ANOMALOUS INTERNAL FRICTION PEAKS AS FUNCTION OF STRAIN AMPLITUDE

Abstract
Anelasticity, as suggested by Zener /1/ in 1948, gives rise to internal friction which is independent of the strain amplitude. The internal friction which increases with an increase of strain amplitude was explained by Koehler /2/ and Granato and Lücke /3/ in terms of vibration string and unpinning of dislocations. Early in 1949, Kê /4, 5/ observed in slightly cold-worked dilute aluminium-copper solid solutions a pronounced internal friction peak as a function of strain amplitude in which the high-amplitude side of the peak decreases rapidly to reach a very small value. The term "anomalous internal friction" was suggested by Kê /4/ in the sense that this anomalously amplitude-dependent internal friction is quite different from the amplitude independent internal friction formulated by Zener /1/ as well as from the "normal" amplitude dependent effect treated by Granato and Lücke /3/ in which the internal friction increases with an increase of strain amplitude and then decreases slowly and stays at an almost constant high value. This report reviews the experimental results concerning the anomalously amplitude-dependent internal friction peaks since the work of Kê in 1949, with emphasis on cold-worked f.c.c. metals (Al) containing Cu or Mg as substitutional solute atoms. In the light of the latest experimental results, a kink-dragging model is suggested.