Internal Friction of Lead, II

概要

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The experimental results on the internal friction of lead single crystals were discussed on the basis of the dislocation theory. At low temperatures, the dependences of the internal friction on the strain amplitude and the frequency are well explained with the pinned-down dislocation model. The pinning of dislocations by point defects is also varified to exist through analyzing the change of the amplitude dependence of the internal friction produced by annealing the specimen. The exponential increase of the internal friction with increasing temperature is considered to be due to the thermal break-away of the dislocations from the pinning points. On the assumption that the Cottrell's force acts between the pinning impurity atom and the dislocation, some of the unknown quantities of a crystal can be determined as follows: dislocation density is 1.03 × 10^8cm^<-3>, loop length of dislocation network 1.71 × 10^<-4>cm, and mean distance between impurities on dislocation 2.85 × 10^<-5>cm. Above a certain temperature (about 300°K) the internal friction decreases with increasing strain amplitude, being the reverse of the behavior at low temperatures. This phenomenon is interpreted as the impurity pinning becomes ineffective at high temperatures and the formation of jogs at the network pinning points of the dislocations contributes to the internal friction.
社団法人日本物理学会の論文
1959-05-05