Download or read book Using Molecular Dynamics to Develop a Crystal Plasticity Model for BCC Slip written by and published by . This book was released on 2013 with total page 25 pages. Available in PDF, EPUB and Kindle. Book excerpt:

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.

Download or read book A Molecular Dynamics Study of Nanocontact Plasticity and Dislocation Avalanches in FCC and BCC Crystals written by Javier Varillas and published by . This book was released on 2019 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: This study aims to investigate the underlying mechanisms which govern the development of dense defect networks in nanoscale crystal plasticity, either under contact and uniaxial loading conditions, with emphasis on the onset of intermittent avalanche phenomena. The investigation is based on a comprehensive set of massive molecular dynamics (MD) simulations performed with embedded-atom method potentials in face-centered cubic (FCC) and body-centered cubic (BCC) crystals. The first part of the thesis concerns the combined role of elasticity and plasticity in nanocontact loadings, where attention is given to the mechanisms leading to the formation of a permanent nanoimprint as well as to the onset of material pile-up at the contact vicinity. It is found that the topographical arrangement of the slip traces emitted at the surface into specific deformation patterns is a distinctive feature of the underlying dislocation glide and twinning processes occurring in FCC and BCC crystals as a function of temperature and surface orientation. A mechanistic analysis is made on the influence of the defect nucleation events in conjunction with the development of entangled defect networks upon the material hardness and its evolution towards a plateau level with increasing indenter-tip penetration. Complementary MD simulations of the uniaxial stress-strain curve of the plastically deformed region are carried out with the purpose of establishing a direct correlation between nanoscale material responses attaining under uniaxial and contact loading conditions. The results of this comparison illustrate on the key role played by defect nucleation processes on the formation of permanent nanoimprints, which differs from the conventional view in that in micro and macroscopic scales imprint formation is essentially governed by the evolutionary character of a preexisting (entangled) defect network: the greater the dislocation density, the larger the measured hardness. In overall, this work provides a fundamental insight into the understanding of why BCC surfaces are harder than FCC surfaces at the nanoscale. A statistical physics background is devised to investigate the influence of the dislocation mechanisms on the onset of avalanche events that are inherent to crystal plasticity. The analysis is predicated upon the notion in that the size distribution of such avalanches follows power-law scaling. To investigate the avalanche size distributions in cubic crystals, a group of novel MD simulations are performed where the computational cells containing a periodic arrangement of a preexisting dislocation network are subjected to uniaxial straining under displacement control at different strain rates and temperatures. Under sufficiently slow driving, the dislocation networks evolve through the emission of dislocation avalanches which do not overlap in time. This illustrates that the mobilized entangled dislocation arrangements exhibit quiescent periods during each plastic (dissipative) event, enabling comparison with experimental results which are also performed under strict displacement controlled conditions. The results illustrate on the attainment of a transitional slip size separating two power-law avalanche regimes as a function of the fundamental dislocation glide processes at the crossroads of self-organized and tuned criticality models. Detailed analyses of the MD simulations furnish specific mechanisms characterizing dislocation avalanche emission and propagation in FCC and BCC metals throughout a wide temperature range, which is central in supporting the onset of the aforementioned two power-law regimes.

Download or read book Crystal Plasticity at Micro and Nano scale Dimensions written by Ronald W. Armstrong and published by MDPI. This book was released on 2021-08-31 with total page 322 pages. Available in PDF, EPUB and Kindle. Book excerpt: The present collection of articles focuses on the mechanical strength properties at micro- and nanoscale dimensions of body-centered cubic, face-centered cubic and hexagonal close-packed crystal structures. The advent of micro-pillar test specimens is shown to provide a new dimensional scale for the investigation of crystal deformation properties. The ultra-small dimensional scale at which these properties are measured is shown to approach the atomic-scale level at which model dislocation mechanics descriptions of crystal slip and deformation twinning behaviors are proposed to be operative, including the achievement of atomic force microscopic measurements of dislocation pile-up interactions with crystal grain boundaries or with hard surface coatings. A special advantage of engineering designs made at such small crystal and polycrystalline dimensions is the achievement of an approximate order-of-magnitude increase in mechanical strength levels. Reasonable extrapolation of macro-scale continuum mechanics descriptions of crystal strength properties at micro- to nano-indentation hardness measurements are demonstrated, in addition to reports on persistent slip band observations and fatigue cracking behaviors. High-entropy alloy, superalloy and energetic crystal properties are reported along with descriptions of deformation rate sensitivities, grain boundary structures, nano-cutting, void nucleation/growth micromechanics and micro-composite electrical properties.

