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Articles de revues sur le sujet "Dislocation Dynamics Simulations"
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Mani Krishna, Karri V., et Prita Pant. « Dislocation Dynamics Simulations ». Materials Science Forum 736 (décembre 2012) : 13–20. http://dx.doi.org/10.4028/www.scientific.net/msf.736.13.
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Dislocation Dynamics (DD) simulations are used to study the evolution of a pre-specified dislocation structure under applied stresses and imposed boundary conditions. These simulations can handle realistic dislocation densities ranging from 1010 to 1014 m-2, and hence can be used to model plastic deformation and strain hardening in metals. In this paper we introduce the basic concepts of DD simulations and then present results from simulations in thin copper films and in bulk zirconium. In both cases, the effect of orientation on deformation behaviour is investigated. For the thin film simulations, rigid boundary conditions are used at film-substrate and film-passivation interfaces leading to dislocation accumulation, while periodic boundaries are used for bulk grains of Zr. We show that there is a clear correlation between strain hardening rate and the rate of increase of dislocation density.
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Demir, I., et A. N. Gulluoglu. « Dislocation Dynamics Simulations in the Presence of Interacting Cracks ». Journal of Engineering Materials and Technology 121, no 2 (1 avril 1999) : 151–55. http://dx.doi.org/10.1115/1.2812360.
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For an understanding failure behavior of crystalline solids, considerable interest is given to investigating interaction effects between the main crack and microcracks in the presence of mobile dislocations. Accurate analysis of these types of interaction problems may lead to accurate models for failure prevention and the history of plastic zone development. High stress concentration areas such as crack tips are the places where dislocations are subjected to higher forces. Therefore, a computer simulation technique based on dislocation dynamics has been developed to investigate the movement of dislocations in the presence of multiple cracks. Dislocation structures, dislocation distribution and strain rate results are presented as functions of applied stresses for different microcrack positions and orientations. Simulation results give a reasonable description of dislocation pattern development during deformation around the cracks and explain the shape and development of the plastic zone.
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YANG, XIYUAN. « THE MOBILITY OF THE EDGE DISLOCATION IN METAL : A MOLECULAR DYNAMICS SIMULATION ». International Journal of Modern Physics B 25, no 25 (10 octobre 2011) : 3315–24. http://dx.doi.org/10.1142/s021797921110103x.
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In this paper, we use molecular dynamics (MD) simulations and a modified analytic embedded-atom method to investigate the edge dislocation movement without imposed strain at 0 K. The obtained results indicate that the straight lines of the partial dislocations always preserve their original shapes and are parallel to each other during the simulation process. According to the energy of each atom, the positions of both partial dislocation cores are determined. Then the velocities in the period of the relaxation process are investigated in detail. The MD simulations reveal that the MD relaxation time dependence of the edge dislocation mobility is divided into two parts. First, during the initial period ranging from 0 to 6 ps, the relative velocity of the dislocation movement lineally increases with the incremental relaxation time. Second, in the latter period from 6 ps to the end of the simulated process the velocity decreases exponentially as the MD simulation time evolves.
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Derlet, P. M., P. Gumbsch, R. Hoagland, J. Li, D. L. McDowell, H. Van Swygenhoven et J. Wang. « Atomistic Simulations of Dislocations in Confined Volumes ». MRS Bulletin 34, no 3 (mars 2009) : 184–89. http://dx.doi.org/10.1557/mrs2009.50.
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AbstractInternal microstructural length scales play a fundamental role in the strength and ductility of a material. Grain boundaries in nanocrystalline structures and heterointerfaces in nanolaminates can restrict dislocation propagation and also act as a source for new dislocations, thereby affecting the detailed dynamics of dislocation-mediated plasticity. Atomistic simulation has played an important and complementary role to experiment in elucidating the nature of the dislocation/interface interaction, demonstrating a diversity of atomic-scale processes covering dislocation nucleation, propagation, absorption, and transmission at interfaces. This article reviews some atomistic simulation work that has made progress in this field and discusses possible strategies in overcoming the inherent time scale challenge of finite temperature molecular dynamics.
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Deng, Jie, et Anter El-Azab. « Dislocation pair correlations from dislocation dynamics simulations ». Journal of Computer-Aided Materials Design 14, S1 (décembre 2007) : 295–307. http://dx.doi.org/10.1007/s10820-008-9090-4.
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Roy, Shyamal, Sönke Wille, Dan Mordehai et Cynthia A. Volkert. « Investigating Nanoscale Contact Using AFM-Based Indentation and Molecular Dynamics Simulations ». Metals 12, no 3 (14 mars 2022) : 489. http://dx.doi.org/10.3390/met12030489.
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In this work we study nanocontact plasticity in Au thin films using an atomic force microscope based indentation method with the goal of relating the changes in surface morphology to the dislocations created by deformation. This provides a rigorous test of our understanding of deformation and dislocation mechanisms in small volumes. A series of indentation experiments with increasing maximum load was performed. Distinct elastic and plastic regimes were identified in the force-displacement curves, and the corresponding residual imprints were measured. Transmission electron microscope based measured dislocation densities appear to be smaller than the densities expected from the measured residual indents. With the help of molecular dynamics simulations we show that dislocation nucleation and glide alone fail to explain the low dislocation density. Increasing the temperature of the simulations accelerates the rate of thermally activated processes and promotes motion and annihilation of dislocations under the indent while transferring material to the upper surface; dislocation density decreases in the plastic zone and material piles up around the indent. Finally, we discuss why a significant number of cross-slip events is expected beneath the indent under experimental conditions and the implications of this for work hardening during wear.
