio work The Postgraduate Degree Show is held from 6PthP December 2005 to 17PthP December 2005 and my work is installed in the Sculpture Studio (as a gallery space) at Building 29 of Sydney College of the Arts, Sydney. There are three installations of work, each with a series of paintings and object-models. The media I am using are oil on canvas for the paintings and wood for the models. The titles of my exhibition pieces are Project Studio (Stairs), Project Rented Room (Chair), Project Rented Room (Bed), and Project Object. Together they are entitled Project: Spanning the Space of Dislocation. The project explores the perception of space and its representation through painting and installation. The starting point is the image of familiar architectural objects to which I displace the experience of it from one site (my painting studio) to another (the gallery space) through painting as index. I use the technique of ambiguous linear forms in painting and the reflexive reading of orthogonal projective planes in installation to further extend the viewer’s perception of space and objects. The aim is to show that space has a meaningful relationship to objects and bring about a renewed awareness of habitual practice in seeing and representing space. UResearch paperU I have divided my research paper in two chapters. Chapter one explores the issue of spatial representation through ambiguity of simple linear forms and painting as index. My concern is on space being less important to objects in the distinction between space as ground and object as figure. Within this chapter I argue for an extended and a reflexive mode of seeing and representing space and objects instead of for a ground-figure contrast. By mapping my experience on a usual working site and displacing it to another space, I show that my perception of space is extended such that the boundary between the familiar and foreign (that is, space-object distinction) is blurred. Chapter two explores the method of presentation through painting and installation in a gallery and addresses the viewer’s space of perception with the work. I also discuss possible reflexive readings on the projective planes of the work which further extend the perception of it.
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Shi, Xiangjun. "Etude par simulations de dynamique des dislocations des effets d'irradiation sur la ferrite à haute température." Electronic Thesis or Diss., Paris 6, 2014. https://accesdistant.sorbonne-universite.fr/login?url=https://theses-intra.sorbonne-universite.fr/2014PA066500.pdf.
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Cette étude s’insère dans le cadre d’une modélisation multi-échelles du durcissement et de la fragilisation par irradiation de l’acier de cuve des Réacteurs nucléaires à Eau Pressurisée (REP). Des simulations en Dynamique des Dislocations (DD) ont été menées pour décrire la plasticité du fer pur irradié à l’échelle du grain et fournir aux échelles supérieures des informations quantitatives telles que la force d’épinglage des dislocations par les boucles induites par l’irradiation. Nous avons débuté notre étude par l’analyse des interactions élémentaires entre une dislocation coin et différents types de boucles. Un nouveau modèle de DD a été identifié puis validé, que ce soit d’un point de vue qualitatif (mécanismes d’interaction) ou quantitatif (contrainte critique), en comparant ces résultats à ceux obtenus en Dynamique Moléculaire dans la littérature. L’influence de la taille des boucles et de la vitesse de déformation a été particulièrement étudiée.Des simulations élémentaires impliquant cette fois-ci une dislocation vis et les mêmes défauts d’irradiation ont permis d’étendre le domaine de validité du modèle de DD, en se comparant toujours aux résultats de DM de la littérature. Enfin, un premier jeu de simulations massives entre une dislocation coin et différents types de boucles a permis d’obtenir une première estimation de la valeur de la force d’obstacle pour ce type de défauts, α≈0,26. Cette valeur est en accord avec différents travaux précédents, expérimentaux ou numériques, et permet d’envisager avec confiance de futurs travaux s’appuyant sur ce nouveau modèle de DDThis study is a contribution to the multi-scale modeling of hardening and embrittlement of the vessel steel in Pressurized Water Reactors (PWR) under irradiation conditions. Dislocation Dynamics simulations (DD) were conducted to describe the plasticity of irradiated iron at grain scale. Quantitative information about the pinning strength of radiation-induced loops was extracted and can be transferred at crystal plasticity scale. Elementary interactions between an edge dislocation and different types of loops were first analyzed. A new model of DD was identified and validated, both qualitatively in terms of interaction mechanisms and quantitatively in terms of critical stress, using Molecular Dynamics results available in the literature. The influence of the size of the loops and of the strain rate was particularly studied. Elementary simulations involving a screw dislocation and the same radiation-induced defects were conducted and carefully compared to available MD results, extending the range of validity of our model. Finally, a set of massive simulations involving an edge dislocation and a large number of loops was performed and allowed a first estimation of the obstacle strength for this type of defects (α≈0.26). This value is in a good agreement with previous experimental and numerical studies, and gives us confidence in future work based on this new DD model
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Oliveira, Maria Angela Loyola de. "Émission et développement de dislocations en tête de fissure dans le silicium : analyse tridimensionnelle de l'interaction dislocation/fissure." Vandoeuvre-les-Nancy, INPL, 1994. http://www.theses.fr/1994INPL067N.
