Atomistic Modeling Of Dislocation Motion At Experimental Time Scales

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Atomistic Modeling of Dislocation Motion at Experimental Time-scales

Author : Sepehr Saroukhani
Publisher :
ISBN 13 :
Total Pages : 308 pages
Book Rating : 4.:/5 (11 download)

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Book Synopsis Atomistic Modeling of Dislocation Motion at Experimental Time-scales by : Sepehr Saroukhani

Download or read book Atomistic Modeling of Dislocation Motion at Experimental Time-scales written by Sepehr Saroukhani and published by . This book was released on 2017 with total page 308 pages. Available in PDF, EPUB and Kindle. Book excerpt: An accurate prediction of the rate of dislocation motion is key to the fidelity of multi-scale plasticity models of metals and alloys. In this dissertation, atomistic simulations and rate theories based on statistical mechanics are used to accurately predict the rate of three main dislocation motion mechanisms: 1) Dislocation motion across precipitates 2) Dislocation motion through a field of obstacles 3) Dislocation motion via kink-pair nucleation For these mechanisms, the accuracy of both conventional and modern rate theories is examined by comparing their predictions to benchmarks obtained from MD simulations. Different variants of the Harmonic Transition State Theory, as the most common rate theory in the literature, are found to provide grossly inaccurate predictions for all three problems. It is shown that the inaccuracy of these approaches stems from their assumptions about the entropy barrier. The original version of HTST estimates the entropy barrier by the harmonic vibrational entropy, which is found to be inaccurate for all three problems due to thermal softening. Other versions of HTST based on simple estimates of the attempt frequency consider smaller values for the vibrational entropy, and hence provide even more inaccurate predictions. Furthermore, all variants of HTST neglect the configurational entropy, which turns out to be significant for the kink-pair nucleation problem. The utility of the Finite Temperature string method for computing a reaction coordinate and a free energy profile was examined for the three problems. The method provides an accurate reaction channel for dislocation-obstacle interactions but fails to provide a reasonable free energy profile. The reasons are investigated and discussed in the first paper presented in this dissertation. The original version of the method fails to provide a reaction channel for the kink-pair nucleation problem because it has not been designed for problems with multiple reaction channels. To address this issue, a modification to the approach based on physical intuitions about the problem is proposed and is shown to be effective. Different variants of the Transition Interface Sampling approach, as a modern rate theory, are found to be capable of accurately predicting the rate for all three problems. TIS and its Path Swapping version are found to be effective for dislocation-precipitate interactions. The method is also accurate in the jerky motion regime of dislocation motion through a field of solutes. For the smooth motion regime, however, the Partial Path version of TIS -- designed for diffusive barriers -- had to be used. In order to provide accurate predictions for the kink-pair nucleation problem, TIS had to be modified based on physical intuitions about the problem because the method has not been designed for problems with multiple reaction channels such as the glide of screw dislocations in BCC transition metals. The performance of the Meyer-Neldel (MN) rule, as the most common entropy estimation approach in material mechanics, is examined for the three problems. It is shown that the method accurately predicts the entropy barrier for dislocation-precipitate interactions but fails to fully explain the entropy barrier for the other two problems. The assumptions and the...

Improving Atomistic Simulations to Predict Deformation and Fracture

Author : Kristopher Learion Baker
Publisher :
ISBN 13 :
Total Pages : 150 pages
Book Rating : 4.:/5 (826 download)

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Book Synopsis Improving Atomistic Simulations to Predict Deformation and Fracture by : Kristopher Learion Baker