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J. Chavez, Jose, Xiao W. Zhou, Sergio F. Almeida, Rodolfo Aguirre et David Zubia. « Molecular Dynamics Simulations of CdTe / CdS Heteroepitaxy - Effect of Substrate Orientation ». Journal of Materials Science Research 5, no 3 (7 avril 2016) : 1. http://dx.doi.org/10.5539/jmsr.v5n3p1.
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<p class="1Body">Molecular dynamics simulations were used to catalogue atomic scale structures of CdTe films grown on eight wurtzite (wz) and zinc-blende (zb) CdS surfaces. Polytypism, grain boundaries, dislocations and other film defects were detected. Dislocation lines were distributed in three distinct ways. For the growths on the wz {0001} and zb {111} surfaces, dislocations were found throughout the epilayers and formed a network at the interface. The dislocations within the films grown on the wz {1100}, wz {1120}, zb {110}, zb {010}, and zb {1/10 1 1/10} surfaces formed an interface network and also threaded from the interface towards the film’s surface. In contrast, the growth on the zb {112} surface only had dislocations localized to the interface. This film exhibited a different orientation from the substrate to reduce the lattice mismatch strain energies, and therefore, its misfit dislocation density. Our study indicates that the substrate orientation could be utilized to modify the morphology of dislocation networks in lattice mismatched multi-layered systems.</p>
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Godiksen, Rasmus B., Zachary T. Trautt, Moneesh Upmanyu, Søren Schmidt et Dorte Juul Jensen. « Simulation of Recrystallization Using Molecular Dynamics ; Effects of the Interatomic Potential ». Materials Science Forum 558-559 (octobre 2007) : 1081–86. http://dx.doi.org/10.4028/www.scientific.net/msf.558-559.1081.
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Recrystallization is governed by the migration of high angle grain boundaries traveling through a deformed material driven by the excess energy located primarily in dislocation structures. A method for investigating the interaction between a migrating grain boundary and dislocation boundaries using molecular dynamics (MD) was recently developed. During simulations migrating high angle grain boundaries interact with dislocation boundaries, and individual dislocations from the dislocation boundaries are absorbed into the grain boundaries. Results obtained previously, using a simple Lennard-Jones (LJ) potential, showed surprisingly irregular grain boundary migration compared to simulations of grain boundary migration applying other types of driving forces. Inhomogeneous boundary-dislocation interactions were also observed in which the grain boundaries locally acquired significant cusps during dislocation absorption events. The study presented here makes comparisons between simulations performed using a LJ- and an embedded atom method (EAM) aluminum potential. The results show similarities which indicate that it is the crystallographic features rather than the atomic interactions that determine the details of the migration process.
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Liu, Jianbin, et Shinji Muraishi. « Dislocation Dynamics Simulations of Dislocation-Particle Bypass Mechanisms ». Materials Science Forum 985 (avril 2020) : 35–41. http://dx.doi.org/10.4028/www.scientific.net/msf.985.35.
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Effect of precipitation strengthening on metal is generally attributed to the dislocation interaction with the precipitate which acts as the barrier to the dislocation motion on the slip plane. In order to achieve better understanding of critical events of dislocation motion and evolution of dislocation microstructure, we have developed numerical simulation method of dislocation-dislocation and dislocation-particle interactions by means of discrete dislocation dynamics at mesoscopic scale. In this work, Green’s function method is utilized for the computation of the stress fields of dislocation and misfitting particle, and the interaction forces acting on the dislocation. We also proposed the efficient algorithm of the connectivity vector for the dislocation line elements, linked-list data structure, to deal with the flexible interaction of dislocation line elements. The geometrical effect of dislocation slip planes on the dislocation bypassing behaviors is tested by changing the relative height of dislocation slip plane against the center plane of spherical particle, where cross slip event is also taken into account for the dislocation motion. Simulation results show a wide variety of topological changes of dislocation during motion on the slip planes around the particle, which results from the stress field of the particle varied with the relative height between the dislocation slip plane and center plane of particle. The full analysis of the mechanisms of dislocation line bypassing misfitting particle has been explained in this study.
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Jones, Reese E., Jonathan A. Zimmerman et Giacomo Po. « Comparison of Dislocation Density Tensor Fields Derived from Discrete Dislocation Dynamics and Crystal Plasticity Simulations of Torsion ». Journal of Materials Science Research 5, no 4 (1 septembre 2016) : 44. http://dx.doi.org/10.5539/jmsr.v5n4p44.
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<p class="1Body">The importance of accurate simulation of the plastic deformation of ductile metals to the design of structures and components is well-known. Many techniques exist that address the length scales relevant to deformation processes, including dislocation dynamics (DD), which models the interaction and evolution of discrete dislocation line segments, and crystal plasticity (CP), which incorporates the crystalline nature and restricted motion of dislocations into a higher scale continuous field framework. While these two methods are conceptually related, there have been only nominal efforts focused on the system-level material response that use DD-generated information to enhance the fidelity of plasticity models. To ascertain to what degree the predictions of CP are consistent with those of DD, we compare their global and microstructural response in a number of deformation modes. After using nominally homogeneous compression and shear deformation dislocation dynamics simulations to calibrate crystal plasticity flow rule parameters, we compare not only the system-level stress-strain response of prismatic wires in torsion but also the resulting geometrically necessary dislocation density tensor fields. To establish a connection between explicit description of dislocations and the continuum assumed with crystal plasticity simulations, we ascertain the minimum length-scale at which meaningful dislocation density fields appear. Our results show that, for the case of torsion, the two material models can produce comparable spatial dislocation density distributions.</p>
Thèses sur le sujet "Dislocation Dynamics Simulations"
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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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Wu, Han. « Dislocation Dynamics Simulations of Plasticity in Cu Thin Films ». Thesis, University of North Texas, 2013. https://digital.library.unt.edu/ark:/67531/metadc500046/.
