Thermally Assisted Unpinning of a Dislocation Double Loop

The effect of thermal fluctuations on dislocation unpinning is computed for a model case of a crystal containing dislocation double loops. The amplitude-dependent decrement as a function of strain amplitude, temperature, and frequency is found to have a maximum. The form of the resulting theory is the same as that for the zero-temperature theory, except that the mechanical breakaway stress of the zero-point theory has to be replaced by a temperature- and frequency-dependent thermal breakaway stress at finite temperatures.