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Des éprouvettes monocristallines, sans dislocations, fissurées a 20c par clivage limite, sont chargées progressivement a une température suffisante (700c environ) pour que le silicium devienne ductile du fait de l'activation thermique du glissement des dislocations. Les concentrations de contraintes existant en pointe de fissure provoquent la nucléation et le développement de boucles de dislocations qui exercent en retour sur la fissure des contraintes s'opposant en moyenne a sa propagation: cet effet est appelé écrantage. La partie expérimentale de cette étude est consacrée à la localisation des sources de dislocations, à la caractérisation des systèmes de glissement actives et à l'influence du chargement sur la ténacité du matériau. Le chargement en deux étapes qui a été développe permet d'activer un nombre limite de sources, puis de suffisamment étaler les configurations de dislocations pour qu'elles puissent être caractérisées par topographie aux rayons X, tout en évitant l'émission de nouvelles dislocations. L'objectif de la partie théorique de cette étude est de poser les concepts fondamentaux de l'interaction dislocation-fissure puis de l'évaluer quantitativement. Le calcul de l'écrantage et de l'ouverture de la fissure a pu être effectué analytiquement, grâce à la simplicité du formalisme lié aux états plans. Dans le cas réel, tridimensionnel, le calcul de l'écrantage a été réalisé par intégration numérique du champ de contrainte d'une boucle circulaire pondère par une fonction de poids, en utilisant le théorème de superposition
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Li, Qizhen. "Theory and modeling of the mechanical behavior of nanoscale and finescale multilayer thin films." Connect to this title online, 2004. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1095684024.
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Thesis (Ph. D.)--Ohio State University, 2004.Title from first page of PDF file. Document formatted into pages; contains xviii, 190 p.; also includes graphics. Includes bibliographical references (p. 181-190).
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Yellakara, Ranga Nikhil. "Computational Study of Dislocation Based Mechanisms in FCC Materials." Thesis, University of North Texas, 2014. https://digital.library.unt.edu/ark:/67531/metadc699921/.
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Understanding the relationships between microstructures and properties of materials is a key to developing new materials with more suitable qualities or employing the appropriate materials in special uses. In the present world of material research, the main focus is on microstructural control to cost-effectively enhance properties and meet performance specifications. This present work is directed towards improving the fundamental understanding of the microscale deformation mechanisms and mechanical behavior of metallic alloys, particularly focusing on face centered cubic (FCC) structured metals through a unique computational methodology called three-dimensional dislocation dynamics (3D-DD). In these simulations, the equations of motion for dislocations are mathematically solved to determine the evolution and interaction of dislocations. Microstructure details and stress-strain curves are a direct observation in the simulation and can be used to validate experimental results. The effect of initial dislocation microstructure on the yield strength has been studied. It has been shown that dislocation density based crystal plasticity formulations only work when dislocation densities/numbers are sufficiently large so that a statistically accurate description of the microstructure can be obtainable. The evolution of the flow stress for grain sizes ranging from 0.5 to 10 µm under uniaxial tension was simulated using an improvised model by integrating dislocation pile-up mechanism at grain boundaries has been performed. This study showed that for a same initial dislocation density, the Hall–Petch relationship holds well at small grain sizes (0.5–2 µm), beyond which the yield strength remains constant as the grain size increases.
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Ni, Luqun. "The effective mass of an accelerating dislocation." Diss., Connected to a 24 p. preview or request complete full text in PDF format. Access restricted to UC campuses, 2005. http://wwwlib.umi.com/cr/ucsd/fullcit?p3190138.
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Thesis (Ph. D.)--University of California, San Diego, 2005.Title from first page of PDF file (viewed March 8, 2006). Available via ProQuest Digital Dissertations. Vita. Includes bibliographical references (p. 171-174).