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Strong size effects in plastic deformation of thin films have been experimentally observed, indicating non-traditional deformation mechanisms. These observations require improved understanding of the behavior of dislocation in small size materials, as they are the primary plastic deformation carrier. Dislocation dynamics (DD) is a computational method that is capable of directly simulating the motion and interaction of dislocations in crystalline materials. This provides a convenient approach to study micro plasticity in thin films. While two-dimensional dislocation dynamics simulation in thin film proved that the size effect fits Hall-Petch equation very well, there are issues related to three-dimensional size effects. In this work, three-dimensional dislocation dynamics simulations are used to study model cooper thin film deformation. Grain boundary is modeled as impenetrable obstacle to dislocation motion in this work. Both tension and cyclic loadings are applied and a wide range of size and geometry of thin films are studied. The results not only compare well with experimentally observed size effects on thin film strength, but also provide many details on dislocation processes in thin films, which could greatly help formulate new mechanisms of dislocation-based plasticity.
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Jiang, Maoyuan. « Investigation of grain size and shape effects on crystal plasticity by dislocation dynamics simulations ». Thesis, Université Paris-Saclay (ComUE), 2019. http://www.theses.fr/2019SACLC035/document.
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Des simulations de dynamique de dislocation (DD) sont utilisées pour l’étude de l'effet Hall-Petch (HP) et des contraintes internes à long-portée induites par les hétérogénéités de déformation dans les matériaux polycristallins.L'effet HP est reproduit avec succès grâce à des simulations de DD réalisées sur de simples agrégats polycristallins périodiques composés de 1 ou de 4 grains. De plus, l'influence de la forme des grains a été explorée en simulant des grains avec différents rapports d'aspect. Une loi généralisée de HP est proposée pour quantifier l'influence de la morphologie du grain en définissant une taille de grain effective. La valeur moyenne de la constante HP $K$ calculée avec différentes orientations cristallines à faible déformation est proche des valeurs expérimentales.Les dislocations stockées pendant la déformation sont principalement localisées à proximité des joints de grain et peuvent être traitées comme une distribution surfacique de dislocations. Nous avons utilisé des simulations DD pour calculer les contraintes associées aux parois de dislocations de différentes hauteurs, longueurs densités et caractères. Dans tous les cas, la contrainte est proportionnelle à la densité surfacique de dislocations géométriquement nécessaires (GNDs) et sa variation est capturée par un ensemble d'équations empiriques simples. Une prévision de contraintes à long-portée dans les grains est réalisée en sommant les contributions des GNDs accumulées de part et d’autre des joints de grains.L'augmentation de la contrainte interne liée au stockage de GNDs est linéaire avec la déformation plastique et est indépendante de la taille des grains. L'effet de taille observé dans les simulations de DD est attribué au seuil de déformation plastique, contrôlé par deux mécanismes concurrents : la contrainte critique de multiplication des sources et la contrainte critique de franchissement de la forêt. En raison de la localisation de la déformation dans les matériaux à gros grains, le modèle d’empilement des dislocations doit être utilisé pour prédire la contrainte critique dans ce cas. En superposant cette propriété aux analyses que nous avons fait à partir de simulations de DD dans le cas d'une déformation homogène, l'effet HP est justifié pour une large gamme de tailles de grainsDislocation Dynamics (DD) simulations are used to investigate the Hall-Petch (HP) effect and back stresses induced by grain boundaries (GB) in polycrystalline materials.The HP effect is successfully reproduced with DD simulations in simple periodic polycrystalline aggregates composed of 1 or 4 grains. In addition, the influence of grain shape was explored by simulating grains with different aspect ratios. A generalized HP law is proposed to quantify the influence of the grain morphology by defining an effective grain size. The average value of the HP constant K calculated with different crystal orientations at low strain is close to the experimental values.The dislocations stored during deformation are mainly located at GB and can be dealt with as a surface distribution of Geometrically Necessary Dislocations (GNDs). We used DD simulations to compute the back stresses induced by finite dislocation walls of different height, width, density and character. In all cases, back stresses are found proportional to the surface density and their spatial variations can be captured using a set of simple empirical equations. The back stress calculation inside grains is achieved by adding the contributions of GNDs accumulated at each GB facet.These back stresses are found to increase linearly with plastic strain and are independent of the grain size. The observed size effect in DD simulations is attributed to the threshold of plastic deformation, controlled by two competing mechanisms: the activation of dislocation sources and forest strengthening. Due to strain localization in coarse-grained materials, the pile-up model is used to predict the critical stress. By superposing such property to the analysis we made from DD simulations in the case of homogeneous deformation, the HP effect is justified for a wide range of grain sizes
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Tschopp, Mark Allen. « Atomistic Simulations of Dislocation Nucleation in Single Crystals and Grain Boundaries ». Diss., Georgia Institute of Technology, 2007. http://hdl.handle.net/1853/16239.
