Read Books Online and Download eBooks, EPub, PDF, Mobi, Kindle, Text Full Free.
Molecular Dynamics Study Of Void Growth And Dislocations In Dynamic Fracture Of Fcc And Bcc Metals
Download Molecular Dynamics Study Of Void Growth And Dislocations In Dynamic Fracture Of Fcc And Bcc Metals full books in PDF, epub, and Kindle. Read online Molecular Dynamics Study Of Void Growth And Dislocations In Dynamic Fracture Of Fcc And Bcc Metals ebook anywhere anytime directly on your device. Fast Download speed and no annoying ads. We cannot guarantee that every ebooks is available!
Book Synopsis Molecular Dynamics Study of Void Growth and Dislocations in Dynamic Fracture of FCC and BCC Metals by :
Download or read book Molecular Dynamics Study of Void Growth and Dislocations in Dynamic Fracture of FCC and BCC Metals written by and published by . This book was released on 2003 with total page 7 pages. Available in PDF, EPUB and Kindle. Book excerpt: Void growth with concomitant dislocation formation has been studied in single crystal face-centered-cubic and body-centered-cubic metals using molecular dynamics method with Embedded-Atom and Finnis-Sinclair potentials for copper and tantalum, respectively. We have concentrated on the quantitative analysis of the void shape evolution, on the structure of dislocations, which emerge from the void, and on the continuum measures such as plastic strain. The effects of strain-rate, differences between lattice structures, and loading conditions as uniaxial, biaxial, and triaxial expansion on the shape of the void and on the dislocations have been investigated.
Book Synopsis Void Growth and Coalescence in Dynamic Fracture from the Atomistic Level by :
Download or read book Void Growth and Coalescence in Dynamic Fracture from the Atomistic Level written by and published by . This book was released on 2010 with total page 4 pages. Available in PDF, EPUB and Kindle. Book excerpt: An important example of multiscale material response is the fracture of ductile solids. In the process of ductile fracture, voids nucleate, grow and coalesce, and it is this linking process that creates the fracture. Ductile fracture has typically been modeled at the continuum level, in a variety of models that may or may not model voids explicitly. Previously we have studied the plasticity associated with void growth in fcc metals, focusing on copper. In the work discussed here we examine void growth in single crystal and polycrystalline body-centered cubic (bcc) metals (V, Nb, Ta, Mo and W) subjected to tension at a high rate and high triaxiality. Large-scale atomistic models provide detailed information on void nucleation and growth and the plasticity generated as voids coalesce, based solely on the constitutive properties inherent in the interatomic forces. The details of the plasticity may be used to inform dislocation dynamics and continuum plasticity models in order to develop models that scale beyond the nanoscale. We also discuss concurrent multiscale modeling of void growth using Coarse-Grained Molecular Dynamics.
Book Synopsis Effect of Stress-triaxiality on Void Growth in Dynamic Fracture of Metals by :
Download or read book Effect of Stress-triaxiality on Void Growth in Dynamic Fracture of Metals written by and published by . This book was released on 2003 with total page 20 pages. Available in PDF, EPUB and Kindle. Book excerpt: The effect of stress-triaxiality on growth of a void in a three dimensional single-crystal face-centered-cubic (FCC) lattice has been studied. Molecular dynamics (MD) simulations using an embedded-atom (EAM) potential for copper have been performed at room temperature and using strain controlling with high strain rates ranging from 107/sec to 101°/sec. Strain-rates of these magnitudes can be studied experimentally, e.g. using shock waves induced by laser ablation. Void growth has been simulated in three different conditions, namely uniaxial, biaxial, and triaxial expansion. The response of the system in the three cases have been compared in terms of the void growth rate, the detailed void shape evolution, and the stress-strain behavior including the development of plastic strain. Also macroscopic observables as plastic work and porosity have been computed from the atomistic level. The stress thresholds for void growth are found to be comparable with spall strength values determined by dynamic fracture experiments. The conventional macroscopic assumption that the mean plastic strain results from the growth of the void is validated. The evolution of the system in the uniaxial case is found to exhibit four different regimes: elastic expansion; plastic yielding, when the mean stress is nearly constant, but the stress-triaxiality increases rapidly together with exponential growth of the void; saturation of the stress-triaxiality; and finally the failure.