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Schwarz, Cornelia. "Numerical implementation of continuum dislocation-based plasticity." kostenfrei, 2007. http://mediatum2.ub.tum.de/doc/618976/document.pdf.
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George, Amber Elizabeth. "Interpreting dislocation gathering a sense of belonging /." Diss., Online access via UMI:, 2007.
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Chang, Zhongwen. "Modelling of Dislocation Bias in FCC Materials." Licentiate thesis, KTH, Reaktorfysik, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-122407.
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Irradiation induced void swelling is problematic for the application of austenitic steels under high dose irradiation. In this thesis, the swelling is characterized by dislocation bias. The dislocation bias is obtained using the finite element method, accounting for fcc copper and nickel under electron irradiation. The methodology is implemented with the interaction energies between an edge dislocation and point defects. Analytically derived interaction energies, which are based on elasticity theory, are compared with interaction energies obtained from atomistic model using semi-empirical atomic potentials as physics basis. The comparison shows that the description of analytical interaction energies is inaccurate in the dislocation core regions. The bias factor dependence on dislocation density and temperature is presented and discussed. At high temperatures or low dislocation densities, the two approaches tend to converge. However, the dislocation bias based on the interaction energies from the two approaches, reveals larger discrepancy for nickel than for copper. The impact on dislocation bias from the different stacking fault energies of copper and nickel is elaborated. Nickel, which has a larger stacking fault energy, is predicted to have larger swelling rate than copper under the same irradiation conditions.QC 20130530
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Butler, George C. "Incorporating dislocation substructure into crystal plasticity theory." Diss., Georgia Institute of Technology, 1999. http://hdl.handle.net/1853/34072.
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Polycrystal models, beginning with the work of Sachs (1928) and Taylor (1938), have been used to predict very complex material behavior. The basis of these models is single crystal plasticity theory, which is then extended to model an actual (polycrystalline) material composed of a large number of single crystals or grains. Crystal plasticity models are formulated at the scale of the individual grain, which is viewed as a fundamental material element. To first order this is a reasonable approximation, and results in qualitatively good predictions. However, it is also well known that the grain is not a uniform entity, and that a great deal of non-uniform activity, including the development of well-defined dislocation structures, occurs within individual grains. The goals of this research are to complete an experimental data set for validation of material modeling, and to then improve the physical basis of predictive polycrystal plasticity models. Preferred orientations (textures) of oxygen free high conductivity (OFHC) copper were measured using reflection x-ray diffraction techniques. Monotonic strain paths included a variety of strain levels for both compression and torsion. One of the significant contributions of this research was the measurement of textures resulting from non-monotonic deformation histories, specifically compressive prestrain (to two different levels) followed by torsion to an effective plastic strain of 1.00. We also concluded synchrotron radiation experiments to map Laue images to examine subgrain microtexture formation at various stages of finite deformation. The second major contribution is to polycrystal plasticity modeling. Improvements to the plasticity model were achieved by including the effects of gradually developing, sub-grain scale microstructures, without explicitly modeling the structures, in terms of both crystallographic texture formation and work hardening. The effects of these microstructures were incorporated through the use of new internal state variables. They result in a broadening of the peaks of the macroscopic texture and a reduction of the rate of texture formation. Predictions of crystallographic orientation distributions were verified by plotting stereographs, which were shown to match measured crystallographic textures. The microstructural hardening law was introduced through a new form of latent hardening, which was shown to match experimental stress-strain behavior more closely than the basic model of Pierce, Asaro, and Needleman (1982). This latent hardening form augmented a Taylor-type term, which reflected statistically stored dislocations in the slip system hardness. Significantly, this improvement was also noted in the case of non-monotonic loading, which the standard model could not predict even to first order. Also, in the course of this research a planar double slip model was used as a precursor to the full three-dimensional modeling. The objective was to use the planar model to test various formulations, at least qualitatively, since it is a simpler model. As a result of comparisons between the three-dimensional simulations and the planar ones, the planar model was shown to be an insufficient tool for developing new texture and hardening evolution schemes as compared to the three-dimensional models. The planar model was unsuitable for modeling any but the most basic crystal plasticity relations and most simple deformation paths in a qualitative manner.
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Robinson, Brett John. "Dislocation in mobile-bearing lateral unicompartmental arthroplasty." Thesis, University of Oxford, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.269475.