Download or read book Improving Atomistic Simulations to Predict Deformation and Fracture written by Kristopher Learion Baker and published by . This book was released on 2012 with total page 150 pages. Available in PDF, EPUB and Kindle. Book excerpt: Atomistic simulations can illuminate detailed mechanisms of brittle and ductile fracture and plasticity. However, there are many limitations to these simulations like short timescales, small spatial scales, and limitations of the discretization. Using molecular dynamics (MD) and multiscale methods, adaptations can be made to allow MD to answer problems relevant to engineers. In the first of three examples, MD is adapted to simulate brittle fracture by changing the discretization and allowing permanent damage between particles. By changing the discretization, specific mechanisms inherent to MD can be suppressed to allow accurate, macroscopic simulations of dynamic fragmentation of brittle materials. Second, the timescale available to MD is extended in a concurrent multiscale method (CADD) combined with accelerated MD. This combined approach allows for microseconds of simulation time at experimentally achievable loading rates. The method is applied to crack opening in aluminum alloys, and the effect of the loading rate on crack growth mechanisms is observed. From the results, it is clear that crack growth mechanisms depend greatly on the rate of the far-field loading. Third, the effect of aging on fatigue crack growth is studied by varying the resistance to dislocation motion in the dislocation dynamics region of CADD. Only in a multiscale simulation like CADD, can dislocation pileups reaching microns into the material interact with the atomic-scale mechanisms at a crack tip. The results of the simulations indicated that increasing the friction force raises the fatigue crack threshold. Also, a transition from stage I fatigue crack growth to stage II fatigue crack growth occurs by dislocations shielding dislocation nucleation on the primary slip plane. These observations support the conclusion that the fatigue crack growth threshold is controlled by the spacing between obstacles to dislocation glide, which is consistent with experimental observations.

Stochastic Dynamics of Crystal Defects

Author : Thomas D Swinburne
Publisher : Springer
ISBN 13 : 3319200194
Total Pages : 110 pages
Book Rating : 4.3/5 (192 download)

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Book Synopsis Stochastic Dynamics of Crystal Defects by : Thomas D Swinburne

Download or read book Stochastic Dynamics of Crystal Defects written by Thomas D Swinburne and published by Springer. This book was released on 2015-07-13 with total page 110 pages. Available in PDF, EPUB and Kindle. Book excerpt: This thesis is concerned with establishing a rigorous, modern theory of the stochastic and dissipative forces on crystal defects, which remain poorly understood despite their importance in any temperature dependent micro-structural process such as the ductile to brittle transition or irradiation damage. The author first uses novel molecular dynamics simulations to parameterise an efficient, stochastic and discrete dislocation model that allows access to experimental time and length scales. Simulated trajectories are in excellent agreement with experiment. The author also applies modern methods of multiscale analysis to extract novel bounds on the transport properties of these many body systems. Despite their successes in coarse graining, existing theories are found unable to explain stochastic defect dynamics. To resolve this, the author defines crystal defects through projection operators, without any recourse to elasticity. By rigorous dimensional reduction, explicit analytical forms are derived for the stochastic forces acting on crystal defects, allowing new quantitative insight into the role of thermal fluctuations in crystal plasticity.

Dislocations, Mesoscale Simulations and Plastic Flow

Author : Ladislas Kubin
Publisher : OUP Oxford
ISBN 13 : 0191664545
Total Pages : 320 pages
Book Rating : 4.1/5 (916 download)

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Book Synopsis Dislocations, Mesoscale Simulations and Plastic Flow by : Ladislas Kubin

Download or read book Dislocations, Mesoscale Simulations and Plastic Flow written by Ladislas Kubin and published by OUP Oxford. This book was released on 2013-04-18 with total page 320 pages. Available in PDF, EPUB and Kindle. Book excerpt: In the past twenty years, new experimental approaches, improved models and progress in simulation techniques brought new insights into long-standing issues concerning dislocation-based plasticity in crystalline materials. During this period, three-dimensional dislocation dynamics simulations appeared and reached maturity. Their objectives are to unravel the relation between individual and collective dislocation processes at the mesoscale, to establish connections with atom-scale studies of dislocation core properties and to bridge, in combination with modelling, the gap between defect properties and phenomenological continuum models for plastic flow. Dislocation dynamics simulations are becoming accessible to a wide range of users. This book presents to students and researchers in materials science and mechanical engineering a comprehensive coverage of the physical body of knowledge on which they are based. It includes classical studies, which are too often ignored, recent experimental and theoretical advances, as well as a discussion of selected applications on various topics.

