Modification of the Koehler-Granato-Lücke Dislocation Damping Theory

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Abstract
The dislocation damping theory of Koehler, Granato, and Lücke is modified for metals with high stacking fault energy. It is assumed that the most abundant impurity atom species interacts only with the edge component of each dislocation. For this model the hysteretic, or frequency independent damping initially increases linearly with stress amplitude and approaches the Granato‐Lücke amplitude dependence at higher stresses. The influence of a second, less abundant impurity atom species which can interact with both screw and edge components also is considered. When the glide distance of a dislocation after breakaway becomes comparable with the mean spacing of the second type of impurity, the hysteretic damping becomes amplitude independent. This modification is best suited for application to the damping of bcc metals containing a higher concentration of substitutional impurities than interstitial impurities.