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The objective of this research is to use atomistic simulations to investigate dislocation nucleation from grain boundaries in face-centered cubic aluminum and copper. This research primarily focuses on asymmetric tilt grain boundaries and has three main components. First, this research uses molecular statics simulations of the structure and energy of these faceted, dissociated grain boundary structures to show that Σ3 asymmetric boundaries can be decomposed into the structural units of the Σ3 symmetric tilt grain boundaries, i.e., the coherent and incoherent twin boundaries. Moreover, the energy for all Σ3 asymmetric boundaries is predicted with only the energies of the Σ3 symmetric boundaries and the inclination angle. Understanding the structure of these boundaries provides insight into dislocation nucleation from these boundaries. Further work into the structure and energy of other low order Σ asymmetric boundaries and the spatial distribution of free volume within the grain boundaries also provides insight into dislocation nucleation mechanisms. Second, this research uses molecular dynamics deformation simulations with uniaxial tension applied perpendicular to these boundaries to show that the dislocation nucleation mechanisms in asymmetric boundaries are highly dependent on the faceted, dissociated structure. Grain boundary dislocation sources can act as perfect sources/sinks for dislocations or may violate this premise by increasing the dislocation content of the boundary during nucleation. Furthermore, simulations under uniaxial tension and uniaxial compression show that nucleation of the second partial dislocation in copper exhibits tension-compression asymmetry. Third, this research explores the development of models that incorporate the resolved stress components on the slip system of dislocation nucleation to predict the atomic stress required for dislocation nucleation from single crystals and grain boundaries. Single crystal simulations of homogeneous dislocation nucleation help define the role of lattice orientation on the nucleation stress for grain boundaries. The resolved stress normal to the slip plane on which the dislocation nucleates plays an integral role in the dislocation nucleation stress and related mechanisms. In summary, the synthesis of various aspects of this work has provided improved understanding of how the grain boundary character influences dislocation nucleation in bicrystals, with possible implications for nanocrystalline materials.
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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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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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Guduguntla, Varun. « Effects of Thermostats in Molecular Dynamics Simulations of Nanoindentation ». University of Cincinnati / OhioLINK, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1573573614853041.
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Shukeir, Malik. « Modeling of irradiation effect on the plasticity of alpha-Iron using dislocation dynamics simulations : plasticity through multi-scale modeling ». Electronic Thesis or Diss., Sorbonne université, 2019. http://www.theses.fr/2019SORUS363.
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Ce travail vise à reproduire les interactions individuelles entre les dislocations vis et les boucles induites par l'irradiation en utilisant les simulations de dynamique des dislocations en accord avec les simulations de dynamique moléculaire. Un tel accord se caractérise par la reproduction de la réaction et avoir un valeur des contraintes critiques résolues pour franchir les obstacles. Cette approche fournit le moyen de calibrer notre code de dynamique des dislocations avec les paramètres des simulations de dynamique moléculaire. Par conséquent, il permet d'effectuer des simulations massives à l'échelle mésoscopique. Dans ce cadre, ce travail se compose de deux parties, une identification du modèle énergétique et une identification des mécanismes élémentaires. Dans la première partie, nous proposons une procédure de calibrage de la tension ligne basée sur le mécanisme d'Orowan en utilisant une étude de sensibilité. Dans la deuxième partie, nous avons identifié les mécanismes de glissement dévié et le maclage/antimaclage comme étant essentiels pour reproduire les interactions individuelles de dislocation-boucle. Les simulations de la dynamique des dislocations sont réalisées à l'aide d'un code nodal 3D appelé NUMODIS, où les développements récents dans ce code sont présentés. Un des caractéristiques de ce code est sa capacité à gérer et contrôler les collisions entre les segments des dislocations. Cela se fait au moyen en utilisant un ensemble d'algorithmes génériques avec un minimum de règles localesThis work aims to reproduce the individual interactions between screw dislocations and radiation-induced loops using dislocation dynamics in good agreement with molecular dynamics simulations. Such agreement is characterized by reproducing the dynamics of the reaction and obtaining the critical resolved stress to overcome the obstacles. This approach provides the mean to calibrate our dislocation dynamics code with parameters from the molecular dynamics simulations. Consequently, it permits to perform massive simulations at the mesoscopic scale. In this scope, this work consists of two parts, an identification of the energetic model and identification of elementary mechanisms. In the first part we propose a procedure to calibrate the line tension based on Orowan's mechanism using a sensibility study. In the second part, we have identified the cross-slip and twining/anti-twinning mechanisms to be essential to reproduce the individual dislocation-loop interactions. The dislocation dynamics simulations are done using a 3D nodal code called NUMODIS, where the recent developments in this code are presented. The uniqueness of this code is its ability to manage and control collisions and core reactions between dislocation segments. This is done through a set of generic algorithms with the minimum amount of local rules
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Jover, Carrasco Elena. « Simulations 3D des interactions entre fissure et dislocations ». Thesis, Université Grenoble Alpes, 2022. https://tel.archives-ouvertes.fr/tel-03689315.