Handbook of Materials Modeling

Author : Sidney Yip
Publisher : Springer Science & Business Media
ISBN 13 : 1402032862
Total Pages : 2903 pages
Book Rating : 4.4/5 (2 download)

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Book Synopsis Handbook of Materials Modeling by : Sidney Yip

Download or read book Handbook of Materials Modeling written by Sidney Yip and published by Springer Science & Business Media. This book was released on 2007-11-17 with total page 2903 pages. Available in PDF, EPUB and Kindle. Book excerpt: The first reference of its kind in the rapidly emerging field of computational approachs to materials research, this is a compendium of perspective-providing and topical articles written to inform students and non-specialists of the current status and capabilities of modelling and simulation. From the standpoint of methodology, the development follows a multiscale approach with emphasis on electronic-structure, atomistic, and mesoscale methods, as well as mathematical analysis and rate processes. Basic models are treated across traditional disciplines, not only in the discussion of methods but also in chapters on crystal defects, microstructure, fluids, polymers and soft matter. Written by authors who are actively participating in the current development, this collection of 150 articles has the breadth and depth to be a major contributor toward defining the field of computational materials. In addition, there are 40 commentaries by highly respected researchers, presenting various views that should interest the future generations of the community. Subject Editors: Martin Bazant, MIT; Bruce Boghosian, Tufts University; Richard Catlow, Royal Institution; Long-Qing Chen, Pennsylvania State University; William Curtin, Brown University; Tomas Diaz de la Rubia, Lawrence Livermore National Laboratory; Nicolas Hadjiconstantinou, MIT; Mark F. Horstemeyer, Mississippi State University; Efthimios Kaxiras, Harvard University; L. Mahadevan, Harvard University; Dimitrios Maroudas, University of Massachusetts; Nicola Marzari, MIT; Horia Metiu, University of California Santa Barbara; Gregory C. Rutledge, MIT; David J. Srolovitz, Princeton University; Bernhardt L. Trout, MIT; Dieter Wolf, Argonne National Laboratory.

Atomistic Modeling of Materials Failure

Author : Markus J. Buehler
Publisher : Springer Science & Business Media
ISBN 13 : 0387764267
Total Pages : 547 pages
Book Rating : 4.3/5 (877 download)

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Book Synopsis Atomistic Modeling of Materials Failure by : Markus J. Buehler

Download or read book Atomistic Modeling of Materials Failure written by Markus J. Buehler and published by Springer Science & Business Media. This book was released on 2008-08-07 with total page 547 pages. Available in PDF, EPUB and Kindle. Book excerpt: This is an introduction to molecular and atomistic modeling techniques applied to fracture and deformation of solids, focusing on a variety of brittle, ductile, geometrically confined and biological materials. The overview includes computational methods and techniques operating at the atomic scale, and describes how these techniques can be used to model cracks and other deformation mechanisms. The book aims to make new molecular modeling techniques available to a wider community.

Dislocations in Solids

Author : Frank R.N. Nabarro
Publisher : Elsevier
ISBN 13 : 9780444514837
Total Pages : 668 pages
Book Rating : 4.5/5 (148 download)

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Book Synopsis Dislocations in Solids by : Frank R.N. Nabarro

