PEAKING EFFECT, EXPERIMENTS AND THEORY

Abstract
Recent observations on the peaking effect in Cu are reported which mainly show that 1) the peaking is independent of frequency in the range 2.10² to 5.10⁴ Hz, 2) the peak height is a function of the initial internal friction background which allows a quantitative description of the amplitude dependence, 3) no diffusion mechanism is involved in the initial increase of internal friction, 4) the peaking effect is present in single crystals. Early findings concerning the dependence of peaking with the total number of defects created in the lattice and the inverse relation between peak time and pinning rate are confirmed. All these features are correctly described by a phenomenological model developed by using lattice dynamics calculations, i .e. a dislocation moves against a constant force independent of velocity, instead of the elastical string like behaviour.