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Dislocation Mechanics Of Metal Plasticity And Fracturing
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Book Synopsis Dislocation Mechanics of Metal Plasticity and Fracturing by : Ronald W. Armstrong
Download or read book Dislocation Mechanics of Metal Plasticity and Fracturing written by Ronald W. Armstrong and published by MDPI. This book was released on 2020-11-03 with total page 188 pages. Available in PDF, EPUB and Kindle. Book excerpt: The modern understanding of metal plasticity and fracturing began about 100 years ago, with pioneering work; first, on crack-induced fracturing by Griffith and, second, with the invention of dislocation-enhanced crystal plasticity by Taylor, Orowan and Polanyi. The modern counterparts are fracture mechanics, as invented by Irwin, and dislocation mechanics, as initiated in pioneering work by Cottrell. No less important was the breakthrough development of optical characterization of sectioned polycrystalline metal microstructures started by Sorby in the late 19th century and leading eventually to modern optical, x-ray and electron microscopy methods for assessments of crystal fracture surfaces, via fractography, and particularly of x-ray and electron microscopy techniques applied to quantitative characterizations of internal dislocation behaviors. A major current effort is to match computational simulations of metal deformation/fracturing behaviors with experimental measurements made over extended ranges of microstructures and over varying external conditions of stress-state, temperature and loading rate. The relation of such simulations to the development of constitutive equations for a hoped-for predictive description of material deformation/fracturing behaviors is an active topic of research. The present collection of articles provides a broad sampling of research accomplishments on the two subjects.
Book Synopsis Dislocation Mechanics of Metal Plasticity and Fracturing by : Ronald W. Armstrong
Download or read book Dislocation Mechanics of Metal Plasticity and Fracturing written by Ronald W. Armstrong and published by . This book was released on 2020 with total page 188 pages. Available in PDF, EPUB and Kindle. Book excerpt: The modern understanding of metal plasticity and fracturing began about 100 years ago, with pioneering work; first, on crack-induced fracturing by Griffith and, second, with the invention of dislocation-enhanced crystal plasticity by Taylor, Orowan and Polanyi. The modern counterparts are fracture mechanics, as invented by Irwin, and dislocation mechanics, as initiated in pioneering work by Cottrell. No less important was the breakthrough development of optical characterization of sectioned polycrystalline metal microstructures started by Sorby in the late 19th century and leading eventually to modern optical, x-ray and electron microscopy methods for assessments of crystal fracture surfaces, via fractography, and particularly of x-ray and electron microscopy techniques applied to quantitative characterizations of internal dislocation behaviors. A major current effort is to match computational simulations of metal deformation/fracturing behaviors with experimental measurements made over extended ranges of microstructures and over varying external conditions of stress-state, temperature and loading rate. The relation of such simulations to the development of constitutive equations for a hoped-for predictive description of material deformation/fracturing behaviors is an active topic of research. The present collection of articles provides a broad sampling of research accomplishments on the two subjects.
Book Synopsis Fundamental Aspects of Dislocation Interactions by : G. Kostorz
Download or read book Fundamental Aspects of Dislocation Interactions written by G. Kostorz and published by Elsevier. This book was released on 2013-09-03 with total page 471 pages. Available in PDF, EPUB and Kindle. Book excerpt: Fundamental Aspects of Dislocation Interactions: Low-Energy Dislocation Structures III covers the papers presented at a European Research Conference on Plasticity of Materials-Fundamental Aspects of Dislocation Interactions: Low-Energy Dislocation Structures III, held on August 30-September 4, 1992 in Ascona, Switzerland. The book focuses on the processes, technologies, reactions, transformations, and approaches involved in dislocation interactions. The selection first offers information on work softening and Hall-Petch hardening in extruded mechanically alloyed alloys and dynamic origin of dislocation structures in deformed solids. Discussions focus on stress-strain behavior in relation to composition, structure, and annealing; comparison of stress-strain curves with work softening theory; sweeping and trapping mechanism; and model of dipolar wall structure formation. The text then ponders on plastic instabilities and their relation to fracture and dislocation and kink dynamics in f.c.c. metals studied by mechanical spectroscopy. The book takes a look at misfit dislocation generation mechanisms in heterostructures and evolution of dislocation structure on the interfaces associated with diffusionless phase transitions. Discussions focus on dislocation representation of a wall of elastic domains; equation of equilibrium of an elastic domain; transformation of dislocations; and theoretical and experimental background. The selection is a valuable reference for readers interested in dislocation interactions.
