Investigation into the seismoacoustic properties of specific polycrystalline materials used in nuclear reactors
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he 100th anniversary of the discovery of Xray diffraction
Investigation into the Seismoacoustic Properties of Specific Polycrystalline Materials Used in Nuclear Reactors A. N. Nikitin†a, R. N. Vasina, T. I. Ivankinaa, A. A. Kruglova, T. Lokajicekb, and L. T. N. Phanc a
Joint Institute for Nuclear Research, ul. JoliotCurie 6, Dubna, Moscow oblast, 141980 Russia email: [email protected] b Institute of Geology, Academy of Sciences of the Czech Republic, Rozvojova 269, 165 00 Praha 6Lysolaje, Czech Republic c Tula State University, pr. Lenina 92, Tula, 300600 Russia Received March 23, 2012
Abstract—The characteristics of the wave fields observed during the transmission of quasilongitudinal ultra sonic 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 prop agation times of quasilongitudinal 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. DOI: 10.1134/S1063774512050100
INTRODUCTION The complex character of elasticwave propagation at reflection and refraction from interfaces between isotropic and inhomogeneous media has been noted in the literature on acoustics [1] and seismology [2]. The modern development of seismology has made it neces sary to take into account the anisotropy of elastic properties of geological media [3–5]. Based on an original analytical approach, it was confirmed [6–8] that elastic waves passing through interfaces in aniso tropic media undergo the ternary (in the general case) splitting of reflected and refracted waves at certain grazing angles. This property of acoustic waves was discussed in [9]. However, no experiments on the observation of the splitting of elastic waves propagating through inter faces between different rocks have been performed, and these effects have not been observed at contacts between many structural materials. In this context, an urgent problem is to perform test experiments (based on results obtained by different calculation tech niques) on model samples of materials with well known properties in order to estimate the conditions under which this effect can be detected at elasticwave transmission through an interface between two media. In the first stage, experiments were conducted on sam ples composed of acrylic glass and singlecrystal quartz [10]. Then this experimental study was contin ued on a model assembly composed of polycrystalline graphite (
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