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La ténacité à la rupture est contrôlée non seulement par les paramètres macroscopiques mais aussi par la microstructure. Les défauts de la structure cristalline comme les lacunes, les inclusions ou les dislocations peuvent aussi grandement impacter la ténacité. Pour mieux comprendre ce phénomène, on mènera des simulations 3D d'un front de fissure interagissant avec des dislocations. Ces simulations visent à mesurer les variations des facteurs d'intensité des contraintes sur le front de fissure créées par la présence de dislocations. Pour cela, on combinera deux modèles préexistants : la méthode des éléments finis étendus (XFEM) et la dynamique des dislocations discrètes (DDD). XFEM est une évolution de la méthode des éléments fini qui permet l'étude d'une fissure qui se propage sans avoir besoin de remaillage, elle contrôlera le volume étudié, le chargement appliqué et la position de la fissure tandis que tant que la DDD contrôlera les dislocations, leur mouvement et leur multiplication. La précision du modèle crée sera testée en le comparant avec des résultats de simulations atomistiques. Pour mesurer qualitativement les effets des dislocations sur la ténacité, plusieurs dislocations avec des différents systèmes de glissement seront étudiées. D'autres paramètres comme la distance entre la fissure et la dislocation, la direction de la fissure, et la déformation initiale seront aussi étudiées. Pour comparer le modèle étudié avec des résultats provenant d'autres simulations, deux orientations de fissure seront simulées. Les dislocations étudiées ont des effets sur la fissure différents en fonction de leur système de glissement. Les résultats montrent des dislocations créant soit de l'écrantage, doit de l'anti-écrantage soit une combinaison des deux. Ces effets sont uniquement dépendants de la nature de la dislocation et ne changent pas quand la direction du vecteur de ligne de la dislocation change, ni quand la dislocation est plus éloignée de la fissure, même si l'intensité de l'effet change. De plus, les dislocations étant associées à un état de cisaillement local, elles affectent plus fortement KII que KI. KII contrôle aussi l'angle de propagation de la fissure, ce qui implique que les dislocations sont une des principales sources des déviations des fissuresFracture toughness in materials is not only controlled by macroscopic parameters but also by the microstructure. The defects of the crystalline structure such as voids, inclusions or dislocations can also greatly impact toughness. To better understand this, 3D simulations of a crack front interacting with dislocations will be carried out. These simulations aim at measuring the variations of the stress intensity factors on the crack front caused by the presence of dislocations. To carry out these simulations, two preexisting models will be combined: Extended Finite Elements Method (XFEM) and Discrete Dislocation Dynamics (DDD). XFEM is an evolution of the Finite Elements Methods that allows the study of a propagating crack without needing to remesh, it will control the studied volume, the applied loading and the crack position while DDD controls the dislocations, their movement, and their multiplication. The accuracy of the created model is tested by comparisons with atomistic simulations. To test the effect of dislocations on toughness, several dislocations with different slip systems were studied. Other parameters such as dislocation crack distance, line direction, and initial strain were also studied. To compare the studied model with existing simulation results, two crack orientations were selected. The studied dislocations have different behaviors depending on their slip system. The results show dislocations creating shielding, antishielding or a combination of both. These effects are only dependent of the dislocation nature, and do not change when the dislocation line direction changes or if the dislocation is farther from the crack, though the intensity of the effect does change given these circumstances. Since the presence of dislocations is associated to a shear stress in their glide planes, it is found that they have more effect on KII than on KI. KII also controls the crack propagation angle, which means that the dislocations are one of the main sources of crack deviation
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Ye, Wei. « Nano-epitaxy modeling and design : from atomistic simulations to continuum methods ». Diss., Georgia Institute of Technology, 2013. http://hdl.handle.net/1853/50304.
Texte intégralRésumé :
The dissertation starts from the understanding of dislocation dissipation mechanism due to the image force acting on the dislocation. This work implements a screw dislocation in solids with free surfaces by a novel finite element model, and then image forces of dislocations embedded in various shaped GaN nanorods are calculated. As surface stress could dramatically influence the behavior of nanostructures, this work has developed a novel analytical framework to solve the stress field of solids with dislocations and surface stress. It is successfully implemented in this framework for the case of isotropic circular nanowires (2D) and the analytical result of the image force has been derived afterwards. Based on the finite element analysis and the analytical framework, this work has a semi-analytical solution to the image force of isotropic nanorods (3D) with surface stress. The influences of the geometrical parameter and surface stress are illustrated and compared with the original finite element result. In continuation, this work has extended the semi-analytical approach to the case of anisotropic GaN nanorods. It is used to analyze image forces on different dislocations in GaN nanorods oriented along polar (c-axis) and non-polar (a, m-axis) directions. This work could contribute to a wide range of nanostructure design and fabrication for dislocation-free devices.
Chapitres de livres sur le sujet "Dislocation Dynamics Simulations"
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Cai, Wei, Vasily V. Bulatov, Tim G. Pierce, Masato Hiratani, Moono Rhee, Maria Bartelt et Meijie Tang. « Massively-Parallel Dislocation Dynamics Simulations ». Dans Solid Mechanics and its Applications, 1–11. Dordrecht : Springer Netherlands, 2004. http://dx.doi.org/10.1007/978-1-4020-2111-4_1.
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Sills, Ryan B., William P. Kuykendall, Amin Aghaei et Wei Cai. « Fundamentals of Dislocation Dynamics Simulations ». Dans Multiscale Materials Modeling for Nanomechanics, 53–87. Cham : Springer International Publishing, 2016. http://dx.doi.org/10.1007/978-3-319-33480-6_2.
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LeSar, Richard, et Laurent Capolungo. « Advances in Discrete Dislocation Dynamics Simulations ». Dans Handbook of Materials Modeling, 1079–110. Cham : Springer International Publishing, 2020. http://dx.doi.org/10.1007/978-3-319-44677-6_85.
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Mohles, Volker. « Dislocation Dynamics Simulations of Particle Strengthening ». Dans Continuum Scale Simulation of Engineering Materials, 375–95. Weinheim, FRG : Wiley-VCH Verlag GmbH & Co. KGaA, 2005. http://dx.doi.org/10.1002/3527603786.ch17.