Download or read book Dislocations in Solids written by Frank R.N. Nabarro and published by Elsevier. This book was released on 2004-12 with total page 668 pages. Available in PDF, EPUB and Kindle. Book excerpt: This is the first volume to appear under the joint editorship of J.P. Hirth and F.R.N. Nabarro. While Volume 11 concentrated on the single topic of dislocations and work hardening, the present volume spreads over the whole range of the study of dislocations from the application by Kléman and his colleagues of homotopy theory to classifying the line and point defects of mesomorphic phases to Chaudhri's account of the experimental observations of dislocations formed around indentations. Chapter 64, by Cai, Bulatove, Chang, Li and Yip, discusses the influence of the structure of the core of a dislocation on its mobility. The power of modern computation allows this topic to be treated from the first principles of electron theory, and with empirical potentials for more complicated problems. Advances in electron microscopy allow these theoretical predictions to be tested. In Chapter 65, Xu analyzes the emission of dislocations from the tip of a crack and its influence on the brittle to ductile transition. Again, the treatment is predominantly theoretical, but it is consistently related to the very practical example of alpha iron. In a dazzling interplay of experiment and abstract mathematics, Kléman, Lavrentovich and Nastishin analyze the line and point structural defects of the many mesomorphic phases which have become known in recent years. Chapter 67, by Coupeau, Girard and Rabier, is essentially experimental. It shows how the various modern techniques of scanning probe microscopy can be used to study dislocations and their interaction with the free surface. Chapter 68, by Mitchell and Heuer, considers the complex dislocations that can form in ceramic crystals on the basis of observations by transmission electron microscopy and presents mechanistic models for the motion of the dislocations in various temperature regimes. While the underlying aim of the study of dislocations in energetic crystals by Armstrong and Elban in Chapter 69 is to understand the role of dislocations in the process of detonation, it has the wider interest of studying dislocations in molecular crystals which are ``elastically soft, plastically hard, and brittle''. Chaudhri in Chapter 70 discusses the role of dislocations in indentation processes, largely on the basis of the elastic analysis by E.H. Yoffe. The special case of nanoindentations is treated only briefly.

Dislocations in Solids

Author :
Publisher : Elsevier
ISBN 13 : 0080472540
Total Pages : 603 pages
Book Rating : 4.0/5 (84 download)

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Book Synopsis Dislocations in Solids by :

Download or read book Dislocations in Solids written by and published by Elsevier. This book was released on 2004-08-05 with total page 603 pages. Available in PDF, EPUB and Kindle. Book excerpt: This is the first volume to appear under the joint editorship of J.P. Hirth and F.R.N. Nabarro. While Volume 11 concentrated on the single topic of dislocations and work hardening, the present volume spreads over the whole range of the study of dislocations from the application by Kléman and his colleagues of homotopy theory to classifying the line and point defects of mesomorphic phases to Chaudhri's account of the experimental observations of dislocations formed around indentations.Chapter 64, by Cai, Bulatove, Chang, Li and Yip, discusses the influence of the structure of the core of a dislocation on its mobility. The power of modern computation allows this topic to be treated from the first principles of electron theory, and with empirical potentials for more complicated problems. Advances in electron microscopy allow these theoretical predictions to be tested.In Chapter 65, Xu analyzes the emission of dislocations from the tip of a crack and its influence on the brittle to ductile transition. Again, the treatment is predominantly theoretical, but it is consistently related to the very practical example of alpha iron.In a dazzling interplay of experiment and abstract mathematics, Kléman, Lavrentovich and Nastishin analyze the line and point structural defects of the many mesomorphic phases which have become known in recent years.Chapter 67, by Coupeau, Girard and Rabier, is essentially experimental. It shows how the various modern techniques of scanning probe microscopy can be used to study dislocations and their interaction with the free surface.Chapter 68, by Mitchell and Heuer, considers the complex dislocations that can form in ceramic crystals on the basis of observations by transmission electron microscopy and presents mechanistic models for the motion of the dislocations in various temperature regimes.While the underlying aim of the study of dislocations in energetic crystals by Armstrong and Elban in Chapter 69 is to understand the role of dislocations in the process of detonation, it has the wider interest of studying dislocations in molecular crystals which are ``elastically soft, plastically hard, and brittle''.Chaudhri in Chapter 70 discusses the role of dislocations in indentation processes, largely on the basis of the elastic analysis by E.H. Yoffe. The special case of nanoindentations is treated only briefly.

