Journal ArticleDOI
Dislocation nucleation from a crack tip : an analysis based on the Peierls concept
Reads0
Chats0
TLDR
In this paper, a periodic relation between shear stress and atomic shear displacement is assumed to hold along the most highly stressed slip plane emanating from a crack tip, which allows some small slip displacement to occur near the tip in response to small applied loading and, with increase in loading, the incipient dislocation configuration becomes unstable and leads to a fully formed dislocation which is driven away from the crack.Abstract:
Dislocation nucleation from a stressed crack tip is analyzed based on the Peierls concept. A periodic relation between shear stress and atomic shear displacement is assumed to hold along the most highly stressed slip plane emanating from a crack tip. This allows some small slip displacement to occur near the tip in response to small applied loading and, with increase in loading, the incipient dislocation configuration becomes unstable and leads to a fully formed dislocation which is driven away from the crack. An exact solution for the loading at that nucleation instability is developed via the J -integral for the case when the crack and slip planes coincide, and an approximate solution is given when they do not. Solutions are also given for emission of dissociated dislocations, especially partial dislocation pairs in fcc crystals. The level of applied stress intensity factors required for dislocation nucleation is shown to be proportional to √γ us , where γ us , the unstable stacking energy, is a new solid state parameter identified by the analysis. It is the maximum energy encountered in the block-like sliding along a slip plane, in the Burgers vector direction, of one half of a crystal relative to the other. Approximate estimates of γ us are summarized and the results are used to evaluate brittle vs ductile response in fcc and bcc metals in terms of the competition between dislocation nucleation and Griffith cleavage at a crack tip. The predictions seem compatible with known behavior and also show that in many cases solids which are predicted to first cleave under pure mode I loading should instead first emit dislocations when that loading includes very small amounts of mode II and III shear. The analysis in this paper also reveals a feature of the near-tip slip distribution corresponding to the saddle point energy configuration for cracks that are loaded below the nucleation threshold, as is of interest for thermal activation.read more
Citations
More filters
Journal ArticleDOI
Stress singularities along a cycloid rough surface
Chiu Cheng-Hsin,Gao Huajian +1 more
TL;DR: In this article, a cycloid wavy surface subject to a uniform bulk stress is adopted as a model problem, and the elastic stress and displacement fields are determined using Muskhelishvili's conformal mapping method.
Journal ArticleDOI
Molecular dynamics simulations of shock compression of nickel: From monocrystals to nanocrystals
H. Jarmakani,Eduardo M. Bringa,Paul Erhart,Bruce Remington,Yinmin Wang,Nhon Q. Vo,Marc A. Meyers +6 more
TL;DR: In this paper, the effect of stress unloading, a phenomenon often neglected in MD simulations, on dislocation behavior is computed, and it is shown that a large fraction of the dislocations generated during compression is annihilated upon unloading.
Journal ArticleDOI
Solid solution strengthening of hexagonal titanium alloys: Restoring forces and stacking faults calculated from first principles
TL;DR: In this article, a series of Ti+X alloys (X = Al, Sn, V, Zr and O) were selected to analyze the impact of solute valence structure and lattice site deformation on the mechanisms responsible for variation of mechanical properties.
Journal ArticleDOI
Kinetic Pathways to Strain Relaxation in the Si-Ge System.
TL;DR: In this paper, the authors adopt a nucleation and growth description of the 2D-to-3D transition in Si-Ge system to understand the kinetic pathways to island formation.
Journal ArticleDOI
Atomistic simulation of the deformation of gold nanopillars
TL;DR: In this paper, a series of molecular dynamics simulations of the uniaxial compression of cylindrical gold nanopillars is performed, and the authors suggest that dislocation nucleation at the surface of the nanopillar occurs at a critical strain, where the local strain has contributions from the homogeneous elastic strain and an atomic level thermal strain.
References
More filters
Book
Theory of Dislocations
John Price Hirth,Jens Lothe +1 more
TL;DR: Dislocations in Isotropic Continua: Effects of Crystal Structure on Dislocations and Dislocation-Point-Defect Interactions at Finite temperatures.
Journal ArticleDOI
A Path Independent Integral and the Approximate Analysis of Strain Concentration by Notches and Cracks
TL;DR: In this paper, an integral is exhibited which has the same value for all paths surrounding a class of notches in two-dimensional deformation fields of linear or non-linear elastic materials.
Journal ArticleDOI
Embedded-atom method: Derivation and application to impurities, surfaces, and other defects in metals
Murray S. Daw,Michael I. Baskes +1 more
TL;DR: In this paper, the authors derived an expression for the total energy of a metal using the embedding energy from which they obtained several ground-state properties, such as the lattice constant, elastic constants, sublimation energy, and vacancy-formation energy.
Journal ArticleDOI
Embedded-atom-method functions for the fcc metals Cu, Ag, Au, Ni, Pd, Pt, and their alloys.
TL;DR: A consistent set of embedding functions and pair interactions for use with the embedded-atom method was determined empirically by fitting to the sublimation energy, equilibrium lattice constant, elastic constants, and vacancy-formation energies of the pure metals and the heats of solution of the binary alloys as discussed by the authors.
High-temperature ordered intermetallic alloys
TL;DR: In this article, the authors describe the behavior of grain boundaries in a two-dimensional model ordered alloy and the effects of elastic anisotropy on the anomalious yield behavior of cubic ordered alloys.