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LeSar, Richard, et Laurent Capolungo. « Advances in Discrete Dislocation Dynamics Simulations ». Dans Handbook of Materials Modeling, 1–32. Cham : Springer International Publishing, 2018. http://dx.doi.org/10.1007/978-3-319-42913-7_85-1.
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Sills, R. B., et S. Aubry. « Line Dislocation Dynamics Simulations with Complex Physics ». Dans Handbook of Materials Modeling, 1559–81. Cham : Springer International Publishing, 2020. http://dx.doi.org/10.1007/978-3-319-44677-6_19.
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Sills, R. B., et S. Aubry. « Line Dislocation Dynamics Simulations with Complex Physics ». Dans Handbook of Materials Modeling, 1–23. Cham : Springer International Publishing, 2018. http://dx.doi.org/10.1007/978-3-319-42913-7_19-1.
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Marian, Jaime, Steve Fitzgerald et Giacomo Po. « Discrete Dislocation Dynamics Simulations of Irradiation Hardening in Nuclear Materials ». Dans Handbook of Materials Modeling, 2243–71. Cham : Springer International Publishing, 2020. http://dx.doi.org/10.1007/978-3-319-44680-6_121.
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Marian, Jaime, Steve Fitzgerald et Giacomo Po. « Discrete Dislocation Dynamics Simulations of Irradiation Hardening in Nuclear Materials ». Dans Handbook of Materials Modeling, 1–29. Cham : Springer International Publishing, 2018. http://dx.doi.org/10.1007/978-3-319-50257-1_121-1.
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Devincre, B. « Atypical Plastic Properties of Ni3AL Alloys Studied by Dislocation Dynamics Simulations ». Dans Multiscale Phenomena in Plasticity : From Experiments to Phenomenology, Modelling and Materials Engineering, 319–28. Dordrecht : Springer Netherlands, 2000. http://dx.doi.org/10.1007/978-94-011-4048-5_25.
Texte intégralActes de conférences sur le sujet "Dislocation Dynamics Simulations"
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Asari, Keisuke, Satoshi Miyashiro, Mitsuhiro Itakura et Taira Okita. « Fundamental Study to Evaluate Mechanical Property Change Associated to Dislocation Behavior in Irradiated Austenitic Stainless Steels by Incorporating Thermal Fluctuations ». Dans 2013 21st International Conference on Nuclear Engineering. American Society of Mechanical Engineers, 2013. http://dx.doi.org/10.1115/icone21-16428.
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Molecular dynamics simulations were conducted with three interatomic potentials for face-centered cubic (FCC) metals with different stacking fault energies (SFEs), and the effect of the SFE on the dislocation behaviors was evaluated by incorporating thermal fluctuation. The separation distance between two partial dislocations fluctuated and was changed locally by thermal vibration, and the fluctuation increased with temperature. For a low-SFE metal, thermal vibration can hardly induce reversions into a perfect dislocation. This causes a characteristic morphology for interactions between a line dislocation and irradiation-induced defects for austenitic stainless steels.
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Li, Baozhen. « Molecular Dynamics Simulations of Deformation Behavior of AlN in Nanoscratching ». Dans ASME 2020 15th International Manufacturing Science and Engineering Conference. American Society of Mechanical Engineers, 2020. http://dx.doi.org/10.1115/msec2020-8222.
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Abstract During the past few years aluminum nitride (AlN) as an important semiconductor material has attracted more and more attention owing to its splendid physical and mechanical properties. In this paper, molecular dynamics simulations of nanoscratching process of AlN are carried out study the deformation behaviors of AlN. The effects of scratching depth on the scratching force, workpiece pile-up and dislocation formation and motion are thoroughly studied. We found that the plastic deformation of AlN is mainly caused by the dislocation nucleation and motion in the nanoscratching process. In this study, we note that the workpiece material undergoes plastic deformation predominant by dislocation activity. In order to investigate the effects of the basic factors that play an important role in the scratching process, we further performed a series of MD simulations of scratching on the AlN(0001) surface along the [-12-10] direction. And it can be seen that there is a critical scratching depth for the transformation from elastic deformation to plastic deformation. The results suggest that the friction and normal force are bigger for a larger scratching depth. We also found the phenomenon of ultra-low friction under shallow scratches of AlN in the scratching process. The ultralow friction force at the scratching depth of 1nm is because of the absence of permanent plastic deformation of workpiece. The deformation under the abrasive begins to recover after the abrasive moves forward. This is the possible reason for the occurrence of ultra-low friction. These results shed light on the material deformation mechanism in nanoscratching process of AlN.
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Spearot, Douglas E., Karl I. Jacob et David L. McDowell. « Molecular Dynamics Simulations of Dislocation Nucleation From Bicrystal Interfaces in FCC Metals ». Dans ASME 2005 International Mechanical Engineering Congress and Exposition. ASMEDC, 2005. http://dx.doi.org/10.1115/imece2005-82092.
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Atomistic simulations are used to study dislocation nucleation from <001> tilt bicrystal interfaces in copper subjected to a tensile deformation. Specifically, three interface misorientations are examined, including the Σ5 (310) interface, which has a high density of coincident atomic sites. The initial interface configurations, which are discussed in terms of structural units, are refined using energy minimization techniques. Molecular dynamics simulations are then used to deform each interface in tension. The role of boundary conditions and their effect on the inelastic deformation response is discussed in detail. Molecular dynamics simulations show that the interface structural units are directly involved in the partial dislocation nucleation process. The maximum tensile strength of the Σ5 (310) interface shows a modest increase in the case where lateral confinement of the interface is an important consideration.