Book Synopsis Three-Dimensional Molecular Dynamics Simulations of Void Coalescence During Dynamic Fracture of Ductile Metals by :
Download or read book Three-Dimensional Molecular Dynamics Simulations of Void Coalescence During Dynamic Fracture of Ductile Metals written by and published by . This book was released on 2004 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Void coalescence and interaction in dynamic fracture of ductile metals have been investigated using three-dimensional strain-controlled multi-million atom molecular dynamics simulations of copper. The correlated growth of two voids during the coalescence process leading to fracture is investigated, both in terms of its onset and the ensuing dynamical interactions. Void interactions are quantified through the rate of reduction of the distance between the voids, through the correlated directional growth of the voids, and through correlated shape evolution of the voids. The critical inter-void ligament distance marking the onset of coalescence is shown to be approximately one void radius based on the quantification measurements used, independent of the initial separation distance between the voids and the strain-rate of the expansion of the system. The interaction of the voids is not reflected in the volumetric asymptotic growth rate of the voids, as demonstrated here. Finally, the practice of using a single void and periodic boundary conditions to study coalescence is examined critically and shown to produce results markedly different than the coalescence of a pair of isolated voids.
Book Synopsis Molecular Dynamic Study of Edge Dislocations and Stacking Faults in FCC Metals by :
Download or read book Molecular Dynamic Study of Edge Dislocations and Stacking Faults in FCC Metals written by and published by . This book was released on 2000 with total page 38 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis A Study of the Mechanism of Dynamic Ductile Fracture of Two-Phase Materials by : Minoru Taya
Download or read book A Study of the Mechanism of Dynamic Ductile Fracture of Two-Phase Materials written by Minoru Taya and published by . This book was released on 1986 with total page 35 pages. Available in PDF, EPUB and Kindle. Book excerpt: Dynamic ductile fracture of two phase material have been investigated in two stages. The first stage is a model study where an idealized two phase material, single crystal Cu SiO2 was used to study the initiation and growth of voids, the dislocation morphology and the other microscopic behavior that took place in the as-impacted speciment. Important findings are voids were nucleated from only a fraction of secondary particles SiO2, the larger strain has induced the higher void density, and the dislocation cell structures were formed with the average cell size being constant for the range of strain rates investigated. Analytical models were constructed with the aim of simulating the void growth in a two phase material subjected to high strain rate deformation, static void growth model and dynamic void growth model. A comparison of the void density indicated the static void growth model can predict the experimental results reasonably well for the smaller strain, but it fails to predict for the larger strain, while the dynamic void growth model can simulate the void growth well for the entire range of strain and strain rates. The second stage conducts a series of experiments on more realistic two phase materials, Al Si alloy and SiC(w) or SiC(p)/Al composite. The mode of the initiation and growth of voids was observed in the specimens that were impacted by Split Hopkinson bar test. The void density was also measured along the specimen axis and its values were compared with the analytical results by the static void growth model, resulting in a reasonably good agreement.
Book Synopsis High-Pressure Shock Compression of Solids II by : Lee Davison
Download or read book High-Pressure Shock Compression of Solids II written by Lee Davison and published by Springer Science & Business Media. This book was released on 2012-12-06 with total page 496 pages. Available in PDF, EPUB and Kindle. Book excerpt: This volume concerns the fracture and fragmentation of solid materials that occurs when they are subjected to extremes of stress applied at the highest possible rates. The plan for the volume is to address experimental, theoretical, and com putational aspects of high-rate dynamic fracture and fragmentation, with emphasis on recent work. We begin with several chapters in which the emphasis falls on experimental methods and observations. These chapters address both macroscopic responses and the microscopic cause of these re sponses. This is followed by several chapters emphasizing modeling-the physical explanation and mathematical representation of the observations. Some of the models are deterministic, while others focus on the stochastic aspects of the observations. Often, the ov\!rall objective of investigation of dynamic fracture and fragmentation phenomena is provision of a means for predicting the entire course of an event that begins with a stimulus such as an impact and proceeds through a complicated deformation and fracture pro cess that results in disintegration of the body and formation of a rapidly expanding cloud of debris fragments. Analysis of this event usually involves development of a continuum theory and computer code that captures the experimental observations by incorporating models of the important pheno mena into a comprehensive description of the deformation and fracture pro cess. It is to this task that the work of the last few chapters is devoted.
