Modulus Change Associated with Amplitude-Dependent Internal Friction in Crystals

Abstract

The ratio of amplitude-dependent internal friction to the associated modulus change is discussed for the case where the both quantities are due to dislocations oscillating in the lattice. It is shown that the ratio lies between π and 4, when the motion of dislocation is limited by frictional forces. The ratio has a smaller value, when the motion is prevented by the obstacles such as subboundaries, or when it is limited by tension forces. Comparison of the above results with available data on copper, copper alloys and lead shows that the experimental values of the ratio can be explained by assuming that the internal friction is due to dislocations oscillating in the lattice, where impurities are randomly distributed.