Formation and strength of dislocation junctions in FCC metals: A study by dislocation dynamics and atomistic simulations

The structure and strength of three-dimensional Lomer-Cottrell junctions are studied using four different models. These models represent increasing levels of sophistication, with each case including some new physical effect. The line tension approximation makes use only of the elastic self energy of the dislocation lines. The edge-screw dislocation dynamics model increases the sophistication by including the elastic interactions between all of the dislocation segments. At the next level of sophistication, the nodal dislocation dynamics method accounts for the dissociation of the core into partial dislocations. Finally, the quasicontinuum method takes into account the core effects at the atomic level. The results show that although the line tension model represents a huge simplification of the physics of dislocations, it is able to reproduce the equilibrium structure of any type of Lomer-Cottrell interaction, both in the absence and presence of an externally applied stress. The pseudo-analytical description can thus be used as a bench mark for the development of dislocation dynamics simulations.