Book Synopsis Void Coalescence Processes Quantified Through Atomistic and Multiscale Simulation by :
Download or read book Void Coalescence Processes Quantified Through Atomistic and Multiscale Simulation written by and published by . This book was released on 2007 with total page 13 pages. Available in PDF, EPUB and Kindle. Book excerpt: Simulation of ductile fracture at the atomic scale reveals many aspects of the fracture process including specific mechanisms associated with void nucleation and growth as a precursor to fracture and the plastic deformation of the material surrounding the voids and cracks. Recently we have studied void coalescence in ductile metals using large-scale atomistic and continuum simulations. Here we review that work and present some related investigations. The atomistic simulations involve three-dimensional strain-controlled multi-million atom molecular dynamics simulations of copper. The correlated growth of two voids during the coalescence process leading to fracture is investigated, both in terms of its onset and the ensuing dynamical interactions. Void interactions are quantified through the rate of reduction of the distance between the voids, through the correlated directional growth of the voids, and through correlated shape evolution of the voids. The critical inter-void ligament distance marking the onset of coalescence is shown to be approximately one void radius based on the quantification measurements used, independent of the initial separation distance between the voids and the strain-rate of the expansion of the system. No pronounced shear flow is found in the coalescence process. We also discuss a technique for optimizing the calculation of fine-scale information on the fly for use in a coarse-scale simulation, and discuss the specific case of a fine-scale model that calculates void growth explicitly feeding into a coarse-scale mechanics model to study damage localization.
Book Synopsis Microstructural Origins of Dynamic Fracture in Ductile Metals by : Alfred Schwartz
Download or read book Microstructural Origins of Dynamic Fracture in Ductile Metals written by Alfred Schwartz and published by . This book was released on 2004 with total page 23 pages. Available in PDF, EPUB and Kindle. Book excerpt: Dynamic fracture is a material failure process at high strain-rates. Here, we limit our discussion to spallation fracture during shock wave loading. When a compressive shock wave reflects from a free surface, internal states of tension are created. If this tension exceeds the rupture strength of the material, it fails by nucleating and growing microscopic voids in ductile metals and cracks in brittle solids. This effect, known as spallation, was reported by Hopkinson in 1872 [1]. Rinehart and Pierson [2] give an historical introduction to spallation and other aspects of high strain-rate deformation. This phenomenology of the nucleation and growth of microscopic voids is common to all fracture in ductile metals, including dynamic fracture. The importance of pulse duration was not fully appreciated until the 1960's through the work of Butcher and colleagues [3, 4], leading to the concept of cumulative damage. This concept of damage accumulation was put on a strong experimental foundation by Barbee et al. [5], who performed gas gun recovery experiments and tediously measured the size and distribution of microscopic flaws using 2D microscopy. The resulting continuum material model of dynamic fracture is known as the SRI-NAG model [6, 7], for Nucleation And Growth. In a critical assessment of dynamic fracture, Meyers and Aimone [8] reviewed the abundant continuum spallation models and found the model of nucleation, growth, and coelescense of voids to qualitatively reproduce the observed extent of damage from spall recovery experiments. As in the work of Barbee et al. [5], Meyers and Aimone do not find any voids smaller than about 1 {micro}m, suggesting that the voids either nucleated at that scale or when they are nucleated they rapidly grow to the micron size scale. The continuum models are phenomenological in nature with parameters fit to experiment. The advent of the Advanced Strategic Computing program has enabled direct numerical simulation of the nucleation and growth of microscopic voids. However, there exists no experimental data to both guide the modeling to the essential physical phenomena and to validate meso-scale modeling of dynamic fracture in ductile metals. The goal of this project is to obtain this new experimental data for dynamic fracture in ductile metals by characterizing and analyzing the microscopic processes using modern experimental facilities not previously available. In particular, we measured with increased precision the damage produced during spallation fracture in ductile metals. Dynamic gas-gun recovery experiments were used to generate incipient spallation damage while concurrently measuring the free surface velocity wave profile. This wave profile has been used extensively to characterize spallation fracture. The concurrent measurement enables us to correlate the observed incipient damage with features in the wave profile, such as the velocity pull back. The incipient spallation damage was characterized using both advanced Synchrotron-based 3D X-Ray tomography and traditional 2D microscopy. A direct correlation was made between the traditional 2D microscopy and the 3D distribution of voids on the same sample. 2D microscopy, including optical, EBS/OIM, and TEM, was used to quantify, for the first time, the plastically deformed zone in the metal surrounding an incipiently grown void. Nanoindentation hardness experiments were used to quantify the increased strength in the plastically deformed zone from the greatly increased dislocation density.
