Dislocation Emission and Crack Dislocation Interactions

Atomistic study of dislocation loop emission from a crack tip.

We report the first atomistic calculation of the saddle-point configuration and activation energy for the nucleation of a 3D dislocation loop from a stressed crack tip in single crystal Cu. The transition state is found using reaction pathway sampling schemes, the nudged elastic band, and dimer methods. For the (111)[110] crack, loaded typically at 75% of the athermal critical strain energy rel...

Hydrogen-dislocation Interactions and Intrinsic Dislocation Relaxation in Niobium

The dislocation relaxation between 100 K and 200 K (IkHz) in plastically deformed niobium, formerly named "a-relaxation" is a hydrogen Snoek-Koster relaxation (cold work relaxation). This is shown by experiments on extremely degassed samples, which contained controlled amounts of hydrogen and/or oxygen. The intrinsic, hydrogen-free dislocation relaxation appears between 30 K and 70 K (IkHz), th...

Crack Tip Dislocation Nucleation in FCC Solids

We present results of molecular dynamic simulations aimed at examining crack tip dislocation emission in fcc solids. The results are analyzed in terms of recent continuum formulations of this problem. In mode II, Au, Pd, and Pt displayed a new unanticipated mechanism of crack tip dislocation emission involving the creation of a pair of Shockley partials on a slip plane one plane below the crack...

Finite-temperature dislocation interactions

Void growth by dislocation emission

Laser shock experiments conducted at an energy density of 61 MJ/m revealed void initiation and growth at stress application times of approximately 10 ns. It is shown that void growth cannot be accomplished by vacancy diffusion under these conditions, even taking into account shock heating. An alternative, dislocation-emission-based mechanism, is proposed for void growth. The shear stresses are ...