The processes of elastic and plastic deformation of materials are considered within the framework of the modified model of the acoustoplastic effect. The conditions of reducing it to the widely used empirical Bodner-Partom model for describing experimental stress-strain curves are analyzed. The conditions of applicability of this empirical model are noted. The relationship between the parameters used in the Bodner-Partom model and such material parameters as the internal friction stress, the activation volume of defects, their relaxation time and their equilibrium concentration, as well as with the parameter characterizing the degree of interaction of defects is determined. Keywords: mechanical stress, plastic strain rate, acoustoplastic effect, defects.