The peaking effect in the internal friction of metals

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Abstract
Since the discovery by Simpson and Sosin (1972) that under certain experimental conditions the internal friction of metals may attain a maximum during irradiation with electrons or γ-rays before the onset of a steady decline, several attempts have been made to account for the occurrence of the peak. Relaxational models, based on defect-dragging processes, imply a frequency dependence of the peak height which is not observed, while the phenomenological ‘hysteretic’ ones hitherto advanced encompass only some of the main features of the peaking effect. In the present paper a model is outlined in which elastic interactions between stationary point defects and the cores of vibrating dislocations, at which they are adsorbed, lead to an initial increase in the damping. However, as a result of the increasing pinning force acting on the dislocations with rising point-defect concentration, the maximum, attained at a certain level of integrated flux, is followed by a uniform decrease in the internal friction. The frequency independence of the peak height and other principal characteristics of the peaking effect are explained by the model.