Book Synopsis Dislocation Modelling of Physical Systems by : M.F. Ashby
Download or read book Dislocation Modelling of Physical Systems written by M.F. Ashby and published by Elsevier. This book was released on 2013-10-22 with total page 598 pages. Available in PDF, EPUB and Kindle. Book excerpt: Dislocation Modelling of Physical Systems contains the Proceedings of the International Conference held at Gainesville, Florida, USA on June 22-27, 1980. The book emphasizes the growing interest in relating dislocation theoretic concepts to engineering problems. Topic areas chosen ranged from the fundamental, such as properties of single dislocations, to the more applied, such as fracture. The papers are grouped specifically based on the main topics they discuss. These topics include fracture; point defects and dislocations; structure dependence of mechanical behavior; properties of single dislocations; plasticity and geometry of deformation; internal friction effects; and boundaries.
Book Synopsis A Contribution to the Modeling of Metal Plasticity and Fracture by : Shyam Mohan Keralavarma
Download or read book A Contribution to the Modeling of Metal Plasticity and Fracture written by Shyam Mohan Keralavarma and published by . This book was released on 2012 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The objective of this dissertation is to further the understanding of inelastic behavior in metallic materials. Despite the increasing use of polymeric composites in aircraft structures, high specific strength metals continue to be used in key components such as airframe, fuselage, wings, landing gear and hot engine parts. Design of metallic structures subjected to thermomechanical extremes in aerospace, automotive and nuclear applications requires consideration of the plasticity, creep and fracture behavior of these materials. Consideration of inelasticity and damage processes is also important in the design of metallic components used in functional applications such as thin films, flexible electronics and micro electro mechanical systems. Fracture mechanics has been largely successful in modeling damage and failure phenomena in a host of engineering materials. In the context of ductile metals, the Gurson void growth model remains one of the most successful and widely used models. However, some well documented limitations of the model in quantitative prediction of the fracture strains and failure modes at low triaxialities may be traceable to the limited representation of the damage microstructure in the model. In the first part of this dissertation, we develop an extended continuum model of void growth that takes into account details of the material microstructure such as the texture of the plastically deforming matrix and the evolution of the void shape. The need for such an extension is motivated by a detailed investigation of the effects of the two types of anisotropy on the materials' effective response using finite element analysis. The model is derived using the Hill-Mandel homogenization theory and an approximate limit analysis of a porous representative volume element. Comparisons with several numerical studies are presented towards a partial validation of the analytical model. Inelastic phenomena such as plasticity and creep result from the collective behavior of a large number of nano and micro scale defects such as dislocations, vacancies and grain boundaries. Continuum models relate macroscopically observable quantities such as stress and strain by coarse graining the discrete defect microstructure. While continuum models provide a good approximation for the effective behavior of bulk materials, several deviations have been observed in experiments at small scales such as an intrinsic size dependence of the material strength. Discrete dislocation dynamics (DD) is a mesoscale method for obtaining the mechanical response of a material by direct simulation of the motion and interactions of dislocations. The model incorporates an intrinsic length scale in the dislocation Burgers vector and potentially allows for size dependent mechanical behavior to emerge naturally from the dynamics of the dislocation ensemble. In the second part of this dissertation, a simplified two dimensional DD model is employed to study several phenomena of practical interest such as strain hardening under homogeneous deformation, growth of microvoids in a crystalline matrix and creep of single crystals at elevated temperatures. These studies have been enabled by several recent enhancements to the existing two-dimensional DD framework described in Chapter V. The main contributions from this research are: (i) development of a fully anisotropic continuum model of void growth for use in ductile fracture simulations and (ii) enhancing the capabilities of an existing two-dimensional DD framework for large scale simulations in complex domains and at elevated temperatures.