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Lin, Pandong, Junfeng Nie et Meidan Liu. « Point Defect Effects on Tensile Strength of BCC-Fe Studied by Molecular Dynamics ». Dans 2020 International Conference on Nuclear Engineering collocated with the ASME 2020 Power Conference. American Society of Mechanical Engineers, 2020. http://dx.doi.org/10.1115/icone2020-16162.
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Abstract BCC-Fe is the critical and major component of the reactor pressure vessel (RPV) steel. With long-tern neutron irradiation, many point defects can be obtained in RPV steel. In this paper, the points defects (interstitial, vacancy and Frenkel pair) effects on the tensile strength of Fe are studied by molecular dynamics simulations at 300K. The uni-axial tensile load is along [001] direction of the Fe samples loading in constant strain rate. The Fe atoms are added or removed randomly to generate point defects. For point defects, three types of point defects can decrease the tensile strength containing yield stress and strain of Fe samples. In addition, the tensile strength decreases with the increase of point defect concentration. With the same defect concentration, interstitials decrease the yield stress the most seriously compared with the vacancies and Frenkel pairs. Apart from that, the morphology and evolution of the microstructure of Fe with point defects are also investigated under tension. Compared with the perfect crystal, the generation of dislocation decreases the tensile strength dramatically. For sample with interstitials, interstitial clusters form and evolve in dislocations loops finally. For sample with vacancis, vacancy may aggregate together and vacancy clusters form as a result, which is seen as precursors of dislocation loop. Notably, the results are meaningful to understand the effects of point defects on tensile strength of BCC-Fe.
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Gao, Huang, et Gary J. Cheng. « A Dislocation Dynamics Based Constitutive Model and Experimental Validations by 3D Microscale Laser Dynamic Forming of Metallic Thin Films ». Dans ASME 2010 International Manufacturing Science and Engineering Conference. ASMEDC, 2010. http://dx.doi.org/10.1115/msec2010-34300.
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Microscale Laser Dynamic Forming (μLDF) shows great potential in fabricating the robust and high-aspect-ratio metallic microcomponents by the high speed plasma shockwave. Experiments revealed that strain rate and sample size play important roles in determining the final results of μLDF. To further understand the deformation behavior, we develop a constitutive model integrating size effects and ultrahigh strain rate effects to predict the ultimate plastic deformations. To derive this model, 3-D Discrete Dislocation Dynamics (DDD) simulations are first set up to investigate the dislocation evolutions and the dynamic responses during shockwave propagation. It is observed that there exist three dynamic stages during deformation process, and the initial strain hardening rate in Stage II increases with strain rate. The simulation also reveals that stain softening occurs only for the smaller cell size due to two competing mechanisms. In addition, the simulation predicts that the flow stress and yield strength increase with the strain rate and decrease with cell size. The modified mechanical threshold stress (MTS) model integrating these effects is implemented in Abaqus/Explicit and predicts the deformation depth and thickness variations in good agreement with the experimental results.
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Déprés, C., G. V. Prasad Reddy, L. Tabourot, R. Sandhya et S. Sankaran. « First Steps of Crack Initiation and Propagation in Fatigue of FCC Crystals Studied by Dislocation Dynamics ». Dans ASME 2012 11th Biennial Conference on Engineering Systems Design and Analysis. American Society of Mechanical Engineers, 2012. http://dx.doi.org/10.1115/esda2012-82942.
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3D discrete dislocation dynamic (DDD) simulations are performed to simulate stage-I fatigue crack initiation and propagation along the surface, in the primary grain and its neighbouring grain, in 316L stainless steel. The scenario of crack propagation in primary grain and the evolution of dislocation structure ahead of crack tip are discussed, and in addition crack tip sliding displacement is estimated. Probable mechanisms of crack propagation from primary grain to neighbouring grain are evaluated. In this process, surface relief in the neighbouring-grain under the influence of crack stress field in the primary grain is studied for varying neighbouring-grain orientations. An enhanced evolution of surface extrusions in the neighbouring grain, are observed in the presence of heterogeneous stress field (i.e., in the presence of crack in the primary grain), compared to that in the case of homogeneous stress field. In addition, influence of crack stress field on prior cyclic-deformed substructure is presented.
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WANG, G. S. « PERFORMANCE OF A TANTALUM FOR APPLICATIONS OF EXPLOSIVELY FORMED PROJECTILES ». Dans 32ND INTERNATIONAL SYMPOSIUM ON BALLISTICS. Destech Publications, Inc., 2022. http://dx.doi.org/10.12783/ballistics22/36161.
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The deformation rate of explosively formed projectiles (EFPs) are extremely high, at the strain rate orders of more than a half million strain per second. The deformation occurs often at the magnitude of several hundred percent of strain, and the adiabatic heat is considerable. Challenges for developing a material model suitable for simulations of the projectile lies in the limitation of material testing where the strain rates used often are several orders of magnitude lower than what occurs in EFP projectiles. In this work, an effort is made to establish a dislocation thermal dynamics based model for a batch of tantalum to characterise its material behaviour at extreme strain rate, magnitude, and temperature, based on conventional material test results for both room and elevated temperatures at moderate strain rates. The validation of numerical simulations with this model for the EFP test results shows that there is a potential with the theoretical model based on the dislocation movement for such applications.