Download or read book Computer Simulations of Crystal Plasticity at Different Length Scales written by Bingqing Cheng and published by . This book was released on 2017-01-27 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: This dissertation, "Computer Simulations of Crystal Plasticity at Different Length Scales" by Bingqing, Cheng, 程冰清, was obtained from The University of Hong Kong (Pokfulam, Hong Kong) and is being sold pursuant to Creative Commons: Attribution 3.0 Hong Kong License. The content of this dissertation has not been altered in any way. We have altered the formatting in order to facilitate the ease of printing and reading of the dissertation. All rights not granted by the above license are retained by the author. Abstract: Crystal plasticity has been an active research field for several decades. The crystal plasticity of the bulk materials has its key relevance in the industrial process. Besides, the plasticity of nano-sized materials becomes a topic attracting a lot of interest recently. In the Part I of the thesis, molecular dynamics (MD) simulations were used to study the plasticity of small nanoparticles. Firstly, the coalescence process of Cu nanoparticles was explored. It was found that a peculiar type of five-fold twins in the sintered products were formed via an unseen before dislocation-free process involving a series of shear waves and rigid-body rotations. Secondly, a similar study on the heating of a single nanoparticle was conducted. The same dislocation-free shear wave mechanism was spotted again. In this mechanism, a cluster of atoms rearranges in a highly coordinated way between different geometrical configurations (e.g. fcc, decahedral, icosahedral) without involving dislocations. Thirdly, simulations on the sintering of many nanoparticles were performed, and the governing processes during the consolidation were discussed. The findings in this part of the thesis can provide some guidance for controlling the motifs of nanoparticles. In Part II of the thesis, the emphasis was switched to the crystal plasticity at larger spatial and temporal scales. A dislocation density-based model was developed in our research group. This model employs a dynamics formulation in which the force on each group of dislocation density is calculated with the Taylor and mutual elastic interactions taken into account. The motion of the dislocation densities is then predicted using a conservative law, with annihilation and generation considered. The new dislocation density-based model was used in this work to simulate the plastic deformation of single crystals under ultrasonic irradiation. Softening during vibrations as well as enhanced cell formation was predicted. This is the first simulation effort to successfully predict the cell formation phenomenon under vibratory loadings. DOI: 10.5353/th_b5317059 Subjects: Crystals - Plastic properties - Computer simulation

Download or read book Multiscale Modelling of Plasticity and Fracture by Means of Dislocation Mechanics written by Peter Gumbsch and published by Springer Science & Business Media. This book was released on 2011-01-30 with total page 401 pages. Available in PDF, EPUB and Kindle. Book excerpt: The latest state of simulation techniques to model plasticity and fracture in crystalline materials on the nano- and microscale is presented. Discrete dislocation mechanics and the neighbouring fields molecular dynamics and crystal plasticity are central parts. The physical phenomena, the theoretical basics, their mathematical description and the simulation techniques are introduced and important problems from the formation of dislocation structures to fatigue and fracture from the nano- to microscale as well as it’s impact on the macro behaviour are considered.