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.
Book Synopsis Strain Gradient Plasticity-Based Modeling of Damage and Fracture by : Emilio Martínez Pañeda
Download or read book Strain Gradient Plasticity-Based Modeling of Damage and Fracture written by Emilio Martínez Pañeda and published by Springer. This book was released on 2017-08-23 with total page 166 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book provides a comprehensive introduction to numerical modeling of size effects in metal plasticity. The main classes of strain gradient plasticity formulations are described and efficiently implemented in the context of the finite element method. A robust numerical framework is presented and employed to investigate the role of strain gradients on structural integrity assessment. The results obtained reveal the need of incorporating the influence on geometrically necessary dislocations in the modeling of various damage mechanisms. Large gradients of plastic strain increase dislocation density, promoting strain hardening and elevating crack tip stresses. This stress elevation is quantified under both infinitesimal and finite deformation theories, rationalizing the experimental observation of cleavage fracture in the presence of significant plastic flow. Gradient-enhanced modeling of crack growth resistance, hydrogen diffusion and environmentally assisted cracking highlighted the relevance of an appropriate characterization of the mechanical response at the small scales involved in crack tip deformation. Particularly promising predictions are attained in the field of hydrogen embrittlement. The research has been conducted at the Universities of Cambridge, Oviedo, Luxembourg, and the Technical University of Denmark, in a collaborative effort to understand, model and optimize the mechanical response of engineering materials.
Book Synopsis Mathematical Theory of Dislocations and Fracture by : R. W. Lardner
Download or read book Mathematical Theory of Dislocations and Fracture written by R. W. Lardner and published by Toronto ; Buffalo : University of Toronto Press. This book was released on 1974 with total page 386 pages. Available in PDF, EPUB and Kindle. Book excerpt: Concise, logical, and mathematically rigorous, this introduction to the theory of dislocations is addressed primarily to students and researchers in the general areas of mechanics and applied mathematics. Its scope encompasses those aspects of dislocation theory which are closely related to the theories of elasticity and macroscopic plasticity, to modern continuum mechanics, and to the theory of cracks and fracture. The volume incorporates several new and original pieces of work, including a development of the theory of dislocation motion and plastic strain for non-linear materials, a new discussion of the line tension model, revised calculations of the Peierls resistance, and a new development of the van der Merwe theory of crystal interfaces.
Book Synopsis Dislocations and Plastic Deformation by : I. Kovács
Download or read book Dislocations and Plastic Deformation written by I. Kovács and published by Elsevier. This book was released on 2016-07-08 with total page 359 pages. Available in PDF, EPUB and Kindle. Book excerpt: Dislocations and Plastic Deformation deals with dislocations and plastic deformation, and specifically discusses topics ranging from deformation of single crystals and dislocations in the lattice to the fundamentals of the continuum theory, the properties of point defects in crystals, multiplication of dislocations, and partial dislocations. The effect of lattice defects on the physical properties of metals is also considered. Comprised of nine chapters, this book begins by providing a short and, where possible, precise explanation of dislocation theory. The first six chapters discuss the properties of dislocations and point defects both in crystals and in an elastic continuum. The reader is then introduced to some applications of dislocation theory that show, for instance, the difficulties involved in understanding the hardening of alloys and the work-hardening of pure metals. This book concludes by analyzing the effect of heat treatment on the defect structure in metals. This text will be of interest to students and practitioners in the field of physics.
Book Synopsis Dislocation Based Fracture Mechanics by : Johannes Weertman
Download or read book Dislocation Based Fracture Mechanics written by Johannes Weertman and published by World Scientific Publishing Company. This book was released on 1996-02-16 with total page 548 pages. Available in PDF, EPUB and Kindle. Book excerpt: The dislocation is the basic building block of the crack in an elastic-plastic solid. Fracture mechanics is developed in this text from its dislocation foundation. It is the only text to do so. It is written for the graduate student and the new investigator entering the fracture field as well as the experienced scientist who has not used the dislocation approach. The dislocation mechanics needed to find the dislocation density fields of crack tip plastic zones is developed in detail. All known dislocation based solutions are given for the three types of cracks in elastic-plastic solids are given.
