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The results of integrated studies of the slow relaxation of the sound speed in structurally inhomogeneous materials after vibratory action with a finite strain amplitude are presented. The results were obtained using an experimental setup created for these studies, which ensured highly accurate measurements of the linear and nonlinear acoustic characteristics of various materials. The results of an experimental study of relaxation in carbonate rock, which is a structurally inhomogeneous material with a complex system of internal relationships, are presented. The measurements made it possible to determine the dependence of the relaxation parameters on the amplitude and time of excitation, as well as the effects caused by the finite amplitude of the probing wave. The results are interpreted, and effects that have not received an exhaustive explanation are noted. [ABSTRACT FROM AUTHOR]

The paper presents the results of experimental research into the nonlinear acoustic properties of carbonate rocks depending on saturation. The linear acoustic properties of the same sample depending on saturation were presented earlier in Physical Acoustics. The previously obtained data point to the isotropy of the material, which makes it possible to restrict analysis to only two vibration modes. Responses for finite deformations were measured for the longitudinal and shear modes of an isotropic sample, which made it possible to analyze the nonlinear properties of macroscopic deformations with a change in volume and pure displacement. A heretofore unknown feature of the response was revealed for finite deformation values; it is related to the occurrence of a jumplike transition from classical nonlinearity to a hysteresis type of nonlinearity. As well, the deformation amplitude corresponding to the transition depends on fluid saturation. We studied the slow relaxation that occurs after long-term excitation of a sample with a deformation amplitude on the order of 10. Data are presented on relaxation for deformation from pure displacement and deformation with a change in volume, which made it possible to isolate features related to the type of deformation and to compare the obtained data with the earlier published theoretical model. These data are compared with the results of other research groups. [ABSTRACT FROM AUTHOR]

The results of acoustic spectroscopy of a carbonate sedimentary rock in the case of saturation degree variations are given. The data on the elasticity and dissipation tensors within a two-octave range are obtained for one and the same sample using one and the same measurement technique. High accuracy of the measurements allowed distinguishing all three saturation stages, namely, condensation, meniscus creation, and pore filling with a fluid. The observed variations are in good agreement with the results of a standard granulometric analysis. The character of variations in the frequency dependence of attenuation coefficients make it possible to make reasonable assumption concerning the mechanisms responsible for acoustic energy absorption in porous materials. [ABSTRACT FROM AUTHOR]