Thermally Activated Mechanisms in Crystal Plasticity

Author : D. Caillard
Publisher : Elsevier
ISBN 13 : 0080542786
Total Pages : 453 pages
Book Rating : 4.0/5 (85 download)

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Book Synopsis Thermally Activated Mechanisms in Crystal Plasticity by : D. Caillard

Download or read book Thermally Activated Mechanisms in Crystal Plasticity written by D. Caillard and published by Elsevier. This book was released on 2003-09-08 with total page 453 pages. Available in PDF, EPUB and Kindle. Book excerpt: KEY FEATURES: A unified, fundamental and quantitative resource. The result of 5 years of investigation from researchers around the world New data from a range of new techniques, including synchrotron radiation X-ray topography provide safer and surer methods of identifying deformation mechanisms Informing the future direction of research in intermediate and high temperature processes by providing original treatment of dislocation climb DESCRIPTION: Thermally Activated Mechanisms in Crystal Plasticity is a unified, quantitative and fundamental resource for material scientists investigating the strength of metallic materials of various structures at extreme temperatures. Crystal plasticity is usually controlled by a limited number of elementary dislocation mechanisms, even in complex structures. Those which determine dislocation mobility and how it changes under the influence of stress and temperature are of key importance for understanding and predicting the strength of materials. The authors describe in a consistent way a variety of thermally activated microscopic mechanisms of dislocation mobility in a range of crystals. The principles of the mechanisms and equations of dislocation motion are revisited and new ones are proposed. These describe mostly friction forces on dislocations such as the lattice resistance to glide or those due to sessile cores, as well as dislocation cross-slip and climb. They are critically assessed by comparison with the best available experimental results of microstructural characterization, in situ straining experiments under an electron or a synchrotron beam, as well as accurate transient mechanical tests such as stress relaxation experiments. Some recent attempts at atomistic modeling of dislocation cores under stress and temperature are also considered since they offer a complementary description of core transformations and associated energy barriers. In addition to offering guidance and assistance for further experimentation, the book indicates new ways to extend the body of data in particular areas such as lattice resistance to glide.

Multiscale Phenomena in Plasticity: From Experiments to Phenomenology, Modelling and Materials Engineering

Author : Joël Lépinoux
Publisher : Springer Science & Business Media
ISBN 13 : 9401140480
Total Pages : 540 pages
Book Rating : 4.4/5 (11 download)

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Book Synopsis Multiscale Phenomena in Plasticity: From Experiments to Phenomenology, Modelling and Materials Engineering by : Joël Lépinoux

Download or read book Multiscale Phenomena in Plasticity: From Experiments to Phenomenology, Modelling and Materials Engineering written by Joël Lépinoux and published by Springer Science & Business Media. This book was released on 2012-12-06 with total page 540 pages. Available in PDF, EPUB and Kindle. Book excerpt: A profusion of research and results on the mechanical behaviour of crystalline solids has followed the discovery of dislocations in the early thirties. This trend has been enhanced by the development of powerful experimental techniques. particularly X ray diffraction. transmission and scanning electron microscopy. microanalysis. The technological advancement has given rise to the study of various and complex materials. not to speak of those recently invented. whose mechanical properties need to be mastered. either for their lise as structural materials. or more simply for detenllining their fonnability processes. As is often the case this fast growth has been diverted both by the burial of early fundamental results which are rediscovered more or less accurately. and by the too fast publication of inaccurate results. which propagate widely. and are accepted without criticism. Examples of these statements abound. and will not be quoted here for the sake of dispassionateness. Understanding the mechanical properties of materials implies the use of various experimental techniques. combined with a good theoretical knowledge of elasticity. thermodynamics and solid state physics. The recent development of various computer techniques (simulation. ab initio calculations) has added to the difficulty of gathering the experimental information. and mastering the theoretical understanding. No laboratory is equipped with all the possible experimental settings. almost no scientist masters all this theoretical kno\vledge. Therefore. cooperation between scientists is needed more than even before.