Book Synopsis Mechanisms of Deformation and Fracture by : K. E. Easterling
Download or read book Mechanisms of Deformation and Fracture written by K. E. Easterling and published by Elsevier. This book was released on 2013-10-22 with total page 431 pages. Available in PDF, EPUB and Kindle. Book excerpt: Mechanisms of Deformation and Fracture contains the proceedings of the Interdisciplinary Conference on the Mechanisms of Deformation and Fracture held at the University of Luleå in Sweden on September 20-22, 1978. The papers explore the mechanisms underlying deformation and fracture of materials such as pearlite, metals, quartz, soils, and rocks. Results of theoretical and experimental studies on topics ranging from electromagnetic detection of low-cycle fatigue to stress and strain distribution in two-phase systems are presented. This book is comprised of 37 chapters and begins with a discussion on the interrelationships among solid mechanics, earth sciences, and material sciences. Subsequent chapters focus on the low-cycle behavior of case hardened steel; deformation and shear of normally consolidated flocculated kaolin; analytical modeling in inelasticity; creep mechanisms in clay; and initiation of crack growth at full plasticity. Plastic flow mechanisms and the rheological properties of the Earth's mantle are also examined, along with the fracture of glassy thermoplastics. The final chapter presents a thermodynamic model of consolidation in cohesive soils. This monograph will be a valuable resource for students and practitioners of mechanical engineering, metallurgy, materials science, and earth sciences.
Book Synopsis Crystal Plasticity Finite Element Methods by : Franz Roters
Download or read book Crystal Plasticity Finite Element Methods written by Franz Roters and published by John Wiley & Sons. This book was released on 2011-08-04 with total page 188 pages. Available in PDF, EPUB and Kindle. Book excerpt: Written by the leading experts in computational materials science, this handy reference concisely reviews the most important aspects of plasticity modeling: constitutive laws, phase transformations, texture methods, continuum approaches and damage mechanisms. As a result, it provides the knowledge needed to avoid failures in critical systems udner mechanical load. With its various application examples to micro- and macrostructure mechanics, this is an invaluable resource for mechanical engineers as well as for researchers wanting to improve on this method and extend its outreach.
Book Synopsis Deformation and Fracture of Solids by : Robert M. Caddell
Download or read book Deformation and Fracture of Solids written by Robert M. Caddell and published by Prentice Hall. This book was released on 1980 with total page 330 pages. Available in PDF, EPUB and Kindle. Book excerpt: Good,No Highlights,No Markup,all pages are intact, Slight Shelfwear,may have the corners slightly dented, may have slight color changes/slightly damaged spine.
Book Synopsis Multiscale Modeling of Dislocation and Grain Boundary Mechanics in Small Scale Metals by : Jamie Gravell
Download or read book Multiscale Modeling of Dislocation and Grain Boundary Mechanics in Small Scale Metals written by Jamie Gravell and published by . This book was released on 2021 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Metals are of great importance for structural applications due to their high yield strength and fracture toughness. In recent years, efforts have been undertaken to further improve these properties, accelerated by advances in materials research and manufacturing processes. The conventional strategy to achieve high strength is to reduce the average grain size, but this is inevitably followed by the loss of ductility. Deformation mechanisms for plastic flow and ductility are largely dependent on microscopic defects such as dislocations, grain boundaries (GBs), and triple junctions (TJs). It is necessary to obtain a fundamental understanding of the correlation between defect mechanics and macroscopic properties across a variety of time and length scales so as to overcome the strength-ductility trade-off. With this motivation, a computational and theoretical approach has been taken to investigate the complex interplay between defects and macroscopic material response. In the first part of this dissertation (Chapters 2-3), dislocation mechanics within single crystals are examined to understand the role of sample size, crystallographic orientation, and loading conditions on the mechanism response. The focus is drawn to the plastic deformation which occurs at the mesoscale, wherefrom material properties are determined. Chapter 2 reports on DD simulations conducted to examine plastic deformation in single crystalline Cu micropillars subjected to two types of combined loading conditions: tension after torsion and torsion after tension. These combined loadings are then compared with simple tension and pure torsion, respectively. In metallic materials, the activation of one slip system increases the flow strength of other slip systems, which is a phenomenon