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Mason, Jeremy K. (Jeremy Kyle). "Statistical physics of dislocation nucleation by nanoindentation." Thesis, Massachusetts Institute of Technology, 2005. http://hdl.handle.net/1721.1/32914.
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Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Physics, 2005.Page 82 blank.
Includes bibliographical references (page 79-81).
Current understanding of the onset of plasticity during nanoindentation of crystalline materials involves homogenous dislocation nucleation in the crystal underneath the indenter. Through the use of cutting-edge nanoindentation techniques, this study examines the initiation of plastic deformation in single crystal oriented platinum samples. Variations in the temperature and loading rate during indentation reveal temporal and thermal dependencies, and support the stochastic and thermally-activated nature of the initial plastic event. These dependencies of dislocation nucleation are precisely quantified by developing analysis methods based on statistical thermodynamics, and are used to evaluate the probability of various atomistic mechanisms. The results of this procedure implicate a critical activation event occurring in a single atomic volume, with an activation enthalpy of a fraction of an electron volt. These findings strongly indicate that the initiation of plasticity begins with a heterogeneous dislocation nucleation event, in conflict with the current belief, and significantly advance understanding of the onset of plastic deformation during nanoindentation.
by Jeremy K. Mason.
S.B.
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Cai, Wei 1977. "Atomistic and mesoscale modeling of dislocation mobility." Thesis, Massachusetts Institute of Technology, 2001. http://hdl.handle.net/1721.1/8682.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Nuclear Engineering, 2001.Vita.
Includes bibliographical references (p. 297-320).
Dislocation is a line defect in crystalline materials, and a microscopic carrier of plastic deformation. Because dislocation has both a localized core and a long-range stress field, linking atomistic and meso scales is often the most challenging step in studying its dynamics. This Thesis presents theories and simulations of dislocations in Si and BCC transition metals, with emphasis on the atomistic-mesoscale coupling. Contributions are made in both methods development and mechanistic understanding of dislocation mobility. For atomistic studies of defects embedded in a mesoscale surrounding, we have given rigorous treatments of two types of boundary effects. A method is derived for quantifying artificial image energies in dislocation simulations with a periodic cell, in which a longstanding conditional convergence problem in lattice summation is resolved. We have also developed a systematic approach based on the linear response theory, which minimizes boundary wave reflections in molecular dynamics simulations without artificial damping. When predictive models are confronted with experiments at the level of mesoscale kinetics, the challenge is to properly incorporate atomistic details into a coarse-grained simulation.
(cont.) We have investigated dislocation core and kink mechanisms and obtained deeper understandings on the shuffle-glide controversy in Si and edge versus screw dislocations in BCC Mo, with some of these breakthroughs related to a better control of artificial boundary effects. The atomistic-mesoscale coupling is then manifested in our formulation of a kinetic Monte Carlo description of dislocation glide in Si at the mesoscale, based on kink mechanisms. As a result, the nature of "weak obstacles" to kink propagation, a long-standing postulate for interpreting low stress dislocation mobility data, is clarified. This model is then generalized to incorporate cross slip for modeling screw dislocation motion in a BCC lattice. Lastly, a physically-motivated procedure is derived for removing the stress singularity in mesoscale dislocation dynamics simulations.
by Wei Cai.
Ph.D.
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Qin, Cai-Dong. "Dislocation structures associated with indentations in ceramics." Thesis, University of Oxford, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.670333.
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Travlos, John. "Neural injury following traumatic anterior shoulder dislocation." Master's thesis, University of Cape Town, 1989. http://hdl.handle.net/11427/26247.
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In this study I reviewed 28 patients with brachial plexus lesions caused by shoulder dislocation. As far as can be established, this is the largest series reviewed in the literature to date. Contrary to most other reports, the neurological lesions involved the supraclavicular as well as the infraclavicular brachial plexus. The only part of the supraclavicular brachial plexus affected was the suprascapular nerve, and this always recovered spontaneously. Isolated axillary nerve lesions were found to have the poorest prognosis for spontaneous nerve recovery. All lesions that showed no recovery after 3 - 5 months were explored and had either a graft or a neurolysis. This study discusses the combinations of nerve lesions, their recovery and the indications for surgical intervention. I also suggest a classification perhaps more clinically relevant than the anatomical classification of Leffert and Seddon (1965).
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Rajagopalan, Srinivasan. "Dislocation structures and deformation mechanisms in NiAl /." The Ohio State University, 1999. http://rave.ohiolink.edu/etdc/view?acc_num=osu1488190109869723.
