Dislocations in solids contribute to anelastic attenuation, relaxation of the shear modulus, transient creep, and steady state flow. These properties of the mantle may therefore be related. The glide and climb of dislocations appear to have the appropriate time constants to explain seismic wave attenuation and mantle viscosity, respectively. The dislocation density of the mantle depends on the ...

The melting of a polydisperse hard disk system is investigated by Monte Carlo simulations in the semigrand canonical ensemble. This is done in the context of possible continuous melting by a dislocation unbinding mechanism, as an extension of the 2D hard disk melting problem. We find that while there is pronounced fractionation in polydispersity, the apparent density-polydispersity gap does not...

Ultrasonic attenuation in crystals of ice Ih has been measured as functions of frequency (15 a 85 MHz) and temperature ( 8°C a O.l°C). Data were analyzed on the basis of vibrating string model of dislocation, and the following results have been obtained: Density of dislocations is on the order of 106 cm-*; pinning of dislocations may be due to impurity ions; dislocation density severely fluctua...

Computational design of materials processes has received great interests during the past few decades. Successful designs require accurate assessment of material properties, which can be influenced by the internal microstructure of materials. This work aim to develop a novel computational model based on dislocation structures to predict the flow stress properties of metallic materials. To create...

In this article, some Fe (III) doped hydroxyapatite samples (FeHAp) were prepared using the wet chemical method. The prepared samples were characterized via the use of X-ray diffraction (XRD) and scanning electron microscopy (SEM). Detailed structural analysis were done by Scherrer and Williamson–Hall plot methods to detect the effect of iron on the structure of hydroxyapatite (HAp). XRD patter...

Although nanoscale twinning is an effective means to enhance yield strength and tensile ductility in metals, nanotwinned metals generally fail well below their theoretical strength limit due to heterogeneous dislocation nucleation from boundaries or surface imperfections. Here we show that Au nanowires containing angstrom-scaled twins (0.7 nm in thickness) exhibit tensile strengths up to 3.12 G...

When microscopic and macroscopic specimens of metals are subjected to cyclic loading, the creation, interaction, and accumulation of defects lead to damage, cracking, and failure. Here we demonstrate that when aluminum single crystals of submicrometer dimensions are subjected to low-amplitude cyclic deformation at room temperature, the density of preexisting dislocation lines and loops can be d...

The effect of dose and energy on postannealing defect formation for high energy ~mega-electron-volt! phosphorus implanted silicon has been studied using etch pit studies and transmission electron microscopy ~TEM!. Previous work has shown that after annealing there is a strong dependence of dislocation density threading to the surface on the implanted phosphorus dose and energy. A superlinear in...

The relationship between the film thickness and dislocation spacing in the interface dislocation arrays is studied by using a criterion based on the energy difference between the relaxed film configuration and a selected, partially relaxed or unrelaxed reference configuration. It is shown that arrays with lower dislocation density are formed in relaxation processes that are more gradual. Stabil...