known as latent hardening. This latent hardening behavior has been understood by the “forest hardening” mechanism arising from mutual dislocation interactions at the continuum length scale. As the size of a sample decreases to the submicron scale, the interactions between dislocations become increasingly sparse, so plastic deformation is instead governed mainly by dislocation sources. We find that there exists a transition from latent hardening to latent softening in intermediately-sized 600 nm samples undergoing the combined tension after torsion loading. The systematic computational and theoretical model described here suggests explosive multiplication causes dislocation density to greatly increase, giving rise to latent softening in those micropillars under tension after torsion. At the continuum length scale, mechanical properties of metals show relatively weak orientation dependence; however, Chapter 3 shows how strong anisotropic behaviors are exhibited as the size of sample decreases to micron and nanometer length scales. DD simulations are performed to investigate the orientation-dependent plasticity in submicron face-centered cubic (FCC) micropillars subjected to torsion. Accommodating results from atomistic modeling, updated surface nucleation schemes in DD models have been developed for three orientations ([001], [101], and [111]), allowing investigation of the dislocation microstructure evolution and the corresponding anisotropic mechanical response upon torsional loading and unloading. The DD simulation results show that the coaxial and hexagonal dislocation networks formed in [101]- and [111]-oriented nanopillars, respectively, exhibited excellent plastic recovery, while the rectangular dislocation network formed in the [001] crystal orientation was more stable and did not experience as much plastic recovery. Following work on isolated dislocation mechanics within a single crystal, the second part of this dissertation, Chapter 4, transitions into the exploration of defect mechanisms within bicrystals. Mechanical properties of metals such as strength and toughness are strongly correlated to complex interactions between various defects in the crystalline structure. While elementary interactions between these defects have been investigated using recent micro- and nano-characterization techniques, understanding of the detailed interaction mechanisms has hardly been obtained. To model plasticity in polycrystals at larger time and length scales, it is necessary to formulate a general guideline to predict both the interaction type (transmission or reflection) and the dislocation’s subsequent slip system after the interaction. Many criteria based on the geometric alignment of the defects have been developed to predict this phenomenon, but these have not been found to be accurate when applied to general data sets of grain boundaries (GBs). With this motivation, we conduct a systematic study using molecular dynamics (MD) models of bicrystals to analyze defect interaction process between a prismatic dislocation loop and eleven different grain boundaries of the following character: three tilt, three twist, and five mixed. Based on the MD observations, two new prediction methods are developed: the first is a new data-driven parametric score function based on the classical geometric criteria, and the second is by applying Gaussian process machine learning methods to find the probability distribution of a hidden function. The proposed methods could pave a new way to predict the unit interaction of dislocation with various GBs, which could show much higher accuracy compared to pre-existing geometric criteria. Finally, additional work on paving the way to polycrystalline modeling at the mesoscale is detailed, followed by an overall summary in Chapter 5.
Book Synopsis Ductile Fracture and Ductility by : Bradley Dodd
Download or read book Ductile Fracture and Ductility written by Bradley Dodd and published by Academic Press. This book was released on 1987 with total page 328 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Ductile Fracture of Metals by : P. F. Thomason
Download or read book Ductile Fracture of Metals written by P. F. Thomason and published by Pergamon. This book was released on 1990 with total page 240 pages. Available in PDF, EPUB and Kindle. Book excerpt: An account of the recent developments in research into ductile fracture in metals and alloys. Aspects covered include localized fracture at the root of notches and sharp cracks, and fracture in bulk plastic-deformation processes of the metal and metal forming type. Also discusses various theoretical
Book Synopsis Testing of the Plastic Deformation of Metals by : T. W. Clyne
Download or read book Testing of the Plastic Deformation of Metals written by T. W. Clyne and published by Cambridge University Press. This book was released on 2021-06-10 with total page 297 pages. Available in PDF, EPUB and Kindle. Book excerpt: Discover a novel approach to the subject, providing detailed information about established and innovative mechanical testing procedures.