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BOIOLI, FRANCESCA. "Dislocation modelling in realistic Si-Ge nanostructures." Doctoral thesis, Università degli Studi di Milano-Bicocca, 2013. http://hdl.handle.net/10281/40115.
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SiGe heterostructures have gained a lot of interests in view of developing devices integrated into the main-stream Silicon technology and also from a scientific point of view as a prototypical system to understand the properties of more complex systems, such as III-V semiconductors. Si-Ge epitaxial structures, as well as other mismatched heteroepitaxial materials, have a high potential to improve the state-of-the-art of Si devices, thanks to the fact that the strain modifies the band structures of this material class, opening new possibility of band-gap engineering.
Since the nineties, the development of devices having strained-SiGe layers as the active part occurred, in particular the heterojunction bipolar transistors, further developed to what is presently the fourth-generation of SiGe technology. Also the introduction of strained Si layers by using relaxed SiGe virtual substrates, is very important, for example, for the complementary metal–oxide–semiconductor (CMOS) technology.
In order to effectively exploit SiGe or strained-Si layers in any application, it is fundamental to growth high quality single crystalline materials, reducing as much as possible the defect density in the active volume and the surface corrugation, and to obtain the desired strain state in the epitaxial layers. However the possibility of using such heterostructures for any application, is hindered by the nucleation of dislocation, which is often an unavoidable strain-relief mechanisms. Dislocation formation affects both the final material quality and the relaxation degree of mismatched layers. These defects are often charged and act as non-radiative recombination centers and it is generally accepted that they are detrimental for opto-electronic devices based on Si-Ge semiconductors. In the past years, a lot of effort has been devoted reduce the defect density or to segregate dislocations in non-active regions. However, dislocation engineering, intended as the precise control of dislocation position, has always been a goal out of reach, because of the nucleation of such defects at unpredictable sites at the surface or at other heterogeneities. It is clear that predicting the extent of the plastic relaxation process and governing dislocation nucleation and positioning would be of the utmost importance.
Self-assembled nanoislands and nanowires, represent other novel heterostructures that can be exploited to obtain defect-free configurations with the desired strain state. Even in this case, very high stresses arise from the epitaxial integration of lattice mismatched materials and dislocation formation remains a competitive strain relief mechanism. Hence it is of fundamental importance to determine the coherency limits of such nanostructures and to elucidate the main strain relief mechanisms in the attempt to predict the final dislocation microstructure and strain state in heteroepitaxial systems.
The main goal of this work, is the understanding of the fundamental mechanisms of dislocation nucleation and propagation in Si-Ge nanostructures (i.e. films, nanoislands and nanowires) through dislocation modelling. Even if dislocation formation and motion relies on a sequence of discrete atomic displacements, such defects induce in a crystal a smooth deformation field in the entire structure. The elastic theory of dislocations provides a good description of such stress field and of the elastic energy, as produced by dislocations in bulk materials or in finite size solids with simple geometries. In order to assess the stresses and the energetics of plastically relaxed multifaceted structures, characterized by an high surface to volume ratio and typical length scale in the order of tens or hundreds of nanometers, linear elasticity theory numerically solved by finite element methods is the most suitable tool, since in this approximation the dislocation-surface interaction can be correctly taken into account. Moreover, the motion of dislocations in nanostructures can be handled by using three-dimensional dislocation dynamics simulations. This simulation technique, originally developed to study plasticity in bulk materials, has been demonstrated to give accurate results also for nanometric systems, and is the tool of choice to study the motion and interactions of a large density of dislocation in thin films or three-dimensional nanocrystals. Important properties determined by the atomistic nature of dislocations moving in a discrete lattice, can be included, both in the finite element calculations and in dislocation dynamics simulations, by adopting simple rules that take into account such atomistic features.
The first topic addressed in this work, is the investigation of plastic relaxation in SiGe epitaxial films aimed at governing dislocation nucleation and positioning. In particular, we show with the help of finite element calculations and dislocation dynamics simulations that a turning point to direct dislocation formation and propagation in predefined regions, is the introduction of preferential nucleation sites through substrate nanopatterning. Theoretical predictions indicating effective dislocation trapping along the features of trench- or pit-patterned substrates are discussed and compared with tailored experiments of SiGe deposition on nanopatterned substrate.
