Dissipative acoustic nonlinearity of polycrystalline zinc

Results of experimental studies of nonlinear acoustic effects, namely, the attenuation of a weak ultrasonic pulse under the action of an intense low-f requency pumping wave and the limitation of the ultrasonic pulse amplitude in rod-type resonators made of unannealed and annealed polycrystalline zinc , are presented. The measurements are performed for the first four longitud inal modes of the rods with the frequency of them ultrasonic pulses varying from 40 kHz to 1 MHz. An analytical description of this effect is presente d in the framework of the phenomenological equation of state allowing for d issipative nonlinearity. A modification of the Granato-Lucke dislocation th eory that explains the experimentally observed amplitude and frequency depe ndences of the coefficient of nonlinear attenuation of ultrasonic pulses is proposed. Estimates for the parameters of the modified model are obtained from the comparison of theoretical and experimental data. (C) 2001 MAIK "Na uka/Interperiodica".