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Tan, Jingye, Kathryn Maupin, Shuai Shao et Danial Faghihi. « A Bayesian Machine Learning Framework for Selection of the Strain Gradient Plasticity Multiscale Model ». Dans ASME 2021 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2021. http://dx.doi.org/10.1115/imece2021-69693.
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Abstract A class of sequential multiscale models investigated in this study consists of discrete dislocation dynamics (DDD) simulations and continuum strain gradient plasticity (SGP) models to simulate the size effect in plastic deformation of metallic micropillars. The high-fidelity DDD explicitly simulates the microstructural (dislocation) interactions. These simulations account for the effect of dislocation densities and their spatial distributions on plastic deformation. The continuum SGP captures the size-dependent plasticity in micropillars using two length parameters. The main challenge in predictive DDD-SGP multi-scale modeling is selecting the proper constitutive relations for the SGP model, which is necessitated by the uncertainty in computational prediction due to DDD’s microstructural randomness. This contribution addresses these challenges using a Bayesian learning and model selection framework. A family of SGP models with different fidelities and complexities is constructed using various constitutive relation assumptions. The parameters of the SGP models are then learned from a set of training data furnished by the DDD simulations of micropillars. Bayesian learning allows the assessment of the credibility of plastic deformation prediction by characterizing the microstructural variability and the uncertainty in training data. Additionally, the family of the possible SGP models is subjected to a Bayesian model selection to pick the model that adequately explains the DDD training data. The framework proposed in this study enables learning the physics-based multiscale model from uncertain observational data and determining the optimal computational model for predicting complex physical phenomena, i.e., size effect in plastic deformation of micropillars.
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Oyinbo, Sunday Temitope, et Tien-Chien Jen. « Molecular Dynamics Simulation of the Effect of Hydrogen on the Interaction Between Dislocations in Alpha-Iron ». Dans ASME 2022 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2022. http://dx.doi.org/10.1115/imece2022-94722.
Texte intégralRésumé :
Abstract In this study, we use extensive molecular dynamics (MD) calculations based on a highly-accurate interatomic potential to examine how hydrogen atoms impact the mechanisms behind the mobilities of edge and screw dislocations in alpha-iron (α-Fe) at a temperature ranging from 300 K to 500 K. The dislocation mobility in α-Fe is shown to be temperature and hydrogen concentration-dependent in this MD investigation. It is demonstrated from the results that hydrogen impurities that are efficient in locking dislocations exist in the form of complexes that are scattered discretely along the dislocation line and that these complexes operate as extremely effective impediments to the mobility of dislocations. The hydrogen impact on the edge dislocation motion from the dislocation velocities versus shear stress reveals that the movement of edge dislocations in α-Fe with hydrogen is much damped as the hydrogen concentration increases. Furthermore, the motion of screw dislocations in the α-Fe is by the process of kink-pair nucleation and migration. according to the simulation results, the locking mechanism of the cross-slip seen along the dislocation path is due to the strong-feature energy landscape and inherent energy fluctuation in the system, resulting in jogs formation.
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Tan, E. H., et L. Z. Sun. « Dislocation Dynamics Modeling for Yield Strength of Nanoscale Film Heterostructures ». Dans ASME 2005 International Mechanical Engineering Congress and Exposition. ASMEDC, 2005. http://dx.doi.org/10.1115/imece2005-79222.
Texte intégralRésumé :
A novel dislocation dynamics framework is developed to simulate dislocation evolutions in thin film heterostructures at nanoscale. It is based on 3-D dislocation motion together with its physical background by adding the solid viscous effect. As the numerical simulation results demonstrate, this new model completely solves a long-standing paradoxical phenomenon with which the simulation results were dependent on dislocation-segment lengths in the classical discrete dislocation dynamics theory. The proposed model is applied to simulate the effect of dislocations on the mechanical performance of thin films. The interactions among the dislocation loop, free surface and interface are rigorously computed by decomposing this complicated problem into two relatively simple sub-problems. This model is allowed to determine the critical thickness of thin films for a surface loop to nucleate and to simulate how a surface loop evolves into two threading dislocations. Furthermore, the relationship between the film thickness and yield strength is constructed and compared with the conventional Hall-Petch relation.
Rapports d'organisations sur le sujet "Dislocation Dynamics Simulations"
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Zhou, Caizhi. Dislocation dynamics simulations of plasticity at small scales. Office of Scientific and Technical Information (OSTI), janvier 2010. http://dx.doi.org/10.2172/1037981.
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Cazamias, J., D. Lassila, M. Shehadeh et H. Zbib. A Report on the use of Weak-Shock Wave Profiles and 3-D Dislocation Dynamics Simulations for Validation of Dislocation Multiplication and Mobility in the Phonon Drag Regime. Office of Scientific and Technical Information (OSTI), février 2004. http://dx.doi.org/10.2172/15013922.
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Tang, M., G. Hommes, S. Aubry et A. Arsenlis. ParaDiS-FEM dislocation dynamics simulation code primer. Office of Scientific and Technical Information (OSTI), septembre 2011. http://dx.doi.org/10.2172/1037843.
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Lassila, D. H. Dislocation dynamics : simulation of plastic flow of bcc metals. Office of Scientific and Technical Information (OSTI), février 2001. http://dx.doi.org/10.2172/15005437.
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Kleiner, Kevin Gordon. Modeling and Simulating Dislocation Dynamics Near Sound Speeds in Cubic Crystals. Office of Scientific and Technical Information (OSTI), juillet 2019. http://dx.doi.org/10.2172/1545735.
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