Download or read book Crystal Plasticity Modeling of the Deformation of BCC Iron and Niobium Single Crystals written by Aboozar Mapar and published by . This book was released on 2017 with total page 207 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Dislocation Mechanism Based Crystal Plasticity written by Zhuo Zhuang and published by Academic Press. This book was released on 2019-04-12 with total page 452 pages. Available in PDF, EPUB and Kindle. Book excerpt: Dislocation Based Crystal Plasticity: Theory and Computation at Micron and Submicron Scale provides a comprehensive introduction to the continuum and discreteness dislocation mechanism-based theories and computational methods of crystal plasticity at the micron and submicron scale. Sections cover the fundamental concept of conventional crystal plasticity theory at the macro-scale without size effect, strain gradient crystal plasticity theory based on Taylar law dislocation, mechanism at the mesoscale, phase-field theory of crystal plasticity, computation at the submicron scale, including single crystal plasticity theory, and the discrete-continuous model of crystal plasticity with three-dimensional discrete dislocation dynamics coupling finite element method (DDD-FEM). Three kinds of plastic deformation mechanisms for submicron pillars are systematically presented. Further sections discuss dislocation nucleation and starvation at high strain rate and temperature effect for dislocation annihilation mechanism. - Covers dislocation mechanism-based crystal plasticity theory and computation at the micron and submicron scale - Presents crystal plasticity theory without size effect - Deals with the 3D discrete-continuous (3D DCM) theoretic and computational model of crystal plasticity with 3D discrete dislocation dynamics (3D DDD) coupling finite element method (FEM) - Includes discrete dislocation mechanism-based theory and computation at the submicron scale with single arm source, coating micropillar, lower cyclic loading pillars, and dislocation starvation at the submicron scale

Download or read book Applied Nanoindentation in Advanced Materials written by Atul Tiwari and published by John Wiley & Sons. This book was released on 2017-10-30 with total page 704 pages. Available in PDF, EPUB and Kindle. Book excerpt: Research in the area of nanoindentation has gained significant momentum in recent years, but there are very few books currently available which can educate researchers on the application aspects of this technique in various areas of materials science. Applied Nanoindentation in Advanced Materials addresses this need and is a comprehensive, self-contained reference covering applied aspects of nanoindentation in advanced materials. With contributions from leading researchers in the field, this book is divided into three parts. Part one covers innovations and analysis, and parts two and three examine the application and evaluation of soft and ceramic-like materials respectively. Key features: A one stop solution for scholars and researchers to learn applied aspects of nanoindentation Contains contributions from leading researchers in the field Includes the analysis of key properties that can be studied using the nanoindentation technique Covers recent innovations Includes worked examples Applied Nanoindentation in Advanced Materials is an ideal reference for researchers and practitioners working in the areas of nanotechnology and nanomechanics, and is also a useful source of information for graduate students in mechanical and materials engineering, and chemistry. This book also contains a wealth of information for scientists and engineers interested in mathematical modelling and simulations related to nanoindentation testing and analysis.