The second issue investigated here concerns self-assembled SiGe nanoislands. In these epitaxial nanostructures an intriguing mechanism of dislocation ordering is observed. In this work we reproduced such behavior by using a simple analytical model based on energetics considerations. Furthermore, the plastic relaxation onset for dislocation formation has been determined in epitaxial islands grown on pit-patterned substrates and nucleated in pits. The key factors influencing dislocation formation in such structures have been identified, opening new possibility to grow large defect-free islands on nanopattered substrates.
Finally, dislocation formation in core-shell nanowires has been considered. Elastic and plastic strain relaxaion has been investigated in such structures and a mechanism for dislocation nucleation and propagation in core-shell nanowires is presented. This allowed us to predict dislocation configurations that are more efficient in the strain relief process and the expected misfit dislocation pattern at the core-shell interface.
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Sirindil, Abdullah. "Z-modules et alliages intermétalliques." Thesis, Paris 6, 2017. http://www.theses.fr/2017PA066484/document.
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Le présent travail de thèse se propose de profiter de la description cristallographique à N dimensions pour rediscuter les structures des alliages métalliques périodiques dont les atomes sont situés sur un sous-ensemble ordonné d’un Z-module — c’est-à-dire sur des positions qui sont des combinaisons linéaires entières de N>3 vecteurs arithmétiquement indépendants— exemplifiés par les quasicristaux et les phases approximantes. La description cristallographique à N dimensions permet ainsi de révéler des symétries supplémentaires, cachées dans l’espace physique, susceptibles d’engendrer de nouveaux types de défauts, dits défauts de module, dans les alliages métalliques périodiques dont les atomes se localisent sur un Z-module non trivial dans l’espace direct. Ces défauts correspondent aux opérations de symétrie interne du Z-module qui sont perdues lors de la projection rationnelle dans l’espace physique en raison de la périodicité de l’alliage. Ce sont des macles, des défauts de translations et les dislocations qui les bordent et que nous désignons par dislocations de modules pour les différencier des usuelles dislocations de réseau. Elles apparaissent comme des dislocations partielles bordant une ou plusieurs fautes d’empilement. Des dislocations particulières peuvent exister avec des vecteurs de Burgers ayant une composante nulle dans l’espace physique. Ces dislocations, que nous appelons dislocations scalaires, n’engendrent aucun champ de contrainte et ne sont sensibles à aucun champ de déformation. La phase orthorhombique NiZr de symétrie Cmcm a une maille cristalline dont tous les atomes sont situés sur une fraction d’un même Z-module pentagonal ; elle, est à ce titre, parfaitement descriptible à 5 dimensions. A parti de cette analyse, nous avons prédit l’existence de nouveaux défauts tels que les macles quinaires et défauts de translations, tous observés et confirmés par nos observations en microscopie électronique haute résolution HREM et STEM-HAADFThe present work is an attempt to take advantage of the N-dimensional crystallographic description to rediscuss the structures of periodic metal alloys whose atoms are located on an ordered subset of a Z-module — positions that are integer linear combinations of N> 3 arithmetically independent vectors — like those encountered in quasicrystals and approximants. This N-dimensional crystallographic description makes it possible to reveal hidden symmetries in periodic metallic alloys, that can generate new types of possible defects by symmetry breaking during the projection in the physical space. Thus, in addition to the usual defects due to a local breaking of periodicity, these alloys may contain new defects corresponding to internal symmetry operations of the Z-module which are lost due to the periodicity of the alloy. These defects are twins, translation defects and dislocations that border them and that we refer to as dislocations of modules to differentiate them from the usual network dislocations and which appear as partial dislocations bordering one or more stacking faults. Particular dislocations may exist with Burgers vectors having a null component in the physical space. These dislocations, which we call scalar dislocations, generate no stress field and are not sensitive to any deformation field. The orthorhombic phase of NiZr has a crystal structure the atoms of which are located on a fraction of the pentagonal Z-module and is therefore fully describable at 5 dimensions. We can thus describe new defects such as quinary twins, but also defects of translations that all keep the Z-module invariant. All these defects have indeed been observed and recognized by high resolution electron microscopy (HREM and STEM-HAADF)
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Douat, Benjamin. "Étude de surfaces sous contrainte à l'échelle atomique : application au cas du niobium." Thesis, Poitiers, 2018. http://www.theses.fr/2018POIT2274/document.
