The Amplitude Dependence of Internal Friction and the Young's Modulus Defect in Solids Due to Anharmonism of Dislocation Motion at Low Vibration Amplitudes

The amplitude dependence of internal friction and Young's modulus defect in solids are considered under the conditions of athermic surmounting by dislocations of potential barriers associated with the so-called “generalized static friction forces”. It is shown that the anharmonism of constrained oscillations of dislocations gives rise to an amplitude dependence of internal friction and the Young's modulus defect observed in real crystals at relative deformation amplitudes ≈ 10−7 to 10−5 and at frequencies ≈ 105 Hz. The results of a comparison of the theory with experimental data for a number of crystals are given. The characteristic stresses at which the anharmonic behaviour of dislocations occurs are found to be one order smaller than the stresses of break-off of dislocations from minor pinning points.