Dislocation contribution to acoustic nonlinearity: The effect of orientation-dependent line energy

Abstract

Dislocation dynamics (DD) simulations are used to investigate the acoustic nonlinearity created by dislocations in crystals. The acoustic nonlinearity parameter, β, is quantitatively predicted for a single dislocation bowing in its glide plane between pinning points under a quasistatic loading assumption using DD simulations. The existing model using a constant line energy assumption fails to capture the correct behavior of β for edge dislocations in materials with a nonzero Poisson’s ratio. A strong dependence of β on the orientation of Burgers vector relative to the line direction of the dislocation is shown by the DD simulations. A new model using an orientation-dependent line energy is derived for the cases of initially pure edge and screw dislocations. The model is shown to agree with the DD simulations over a range of Poisson’s ratio and static stresses.