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Journal ArticleDOI

Void growth by dislocation emission

05 Apr 2004-Acta Materialia (Pergamon)-Vol. 52, Iss: 6, pp 1397-1408
TL;DR: In this paper, a criterion for the emission of a dislocation from the surface of a void under remote tension is formulated, analogous to Rice and Thomsons criterion for crack blunting by dislocation emission from the crack tip.
About: This article is published in Acta Materialia.The article was published on 2004-04-05. It has received 302 citations till now. The article focuses on the topics: Dislocation & Void (astronomy).
Citations
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Journal ArticleDOI
TL;DR: In this paper, the first overview of failure of metals is presented, focusing on brittle and ductile failure under monotonic loadings, where the focus is on linking microstructure, physical mechanisms and overall fracture properties.

639 citations


Cites background from "Void growth by dislocation emission..."

  • ...[371] to derive a criterion in stress space for void nucleation by dislocation emission....

    [...]

01 Jan 2001
TL;DR: In this paper, a model for the axisymmetric growth and coalescence of small internal voids in elastoplastic solids is proposed and assessed using void cell computations.
Abstract: A model for the axisymmetric growth and coalescence of small internal voids in elastoplastic solids is proposed and assessed using void cell computations. Two contributions existing in the literature have been integrated into the enhanced model. The first is the model of Gologanu-Leblond-Devaux, extending the Gurson model to void shape effects. The second is the approach of Thomason for the onset of void coalescence. Each of these has been extended heuristically to account for strain hardening. In addition, a micromechanically-based simple constitutive model for the void coalescence stage is proposed to supplement the criterion for the onset of coalescence. The fully enhanced Gurson model depends on the flow properties of the material and the dimensional ratios of the void-cell representative volume element. Phenomenological parameters such as critical porosities are not employed in the enhanced model. It incorporates the effect of void shape, relative void spacing, strain hardening, and porosity. The effect of the relative void spacing on void coalescence, which has not yet been carefully addressed in the literature. has received special attention. Using cell model computations, accurate predictions through final fracture have been obtained for a wide range of porosity, void spacing, initial void shape, strain hardening, and stress triaxiality. These predictions have been used to assess the enhanced model. (C) 2000 Elsevier Science Ltd. All rights reserved.

519 citations

Journal ArticleDOI
TL;DR: In this paper, the authors used LAMMPS simulations in monocrystalline and bicrystalline copper to reveal void growth mechanisms and found that the emission of dislocations from voids is the first stage, and their reaction and interaction is the second stage.

227 citations

Journal ArticleDOI
TL;DR: In this paper, it was shown that the emission and outward expansion of special dislocation loops, nucleated at the surface of nanosized voids, are responsible for the outward flux of matter, promoting their growth.

157 citations

Journal Article
TL;DR: An overview of experimental study, computer simulations and theoretical models of fracture of nanocrystalline materials is presented in this paper, where the key experimentally detected facts on ductile and brittle fracture processes are discussed.
Abstract: An overview of experimental study, computer simulations and theoretical models of fracture of nanocrystalline materials is presented. The key experimentally detected facts on ductile and brittle fracture processes are discussed. Special attention is paid to computer simulations and theoretical models of nucleation and growth of nanocracks and nanopores in deformed nanocrystalline materials. Also, we discuss mechanisms for fracture suppression in such materials showing good ductility or superplasticity.

117 citations

References
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Book
01 Jan 1934
TL;DR: The theory of the slipline field is used in this article to solve the problem of stable and non-stressed problems in plane strains in a plane-strain scenario.
Abstract: Chapter 1: Stresses and Strains Chapter 2: Foundations of Plasticity Chapter 3: Elasto-Plastic Bending and Torsion Chapter 4: Plastic Analysis of Beams and Frames Chapter 5: Further Solutions of Elasto-Plastic Problems Chapter 6: Theory of the Slipline Field Chapter 7: Steady Problems in Plane Strain Chapter 8: Non-Steady Problems in Plane Strain

20,724 citations

Journal ArticleDOI
TL;DR: In this article, a variational principle is established to characterize the flow field in an elastically rigid and incompressible plastic material containing an internal void or voids, and an approximate Rayleigh-Ritz procedure is developed and applied to the enlargement of an isolated spherical void in a nonhardening material.
Abstract: The fracture of ductile solids has frequently been observed to result from the large growth and coalescence of microscopic voids, a process enhanced by the superposition of hydrostatic tensile stresses on a plastic deformation field. The ductile growth of voids is treated here as a problem in continuum plasticity. First, a variational principle is established to characterize the flow field in an elastically rigid and incompressible plastic material containing an internal void or voids, and subjected to a remotely uniform stress and strain rate field. Then an approximate Rayleigh-Ritz procedure is developed and applied to the enlargement of an isolated spherical void in a nonhardening material. Growth is studied in some detail for the case of a remote tensile extension field with superposed hydrostatic stresses. The volume changing contribution to void growth is found to overwhelm the shape changing part when the mean remote normal stress is large, so that growth is essentially spherical. Further, it is found that for any remote strain rate field, the void enlargement rate is amplified over the remote strain rate by a factor rising exponentially with the ratio of mean normal stress to yield stress. Some related results are discussed, including the long cylindrical void considered by F.A. McClintock (1968, J. appl. Mech . 35 , 363), and an approximate relation is given to describe growth of a spherical void in a general remote field. The results suggest a rapidly decreasing fracture ductility with increasing hydrostatic tension.

4,156 citations

Journal ArticleDOI
M.F. Ashby1
TL;DR: The geometrically necessary dislocations as discussed by the authors were introduced to distinguish them from the statistically storages in pure crystals during straining and are responsible for the normal 3-stage hardening.
Abstract: Many two-phase alloys work-harden much faster than do pure single crystals. This is because the two phases are not equally easy to deform. One component (often dispersed as small particles) deforms less than the other, or not at all, so that gradients of deformation form with a wavelength equal to the spacing between the phases or particles. Such alloys are ‘plastically non-homogeneous’, because gradients of plastic deformation are imposed by the microstructure. Dislocations are stored in them to accommodate the deformation gradients, and so allow compatible deformation of the two phases. We call these ‘geometrically-necessary’ dislocations to distinguish them from the ‘statistically-stored’ dislocations which accumulate in pure crystals during straining and are responsible for the normal 3-stage hardening. Polycrystals of pure metals are also plastically non-homogeneous. The density and arrangement of the geometrically-necessary dislocations can be calculated fairly exactly and checked by electr...

3,527 citations

Book
01 Jan 1979
TL;DR: In this article, Bertotti, Ferro, and Mazetti proposed a theory of dislocation drag in covalent crystals and formed a model of the formation and evolution of dislocations during irradiation.
Abstract: Preface. Electrical noise associated with dislocations and plastic flow in metals (G. Bertotti, A. Ferro, F. Fiorillo, P. Mazetti). Mechanisms of dislocation drag (V.I. Alshits, V.L. Indenbom). Dislocations in covalent crystals (H. Alexander). Formation and evolution of dislocation structures during irradiation (B.O. Hall). Dislocation theory of martensitic transformations (G.B. Olsen, M. Cohen). Author index. Subject index. Cumulative index.

2,752 citations