An experimental study of an influence of a strong low-frequency wave on the propagation of weak ultrasonic pulses in an acoustic resonator made of annealed polycrystalline copper has been carried out. The measurements were carried out with harmonic excitation of the resonator at its first four longitudinal modes in the range from 2 to 15 kHz, the frequency of ultrasonic pulses varied from 65 to 400 kHz. The analysis of the observed nonlinear effects was carried out within the framework of the polycrystal equation of state obtained on the basis of a modified string model of the Granato-Lucke dislocation. The values of the parameters of dissipative and reactive nonlinearity of dislocations in annealed copper are determined. Keywords: dislocation dissipative and reactive nonlinearity, polycrystalline copper, elastic waves.

A theoretical study of the propagation of longitudinal strong low-frequency and weak high-frequency elastic waves in non-dispersing solids with a bimodular nonlinearity is carried out, taking into account the effects of reflection from the shock fronts of the wave. Expressions are obtained for the waveform, as well as for the amplitudes, frequencies, and phases of the harmonic components of the perturbation reflected from the discontinuities of the nonlinear wave. Numerical and graphical analysis of the obtained solutions is carried out. It is noted that the experimental study of the effects of wave reflection from discontinuities can be used to determine the nonlinear parameter of the bimodular solids. Keywords: longitudinal elastic waves, bimodular nonlinearity, shock waves, reflection from a discontinuity.