Atomistic Modeling of Dislocation-interface Interactions

Author :
Publisher :
ISBN 13 :
Total Pages : pages
Book Rating : 4.:/5 (16 download)

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Book Synopsis Atomistic Modeling of Dislocation-interface Interactions by :

Download or read book Atomistic Modeling of Dislocation-interface Interactions written by and published by . This book was released on 2011 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Using atomic scale models and interface defect theory, we first classify interface structures into a few types with respect to geometrical factors, then study the interfacial shear response and further simulate the dislocation-interface interactions using molecular dynamics. The results show that the atomic scale structural characteristics of both heterophases and homophases interfaces play a crucial role in (i) their mechanical responses and (ii) the ability of incoming lattice dislocations to transmit across them.

Comprehensive Nuclear Materials

Author :
Publisher : Elsevier
ISBN 13 : 0081028660
Total Pages : 4871 pages
Book Rating : 4.0/5 (81 download)

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Book Synopsis Comprehensive Nuclear Materials by :

Download or read book Comprehensive Nuclear Materials written by and published by Elsevier. This book was released on 2020-07-22 with total page 4871 pages. Available in PDF, EPUB and Kindle. Book excerpt: Materials in a nuclear environment are exposed to extreme conditions of radiation, temperature and/or corrosion, and in many cases the combination of these makes the material behavior very different from conventional materials. This is evident for the four major technological challenges the nuclear technology domain is facing currently: (i) long-term operation of existing Generation II nuclear power plants, (ii) the design of the next generation reactors (Generation IV), (iii) the construction of the ITER fusion reactor in Cadarache (France), (iv) and the intermediate and final disposal of nuclear waste. In order to address these challenges, engineers and designers need to know the properties of a wide variety of materials under these conditions and to understand the underlying processes affecting changes in their behavior, in order to assess their performance and to determine the limits of operation. Comprehensive Nuclear Materials, Second Edition, Seven Volume Set provides broad ranging, validated summaries of all the major topics in the field of nuclear material research for fission as well as fusion reactor systems. Attention is given to the fundamental scientific aspects of nuclear materials: fuel and structural materials for fission reactors, waste materials, and materials for fusion reactors. The articles are written at a level that allows undergraduate students to understand the material, while providing active researchers with a ready reference resource of information. Most of the chapters from the first Edition have been revised and updated and a significant number of new topics are covered in completely new material. During the ten years between the two editions, the challenge for applications of nuclear materials has been significantly impacted by world events, public awareness, and technological innovation. Materials play a key role as enablers of new technologies, and we trust that this new edition of Comprehensive Nuclear Materials has captured the key recent developments. Critically reviews the major classes and functions of materials, supporting the selection, assessment, validation and engineering of materials in extreme nuclear environments Comprehensive resource for up-to-date and authoritative information which is not always available elsewhere, even in journals Provides an in-depth treatment of materials modeling and simulation, with a specific focus on nuclear issues Serves as an excellent entry point for students and researchers new to the field

Atomistic Simulation of Anistropic Crystal Structures at Nanoscale

Author : Jia Fu
Publisher : BoD – Books on Demand
ISBN 13 : 1838802010
Total Pages : 180 pages
Book Rating : 4.8/5 (388 download)

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Book Synopsis Atomistic Simulation of Anistropic Crystal Structures at Nanoscale by : Jia Fu

Download or read book Atomistic Simulation of Anistropic Crystal Structures at Nanoscale written by Jia Fu and published by BoD – Books on Demand. This book was released on 2019-05-10 with total page 180 pages. Available in PDF, EPUB and Kindle. Book excerpt: Multiscale simulations of atomistic/continuum coupling in computational materials science, where the scale expands from macro-/micro- to nanoscale, has become a hot research topic. These small units, usually nanostructures, are commonly anisotropic. The development of molecular modeling tools to describe and predict the mechanical properties of structures reveals an undeniable practical importance. Typical anisotropic structures (e.g. cubic, hexagonal, monoclinic) using DFT, MD, and atomic finite element methods are especially interesting, according to the modeling requirement of upscaling structures. It therefore connects nanoscale modeling and continuous patterns of deformation behavior by identifying relevant parameters from smaller to larger scales. These methodologies have the prospect of significant applications. I would like to recommend this book to both beginners and experienced researchers.

