SECOND ORDER PYRAMIDAL SLIP IN ZINC SINGLE CRYSTALS K. H. Adams,* R. C. Blish and T. Vreeland, Jr. W. M. Keck Laboratory of Engineering Materials California Institute of Technology Pasadena, California (U.S.A.) CALT-473-18 Measurements of strain, dislocation mobility and dislocation density have been made in 99.999% zinc single crystals stressed at room temperatur~ j_n comp.!:_ession along the ...

Grain boundaries (GBs) play a fundamental role in the strengthening mechanism of crystalline structures by acting as an impediment to dislocation motion. However, the presence of an aggressive environment such as hydrogen increases the susceptibility to intergranular fracture. Further, there is a lack of systematic investigations exploring the role of hydrogen on the dislocation-grain-boundary ...

An exactly solvable phase-field theory of dislocation dynamics, strain hardening and hysteresis in ductile single crystals is developed. The theory accounts for: an arbitrary number and arrangement of dislocation lines over a slip plane; the long-range elastic interactions between dislocation lines; the core structure of the dislocations resulting from a piecewise quadratic Peierls potential; t...

The microstructure of three different nanocrystalline materials with hexagonal crystal structure are studied by X-ray diffraction peak profile analysis. The crystallite size distribution and the dislocation structure are determined in plasmathermal silicon nitride powder, sintered tungsten carbide and severely deformed titanium and are compared with transmission electron microscopy (TEM) result...

Very high strain hardening coefficients (=G/23) are observed for aluminum-alloyed face-centered cubic Hadfield steel single crystals under tensile loading. Alloying with aluminum suppressed deformation twinning in two of the three crystallographic orientations studied, and transmission electron microscopy results revealed the existence of dense dislocation walls (sheets) along crystallographic ...

The normal stress distribution across a slip plane has the effect of reducing the critical loading required for dislocation emission from a crack tip. The reduction by normal stresses was found to be very significant for Si, based on properties estimated for it using density functional theory, to be large for Fe as modeled by the embedded atom method (EAM), and to be smaller in AI, Ni and order...

Open dislocation of the proximal interphalangeal (PIP) joint is relatively rare. We report a case of a 32-year-old man who had open dislocation of the PIP joint of the little finger while playing American football. He had a history of chronic radial collateral ligament injury. We reconstructed the radial collateral ligament with a half-slip of the flexor digitorum superficialis tendon.

Analysis of the tidal stress tensor at the time of moderate to large earthquakes fails to confirm an earlier hypothesis that the origin times of shallow dip-slip earthquakes correlate with solid-earth tidal shear stress, Furthermore, no correlation is seen for either tidal shear stress or tidal normal-to-the-fault compressive stress with shallow strike-slip earthquakes or with deep earthquakes....

Using QM-Sutton-Chen many-body potential, we have studied the 1⁄2a<110> screw dislocation in nickel (Ni) via Molecular Dynamics (MD) simulations. We have studied core energy and structure using a quadrupolar dislocation system with 3-D periodic boundary conditions. The relaxed structures show dissociation into two partials on {111} planes. The equilibrium separation distance between the two par...

Simultaneous dislocation of both the proximal and distal interphalangeal (PIP and DIP) joints in a finger is uncommon. Two patients were treated conservatively. Both two patients fell from a step-ladder and X-rays revealed dorsal dislocations of both PIP and DIP joints of their right little fingers. Manual reduction was easily achieved with gentle longitudinal traction. The mechanism of the inj...