The frequency dependence of sound radiation from mobile dislocation walls

Abstract

Macroscopic re-radiated plane waves from microscopic dislocation sources oscillating in a narrow slip band have been produced and detected in LiF and NaCl crystals in the 5–110 MHz frequency range. The observed waves were shown to depend upon the dislocation motion through their dependence on the orientation of the exciting waves and their dependence on the number of pinning points on the dislocation lines during γ-irradiation of LiF and NaCl. The quantitative values of the re-radiated wave amplitudes were shown to be in good agreement with the values given by the model of the vibrating string for the dislocation displacements, both in the low frequency or frequency independent region and in the high frequency or ω −1 frequency region of the displacement. Since the measured re-radiated amplitudes were as large as is permitted by the vibrating string model, dislocation-dislocation interactions could not play an important role in limiting the dislocation motion for this configuration of dislocations.