Low Frequency Internal Friction Due to Dislocations Oscillating in the Lattice

The amplitude-dependent internal friction which is due to dislocations oscillating in the lattice is described in terms of dislocation mobility, under the condition that the motion of dislocation is limited by tension forces, as will be the case at low frequencies. It is shown that the friction increases as the frequency increases and that it decreases as the amplitude increases. These results are in contrast to those obtained before for the internal friction at high frequencies, where the internal friction increases with the amplitude and has an inverse frequency dependence. Comparison with available data of low frequency internal friction on copper and α-brass shows that the line-tension limited motion accounts for the observed results.