Atomistic Simulation of Dislocation Motion and Interaction with Crack Tips and Voids

Author : Erik Bitzek
Publisher :
ISBN 13 : 9783832267704
Total Pages : 227 pages
Book Rating : 4.2/5 (677 download)

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Book Synopsis Atomistic Simulation of Dislocation Motion and Interaction with Crack Tips and Voids by : Erik Bitzek

Download or read book Atomistic Simulation of Dislocation Motion and Interaction with Crack Tips and Voids written by Erik Bitzek and published by . This book was released on 2007 with total page 227 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Applied Computational Materials Modeling

Author : Guillermo Bozzolo
Publisher : Springer Science & Business Media
ISBN 13 : 0387345655
Total Pages : 502 pages
Book Rating : 4.3/5 (873 download)

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Book Synopsis Applied Computational Materials Modeling by : Guillermo Bozzolo

Download or read book Applied Computational Materials Modeling written by Guillermo Bozzolo and published by Springer Science & Business Media. This book was released on 2007-12-19 with total page 502 pages. Available in PDF, EPUB and Kindle. Book excerpt: The scope of this book is to identify and emphasize the successful link between computational materials modeling as a simulation and design tool and its synergistic application to experimental research and alloy development. The book provides a more balanced perspective of the role that computational modeling can play in every day research and development efforts. Each chapter describes one or more particular computational tool and how they are best used.

Atomistic and Mesoscale Modeling of Dislocation Mobility

Author : Wei Cai
Publisher :
ISBN 13 :
Total Pages : 321 pages
Book Rating : 4.:/5 (497 download)

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Book Synopsis Atomistic and Mesoscale Modeling of Dislocation Mobility by : Wei Cai

Download or read book Atomistic and Mesoscale Modeling of Dislocation Mobility written by Wei Cai and published by . This book was released on 2001 with total page 321 pages. Available in PDF, EPUB and Kindle. Book excerpt: (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.

Dislocation Dynamics and Plasticity

Author : Taira Suzuki
Publisher : Springer Science & Business Media
ISBN 13 : 364275774X
Total Pages : 237 pages
Book Rating : 4.6/5 (427 download)

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Book Synopsis Dislocation Dynamics and Plasticity by : Taira Suzuki

Download or read book Dislocation Dynamics and Plasticity written by Taira Suzuki and published by Springer Science & Business Media. This book was released on 2013-03-07 with total page 237 pages. Available in PDF, EPUB and Kindle. Book excerpt: In the 1950s the direct observation of dislocations became possible, stimulat ing the interest of many research workers in the dynamics of dislocations. This led to major contributions to the understanding of the plasticity of various crys talline materials. During this time the study of metals and alloys of fcc and hcp structures developed remarkably. In particular, the discovery of the so-called in ertial effect caused by the electron and phonon frictional forces greatly influenced the quantitative understanding of the strength of these metallic materials. Statis tical studies of dislocations moving through random arrays of point obstacles played an important role in the above advances. These topics are described in Chaps. 2-4. Metals and alloys with bcc structure have large Peierls forces compared to those with fcc structure. The reasons for the delay in studying substances with bcc structure were mostly difficulties connected with the purification techniques and with microscopic studies of the dislocation core. In the 1970s, these difficulties were largely overcome by developments in experimental techniques and computer physics. Studies of dislocations in ionic and covalent bonding materials with large Peierls forces provided infonnation about the core structures of dislocations and their electronic interactions with charged particles. These are the main subjects in Chaps. 5-7.