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Les mécanismes de déformation plastique des matériaux cubiques à corps centré sont étudiés depuis plus d’un demi-siècle. Il est maintenant bien établi que les dislocations vis contrôlent la plasticité de ces matériaux. Ceci est dû à une structure non-plane du cœur de ces dislocations, qui induit une forte friction de réseau communément appelée ‘pseudo-Peierls’. Le mécanisme supposé est la nucléation thermiquement activée de paires de décrochements. Cette structure de cœur particulière limite également les plans de glissement possibles. Les traces de glissement aux échelles méso et microscopiques apparaissent ‘ondulées’, ce qui a amené à proposer toute une variété de plans de glissement.Dans ce contexte, nous avons analysé à une échelle plus fine, i .e. à l’échelle atomique, les traces de glissement obtenues par déformation en compression de monocristaux de niobium à des températures situées dans le régime de température thermiquement activé: 293 K, 200 K et 90 K. L’analyse par microscopie à effet tunnel sous environnement ultra vide indique qu’à la résolution atomique chaque trace de glissement peut être décomposée en segments associés à des plans de type {112} et {110}. De manière surprenante, il est mis en évidence qu’à 293 K et 200 K du glissement se produit à la fois dans le sens maclage et antimaclage. De plus, toutes les traces de glissement impliquent du glissement sur des plans de type {110}, étayant ainsi la structure de cœur compact prévue par simulations atomistiques ab initio.L’étude in situ de la surface sous contrainte, à T = 293 K et 200 K, a aussi mis en évidence des réorganisations, voire des disparitions, de terrasses atomiques au voisinage de dislocations émergentes. Le calcul des forces d’interaction en élasticité linéaire isotrope montre que les dislocations proches de ces terrasses ne jouent pas de rôle prépondérant sur la position d’équilibre des terrasses. En revanche, celles-ci modifient localement le potentiel chimique de surface, favorisant la diffusion atomique à l’origine des réorganisations de surface constatées expérimentalementThe plastic deformation of body-centred cubic metals is the subject of extensive studies since more than half a century. It is now well established that the screw dislocations control the plasticity of these metallic metals. The reason for this is attributed to a non-planar configuration of the core of these dislocations, which induces a high friction force usually referred to as ‘pseudo-Peierls’. The underlying elementary mechanism is the thermally activated nucleation of kink pairs. While perfect screw dislocations do not have specific glide plane, the non-planar core configuration limits the number of possible slip planes. The slip traces observed at the meso and microscopic scales are wavy, which has leaded to the proposal of several possible slip planes.In this context, we propose an analysis at a finer scale, i.e. the atomic scale, of the slip traces produced by compressive stress on niobium single crystals at three temperatures in the thermally activated temperature regime, namely: 293 K, 200 K and 90 K. The analyses were carried out using a scanning tunnelling microscope under ultra-high vacuum environment. At this scale of observation, the slip traces are made up of crystallographic segments that can be associated with {011} and {112} planes. It is also noticeable that at 200 K and 293 K dislocation glide is observed in both the twinning and the anti-twinning directions. More importantly, all slip traces include segments that belong to {011} planes strongly supporting the latest ab initio atomistic simulations predicting a compact core configuration for screw dislocation.In this study, we also established that, at T = 293 K and 200 K, the sample surface may undergo drastic changes of its vicinal terraces, when they are close to emerging dislocations. The calculation of interaction forces, in the frame of isotropic linear elasticity, indicates that dislocations close to vicinal terraces do not play a major role regarding the stable positions of the vicinal terraces. However, they locally modify the chemical potential of the surface, thus enhancing atomic diffusion which is at the origin of the surface reorganisations experimentally observed
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Poty, Alexandre. "Etude de la plasticité dans les métaux hexagonaux à l'échelle atomique : dynamique des dislocations par dynamique moléculaire." Thesis, Metz, 2011. http://www.theses.fr/2011METZ010S/document.