Download or read book A Quantized Crystal Plasticity Model for Nanocrystalline Metals written by Lin Li and published by . This book was released on 2011 with total page 156 pages. Available in PDF, EPUB and Kindle. Book excerpt: Abstract: Nanocrystalline (NC) metals, which consist of grains or crystallites with sizes less than 100 nm, have exhibited unique mechanical and physical properties, in comparison to coarse-grained (CG) counterparts. The appealing mechanical properties, for instance, include extremely high strengths, very extended elastic-plastic transitions, and unprecedented magnitudes of recoverable plastic strain. Further, footprints of inter-granular stresses measured from diffraction experiments are distinct for NC metals vs. CG metals. In particular, recent in-situ synchrotron measurements reveal that residual lattice strains change rather modestly even after imposing macro plastic strains to ~1%. Remarkably, over the same regime, the corresponding residual peak widths decrease. These phenomena are in sharp contrast to CG metals, for which residual lattice strain and peak widths both increase with deformation. In this dissertation, a quantized crystal plasticity (QCP) model is developed to explore the aforementioned unique NC features. The QCP model employs a crystallographic description of dislocation slip plasticity; in particular, single slip events across nano scale grains impart large (~1%) increments in grain-averaged plastic shear. Therefore, plasticity does not proceed in a smooth, continuous fashion but rather via strain jumps, imparting violent grain-to-grain redistribution in stress. This discrete feature is consistent with recent Molecular Dynamics (MD) simulations, which illustrate a dramatic jump in grain-averaged shear strain when a dislocation spontaneously transverses a nano grain interior after depinning from grain boundary (GB) ledges. Finite element simulations implementing this quantized plasticity approach predict the experimental properties of enhanced strength, extended elastic-plastic strain, and recoverable plastic strain, as well as the trends in residual lattice strain and peak width mentioned, but only under certain conditions. First, the grain-to-grain distribution of critical stress for slip activation is very different from that for CG materials. In particular, no events occur below a rather large threshold stress ~ 1/grain size; and above this threshold, a very asymmetric distribution predominates, signifying that a relatively large number of easier-to-slip grains are balanced by a minority of harder-to-slip grains. Second, there exists a large residual stress state, which can be removed via post deformation. The quantized crystal plasticity provides an alternate view of NC deformation, compared to hypotheses in the literature that are centered on GB sliding or deformation of a GB phase separated from grain interior. The QCP model is capable of bridging the disparity in length and time scales between MD simulations and physical experiments, and as well establishes an insightful connection between them.

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.

Download or read book Size Effects in Plasticity written by George Voyiadjis and published by Academic Press. This book was released on 2019-08-01 with total page 410 pages. Available in PDF, EPUB and Kindle. Book excerpt: Size Effects in Plasticity: From Macro to Nano provides concise explanations of all available methods in this area, from atomistic simulation, to non-local continuum models to capture size effects. It then compares their applicability to a wide range of research scenarios. This essential guide addresses basic principles, numerical issues and computation, applications and provides code which readers can use in their own modeling projects. Researchers in the fields of computational mechanics, materials science and engineering will find this to be an ideal resource when they address the size effects observed in deformation mechanisms and strengths of various materials. - Provides a comprehensive reference on the field of size effects and a review of mechanics of materials research in all scales - Explains all major methods of size effects simulation, including non-local continuum models, non-local crystal plasticity, discrete dislocation methods and molecular dynamics - Includes source codes that readers can use in their own projects

Download or read book High Resolution Crystal Plasticity Simulations written by Martin Diehl and published by Apprimus Wissenschaftsverlag. This book was released on 2016-03-02 with total page 138 pages. Available in PDF, EPUB and Kindle. Book excerpt: In this work the possibilities and capabilities of high-resolution crystal plasticity simulations are presented and discussed. Giving several examples, it is shown how the application of crystal plasticity simulations helps to understand the micro-mechanical behaviour of crystalline materials. To avoid the high computational costs associated with crystal plasticity simulations that arise from (i) the evaluation of the selected constitutive law, and (ii) the solution of the associated mechanical boundary value problem, both contributions to the runtime have to be kept small. This is done by (i) employing a rather simple—and therefore fast—constitutive model, and by (ii) using an effective spectral method employing fast Fourier transforms for solving the partial differential equations describing the mechanical behaviour. Here, an improved spectral solver incorporated into the Düsseldorf Advanced Material Simulation Kit (DAMASK) is used.

Download or read book The Mechanics and Thermodynamics of Continua written by Morton E. Gurtin and published by Cambridge University Press. This book was released on 2010-04-19 with total page 721 pages. Available in PDF, EPUB and Kindle. Book excerpt: The Mechanics and Thermodynamics of Continua presents a unified treatment of continuum mechanics and thermodynamics that emphasises the universal status of the basic balances and the entropy imbalance. These laws are viewed as fundamental building blocks on which to frame theories of material behaviour. As a valuable reference source, this book presents a detailed and complete treatment of continuum mechanics and thermodynamics for graduates and advanced undergraduates in engineering, physics and mathematics. The chapters on plasticity discuss the standard isotropic theories and, in addition, crystal plasticity and gradient plasticity.