Book Synopsis Void initiation, growth, and coalescence in ductile fracture of metals by : Heinz G. F. Wilsdorf
Download or read book Void initiation, growth, and coalescence in ductile fracture of metals written by Heinz G. F. Wilsdorf and published by . This book was released on 1976 with total page 28 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Molecular Dynamics Simulation of Dislocation Mobility of a Body-centered Cubic Metal by : Jinpeng Chang
Download or read book Molecular Dynamics Simulation of Dislocation Mobility of a Body-centered Cubic Metal written by Jinpeng Chang and published by . This book was released on 2000 with total page 200 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Crack Nucleation Related Dislocation Dynamics - A Numerical Study on the FCC Metal by : Harold W. H. Kwok
Download or read book Crack Nucleation Related Dislocation Dynamics - A Numerical Study on the FCC Metal written by Harold W. H. Kwok and published by . This book was released on 2011 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Dislocation Interactions with Voids and Helium Bubbles in FCC Metals by : J. Young
Download or read book Dislocation Interactions with Voids and Helium Bubbles in FCC Metals written by J. Young and published by . This book was released on 2003 with total page 8 pages. Available in PDF, EPUB and Kindle. Book excerpt: The formation of a high number density of helium bubbles in FCC metals irradiated within the fusion energy environment is well established. Yet, the role of helium bubbles in radiation hardening and mechanical property degradation of these steels remains an outstanding issue. In this paper, we present the results of a combined molecular dynamics simulation and in-situ straining transmission electron microscopy study, which investigates the interaction mechanisms between glissile dislocations and nanometer-sized helium bubbles. The molecular dynamics simulations, which directly account for dislocation core effects through semi-empirical interatomic potentials, provide fundamental insight into the effect of helium bubble size and internal gas pressure on the dislocation/bubble interaction and bypass mechanisms. The combination of simulation and in-situ straining experiments provides a powerful approach to determine the atomic to microscopic mechanisms of dislocation-helium bubble interactions, which govern the mechanical response of metals irradiated within the fusion environment.
Book Synopsis Void Coalescence Processes Quantified Through Atomistic and Multiscale Simulation by : R. E. Rudd
Download or read book Void Coalescence Processes Quantified Through Atomistic and Multiscale Simulation written by R. E. Rudd and published by . This book was released on 2005 with total page 9 pages. Available in PDF, EPUB and Kindle. Book excerpt: Simulation of ductile fracture at the atomic scale reveals many aspects of the fracture process including specific mechanisms associated with void nucleation and growth as a precursor to fracture and the plastic deformation of the material surrounding the voids and cracks. Recently we have studied void coalescence in ductile metals using large-scale atomistic and continuum simulations. Here we review that work and present some related investigations. The atomistic simulations involve three-dimensional strain-controlled multi-million atom molecular dynamics simulations of copper. The correlated growth of two voids during the coalescence process leading to fracture is investigated, both in terms of its onset and the ensuing dynamical interactions. Void interactions are quantified through the rate of reduction of the distance between the voids, through the correlated directional growth of the voids, and through correlated shape evolution of the voids. The critical inter-void ligament distance marking the onset of coalescence is shown to be approximately one void radius based on the quantification measurements used, independent of the initial separation distance between the voids and the strain-rate of the expansion of the system. No pronounced shear flow is found in the coalescence process.
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 A Numerical Study of the Influence of Void Growth on Ductile Fracture and Metal Extrusion by : Nikolaos Aravas
Download or read book A Numerical Study of the Influence of Void Growth on Ductile Fracture and Metal Extrusion written by Nikolaos Aravas and published by . This book was released on 1987 with total page 340 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Scientific and Technical Aerospace Reports by :
Download or read book Scientific and Technical Aerospace Reports written by and published by . This book was released on 1989 with total page 988 pages. Available in PDF, EPUB and Kindle. Book excerpt:
