T. I. Ivankina

P-wave ray velocities and the inverse acoustic problem for anisotropic media

The specific features of the calculation of ray velocities of quasi-longitudinal waves in anisotropic media have been considered. A technique for calculating elastic constants using P-wave ray velocities measured in an ultrasonic experiment on spherical samples is presented. It is shown by an example of tabular data that elastic constants С11, С22, and С33 and combinations of constants (С12 + 2С66), (С13 + 2С55), (С23 + 2С44), (С14 + 2С56), (С25 + 2С46), and (С36 + 2С45) can be calculated most accurately for the general case of anisotropic media with elastic properties of arbitrary symmetry. Since the determining system of equations is illconditioned, the values of elastic constants entering these combinations depend on the choosed initial approximation.

Peculiarities of quasi-longitudinal elastic wave propagation through the interface between isotropic and anisotropic media: Theoretical and experimental study

The peculiarities of elastic wave propagation in a bilayer medium are studied theoretically and experimentally. One (isotropic) layer was an acrylic glass plate, and the other (anisotropic) was a quartz single-crystal. In experiments, the elastic waves were generated by a piezoelectric transmitter and received by a piezoelectric transducer contacting the surface of the model medium. The propagation time of a quasi-longitudinal wave was determined using high-order statistics. In the general case, the incident elastic waves are split at the interface between the layers: beams undergo double reflection and triple refraction. The measured dependences of the propagation times of quasi-longitudinal split waves on the angles of refraction are in satisfactory agreement with the calculated ones. The calculation was performed by solving the Christoffel equation with allowance for the boundary conditions.

Similar Quartz Crystallographic Textures in Rocks of Continental Earth's Crust (by Neutron Diffraction Data): III. Relation of Quartz Texture Types with Means and Conditions of Texture Formation

Examples of different rocks collected in different regions of the continental earth’s crust are presented. Groups of quartz crystallographic textures of the same type are selected for these rocks. The relationship between the types of textures and the physical means and conditions of their formation is analyzed. The effect of the α-β phase transition in quartz on the texture transformations in rocks is considered.

Investigation into the seismoacoustic properties of specific polycrystalline materials used in nuclear reactors

The characteristics of the wave fields observed during the transmission of quasi-longitudinal ultrasonic waves through polycrystalline graphite samples have been studied. The specific features of propagation of elastic waves in a bilayer medium, where one of the layers (isotropic) is an acrylic glass hemisphere and the other (anisotropic) is a polycrystalline porous graphite hemisphere, are considered. The velocities and propagation times of quasi-longitudinal waves in polycrystalline graphite samples and a bilayer acrylic glass-graphite sample in different directions are experimentally measured by ultrasonic spatial sounding. The experimental results are compared with theoretical calculations using the data on graphite crystallographic texture obtained previously by neutron diffraction. The reasons for the discrepancy between the theoretical and experimental characteristics of elastic waves in the media under study are established and analyzed.