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La mise en forme des matériaux passe par la déformation à l'échelle atomique de sa structure. Cette déformation implique la création et le déplacement de défauts tels que les dislocations. La mobilité des dislocations joue un rôle majeur dans la plasticité des matériaux. Il existe différents types de dislocations se déplaçant sur différents systèmes. Actuellement les systèmes de glissement principaux sont bien connus mais les systèmes secondaires, essentiels à la bonne modélisation du comportement plastique, ne le sont pas. Notre travail est de définir les systèmes principaux et secondaires, de les hiérarchiser et de donner une valeur de la contrainte permettant l'activation de la dislocation. Nous avons pour cela choisi d’utiliser la méthode de la Dynamique Moléculaire associée à des potentiels de type Embedded Atom Method (EAM). Nous avons débuté notre étude par la comparaison des performances des différents potentiels de Zirconium et de Titane publiés dans la littérature par rapport aux propriétés plastiques et élastiques obtenues expérimentalement ou par méthode ab initio. Nous avons ensuite étudié les dislocations coins dans les plans prismatiques 1, basal et pyramidal type 1. Nous avons calculé les cissions critiques d'activation de ces dislocations dans le Zirconium et le Titane. Nous nous sommes enfin intéressés aux énergies de fautes des différents plans de glissement du Zirconium et du Titane. Nous avons pour cela calculé toutes les surfaces γ de ces deux métaux. Nous avons comparé les résultats obtenus par dynamique moléculaire à des résultats obtenus par méthode ab initio. Nous avons ensuite donné un classement des différents plans de glissementThe forming of a material requires the deformation at an atomic level of his structure. This deformation involves the creation and movement of defaults like the dislocations. The dislocations mobility plays a major role in the plasticity of the materials. There are different types of dislocations gliding on different gliding systems. Currently the principal gliding systems are well known but the secondary systems aren't. Our work is to define the principal and the secondary gliding systems, to rank them and to calculate the value of the critical resolved shear stress responsible for the dislocation movement. For that we chose to use Molecular Dynamics with EAM (Embedded Atom Method) potentials. We began our studies by comparing the results of several EAM potentials for Zirconium and Titanium to the plastic and elastic properties obtained experimentally or by ab initio calculation.We studied edge dislocations in the prismatic, basal and pyramidal 1 planes. We calculated the critical resolved shear stress of these dislocations in Zirconium and Titanium. Finally we got interested in the fault energies of several gliding planes of Zirconium and Titanium. For that we calculated the γ surfaces of those planes. We compared results obtained by molecular dynamics to results obtained by ab initio calculation. We finally gave a classification of those planes
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Chen, Albert Yi Fu 1967. "Art and social dislocation : a Chinese diasporic condition." Monash University, Dept. of Fine Arts, 2004. http://arrow.monash.edu.au/hdl/1959.1/5203.
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Scafesi, Oana Sanda. "Evaluation of propriocetion in patients with anterior dislocation." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape10/PQDD_0001/MQ40879.pdf.
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Arsenlis, Athanasios 1975. "Modeling dislocation density evolution in continuum crystal plasticity." Thesis, Massachusetts Institute of Technology, 2001. http://hdl.handle.net/1721.1/36679.
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Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2001.Includes bibliographical references (p. 221-229).
Dislocations are the singly most important material defects in crystal plasticity, and although dislocation mechanics has long been understood as the underlying physical basis for continuum crystal plasticity formulations, explicit consideration of crystallo- graphic dislocation mechanics has been largely absent in working constitutive models. In light of recent theoretical developments in dislocation dynamics, and the introduc- tion of geometrically necessary dislocation (GND) density in continuum formulations through plastic strain gradients, a single crystal plasticity model based on dislocation density state variables is developed. The density state variables evolve from initial conditions according to equations based on fundamental concepts in dislocation me- chanics such as the conservation of Burgers vector in multiplication and annihilation processes. Along with those processes that account for bulk statistical dislocation evolution, the evolving polarity due to dislocation species flux divergences may be in- cluded to detail the length-scale dependence of mechanical properties on the micron level. The full dislocation density description of plasticity allows a simple evaluation of the role of GND density in non-homogeneously deforming bodies. A local version of the constitutive model, which captures the bulk processes of dislocation multiplication and annihilation during plastic deformation, is implemented within a finite element framework to investigate the poly-slip behavior of aluminum single crystals under tension.
(cont.) A non-local version of the constitutive model using an idealized planar double slip system geometry is implemented within a finite element framework to investigate the length-scale dependence observed in the bending of thin single crystal beams. The results not only capture the mechanical stress/strain response of the material, but also detail the development of underlying dislocation structure responsible_ fr: the plistic behavior of the crystal.
by Athanasios Arsenlis.
Ph.D.