We calculate the effect of the nonsingular stress acting parallel to a crack (the “Tstress”) on edge dislocation nucleation at a crack loaded in Mode I. We find that this leads to crack size effect – that is, for small cracks (of order 100 atomic spacings or less), the T stress causes the critical load for dislocation nucleation (expressed in terms of the applied stress intensity factor) to dev...

The diffusion of an interstitial Si atom along an edge dislocation in Al is studied by using a quantummechanics/molecular-mechanics coupling method. It is found that the diffusing Si atom follows approximately a sinusoidal trajectory. The diffusion energy barrier along the partial dislocation core is in excellent agreement with the experimental value. We predict that the stacking fault ribbon c...

Transmission electron microscopy (TEM) and KOH etching have been used to study the dislocation structure of 4H SiC wafers grown by physical vapor transport. A new type of threading dislocation arrays was observed. Rows of etch pits corresponding to dislocation arrays were observed in vicinity of micropipes, misoriented grains and polytypic inclusions at the periphery of the boules and extended ...

We develop a mesoscopic dislocation dynamics model for vacancy-assisted dislocation climb by upscalings from a stochastic model on the atomistic scale. Our models incorporate microscopic mechanisms of (i) bulk diffusion of vacancies, (ii) vacancy exchange dynamics between bulk and dislocation core, (iii) vacancy pipe diffusion along the dislocation core, and (iv) vacancy attachment-detachment k...

Dislocations are a common type of defects that signifi cantly infl uence many mechanical phenomena such as plastic deformation, crystal growth, morphology, or diffusion of materials. Although dislocations have been well-studied for simple crystalline structures such as pure metals, semiconductors, ionic materials, and binary oxides, there is very limited knowledge on such defects in complex-lay...

We study the dynamic response of a superfluid field to a moving edge dislocation line to which the field is minimally coupled. We use a dissipative Gross-Pitaevskii equation, and determine the initial conditions by solving the equilibrium version of the model. We consider the subsequent time evolution of the field for both glide and climb dislocation motion and analyze the results for a range o...

We consider dislocations in the framework of Eringen’s nonlocal elasticity. The fundamental field equations of nonlocal elasticity are presented. Using these equations, the nonlocal force stresses of a straight screw and a straight edge dislocation are given. By the help of these nonlocal stresses, we are able to calculate the interaction forces between dislocations (Peach-Koehler forces). All ...

Abstract. Various equilibrium dislocation distributions in finite and infinite media were recently analyzed [51 both from theoretical and computational standpoints. In this paper we shed further light on this issue, by elaborating on a variational procedure that gives the required equilibrium conditions: the glide forces on each dislocation represent a set of self-equilibrating forces. The deri...

The Grandjean-Friedel-Cano wedge geometry is used to produce well controlled edge dislocation patterns in ordered latexes. Due to the strain field, the color of the Bragg reflected light is found to be modified, making the dislocations easily visible in a metallurgical microscope. An estimate of the elastic energy stored in this strain field is made. The minimum energy configuration of the disl...

The stress-driven motion of dislocations in crystalline solids, and thus the ensuing plastic deformation process, is greatly influenced by the presence or absence of various pointlike defects such as precipitates or solute atoms. These defects act as obstacles for dislocation motion and hence affect the mechanical properties of the material. Here we combine molecular dynamics studies with three...