Download or read book Crystal Plasticity Modeling of Deformation in FCC Metals and Predictions for Recrystallization Nucleation written by Supriyo Chakraborty (Ph. D. materials engineering) and published by . This book was released on 2021 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Crystal plasticity modeling was used to understand the deformation process of FCC metals and alloys. Firstly, we investigated the issue of cube texture development during static recrystallization of FCC metals, which has been vigorously debated over the last 70 years. A Full-field elasto-viscoplastic fast-Fourier transform (EVP-FFT)based crystal plasticity solver coupled with dislocation density based constitutive model was employed to understand the deformation process in copper under plane strain compression. Simulation results revealed that the grains with initially cube orientation retained a small fraction of the cube component in the deformed state, whereas, some of the grains with initially non-cube orientations developed the cube component during the deformation. For strain up to 0.46, non-cube grains which are within 10-20 deg from the ideal cube orientation showed the highest affinity to develop the cube component during deformation. However, the cube component developed during the deformation was unstable and rotated away from the cube orientation with further deformation. With increasing strain up to 1.38, some of the grains with higher angular deviation from the ideal cube orientation also developed the cube component. No particular axis preference was observed for the non-cube grains, rather, the evolution of the cube component becomes dynamic at larger strain. Rotation of the non-cube grains towards the cube component is mainly driven by the local relaxation of the imposed boundary conditions. Significant changes in lattice rotation and slip activity were observed with different relaxed constraints. Best correlation was found for the e13 strain component and the development of cube component. Analysis of the disorientation angle and the dislocation density difference with the neighboring locations showed that the cube component developed during the deformation can play a significant role during nucleation. Secondly, we used the mean-field visco-plastic self-consistent (VPSC) and the full-field EVP-FFT based crystal plasticity models to investigate the effect of different deformation modes and their interactions on the mechanical behavior and texture evolution in the equiatomic CrCoNi alloy. The presence of twin/HCP lamella has been attributed to the excellent mechanical behavior of this alloy. However, this hypothesis is not critically studied yet. An electron back scatter diffraction (EBSD) microstructure image was considered as input for both the EVP-FFT and VPSC simulations. We found the latent hardening ratio of twin to slip systems is approximately three times higher. Although twinning started to occur in those grains which are oriented along 111, substantial twinning has been found in almost all the grains at higher strain. We observed that the overall texture evolution is only influenced by slip mechanism and twinning has negligible effect on it. grain rotation predicted by the full field simulations matched well with the EBSD observation.

Download or read book Classical And Quantum Dynamics In Condensed Phase Simulations Proceedings Of The International School Of Physics written by Bruce J Berne and published by World Scientific. This book was released on 1998-06-17 with total page 881 pages. Available in PDF, EPUB and Kindle. Book excerpt: The school held at Villa Marigola, Lerici, Italy, in July 1997 was very much an educational experiment aimed not just at teaching a new generation of students the latest developments in computer simulation methods and theory, but also at bringing together researchers from the condensed matter computer simulation community, the biophysical chemistry community and the quantum dynamics community to confront the shared problem: the development of methods to treat the dynamics of quantum condensed phase systems.This volume collects the lectures delivered there. Due to the focus of the school, the contributions divide along natural lines into two broad groups: (1) the most sophisticated forms of the art of computer simulation, including biased phase space sampling schemes, methods which address the multiplicity of time scales in condensed phase problems, and static equilibrium methods for treating quantum systems; (2) the contributions on quantum dynamics, including methods for mixing quantum and classical dynamics in condensed phase simulations and methods capable of treating all degrees of freedom quantum-mechanically.

Download or read book Statistical Analysis and Constitutive Modeling of Crystal Plasticity Using Dislocation Dynamics Simulation Database written by Shamseddin Akhondzadeh and published by . This book was released on 2021 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: